BR102022007300A2 - PROCESS FOR THE ENERGY-EFFICIENT PRODUCTION OF ALKALI METAL ALCOXIDES - Google Patents

Abstract

The present invention relates to a process for the production of sodium and/or potassium alkoxides in countercurrent by reactive rectification. The alcohol reacts in countercurrent with the respective alkali metal hydroxide. The vapors comprising alcohol and water are separated in at least two rectification columns arranged in series. The steam energy obtained in the second rectification is used to operate the first rectification. This specific energy integration, together with the establishment of a certain pressure difference in the two stages of rectification, makes it possible to cover a particularly large proportion of the energy required for rectification via heating steam and to minimize the use of electricity.

Description

PROCESS FOR THE ENERGY-EFFICIENT PRODUCTION OF ALKALI METAL ALCOXIDES

[001] The present invention relates to a process for the production of sodium and/or potassium alkoxides in countercurrent by reactive rectification. The alcohol reacts in countercurrent with the respective alkali metal hydroxide. The vapors comprising alcohol and water are separated in at least two rectification columns arranged in series. The steam energy obtained in the second rectification is used to operate the first rectification. This specific energy integration, together with the establishment of a certain pressure difference in the two rectification stages, makes it possible to cover a particularly large part of the energy required for the rectification by means of the heating steam.

1. Background of the invention

[002] The production of alkali metal alkoxides is an important industrial process.

[003] Alkali metal alkoxides are used as strong bases in the synthesis of various chemicals, for example, in the production of pharmaceutical or agrochemical active ingredients. Alkali metal alkoxides are also used as catalysts in transesterification and amidation reactions.

[004] Alkali metal alkoxides (ROM) are produced by reactive distillation of alkali metal hydroxides (MOH) and alcohols (ROH) in a countercurrent distillation column, in which the reaction water formed according to the following reaction <1> is removed with the distillate.

[005] Such a process principle by which an aqueous solution of alkali metal hydroxide and gaseous methanol are run countercurrently in a rectifying column is disclosed, for example, in US 2,877,274 A. This process is again described in generally unchanged form in WO 01/42178 A1.

[006] Similar processes, which additionally employ a dragging agent such as, for example, benzene, are described in GB 377,631 A and US 1,910,331 A. This dragging agent is used to separate water and alcohol soluble in water. In both patents the condensate is subjected to phase separation to separate the water of reaction.

[007] Correspondingly, DE 96 89 03 C describes a process for the continuous production of alkali metal alkoxides in a reaction column, in which the water-alcohol mixture withdrawn at the top of the column is condensed and then subjected to phase separation. The aqueous phase is discarded and the alcoholic phase is returned to the top of the column along with the fresh alcohol. EP 0 299 577 A2 describes a similar process, in which the water in the condensate is separated with the help of a membrane.

[008] The most industrially important alkali metal alkoxides are those of sodium and potassium, especially the methoxides and ethoxides. Their synthesis is often described in the prior art, for example in EP 1 997 794 A1.

[009] The syntheses of alkali metal alkoxides by reactive rectification described in the prior art typically originate vapors comprising the alcohol and water employed. It is advantageous for economic reasons to reuse the alcohol contained in the vapors as a reagent in reactive distillation. The vapors are therefore typically supplied to a rectification column and the alcohol present therein is separated (described, for example, in GB 737 453 A and US 4,566,947 A). The alcohol thus recovered is then supplied to reactive distillation as a reagent, for example. Alternatively or additionally, a portion of the alcohol vapor can be used to heat the rectification column (described in WO 2010/097318 A1). However, this requires the steam to be compressed to reach the required temperature level for heating the rectifying column. The steam is cooled between the compression stages, where a multi-stage compression is thermodynamically advantageous and an intercooling ensures that the maximum permissible temperature of the compressor is not exceeded.

[0010] The integration of heat within the grinding stage for efficient utilization of the energy employed is described in a different context in Ott, J., Gronemann, V., Pontzen, F., Fiedler, E., Grossmann, G., Kersebohm, D.B., Weiss, G. and Witte, C. (2012). Methanol. in Ullmann's Encyclopedia of Industrial Chemistry, (Ed.). (doi:10.1002/14356007.a16_465.pub3). Paragraph 5.4 of that citation discloses the processing of crude methanol obtained in conventional synthesis processes by rectification using a plurality of rectification columns. It is generally proposed to use the heat of condensation of the steam obtained in the rectification column at relatively high pressure to heat the rectification column at relatively low pressure. However, this citation does not reveal anything about advantageous energy integration in the separation of methanol-water vapors produced in the reactive rectification of alkali metal alkoxides.

[0011] In the production of alkali metal alkoxides, it is desirable to cover the largest possible proportion of the energy required for operation from low energy energy sources, such as steam heating, rather than resorting to higher energy sources, such as like electric current. This requirement is achieved on an industrial scale specifically in integrated plants (chemical parks, technology parks) in which heating steam is generated and remains unused.

[0012] It is therefore the object of the present invention to provide an improved process for the production of sodium and potassium alkoxides by reactive distillation. Said process must allow especially energetically efficient use of the heat released during the compression and cooling of the vapours. It should also cover as much of the energy demand as possible through steam heating as an external energy source and have the lowest possible electricity demand.

2. Brief summary of the invention

[0013] The present invention therefore relates to a process for producing at least one alkali metal alkoxide of the formula MAOR, in which R is a C1 to C6 hydrocarbon radical, preferably methyl or ethyl, and in which MA is selected from sodium, potassium and where MA is preferably sodium, wherein: (a1) a reagent stream SAE1 comprising ROH reacts with a reagent stream SAE2 comprising MAOH in countercurrent at a pressure p3A and a temperature T3A on a column of RRA reactive rectification to provide an RPA crude product comprising MAOR, water, ROH, MAOH, wherein a SAP bottoms product stream comprising ROH and MAOR is withdrawn at the lower end of RRA and a SAB vapor stream comprising water and ROH is withdrawn at the top end of RRA, (a2) and optionally, simultaneously and spatially separated from step (a1), a reagent stream SBE1 comprising ROH reacts with a reagent stream SBE2 comprising MBOH in countercurrent at a pressure p3B and a temperature T3B at an RRB reactive rectification column to generate a RPB crude product comprising MBOR, water, ROH, MBOH, where MB is selected from sodium, potassium and where MB is preferably potassium, where an SBP bottoms product stream comprising ROH and MBOR is withdrawn at the bottom end of RRB and a steam stream SBB comprising water and ROH is drawn at the top end of RRB, (b) the steam stream SAB and if step (a2) is carried out, the steam stream SBB in mixture with SAB or separately from SAB is passed to a first rectification column RD1 to obtain a GRD1 mixture comprising water and ROH in the first rectification column RD1, (c) the GRD1 mixture is in the first rectification column RD1 at a pressure p1 and a temperature T1 separated into a steam stream comprising ROH, SRDB1, at the top end of RD1 and a bottom stream SRDX1 comprising water and ROH at the bottom end of RD1, (d) bottom stream SRDX1 is total or partially passed to a second rectification column RD2, to obtain a GRD2 mixture comprising water and ROH in the second rectification column RD2, (e) the GRD2 mixture is at a pressure p2 and a temperature T2 separated into a steam stream comprising ROH, SRDB2, at the top of RD2 and a bottom stream SRDS2 comprising water and optionally ROH at the lower end of RD2, characterized by the fact that p2 > p1, p2 > p3A and in cases where step (a2) is performed p2 > p3B , and wherein preferably additionally p3A > p1 and in cases where step (a2) is carried out, furthermore preferably also p3B > p1, and wherein (f) energy from SRDB2 is transferred to the GRD1 mixture in the first rectification column RD1.

3. Figures 3.1 Figure 1

[0014] Figure 1 shows a process not according to the invention for the production of alkali metal alkoxides with a corresponding interconnection of rectification columns. One reactive rectification column (“reactive rectification column” is abbreviated to “reaction column”) RRA <3A> at pressure p3A and two rectification columns RD1 <1> and RD2 <2> at pressures p1 and p2 are employed. respectively. In that document, p1 > p3A > p2.

[0015] In RRA <3A> NaOH (stream SAE2 <3A02>) reacts with methanol (stream SAE1 <3A01>) to provide a crude product RPA <3A07> comprising water, methanol, NaOH and sodium methoxide. At the lower end of the RRA <3A> a mixture of methanol-sodium methoxide SAP <3A04> is withdrawn. The bottom evaporator VS3A <3A06> at the lower end of the RRA reaction column <3A> is used to adjust the concentration of the methoxide solution to the desired value in the resulting SAP* mixture <3A08>. In addition, another evaporator can be attached to the bottom of the RRA <3A> reaction column, especially for starting the RRA <3A> reaction column (not shown).

[0016] On top of the RRA <3A> a methanol-water mixture is drawn off as a stream of steam SAB <3A03>. SAB <3A03> is supplied to the first water/methanol column RD1 <1>, where optionally SAB <3A03> is on top of the reaction column RRA <3A> partially condensed in the KRRA condenser <3A05> and recycled in liquid form as reflux to the top of the RRA <3A>. At least a portion of the SAB <3A03> steam is then passed through a VD31 <10> compressor, thereby increasing the pressure of the SAB <3A03> steam from p3A to pressure p1.

[0017] A methanol/water mixture GRD1 <108> is thus obtained in the first rectification column RD1 <1>. The methanol is recovered by distillation as SRDB1 <101> steam in this first RD1 <1> water/methanol column. Methanol recovered as SRDB1 vapor stream <101> is at withdrawal point <109> on top of RD1 <1> discharged and partially on top of rectification column RD1 <1> condensed in condenser KRD1 <102> and recycled into form liquid as reflux to the top of RD1 <1>. The remaining portion of the methanol recovered as vapor SRDB1 <101> is, for example, through a choke D13 <11> decompressed to pressure p3 and introduced into RRA <3A> as methanol stream SAE1 <3A01>.

[0018] At the lower end (another term for “lower end of a rectification column” is “bottom of a rectification column”) of RD1 <1> a bottom stream SRDX1 <103> comprising water and methanol is discharged at point of withdrawal <110>. A first SRDX1 portion <104> of the SRDX1 stream <103> is supplied to a second water/methanol column RD2 <2>, a second SRDX12 portion <105> of the SRDX1 stream <103> is fed through a recycled bottom evaporator to VSRD1 <106> on RD1 <1>. The SRDX1 <104> is, for example, decompressed through a D12 <12> choke to pressure p2 before being introduced into the RD2 <2>.

[0019] A methanol/water mixture GRD2 <206> is thus obtained in the second rectification column RD2 <2>. In the RD2 rectification column <2> the methanol residues of SRDX1 <104> are separated from the water and distilled back as steam stream SRDB2 <201> on top of RD2 <2>. Methanol recovered as vapor stream SRDB2 <201> is at withdrawal point <208> on top of RD2 <2> discharged and partially on top of rectification column RD2 <2> condensed in condenser KRD2 <203> and recycled to form liquid as reflux to the top of RD2 <2>. The remaining portion of the methanol recovered as vapor SRDB2 <201> is passed through a compressor VD23 <13>, thus compressed to pressure p3 and, together with the vapors SRDB1 <101> from RD1 <1> decompressed to pressure p3, introduced as SAE1 methanol stream <3A01> in RRA <3A>.

[0020] At the lower end of RD2 <2> an SRDS2 bottom stream <202> comprising water and optionally methanol is discharged at withdrawal point <207>. SRDS2 <202> is heated through a VSRD2 <204> bottom evaporator and recycled into RD2 <2>.

[0021] For heating the portion of the background current SRDS2 <202> that is recycled by VSRD2 <204> into RD2 <2> the energy released in the condensation of SRDB1 <101> on capacitor KRD1 <102> at the top of the rectification a RD1 column <1> is used. Said energy is supplied to VSRD2 <204>, as indicated by the dashed arrow <4>. Heat transfer can be done indirectly, i.e. using a heat transfer medium other than SRDB1 <101> and SRDS2 <202>, or directly, i.e. through contact of SRDB1 <101> with SRDS2 <202 > on condenser KRD1 <102> or bottom evaporator VSRD2 <204>. In the case of direct contact, it is sufficient to use only the KRD1 condenser <102> and omit the VSRD2 bottom evaporator <204> or to use only the VSRD2 bottom evaporator <204> and to omit the KRD1 condenser <102>, and then in each case pass both streams SRDB1 <101> with SRDS2 <202> through condenser KRD1 <102> or bottom evaporator VSRD2 <204> so that energy, preferably heat, is transferred from SRDB1 <101> to SRDS2 <202> .

3.2 Figure 2

[0022] Figure 2 shows another process not according to the invention for the production of alkali metal alkoxides. This differs from the process shown in figure 1 in terms of the pressures in the respective column. In the embodiment shown in figure 1 p1 > p3A > p2 while in the embodiment shown in figure 2 p1 > p2 > p3A. This different pressure regime makes the VD23 <13> compressor unnecessary and a D23 <14> choke, for example, is attached. Choke D23 <14> decompresses the steam stream SRDB2 <201> from p2 to pressure p3A while in the mode according to figure 1 compressor VD23 <13> increases from p2 to pressure p3A.

3.3 Figure 3

[0023] Figure 3 shows an embodiment of the process according to the invention for the production of alkali metal alkoxides with a corresponding interconnection of rectification and reactive rectification columns. In this document, similarly to the modalities described in figures 1 and 2, a reactive rectification column RRA <3A> at pressure p3A and two rectification columns RD1 <1> and RD2 <2> with pressures p1 and p2 are employed. respectively. In that document, p2 > p1 > p3A. The configuration shown in figure 3 corresponds to the configuration shown in figure 2 with the following exceptions: 1. An intermediate evaporator VZRD1 <107> is arranged in the rectification column RD1 <1> next to the bottom evaporator VSRD1 <106> which can be used to power the GRD1 <108> mixture in RD1 <1>. For this purpose, the GRD1 mixture <108> is at a withdrawal point <111> discharged from the RD1 rectification column <1> as stream SRDX1 <112>. SRDX1 <112> is heated in VZRD1 <107> and recycled in the RD1 rectification column <1>.

[0024] 2. The throttle D12 <12> is due to the different pressures in the rectifying columns RD1 <1> and RD2 <2> (p2 > p1) replaced by a pump P <15>. The reason for this difference is that the pressure of SRDX1 <104>, when this current is passed to RD2<2>, is according to the invention increased to p2.

[0025] 3. In an optional embodiment additional methanol as stream SXE1 <205> is through reflux in the rectification column RD2 <2> added thereto.

[0026] 4. The energy released in the condensation of steam SRDB2 <201> at the top of RD2 <2> is through the intermediate evaporator VZRD1 <107> transferred to SRDX1 <112> and after the reintroduction of SRDX1 <112> into RD1 < 1>, transferred from SRDX1 <112> to the GRD1 <108> mixture present in RD1 <1>. Alternatively or additionally, the energy released in the condensation of steam SRDB2 <201> on top of RD2 <2> is through the bottom evaporator VSRD1 <106> transferred to the SRDX12 <105> portion of the SRDX1 stream <103>. Once SRDX12 <105> is recycled into RD1 <1>, it transfers energy to the GRD1 <108> mixture present in RD1 <1>. The energy flow is shown by the dashed arrow <4>.

[0027] In the case of direct contact, it is sufficient to use only the KRD2 condenser <203> and omit the VSRD1 bottom evaporator <106> or to use only the VSRD1 bottom evaporator <106> and omit the KRD2 condenser <203>, and then in each case pass both streams SRDB2 <201> with SRDX12 <105> through condenser KRD2 <203> or bottom evaporator VSRD1 <106> so that energy, preferably heat, is transferred from SRDB2 <201> to SRDX12 <105>.

3.4 Figure 4

[0028] Figure 4 shows another embodiment of the process according to the invention for the production of alkali metal alkoxides with a corresponding interconnection of rectification columns. In this document, in a similar way to the modalities described in figures 1 and 2, a reactive rectification column RRA <3A> at a pressure p3A and two rectification columns RD1 <1> and RD2 <2> having the pressures of p1 and p2 respectively. In that document, p2 > p3A > p1. The configuration shown in figure 4 corresponds to the configuration shown in figure 3 with the exception of pressure p3A > p1. This allows the VD31 compressor <10> to be omitted while the D13 choke <11> is replaced with the VD13 compressor <16>.

3.5 Figure 5

[0029] Figure 5 shows another embodiment of the process according to the invention. Said modality employs two reactive rectification columns (RRA <3A> at a pressure p3A and RRB <3B> at a pressure p3B) and two rectification columns (RD1 <1> and RD2 <2> having pressures p1 and p2 respectively ). Here p2 > p1 > p3A and p1 > p3B.

[0030] In RRA <3A> NaOH (stream SAE2 <3A02>) is reacted with methanol (stream SAE1 <3A01>) to provide a crude product RPA <3A07> comprising water, methanol, NaOH and sodium methoxide.

[0031] At the lower end of RRA <3A> a mixture of methanol-sodium methoxide SAP <3A04> is withdrawn. The bottom evaporator VS3A <3A06> at the bottom of the RRA column <3A> is used to adjust the concentration of the methoxide solution to the desired value in the resulting SAP* mixture <3A08>. In addition, another evaporator can be attached to the bottom of the RRA <3A> column, especially for starting the RRA <3A> column (not shown).

[0032] On top of RRA <3A> a methanol-water mixture is drawn off as vapor SAB <3A03>. SAB <3A03> is supplied to the first water/methanol column RD1 <1>, where optionally SAB <3A03> is on top of the reaction column RRA <3A> partially condensed in the KRRA condenser <3A05> and recycled in liquid form as reflux to the top of RRA <3A>.

[0033] Simultaneously with the reaction in RRA <3A>, in RRB <3B> KOH (current SBE2 <3B02>) is reacted with methanol [0033] Simultaneously with the reaction in RRA <3A>, in RRB <3B> KOH ( current SBE2 <3B02>) is reacted with methanol

[0034] At the lower end of the RRB <3B> a mixture of methanol-potassium methoxide SBP <3B04> is withdrawn. The VS3B <3B06> bottom evaporator at the lower end of the RRB <3B> column is used to adjust the concentration of the methoxide solution to the desired value in the resulting SBP* <3B08> mixture. In addition, another evaporator can be attached to the lower end of the RRB <3B> column, especially for starting the RRB <3B> reaction column (not shown).

[0035] On top of RRB <3B> a methanol-water mixture is removed as vapor SBB <3B03>, where optionally SBB <3B03> is on top of reaction column RRB <3B> partially condensed in condenser KRRB <3B05 > and recycled in liquid form as reflux to the top of RRB <3B>.

[0036] At least a portion of the SAB <3A03> and SBB <3B03> vapors is combined and the combined vapor is then passed through a VD31 compressor <10> which increases the pressure of the combined vapors to pressure p1. The combined vapors are then passed to the first rectification column RD1 <1> which then generates a methanol/water mixture GRD1 <108>.

[0037] In RD1<1> methanol is recovered by distillation as steam SRDB1<101>. Methanol recovered as SRDB1 vapor stream <101> is at withdrawal point <109> on top of RD1 <1> discharged and partially on top of rectification column RD1 <1> condensed in condenser KRD1 <102> and recycled into form liquid as reflux to the top of RD1 <1>. The remaining portion of the methanol recovered as SRDB1 vapor <101> is, for example, through a D13 throttle <11> decompressed to pressure p3A/p3B and introduced into the two reaction columns RRA <3A> and RRB <3B> as a stream of methanol SAE1 <3A01> and SBE1 <3B01> respectively.

[0038] An intermediate evaporator VZRD1 <107> is arranged in the rectification column RD1 <1> next to the bottom evaporator VSRD1 <106>, which can be used to supply energy to the mixture GRD1 <108> in RD1 <1>. For this purpose, the GRD1 mixture <108> is at a withdrawal point <111> discharged from the RD1 rectification column <1> as stream SRDX1 <112>. SRDX1 <112> is heated in VZRD1 <107> and recycled in the RD1 rectification column <1>.

[0039] At the lower end of RD1 <1> an SRDX1 bottom stream <103> comprising water and methanol is discharged at withdrawal point <110>. A first SRDX1 portion <104> of the SRDX1 <103> stream is supplied to a second water/methanol column RD2 <2>, a second SRDX12 portion <105> of the SRDX1 <103> stream is through a bottom evaporator VSRD1 < 106> recycled to RD1<1>. The pressure of SRDX1 <104> is via a pump P<15> increased to pressure p2 before this current is introduced into RD2 <2>.

[0040] A methanol/water mixture GRD2 <206> is thus obtained in the second rectification column RD2 <2>. In the RD2 rectification column <2> the methanol residues of SRDX1 <104> are separated from the water and recovered by means of distillation as steam stream SRDB2 <201> on top of RD2 <2>. Methanol recovered as vapor stream SRDB2 <201> is at withdrawal point <208> on top of RD2 <2> discharged and partially on top of rectification column RD2 <2> condensed in condenser KRD2 <203> and recycled to form liquid as reflux to the top of RD2 <2>. Optionally, additional methanol as stream SXE1<205> is through reflux on rectification column RD2<2> added thereto.

[0041] The remaining portion of the methanol recovered as steam SRDB2 <201> not supplied to the condenser KRD2 <203> is passed through the throttle D23 <14>, thus decompressed to pressure p3A or p3B and, together with the steam SRDB1 <101> from RD1 <1> decompressed to pressure p3A or p3B, introduced into RRA <3A> and RRB <3B> as methanol stream SAE1 <3A01> and SBE1 <3B01> respectively.

[0042] At the lower end of RD2 <2> an SRDS2 bottom stream <202> comprising water and optionally methanol is discharged at withdrawal point <207>. SRDS2 <202> is partially heated through a VSRD2 <204> bottom evaporator and recycled into RD2 <2>.

[0043] The energy released in the condensation of steam SRDB2 <201> at the top of RD2 <2> is through the intermediate evaporator VZRD1 <107> transferred to SRDX1 <112> and, after reintroduction of SRDX1 <112> into RD1 <1> , transferred from SRDX1 <112> to the GRD1 <108> mixture present in RD1 <1>. Alternatively or additionally, the energy released in the condensation of steam SRDB2 <201> on top of RD2 <2> is through the bottom evaporator VSRD1 <106> transferred to the SRDX12 <105> portion of the SRDX1 stream <103>. Once SRDX12 <105> is recycled into RD1 <1>, it transfers energy to the GRD1 <108> mixture present in RD1 <1>. The energy flow is shown by the dashed arrow <4>.

3.6 Figure 6

[0044] Figure 6 shows another embodiment of the process according to the invention for the production of alkali metal alkoxides with a corresponding interconnection of rectification columns. In this document, similarly to the modality described in Figure 5, two reactive rectification columns RRA <3A> and RRB <3B> at a pressure p3A and p3B respectively and two rectification columns RD1 <1> and RD2 <2> are employed in this document. having the pressures p1 and p2 respectively. In contrast to the embodiment according to figure 5, p2 > p3A > p1 and p2 > p3B > p1. The configuration shown in figure 6 corresponds to the configuration shown in figure 5, except that pressure p3A > p1 and pressure p3B > p1, thus allowing compressor VD31 <10> to be omitted and throttle D13 <11> to be replaced by VD13 compressor <16>.

3.7 Figure 7

[0045] Figure 7 shows an embodiment of the process according to the invention that corresponds to that described in figure 5. In that document, p2 > p1 > p3A and p1 > p3B. It shows the embodiment in which the energy released in the condensation of steam SRDB2 <201> at the top of RD2 <2> is directly through the bottom evaporator VSRD1 <106> transferred to the portion SRDX12 <105> of the stream SRDX1 <103 > which is recycled in RD1 <1>. The transfer is effected directly, as SRDB2<201> vapor is contacted with SRDX12<105> in VSRD1<106>, thus allowing the transfer of energy from SRDB2<201> to SRDX12<105> without, for example, interfering an additional heat transfer medium. The KRD2 <203> condenser shown in figure 5 can be omitted, and the fresh methanol stream SXE1 <205> is introduced in that document directly into column RD2 <2>.

3.8 Figure 8

[0046] Figure 8 shows an embodiment of the process according to the invention that corresponds to that described in figure 6. In that document, p2 > p3A > p1 and p2 > p3B > p1. It shows the embodiment in which the energy released in the condensation of steam SRDB2 <201> at the top of RD2 <2> is directly through the bottom evaporator VSRD1 <106> transferred to the portion SRDX12 <105> of the stream SRDX1 <103> which is recycled in RD1 <1>. The transfer is effected directly, as SRDB2<201> vapor is contacted with SRDX12<105> in VSRD1<106>, thus allowing the transfer of energy from SRDB2<201> to SRDX12<105> without, for example, interfering an additional heat transfer medium. The KRD2 <203> condenser shown in figure 6 can be omitted, and the fresh methanol stream SXE1 <205> is here introduced directly into the RD2 rectification column <2>.

3.9 Figure 9

[0047] Figure 9 shows an embodiment of the process according to the invention that corresponds to that described in figure 5. In that document, p2 > p1 > p3A and p1 > p3B. It shows the mode in which the energy released in the condensation of steam SRDB2 <201> on top of RD2 <2> is through the intermediate evaporator VZRD1 <107> transferred to the water/methanol mixture GRD1 <108> of RD1 <1>. GRD1 <108> is withdrawn from rectifying column RD1 <1> at withdrawal point <111> as current SRDX1 <112>. SRDB2 <201> transfers energy to SRDX1 <112> in VZRD1 <107>, especially by heating SRDX1 <112>. SRDX1 <112> is then recycled into the RD1 <1> rectification column.

[0048] In RD1<1> the SRDX1<112> current then transfers energy to the GRD1<108> mixture present in RD1<1>. Energy transfer from SRDB2 <201> to SRDX1 <112> is effected directly as SRDB2 <201> steam is contacted with SRDX1 <112> from RD1 <1> in VZRD1 <107>, thus allowing energy transfer from SRDB2 <201> to SRDX1 <112> from RD1 <1> without, for example, interposing another heat transfer medium. The KRD2 <203> condenser shown in figure 5 can be omitted, and the fresh methanol stream SXE1 <205> is here introduced directly into the RD2 rectification column <2>.

3.10 Figure 10

[0049] Figure 10 shows an embodiment of the process according to the invention that corresponds to that described in figure 6. In that document, p2 > p3A > p1 and p2 > p3B > p1. It shows the mode in which the energy released in the condensation of steam SRDB2 <201> on top of RD2 <2> is through the intermediate evaporator VZRD1 <107> transferred to the water/methanol mixture GRD1 <108> of RD1 <1>. GRD1 <108> is withdrawn from rectifying column RD1 <1> at withdrawal point <111> as current SRDX1 <112>. SRDB2 <201> transfers energy to SRDX1 <112> in VZRD1 <107>, especially by heating SRDX1 <112>. SRDX1 <112> is then recycled into the RD1 <1> rectification column.

[0050] In RD1<1> the SRDX1<112> current then transfers energy to the GRD1<108> mixture present in RD1<1>. Energy transfer from SRDB2 <201> to SRDX1 <112> is effected directly as SRDB2 <201> steam is contacted with SRDX1 <112> from RD1 <1> in VZRD1 <107>, thus allowing energy transfer from SRDB2 <201> to SRDX1 <112> from RD1 <1> without, for example, interposing another heat transfer medium. The KRD2 <203> condenser shown in figure 6 can be omitted, and the fresh methanol stream SXE1 <205> is here introduced directly into the RD2 rectification column <2>.

3.11 Figure 11

[0051] Figure 11 shows an embodiment of the process according to the invention that shows a combination of the embodiments according to figures 7 and 9. In that document, p2 > p1 > p3A and p1 > p3B. It shows the embodiment in which the energy released in the condensation of steam SRDB2 <201> at the top of RD2 <2> is directly through the bottom evaporator VSRD1 <106> transferred to the portion SRDX12 <105> of the stream SRDX1 <103> which is recycled in RD1 <1>. The transfer is effected directly, as SRDB2<201> vapor is contacted with SRDX12<105> in VSRD1<106>, thus allowing the transfer of energy from SRDB2<201> to SRDX12<105> without, for example, interfering an additional heat transfer medium.

[0052] After this heat transfer, more energy from the steam SRDB2 <201> is transferred through the intermediate evaporator VZRD1 to the water/methanol mixture GRD1 <108> from RD1 <1>. GRD1 <108> is withdrawn from rectifying column RD1 <1> at withdrawal point <111> as current SRDX1 <112>. SRDB2 <201> transfers energy to SRDX1 <112> in VZRD1 <107>, especially by heating SRDX1 <112>. SRDX1 <112> is then recycled into the RD1 <1> rectification column.

[0053] The transfer of energy from SRDB2 <201> to SRDX1 <112> is performed directly, as steam SRDB2 <201> is contacted with SRDX1 <112> from RD1 <1> in VZRD1 <107>, thus allowing the transfer of energy from SRDB2 <201> to SRDX1 <112> from RD1 <1> without, for example, interposing another means of heat transfer.

[0054] In RD1 <1> the SRDX1 <112> and SRDX12 <105> currents then transfer the energy absorbed by SRDB2 <201> to the GRD1 <108> mixture present in RD1.

3.12 Figure 12

[0055] Figure 12 shows an embodiment of the process according to the invention that corresponds to a combination of the embodiments of figures 8 and 10. In that document, p2 > p3A > p1 and p2 > p3B > p1. It shows an embodiment in which the energy released in the condensation of steam SRDB2 <201> on top of RD2 <2> is directly through the bottom evaporator VSRD1 <106> transferred to the portion SRDX12 <105> of the stream SRDX1 <103 > which is recycled in RD1 <1>. The transfer is effected directly, as SRDB2<201> vapor is contacted with SRDX12<105> in VSRD1<106>, thus allowing the transfer of energy from SRDB2<201> to SRDX12<105> without, for example, interfering an additional heat transfer medium.

[0056] After this heat transfer, more energy from the steam SRDB2 <201> is transferred through the intermediate evaporator VZRD1 to the water/methanol mixture GRD1 <108> from RD1 <1>. GRD1 <108> is withdrawn from the RD1 rectification column <1> after withdrawal point <111> as current SRDX1 <112>. SRDB2 <201> transfers energy to SRDX1 <112> in VZRD1 <107>, especially by heating SRDX1 <112>. SRDX1 <112> is then recycled into the RD1 <1> rectification column.

[0057] The transfer of energy from SRDB2 <201> to SRDX1 <112> is performed directly, as steam SRDB2 <201> is contacted with SRDX1 <112> from RD1 <1> in VZRD1 <107>, thus allowing the transfer of energy from SRDB2 <201> to SRDX1 <112> from RD1 <1> without, for example, interposing another means of heat transfer.

[0058] In RD1 <1> the SRDX1 <112> and SRDX12 <105> currents then transfer the energy absorbed by SRDB2 <201> to the GRD1 <108> mixture present in RD1 <1>.

4. Detailed description of the invention 4.1 Step (a1) of the process according to the invention

[0059] In step (a1) of the process according to the invention for producing at least one alkali metal alkoxide of formula MAOR an SAE1 reagent stream comprising ROH is reacted with an SAE2 reagent stream comprising MAOH in countercurrent at a pressure p3A and a T3A temperature on an RRA reactive rectification column to provide an RPA crude product comprising MAOR, water, ROH, MAOH.

[0060] According to the invention, a "reactive rectification column" is a rectification column in which the reaction according to step (a1) or step (a2) of the process according to the invention takes place at least in some parts. It can also be abbreviated to “reaction column”.

[0061] In step (a1) of the process according to the invention, a SAP bottoms product stream comprising ROH and MAOR is withdrawn at the lower end of RRA. A SAB steam stream comprising water and ROH is withdrawn at the top end of the RRA.

[0062] “Vapor stream” means that the respective stream is a gaseous stream.

[0063] In the process according to the invention, R is a C1-C6 hydrocarbon radical, preferably selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, pentyl isomers, such as n-pentyl, more preferably selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, even more preferably selected from the group consisting of methyl, ethyl. R is particularly preferably methyl and ROH is correspondingly methanol.

[0064] MA is selected from sodium, potassium, and preferably sodium.

[0065] The SAE1 reagent stream comprises ROH. In a preferred embodiment, the mass fraction of ROH in SAE1 based on the total mass of the SAE1 reagent stream is ≥ 95% by weight, even more preferably ≥ 99% by weight, where SAE1 especially comprises water.

[0066] The ROH alcohol used as the SAE1 reagent stream in step (a1) of the process according to the invention may also be a commercially available alcohol having a mass fraction of alcohol, based on the total mass of the SAE1 reagent stream, of greater than 99.8% by weight and a mass fraction of water, based on the total mass of the SAE1 reagent stream, of up to 0.2% by weight.

[0067] The SAE1 reagent stream is preferably introduced in the form of a vapour.

[0068] The SAE2 reagent stream comprises MAOH. In a preferred embodiment, SAE2 comprises not only MAOH, but also at least one other compound selected from water, ROH. SAE2 most preferably comprises water in addition to MAOH, in which case SAE2 is an aqueous solution of MAOH.

[0069] When the SAE2 reagent stream comprises MAOH and water, the mass fraction of MAOH based on the total weight of the SAE2 reagent stream is especially in the range of 10% to 55% by weight, preferably 15% to 54 % by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight, most preferably 50% by weight.

[0070] When the SAE2 reagent stream comprises MAOH and ROH, the mass fraction of MAOH, based on the total weight of the SAE2 reagent stream, is especially in the range of 10% to 55% by weight, preferably 15% to 54% by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight.

[0071] In the particular case where the SAE2 reagent stream comprises water and ROH in addition to MAOH, it is particularly preferable when the mass fraction of MAOH, based on the total weight of the SAE2 reagent stream, is especially in the range of 10% to 55% by weight, preferably from 15% to 54% by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight.

[0072] Step (a1) of the process according to the invention is carried out in a reactive rectification column (or "reaction column") RRA.

[0073] Step (a2) of the process according to the invention is carried out in a reactive rectification column (or "reaction column") RRB.

[0074] The RRA/RRB reaction column preferably contains internal components. Suitable internal components are, for example, plates, structured fillings or unstructured fillings. When the RRA/RRB reaction column contains dishes, hood dishes, valve dishes, tunnel dishes, Thormann dishes, cross-slotted hood dishes or sieve dishes are suitable. When the RRA/RRB reaction column contains trays, it is preferable to choose trays where not more than 5% by weight, more preferably less than 1% by weight, of the liquid flows through the respective trays. The construction measures necessary to minimize liquid dripping are familiar to those skilled in the art. In the case of valve plates, for example, particularly tight shut-off valve configurations are selected. Reducing the number of valves also makes it possible to increase the steam velocity at the plate openings to twice the typically established value. When using sieve plates it is particularly advantageous to reduce the diameter of the plate openings by maintaining or even increasing the number of openings.

[0075] When using structured or unstructured fillings, structured fillings are preferred in terms of uniform distribution of the liquid. In this embodiment, it is still preferable when in all parts of the cross-section of the column corresponding to more than 2% of the total cross-section of the column the average ratio of liquid flow to vapor flow is not exceeded by more than 15%, more than preference for more than 3%, in relation to the liquid. This minimized amount of liquid makes it possible for the capillary effect on the wire meshes to eliminate local spikes in liquid dripping density.

[0076] For columns comprising unstructured packings, especially comprising random packings, and for columns comprising structured packings, the desired liquid distribution characteristics can be achieved when the dripping density of the liquid in the border region of the column cross section adjacent to the column shell, corresponding to about 2% to 5% of the total column cross section, is reduced compared to the other cross section regions by up to 100%, preferably by 5% to 15%. This can easily be achieved, for example, by targeted distribution from the dripping points of liquid dispensers or holes in them.

[0077] The process according to the invention can be carried out continuously or discontinuously. It is preferably carried out continuously.

[0078] According to the invention, the “reaction of an SAE1 reagent stream comprising ROH with an SAE2 reagent stream comprising MAOH in countercurrent” is achieved, in particular, as a result of the feed point for at least a portion of the SAE1 reagent stream comprising ROH in step (a1) being located in the RRA reaction column below the feed point of the SAE2 reagent stream comprising MAOH.

[0079] The RRA reaction column preferably comprises at least 2, in particular 15 to 40, theoretical plates between the feed point of the SAE1 reagent stream and the feed point of the SAE2 reagent stream.

[0080] The RRA reaction column is preferably operated as a pure stripping column. Thus, the SAE1 reagent stream comprising ROH is supplied especially in vapor form in the lower region of the RRA reaction column. Step (a1) of the process according to the invention also comprises the case where a portion of the reagent stream SAE1 comprising ROH is added in vapor form below the feed point of the reagent stream SAE2 comprising MAOH, but nevertheless , at the top end or top end region of the RRA reaction column. This allows you to reduce the dimensions in the lower region of the RRA reaction column. When a portion of the SAE1 reagent stream comprising ROH, in particular methanol, is added especially in vapor form to the head end or head end region of the RRA reaction column only a fraction of 10% to 70% by weight, preferably from 30% to 50% by weight, (in each case based on the total amount of alcohol ROH employed in step (a1) as SAE1) is supplied at the lower end of the RRA reaction column and the remaining fraction is added in form of steam in a single stream or divided into a plurality of substreams preferably 1 to 10 theoretical plates, particularly preferably 1 to 3 theoretical plates, below the feed point of the SAE2 reagent stream comprising MAOH.

[0081] In the RRA reaction column, the SAE1 reagent stream comprising ROH is then reacted with the SAE2 reagent stream comprising MAOH according to reaction <1> described above to provide MAOR and H2O, where these products are present in admixture with the reagents ROH and MAOH since this is an equilibrium reaction. Thus, a crude RPA product containing not only the MAOR and water products, but also ROH and MAOH is obtained on the RRA reaction column in step (a1) of the process according to the invention.

[0082] The bottom SAP product stream comprising ROH and MAOR is then obtained and withdrawn at the lower end of RRA.

[0083] A water-containing alcohol stream, currently referred to as "SAB steam stream comprising water and ROH", is withdrawn at the top end of RRA, preferably at the top of the RRA column.

[0084] The amount of alcohol ROH comprised by the reagent stream SAE1 is preferably chosen so that said alcohol simultaneously serves as a solvent for the alkali metal alkoxide MAOR obtained in the bottom product stream SAP. The amount of ROH alcohol in the SAE1 reagent stream is preferably chosen to achieve at the bottom of the RRA reaction column the desired concentration of the alkali metal alkoxide solution which is withdrawn as a SAP bottoms product stream comprising ROH and MAOR. for the MAOR alkali metal alkoxide obtained in the SAP bottoms product stream. The amount of ROH alcohol in the SAE1 reagent stream is preferably chosen to achieve at the bottom of the RRA reaction column the desired concentration of the alkali metal alkoxide solution which is withdrawn as a SAP bottoms product stream comprising ROH and MAOR.

[0085] In a preferred embodiment of the process according to the invention, and especially in cases where SAE2 also comprises water in addition to MAOH, the ratio of the total weight (masses; unit: kg) of ROH alcohol used as SAE1 reagent stream in step (a1) for the total weight (masses; unit: kg) of MAOH used as the SAE2 reagent stream in step (a1) is from 1:1 to 50:1, more preferably 5:1 to 48:1, even more preferably 9:1 to 35:1, even more preferably 10:1 to 30:1, even more preferably 13:1 to 22:1, most preferably 14:1.

[0086] The RRA reaction column is operated with or without, preferably without reflux.

[0087] "No backflow" means that the SAB steam stream withdrawn at the top end of RRA comprising water and ROH is completely supplied to the first rectification column RD1 according to step (b). The SAB steam stream comprising water and ROH is preferably supplied to the first rectification column RD1 in the form of steam.

[0088] "With reflux" means that the SAB steam stream withdrawn at the top end of the respective column, the RRA reaction column in step (a1), comprising water and ROH is not completely discharged, that is, it is not completely supplied to the first rectification column RD1 in step (b), but is at least partially, preferably partially, recycled to the respective column, i.e. the RRA reaction column in step (a1), as reflux. In cases where such reflux is established, the reflux ratio is preferably 0.05 to 0.99, more preferably 0.1 to 0.9, even more preferably 0.11 to 0.34, particularly preferably 0.14 to 0.27 and very particularly preferably 0.17 to 0.24. A reflux can be established by attaching to the top of the respective column, the RRA reaction column in step (a1), a KRRA condenser in which the SAB vapor stream is at least partially condensed and sent back to the respective column, the RRA reaction column in step a1). Generally and in the context of the present invention, reflux ratio should be understood as meaning the ratio between the mass flow (kg/h) recycled and the respective column in liquid form (reflux) and the mass flow (kg/h) discharged from the respective column in liquid form (distillate) or in gaseous form (vapor).

[0089] In the embodiment in which a reflux is established in the RRA reaction column, the MAOH alcohol employed in step (a1) as the SAE2 reagent stream can also be at least partially, preferably partially, mixed with the reflux stream and the resulting mixture will thus be fed to step (a1).

[0090] Step (a1) of the process according to the invention is carried out in particular at a temperature T3A in the range of 25°C to 200°C, preferably in the range of 45°C to 150°C, more preferably in the range of 47°C to 120°C, more preferably in the range of 60°C to 110°C.

[0091] Step (a1) of the process according to the invention is carried out in particular at a pressure p3A of 0.5 bar (500 kPa) to 40 bar (4 MPa), preferably in the range of 0.75 bar ( 75 kPa) to 5 bar (500 kPa), more preferably in the range 1 bar (100 kPa) to 2 bar (200 kPa), more preferably in the range 1 bar (100 kPa) to 1.8 bar (180 kPa), even more preferably from 1.1 bar (110 kPa) to 1.6 bar (160 kPa). It is an essential feature of the invention that when establishing the p3A pressure: p2 > p3A. It is especially also the case that p3A > p1.

[0092] The RRA reaction column comprises in a preferred embodiment at least one evaporator which is in particular selected from intermediate evaporators VZ3A and bottom evaporators VS3A. The RRA reaction column particularly preferably comprises at least one VS3A bottom evaporator. Evaporators are special types of WT heat exchangers.

[0093] K condensers are also special types of WT heat exchangers. Typical capacitors are known to those skilled in the art. These are preferably employed as liquefaction media on top of rectification columns and reaction columns. In the direct transfer of energy from the top stream of one column to the bottom or middle stream of another column, a condenser from one column can be used simultaneously as an evaporator from the other column (as shown in the examples).

[0094] According to the invention, VZ "intermediate evaporators" (for example, VZ3A in RRA, VZ3B in RRB, VZRD1 in RD1, VZRD2 in RD2) are to be understood as evaporators arranged above the bottom of the respective column, in particular above from the bottom of the RRA/RRB reaction column or above the bottom of the RD1 or RD2 rectification column. They, in particular, evaporate the crude RPA/RPB or SRDX1Z product as a sidestream.

[0095] According to the invention "bottom evaporators" VS (for example VS3A in RRA, VS3B in RRB, VSRD1 in RD1, VSRD2 in RD2) should be understood as meaning evaporators that heat the bottom of the respective column, in particular the bottom of RRA/RRB reaction column or RD1 or RD2 rectification column. They evaporate the background product stream (eg SAP/SBP or SRDX1S).

[0096] An evaporator is typically arranged outside the respective reaction column or rectification column. The mixture to be evaporated in the evaporator is withdrawn from the column by means of an outlet or "draw point" and supplied to at least one evaporator.

[0097] The evaporated mixture is recycled back to the respective column, optionally with a residual proportion of liquid, through a feed or “feed point”. When the evaporator is an intermediate evaporator, the outlet through which the respective mixture is withdrawn and supplied to the evaporator is a side stream outlet and the feed through which the respective evaporated mixture is sent back to the column is a feed of side chain. When the evaporator is a bottom evaporator, i.e. it heats the bottom of the column, at least a portion of the bottom stream is evaporated and recycled back to the respective column in the bottom region of the column.

[0098] However, alternatively, it is also possible, for example, in a suitable dish when using an intermediate evaporator or at the bottom of the respective column, to provide tubes which are traversed by the relevant heating medium. In this case, evaporation takes place on the plate or at the bottom of the column. However, it is preferable to arrange the evaporator outside the respective column.

[0099] Suitable evaporators that can be used as intermediate evaporators and bottom evaporators include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation evaporators with decompression, steam boilers, falling film evaporators or film evaporators thin. Heat exchangers for evaporation typically employed in the case of natural circulation evaporators and forced circulation evaporators are shell and tube or plate apparatus. When using a shell and tube exchanger, the heating medium can flow through the tubes with the mixture to be evaporated flowing around the tubes or else the heating medium can flow around the tubes with the mixture to be evaporated flowing through the tubes. tubes. In the case of a falling film evaporator, the mixture to be evaporated is typically introduced as a thin film inside a tube and the tube is heated externally. Unlike a falling film evaporator, a thin film evaporator further comprises a rotor with wipers which distribute the liquid to be evaporated on the inner wall of the tube to form a thin film.

[00100] In addition to the types of evaporator cited, however, it is also possible to employ any other desired type of evaporator known to those skilled in the art and suitable for use in a rectifying column.

[00101] When the RRA reaction column/RRB reaction column has an intermediate evaporator VZ3A or VZ3B, it is preferable that the respective intermediate evaporator is arranged in the exhaustion region of the RRA reaction column in the region of the reagent stream feed column SAE1 or in the case of the RRB reaction column in the SBE1 reagent stream feedpoint region. This allows introducing a predominant portion of the thermal energy through the intermediate evaporator VZ3A/VZ3B. It is thus possible, for example, to introduce more than 80% of the energy through the intermediate evaporator. According to the invention, the intermediate evaporator VZ3A/VZ3B is preferably arranged and/or configured so as to introduce more than 50%, in particular more than 75%, of the total energy required for the reactive rectification.

[00102] When the RRA reaction column/RRB reaction column has an intermediate evaporator VZ3A or VZ3B, it is additionally advantageous when the intermediate evaporator is arranged so that the RRA/RRB reaction column has 1 to 50 theoretical plates below the evaporator intermediate and 1 to 200 theoretical plates above the intermediate evaporator. It is especially preferred when the RRA/RRB reaction column then has 2 to 10 theoretical plates below the intermediate evaporator and 20 to 50 theoretical plates above the intermediate evaporator.

[00103] When the RRA reaction column/RRB reaction column has a VZ3A/VZ3B intermediate evaporator, it is also advantageous when the side stream exit (i.e., the “ERRA withdrawal point” in the RRA reaction column/o “ outlet point ERRB” on the RRB reaction column) through which the RPA/RPB crude product is supplied to the intermediate evaporator VZ3A/VZ3B and the side stream feed (i.e. the “ZRRA withdrawal point” on the reaction column RRA/the “ZRRB withdrawal point” on the RRB reaction column) whereby the RPA/RPB evaporated crude product from the VZ3A/VZ3B intermediate evaporator is sent back to the respective RRA/RRB reaction column are positioned therebetween RRA reaction column/RRB reaction column plates. However, it is also possible that the side stream outlet and the side stream feed are arranged at different heights.

[00104] In a preferred embodiment, when using a VZ3A/VZ3B intermediate evaporator in RRA/RRB, the diameter of the RRA/RRB reaction column above the RRA/RRB intermediate evaporator is greater than the diameter of the RRA/RRB reaction column below of the intermediate evaporator VZ3A/VZ3B. This has the advantage of allowing capital expenditure savings.

[00105] In such intermediate evaporator VZ3A/VZ3B RPA liquid crude product comprising MAOR, water, ROH, MAOH present in RRA reaction column or RPB liquid crude product comprising MBOR, water, ROH, MBOH present in RRB reaction column can be converted in the gaseous state, or if it is already in the gaseous state heated further, thus improving the efficiency of the reaction according to step (a1)/(a2) in the process according to the invention.

[00106] The arrangement of one or more VZ3A intermediate evaporators in the upper region of the RRA reaction column or one or more VZ3B intermediate evaporators in the upper region of the RRB reaction column allows reducing the dimensions in the lower region of the RRA reaction column/ RRB. In the modality with at least one, preferably two or more intermediate evaporators VZ3A/VZ3B, it is also possible to supply ROH undercurrents in liquid form in the upper region of the RRA/RRB reaction column.

[00107] According to the invention, the bottom evaporators are arranged at the bottom of the RRA/RRB reaction column and are then referred to as “VS3A” and “VS3B”. The SAP/SBP bottoms stream present in the RRA/RRB reaction column can be passed to such a bottoms evaporator and ROH at least partially removed therefrom to obtain a SAP* bottoms stream having a high mass fraction of MAOR compared to SAP/ to obtain a bottom product stream SBP* with a high mass fraction of MBOR compared to SBP.

[00108] In step (a1) of the process according to the invention, a SAP bottoms product stream comprising ROH and MAOR is withdrawn at the lower end of the RRA reaction column.

[00109] It is preferred when the RRA reaction column comprises at least one VS3A bottoms evaporator through which the SAP bottoms product stream is then at least partially passed to at least partially remove ROH, thereby providing a bottoms product stream SAP* having an elevated mass fraction of MAOR compared to SAP.

[00110] The mass fraction of MAOR in the bottom product stream SAP* is especially high compared to the mass fraction of MAOR in the bottom product stream SAP by at least 1%, preferably by ≥ 2%, more preferably at ≥ 5%, even more preferably at ≥ 10%, even more preferably at ≥ 20%, even more preferably at ≥ 30%, even more preferably at ≥ 40%, even more preferably at ≥ 50 %, even more preferably ≥ 100%, even more preferably ≥ 150%.

[00111] It is preferred when SAP or, if at least one VS3A bottom evaporator is used, through which the SAP bottom product stream is at least partially passed to at least partially remove ROH, SAP* has a mass fraction of MAOR in ROH in the range of 1% to 50% by weight, preferably 5% to 32% by weight, more preferably 15% to 32% by weight, most preferably 30% to 32% by weight, in each case with based on the total mass of SAP/SAP*.

[00112] The mass fraction of residual water in SAP/SAP* is preferably < 1% by weight, preferably < 0.1% by weight, most preferably < 0.01% by weight, based on the total mass of SAP/SAP*.

[00113] The mass fraction of the MAOH reagent in SAP/SAP* is preferably < 1% by weight, preferably < 0.1% by weight, most preferably < 0.01% by weight, based on the total mass of SAP/SAP*.

4.2 Step (a2) of the process according to the invention (optional)

[00114] According to the invention, step (a2) is performed or not. In optional step (a2), which proceeds simultaneously and spatially separately from step (a1) of the process according to the invention, a reagent stream SBE1 comprising ROH is reacted with a reagent stream SBE2 comprising MBOH in countercurrent at a pressure p3B and a T3B temperature on an RRB reactive rectification column to provide an RPB crude product comprising MBOR, water, ROH, MBOH.

[00115] In the optional step (a2) of the process according to the invention, a bottom product stream SBP comprising ROH and MBOR is withdrawn at the lower end of RRB. An SBB steam stream comprising water and ROH is withdrawn at the top end of the RRB.

[00116] MB is selected from sodium, potassium and preferably potassium.

[00117] The SBE1 reagent stream comprises ROH. In a preferred embodiment, the mass fraction of ROH in SBE1 based on the total mass of the SBE1 reagent stream is ≥ 95% by weight, even more preferably ≥ 99% by weight, where SBE1 especially comprises water.

[00118] The ROH alcohol used as the SBE1 reagent stream in the optional step (a2) of the process according to the invention can also be a commercial alcohol having a mass fraction of alcohol, based on the total mass of the SBE1 reagent stream, greater than 99.8% by weight and a mass fraction of water, based on the total mass of the SBE1 reagent stream, of up to 0.2% by weight.

[00119] The SBE1 reagent stream is preferably introduced in the form of a vapour.

[00120] The SBE2 reagent stream comprises MBOH. In a preferred embodiment, SBE2 comprises not only MBOH, but also at least one other compound selected from water, ROH. It is even more preferable when SBE2 comprises water in addition to MBOH, thus making SBE2 an aqueous MBOH solution.

[00121] When the SBE2 reagent stream comprises MBOH and water, the mass fraction of MBOH based on the total weight of the SBE2 reagent stream is especially in the range of 10% to 55% by weight, preferably 15% to 54 % by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight, most preferably 50% by weight.

[00122] When the SBE2 reagent stream comprises MBOH and ROH, the mass fraction of MBOH, based on the total weight of the SBE2 reagent stream, is especially in the range of 10% to 55% by weight, preferably 15% to 54% by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight.

[00123] In the particular case where the SBE2 reagent stream comprises water and ROH in addition to MBOH, it is particularly preferable when the mass fraction of MBOH, based on the total weight of the SBE2 reagent stream, is especially in the range of 10% to 55% by weight, preferably from 15% to 54% by weight, more preferably from 30% to 53% by weight and particularly preferably from 45% to 52% by weight.

[00124] Step (a2) of the process according to the invention is carried out in a reactive rectification column (or "reaction column") RRB. Preferred embodiments of the RRB reaction column are described in section 4.1.

[00125] According to the invention, the “reaction of an SBE1 reagent stream comprising ROH with an SBE2 reagent stream comprising MBOH in countercurrent” is especially achieved as a result of the feed point for at least a portion of the reagent stream SBE1 comprising ROH in optional step (a2) being arranged below the feed point for the reagent stream SBE2 comprising MBOH on the RRB reaction column.

[00126] The RRB reaction column preferably comprises at least 2, in particular 15 to 40, theoretical plates between the feed point of the reagent stream SBE1 and the feed point of the reagent stream SBE2.

[00127] The RRB reaction column is preferably operated as a pure stripping column. Thus, the SBE1 reagent stream comprising ROH is supplied especially in vapor form in the lower region of the RRB reaction column. Optional step (a2) of the process according to the invention also covers the case where part of the reagent stream SBE1 comprising ROH is introduced in vapor form below the feed point of the reagent stream SBE2 comprising aqueous sodium hydroxide solution MBOH , but notwithstanding at the top end or in the top end region of the RRB reaction column. This makes it possible to reduce the dimensions of the lower region of the RRB reaction column. When a portion of the SBE1 reagent stream comprising ROH, in particular methanol, is added especially in vapor form at the top end or top end region of the RRB reaction column, only a fraction of, in particular, 10% to 70% by weight, preferably from 30% to 50% by weight, (in each case based on the total amount of alcohol ROH employed in optional step (a2)) is supplied to the lower end of the RRB reaction column and the remaining fraction is added in vapor form in a single stream or divided into a plurality of substreams preferably 1 to 10 theoretical plates, particularly preferably 1 to 3 theoretical plates, below the feed point of the reagent stream SBE2 comprising MBOH.

[00128] In the RRB reaction column, the SBE1 reagent stream comprising ROH is then reacted with the SBE2 reagent stream comprising MBOH according to reaction <1> described above to generate MBOR and H2O, where these products are present in admixture with the ROH and MBOH reagents since this is an equilibrium reaction. Thus, a crude RPB product which contains not only the MBOR and water products, but also ROH and MBOH is obtained on the RRB reaction column in optional step (a2) of the process according to the invention.

[00129] The bottom product stream SBP comprising ROH and MBOR is then obtained and withdrawn at the lower end of RRB.

[00130] A water-containing alcohol stream, currently referred to as "SBB steam stream comprising water and ROH", is withdrawn at the top end of the RRB, preferably at the top of the RRB.

[00131] This SBB steam stream comprising water and ROH is supplied to step (b) of the process according to the invention. Said stream is mixed with SAB before being fed to step (b) of the process according to the invention or not, i.e. it is fed to step (b) of the process according to the invention separately from SAB. The SBB steam stream is preferably mixed with SAB and the resulting mixed steam stream is then introduced into step (b) of the process according to the invention.

[00132] The amount of ROH alcohol comprised in the SBE1 reagent stream is preferably selected so that it simultaneously serves as a solvent for the MBOR alkali metal alkoxide present in the SBP bottoms product stream. The amount of ROH alcohol in the SBE1 reagent stream is preferably chosen to achieve at the bottom of the reaction column the desired concentration of the alkali metal alkoxide solution which is withdrawn as an SBP bottoms product stream comprising ROH and MBOR.

[00133] In a preferred embodiment of the optional step (a2) of the process according to the invention, and especially in cases where SBE2 comprises water in addition to MBOH, the ratio of the total weight (masses; units: kg) of ROH alcohol used in step (a2) as reagent stream SBE1 for the total weight (masses; unit: kg) of MBOH employed in step (a2) as reagent stream SBE2 is 1:1 to 50:1, more preferably 5:1 to 48:1, even more preferably 9:1 to 35:1, even more preferably 10:1 to 30:1, even more preferably 13:1 to 22:1, most preferably 14:1.

[00134] The RRB reaction column is operated with or without, preferably without reflux.

[00135] "No backflow" means that the SBB steam stream withdrawn at the top end of the RRB comprising water and ROH is completely supplied to the RD1 rectification column according to step (b). The SBB steam stream comprising water and ROH is preferably supplied to the RD1 rectification column in the form of steam.

[00136] "With reflux" means that the SBB steam stream withdrawn at the top end of the respective column, the RRB reaction column in step (a2), comprising water and ROH is not completely discharged, that is, it is not completely supplied to the first rectification column RD1 in step (b), but is at least partially, preferably partially, recycled to the respective column, reaction column RRB in step (a2), as reflux. In cases where such reflux is established, the reflux ratio is preferably 0.05 to 0.99, more preferably 0.1 to 0.9, even more preferably 0.11 to 0.34, particularly preferably 0.14 to 0.27 and very particularly preferably 0.17 to 0.24. A reflux can be established by affixing to the top of the respective column, RRB reaction column in step (a2), a KRRB condenser in which the SBB vapor stream is at least partially condensed and sent back to the respective column, the reaction column RRB in step (a2).

[00137] In the embodiment in which a reflux is established in the RRB reaction column, the MBOH alcohol employed in the optional step (a2) as the SBE2 reagent stream can also be at least partially, preferably partially, mixed with the reflux stream and the resulting mixture will thus be supplied to step (a2).

[00138] The optional step (a2) of the process according to the invention is carried out in particular at a temperature T3B in the range of 25°C to 200°C, preferably in the range of 45°C to 150°C, more than preferably in the range 47°C to 120°C, more preferably in the range 60°C to 110°C.

[00139] The optional step (a2) of the process according to the invention is carried out in particular at a pressure p3B of 0.5 bar (50 kPa) to 40 bar (4 MPa), preferably in the range of 0.75 bar (75 kPa) to 5 bar (500 kPa), more preferably in the range 1 bar (100 kPa) to 2 bar (200 kPa), more preferably in the range 1 bar (100 kPa) to 1.8 bar ( 180 kPa), even more preferably from 1.1 bar (110 kPa) to 1.6 bar (160 kPa). It is an essential feature of the invention that when setting the p3B pressure: p2 > p3B. It is especially also the case that p3B > p1.

[00140] In a preferred embodiment, the RRB reaction column comprises at least one evaporator which is selected in particular from intermediate evaporators VZB and bottom evaporators VSB. The RRB reaction column particularly preferably comprises at least one bottom evaporator VS3B.

[00141] In the optional step (a2) of the process according to the invention, a bottom product stream SBP comprising ROH and MBOR is withdrawn at the lower end of the RRB reaction column.

[00142] It is preferred when the RRB reaction column comprises at least one VS3B bottoms evaporator through which the SBP bottoms product stream is then at least partially passed to at least partially remove ROH, thereby providing a bottoms product stream SBP* having an elevated MBOR mass fraction compared to SBP.

[00143] The mass fraction of MBOR in bottom product stream SBP* is especially high compared to the mass fraction of MBOR in bottom product stream SBP by at least 1%, preferably by ≥ 2%, more preferably at ≥ 5%, even more preferably at ≥ 10%, even more preferably at ≥ 20%, even more preferably at ≥ 30%, even more preferably at ≥ 40%, even more preferably at ≥ 50 %, even more preferably ≥ 100%, even more preferably ≥ 150%.

[00144] It is preferred when SBP or, if at least one VS3B bottoms evaporator is used, through which the SBP bottoms product stream is at least partially passed to at least partially remove ROH, SBP* has a mass fraction of MBOR in ROH in the range of 1% to 50% by weight, preferably 5% to 32% by weight, more preferably 10% to 32% by weight, most preferably 15% to 30% by weight, in each case with based on the total mass of SBP/SBP*.

[00145] The mass fraction of residual water in SBP/SBP* is preferably < 1% by weight, preferably < 0.1% by weight, most preferably < 0.01% by weight, based on the total mass of SBP/SBP*.

[00146] The mass fraction of the MBOH reagent in SBP/SBP* is preferably < 1% by weight, preferably < 0.1% by weight, most preferably < 0.01% by weight, based on the total mass of SBP/SBP*.

[00147] In the embodiments of the present process in which step (a2) is also carried out, it is preferable when the SAP bottoms product stream is at least partially passed through a VS3A bottoms evaporator and ROH is at least partially removed from the SAP to provide a SAP* bottoms product stream having a high MAOR mass fraction compared to SAP and/or, preferably e, the SBP bottoms product stream is at least partially passed through a VS3B bottoms evaporator and ROH is at least partially removed from the SBP to provide a bottom product stream SBP* having a high mass fraction of MBOR compared to SBP.

[00148] In the embodiments of the present invention in which step (a2) of the process according to the invention is performed simultaneously and spatially separated from step (a1). Spatial separation is ensured by performing steps (a1) and (a2) on both RRA and RRB reaction columns.

[00149] In an advantageous embodiment of the invention, the RRA and RRB reaction columns are accommodated in a column shell, where the column is at least partially subdivided by at least one dividing wall. Such a column having at least one dividing wall will, according to the invention, be referred to as "DWC". Such partition wall columns are familiar to those skilled in the art and are described, for example, in US 2,295,256, EP 0 122 367 A2, EP 0 126 288 A2, WO 2010/097318 A1 and I. Dejanović, Lj. Matijašević, Ž. Olujić, Chemical Engineering and Processing 2010, 49, 559-580. In partition wall columns suitable for the process according to the invention, the partition walls preferably extend to the floor of the column and, in particular, preferably comprise at least a quarter, more preferably at least a third, even more preferably at least half, even more preferably at least two-thirds, even more preferably at least three-quarters, of the column by height. They divide the columns into at least two reaction spaces in which spatially separated reactions can be carried out. The reaction spaces provided by at least one dividing wall can be of identical or different sizes.

[00150] In this embodiment, the SAP and SBP bottom product streams can be withdrawn separately in the respective regions separated by the dividing wall and preferably passed through the VS3A/VS3B bottom evaporator attached to each reaction space formed by at least one wall reaction in which ROH is at least partially removed from SAP/SBP to obtain SAP*/SBP*.

4.3 Step (b) of the process according to the invention

[00151] In step (b) of the process according to the invention, the SAB steam stream and if step (a2) is carried out, the SBB steam stream in mixture with SAB or separately from SAB is passed to a first column of RD1 grinding.

[00152] To obtain a GRD1 mixture comprising water and ROH in the RD1 rectification column.

[00153] In the optional embodiment of the process according to the invention in which step (a2) is carried out, the SBB steam stream is preferably mixed with SAB and the SABB steam mixture obtained is then introduced into a rectification column RD1 .

[00154] In one embodiment of the present invention (when p3A < p1/p3B < p1) the SAB steam stream and, in cases where the optional step (a2) is carried out, the SBB steam stream can be compressed before passing for the RD1 grinding column. This can be done using a VD31 compressor. However, in the embodiments of the present invention in which p3A > p1 and p3B > p1 it is not necessary to supply a VD31 compressor and it is then possible to save on its supply and on the electrical energy required for it.

[00155] It will be appreciated that even in embodiments where the optional step (a2) is carried out and SBB is introduced into the rectification column RD1 separately from SAB, SAB and SBB undergo mixing in the rectification column RD1 with the result that a GRD1 mixture comprising water and ROH is always obtained in the first rectification column RD1 after carrying out step (b).

[00156] Any desired rectification column known to those skilled in the art can be used as the RD1 rectification column in step (b) of the process according to the invention. The RD1 grinding column preferably contains internal components. Suitable inner components are, for example, plates, unstructured fillings or structured fillings. As dishes, bell dishes, sieve dishes, valve dishes, tunnel dishes or slit dishes are usually used. Unstructured packings are usually beds of random packing elements. Commonly used random filling elements are Raschig rings, Pall rings, Berl saddles or Intalox® saddles. Structured fillings are, for example, marketed under the trade name Mellapack® by Sulzer. In addition to the mentioned internal components, other suitable internal components are known to a person skilled in the art and can also be used.

[00157] The preferred internals have a low specific pressure drop per theoretical plate. Structured fillings and random filling elements have, for example, a significantly lower pressure drop per theoretical plate than plates. This has the advantage that the pressure drop in the rectification column remains as low as possible and thus the mechanical power of the compressor and the temperature of the alcohol/water mixture GRD1 to be thus evaporated remain low.

[00158] When the RD1 rectification column contains structured or unstructured packing, these can be divided or in the form of an uninterrupted packing. However, usually at least two packings are provided, one packing above the SAB steam stream feed point/the SAB and SBB steam stream feed points and one packing below the SAB steam stream feed point/ the feed points of the two SAB and SBB steam streams/the SABB mixed steam feed point. If an unstructured filling is used, for example a random filling, the random filling elements are typically arranged in a suitable sieve dish or mesh dish.

[00159] At the end of step (b) of the process according to the invention, a GRD1 mixture comprising water and ROH is finally obtained in the RD1 rectification column. The composition of the GRD1 mixture results in particular from the composition of the SAB steam stream and whether step (a2) is carried out partially from the composition of the two SAB and SBB steam streams in particular.

4.4 Step (c) of the process according to the invention

[00160] In step (c) of the process according to the invention, the GRD1 mixture comprising water and ROH is in the first rectification column RD1 at a pressure p1 and a temperature T1 separated into a steam stream comprising ROH SRDB1 at the end of the top (=top) of RD1 and a bottom stream SRDX1 comprising water and ROH at the bottom (=bottom) end of RD1.

[00161] With the exception of the condition that p2 > p1, the pressure p1 in RD1 can be chosen by those skilled in the technique according to their knowledge of the technique. It is preferably in the range between 1 bar (100 kPa) and 20 bar (2 MPa), preferably 1 bar (100 kPa) and 15 bar (1.5 MPa), more preferably 1 to 10 bar (100 kPa to 1 MPa), even more preferably 1.00 to 3.00 bar (100 kPa to 300 kPa), even more preferably 1.00 to 2.0 bar (100 kPa to 200 kPa), even more preferably 1.00 at 1.50 bar (100 kPa to 150 kPa), where, simultaneously, p2 > p1.

[00162] The T1 temperature in the RD1 can be chosen by those skilled in the art according to their knowledge of the art. It is preferably in the range from 40°C to 220°C, preferably from 60°C to 190°C.

[00163] In a preferred embodiment p3A > p1 and, in addition, in cases where step (a2) is performed, in addition p3B > p1. As a result of this built-in pressure, the total process energy demand is surprisingly minimized compared to modalities where p3A < p1/p3B < p1.

[00164] The separation according to step (c) of the process according to the invention is a separation by distillation of the GRD1 alcohol/water mixture as is known to those skilled in the art.

[00165] At the lower end (also: "bottom") of the RD1 rectification column, a bottom stream SRDX1 still comprising ROH alcohol is obtained. SRDX1 comprises ROH in a mass fraction of, in particular, 0.005% to 95% by weight, preferably 25% to 95% by weight, based on the total mass of SRDX1. SRDX1 preferably comprises essentially water in addition to the ROH alcohol.

[00166] In a preferred embodiment of the invention, SRDB1 is at least partially employed as an SAE1 reagent stream in the RRA reactive rectification column and if step (a2) is carried out alternatively or additionally employed as an SBE1 reagent stream in the reactive rectification column RRB.

[00167] It is also obtained at the top of the rectification column RD1 the steam stream SRDB1 comprising ROH. The preferred mass fraction of ROH in this SRDB1 vapor stream is ≥ 99% by weight, preferably ≥ 99.6% by weight, most preferably ≥ 99.9% by weight, in each case based on the total mass of SRDB1 , where the remainder is mostly water.

[00168] In step (c) the SAB or SAB and SBB steam obtained in step (a1) or step (a1) and (a2) is subjected to separation by distillation. These vapors essentially comprise ROH alcohol and water. In particular, each of SAB or SAB and SBB is a water/alcohol mixture in which the mass fraction of ROH is preferably in the range > 80% by weight, more preferably > 85% by weight, even more preferably >90% by weight (based on total mass of SAB or SAB and SBB). Thus, in particular, GRD1 is also an alcohol/water mixture in which the mass fraction of ROH is preferably in the range > 80% by weight, more preferably > 95% by weight, even more preferably > 90% by weight (based on total GRD1 mass).

4.5 Step (d) of the process according to the invention

[00169] In step (d) of the process according to the invention, the bottom stream SRDX1 is wholly or partially, preferably partially, passed to a second rectification column RD2. This provides a GRD2 mixture comprising water and ROH in the second RD2 rectification column.

[00170] In the embodiment of the present invention, in which the SRDX1 is partially passed to the RD2, this is especially realized so that a first portion SRDX1 of the background current SRDX1 discharged from the first rectification column RD1 is passed to a second column of rectification RD2 and a second portion SRDX12 of the background stream SRDX1 discharged from the first rectification column RD1 is recycled to the first rectification column RD1. It is even more preferable when energy is transferred to SRDX12, even more preferable when SRDX12 is heated. Once SRDX12 has been recycled to RD1, it undergoes mixing in RD1 with GRD1 and thus provides energy to separate GRD1 according to step (c).

[00171] In this preferred embodiment of step (d) of the process according to the invention, it is even more preferable when the ratio of masses (in kg) of SRDX1 to SRDX12 is in the range of 9:1 to 1:9, even more than preferably 4:1 to 1:4, even more preferably 7:3 to 3:7, even more preferably 3:2 to 2:3, even more preferably 1:1.

[00172] In this preferred embodiment of step (d) of the process according to the invention, it is possible to supply energy to the SRDX12 stream. In a preferred embodiment, this is accomplished when the SRDX12 stream is passed through a bottom evaporator VSRD1 in which energy is transferred from SRDB2 or other heat transfer medium to SRDX12. This energy transfer can advantageously be accomplished when SRDs12 and SRDB2/SRDS12 and the heat transfer medium are passed through a bottom evaporator VSRD1. After recycling SRDs12 into the RRA reaction column SRDs12 then transfers energy to GRD1.

[00173] Any desired rectification column known to those skilled in the art can be used as the RD2 rectification column in step (d) of the process according to the invention. The RD2 grinding column preferably contains internal components. Suitable inner components are, for example, plates, unstructured fillings or structured fillings. As dishes, bell dishes, sieve dishes, valve dishes, tunnel dishes or slit dishes are usually used. Unstructured packings are usually beds of random packing elements. Commonly used random filling elements are Raschig rings, Pall rings, Berl saddles or Intalox® saddles. Structured fillings are, for example, marketed under the trade name Mellapack® by Sulzer. In addition to the mentioned internal components, other suitable internal components are known to a person skilled in the art and can also be used.

[00174] Preferred internal components have a low specific pressure drop per theoretical plate. Structured fillings and random filling elements have, for example, a significantly lower pressure drop per theoretical plate than plates. This has the advantage that the pressure drop in the RD2 rectification column remains as low as possible and thus the mechanical power of the compressor and the temperature of the alcohol/water mixture GRD2 to be evaporated remain low.

[00175] When the RD2 rectification column contains structured or unstructured packing, these can be divided or in the form of uninterrupted packing. However, typically at least two fillers are provided, a filler above the feedpoint of the current SRDX1/the portion of SRDX1, in particular SRDX12, and a filler below the relevant feedpoint. If an unstructured filling is used, for example a random filling, the random filling elements are typically arranged in a suitable sieve dish or mesh dish.

[00176] SRDs1/the portion of SRDs1 that is passed to RD2 and which is preferably SRDs12 is at least partially liquid.

[00177] It is therefore even preferable to pass this current to RD2 through a liquid compressor or a pump P, since, according to the invention, RD2 is at the highest pressure (p2 > p1; p2 > p3A; p2 > p3B).

[00178] At the end of step (d) of the process according to the invention, a GRD2 mixture comprising water and ROH is finally obtained in the RD2 rectification column. The composition of the GRD2 mixture results especially from the composition of the SRDX1 stream/the portion of the SRDX1 stream, preferably SRDX12, which is passed to RD2.

4.6 Step (e) of the process according to the invention

[00179] In step (e) of the process according to the invention, the GRD2 mixture comprising water and ROH is at a pressure p2 and a temperature T2 separated into a steam stream comprising ROH SRDB2 at the top of RD2 and a bottom stream SRDS2 comprising water and optionally ROH at the bottom of RD2.

[00180] With the exception of the condition that p2 > p1, the pressure p2 in RD2 can be chosen by those skilled in the art according to their knowledge of the technique. It is preferably in the range between 1 bar (100 kPa) and 20 bar (2 MPa), preferably 1 bar (100 kPa) and 15 bar (1.5 MPa), more preferably 1 to 10 bar (100 kPa to 1 MPa), even more preferably 3.00 to 9.00 bar (300 kPa to 900 kPa), even more preferably 3.20 to 8.90 bar (320 kPa to 890 kPa), wherein, simultaneously, p2 > p1.

[00181] The T2 temperature in the RD2 can be chosen by those skilled in the art according to their knowledge of the art. It is preferably in the range from 40°C to 220°C, preferably from 60°C to 190°C.

[00182] The separation according to step (e) of the process according to the invention is a separation by distillation of the GRD2 alcohol/water mixture as is known to the person skilled in the art.

[00183] Obtained at the bottom of the RD2 rectification column is an SRDS2 stream that may comprise <1 wt% alcohol based on the total mass of SRDS2.

[00184] It is also obtained at the top of the RD2 rectification column the SRDB2 steam stream comprising ROH. The preferred mass fraction of ROH in this SRDB2 vapor stream is ≥ 99% by weight, preferably ≥ 99.6% by weight, most preferably ≥ 99.9% by weight, in each case based on the total mass of SRDB2 , where the remainder is mostly water.

[00185] In a preferred embodiment of the present invention, SRDB2 is at least partially employed as an SAE1 reagent stream in the RRA reactive rectification column and if step (a2) is carried out alternatively or additionally employed as an SBE1 reagent stream in the SBE1 column RRB reactive rectification.

[00186] In step (e) the SRDX1 stream, preferably the SRDX12 portion, completely or partially passed to the second rectification column RD2 in step (d) is subjected to separation by distillation.

4.7 Pressure management as a distinctive feature

[00187] The process according to the invention is characterized in that, during the operation of the rectification columns RD1 (step (c)) and RD2 (step (e)), a certain pressure ratio is established.

[00188] Thus, p2 > p1, p2 > p3A and in cases where step (a2) is performed p2 > p3B.

[00189] It was surprisingly found that maintaining these pressures allows minimizing the need for electrical energy supplied externally and most of the energy required for the process to be covered by heating steam.

[00190] It is even more advantageous when additionally the pressures are set such that p3A > p1 and in cases where step (a2) is performed additionally p3B > p1. Setting the pressures p3A and p3B in such a way reduces the total required energy demand compared to the case where p3A < p1/p3B < p1.

4.8 Characterization step (f): Energy transfer from SRDB2 to GRD1

[00191] Step (f) of the process according to the invention which characterizes in addition to the pressure regime is that energy is transferred from SRDB2 to the GRD1 mixture in the first rectification column RD1. According to the invention, "energy transfer" is to be understood in particular as meaning "heat transfer".

[00192] This step (f) and the pressure regime according to the invention allow a particularly advantageous integration of energy that would otherwise dissipate, which allows covering a particularly large portion of the energy demand of the process through the use of Low energy heating steam instead of electric current. This makes the process according to the invention particularly energy-efficient.

[00193] According to the invention, the transfer of energy from SRDB2 to GRD1 in RD2 can be carried out in various ways familiar to those skilled in the art and preferably comprises heating GRD1 in RD21 with SRDB2, for example, through an exchanger of heat WT.

[00194] According to the invention in step (f) especially energy is transferred from SRDB2 to GRD1 in RD1 directly or indirectly, preferably directly.

4.8.1 Direct power transfer from SRDB2 to GRD1 on RD1

[00195] According to the invention, "direct energy transfer from SRDB2 to GRD1 in RD1" means that an energy transfer, preferably heating, from GRD1 in RD1 with SRDB2 is carried out so that GRD1 is contacted with SRDB2 without GRD1 undergoes mixing with SRDB2, thus transferring energy from SRDB2 to GRD1. However, according to the invention, cases of direct energy transfer are to be understood to also include cases where an energy transfer, preferably heating, of an unloaded stream SX from RD1 with SRDB2 is effected without SRDB2 undergoing mixing with SX , thus transferring energy from SRDB2 to SX, and SX is then passed back to RD1 where it undergoes mixing with GRD1 in RD1 and thus transfers the absorbed energy from SRDB2 to GRD1 in RD1.

[00196] In a particular embodiment of the present invention, SX is selected from the group consisting of SRDS12, SRDX1.

[00197] Contact without mixing is obtained by methods known to those skilled in the art, for example, by contacting through a dividing wall made of metal, plastic, etc., in particular in the WT heat exchanger, preferably a K-condenser or V evaporator which is in particular selected among VS bottom evaporators and VZ intermediate evaporators.

[00198] According to the invention it is preferable when the direct transfer of energy from the SRDB2 to the GRD1 mixture in the second rectification column RD1 is carried out according to at least one of the steps (α-i), (α-ii), (α-iii), more preferably carried out according to at least one of steps (α-i), (α-ii).

[00199] (α-i) A first portion SRDS11 of the background current SRDS1 discharged from RD1 is passed to the second rectification column RD2, and energy is transferred from SRDB2 to a second portion SRDS12 of the background current SRDS1 discharged from RD1 , preferably via a WT heat exchanger, and SRDS12 is then recycled into RD1. This step (αi) also comprises embodiments in which energy is initially transferred from SRDB2, preferably via a WT heat exchanger, to the total background flow SRDS1, and the background flow SRDS1 is only then divided into SRDS11 and SRDS12 , and SRDS11 is then passed to RD2 and SRDS12 is recycled to RD1.

[00200] (α-ii) At least one stream SRDX1 distinct from SRDB1 and SRDS1 comprising ROH and water is discharged from RD1, energy is then transferred from SRDB2 to SRDX1, preferably via a WT heat exchanger, and SRDX1 is recycled in RD1.

[00201] It is preferred when SRDX1 is withdrawn below the SRDB1 steam stream in RD1. SRDX1 is then specially selected from undercurrent SRDX1S, intermediate current SRDX1Z.

[00202] An undercurrent SRDX1S is a current whose withdrawal point RD1 is at or below the withdrawal point of SRDS1. The SRDX1S can then be passed through a WT heat exchanger, in particular a VS bottom evaporator, and energy can be transferred therein from the SRDB2 to the SRDX1S.

[00203] An intermediate chain SRDX1Z is a chain whose withdrawal point on RD1 is between the withdrawal points of SRDB1 and SRDS1. SRDX1Z can then be discharged from RD1 and passed through a WT heat exchanger, in particular a VZ intermediate evaporator, and the energy transferred from SRDB2 to SRDX1Z therein.

[00204] (α-iii) SRDB2 is passed through the RD1, thus transferring energy from SRDB2 to GRD1, preferably through a WT heat exchanger. Such an embodiment can be realized, for example, when SRDB2 is passed through the rectification column RD1 through a conduit whose surface SRDB2 transfers energy to GRD1 in RD1.

4.8.2 Indirect energy transfer from SRDB2 to GRD1 in RD1

[00205] According to the invention, "indirect energy transfer from SRDB2 to GRD1 in RD1" should be understood to mean that an energy transfer, preferably heating, from GRD1 with SRDB2 is effected in RD1 so that GRD1 is not directly contacted with SRDB2, but at least one additional heat transfer medium W1, preferably precisely an additional one distinct from GRD1 and SRDB2 is employed, which during energy transfer from SRDB2 to GRD1 in RD1 does not undergo mixing with SRDB2 nor with GRD1 on RD1. Energy is transferred from SRDB2 to at least one heat transfer medium W1 without SRDB2 and the at least one heat transfer medium W1 passing through mixing and then transferred from the at least one heat transfer medium W1 to GRD1 in RD1 without the at least one heat transfer medium W1 and GRD1 undergoing mixing.

[00206] According to the invention, cases of indirect energy transfer should also be understood to include cases where energy is transferred from SRDB2 to at least one, preferably precisely one, heat transfer medium W1 without SRDB2 and the at least one heat exchanger W1 undergoing mixing and subsequently an energy transfer, preferably heating, of a stream SX discharged from RD1 with the at least one heat transfer means W1 is effected without the at least one heat transfer means heat transfer medium W1 is mixed with SX, thereby transferring energy from the at least one heat transfer medium W1 to SX, and SX is then recycled into RD1 where it undergoes mixing with GRD1 in RD1 and thereby transfers the energy absorbed by SRDB2 through of at least one heat transfer medium W1 to GRD1 in RD1.

[00207] In a particular embodiment of the present invention, SX is selected from the group consisting of SRDS22, SRDX1.

[00208] "At least one heat transfer medium W1" comprises cases where energy from W1 is first transferred to one or more additional heat transfer means W2, W3, W4, W5, etc. distinct from GRD1 and SRDB2 and the latter of these heat transfer means, referred to as "WY" is contacted with GRD1 in RD1, thereby transferring energy, preferably heat, from WY to GRD1, but without WY and GRD1 undergoing mixing. Energy, preferably heat, can also be transferred from WY to a stream SX discharged from RD1 without WY and SX is mixed and SX is subsequently recycled into RD1 where it is mixed with GRD1 in RD1, thus transferring the energy absorbed by WY to GRD1 in RD21.

[00209] The contact described is in each case preferably carried out on a WT heat exchanger, preferably a K condenser or V evaporator, which is specially selected from VS bottom evaporators and VZ intermediate evaporators.

[00210] According to the invention, it is preferable when the indirect transfer of energy from the SRDB2 to the GRD1 mixture in the second rectification column RD1 is carried out according to at least one of the steps (β-i), (β-ii), (β-iii), more preferably according to at least one of steps (β-i), (β-ii).

[00211] (β-i) a first portion SRDS11 of the background stream SRDS1 discharged from RD1 is passed to the second rectification column RD2, and a second portion SRDS12 of the background stream SRDS1 discharged from RD1 is recycled into RD1. Energy is transferred from SRDB2 to at least one heat transfer medium Wi1 other than SRDS12 and then transferred from at least one heat transfer medium Wi1 to SRDS12 and SRDS22 is then recycled in RD1. This step (β-i) also comprises embodiments in which energy is initially transferred from at least one, preferably precisely one, heat transfer medium Wi1 other than SRDS12, preferably via a heat exchanger WT, to the current total SRDS1 background and the SRDS12 portion is then separated from the SRDS1 background stream, and subsequently the SRDS12 is recycled into RD1.

[00212] (β-ii) at least one SRDX1 stream distinct from SRDB1 and SRDS1 comprising ROH and water is discharged from RD1. Energy is transferred from the SRDB2 to at least one, preferably precisely one, Wii1 heat transfer medium other than SRDX2, preferably via a WT heat exchanger, and then transferred from the at least one Wii1 heat transfer medium to SRDX1 and SRDX1 is then recycled into RD1.

[00213] It is preferred when the SRDX1 is withdrawn below the SRDB1 steam stream on the RD1. SRDX1 is then specially selected from undercurrent SRDX1S, intermediate current SRDX1Z.

[00214] An undercurrent SRDX1S is a current whose withdrawal point on RD1 is at or below the withdrawal point of SRDS1. The SRDX1S can then be passed through a WT heat exchanger, in particular a VS bottom evaporator, and the energy transferred therein from the SRDB2 to the SRDX1S.

[00215] An intermediate chain SRDX1Z is a chain whose withdrawal point on RD1 is between the withdrawal points of SRDB1 and SRDS1. SRDX1Z can then be discharged from RD1 and passed through a WT heat exchanger, in particular a VZ intermediate evaporator, and the energy transferred from SRDB2 to SRDX1Z therein.

[00216] (β-iii) energy is transferred from SRDB2 to at least one Wii1 heat transfer medium other than GRD1 and the at least one Wii1 heat transfer medium is then passed through RD1, thereby transferring energy of at least least one means of Wii1 heat transfer to GRD1. Such an embodiment can be realized, for example, when at least one heat transfer medium Wii1 is passed through the rectifying column RD1 through a conduit whose surface transfers energy from the at least one heat transfer medium Wii1 to GRD1 in RD1.

[00217] Usable heat transfer medium W1 W2, Wi1/at least one heat transfer medium Wii1/at least one heat transfer medium Wii1 include any heat transfer medium known to those skilled in the art. Such heat transfer media are preferably selected from the group consisting of water; alcohol-water solutions; brine solutions, also including ionic liquids, such as, for example, LiBr solutions, dialkylimidazolium salts such as especially dialkylimidazolium dialkylphosphates; mineral oils, for example, such as diesel oils, thermal oils, such as, for example, silicone oils; biological oils, such as, for example, limonene; aromatic hydrocarbons, such as, for example, dibenzyltoluene. The most preferred heat transfer medium is water.

[00218] Salt water solutions that can be used are also described, for example, in DE 10 2005 028 451 A1 and WO 2006/134015 A1.

4.9 Addition of fresh alcohol

[00219] ROH alcohol is consumed in the process according to the invention and, especially in a continuous process mode, requires replacement with fresh ROH alcohol.

[00220] Fresh alcohol is, in particular, added to at least one of the selected columns of the RD1 rectification column, RD2 rectification column, RRA reactive rectification column and if step (a2) is carried out alternatively or additionally added to the column of reactive rectification RRB.

[00221] In a preferred embodiment of the present invention, an SXE1 stream other than SAE1 and SBE1 comprising ROH is correspondingly added to at least one of the selected columns of the RD1 rectification column, RD2 rectification column, RRA reactive rectification column and if the step (a2) is carried out alternatively or additionally added to the RRB reactive rectification column.

[00222] The supply of fresh alcohol ROH is especially carried out, directly as a stream of SAE1 reagent comprising ROH on the RRA reaction column or, in the embodiments in which step (a2) is carried out, on the RRA and RRB reaction columns.

[00223] In the process according to the invention it is additionally preferable to employ the vapor stream comprising ROH SRDB1 at least partially as SAE1 reagent stream in step (a1) and optionally as SBE1 reagent stream in step (a2). The SRDB2 vapor stream can alternatively or additionally be employed at least partially as the SAE1 reagent stream in step (a1) and optionally as the SBE1 reagent stream in step (a2).

[00224] In the particularly preferred embodiment in which SRDB1 and SRDB2 are employed at least partially as reagent stream SAE1 in step (a1) and optionally as reagent stream SBE1 in step (a2), SRDB1 and SRDB2 can be supplied to the respective column of RRA/RRB reactive rectification separately from each other or first mixed together and then supplied to the respective RRA/RRB reactive rectification column. SRDB1 and SRDB2 are preferably first mixed together and then fed to the respective RRA/RRB reactive rectification column.

[00225] In this preferred embodiment, it is even more preferable when fresh ROH alcohol is added to one of the rectification columns RD1, RD2, preferably RD1.

[00226] When fresh ROH alcohol is added to the RD1 or RD2 rectification column, it is preferably supplied in the rectification section of the respective rectification column or directly on top of the respective rectification column. The ideal feed point depends on the water content of the fresh alcohol used and also on the desired residual water content in the SRDB1/SRDB2 steam stream. The greater the proportion of water in alcohol employed and the greater the purity requirements in the SRDB1/SRDB2 steam stream, the more advantageous it is to feed a number of theoretical plates below the top of the RD1/RD2 rectification column. Up to 20 theoretical plates below the top of the RD1/RD2 rectification column are preferred, and in particular 1 to 5 theoretical plates.

[00227] When fresh ROH alcohol is added to the rectification column RD1/RD2 it is added to the top of the rectification column RD1/RD2 at temperatures up to the boiling point, preferably at room temperature. The fresh alcohol can have a dedicated feed supplied to it or else when a portion of the alcohol withdrawn at the top of the RD1/RD2 rectification column is recycled it can be mixed with it after condensation and supplied to the RD1/RD2 rectification column in set. In this case it is particularly preferable when fresh alcohol is added to a condensate vessel in which condensed alcohol from the SRDB1/SRDB2 vapor stream is collected.

5. Examples 5.1 Example 1 (not of the invention)

[00228] The configuration according to example 1 corresponds to the interconnection of two columns according to figure 1, where p1 > p3A > p2.

[00229] An SAE2 <3A02> stream of aqueous NaOH (50% by weight) of 5 t/h is supplied to the top of an RRA <3A> reaction column at 25°C. A stream of SAE1 <3A01> methanol steam of 70.2 t/h is supplied countercurrent above the bottom of the RRA <3A> reaction column. The RRA <3A> reaction column is operated at a p3A pressure of 1.6 bar (160 kPa). At the bottom of the RRA column <3A> a product stream with virtually no water SAP* <3A08> of 10.8 t/h (30% by weight sodium methoxide in methanol) is withdrawn. In the VS3A evaporator <3A06> of the RRA reaction column <3A> about 0.7 MW of heating power is introduced using heating steam. A stream of methanol-water vapor SAB <3A03> is drawn off the top of the RRA reaction column <3A>. A portion of this stream is recycled through a KRRA condenser <3A05> to the RRA reaction column <3A>, and the remaining portion (64.4 t/h) compressed in a VD31 compressor <10> at 7.1 bar ( 710 kPa), where about 4 MW of compressor power is required and supplied to a first rectification column RD1 <1>. The RD1 rectification column <1> is operated at p1 = ~ 7 bar (700 kPa). At the top of the RD1 rectification column <1> a fresh liquid methanol stream of 9.5 t/h is supplied (not shown in figure 1) and the methanol vapor stream SRDB1 <101> is withdrawn. A portion of SRDB1 <101> is recycled through capacitor KRD1 <102> into column RD1 <1>. The remaining portion of SRDB1 <101> (42.9 t/h) is fed to the RRA <3A> reaction column. The condenser KRD1 <102> of column RD1 <1> which is simultaneously the evaporator VSRD2 of the second rectification column RD2 <2> provides the heating power for column RD2 <2>. The modality according to example 1 used direct contact where the condenser KRD1 <102> is used simultaneously as a bottom evaporator VSRD2 <204>.

[00230] A liquid stream of a water-methanol mixture SRDX1 <103> is discharged at the bottom of the rectification column RD1 <1>, of which a portion SRDX12 <104> of 30.9 t/h is passed to the column of RD2 rectification <2> and the remaining portion of the SRDX1 <103> stream is recycled as SRDX1 <105> into RD1 <1>. In the evaporator VSRD1 <106> of the rectification column RD1 <1> about 5.4 MW of heating power is introduced via heating steam.

[00231] The RD2 rectification column <2> is operated at a p2 pressure of 1.1 bar (110 kPa). A methanol steam stream SRDB2 <201> is withdrawn at the top of the RD2 <2> rectification column. A portion of SRDB2<201> is recycled through condenser KRD2<203> into column RD2<2>. The remaining portion of SRDB2 <201> (27.3 t/hr) is fed to the RRA <3A> reaction column. This portion of the SRDB2 <201> steam stream is compressed to 2 bar (200 kPa) in a VD23 <13> compressor, where about 0.6 MW of compressor power is required. At the bottom of the RD2 <2> rectification column is discharged a liquid stream of SRDS2 <202> water (contaminated with 500 wt. ppm methanol) of 3.7 t/h. For evaporation in rectification column RD2 <2> (since direct heat integration is performed, the function of bottom evaporator VSRD2 <204> shown in figure 1 is co-assumed by condenser KRD1 <102>) about 14, 8 MW of heating power is introduced through heat integration with the RD1 column <1>.

[00232] The respective non-recycled portions of methanol vapor streams SRDB1 <101> and SRDB2 <201> taken from the tops of RD1 <1> and RD2 <2> are mixed and recycled to the bottom of the RRA reaction column <3A >.

[00233] Altogether, in this example, about 6.1 MW of heating power is required through heating steam and about 4.6 MW of electrical power (compressor power) and must be supplied externally.

5.2 Example 2 (not of the invention)

[00234] The configuration according to example 2 corresponds to the interconnection of two columns according to figure 2, where p1 > p2 > p3A.

[00235] A SAE2 <3A02> stream of aqueous NaOH (50% by weight) of 5 t/h is supplied to the top of an RRA <3A> reaction column at 25°C. A stream of SAE1 <3A01> methanol steam of 70.2 t/h is supplied countercurrent above the bottom of the RRA <3A> reaction column.

[00236] The RRA <3A> reaction column is operated at a p3A pressure of 1.1 bar (110 kPa). At the bottom of the RRA column <3A> a product stream with virtually no water SAP* <3A08> of 10.8 t/h (30% by weight sodium methoxide in methanol) is withdrawn. In the VS3A evaporator <3A06> of the RRA reaction column <3A> about 8 MW of heating power is introduced using heating steam. A stream of methanol-water vapor SAB <3A03> is drawn off the top of the RRA reaction column <3A>. A portion of this stream is recycled through a KRRA condenser <3A05> to the RRA reaction column <3A> and the remaining portion (64.4 t/h) compressed in a VD31 compressor <10> at 9 bar (900 kPa) , where about 5.8 MW of compressor power is required and supplied to a first rectification column RD1 <1>. The RD1 rectification column <1> is operated at p1 = ~ 8.9 bar (890 kPa). At the top of the RD1 rectification column <1> a fresh liquid methanol stream of 9.5 t/h is supplied (not shown in figure 2) and the methanol vapor stream SRDB1 <101> is withdrawn. A portion of SRDB1 <101> is recycled through capacitor KRD1 <102> into column RD1 <1>. The remaining portion of SRDB1 <101> (42.9 t/h) is fed to the RRA <3A> reaction column. The condenser KRD1 <102> of column RD1 <1> which is simultaneously the evaporator VSRD2 <204> of the second rectification column RD2 <2> provides the heating power for column RD2 <2>. The embodiment according to example 2 used direct contact where the condenser KRD1 <102> is used simultaneously as a bottom evaporator VSRD2 <204>.

[00237] A liquid stream of a water-methanol mixture SRDX1 <103> is discharged at the bottom of the rectification column RD1 <1>, of which a portion SRDX12 <104> of 31.9 t/h is passed to the column of RD2 rectification <2> and the remaining portion of the SRDX1 <103> stream is recycled as SRDX1 <105> into RD1 <1>. In the evaporator VSRD1 <106> of the rectification column RD1 <1> about 5.2 MW of heating power is introduced via heating steam.

[00238] The RD2 rectification column <2> is operated at a p2 pressure of 1.5 bar (150 kPa). A methanol steam stream SRDB2 <201> is withdrawn at the top of the RD2 <2> rectification column. A portion of SRDB2 <201> is recycled through condenser KRD2 <203> into column RD2 <2>. The remaining portion of SRDB2<201> (28.2 t/hr) is fed to the RRA <3A> reaction column. At the bottom of the RD2 <2> rectification column is discharged a liquid stream of SRDS2 <202> water (contaminated with 500 wt. ppm methanol) of 3.7 t/h. For evaporation in rectification column RD2 <2> (since direct heat integration is performed, the function of bottom evaporator VSRD2 <204> shown in figure 1 is co-assumed by condenser KRD1 <102>) about 15.9 MW of heating power are introduced through heat integration with column RD1 <1>.

[00239] The respective non-recycled portions of methanol vapor streams SRDB1 <101> and SRDB2 <201> taken from the tops of RD1 <1> and RD2 <2> are mixed and recycled to the bottom of the RRA reaction column <3A >.

[00240] Altogether, in this example, about 6.0 MW of heating power is required through heating steam and about 5.8 MW of electrical power (compressor power) and must be supplied externally.

5.3 Example 3 (not of the invention)

[00241] The configuration according to example 3 corresponds to the interconnection of two columns according to figure 3, where p2 > p1 > p3A. Intermediate evaporator VZRD1 <107> with stream SRDX1 <112> withdrawn at withdrawal point <111> shown in figure 3 is also omitted in the configuration according to example 3. Condenser KRD2 <203> is also simultaneously the evaporator of background VSRD1 <106>. Fresh methanol stream SXE1 <205> is given in figure 3 for rectifying column RD2 <2> but in configuration according to example 3 given for RD1 <1>.

[00242] An SAE2 <3A02> stream of aqueous NaOH (50% by weight) of 5 t/h is supplied to the top of an RRA <3A> reaction column at 25°C. A stream of SAE1 <3A01> methanol steam of 70.2 t/h is supplied countercurrent above the bottom of the RRA <3A> reaction column. The RRA <3A> reaction column is operated at a p3A pressure of 1.1 bar (110 kPa). At the bottom of the RRA column <3A> a product stream with virtually no water SAP* <3A08> of 10.8 t/h (30% by weight sodium methoxide in methanol) is withdrawn. In the VS3A evaporator <3A06> of the RRA reaction column <3A> about 1.4 MW of heating power is introduced using heating steam. A stream of methanol-water vapor SAB <3A03> is drawn off the top of the RRA reaction column <3A>. A portion of this stream is recycled through a KRRA condenser <3A05> to the RRA reaction column <3A> and the remaining portion (64.4 t/h) compressed in a VD31 compressor <10> at 1.7 bar (170 kPa), where about 1.1 MW of compressor power is required and supplied to a first rectification column RD1 <1>. The RD1 <1> rectification column is operated at p1 = ~ 1.5 bar (150 kPa). At the top of the RD1 rectification column <1> is supplied a fresh liquid methanol stream SXE1 <205> of 9.5 t/h (shown at the top of the RD2 rectification column <2> in figure 3) and a methanol stream in steam SRDB1 < 101> is removed. A portion of SRDB1 <101> is recycled through capacitor KRD1 <102> into column RD1 <1>. The remaining portion of SRDB1 <101> (56.8 t/h) is fed to the RRA <3A> reaction column. The embodiment according to example 3 used direct contact where the condenser KRD2 <203> simultaneously serves as a bottom evaporator VSRD1 <106>.

[00243] A liquid stream of a water-methanol mixture SRDX1 <103> is discharged at the bottom of the RD1 rectification column <1>, of which a 17 t/h SRDX12 <104> portion is passed to the RD2 rectification column <2> and the remaining portion of the SRDX1 stream <103> is recycled as SRDX1 <105> into RD1 <1>.

[00244] The discharged stream pressure SRDX12 <104> is increased in a P pump <15> to 9 bar (900 kPa) and the stream SRDX12 <104> supplied to the second rectification column RD2 <2>. The RD2 <2> rectification column is operated at a p2 pressure of 8.9 bar (890 kPa). In the condenser KRD2 <203> of column RD2<2> which is simultaneously the evaporator of column RD1 <1>, approximately 8.2 MW of heating power is supplied to column RD1 <1>. A methanol steam stream SRDB2 <201> is withdrawn at the top of the RD2 <2> rectification column. A portion of SRDB2 <201> is recycled through condenser KRD2 <203> into column RD2 <2>. The remaining portion of SRDB2<201> (13.4 t/hr) is fed to the RRA <3A> reaction column. A liquid stream of water (contaminated with 500 ppm by weight of methanol) of 3.7 t/h is discharged to the bottom of the RD2 <2> rectification column. In the VSRD2 evaporator <204> of the RD2 rectification column <2> about 12.9 MW of heating power is introduced using heating steam.

[00245] The respective non-recycled portions of the steam methanol streams SRDB1 <101> and SRDB2 <201> taken from the tops of RD1 <1> and RD2 <2> are mixed, decompressed and recycled to the bottom of the RRA reaction column <3A>.

[00246] Altogether, in this example, about 14.3 MW of heating power is required through heating steam and about 1.1 MW of electrical power (compressor power) and must be supplied externally.

[00247] Compared to the modality according to the non-inventive example 1, this variant saves about 75% of the required compressor power to be supplied externally (electricity).

5.4 Example 4 (of the invention)

[00248] The configuration according to example 4 corresponds to the interconnection of two columns according to figure 4, where p2 > p3A > p1. Intermediate evaporator VZRD1 <107> with stream SRDX1 <112> withdrawn at withdrawal point <111> shown in figure 4 is also omitted in the configuration according to example 4. Condenser KRD2 <203> is also simultaneously the evaporator of background VSRD1 <106>. The fresh methanol stream SXE1 <205> is given in figure 4 for the rectification column RD2 <2> but in the configuration according to example 4 given for RD1 <1>.

[00249] A SAE2 <3A02> stream of aqueous NaOH (50% by weight) of 5 t/h is supplied to the top of an RRA <3A> reaction column at 25°C. A stream of SAE1 <3A01> methanol steam of 70.2 t/h is supplied countercurrent above the bottom of the RRA <3A> reaction column. The RRA <3A> reaction column is operated at a p3A pressure of 1.6 bar (160 kPa). At the bottom of the RRA column <3A> a product stream with virtually no water SAP* <3A08> of 10.8 t/h (30% by weight sodium methoxide in methanol) is withdrawn. In the VS3A evaporator <3A06> of the RRA reaction column <3A> about 0.8 MW of heating power is introduced using heating steam. A stream of methanol-water vapor SAB <3A03> is drawn off the top of the RRA reaction column <3A>. A portion of this stream is recycled through a KRRA condenser <3A05> to the RRA reaction column <3A> and the remaining portion (64.4 t/h) is supplied to a first rectification column RD1 <1>. The RD1 rectification column <1> is operated at p1 = ~ 1.1 bar (110 kPa). At the top of the RD1 rectification column <1> is supplied a fresh liquid methanol stream SXE1 <205> of 9.5 t/h (shown at the top of the RD2 rectification column <2> in figure 4) and a methanol stream in steam SRDB1 < 101> is removed.

[00250] A portion of the SRDB1 <101> is recycled through the KRD1 condenser <102> into column RD1 <1>. The remaining portion of SRDB1 <101> (55 t/h) is compressed to 2 bar (200 kPa) in a VD13 <16> compressor, where about 1.2 MW of compressor power is required, and supplied to the RRA reaction <3A>. Discharged at the bottom of the RD1 rectification column <1> is a liquid stream of a water-methanol mixture SRDX1 <103> of which an 18.9 t/h SRDX12 <104> portion is passed to the RD2 rectification column <2> and the remaining portion of the SRDX1 stream <103> is recycled as SRDX1 <105> into RD1 <1>.

[00251] The discharged stream pressure SRDX12 <104> is increased in a P pump <15> to 3.4 bar (340 kPa) and the stream supplied to the second rectification column RD2 <2>. The RD2 <2> rectification column is operated at a p2 pressure of 3.2 bar (320 kPa). In the condenser KRD2 <203> of column RD2<2> which is simultaneously the evaporator of column RD1 <1>, about 6.3 MW of heating power is supplied to column RD1 <1>. Drawn off at the top of the RD2 <2> rectification column is a methanol steam stream SRDB2 <201>. A portion of SRDB2 <201> is recycled through condenser KRD2 <203> into column RD2 <2>. The remaining portion of SRDB2<201> (15.2 t/hr) is fed to the RRA <3A> reaction column. A liquid stream of water (contaminated with 500 ppm by weight of methanol) of 3.7 t/h is discharged to the bottom of the RD2 <2> rectification column. In the VSRD2 evaporator <204> of the RD2 rectification column <2> about 11.4 MW of heating power is introduced using heating steam.

[00252] The respective non-recycled portions of the steam methanol streams SRDB1 <101> and SRDB2 <201> taken from the tops of RD1 <1> and RD2 <2> are mixed and recycled to the bottom of the RRA reaction column <3A >.

[00253] Altogether, in this example, about 12.2 MW of heating power is required through heating steam and about 1.2 MW of electrical power (compressor power) and must be supplied externally. Compared to the embodiment according to the non-inventive example 2, this variant saves about 79% of the necessary compressor power to be supplied externally (electrical energy).

5.5 Result

[00254] Comparison of the proportion of heating steam and electric current necessary to cover the energy demand in the examples of the invention and not of the invention reveals that the process of the invention surprisingly makes it possible to cover a large proportion of the energy demand by means of steam of heating and to minimize the proportion of the energy to be supplied by electrical energy.

Claims (15)

Process for producing at least one alkali metal alkoxide of formula MAOR, wherein R is a C1 to C6 hydrocarbon radical and wherein MA is selected from sodium, potassium, wherein: (a1) an SAE1 reagent stream comprising ROH is reacted with an SAE2 reagent stream comprising MAOH countercurrently at a pressure p3A and a temperature T3A on an RRA reactive rectification column to provide an RPA crude product comprising MAOR, water, ROH, MAOH, wherein a bottom product stream SAP comprising ROH and MAOR is withdrawn at the bottom end of RRA and a SAB vapor stream comprising water and ROH is withdrawn at the top end of RRA, (a2) and optionally, simultaneously and spatially separated from step (a1), a reagent stream SBE1 comprising ROH is reacted with a stream of reagent SBE2 comprising MBOH in countercurrent at a pressure p3B and a temperature T3B on an RRB reactive rectification column to obtain a crude product RPB comprising MBOR, water, ROH, MBOH, wherein MB is selected from sodium, potassium, wherein an SBP bottoms product stream comprising ROH and MBOR is withdrawn at the bottom end of RRB and an SBB vapor stream comprising water and ROH is withdrawn at the top end of RRB, (b) the vapor stream SAB and if step (a2) is carried out, the steam stream SBB in mixture with SAB or separately from SAB is passed to a first rectification column RD1, to obtain a GRD1 mixture comprising water and ROH in the first rectification column RD1, (c) the GRD1 mixture is in the first rectification column RD1 at a pressure p1 and a temperature T1 separated into a steam stream comprising ROH SRDB1 at the top end of RD1 and a bottom stream SRDX1 comprising water and ROH at the bottom end of RD1, (d) the bottom stream SRDX1 is wholly or partially passed to a second rectification column RD2, to obtain a GRD2 mixture comprising water and ROH in the second rectification column RD2, (e) the GRD2 mixture is at a pressure p2 and a temperature T2 separated into a steam stream comprising ROH SRDB2 at the top of RD2 and a bottom stream SRDS2 comprising water at the lower end of RD2, characterized by the fact that p2 > p1, p2 > p3A, and in cases where the step (a2) is performed p2 > p3B, and in which (f) energy from SRDB2 is transferred to the GRD1 mixture in the first rectification column RD1. Process, according to claim 1, characterized by the fact that in step (f) the energy is transferred directly from SRDB2 to GRD1. Process, according to claim 2, characterized by the fact that at least one of the steps (αi), (α-ii), (α-iii) is carried out: (α-i) a first portion SRDS11 of the background stream SRDS1 discharged from RD1 is passed to the second rectification column RD2 and energy is transferred from SRDB2 to a second portion SRDS12 of the background current SRDS1 discharged from RD1 and SRDS12 is then recycled into RD1; (α-ii) at least one SRDX1 stream distinct from SRDB1 and SRDS1 comprising ROH and water is discharged from RD1, energy is then transferred from SRDB2 to SRDX1 and SRDX1 is recycled in RD1; (α-iii) SRDB2 is passed through RD2, thus transferring energy from SRDB1 to GRD2. Process, according to claim 1, characterized by the fact that in step (f) energy is transferred indirectly from SRDB2 to GRD1. Process, according to claim 4, characterized by the fact that at least one of the steps (βi), (β-ii), (β-iii) is carried out: (β-i) an SRDS11 portion of the SRDS1 background stream discharged from RD1 is passed to the second rectification column RD2, and a second portion SRDS12 of the background stream SRDS1 discharged from RD1 is recycled in RD1, wherein energy is transferred from SRDB2 to at least one distinct heat transfer medium Wi1 from SRDS12 and then transferred from at least one Wi1 heat transfer medium to SRDS12 and SRDS12 is then recycled into RD1; (β-ii) at least one SRDX1 stream other than SRDB1 and SRDS1 comprising ROH and water is discharged from RD2 and energy is transferred from SRDB2 to at least one heat transfer medium Wii1 other than SRDX1 and then transferred from at least one medium Wii1 heat transfer to SRDX1 and SRDX1 is then recycled into RD1; (β-iii) energy is transferred from SRDB2 to at least one Wii1 heat transfer medium other than GRD1 and the at least one Wii1 heat transfer medium is then passed through RD1, thereby transferring energy of at least a Wii1 heat transfer medium for GRD1. Process, according to claim 5, characterized by the fact that each of Wi1, Wii1, Wii1 is water. Process according to any one of claims 3, 5 and 6, characterized in that SRDX1 is withdrawn below the steam stream SRDB1 in RD1. Process according to any one of claims 1 to 7, characterized in that SRDB2 is at least partially used as a SAE1 reagent stream in the RRA reactive rectification column and if step (a2) is carried out alternatively or additionally used as a stream of SBE1 reagent on the RRB reactive rectification column Process according to any one of claims 1 to 8, characterized in that SRDB1 is at least partially used as a SAE1 reagent stream in the RRA reactive rectification column and if step (a2) is carried out alternatively or additionally used as a stream of SBE1 reagent on the RRB reactive rectification column. Process according to any one of claims 1 to 9, characterized in that an SXE1 stream other than SAE1 and SBE1 comprising ROH is added to at least one of the selected columns of rectification column RD1, rectification column RD2, column of RRA reactive rectification and whether step (a2) is carried out alternatively or additionally added to the RRB reactive rectification column. Process according to any one of claims 1 to 10, characterized in that R is methyl or ethyl. Process according to any one of claims 1 to 11, characterized in that step (a2) is carried out. Process according to any one of claims 1 to 12, characterized in that p3A > p1 and additionally in cases where step (a2) is performed p3B > p1. Process according to any one of claims 1 to 13, characterized in that the bottom stream SRDS2 comprises water and ROH. Process according to any one of claims 1 to 14, characterized in that it is carried out continuously.

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