阅读说明：本技术 通过苯和/或甲苯的甲基化制备对二甲苯的催化剂 (Catalyst for producing p-xylene by methylation of benzene and/or toluene ) 是由 W·F·莱 陈诞仁 S·M·沃什伯恩 于 2018-12-11 设计创作，主要内容包括：这里所公开的实施方案包括对二甲苯的制备方法和用于对二甲苯制备方法的催化剂。在一个实施方案中,所述方法包括使包含苯和/或甲苯的芳族烃进料与包含甲醇和/或二甲基醚的烷基化试剂在至少一个烷基化反应区中在包含具有小于5的约束指数的分子筛的烷基化催化剂存在下和在烷基化条件下接触。所述烷基化催化剂包含稀土金属或碱土金属中的至少一种和粘结剂,和所述至少一种稀土金属或碱土金属的大部分沉积在所述分子筛上。另外,所述方法包括制备包含二甲苯的烷基化芳族产物。(Embodiments disclosed herein include a process for producing para-xylene and a catalyst for use in the process for producing para-xylene. In one embodiment, the process comprises contacting an aromatic hydrocarbon feed comprising benzene and/or toluene with an alkylating agent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone in the presence of an alkylation catalyst comprising a molecular sieve having a constraint index of less than 5 and under alkylation conditions. The alkylation catalyst comprises at least one of a rare earth metal or an alkaline earth metal and a binder, and a majority of the at least one rare earth metal or alkaline earth metal is deposited on the molecular sieve. In addition, the process includes producing an alkylated aromatic product comprising xylene.)

1. A process for producing para-xylene, the process comprising:

(a) contacting an aromatic hydrocarbon feed comprising benzene and/or toluene with an alkylating agent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone in the presence of an alkylation catalyst comprising a molecular sieve having a constraint index of less than 5 and under alkylation conditions, wherein the alkylation catalyst comprises at least one of a rare earth metal or an alkaline earth metal and a binder, and wherein a majority of the at least one rare earth metal or alkaline earth metal is deposited on the molecular sieve; and

(b) an alkylated aromatic product comprising xylene is produced.

2. The method of claim 1, wherein at least 70% of the at least one rare earth metal or alkaline earth metal is deposited on the molecular sieve.

3. The method of claim 2, wherein at least 90% of the at least one rare earth metal or alkaline earth metal is deposited on the molecular sieve.

4. The method of any of claims 1-3, wherein the at least one rare earth metal or alkaline earth metal comprises at least one of lanthanum or strontium.

5. The method of claim 4, wherein the at least one rare earth metal or alkaline earth metal comprises lanthanum.

6. The process of any of claims 1-5, wherein the alkylation catalyst comprises from about 1 to about 5 wt% of the at least one rare earth metal or alkaline earth metal, based on the weight of the final catalyst.

7. The process of any of claims 1-6, wherein the molecular sieve has a MWW framework structure.

8. The process of claim 7, wherein the molecular sieve is selected from the group consisting of MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8HS, UZM-37, MIT-1, and mixtures thereof.

9. The process of claim 8, wherein the molecular sieve comprises MCM-49.

10. The process of claim 8, wherein the molecular sieve comprises MCM-22.

11. The process of any of claims 1-10, wherein the alkylation conditions include a temperature of about 500 ℃ to about 700 ℃, a pressure of at least 700kPa-a, and about 10-1hr^-1Based on the Weight Hourly Space Velocity (WHSV) of the aromatic hydrocarbon feed and the alkylating agent.

12. A process for producing para-xylene, the process comprising:

(a) contacting an aromatic hydrocarbon feed comprising benzene and/or toluene with an alkylating agent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone in the presence of an alkylation catalyst comprising a molecular sieve of MWW framework structure and under alkylation conditions, wherein the alkylation catalyst comprises lanthanum and a binder, and wherein a major portion of the lanthanum is deposited on the molecular sieve; and

(b) an alkylated aromatic product comprising xylene is produced.

13. The method of claim 12 wherein said lanthanum is deposited on said molecular sieve using a milling operation.

14. The method of claim 13 wherein at least 70% of said lanthanum is deposited on said molecular sieve.

15. The method of claim 14 wherein at least 90% of the lanthanum is deposited on the molecular sieve.

16. The process of any of claims 12-15, wherein the alkylation catalyst comprises from about 1 to about 5 wt% lanthanum, based on the weight of the final catalyst.

17. The process of claim 16, wherein the molecular sieve comprises MCM-49.

18. The process of claim 16, wherein the molecular sieve comprises MCM-22.

19. The process of any of claims 12-18, wherein the alkylated aromatic product comprises at least 35 wt% para-xylene based on the total amount of xylene.

20. The process of claim 19, wherein said alkylated aromatic product comprises at least 80 xylenes.

Technical Field

The present disclosure relates generally to catalysts for the methylation of benzene and/or toluene to produce xylenes, especially para-xylene.

Background

Xylene is a valuable precursor in the chemical industry. Of the three xylene isomers, para-xylene is of prime importance because it is the starting material for the manufacture of terephthalic acid, which itself is a valuable intermediate in the preparation of synthetic polyester fibers, films and resins. Currently, the demand for para-xylene is increasing at an annual rate of 5-7%.

One known route to para-xylene is by methylation of benzene and/or toluene. For example, U.S. Pat. No. 6,504,072 discloses a process for the selective production of para-xylene, comprising reacting toluene and methanol under alkylation conditions in the presence of a catalyst comprising a porous crystalline material having about 0.1-15sec when measured at a temperature of 120 ℃ and a 2,2 dimethylbutane pressure of 60 torr (8kPa)^-1Diffusion parameter for 2,2 dimethylbutane. The porous crystalline material is preferably a medium pore zeolite, especially ZSM-5, which has been vigorously steamed at a temperature of at least 950 ℃. The alkylation conditions include a temperature of about 500 ℃ to 700 ℃, a pressure of about 1 atmosphere to 1000psig (100 to 7000kPa), a weight hourly space velocity of about 0.5 to about 1000, and a molar ratio of toluene to methanol of at least about 0.2.

Additionally, U.S. patent No. 6,642,426 discloses a process for alkylating an aromatic hydrocarbon reactant, particularly toluene, with an alkylating agent comprising methanol to produce an alkylated aromatic product, comprising: introducing an aromatic hydrocarbon reactant into the reactor system at a first location toPreparing an alkylated aromatic product, wherein the reactor system comprises a fluidized bed reaction zone comprising a temperature of 500-³The operating bed density of (a); introducing a plurality of streams of said alkylating agent into said fluidized bed reaction zone at spaced locations along the flow of said aromatic hydrocarbon reactant, at least one of said streams being introduced at a second location downstream of said first location; and recovering from the reactor system the alkylated aromatic product produced by the reaction of the aromatic reactant and alkylating agent. The preferred catalyst is ZSM-5 which has been selectivated by high temperature steaming.

As exemplified in the above-mentioned U.S. patents, the current process for the alkylation of benzene and/or toluene with methanol is carried out at elevated temperatures (i.e., 500 ℃ C. and 700 ℃ C.) in the presence of a medium pore zeolite, especially ZSM-5. This leads to a number of problems, especially with short catalyst life/cycle and therefore requiring frequent catalyst regeneration. In addition, existing processes typically result in the conversion of large amounts of methanol to ethylene and other light olefins, which reduces the yield of desired products, such as xylenes, and increases recovery costs.

Accordingly, there remains a need for improved processes and/or catalysts for the alkylation of benzene and/or toluene with methanol (or dimethyl ether) that increase the catalyst's para-xylene selectivity and produce higher than equilibrium amounts of para-xylene.

Disclosure of Invention

Brief Description of Drawings

Fig. 1 is a schematic side view of a milling operation to form a catalyst in accordance with at least some embodiments disclosed herein.

Fig. 2 is a schematic top view of the grinding operation of fig. 1.

FIGS. 3-6 are graphs showing comparative performance data for L a modified MCM-49 catalyst and an unmodified MCM-49 catalyst.

Detailed Description

The following discussion is directed to various embodiments. It is to be understood, however, that the embodiments disclosed herein have broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. In the drawings, certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. All documents described herein, including any priority documents and/or test procedures, are incorporated by reference in their entirety for all jurisdictions in which the present invention is not inconsistent with this disclosure. When multiple lower limits and multiple upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

As used herein, the term "Cn" hydrocarbon wherein n is a positive integer, e.g., 1, 2, 3,4, 5, etc., refers to a hydrocarbon having n number of carbon atom(s) per molecule. As used herein, the term "Cn +" hydrocarbons where n is a positive integer, e.g., 1, 2, 3,4, 5, etc., refers to hydrocarbons having at least n number of carbon atoms (one or more) per molecule. The term "Cn-" hydrocarbons, where n is a positive integer, such as 1, 2, 3,4, 5, etc., as used herein refers to hydrocarbons having up to n number of carbon atom(s) per molecule.

As used herein, the terms "alkylating …" and "methylating …", or "alkylating" and "methylating" are used interchangeably.

The Constraint Index (Constraint Index) is a convenient measure of the extent to which a molecular sieve provides controlled access to various sizes of molecules into its internal structure. The method of determining the constraint index is fully described in U.S. Pat. No. 4,016,218, to which reference is made for details.

Embodiments disclosed herein provide catalysts for alkylation processes for producing xylenes, especially para-xylene, and alkylation processes using such catalysts. In some embodiments, the catalysts disclosed herein can be used in alkylation processes at milder temperatures and conditions to produce xylenes with less light gas by-product and longer catalyst cycle life than conventional high temperature processes. In the catalysts of at least some embodiments disclosed herein, the zeolite of MWW framework type is modified with rare earth metals and/or alkaline earth metals to improve the selectivation (selectivity) to xylenes, especially para-xylene. In an alkylation process, an aromatic hydrocarbon feed comprising benzene and/or toluene is contacted with an alkylating agent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone in the presence of an alkylation catalyst under alkylation conditions.

In at least some embodiments, the process is effective to convert benzene and/or toluene to xylenes at substantially 100% methanol conversion and substantially no light gas production. This high methanol utilization is surprising in view of the methanol utilization in the prior art toluene and/or benzene methylation processes and achieves the significant advantage of less coke formation, which increases catalyst life. In addition, in conventional processes, steam is preferably co-fed into the reactor with the methanol to minimize methanol side reactions, and the steam negatively impacts catalyst life. Since nearly 100% of the methanol reacts with the aromatic ring to produce aromatics in the process disclosed herein, co-feed steam is not required, thereby reducing the energy requirements of the process and increasing catalyst life.

The methanol selectivity to xylene in the process disclosed herein is typically about 80%, with the major byproducts being benzene and C9+ aromatics. Benzene may be separated from the alkylation effluent and recycled back to the alkylation reaction zone(s), while the C9+ aromatics may be separated for blending into a gasoline pool or transalkylated with additional benzene and/or toluene to produce additional xylenes. In addition, the use of larger pore molecular sieves minimizes diffusion limitations and allows alkylation to be carried out at commercially viable WHSV. Furthermore, when a toluene feed (a feed containing at least 90 wt% toluene) is used, more alkylating agent reacts with toluene to produce xylenes as compared to prior processes relative to other molecules such as alkylating agent or by-products of the reaction.

The amount of para-xylene in the xylene product can be increased up to at least 35 wt.% by selectivating the alkylation catalyst.

Suitable examples of such molecular sieves include, for example, zeolite β, zeolite Y, ultrastable Y (USY), ultrahydrophobic Y (UHP-Y), dealuminated Y (Deal Y), mordenite, ZSM-3, ZSM-4, ZSM-12, ZSM-14, ZSM-18, ZSM-20, and mixtures thereof zeolite ZSM-3 is described in U.S. patent No. 3,415,736 zeolite ZSM-4 is described in U.S. patent No. 4,021,947 zeolite ZSM-12 is described in U.S. patent No. 3,832,449 zeolite ZSM-14 is described in U.S. patent No. 3,923,636 zeolite 18 is described in U.S. patent No. 3,950,496 zeolite ZSM-20 is described in U.S. patent No. 3,972,983 zeolite ZSM-56 is described in U.S. patent No. 3,308,06469 and U.S. Pat. No. 28,341 low sodium ultrastable Y (USY) is described in U.S. patent No. 3,972,766, zeolite ZSM-20 is described in U.S. patent No. 3,972,766, zeolite 56 is described in U.S. patent No. 3,308,069 and U.S. Pat. 28,7928,341 the preparation of a mixture of natural zeolite Y (UHP-593) by the synthesis of mordenite, which may also be carried out as a mordenite, such as a mordenite, zeolite synthesized by the process for the zeolite Y zeolite 369, which may be described in U.S. Pat. 3,598, U.S. Pat. 3,598.

One preferred class of molecular sieves suitable for use in the embodiments disclosed herein and having a constraint index of less than 5 is crystalline microporous materials of the MWW framework type. The term "crystalline microporous material of MWW framework type" as used herein includes one or more of the following:

molecular sieves made from common first degree crystalline building block (building block) unit cells, wherein the unit cells have MWW framework topology. (the unit cell is a spatial arrangement of atoms that if tiled in three-dimensional space describes a crystal structure that is discussed in the "Atlas of Zeolite Framework Types", fifth edition, 2001, the entire contents of which are incorporated by reference);

molecular sieves made of ordinary second degree building blocks, which are 2-dimensional tiling of the unit cells of this MWW framework topology, forming a "single layer of one unit cell thickness", preferably one c-unit cell thickness;

molecular sieves made of ordinary second degree building blocks, are "layers of one or more than one unit cell thickness", wherein the layers of more than one unit cell thickness are made by stacking, filling or bonding at least two monolayers of one unit cell thickness. Such a stack of second degree building units may be in a regular manner, an irregular manner, a random manner, or any combination thereof; and

molecular sieves made by any regular or random 2-dimensional or 3-dimensional combination of unit cells with MWW framework topology.

Crystalline microporous materials of the MWW framework type include those molecular sieves having an X-ray diffraction pattern including d-spacing maxima at 12.4 + -0.25, 6.9 + -0.15, 3.57 + -0.07 and 3.42 + -0.07 Angstrom X-ray diffraction data used to characterize the material are obtained by standard techniques using the K- α doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and an attached computer as the collection system.

Examples of MWW framework type crystalline microporous materials include MCM-22 (described in U.S. Pat. No. 4,954,325), PSH-3 (described in U.S. Pat. No. 4,439,409), SSZ-25 (described in U.S. Pat. No. 4,826,667), ERB-1 (described in European patent No. 0293032), ITQ-1 (described in U.S. Pat. No. 6,077,498), ITQ-2 (described in International patent publication No. WO 97/17290), MCM-36 (described in U.S. Pat. No. 5,250,277), MCM-49 (described in U.S. Pat. No. 5,236,575), MCM-56 (described in U.S. Pat. No. 5,362,697), UZM-8 (described in U.S. Pat. No. 6,756,030), UZM-8HS (described in U.S. Pat. No. 7,713,513), UZM-37 (described in U.S. Pat. No. 7,982,084), EMM-10 (described in U.S. Pat. 6,563512), EMM-3512 (described in U.S. Pat. No. 5,3524), EMM-366326, EMM-24, EMM-3, and mixtures thereof are generally described by Vopp-3.

In some embodiments, the crystalline microporous materials of the MWW framework type employed in the embodiments disclosed herein may be contaminated with other crystalline materials, such as ferrierite (ferrierite) or quartz. These contaminants may be present in amounts of ≦ 10 wt%, typically ≦ 5 wt%.

Additionally or alternatively, the molecular sieves useful in embodiments disclosed herein may be characterized by a silicon to aluminum molar ratio (i.e., Si/Al ratio). In particular embodiments, suitable molecular sieves herein include those having a Si/Al ratio of less than 100, preferably from about 15 to 50.

The molecular sieve catalyst may be selectivated to produce a higher than equilibrium amount of para-xylene in the product mixture (i.e., greater than about 23 wt% para-xylene, based on the total amount of xylene). In one embodiment, the concentration of para-xylene in the xylene fraction is at least 35 wt%, preferably at least 40 wt%, more preferably at least 45 wt%. The molecular sieve catalyst may be selectively deactivated ex situ by modifying the catalyst with a rare earth metal and/or an alkaline earth metal. As used herein, a target para-xylene selectivity refers to at least 35 wt%, preferably at least 40 wt%, more preferably at least 45 wt% para-xylene in the xylene fraction.

In particular, in embodiments disclosed herein, the molecular sieve can be combined with at least one modifier (e.g., an oxide modifier), such as at least one oxide selected from at least one of the rare earth metals and the alkaline earth metals. Most preferably, the at least one oxide modifier is selected from oxides of lanthanum and strontium. In some cases, the molecular sieve may be combined with more than one oxide modifier. For example, in some embodiments, the molecular sieve may be combined with oxides of one or more of boron, magnesium, calcium, and phosphorus, in addition to the oxides of the rare earth and/or alkaline earth metals described above.

In some embodiments, the total amount of rare earth and/or alkaline earth metal (measured on an elemental basis) present in the catalyst may be from about 1 to about 10 wt%, preferably from about 1 to about 5 wt%, based on the weight of the final catalyst.

Modification of molecular sieves with rare earth and/or alkaline earth metals can be achieved by direct synthesis, which proceeds as follows: the molecular sieve material, alone or in combination with a binder or matrix material, is contacted with a solution containing a suitable rare earth and/or alkaline earth metal containing compound. In some embodiments, the rare earth and/or alkaline earth metal is combined with the molecular sieve via impregnation. When the modifier comprises phosphorus, incorporation of the modifier into the catalyst is suitably achieved by the methods described in U.S. Pat. nos. 4,356,338, 5,110,776, 5,231,064, and 5,348,643, the entire disclosures of which are incorporated herein by reference.

Referring to fig. 1 and 2, in still other embodiments, the rare earth and/or alkaline earth metal can be combined with the molecular sieve via a grinding mill addition or grinding operation. In particular, in these embodiments, an oxide of a rare earth or alkaline earth metal is added to the extrusion mixture 30 and this combined material is subjected to a milling operation. In one example of such a milling operation, the mixture 30 is placed in a container or vessel 20 and a direct high pressure is applied (e.g., via roller(s) or other mechanical device(s) 10) at a lower temperature (e.g., room temperature) to facilitate mixing and bonding of the ingredients. Depending on the composition of the mixture 30, a milling operation may be used to achieve the desired positioning of the metal oxide within the catalyst.

In particular, in at least some embodiments, it is desirable to deposit the rare earth and/or alkaline earth metal directly on the molecular sieve itself (or at least a substantial portion on the molecular sieve), as opposed to being nearly uniformly distributed on the molecular sieve and binder. For example, in some embodiments, more than 50% (e.g., at least 60, 70, 80, 90, 99%) of the rare earth and/or alkaline earth metals of the catalyst are deposited on the molecular sieve. In still other of these embodiments, substantially all of the rare earth and/or alkaline earth metal of the catalyst is deposited on the molecular sieve rather than on the binder. During manufacture of these embodiments using a milling operation, the rare earth and/or alkaline earth metal (or precursors thereof) is first milled together with the molecular sieve (e.g., the crystals of the molecular sieve themselves) to facilitate bonding of the two compositions and thus deposition of the metal onto the molecular sieve. Thereafter, the combined metal and molecular sieve are milled again with other catalyst ingredients (e.g., binder) to facilitate formation of the final extrudable catalyst mixture.

The catalyst may additionally be selectivated prior to introduction into the aromatization reactor or in situ in the reactor as follows: the catalyst is contacted with a selectivating agent, such as silica, silicalite, steam, coke, or combinations thereof. In one embodiment, the catalyst is silica-selectivated as follows: the catalyst is contacted with at least one organosilicon in a liquid carrier, followed by calcining the silicon-containing catalyst in an oxygen-containing atmosphere, such as air, at a temperature of 350-. A suitable silica selectivation procedure is described in U.S. patent No. 5,476,823, which is incorporated herein by reference in its entirety. In another embodiment, the catalyst is selectively deactivated by contacting the catalyst with steam. Steaming of the zeolite is carried out at a temperature of at least about 900 c, preferably from about 950 to about 1075 c, most preferably from about 1000 to about 1050 c, for a period of time from about 10 minutes to about 10 hours, preferably from 30 minutes to 5 hours. The selectivation procedure may be repeated multiple times to alter the diffusion characteristics of the molecular sieve and may increase xylene yield.

In addition to, or instead of, silica or steam selectivation, the catalyst may also undergo coke selectivation. Such optional coke selectivation typically involves contacting the catalyst with a thermally decomposable organic compound at an elevated temperature above the decomposition temperature of the compound but below a temperature at which the crystallinity of the molecular sieve is adversely affected. Further details regarding coke selectivation techniques are provided in U.S. patent No. 4,117,026, which is incorporated herein by reference. In some embodiments, a combination of silica selectivation and coke selectivation may be employed.

The above molecular sieves may be used as alkylation catalysts herein without any binder or matrix. Alternatively, the molecular sieve may be composited with other materials resistant to the temperatures and other conditions employed in the alkylation reaction. Such materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays and/or oxides such as alumina, silica-alumina, zirconia, titania, magnesia or mixtures of these and other oxides. The latter may be naturally occurring or in the form of a gelatinous precipitate or gel comprising a mixture of silica and metal oxide. Clays may also be included with the oxide type binder to improve the mechanical properties of the catalyst or to aid in its manufacture. The use of a material in conjunction with (i.e., in conjunction with or present during the synthesis of) a molecular sieve that is itself catalytically active can alter the conversion and/or selectivity of the catalyst. The inactive material suitably acts as a diluent to control the amount of conversion so that the products can be obtained economically and sequentially without employing other means for controlling the rate of reaction. These materials can be incorporated into naturally occurring clays, such as bentonite and kaolin, to improve the crush strength of the catalyst under commercial operating conditions and to act as a binder or matrix for the catalyst. The relative proportions of molecular sieve and inorganic oxide matrix can vary widely, with the molecular sieve content ranging from about 1 to about 90 wt% of the composite and more typically, especially when the composite is prepared in the form of beads, from about 2 to about 80 wt% of the composite.

In addition, the catalysts disclosed herein may be referred to with reference to their "α value". α values are a measure of the cracking activity of the catalyst and are described in U.S. Pat. No. 3,354,078 and Journal of Catalysis, volume 4, page 527 (1965), volume 6, page 278 (1966) and volume 61, page 395 (1980), each of which is incorporated herein by reference.

The feed to the process of the present invention comprises an aromatic hydrocarbon feed (comprising benzene and/or toluene) and an alkylating agent comprising methanol and/or dimethyl ether. Any refinery aromatic feed may be used as a source of benzene and/or toluene, but in some embodiments it may be desirable to use an aromatic hydrocarbon feed comprising at least 90 wt% toluene. Additionally, in some embodiments, it may be desirable to pre-treat the aromatic hydrocarbon feed to remove catalyst poisons, such as nitrogen and sulfur compounds. In other embodiments, the feed may also include non-aromatic compounds, such as refinery aromatic feeds from which non-aromatic compounds are not extracted.

The alkylation process of the embodiments disclosed herein may generally be carried out at a temperature of from about 500 ℃ to about 700 ℃, preferably about 550 ℃ to 650 ℃. The operating pressure will vary with temperature, but oneTypically at least 700kPa-a, such as at least 1000kPa-a, such as at least 1500kPa-a, or at least 2000kPa-a, and up to about 7000kPa-a, such as up to about 6000kPa-a, and up to about 5000 kPa-a. In terms of ranges, the operating pressure may be 700kPa-a to 7000kPa-a, such as 1000kPa-a to 6000kPa-a, for example 2000kPa-a to 5000 kPa-a. Suitable Weight Hourly Space Velocity (WHSV) values based on total aromatic and alkylating agent feed are in the range of 50 to 0.5hr^-1E.g. 10-1hr^-1Within the range of (1). In some embodiments, at least a portion of the aromatic feed, methanol alkylating agent, and/or alkylation effluent may be present in the alkylation reaction zone in the liquid phase.

In some embodiments, the alkylation process of the present invention may be conducted at lower temperatures, i.e., less than 500 ℃, e.g., less than 475 ℃, or less than 450 ℃, or less than 425 ℃, or less than 400 ℃. To provide a commercially viable reaction rate, the process may be carried out at a temperature of at least 250 ℃, such as at least 275 ℃, such as at least 300 ℃. In terms of ranges, the processes in these embodiments can be conducted at a temperature of 250 to less than 500 ℃, e.g., 275-475 ℃, e.g., 300-450 ℃. In embodiments where lower operating temperatures are used (e.g., temperatures generally less than 500 ℃), the lifetime of the alkylation catalyst may be enhanced compared to higher temperature processes because methanol decomposition is much less at lower reaction temperatures.

The alkylation reaction may be carried out in any known reactor system, including but not limited to fixed bed reactors, moving bed reactors, fluidized bed reactors, and reactive distillation units. In addition, the reactor may comprise a single reaction zone or multiple reaction zones located in the same or different reaction vessels. In addition, the injection of the methanol/dimethyl ether alkylating agent may be carried out at a single location in the reactor or at multiple locations spaced along the reactor.

The product of the alkylation reaction comprises xylene, benzene and/or toluene (both remaining and co-produced in the process), C₉₊Aromatic hydrocarbons, co-produced water, oxygenate byproducts, and, in some cases, unreacted methanol. However, it is generally preferred to operate the process so that all of the methanol and aromatics are presentThe group hydrocarbon feed reacts and the alkylation product generally contains no residual methanol. The alkylation product is also generally free of light gases produced by the decomposition of methanol to ethylene and other olefins. In some embodiments, the organic component of the alkylation product may contain at least 80 wt% xylene, and para-xylene may comprise at least 35 wt% of the xylene fraction.

After water separation, the alkylation product may be fed to a separation zone, such as one or more distillation columns, to recover xylene and toluene and C₉₊Aromatic hydrocarbon by-products are separated. The resulting benzene and/or toluene can be recycled to the alkylation reaction zone while C can be recovered₉₊Aromatics are used for blending into gasoline pools or for transalkylation with additional benzene and/or toluene to produce additional xylenes. The oxygenate byproducts can be removed from the alkylation product by any means known in the art, such as adsorption as described in U.S. patent nos. 9,012,711, 9,434,661, and 9,205,401; caustic washing as described in U.S. patent No. 9,294,962; crystals disclosed in 8,252,967, 8,507,744 and 8,981,171; and conversion to ketones as described in U.S. patent publication nos. 2016/0115094 and 2016/0115103.

May be removed from the alkylation product and any downstream C₉₊The xylenes recovered from the transalkylation process are sent to a para-xylene production loop. The latter includes a para-xylene separation zone wherein the para-xylene is conventionally recovered by adsorption or crystallization or a combination of both. When the para-xylene is separated by adsorption, the adsorbent used preferably contains a zeolite. Typical adsorbents used include natural or synthetic crystalline aluminosilicate zeolites, such as zeolite X, or Y, or mixtures thereof. These zeolites are preferably exchanged by cations such as alkali or alkaline earth metal or rare earth cations. The adsorption column is preferably a simulated moving bed column (SMB) and a desorbent, such as para-diethylbenzene, para-difluorobenzene, diethylbenzene or toluene or mixtures thereof, is used to recover selectively adsorbed para-xylene. A commercial SMB unit suitable for use in the process of the present invention is PAREX^TMOr E L UXY L^TM。

Reference will now be made in particular to the following non-limiting examples.

Example 1:

the L a-containing MCM-22 crystals were synthesized from a mixture prepared from 990g of water, 80g of Hexamethylethyleneimine (HMI) (99% solution), 275g of silica, 74g of sodium aluminate solution (45%), and 13.5g of 50% sodium hydroxide solution, and 15.2g of lanthanum nitrate hexahydrate in 50g of deionized water, the mixture having the molar composition shown in Table 1 below.

TABLE 1

SiO2/Al2O3	～22.5
		H2O/SiO2	～14
OH-/SiO2	～0.15
		Na+/SiO2	～0.215
HMI/SiO2	～0.19

The mixture was reacted for 72 hours at 320 ° F (160 ℃) in a 52 liter autoclave with stirring at 250 RPM. The product was filtered, washed with deionized water and dried at 250 ° F (121 ℃). The X-ray diffraction pattern of the as-synthesized material shows a typical pure phase of MCM-22 topology. Scanning Electron Microscope (SEM) images of as-synthesized material show layeringThe resulting as-synthesized L a-MCM-22 crystals exhibited an SiO of about 21.1₂/Al₂O₃Mole ratio and 1.74 wt% L a.

The as-synthesized crystals L a-MCM-22 were converted to the hydrogen form by three ion exchanges at room temperature with ammonium nitrate solution, followed by drying at 250 ℃ F. (121 ℃) and calcination at 1000 ℃ F. (538 ℃) for 6 hours the resulting H-form L a-MCM-22 crystals had 582(515+67) m²Total (micro) + meso) surface area per gram, hexane adsorption of 99.4mg/g and α value of 770.