EP3080067A1

EP3080067A1 - Tertiary alkylamines as methacrolein synthesis co-catalyst

Info

Publication number: EP3080067A1
Application number: EP14805929.8A
Authority: EP
Inventors: Rudolf Burghardt; Steffen Krill; Torsten Balduf; Eduard Rundal
Original assignee: Evonik Roehm GmbH
Current assignee: Roehm GmbH Darmstadt
Priority date: 2013-12-12
Filing date: 2014-12-03
Publication date: 2016-10-19
Also published as: KR20160098374A; CN105722814A; JP2017502943A; EP2883859A1; SG11201602880UA; US20160280624A1; TW201536732A; WO2015086386A1

Abstract

The invention relates to a method for preparing methacrolein from propionaldehyde and formalin. Said novel method is characterized in that the catalyst system used for the conversion is modified by the simultaneous presence of secondary and tertiary amines in such a way that the synthesis can be performed more efficiently and requires less effort in the purification stage.

Description

Tertiary alkylamines as cocatalyst in methacrolein synthesis

The present invention relates to an improved process for the preparation of methacrolein from propionaldehyde and formalin. This novel process is characterized in that the catalyst system used for this reaction is modified such that the synthesis is more efficient and less

Cleaning effort can be performed.

Methacrolein is used in chemical synthesis in particular as an intermediate for the production of methacrylic acid, methyl methacrylate or even active,

Odors or flavors used. There is a great interest in the simplest possible, economical and environmentally friendly production processes.

State of the art

The present invention relates to the modification of the large-scale process for the production of methacrolein, starting from propanal and

Formaldehyde or formalin. The reaction is via a Mannich reaction. Such a process for the preparation of methacrolein, is inter alia in the

DE 32 13 681, US 7,141, 702, US 4,408,079, JP 3069420,

JP 4173757, EP 0 317 909 and US 2,848,499. In this process, in the presence of dimethylamine and acetic acid as homogeneous catalysts at temperatures of about 160 to 180 ° C and a

Residence time of about 10 sec propionaldehyde reacted with formalin. The

Reaction mixture is separated by distillation. At the head of the column becomes one

Methacrolein-water obtained by heteroazeotrope. At the bottom of the column, an aqueous solution with the homogeneous catalysts, traces of methacrolein and high boilers is separated. Optionally, a part, for example about 50%, of the aqueous discharge can be recycled again. The catalytically active amines required for the reaction form under the

Reaction conditions according to Eschweiler-Clarke or in a Leukart-Wallach similar reaction higher alkylated derivatives, which are no longer catalytically active according to the prior art. For example, dimethylamine is formed by reaction with a formaldehyde equivalent of trimethylamine while releasing water. According to DE 32 13 681, this formed in the reaction of dimethylamine (DMA) trimethylamine (TMA) is catalytically inactive. In addition, US Pat. No. 4,408,079 states that trimethylamine reduces the selectivity of the reaction and therefore has to be separated off. In such a separation, however, an overall higher catalyst consumption is given in a continuous operation. Thus, the TMA can not be removed without simultaneous removal of DMA and both the excess DMA and TMA converted DMA must be renewed. Furthermore, this separation is carried out by distillation, whereby the separated with low-boiling methacrolein in a

consuming additional distillation stage must be recovered.

According to the state of the art, it is thus necessary when recycling the

Increase the addition of DMA to balance the loss of catalytic activity due to the formation of TMA.

task

In view of the prior art, it was therefore an object of the present invention to reduce the amount of amines used in the implementation of a continuously performed, aminatalytic reaction for the synthesis of methacrolein over the prior art.

In particular, it was an object to provide such a method in which less cleaning steps are needed and the amount of waste water can be reduced.

Other not explicitly mentioned tasks arise from the

Overall context of the following description and the claims.

solution

The inventive method is used to optimize the amine-containing

Components of the catalyst system one - preferably continuously

Mannich reaction in which propanal with formaldehyde too

Methacrolein is reacted.

These objects are achieved by a novel process in the propanal in the presence of 0.1 to 30 mol%, preferably 0.5 to 20 mol% organic base and 0.1 to 30 mol%, preferably 0.5 to 20 mol% acid , in each case based on propanal, at a temperature of 100 to 300 ° C and at a pressure of 5 to 100 bar continuously reacted with formaldehyde to methacrolein. The component formaldehyde is understood to be independent of the addition form and formalin or paraformaldehyde are included with this term in relation to the addition. The process according to the invention is characterized in particular in that the organic base is a mixture of a secondary alkylamine and a tertiary alkylamine in a substance ratio between 20: 1 and 1: 3, preferably between 10 to 1 and 1 to 2, more preferably between 7 to 1 and 1 to 1, and most preferably between 5 to 1 and 2.5 to 1.

In a first embodiment, the secondary and the tertiary alkyl amines of the plant, preferably directly to the reactor, are added as a mixture. The ratio of the two components is either as indicated or the proportion of tertiary alkyl amines at the entrance of the reaction is reduced compared to

Reactor outlet, as they are formed during the reaction itself.

In a preferred, alternative embodiment of the invention, only secondary alkylamines are added to the system. The tertiary alkylamines are formed during operation of the plant and accumulate in circulation. Particularly preferred in this embodiment, the content of tertiary

Alkylamines continuously or regularly determined, for example by sampling. On the basis of this determination, the amine-containing catalyst solution falls below the ratio of secondary to tertiary amine components below 1 to 3, preferably below 1 to 2 and particularly preferably below 1 to 1

renewed accordingly. This renewal is carried out by discharging the aqueous reaction phase and / or by adding fresh secondary alkylamine to

System, preferably directly into the reactor. For this purpose, the plant is designed such that the reaction mixture is continuously discharged from the reaction space and separated via a phase separator or preferably via a distillation column. In this case, the organic phase containing the methacrolein is recovered and removed, for example, as a distillate. The remaining aqueous

The distillation bottoms, including, inter alia, residues of the methacrolein, are recycled wholly or partly to the reaction space. At this point, parts of the aqueous phase can be removed to renew the catalyst components, in particular the amine components. The removal over one

Phase separator is analog. By taking this takes place not only the

Renewal of the catalyst components, but it will be the same time

Reduced amount of water and resulting by-products are discharged from the system. The supply of the reaction solution to be worked up from the reaction space into the distillation column can take place above, inside or below the separation section of the column. In the evaporator section of this column, a sump which predominantly consists of water of reaction or which contains quantities of water which enter the cycle process with the formalin solution collects. This sump additionally contains the catalyst components, such as, for example, the organic acid and the secondary and the tertiary amine or the salts formed therefrom, as well as by-products of the reaction or the combination of the two. This aqueous catalyst solution can preferably be withdrawn below the feed to the column at the bottom of the column. The present total water is made up of the water, which was added as a catalyst solution, in the

Reaction formed and optionally that from the formaldehyde solution together.

Further, but to a lesser extent to be considered sources of water are components of the technical starting materials such as propional and water, which is formed in various side reactions of the catalyst components with reactants, by-products and reaction products, and water of reaction of all these

Components that form under the reaction conditions.

In addition, it is possible to divide the sump effluent into two sub-streams so that a sub-stream just carries with it the amount of water which was formed during the reaction or was introduced with the starting materials. This partial stream is then discharged and the remaining portion returned to the reactor. The executed part would be disposed of thermally or biologically processed in this procedure, for example.

The aqueous phase of the reaction taken in this way continuously, semicontinuously or batchwise is then preferably removed, optionally separated via a membrane into two phases, and the amine-containing wastewater (retentate) thus obtained is incinerated in a thermal oxidizer. Before incineration, the wastewater can be further separated by means of an additional distillation, in order in this way, for example, to lead with discharged product back into the reaction cycle or product work-up. The retentate of the membrane separation stage can be wholly or partly fed back into the reactor or work-up. Particularly preferably, the aqueous phase of the reaction is removed and separated via a membrane into two phases. The amine-containing wastewater thus obtained is then incinerated in a thermal oxidizer or otherwise disposed of, eg in a biological work-up, and the membrane separation retentate is partially recycled to the reactor. In addition, it is possible to further concentrate the retentate in a distillation stage. The concentrate thus obtained can then be partially returned to the reactor.

As an alternative to a membrane separation, the aqueous phase of the reaction can be removed and separated in a distillation. The recovered distillation bottoms are then fed back to the reactor. The aqueous phase is removed for disposal. This disposal may be, for example, combustion in a thermal oxidizer or biological work-up.

The recovered methacrolein in turn is in particular preferably converted to methacrylic acid or methyl methacrylate after purification in a second process which is continuously subsequent to the process.

The Mannich reaction-based methods useful in the preparation of methacrolein are known and appreciated by those skilled in the art

corresponding review article, for example in Ullmann's Encyclopedia of

Industrial Chemistry 2012, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim,

Acrolein and Methacrolein, DOI: 10.1002 / 14356007.a01_149. pub2. In particular, the invention relates before the supply of the amine-containing

Reaction water particularly preferred method performed on a

continuously performed Mannich reaction, as in the European

Patent application is disclosed with the Anmeldeaktenzeichen 13002076.1.

In accordance with the invention, to clarify such a preferred precursor, reference is made to the disclosure content of this application with regard to the methacrolein synthesis. Such, particularly preferred Mannich reaction is in the presence of 0.1 to 20 mol% of organic base, preferably a secondary amine, and 0.1 to 20 mol% acid, based on the propanal used, at a temperature of 100 to 300 ° C and carried out at a pressure of 5 to 100 bar. The acids are generally inorganic acids or organic mono-, di- or polycarboxylic acids, preferably monocarboxylic acids, in particular aliphatic monocarboxylic acids. Particular preference is given to using at least one organic acid, particularly preferably acetic acid, for the reaction of propanal and formaldehyde. The proportion of acid is between 0.1 and 20, advantageously from 0.5 to 10, preferably 1 to 5 mol%, based on propanal.

As inorganic acids are in particular sulfuric acid, phosphoric acid, hydrochloric acid, carbonic acid or boric acid in question. Suitable organic compounds besides acetic acid are also formic acid, propionic acid, isobutyric acid, n-butyric acid, oxalic acid, adipic acid, caprylic acid, phenylformic acid and 2-ethylhexylic acid. In particular, mixtures of two or more acids can be used. In this case, mixtures of organic and inorganic acids, in particular of acetic acid and sulfuric acid are also well suited.

Preferably, an organic acid or a mixture of an organic acid and sulfuric acid is used. Particular preference is given to using only formic acid, acetic acid or propionic acid.

Examples of secondary amines which are added to the system as catalyst are: dimethylamine, diethylamine, methylethylamine,

Methylpropylamine, dipropylamine, dibutylamine, di-isopropylamine, diisobutylamine, methylisopropylamine, methylisobutylamine, methylsec-butylamine, methyl- (2-methylpentyl) -amine, methyl- 2-ethylhexyl) amine, pyrrolidine, piperidine, morpholine, N-methylpiperazine, N-hydroxyethyl-piperazine, piperazine, hexamethyleneimine,

Diethanolamine, methylethanolamine, methylcyclohexylamine, methylcyclopentalamine, dicyclohexylamine or corresponding mixtures. The secondary amine is preferably dimethylamine or diethylamine, more preferably dimethylamine. Suitable tertiary amines which are added to the system as catalyst or formed during the process are, for example: trimethylamine, triethylamine, dimethylethylamine, diethylmethylamine, dimethylpropylamine,

Dipropylmethylamine, tripropylamine, tributylamine, triisopropylamine, triisobutylamine, dimethylisopropylamine, dil-isopropylmethylamine, dimethylisobutylamine, di-isobutylmethylamine, triethanolamine, dimethylethanolamine,

Diethanolmethylamine, dimethylcyclohexylamine, dicyclohexylmethylamine,

Dimethylcyclopentalamine, dicyclopentylmethylamine, triicyclohexylamine or corresponding mixtures. Preferably, the tertiary amine is trimethylamine or triethylamine, more preferably trimethylamine.

Most preferably, the secondary alkylamine is dimethylamine and at the same time the tertiary alkylamine is trimethylamine.

The proportion of organic base is between 0.1 and 30, advantageously from 0.5 to 20, preferably 1 to 10 mol%, based on propanal. The ratio of the equivalents of amine to acid is preferably chosen such that a pH of 2.5 to 9 results in the reaction mixture before the reaction.

In particular, it is a great advantage of the present invention that the MAL synthesis compared to the prior art with significantly reduced

Wastewater quantity can be carried out. Surprisingly, since the tertiary alkylamine does not have to be continuously discharged from the system and at the same time the secondary amine has to be renewed to a lesser extent, the continuous production process can be carried out with this reduced amount of wastewater.

This reduces the number of cleaning steps as a further advantage at the same time. This applies in particular to the wastewater, which is much more concentrated during discharge.

A great advantage of the method according to the invention is that this can be carried out with relatively simple and cost-effective or in already existing systems. Here, the systems are easy to maintain and cause low maintenance costs. The following examples serve to illustrate more preferred

Embodiments of the present invention, without thereby a

Limitation of the invention should take place.

Examples

In a plant according to FIG. 1 is continuously propanal (PA) with

Formaldehyde using dimethylamine (DMA) or a DMA-TMA mixture and a mixture of acetic acid (AcOH) to sulfuric acid of 2.8 to 1 implemented. The amine-proton ratio was adjusted to 0.75. When calculating this ratio, the sulfuric acid is naturally taken into account twice over acetic acid. The amounts of amine used are shown in Table 1.

251 g / h PA and 349 g / h of a 37 percent formalin become homogeneous

premixed (ratio molar 1: 1). The catalyst solution, consisting of the amines and acids mentioned, is driven into the preheater (12). Both streams are heated to a temperature of 170 ° C prior to combining. The preheated streams are combined in a T-mixer directly with a T-mixer

Flow tube reactor (1/16 inch pipe with a length of 4.2 m) is connected. The thermostating of the reactor is carried out with an oil bath, which is operated at 180 ° C, the residence time is less than 10 s (see Table 1), the pressure in the tubular reactor 70 bar. After the tube reactor, the mixture is expanded in valve (14) and fed to the column (15). 335 g / h of the bottom effluent are returned to the reactor (13), disposed of 370 g / h of the bottom effluent as wastewater. To

Liquefaction of the top stream in the condenser (16) and phase separation in (17) becomes a methacrolein rich phase with a methacrolein content of 96.5%

Dissolved product (1 1 1) and recycled the aqueous effluent of the phase separator in the column (15). The conversion of propionaldehyde, and the yield, based on the propionaldehyde used are shown in Table 1. The reactions of Examples 3 to 5, and Comparative Examples (VB) 4 and 5 were carried out deviating at an oil bath temperature of 160 ° C, instead of 180 ° C. In addition, in these Examples / Comparative Examples, as the acid, only acetic acid and no mixture of sulfuric acid and

Used acetic acid. In this case, an amine-proton ratio of 0.91 was set.

Table 1

yield

Quantity DMA Amount TMA Dwell Time Sales PA /

TIMES

mol / mol PA mol / mol PA l s%

/%

Ex.1 0.029 0.01 1 8.6 99.8 95.6

Ex. 2 0.022 0.018 8.6 91, 4 96.7

VB1 0.040 0 8.6 99.9 95.4

VB2 0.029 0 8.6 98.7 96.7

VB3 0.019 0 8.6 82.7 92.7

Ex.3 0.039 0.0068 9.5 99.2 97.0

Example 4 0.039 0.0136 9.5 99.5 97.0

VB4 0.039 0 9.5 98.4 96.5

Example 5 0.061 0.047 9.5 99.9 98.1

VB5 0.060 0 9.5 99.9 98.0

Example 6 0.062 0.024 9.7 99.9 98.0

Example: 0.064 0.064 9.4 99.9 98.0

Ex. 0.065 0.084 9.3 99.9 98.0

Ex. 9 0.080 0.160 9.5 99.9 98.0

Ex. 10 0.064 0.127 9.7 99.9 97.6

VB6 0.042 0 9.5 98.3 96.5

Ex.1 1 0.042 0.007 9.5 99.6 97.5

Ex. 12 0.042 0.015 9.5 99.8 97.5

Ex. 13 0.042 0.022 9.5 99.8 97.5 It is clear from Examples 1 and 2 in comparison to Examples VB2 and VB3 that with the additional presence of TMA, with identical amounts of DMA, the yield and the conversion can be significantly increased. From the comparison of Ex.1 and VB1 even that compared to the prior art is very

surprising result visible that at lower TMA contents of less than 40 mol% and an identical amine substance concentration, both the yield and the propionaldehyde conversion are almost unchanged. Only at higher levels of TMA, according to Example 2, both go back a little. However, also in this case, both the conversion and the yield are still in an economically interesting area.

From Examples 3 and 4, it can be seen again with respect to Comparative Example 4 that surprisingly, even when enriching TMA in the reactor - as is simulated here by additional amounts in the experimental setup - higher conversions and yields are achieved, even if the selectivity is minimally reduced seems to be. However, this small loss of selectivity is more than offset by the increase in sales.

Examples 5 and 6 and Comparative Example 5 again show that, with particularly high amine concentrations, it is expected that a particularly high conversion and high MAL yields can be achieved. However, it is surprising and in great contradiction to the state of the art that these high conversions are achieved even if there is so much trimethylamine in the reactor that the ratio of trimethylamine to dimethylamine is only slightly below 0.8.

From Examples 7 to 10 it can be seen that surprisingly high yields and selectivities can be achieved even with equimolar amounts of TMA and DMA or with a TMA excess. This shows last that with the present invention a long-standing prejudice of the prior art has been overcome.

It will be readily apparent to one skilled in the art that these attempts are also transferable to continuous manufacturing processes in which TMA accumulates. From Examples VB6 and 1 1 to 13 it can be seen again that both the selectivity and the yield increase surprisingly at a constant DMA concentration and constant other process parameters with simultaneously increasing TMA concentration. It can be concluded not only that TMA does not interfere with the reaction contrary to the general teaching of the prior art, but also catalytically contributes to the reaction itself.

LIST OF REFERENCE NUMBERS

Fig. 1: Schematic representation of an apparatus suitable for carrying out the method according to the invention

FOL formalin (aqueous formaldehyde solution)

PA propanal

DMA aqueous dimethylamine solution

AcOH acetic acid

MAL methacrolein

1 1 heat exchanger (preheater)

12 heat exchangers (preheater)

13 reactor (tubular reactor)

14 pressure relief valve

15 MAL distillation column

16 capacitor

17 phase separator

101 line aqueous formalin

102 line Propanal

103 line in heat exchanger

104 line dimethylamine (40% aqueous solution)

105 line acetic acid

106 line in heat exchanger

107 line in reactor

108 line product mixture to the column

109 line condensate

1 10 reflux in column

1 1 1 MAL to level B)

1 12 pipe to wastewater

1 13 return sump drain

Claims

claims

1 . Process for the propanal in the presence of 0.1 to 30 mol% organic base and 0.1 to 30 mol% acid, in each case based on propanal, at a temperature of 100 to 300 ° C and at a pressure of 5 to 100 bar continuously is reacted with formaldehyde to methacrolein, characterized in that it is the organic base is a mixture of a secondary alkylamine and a tertiary alkylamine in a substance ratio between 20 to 1 and 1 to 3.

2. The method according to claim 1, characterized in that the

Substance ratio between the secondary alkylamine and the tertiary alkylamine between 7 to 1 and 1 to 1.

3. Process according to claim 1 or 2, characterized in that the secondary alkylamine is dimethylamine and the tertiary alkylamine is trimethylamine.

4. The method according to any one of claims 1 to 3, characterized

in that the alkylamines are added to the system as a mixture.

5. The method according to any one of claims 1 to 3, characterized

in that only secondary alkylamines are added to the plant, the tertiary alkylamines accumulate during operation of the plant, the ratio of secondary to tertiary alkylamines is determined continuously or regularly, and the amine-containing

Catalyst solution falls below the ratio of

Amine components of secondary alkylamine to tertiary alkylamine is renewed from 1 to 3.

6. The method according to any one of claims 1 to 5, characterized

characterized in that the aqueous phase of the reaction is continuously, semicontinuously or batchwise removed, optionally separated by a membrane into two phases, the amine-containing wastewater thus obtained in a Thermal Oxidizers burned and the retentate of the membrane separation wholly or partially is fed back into the reactor.

7. The method according to claim 6, characterized in that the aqueous phase of the reaction is removed, separated by a membrane into two phases, the amine-containing wastewater thus obtained in a thermal oxidizer burned and the retentate membrane separation in a

Distillation is concentrated and the concentrate is fed back into the reactor.

8. The method according to any one of claims 1 to 5, characterized

characterized in that the aqueous phase of the reaction is removed, is separated in a distillation, the distillation bottoms are fed back into the reactor and the aqueous phase is discharged for disposal.

9. The method according to any one of claims 1 to 8, characterized

in that the methacrolein recovered is converted into methacrylic acid or methyl methacrylate in a second process continuously following the process.

10. The method according to any one of claims 1 to 9, characterized

in that one or more organic acids or a mixture of an organic acid and sulfuric acid are used as the acid.

1 1. A method according to claim 10, characterized in that is used as the acid formic acid, acetic acid or propionic acid.