JP2019510766A - Catalysts and processes for the production of paraxylene - Google Patents

Abstract

A fluid bed process for producing para-xylene by methylating toluene and / or benzene with methanol using a dual function catalyst system. The first catalyst achieves the methylation of toluene and / or benzene. The second catalyst converts the byproducts of the methylation reaction or unconverted methylating agent to improve the yield of the desired product, or to achieve a combination of these. By including the second catalyst, the C1 to C5 non-aromatic fraction can be suppressed by more than 50% thereof to significantly enhance the formation of aromatics. [Selected figure] Figure 2

Description

Inventor name: Soul Tonidis, Nicolaos; Detogen, Todd Yi; Wegel, Scott Jay
CROSS-REFERENCE TO RELATED APPLICATIONS This application is a European patent application No. 16170703.9 filed on May 20, 2016 March 25, U.S. Provisional Patent Application No. 62/313, 313 and 2016, filed Priority is claimed and its benefits, the contents of which are incorporated herein by reference.
Technical field

  The present disclosure relates to catalysts and processes for producing para-xylene by alkylating benzene and / or toluene with methanol.

  Of the xylene isomers, para-xylene is particularly valuable. This is because it is useful for producing terephthalic acid, which is an intermediate in the production of synthetic fibers. Today, para-xylene is produced commercially by hydroprocessing (catalytic reforming) of naphtha, steam cracking of naphtha or gas oil and disproportionation of toluene.

  One problem with most existing processes for producing xylene is that these processes produce a thermodynamic equilibrium mixture of ortho (o), meta (m) and para (p) xylenes, among which para The xylene concentration is typically only about 24% by weight. Thus, separation of para-xylene from such mixtures typically requires ultra-precision fractionation and a multistage refrigeration process. Such processes have high operating costs and only limited yields are obtained. Thus, there is a continuing need to provide a xylene production process that is highly para isomer selective.

  It is well known to produce xylene by alkylating toluene and / or benzene with methanol, and in particular to selectively produce para-xylene (PX) products using a zeolite catalyst. For example, U.S. Patents 4,002,698, 4,356,338, 4,423,266, 5,675,047, 5,804,690, 5,939,597 Nos. 6,028,238, 6,046,372, 6,048,816, 6,156,949, 6,423,879, 6,504,072, See 6,506,954, 6,538,167 and 6,642,426. The terms "paraxylene selectivity", "paraselective" and the like mean that paraxylene is produced in an amount greater than that present in the mixture of xylene isomers in thermodynamic equilibrium, The paraxylene concentration at thermodynamic equilibrium is about 24 mole% at normal process temperatures. Because of the economic importance of para-xylene compared to meta and ortho-xylene, para-xylene selectivity is highly sought after. Although each of the xylene isomers has important and well-known end uses, para-xylene is currently the most economically valuable.

  In this process, typically toluene and / or benzene are alkylated with methanol in the presence of a suitable catalyst to form xylene in the reactor of the system schematically shown in FIG. In FIG. 1, the feedstock containing reactants enters fluid bed reactor 11 via conduit 1, the effluent containing product exits through conduit 5 and the catalyst is fluid bed reactor 11, An apparatus 12 (which volatizes the fluid from the catalyst) and a catalyst regenerator 13 are circulated via conduits 2, 3 and 4 respectively. Water is typically supplied with toluene and methanol to minimize coking of toluene and autolysis of methanol in the feed line. Other side reactions include the formation of light olefins and light paraffins as a reaction for converting para-xylene to other xylene isomers or heavier aromatics.

Although the methylation of toluene, and in particular the para-selective toluene methylation process of US Pat. No. 6,504,072, provides an attractive route to para-xylene, this process inevitably leads to a considerable amount of C ₁ Produces ~ C ₅ non-aromatics. Therefore, it is desirable to reduce the formation of C ₁ -C ₅ non-aromatics in the toluene methylation reaction to produce more aromatics.

Some embodiments disclosed herein provide a process and dual function catalyst system for methylating toluene and / or benzene in a fluid bed reactor. Due to the nature of the fluidized bed reactor, the dual function catalyst system is preferably a core shell catalyst. By core-shell catalyst is meant a catalyst comprising one zeolite structure, ie a shell, which performs one type of chemical reaction, and a similar or different zeolite structure, ie a core, which carries out or promotes different reactions. In one embodiment, the core-shell catalyst comprises shell zeolite crystals performing a toluene methylation reaction, and core zeolite crystals, wherein the core zeolite crystals are olefins produced as by-products in the toluene methylation reaction and Further conversion of the paraffin or unconverted methylating agent, or improving the yield of the desired product, such as aromatics, or both is performed. By including the second catalyst, it is possible to suppress the C ₁ -C ₅ non-aromatic fraction by more than 50% thereof and to significantly enhance the formation of aromatics.

This process comprises, in a fluid bed reactor, a core crystal of a first medium pore diameter aluminosilicate zeolite and a shell of a second medium pore diameter aluminosilicate zeolite covering at least a portion of the outer surface of the core crystal. Providing a catalyst comprising a discontinuous layer of crystals. The shell crystal may be the same as or different from the core crystal. In one embodiment, the shell crystals comprise ZSM-5 and phosphorous or compounds thereof having a silica / alumina molar ratio of at least 200 measured prior to any steaming of the catalyst, wherein the catalyst is at least 900 ° C. of it is those that are steamed at a temperature of about 0.1 to 15 seconds when the steamed catalyst was measured by the 2,2-dimethylbutane pressure of 120 ° C. temperature and 60 torr (8 kPa) ^{- It} has a diffusion parameter for ^{1, 2} , 2-dimethylbutane. The core crystals may also be ZSM-5, where ZSM-5 has higher activity and / or higher para-xylene selectivity than shell crystals, or metals for further conversion of olefins and paraffins It is one of those taken in. The core-shell catalyst alkylates a C ₆₊ aromatic hydrocarbon with an alkylating agent selected from methanol, dimethyl ether and mixtures thereof under conditions including a temperature of at least 400 ° C. in the presence of shell crystals and core crystals Convert the formed olefins and / or paraffins, the unconverted alkylating agent and the unconverted C _{6 +} aromatic hydrocarbon in the presence of

  Some embodiments disclosed herein also include a discontinuous layer of core crystals of a first medium pore aluminosilicate zeolite and shell crystals of a second medium pore aluminosilicate zeolite. The shell crystals of the second medium pore diameter aluminosilicate zeolite may be the same as or different from the core crystals, and include at least a portion of the outer surface of the core crystals. Shell crystals are effective in achieving toluene methylation, and core crystals convert olefins and / or paraffin by-products produced by the toluene methylation reaction and / or improve aromatic yields It is effective to do.

  These and other objects, features, and advantages will become apparent in the following detailed description, the drawings, the specific embodiments, the experiments and the appended claims.

FIG. 1 is a schematic view of a reactor system comprising a reactor and regeneration tower and several associated ancillary equipment and transfer conduits as known per se in the art.

FIG. 1 is a schematic view of a core-shell catalyst according to at least some embodiments disclosed herein.

It is a comparison graph of the component in the product flow of reaction AD in an Example.

At least some embodiments described herein include a fluidized bed process that produces para-xylene by methylating toluene and / or benzene with methanol using a dual function catalyst system. The first catalyst accomplishes the methylation of toluene and / or benzene, and the second catalyst converts the byproducts of the methylation reaction or unconverted methylating agent, or the yield of the desired product Improve, or achieve a combination of these. By including the second catalyst, it is possible to suppress the C ₁ -C ₅ non-aromatic fraction by more than 50% thereof and to significantly enhance the formation of aromatics.

  For purposes of the description and claims herein, the reference to the group number of the element corresponds to the May 1, 2013 edition of the International Pure Applied Chemistry Association (IUPAC) Periodic Table.

  "Toluene methylation" as used herein may also include benzene methylation.

  The alkylation process used in the present invention can use any aromatic feed comprising toluene and / or benzene. However, it is generally preferred that the aromatic feedstock comprises at least 90% by weight, especially at least 99% by weight of benzene, toluene or mixtures thereof. Aromatic feedstocks comprising at least 99 wt% toluene are particularly desirable in at least some embodiments. Similarly, although the composition of the methanol-containing feedstock is not critical, it is generally desirable to use at least 90% by weight and especially at least 99% by weight of methanol.

  The bifunctional catalyst system used in the alkylation process is preferably a "core-shell" catalyst or a coated catalyst. There are unique challenges in using a dual function catalyst system in a fluid bed reactor. The reason is that stacking two catalysts is not an option. One possible solution is to include both catalysts in the reactor. However, this solution does not allow control of the reaction mechanism since all reactions occur simultaneously. Another possible solution is to use two reactors in series. However, this is not preferable for financial reasons. Core-shell catalysts allow the use of a single reactor and management of the two reaction mechanisms. As used herein, a core-shell or coated catalyst includes one zeolite structure, ie a shell that carries out one type of chemical reaction, as well as similar or different zeolite structures, ie a core that carries out or promotes different reactions. Means catalyst that is One or both of these zeolite structures may also contain metals. The terms core-shell catalyst and coated catalyst can be used interchangeably herein. An example of a coated catalyst is found in US Pat. No. 7,335,295, the contents of which are incorporated herein by reference.

  Referring now to FIG. 2, the core-shell catalyst of the embodiments disclosed herein comprises at least a portion of the outer surface of a first crystal 22 (referred to herein as a core crystal). It comprises a coated layer of second crystals 20 of a second zeolite to be coated (this is referred to herein as shell crystals). The shell crystal 20 can grow into one and form a thick layer covering the core crystal 22. By coating the core crystals 22 with the shell crystals 20, the accessibility of the reactants and products to the outer surface acid sites of the core zeolite 22 is reduced. As used herein and in the claims, the term "coating" refers to a discontinuous layer of a second or shell zeolite crystal (eg, second crystal 20), a shell zeolite crystal as a core crystal, and the like. On the outer surface of the first or core zeolite crystal (eg, the first crystal 22) such that it is discontinuous, ie, the crystal framework of the shell zeolite crystal is not part or a continuum of the framework of the core zeolite crystal By deposited or grown on at least a portion, it is meant to be formed by coating it. Thus, the layer deposited on the core zeolite crystals 22 is not isocrystalline with the core zeolite crystals 22. It should be understood that the representation of crystals 20, 22 in FIG. 2 is schematic in nature, and should not be construed as specifically defining the specific physical shape of the core-shell catalyst embodiment.

  Preferably, the shell crystal 20 covers at least 20 percent (ie 20%) of the outer surface of the core crystal 22, more preferably at least 75 percent (ie 75%) of the outer surface of the core crystal. Although FIG. 2 shows that the shell crystal 20 covers substantially all of the outer surface of the core crystal 22, such complete coverage is not necessary and, in at least some embodiments, the shell. It should be understood that the crystal 20 may cover less than all of the outer surface of the core crystal 22. The covering layer (e.g. of the shell crystal 20) is usually nonuniform and may be attached to the surface of the core crystal 22. Another way of describing the coverage of the shell crystal 20 is the ratio of the shell crystal 20 to the core crystal 22. In some embodiments, the ratio of shell crystal 20 to core crystal 22 is 20: 1 or 10: 1 or 8: 1 or 5: 1 or 2: 1.

  In one embodiment, the core-shell catalyst comprises a shell zeolite crystal 20 performing a toluene methylation reaction and a core zeolite crystal 22, wherein the core zeolite crystal is formed as a by-product in the toluene methylation reaction Either one or both of further converting olefins and paraffins or improving the yield of the desired product, eg aromatics, is carried out.

  The shell crystals 20 of the core-shell catalyst are medium pore aluminosilicate zeolites which are preferably steamed, phosphorus-modified and in their protonated form, for example US Pat. No. 9,012,711. No. 6,095,095, the contents of which are incorporated herein by reference. Medium pore zeolite is generally defined as having a pore size of about 5 to about 7 angstroms, where the zeolite is free to sorb molecules such as n-hexane, 3-methylpentane, benzene and p-xylene . Another general definition of mesoporous zeolites includes the constraint index test described in US Pat. No. 4,016,218, the contents of which are incorporated herein by reference. In this case, the mesoporous zeolite is about 1 to 12 measured for a single zeolite without any oxide modifier introduced to control the diffusivity of the catalyst and before being subjected to any steaming. Have a constraint index of In addition to medium pore aluminosilicate zeolites, other medium pore acidic metallosilicates such as silicoaluminophosphate (SAPO) can be used in the process of the present invention.

  Specific examples of suitable medium pore zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48 and MOR, ZSM-5 and ZSM-11 is particularly preferred. ZSM-5 zeolite and its conventional preparation method are described in US Pat. No. 3,702,886. ZSM-11 zeolite and its conventional preparation method are described in US Pat. No. 3,709,979. ZSM-12 zeolite and its conventional preparation method are described in US Pat. No. 3,832,449. ZSM-23 zeolite and its conventional preparation method are described in U.S. Pat. No. 4,076,842. ZSM-35 zeolite and its conventional preparation method are described in U.S. Pat. No. 4,016,245. ZSM-48 and its conventional preparation method are taught by US Pat. No. 4,375,573. The entire disclosures of these US patents are incorporated herein by reference.

In at least some embodiments, the medium pore zeolite is ZSM-5. The ZSM-5 used in the process of the present invention is typically at least 200, preferably at least 350, more preferably at least 350, as measured prior to any steaming of the catalyst to adjust the diffusivity of the catalyst. It is an aluminosilicate or silicate having a molar ratio of 450 silica (SiO ₂ ) to alumina (Al ₂ O ₃ ). After steaming (described below), the molar ratio of silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) may be at least 900.

The shell zeolite crystals 20 used in the process of the present invention are preferably steamed and about 0 when the steamed catalyst is measured at a temperature of 120 ° C. and a 2,2-dimethylbutane pressure of 60 Torr (8 kPa). 1. Steam to have a diffusion parameter for 2, 2-dimethyl butane of ^{1 to} 15 seconds- ¹ . The diffusion parameter used herein of this particular porous crystalline material is defined as D / r ² × 10 ⁶ , where D is the diffusion coefficient (cm ² / s) and r is the crystal It is a radius (cm). Assuming that a flat sheet model accounts for this diffusion process, diffusion parameters can be derived from sorption measurements. Thus, for a given sorbate sorption volume Q, the value of Q / Qeq (where Qeq is the equilibrium sorbate sorption volume) is mathematically related to (Dt / r ² ) ^1/2 Where t is the time (in seconds) required to reach the sorbate sorbed amount Q. A graphical solution for planar sheet models is described in J.M.S., "Math of Diffusion," Oxford University Press, Ely House, London (1967). Shown by Crank.

The mesoporous zeolites described above are preferred for the process of the present invention. The reason is that the size and shape of the pores are more suitable for producing p-xylene than other xylene isomers. However, conventional forms of this zeolite have diffusion parameter values which exceed the desirable range for the process of the present invention by 0.1 to 15 seconds ⁻¹ . Nevertheless, strictly steaming the zeolite to provide a controlled reduction of the micropore volume of the catalyst to less than 50%, preferably 50 to 90%, of the unsteamed catalyst , The required diffusion rate can be achieved. The reduction in micropore volume is observed by measuring the n-hexane adsorption capacity of the zeolite at 90 ° C. and n-hexane pressure of 75 Torr (10 kPa) before and after steaming.

  Steaming to achieve the desired diffusivity and micropore reduction of the porous crystalline material is preferably at a temperature of at least about 900 ° C., preferably about 950 to about 1075 ° C., most preferably about 1000 to about 1050 ° C. And about 10 minutes to about 10 hours, preferably 30 minutes to 5 hours, such as 30 minutes to 2 hours, by heating the material in the presence of steam. Other preferred temperatures and temperature ranges are from any lower limit temperature and / or time listed in this paragraph to any upper limit temperature and / or time listed herein, eg, about 900-1050 ° C., about 10 minutes -2 hours etc. are mentioned.

  In order to achieve the desired controlled reduction of diffusivity and micropore volume, porous crystalline material prior to steaming, IIA, IIIA, IIIB, IVA, VA, of the periodic table (IUPAC version), It may be desirable to combine with at least one oxide modifier which is preferably selected from oxides of elements of groups VB and VIA. The at least one oxide modifier is advantageously chosen from the oxides of boron, magnesium, calcium, lanthanum and preferably phosphorus. In some cases, it may be desirable to combine the porous crystalline material with a combination of two or more oxide modifiers, such as phosphorus and calcium and / or magnesium. Because it may be possible to reduce the severity of the steaming needed to achieve the target spreading factor value. The total amount, measured on an elemental basis of the oxide modifier, present in the catalyst is about 0.05 to about 20% by weight, for example about 0.1 to about 10% by weight, based on the weight of the final catalyst It is also good.

  When the modifier contains phosphorus, incorporation of the phosphorus modifier into the catalyst can be carried out according to U.S. Patent Nos. 4,356,338, 5,110,776, 5,231,064 and Advantageously, this is achieved by the method described in US Pat. No. 5,348,643, the entire disclosure of which is incorporated herein by reference. Treatment with phosphorus-containing compounds is facilitated by contacting ZSM-5 alone or with a binder material with a solution of the appropriate phosphorus compound, subsequently drying and calcining to convert the phosphorus to its oxide form Can be achieved. The contacting with the phosphorus-containing compound is generally carried out at a temperature of about 25 ° C to about 125 ° C for about 15 minutes to about 20 hours. The concentration of phosphorus in the contacting mixture may be about 0.01 to about 30 wt%.

  After preparation of the phosphorus-containing compound, the catalyst may be dried and calcined to convert the phosphorus to its oxide form. The calcination is carried out in an inert atmosphere or in the presence of oxygen, for example at a temperature of about 150-850 ° C., for example 300-650 ° C., or about 540-810 ° C. in air for at least 30 minutes, for example 45-90. It can be carried out for a minute or for 30 to 60 minutes.

  Representative phosphorus-containing compounds that may be used to incorporate a phosphorus oxide modifier into the catalyst are already disclosed in US Pat. No. 6,504,072.

  The phosphorus oxide modifier is generally present in the catalyst in such an amount that the catalyst comprises 1 to 10% by weight, for example 2 to less than 8% by weight, for example 2 to 6% by weight of phosphorus based on elemental phosphorus.

  In one embodiment, a phosphorus source, such as phosphoric acid, is added to a slurry of ZSM-5 in deionized water. Then a clay, such as kaolin clay, for example Thiele RC-32, is added to the slurry of ZSM-5 and the phosphorus compound. The spray-dried product from this step is then calcined, preferably in air and at a nominal temperature of about 540-810 ° C., and then steamed.

  The core crystals 22 of the core-shell catalyst further convert the reactants not converted by the shell crystals and aromatize the olefins and paraffins formed as by-products in the toluene methylation reaction, thereby recovering the desired aromatics Is an aluminosilicate zeolite capable of improving the rate.

In one embodiment, core crystals 22 comprise medium pore aluminosilicate zeolites, such as those described above. In a preferred embodiment, the medium pore size zeolite is ZSM-5, which may be in protonated form (HZSM-5), preferably about 10 to 800, preferably measured before any steaming of the catalyst Have a molar ratio of silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) of about 10 to 400, more preferably about 20 to 200, most preferably about 20 to 100. The core crystal 22 of the core-shell catalyst may also contain at least one element selected from Groups 6 to 14 of the periodic table. Typically, the total weight of group 6-14 elements is at least 0.01 wt% to less than about 20.0 wt%, preferably about 0.01 to 10.0 wt%, more preferably about 0.01. ~ 2.0 wt%, most preferably about 0.01-1.0 wt%, these wt% excluding any binders that may be used, based on core weight, all Not core / shell mass reference. Of course, the total weight of the Group 6-14 element shall not include the amount attributed to the molecular sieve itself or any binders used. Preferably, the Group 6-14 element is selected from Zn, Ga, Cu, Re, Mo, W, La, Fe, Ag, Pt or Pd. More preferably, the group 6-14 element is Ga or Zn. Incorporation of Group 6-14 metals helps to convert olefin and paraffin byproducts to more aromatics, thereby improving the yield of the desired aromatic product.

In another embodiment, the core crystals 22 comprise medium pore zeolites, such as ZSM-5, as described above in connection with shell crystals, but with higher activity, higher paraxylene selectivity or these The combination of This zeolite has a lower molar ratio of silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) in order to achieve higher activity levels. In one embodiment where the shell crystals have a molar ratio of silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) greater than 450 prior to steaming, the core zeolite is less than 450 silica (SiO ₂ ) prior to steaming. The molar ratio of alumina to alumina (Al ₂ O ₃ ), or the molar ratio of silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) less than 900 after optional steaming, of the increased acid sites and acid sites With increased strength. This higher activity catalyst consumes the olefin by-product of the toluene methylation reaction and produces additional aromatic and light paraffins by the aromatization reaction. Instead of or in addition to higher activity levels, this zeolite may be more selective for para-xylene. This may be achieved by steaming the zeolite.

  In yet another embodiment, the core crystal 22 comprises a zeolite different from ZSM-5. The zeolite may be any zeolite having a three dimensional structure, such as those in the ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48 or SAPO families. The zeolite may be chosen based on the desired reaction and / or the desired properties to be performed in the core.

  The core zeolite crystals 22 used in the process of the present invention may be steamed to achieve the desired diffusivity and reduction of micropore volume of the porous crystalline material. The conditions may be the same as or different from those used to steam the shell crystal 20 described above. Steaming is carried out at a temperature of at least about 900 ° C., preferably about 950 to about 1075 ° C., most preferably about 1000 to about 1050 ° C. and about 10 minutes to about 10 hours, preferably 30 minutes to 5 hours, eg 30 minutes to It can be achieved by heating the zeolite in the presence of steam for 2 hours. Other preferred temperatures and temperature ranges are from any lower limit temperature and / or time listed in this paragraph to any upper limit temperature and / or time listed herein, eg, about 900-1050 ° C. for about 10 minutes -2 hours etc. are mentioned.

  The catalyst system used in the process of the invention preferably comprises a binder or matrix material resistant to the temperatures and other conditions used in the process of the invention. Such materials include active and inactive materials such as clay, silica and / or metal oxides such as alumina. The latter may be in the form of a natural material or a gelatinous precipitate or gel, such as a mixture of silica and metal oxide. The use of materials that are active tends to alter the conversion and / or selectivity of the catalyst and is therefore generally not preferred. The inert material plays a suitable role as a diluent to control the conversion in a given process, so that the product is economically and without any other means to control the reaction rate It can be obtained orderly. These materials may be incorporated into naturally occurring clays such as bentonite and kaolin to improve the crush strength of the catalyst under commercial operating conditions. The said material, ie clay, an oxide etc., functions as a binder of a catalyst. In commercial applications it is desirable to prepare a catalyst with good crush strength as it is desirable to prevent the catalyst from collapsing into powdery materials.

  Naturally occurring clays that can be used in the catalyst of the present invention include the montmorillonite and kaolin families, which families are commonly known as subbentonite and dexy, McNammy, Georgia and Florida clays These include kaolin or others, the main mineral constituents of which are halloysite, kaolinite, dickite, nacrite or anoxite. Such clays can be used in crude form, originally mined or originally subjected to calcination, acid treatment or chemical modification. It will be appreciated that the particular clay used and its treatment will affect performance to some extent. Also, the determination of the most appropriate clay (or, more generally, the binder) is within the skill of a person of ordinary skill in the art who is aware of the disclosed invention to be determined by routine experimentation.

  In addition to the materials mentioned so far, core-shell catalysts can be composited with porous matrix materials, such as, for example, silica-alumina, silica-magnesia, silica-zirconia, silica-tria Together with silica-beryllia, silica-titania, ternary compositions such as silica-alumina-tria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia.

  In general, the catalyst composition comprises 50 to 90% by weight of binder.

  Various synthetic methods can be applied to achieve the core-shell structure. One way is to grow shell crystals on the core crystals. Another way is to start the synthesis of the core crystals and add the appropriate reagents at some point in the synthesis to start the crystallization of the shell crystals. A different approach is to deposit amorphous silica alumina on the core crystals and subsequently to modify and crystallize the amorphous silica into the desired shell crystal structure. A similar method is to synthesize the core crystals with a binder into an extrudate which can be converted to shell crystals. Yet another method involves the conventional synthesis of core crystals followed by vapor phase growth of the shell crystals. Another method that may be used is to remove the aluminum from the core crystals (by steaming or chemical erosion) to produce a surface with mesopore defects, which then grow the shell crystals thereon Or the mesoporous shell of the core crystal is impregnated with the structure directing agent of the shell crystal and then the shell crystal is crystallized.

  The alkylation process can be carried out in any known reaction vessel, but generally the methanol and aromatic feeds are placed in the above catalyst and the catalyst particles are placed in one or more fluidized beds Be brought into contact. Each of the methanol and the aromatic feedstock can be injected into the fluidization catalyst in one step. However, in one embodiment, the methanol feedstock is injected stepwise into the fluidization catalyst at one or more locations downstream from the location of the aromatic reactant injection into the fluidization catalyst. For example, an aromatic feedstock is injected into the lower portion of a single vertical fluidized bed of catalyst, and methanol is introduced into the bed in the plurality of vertically spaced middle portions of the bed. Injected, product can be removed from the top of the floor. Alternatively, the catalyst is disposed in a plurality of vertically spaced catalyst beds and the aromatic feedstock is injected into the lower portion of the first fluidized bed and a portion of the methanol is the first It can be injected into the middle part of the bed, and part of the methanol can be injected into the adjacent downstream catalyst bed or between adjacent downstream catalyst beds.

  One particular system for the alkylation process disclosed herein is described in US Pat. No. 9,095,831. However, the embodiments disclosed herein are generally applicable to fixed bed, moving bed or fluidized bed reactors.

The conditions used in the alkylation step of the process of the invention are not restricted to a narrow range but, in the case of toluene methylation, generally include the following ranges: (a) about 400 to about 700 ° C., eg about 450 (B) a pressure of about 1 atm to about 1000 psig (about 100 to about 7000 kPa), for example a pressure of about 10 psig to about 50 psig (about 170 to about 1480 kPa); (c) at least about 0.2, for example About 0.2 to about 1000 moles of toluene (in the feed to the reactor) / moles of methanol in the feed to the reactor; and (d) based on the total catalytic amount in the reactor, for the aromatic reactant For example, about 0.5 to about 500 h- ¹ and about 0.01 to about 100 h- ¹ of total coal to the total amount of each step stream of methanol reagent. The weight hourly space velocity (WHSV) of the hydrogen fluoride feedstock.

  In addition to the production of para-xylene and other xylene isomers, the process of the present invention produces steam, which can lead to rapid aging of the catalyst at the high temperatures used in the process of the present invention. Water is also advantageously and preferably added to the reaction, for example to one or more of the aromatic feed and / or the alkylating agent feed, despite the formation of water in the reaction. The addition of water in this manner was found to increase the conversion of the alkylating agent, reduce side reactions, and reduce the coking of the furnace used to heat the feed stream to the reactor. ing.

As shown in the examples below, the catalyst of the present invention illustrates the generation and improved aromatics yield of C ₁ -C ₅ nonaromatic with suppressed. Furthermore, the use of Group 6-14 metals increases methanol utilization by altering the kinetic equilibrium of the reaction. This may allow less equipment to be used to produce the same amount of para-xylene, and smaller equipment downstream of the methylation reactor to process C ₁ -C ₅ non-aromatic byproducts Make it

FIG. 3 shows the results of converting methanol to aromatics and olefins using three different catalysts under various reaction conditions. The results are displayed as bar graphs for each reaction in FIG. 3 and the weight percent of each reaction product is shown in the different shaded sections. Reaction A used ZSM-5 catalyst at a temperature of 535 ° C., a methanol partial pressure of 15 psig (103 kPa) and a weight hourly space velocity (WHSV) of 2: ¹ . Reaction B used a ZSM-5 catalyst on which 1 wt% of zinc was dispersed at a temperature of 500 ° C., a methanol partial pressure of 15 psig and a weight hourly space velocity (WHSV) of 2: ¹ . Reaction C used a ZSM-5 catalyst on which 1 wt% zinc was dispersed, at a temperature of 450 ° C., a methanol partial pressure of 15 psig and a weight hourly space velocity (WHSV) of 2: ¹ . Reaction D is ZSM-5 having 1 wt% zinc and 1 wt% phosphorus dispersed thereon, at a temperature of 450 ° C., a methanol partial pressure of 15 psig and a weight hourly space velocity (WHSV) of 2: ^1. The catalyst was used. All conversion reactions were conducted to achieve 100% conversion of the methanol feed. Although none of the catalysts used in reactions A-D were core-shell catalysts, FIG. 3 shows that the addition of Group 6-14 metals to the catalyst reduces the amount of olefins produced and the aromatics produced Is shown to increase the amount of

  Although this disclosure includes descriptions and exemplifications which refer to particular embodiments, one skilled in the art will recognize that the embodiments disclosed herein may also serve variations not necessarily described herein. will do.

Claims (25)

A process for producing para-xylene, comprising the following steps:
(A) A core crystal of a first medium pore aluminosilicate zeolite having a pore size of about 5 to about 7 angstroms in a fluid bed reactor, and at least a portion of the outer surface of said core crystal Providing a catalyst comprising a discontinuous layer of shell crystals of a medium pore aluminosilicate zeolite of 2;
(B) alkylating a C ₆₊ aromatic hydrocarbon with an alkylating agent selected from methanol, dimethyl ether and mixtures thereof in the presence of said shell crystals under conditions comprising a temperature of at least 400 ° C .; (C) converting the olefin and / or paraffin produced in step (b), unconverted alkylating agent and unconverted C ₆₊ aromatic hydrocarbon to para-xylene in the presence of said core crystals.   The process according to claim 1, wherein said second medium pore diameter aluminosilicate zeolite comprises ZSM-5 having a silica / alumina molar ratio of at least 200 measured before any steaming of said catalyst. . A process according to claim 1 or 2, wherein the second medium pore diameter aluminosilicate zeolite comprises ZSM-5 and phosphorus or a compound of phosphorus;
(A) Diffusion parameters for about 0.1 to 15 sec.sup.- ¹ for 2,2-dimethylbutane when said catalyst is measured at a temperature of 120.degree. C. and a 2,2-dimethylbutane pressure of 60 Torr (8 kPa). 3. The process of claim 1 or 2, further comprising steaming the catalyst at a temperature of at least 900 <0> C to have.   The first medium pore diameter aluminosilicate zeolite comprises ZSM-5 having a silica / alumina molar ratio lower than the silica / alumina molar ratio of the second medium pore diameter aluminosilicate zeolite. The process according to any one of 1 to 3.   The first medium pore diameter aluminosilicate zeolite has a silica / alumina molar ratio of about 10 to 100 and about 0.01 to 2% by weight of at least one of at least one of 6 and 10 measured before any steaming of the catalyst. The process of any one of claims 1 to 3 comprising ZSM-5 having a Group 14 element.   6. The process of claim 5, wherein the first medium pore size aluminosilicate zeolite comprises about 0.8 to 1.2 wt% of group 6-14 element.   The process according to claim 5 or 6, wherein the group 6-14 element is selected from the group consisting of Zn, Ga, Cu, Ag or Pt.   The process according to claim 7, wherein the group 6-14 element comprises Zn or Ga.   A process according to any one of the preceding claims, wherein the catalyst further comprises a binder.   10. The process of claim 9, wherein the binder comprises silica and / or clay.   A process according to claim 9 or 10, wherein the catalyst comprises 75-90% by weight of the binder.   12. The method of any one of claims 1-11, wherein the second medium pore aluminosilicate zeolite has been steamed at a temperature of at least 900 ° C for about 10 minutes to about 1.5 hours. process. The conditions in (b) also include a temperature of about 500-700 ° C., a pressure of about 1 atmosphere to 1000 psig (100-7000 kPa), a weight hourly space velocity of about 0.5 to about 1000 h ⁻¹ and at least about 0. 13. A process according to any one of the preceding claims, which also comprises a molar ratio of 2 of toluene to methanol. A process for producing paraxylene, comprising the following steps:
(A) preparing a core-shell catalyst comprising a discontinuous layer of shell crystals covering at least a portion of the outer surface of the core crystals in a fluid bed reactor, said shell crystals comprising Said catalyst is steamed at a temperature of at least 900 ° C., comprising ZSM-5 having a silica / alumina molar ratio of at least 200 and phosphorus or a compound of phosphorus measured before any steaming, Diffusion parameters for 2,1-dimethylbutane for about 0.1 to 15 sec- ¹ when steamed catalyst is measured at a temperature of 120 ° C and a 2,2-dimethylbutane pressure of 60 Torr (8 kPa) Wherein the core crystal comprises ZSM-5;
(B) alkylating a C ₆₊ aromatic hydrocarbon with an alkylating agent selected from methanol, dimethyl ether and mixtures thereof in the presence of said shell crystals; and (c) in the presence of said core crystals Converting the olefin and / or paraffin produced in step (b), the unconverted alkylating agent and the unconverted C ₆₊ aromatic hydrocarbon to para-xylene.   15. The process of claim 14, wherein the core crystals comprise ZSM-5 having a silica / alumina molar ratio lower than the silica / alumina molar ratio of the ZSM-5 of the shell crystal.   ZSM-5 wherein said core crystals have a silica / alumina molar ratio of about 10 to 100 and about 0.01 to 2% by weight of at least one Group 6-14 element measured before any steaming of said catalyst A process according to claim 14, comprising.   The core crystal comprises about 0.8 to 1.2 wt% of a Group 6-14 element, and the Group 6 to 14 element is selected from the group consisting of Zn, Ga, Cu, Ag and Pt. The process according to 14.   18. The process of any of claims 14-17, wherein the catalyst further comprises a binder. The conditions in (b) also include a temperature of about 500-700 ° C., a total reactor pressure of about 1 atmosphere to 1000 psig (100-7000 kPa), a weight hourly space velocity of about 0.5 to about 1000 h ⁻¹ and at least about A process according to any one of claims 14 to 18, which also comprises a molar ratio of toluene to methanol of 0.2. A catalyst composition for producing para-xylene in a fluid bed or moving bed process, said catalyst comprising: (a) a first medium pore aluminosilicate zeolite having a pore size of about 5 to about 7 angstroms (B) a discontinuous layer of shell crystals of a second medium pore diameter aluminosilicate zeolite covering at least a portion of the outer surface of said core crystals, said shell crystals comprising said core crystals May be the same or different, layers;
Contains and
Said shell crystals are configured to achieve methylation of toluene and formation of olefin and / or paraffin by-products when toluene is reacted with an alkylating agent in the presence of said shell crystals; And a catalyst composition, wherein said core crystals are configured to convert said olefin and / or paraffin by-products into para-xylene. The second medium pore diameter aluminosilicate zeolite comprises ZSM-5 having a silica / alumina molar ratio of at least 200 and a phosphorus or phosphorus compound, measured before any steaming of the catalyst, said The catalyst is steamed at a temperature of at least 900 ° C., and said steamed catalyst is about 0. 2 when measured at a temperature of 120 ° C. and a 2,2-dimethylbutane pressure of 60 Torr (8 kPa). 21. The catalyst according to claim 20, having a diffusion parameter for 2,2-dimethylbutane of ^{1 to} 15 seconds- ¹ .   The first medium pore diameter aluminosilicate zeolite comprises ZSM-5 having a silica / alumina molar ratio lower than the silica / alumina molar ratio of the second medium pore diameter aluminosilicate zeolite. The catalyst according to 20 or 21.   The first medium pore diameter aluminosilicate zeolite has a silica / alumina molar ratio of about 10 to 100 and about 0.01 to 2% by weight of at least one of at least one of 6 and 10 measured before any steaming of the catalyst. 22. A catalyst according to claim 20 or 21 comprising ZSM-5 having a Group 14 element.   24. The catalyst of claim 23, wherein the group 6-14 element is selected from the group consisting of Zn, Ga, Cu, Ag or Pt.   The catalyst according to any one of claims 20 to 24, wherein the catalyst further comprises a binder.

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