TWI848392B - Catalyst and methods for producing xylene products rich in o-xylene - Google Patents

Abstract

Methylation catalysts that include surface modified zeolites may be useful for converting benzene and/or toluene via methylation with methanol and/or dimethyl ether to produce xylene products with higher than equilibrium o-xylene selectivity. For example, a methylation process may include: contacting an aromatic hydrocarbon feed with a methylating agent feed in the presence of a methylation catalyst in a methylation reactor under methylation reaction conditions to produce a methylation product mixture effluent exiting the methylation reactor, wherein the methylation catalyst comprises a modified zeolite comprising (a) a zeolite of MWW framework type and (b) a surface modification agent on at least a portion of an outer surface of the zeolite, and the methylation product mixture effluent having a higher than equilibrium o-xylene selectivity.

Description

Catalyst and method for producing xylene products rich in o-xylene

The present disclosure relates to methylated catalysts comprising surface-modified zeolites, and methods of using the methylated catalysts to convert benzene and/or toluene via methylation with methanol and/or dimethyl ether to produce xylene products having higher than equilibrium ortho-xylene selectivity.

1,2-Dimethylbenzene (ortho-xylene or o-xylene) is a valuable chemical intermediate in the manufacture of para-xylene, and its demand has grown by about 2% per year over the past two decades. Ortho-xylene is primarily used in the manufacture of phthalic anhydride, a common intermediate in the manufacture of plasticizers, dyes, and enteric coatings for pharmaceuticals. As the commercial applications of ortho-xylene continue to increase, there is an increasing demand for more selective synthetic methods and improved yields for the manufacture of ortho-xylene.

o-Xylene can be extracted from BTX aromatics (benzene, toluene, and xylene isomers) in catalytic reformate produced by catalytic reforming of naphtha. Alternatively, o-Xylene can be a co-product in toluene disproportionation, transalkylation of toluene with C9+ aromatics, or methylation of toluene and/or benzene. Methylation of toluene and/or benzene is a favorable route to xylene formation due to the low cost of starting materials and the potential to provide high yields. The methylation process can use methanol and/or dimethyl ether as the alkylating agent.

Although methylation of toluene can produce ortho-xylene as one of the products, the methylation processes and catalysts have been configured to maximize the production of the isomer para-xylene at thermodynamic equilibrium. The production of higher para-xylene is dominant because para-xylene is a valuable, long-used chemical feedstock for the production of terephthalic acid and polyethylene terephthalate resins for synthetic fiber textiles, bottles, and plastics, among other industrial applications. For example, most work related to alkylation with methanol has focused on the use of selectivated zeolite catalysts, such as steamed phosphorus-containing ZSM-5, to increase the production of para-xylene. Therefore, there is a need for processes that can produce ortho-xylene with higher yields and meet rapidly increasing demand.

The present disclosure relates to methylated catalysts comprising surface-modified zeolites, and methods of using the methylated catalysts to convert benzene and/or toluene via methylation with methanol and/or dimethyl ether to produce xylene products having higher than equilibrium ortho-xylene selectivity.

Non-limiting exemplary methods of the present disclosure may include one or more of the following: contacting an aromatic feed with a methylating agent feed in the presence of a methylation catalyst under methylation reaction conditions in a methylation reactor to produce a methylation product mixture effluent exiting the methylation reactor, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, the methylation catalyst comprises a modified zeolite, the modified zeolite comprises (a) an MWW framework-type zeolite and (b) a surface modifier on at least a portion of the outer surface of the zeolite, and the methylation product mixture effluent comprises o-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

Another non-limiting exemplary method of the present disclosure may include one or more of the following: providing a precursor catalyst comprising a zeolite having an MWW framework structure; loading the precursor catalyst in a methylation reactor; contacting the precursor catalyst in the methylation reactor with a surface modifier to produce a methylation catalyst comprising a modified zeolite, wherein the modified zeolite comprises the surface modifier on at least a portion of the outer surface of the zeolite; and reacting the methylation catalyst under methylation reaction conditions. Under the conditions of the present invention, the methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene in a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

Another non-limiting exemplary method of the present disclosure may include one or more of the following: providing a precursor catalyst comprising a zeolite having an MWW framework structure; loading the precursor catalyst into a methylation reactor; contacting the precursor catalyst in the methylation reactor with water to produce a methylation catalyst comprising a modified zeolite, the modified zeolite comprising neutralized acid groups on at least a portion of the outer surface of the zeolite; and reacting the methylation catalyst under methylation reaction conditions. , contacting the methylation catalyst in the methylation reactor with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene in a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

Another non-limiting exemplary method of the present disclosure may include one or more of the following: providing a precursor catalyst comprising a zeolite having an MWW framework structure; subjecting the precursor catalyst to one or more treatments comprising contacting the precursor catalyst with an organosilicon compound, wherein each treatment is followed by calcining the precursor catalyst to produce a methylated catalyst, wherein the surface modifier is silica; loading the methylated catalyst into a methylation reactor; and The methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed under reaction conditions to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene in a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

Another non-limiting exemplary method of the present disclosure may include one or more of the following: providing a precursor catalyst comprising a zeolite having an MWW framework structure; contacting the precursor catalyst with a thermally decomposable organic compound at a decomposition temperature of the thermally decomposable organic compound or a high temperature above the decomposition temperature to deposit coke on the surface of the zeolite and produce a methylation catalyst; loading the methylation catalyst in a methylation reactor; and The methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed under appropriate conditions to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene in a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

These and other features and characteristics of the methods disclosed herein as well as their advantageous applications and/or uses will become apparent from the detailed description that follows.

The present disclosure relates to methylation catalysts comprising surface-modified zeolites, and methods of using the methylation catalysts to convert benzene and/or toluene via methylation with methanol and/or dimethyl ether to produce xylene products having a selectivity above equilibrium ortho-xylene. More specifically, the present disclosure includes methylation catalysts (and related methylation methods) comprising both a zeolite and a surface modifier on at least a portion of the outer surface of the zeolite, which produce a product mixture under methylation reaction conditions, the product mixture containing ortho-xylene at a higher concentration than in a thermodynamic equilibrium mixture of para-xylene, ortho-xylene, and meta-xylene. Generally speaking, the thermodynamic equilibrium of the xylenes contains 26% by weight of ortho-xylene. In contrast, at least some of the methylation catalysts described herein produce product mixtures having more than 75% by weight of ortho-xylene. Thus, high selectivity for ortho-xylene in the reaction can be achieved using the methylation catalysts and associated methylation methods described herein.

The zeolite used in the methylation catalyst described herein is of MWW framework type and has a surface modifier on at least a portion of the outer surface of the zeolite, wherein the surface modifier modifies the catalytic activity of the zeolite. In contrast, zeolites having different frameworks (e.g., ZSM-5 framework type and MFI framework type) and surface modifiers do not show increased selectivity for para-ortho-xylene.

Unless otherwise indicated, all numbers indicating quantities in this disclosure should be understood to be modified by the term "about" in all cases. It should also be understood that the numerical values used in the specification and patent application constitute specific embodiments. Efforts have been made to ensure the accuracy of the data in the examples. However, it should be understood that any measurement data inherently contains a certain degree of error due to the limitations of the technology and equipment used to make the measurements.

As used herein, the indefinite article "a" or "an" shall mean "at least one," unless specified to the contrary or the context clearly indicates otherwise. Thus, embodiments using "an ether" include embodiments in which one, two, or more ethers are used, unless specified to the contrary or the context clearly indicates that only one ether is used.

For the purposes of this disclosure, the nomenclature of elements is according to the Periodic Table of Elements version as described in Chemical and Engineering News, 63(5), pg. 27 (1985).

The term "Cn" compound or group, wherein n is a positive integer, means a compound or group containing n carbon atoms. Thus, a "Cm to Cn" alkyl group means an alkyl group containing a number of carbon atoms ranging from m to n. Thus, C1-C3 alkyl means methyl, ethyl, n-propyl, or 1-methylethyl-. The term "Cn+" compound or group, wherein n is a positive integer, means a compound or group containing n carbon atoms. The term "Cn-" compound or group, wherein n is a positive integer, means a compound or group containing n carbon atoms.

For simplicity, the following abbreviations may be used herein: psig is pounds-force per square inch gauge pressure, and WHSV is weight space velocity per hour. Atomic abbreviations are as shown in the periodic table (e.g., Li = lithium).

As used herein, the term "conversion" refers to the degree to which a given reactant is converted to a product in a particular reaction (e.g., methylation, isomerization, etc.). Thus, in a methylation, a conversion of 100% toluene to xylenes means complete consumption of toluene, while a conversion of 0% toluene means no measurable toluene reaction.

As used herein, the term "selectivity" refers to the degree to which a particular xylene isomer (o-xylene, m-xylene, or p-xylene) is formed for a particular reaction, based on the total weight of all xylene isomers (o-xylene, m-xylene, or p-xylene) produced. For example, for the methylation of toluene, a 50% o-xylene selectivity means that 50% of the xylenes formed are o-xylene, while a 100% o-xylene selectivity means that 100% of the xylenes formed are o-xylene. Selectivity is based on the products formed, regardless of the conversion of the particular reaction. The selectivity of a particular xylene isomer (o-xylene, m-xylene, or p-xylene) produced by a particular reactant can be defined as the weight percent (wt %) of that xylene isomer relative to the total weight of all xylene isomers (i.e., all o-xylene, m-xylene, and p-xylene) formed by the particular reactant in the reaction.

As used herein, the term "alkylation" means a chemical reaction in which an alkyl group is transferred from an alkyl source compound to an aromatic ring as a substituent thereon. "Methylation" means an alkylation in which the transferred alkyl group is a methyl group. Thus, methylation of benzene can produce toluene, xylenes, trimethylbenzenes, and the like; and methylation of toluene can produce xylenes, trimethylbenzenes, and the like. Methylation of toluene with methanol in the presence of a zeolite catalyst can be schematically illustrated as follows: Xylene includes 1,2-xylene (ortho-xylene, or o-xylene), 1,3-xylene (meta-xylene, or m-xylene), and 1,4-xylene (para-xylene, or p-xylene). One or more of these xylene isomers, especially para-xylene and/or ortho-xylene, are high-value industrial chemicals. They can be separated to produce corresponding products. However, C9 hydrocarbons are usually undesirable by-products. The above methylation reaction can be carried out in the presence of a zeolite catalyst.

As used herein, the term "procatalyst" is a formulated catalyst containing a crystalline microporous material. In this context, the procatalyst contains a zeolite having a unit cell of the MWW framework topology.

MWW zeolites have a three-dimensional, four-connected framework structure of corner-sharing [TO ₄ ] tetrahedra, where T may be a tetrahedrally coordinated atom. Molecular sieves, such as MWW zeolites, are often described in terms of the size of the rings defining the pores, where the size is based on the number of T atoms in the rings. Other framework-type characteristics include the arrangement of the rings forming the cages, and when present, the size of the channels, and the spaces between the cages. Crystalline building blocks of the MWW framework type include those molecular sieves having X-ray diffraction patterns including lattice spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07, and 3.42±0.07 angstroms. The X-ray diffraction data used to characterize the material were obtained by the standard technique using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system.

As used herein, the term "methylation catalyst" is a modified precursor catalyst comprising an MWW framework-type zeolite and a surface modifier on at least a portion of the outer surface of the zeolite. The surface modifier interacts with the zeolite surface to modify the catalytic activity of the zeolite. The interaction can be a chemical interaction (e.g., covalent bonding, hydrogen bonding, chemical adsorption, or any combination thereof) and/or a physical interaction (e.g., deposition or coating, adsorption, or any combination thereof).

In this disclosure, unless otherwise specified or the context clearly indicates otherwise, WHSV is based on the combined flow rate of the aromatic feed and the methylating agent feed. Methylation Catalyst

The present disclosure includes a method for producing o-xylene with a higher than equilibrium selectivity by methylating benzene and/or toluene with methanol and/or dimethyl ether, which can be achieved using a methylation catalyst comprising a modified zeolite, wherein the modified zeolite comprises (a) an MWW framework-type zeolite and (b) a surface modifier on at least a portion of the outer surface of the zeolite.

The methylated catalyst can be made by modifying a precursor catalyst. The modified precursor catalyst modified to provide a selectivity higher than the equilibrium ortho-xylene is referred to as a methylated catalyst herein. Surface modification can be achieved by contacting the catalyst with a surface modifier. The surface modifier interacts with the zeolite surface to modify the catalytic activity of the zeolite. The interaction can be a chemical interaction (e.g., covalent bonding, hydrogen bonding, chemical adsorption, or any combination thereof) and/or a physical interaction (e.g., deposition or coating, adsorption, or any combination thereof). Examples of surface modifiers described in more detail herein include silica, coke, large N-containing organic molecules, or a combination thereof.

Examples of MWW framework-type zeolites suitable for use as a precursor catalyst may include, but are not limited to, MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, and mixtures of two or more thereof.

The zeolite of the precursor catalyst may be contaminated by other crystalline materials, such as granular iron or quartz. The amount of these contaminants present may be ≤ 10 wt % (e.g., ≤ 5 wt %). In addition, the zeolite of the precursor catalyst may be pre-modified using cation or metal impregnation techniques, which may include, but are not limited to, ion exchange, incipient wetness impregnation, framework metal substitution, and the like. These cation and/or metal modifications may have occurred during the preparation of the precursor catalyst. Examples of elements that may be present in the zeolite of the precursor catalyst may include, but are not limited to, H, alkali metals, alkaline earth metals, transition metals, and any combination thereof.

The precursor catalyst can be formulated in a self-adhesive form without any binder. Alternatively, the precursor catalyst can be formulated with a binder material. The binder can withstand the temperature and other conditions used in the methylation reaction. In other words, the precursor catalyst can include (a) a zeolite with an MWW framework type, and optionally (b) a binder. Such binder materials can be active or inactive. Such binder materials can be synthetic and/or naturally occurring. Non-limiting examples of useful binders are clays (e.g., bentonite, kaolin), oxides such as aluminum oxide, silica, silica-alumina, zirconium oxide, titanium oxide, magnesium oxide, and mixtures, combinations, and complexes thereof. Binders can impart desired mechanical properties such as crushing strength to the pro-drive catalyst and/or help form (e.g., extrude) the pro-drive catalyst. Inactive binder materials also provide the role of diluents for active zeolites. In certain embodiments, the pro-drive catalyst may comprise 10 wt%, 20 wt%, 30 wt%, to 40 wt%, 50 wt%, 60 wt%, to 70 wt%, 80 wt%, or 90 wt% of MWW framework zeolite, based on the total weight of the pro-drive catalyst, and the remainder is the binder material. In addition to the MWW framework zeolite, the pro-drive catalyst may also arbitrarily comprise other zeolites.

The precursor catalyst can be modified by contacting the catalyst with a modifier, such as a silicon-containing reagent, a coke former, a large N-containing organic molecule, or a combination thereof, either prior to introduction into the methylation reactor (ex situ) or in situ in the methylation reactor. Each of these modifiers and the associated modification methods are discussed in further detail herein. Silica Modification of Precursor Catalysts

The precursor catalyst may be modified with silica. Silica modification may be achieved by subjecting the precursor catalyst to one or more treatments with a silicon-containing reagent (e.g., an organosilicon compound in a liquid carrier), each treatment followed by calcining the treated material in an oxygen-containing atmosphere (e.g., air). In the case where the precursor catalyst to be silica-modified contains a binder, it is preferred to use a non-acidic binder, such as silica.

The organosilicon compound used to modify the precursor catalyst can be, for example, polysilicones, siloxanes, silanes, or mixtures thereof. These organosilicon compounds can be solids in pure form, provided that they are soluble or otherwise convertible to liquid form when combined with a liquid carrier medium. The organosilicon compound can also be a liquid in pure form (e.g., tetraethyl orthosilicate, or TEOS). The molecular weight of the polysilicones, siloxanes, or silane compounds used as modifiers can be between 80 g/mol and 20,000 g/mol, and preferably in the range of about 150 g/mol to 10,000 g/mol.

Representative modified polysilicone compounds include dimethyl polysilicone, diethyl polysilicone, Benzyl polysiloxane, methyl hydropolysiloxane, ethyl hydropolysiloxane, phenyl hydropolysiloxane, methylethyl polysiloxane, phenylethyl polysiloxane, diphenyl polysiloxane, methyltrifluoropropyl polysiloxane, ethyltrifluoropropyl polysiloxane, polydimethyl polysiloxane, tetrachlorophenylmethyl polysiloxane, tetrachlorophenylethyl polysiloxane, tetrachlorophenyl hydropolysiloxane, tetrachlorophenylphenyl polysiloxane, methylvinyl polysiloxane, and ethylvinyl polysiloxane. The modified polysiloxane, siloxane, or silane compound need not be linear but may be cyclic, for example, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane, and octaphenylcyclotetrasiloxane. Mixtures of these compounds may also be used as modifiers, as may polysiloxanes having other functional groups.

Typically, the kinetic diameter of the organosilicon compound used to modify the precursor catalyst is larger than the pore size of the MWW framework to prevent the organosilicon compound from entering the zeolite pores.

Examples of organosilicon modifiers, particularly when the modifier is dissolved in an organic carrier or emulsified in an aqueous carrier, include, but are not limited to, dimethylphenylmethylpolysiloxane (e.g., Dow-550) and phenylmethylpolysiloxane (e.g., Dow-710). Dow-550 and Dow-710 are available from Dow Chemical Co., Midland, Mich.

The liquid carrier of the organosilicon compound can be an organic material, such as a linear, branched or cyclic hydrocarbon (e.g., an alkane such as heptane, octane, nonane, undecane, decane, or dodecane) having five or more, especially seven or more, carbon atoms per molecule, or a mixture thereof. The boiling point of the organic material (e.g., alkane) can be greater than about 70° C. A mixture of low-volatility organic materials, such as hydrocracker cycle oil, can be used as a carrier.

Typically, the precursor catalyst may be subjected to one or more treatments comprising contacting the precursor catalyst with an organosilicon compound, which may impregnate the precursor catalyst with the organosilicon compound.

Preferably, after each impregnation with the organosilicon compound, the catalyst is calcined at a temperature increase rate of 0.2°C/min to 5°C/min to a temperature greater than 200°C, but below the temperature at which the crystallinity of the zeolite is adversely affected. This calcination temperature will preferably be below 600°C, for example in the approximate range of 250°C to 600°C, and preferably in the approximate range of 350°C to 550°C. The duration of heating at the calcination temperature may be 1 hour to 24 hours (e.g., 2 hours to 6 hours).

After one or more treatments comprising (a) impregnation and (b) calcination, the precursor catalyst has become a methylated catalyst comprising (a) MWW framework-type zeolite and (b) silica on at least a portion of the outer surface of the zeolite.

The precursor catalyst may be modified to include silica on at least a portion of the zeolite surface (a) prior to introduction into the methylation reactor (ex situ) or (b) in situ in the methylation reactor before the methylation reaction occurs.

For example, in an ex situ process, the precursor catalyst may be modified with silica by contacting the precursor catalyst with at least one organosilicon compound in a liquid carrier and then calcining the silica-containing catalyst in an oxygen-containing atmosphere (e.g., air) under calcining conditions. As described above, the treatment with the organosilicon compound and subsequent calcination may occur multiple times in succession to obtain the desired amount of silica on the zeolite surface. The methylation catalyst having silica on the surface of the MWW framework-type zeolite may then be introduced into (or otherwise placed in) a methylation reactor and subsequently exposed to methylation reaction conditions (described further herein) in the presence of an aromatic feed and a methylating agent feed.

In another example, in an in-situ method, the precursor catalyst can be introduced into (or otherwise placed in) a methylation reactor. In the methylation reactor, the precursor catalyst can be modified with silica by contacting the precursor catalyst with at least one organosilicon compound in a liquid carrier and then calcining the silicon-containing catalyst in an oxygen-containing atmosphere (e.g., air) under calcining conditions. As described above, the treatment with the organosilicon compound and subsequent calcination can occur multiple times in succession to obtain a desired amount of silica on the zeolite surface. This method results in a methylation catalyst having silica on the surface of an MWW framework-type zeolite. While still in the methylation reactor, the methylation catalyst can be exposed to methylation reaction conditions in the presence of an aromatic feed and a methylating agent feed.

Without being bound by theory, it is believed that modifying the zeolite surface of the promotor catalyst with silica inactivates some acid sites and forms a surface shield, which modifies the catalytic activity of the zeolite, resulting in increased ortho-xylene selectivity compared to the unmodified promotor catalyst. The methylated catalyst having silica on the zeolite surface may contain at least 0.1 wt % added silica, based on the total weight of the methylated catalyst, or 0.1 wt % to 30 wt % added silica, or 1 wt % to 10 wt % added silica, or 5 wt % to 25 wt % added silica, or 10 wt % to 30 wt % added silica, based on the total weight of the MWW framework zeolite in the methylated catalyst. "Added silica" means silica introduced into the methylated catalyst as a result of silica modification. Coke-based catalyst modification

Coke upgrading typically involves contacting a precursor catalyst with a coke forming agent (e.g., a thermally decomposable organic material) under coke forming conditions, e.g., at an elevated temperature above the decomposition temperature of the organic material but below a temperature at which the crystallinity of the precursor catalyst or a portion thereof is adversely affected. Coke upgrading can occur naturally (e.g., when a methylation reaction occurs) and/or via the addition of the decomposable organic compound prior to or during the methylation reaction.

The contact temperature for coke upgrading (or coke deposition) may range from 200°C to 650°C (e.g., 375°C to 650°C, 300°C to 550°C, or 250°C to 400°C). The organic materials that may be used in this coke upgrading process may include a wide variety of materials, including, but not limited to, hydrocarbons (e.g., waxes, cycloalkanes, alkenes, cycloalkenes, aromatics, the like, and any combination thereof), oxygen-containing organic materials (e.g., alcohols, aldehydes, ethers, ketones, phenols, the like, and any combination thereof), and heterocyclic compounds (e.g., thiophene, pyrrole, pyridine, the like, and any combination thereof). Hydrogen co-feed may be used to delay excessive coke accumulation.

The precursor catalyst can be modified with coke on at least a portion of the zeolite surface (a) prior to introduction into the methylation reactor (ex situ), (b) in situ in the methylation reactor before the methylation reaction occurs, (c) in situ in the methylation reactor during the methylation reaction, or (d) any combination thereof.

For example, in an ex situ process, the precursor catalyst can be coke-modified by contacting the precursor catalyst with a decomposable organic compound under coking conditions, resulting in coke deposition on the zeolite surface of the precursor catalyst. If sufficient coke deposition is obtained ex situ for the desired ortho-xylene selectivity, the resulting methylated catalyst can be exposed to methylation reaction conditions in the presence of an aromatic feed and a methylating agent feed. During the methylation reaction, further coke upgrading can be performed, for example, if the selectivity to ortho-xylene decreases below a threshold.

Alternatively, if additional coke deposition is desired in addition to ex situ coke deposition, a precursor catalyst having coke on the surface of the MWW framework-type zeolite may be introduced into (or otherwise placed in) the methylation reactor. Once in the methylation reactor, further coke deposition may occur prior to and/or during exposure to methylation reaction conditions in the presence of an aromatic feed and a methylating agent feed.

In another example, in an in-situ process, the precursor catalyst may be introduced into (or otherwise placed in) a methylation reactor. In the methylation reactor, the precursor catalyst may be coked by contacting the precursor catalyst with a decomposable organic compound under coking conditions, resulting in coke deposition on the zeolite surface of the precursor catalyst. The coke modification may occur before and/or during the methylation reaction.

Without being limited by theory, it is believed that the modification step can be repeated multiple times to deposit coke on the zeolite surface and partially passivate the catalytically active sites of the methylated catalyst, which can increase the ortho-xylene yield. The coke-modified methylated catalyst can contain at least 1 wt% coke based on the total weight of the methylated catalyst, or 1 wt% to 40 wt% coke, or 1 wt% to 20 wt% coke, or 10 wt% to 30 wt% coke, or 20 wt% to 40 wt% coke. Adsorption-based catalyst modification

Adsorption modification typically involves contacting a catalyst with a stream containing large N-containing organic molecules at a temperature effective to adsorb a plurality of the large N-containing organic molecules onto at least a portion of the outer surface of the zeolite within the precursor catalyst.

Adsorption modification of the precursor catalyst can be physical (e.g., physical adsorption), chemical (e.g., chemical adsorption), or a combination thereof. Typically, the large N-containing organic molecules used to modify the precursor catalyst have a kinetic diameter larger than the MWW framework pore size to prevent such molecules from entering the zeolite pores.

Examples of large N-containing organic molecules may include, but are not limited to, 2,4-dimethylquinoline, collinine, di-tert-butyl-pyridine, the like, and combinations thereof.

Large N-containing organic molecules may include N, C, H, and optionally O, and may have a molecular weight of ≥ 100 g/mol (eg, 100 g/mol to 500 g/mol).

Adsorption of large N-containing organic molecules may include contacting the precursor catalyst with the large N-containing organic molecules at a temperature ranging from 200° C. to 400° C. (e.g., 200° C. to 350° C., 250° C. to 400° C.) The precursor catalyst may be exposed to the large N-containing organic molecules for 1 hour to 24 hours (e.g., 2 hours to 6 hours).

The modification step, which can be repeated multiple times, partially passivates the catalytically active sites of the methylation catalyst and can increase the ortho-xylene yield.

The precursor catalyst can be modified to contain large N-containing organic molecules adsorbed onto at least a portion of the zeolite surface (a) prior to introduction into the methylation reactor (ex situ), (b) in situ in the methylation reactor before the methylation reaction occurs, (c) in situ in the methylation reactor during the methylation reaction, or (d) any combination thereof.

For example, in an ex situ method, the precursor catalyst can be contacted with large N-containing organic molecules under suitable adsorption conditions. As described above, the adsorption of large N-containing organic molecules can be repeated multiple times to obtain a desired amount of adsorbed large N-containing organic molecules on the zeolite surface. The methylation catalyst with large N-containing organic molecules adsorbed on the surface of the MWW framework-type zeolite can then be introduced into (or otherwise placed in) a methylation reactor, and then the methylation catalyst is exposed to methylation reaction conditions (described further herein) in the presence of an aromatic feed and a methylating agent feed.

Alternatively, if additional adsorption of large N-containing organic molecules is desired in addition to ex situ adsorption, a precursor catalyst having large N-containing organic molecules adsorbed on the surface of the MWW framework-type zeolite can be introduced into (or otherwise placed in) the methylation reactor. Once in the methylation reactor, further adsorption of large N-containing organic molecules can occur prior to and/or during exposure to methylation reaction conditions in the presence of an aromatic feed and a methylating agent feed.

In another example, in an in-situ method, a precursor catalyst may be introduced into (or otherwise placed in) a methylation reactor. In the methylation reactor, the precursor catalyst may be contacted with large N-containing organic molecules under adsorption conditions such that the large N-containing organic molecules are adsorbed on the zeolite surface of the precursor catalyst. The modification of the large N-containing organic molecules may occur before and/or during the methylation reaction.

When adsorption of large N-containing organic molecules occurs during the methylation reaction, the large N-containing organic molecules may be present at 1 volume % to 10 volume %, or 1 volume % to 5 volume %, or 3 volume % to 10 volume %, based on the total volume of the combined aromatic feed, methylating agent feed, and large N-containing organic molecules.

Without being bound by theory, it is believed that adsorption of large N-containing organic molecules onto the precursor catalyst deactivates some acidic sites and forms a surface shield, which modifies the catalytic activity of the methylation catalyst to provide increased ortho-xylene selectivity during the methylation reaction. Steam Modification

Steam modification typically involves contacting a catalyst with the steam. The contacting may be at a temperature of at least 200°C, preferably 200°C to 600°C, and optimally 200°C to 400°C, and for a period of 10 minutes to 10 hours or more, preferably 30 minutes to 5 hours, such as 30 minutes to 2 hours. The partial pressure of the steam may be at least 12 psia (83 kPaa), such as about 15 psia (about 104 kPaa) or more. The steam may be in a carrier gas (e.g., hydrogen). The exposure rate of the steam may be 1 gram/hour (g/h) to 15 g/h, preferably 2 g/h to 10 g/h, and optimally 4 g/h to 8 g/h.

The precursor catalyst may be modified with steam (a) prior to introduction into the methylation reactor (ex situ) and/or (b) in situ in the methylation reactor before the methylation reaction occurs.

For example, in an ex situ process, the precursor catalyst may be contacted with steam under steam treatment conditions. The methylated catalyst (the precursor catalyst modified by steam) may then be introduced into (or otherwise placed in) a methylation reactor and subsequently exposed to methylation reaction conditions (described further herein) in the presence of an aromatic feed and a methylating agent feed.

In another example, in an in-situ method, a precursor catalyst may be introduced into (or otherwise placed in) a methylation reactor. In the methylation reactor, the precursor catalyst may be contacted with steam under steam treatment conditions. This method results in a methylated catalyst (in this example, a steam-modified precursor catalyst). While still in the methylation reactor, the methylated catalyst may be exposed to methylation reaction conditions in the presence of an aromatic feed and a methylating agent feed.

Without being bound by theory, it is believed that exposing the precursor catalyst zeolite surface to steam deactivates some of the acid sites and forms a surface shield that modifies the catalytic activity of the zeolite to provide increased ortho-xylene selectivity. Methylation Process

The feed of the method disclosed herein may include: an aromatic feed including benzene and/or toluene, and a methylating agent feed including one or more of methanol and dimethyl ether. Any suitable refined aromatic feed can be used as a source of benzene and/or toluene. In some embodiments, the aromatic feed includes toluene having a concentration of ≥ 90 wt % (e.g., ≥ 92 wt %, ≥ 94 wt %, ≥ 95 wt %, ≥ 96 wt %, ≥ 98 wt %, or even ≥ 99 wt %), based on the total weight of the aromatic feed. In some embodiments, the aromatic feed may be pretreated to remove catalyst poisons, such as nitrogen and sulfur compounds. The aromatic feed may be fed into the methylation reactor as a single or multiple streams having the same or different compositions through one or more feed inlets. The methylating agent feed may be fed into the methylation reactor as a single or multiple streams having the same or different compositions through one or more feed inlets. Alternatively or additionally, at least a portion of the aromatic feed and at least a portion of the methylating agent feed may be combined and then fed into the methylation reactor as a single or multiple streams through one or more inlets.

The methylation process of the present disclosure can be advantageously carried out at a relatively low reactor (methylation reactor) temperature, such as ≤ 500°C, such as ≤ 475°C, ≤ 450°C, ≤ 425°C, or ≤ 400°C. The process can be carried out in a methylation reactor at a temperature of ≥ 200°C, such as ≥ 250°C, or ≥ 300°C, which has been found to provide commercially viable methylation reaction rates. In terms of range, the process can be carried out at a temperature ranging from 200°C to 500°C, such as 275°C to 475°C, 300°C to 450°C, or 250°C to 400°C. Such low temperature reactions can be particularly useful for MWW framework-type zeolites. Such low temperature reactions can be particularly advantageous in the presence of a fixed bed of methylation catalyst in the methylation reactor. The ability of the disclosed process to operate at low temperatures has many advantages over conventional benzene/toluene methylation processes at temperatures above 500° C., including, for example, higher energy efficiency, longer catalyst life, fewer by-product types, and smaller amounts of by-products that would otherwise be produced at higher temperatures.

The operating pressure in the methylation reactor (in the reactor or methylation reactor) can vary in a wide range, for example, from ≥ 100 kPa, such as ≥ 1000 kPa, ≥ 1500 kPa, ≥ 2000 kPa, ≥ 3000 kPa, or ≥ 3500 kPa, to ≤ 8500 kPa, such as ≤ 7000 kPa, or ≤ 6000 kPa. For example, the operating pressure can range from 700 kPa to 7000 kPa, such as 1000 kPa to 6000 kPa, or 2000 kPa to 5000 kPa. In at least one embodiment, the combination of high pressure (e.g., pressure of 1500 kPa to 4500 kPa or even closer to 8500 kPa) and low temperature (e.g., temperature of 250°C to 500°C) reduces the amount of light gas produced in the methylation reaction and can also reduce the catalyst aging rate.

The WHSV value based on the total aromatic feed and methylating agent feed can be, for example, in the range of 0.5 hr- ¹ to 50 hr ^-1 , such as 5 hr ^-1 to 15 hr ^-1 , 1 hr ^-1 to 10 hr ^-1 , or 5 hr ^-1 to 10 hr ^-1 , or 6.7 hr ^-1 to 10 hr ^-1 . In some embodiments, at least a portion of the aromatic feed, methylating agent feed, and/or methylated product mixture effluent can be present in the methylation reactor in the liquid phase. As described in more detail below, changes in WHSV may need to be coordinated with changes in temperature in order to maintain the desired conversion of benzene, toluene, methanol, and/or dimethyl ether.

The methylation reaction can be carried out in a methylation reactor, which can be any suitable reactor system, including, but not limited to, a fixed bed reactor, a moving bed reactor, a fluidized bed reactor, and/or a reactive distillation unit. In addition, a single methylation reaction zone or multiple methylation reaction zones may be included in the reactor. The methylation reactor may include a bed of methylation catalyst particles, wherein the particles have negligible movement relative to the bed (fixed bed). In addition, the injection of the methylating agent feed can be carried out at a single point in the methylation reactor or at multiple points spaced along the methylation reactor. The aromatic feed and the methylating agent feed can be premixed before entering the methylation reactor or mixed in the methylation reactor.

In some embodiments, the methylation reactor comprises a single or multiple fixed bed continuous flow reactors in a downflow mode, wherein the reactors can be arranged in series or in parallel. The methylation reactor may include a single or multiple catalyst beds in series and/or in parallel. The methylation catalyst bed may have various configurations such as: a single bed, several horizontal beds, several parallel filling tubes, multiple beds each in its own reactor shell, or multiple beds in a single reactor shell. In some embodiments, the fixed bed provides a uniform flow distribution over the entire width and length of the bed to utilize all catalysts. In at least one embodiment, the methylation reactor can provide heat transfer from the fixed bed to provide an effective method for controlling temperature.

The efficiency of a methylation reactor containing a fixed bed of methylation catalyst can be affected by the pressure drop across the fixed bed. The pressure drop depends on various factors, such as path length, methylation catalyst particle size, and pore size. Too much pressure drop can lead to channeling through the catalyst bed and poor efficiency. In some embodiments, the methylation reactor has a cylindrical geometry with axial flow through the catalyst bed.

Various designs of methylation reactors can be tailored to accommodate specific process conditions, such as pressure, temperature, and WHSV, which determines the volume and residence time that will provide the desired conversion rate.

The product of the methylation reaction, the methylation product mixture effluent, may include xylene, benzene and/or toluene (both residual and co-produced in the process), C9+ aromatics, co-produced water, and unreacted methanol and DME. Ortho-xylene may be present in the methylation product mixture effluent at least 27 wt % (e.g., at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt %), based on the total weight of xylene in the methylation product mixture effluent. Ortho-xylene may be present in the methylation product mixture effluent at 27 wt % to 90 wt % (e.g., 30 wt % to 90 wt %, 30 wt % to 60 wt %, 40 wt % to 70 wt %, 50 wt % to 80 wt %, or 60 wt % to 90 wt %), based on the total weight of xylene in the methylation product mixture effluent.

The temperature in the methylation reactor will affect the formation of byproducts, and temperatures below 500° C. can reduce the formation of light gases. In some embodiments, the methylation product mixture effluent contains ≤ 10 wt %, such as ≤ 5 wt %, ≤ 2 wt %, ≤ 1 wt %, or is substantially free of light gases produced by the decomposition of methanol to ethylene or other olefins.

DME, methanol, and/or toluene can be recovered by a separator system. The separator system may include one or more separation units. The separator system may include any suitable method for recovering a DME-rich logistics, a methanol-rich logistics, and/or a toluene-rich logistics from the methylation product mixture effluent. In some embodiments, the separator system includes a first recycle channel. In some embodiments, the first recycle channel is connected to the methylating agent feed or the methylation reactor inlet fluid. In some embodiments, the separator system includes a first separation unit, and the first separation unit can separate an aqueous phase and an oil phase. In some embodiments, the separator system includes a second separation unit, and the second separation unit can separate a DME-rich logistics from the oil phase. In some embodiments, the DME-rich logistics flows through the first recycle channel, and the first recycle channel can be connected to the second separation unit and the methylating agent feed or the methylating reactor inlet fluid. In another embodiment, the second separation unit separates the rich aromatics logistics from the oil phase. In some embodiments, the separation subsystem includes the third separation unit. The third separation unit can separate the rich aromatics logistics into a toluene-rich logistics and a xylene-rich logistics. In some embodiments, the toluene-rich logistics flows to the methylating agent feed or the methylating reactor inlet through the second recycle channel. In some embodiments, the separation subsystem includes the fourth separation unit, and the fourth separation unit can separate the aqueous phase into a water-rich logistics and a methanol-rich logistics. In at least one specific embodiment, the methanol-rich stream flows through a third recycle channel, which can be connected to a fourth separation unit and a methylating agent feed or a methylation reactor inlet fluid.

In some embodiments, the methylation product mixture effluent is separated into an aqueous phase and an oil phase in a first separation unit. The method of separating the aqueous phase from the oil phase can be accomplished by a coalescing plate separator, for example, as described in U.S. Patent Nos. 4,722,800 and 5,068,035; a centrifugal separator, for example, as described in U.S. Patent Nos. 4,175,040; 4,959,158; and 5,591,340; a hydrocyclone separator, for example, as described in U.S. Patent Nos. 4,428,839; 4,927,536; and 5,667,686; or other suitable methods. In some embodiments, the oil phase of the methylation product mixture effluent may contain at least 80% by weight of xylene. In some embodiments, the methylation product mixture effluent comprising an aqueous phase and an oil phase enters the first separation unit; the denser aqueous phase settles to the bottom of the upstream chamber and can be drawn from a drain pipe at the bottom. The lighter oil phase is located on top of the aqueous phase and can overflow the partition into the downstream chamber, which can then be drawn from the bottom of the downstream chamber.

After separation of aqueous phase, oil phase can be fed into second separation unit to separate rich DME logistics, rich aromatics logistics and methane or other byproducts. In some embodiments, this rich DME logistics can be separated with other products and byproducts in whole or in part, to be recycled by first recycle channel. In some embodiments, this rich DME logistics contains ≥ 50 wt %, ≥ 60 wt %, ≥ 70 wt %, ≥ 80 wt %, ≥ 90 wt %, ≥ 95 wt %, ≥ 98 wt % or ≥ 99 wt % DME, based on the gross weight of rich DME logistics. In some embodiments, the methylating agent feed contains ≥ 20 wt%, ≥ 40 wt%, ≥ 60 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt%, or ≥ 99 wt% of DME from a DME-rich stream, based on the total weight of DME in the methylating agent stream. In at least one embodiment, all of the DME in the methylating agent feed is obtained from a DME-rich stream.

In some embodiments, the second separation unit separates methane partially or completely from other products and byproducts. In at least one embodiment, methane is used as fuel gas.

In some embodiments, the second separation unit manufactures an aromatics-rich stream comprising C6 to C9+ aromatic products and by-products. In another embodiment, the second separation unit manufactures a stream of C9+ aromatics. In at least one embodiment, the stream of C9+ aromatics can be recycled to be mixed into a gasoline pool or to produce additional xylene by transalkylation with benzene and/or toluene. In some embodiments, the second separation unit manufactures an aromatics-rich stream comprising ≥ 50 wt%, ≥ 60 wt%, ≥ 70 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt% or ≥ 99 wt% of xylene, based on the gross weight of the aromatics-rich stream. In some embodiments, the aromatics-rich stream comprises ortho-xylene. In some embodiments, the aromatics-rich stream contains ≥ 50 wt%, ≥ 60 wt%, ≥ 70 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt%, or ≥ 99 wt% o-xylene, based on the total weight of the aromatics-rich stream.

In some embodiments, the second separation unit is a distillation system comprising one or more distillation columns. The distillation system can be operated at an increased pressure, such as ≥ 400 kPag, ≥ 500 kPag, ≥ 600 kPag, ≥ 700 kPag, ≥ 800 kPag, ≥ 900 kPag, such as 400 kPag to 1400 kPag, 600 kPag to 1300 kPag, 700 kPag to 1200 kPag, 800 kPag to 1100 kPag, or 900 kPag to 1000 kPag.

In some embodiments, the aromatics-rich stream is processed in the third separation unit and further separated into a xylene-rich stream and a toluene-rich stream that may contain benzene. A toluene-rich stream (to be recycled through the second recycle passage) comprising benzene and/or toluene may contain ≥ 50 wt%, ≥ 60 wt%, ≥ 70 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt%, or ≥ 99 wt% toluene, based on the gross weight of the toluene-rich stream. In another embodiment, the toluene-rich stream comprises benzene and toluene, and the combined weight % is ≥ 50 wt%, ≥ 60 wt%, ≥ 70 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt%, or ≥ 99 wt%, based on the gross weight of the toluene-rich stream. The xylene-rich stream may contain at least 27 wt % (e.g., at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt %, between 27 wt % and 90 wt %, between 30 wt % and 90 wt %, between 30 wt % and 60 wt %, between 40 wt % and 70 wt %, between 50 wt % and 80 wt %, or between 60 wt % and 90 wt %) of o-xylene, based on the total weight of the xylene-rich stream.

In some embodiments, the aqueous phase is transported to the fourth separation unit to separate the methanol-rich stream from the water-rich stream. In some embodiments, the methanol-rich stream to be recycled through the third recycle passage contains ≥ 50 wt%, ≥ 60 wt%, ≥ 70 wt%, ≥ 80 wt%, ≥ 90 wt%, ≥ 95 wt%, ≥ 98 wt%, or ≥ 99 wt% of methanol, based on the total weight of the methanol-rich stream. In some embodiments, the fourth separation unit is a distillation system, and exemplary systems are described in U.S. Patents Nos. 3,293,154 and 4,210,495. In other embodiments, the separation system used is a membrane separation system or an osmotic evaporation separation system.

In another embodiment, the DME-rich stream is combined with the methanol-rich stream to form a single recycle stream. In another embodiment, the toluene-rich stream, the DME-rich stream, and the methanol-rich stream are combined to form a single recycle stream.

FIG. 1 schematically illustrates a method for producing xylenes by methylating benzene and/or toluene with methanol and/or DME according to one embodiment of the present disclosure. A methylating agent feed 101 comprising methanol and/or DME is combined with an aromatic feed 103 comprising toluene and/or benzene in a fluid delivery line 105. The fluid delivery line 105 may include an agitator or other mixing device (not shown) to combine the methylating agent feed 101 and the aromatic feed 103 to form a combined feed. The combined feed is fed into a heat exchanger 109 via a line 107 to preheat the combined feed. The combined feed comprising a heated mixture of feed 101 and feed 103 is fed to heat exchanger 113 via line 111. Heat exchanger 113 may be used to heat or cool the combined feed as desired. The combined feed is then passed through line 115 to methylation reactor 119 via inlet 117. Line 115 may also include a pump or series of pumps (not shown) to maintain adequate pressure and WHSV in methylation reactor 119. Inlet 117 may accept one or more feeds or a stream comprising one or more recycle streams. The methylation reactor 119 may be a fixed or fluidized bed reactor containing a methylation catalyst (not shown) and operated under methylation reaction conditions, which may include a temperature below 500°C and an absolute pressure of ≥ 100 kPa. The methylation reactor 119 may have one or more methylation reactors (not shown) in which a methylation catalyst is present. The product of the methylation conditions in the methylation reactor (methylation product mixture effluent) may be a mixture of xylene, water, methanol, dimethyl ether, and by-products, and is fed from the methylation reactor 119 through outlet 121 to pipeline 123 , and finally fed to the heat exchanger 109 for cooling. The cooled methylated product mixture effluent is passed through pipeline 125 to heat exchanger 127 to be heated or cooled as needed to reach the desired temperature for separation, and then passed through pipeline 129 to separator system 131. Separator system 131 may contain one or more separation units (not shown). Separator system 131 can separate methane or other light gases, which can be removed via pipeline 133 and can be used as fuel gas (not shown).

The separation subsystem 131 can further separate the dimethyl ether-rich stream, which is then provided to the pipeline 135 , which can be recycled to the methylating agent feed 101 or the methylation reactor inlet 117. The pipeline 135 can include a pump or a compressor so that the DME-rich stream can enter the methylating agent feed or the methylation reactor at a desired pressure, and the combination of the pipeline and the pump or compressor is a first recycling channel. The first recycling channel may contain other combinations of pipelines and pumps or compressors (not shown) suitable for recycling DME to the methylation reactor 119 .

The separation subsystem 131 can further separate a toluene-rich stream 137 , which can contain benzene and can be recycled to the aromatic feed 103 or the methylation reactor inlet 117. The pipeline for the toluene-rich stream 137 can include a pump or a compressor so that the toluene-rich stream can enter the aromatic feed or the methylation reactor at a desired pressure; the combination of the pipeline and the pump or compressor is a second recycle channel. Furthermore, the separation can produce a xylene-rich stream, which is sent from pipeline 139 , and pipeline 139 can be connected to other systems for further processing (not shown). The xylene-rich stream can be fed to a separation system, such as a crystallizer or simulated moving bed adsorption chromatography, to recover a high purity para-xylene product and produce an ortho-xylene-rich stream (which may further comprise meta-xylene).

The separation subsystem 131 can further separate the methanol-rich stream, which is then provided to the pipeline 141 , which can be recycled to the methylating agent feed 101 or the methylation reactor inlet 117. The pipeline 141 can include a pump or a compressor so that the methanol-rich stream can enter the methylating agent feed or the methylation reactor at a desired pressure; the combination of the pipeline and the pump or compressor is a third recycle channel. The third recycle channel may contain other combinations of pipelines and pumps or compressors (not shown) suitable for recycling methanol to the methylation reactor 119 . Furthermore, the separation may produce a water-rich stream which is sent out from pipeline 143 , and pipeline 143 may be connected to other systems for further processing (not shown), including a wastewater purification system (not shown).

FIG2 schematically illustrates a method for producing xylenes by converting benzene/toluene by methylation with methanol/dimethyl ether according to a specific embodiment of the present disclosure. A methylating agent feed 201 comprising methanol and/or DME is combined with an aromatic feed 203 comprising toluene and/or benzene in a fluid transport line 205. The fluid transport line 205 may include an agitator or other mixing device (not shown) to fully combine the methylating agent feed 201 and the aromatic feed 203. The combined feed is transported to a heat exchanger 209 via a pipeline 207 to preheat the combined feed. The heated combined feed comprising a mixture of feed 201 and feed 203 is fed to a heat exchanger 213 via a pipeline 211 . The combined feed may be heated or cooled using a heat exchanger 213 as needed. The combined feed is then passed through line 215 , through inlet 217 , to methylation reactor 219. Line 215 may also include a pump or a series of pumps (not shown) to maintain adequate pressure and WHSV in methylation reactor 219. Inlet 217 may receive one or more feeds or a stream comprising one or more recycle streams. Methylation reactor 219 may be a fixed or fluidized bed reactor containing a methylation catalyst (not shown) and operated under methylation reaction conditions, which may include a temperature of ≤ 500°C and a pressure of ≥ 100 kPa. The methylation reactor 219 may have one or more methylation reactors (not shown) in which a methylation catalyst is present. The product of the methylation conditions in the methylation reactor (methylation product mixture effluent) may be a mixture of xylene, water, methanol, dimethyl ether, and by-products. The methylation product mixture effluent is transported from the methylation reactor 219 through outlet 221 to pipeline 223 , leading to heat exchanger 209 for cooling, and the cooled methylation product mixture effluent is passed through pipeline 225 to heat exchanger 227 to be heated or cooled as needed to reach the desired temperature for separation, and then through pipeline 229 to inlet 231 of the first separation unit 233 .

The first separation unit 233 separates the aqueous phase (water/methanol mixture) of the methylated product mixture effluent from the oil phase (the hydrocarbon portion of the methylated product mixture effluent). The first separation unit 233 can act by any suitable method for separating the aqueous phase and the oil phase, including simple phase separation, hydrocyclonic separation, or other suitable methods. The oil phase of the methylated product mixture effluent may contain xylene, methane, dimethyl ether, unreacted benzene or toluene, and other by-products. The hydrocarbon portion of the methylated product mixture effluent is passed through the outlet 235 through the pipeline 237 to the inlet 239 of the second separation unit 248. The aqueous phase is passed through the outlet 269 to the pipeline 271 .

The second separation unit 248 separates the oil phase into (i) a light gas portion comprising methane, which can be discharged into the fuel gas through pipeline 243 ; (ii) a dimethyl ether-rich stream, which passes through outlet 245 through pipeline 247 to pump 249 , through pipeline 251 and is recycled into the methylating agent feed 201 or the methylation reactor inlet 217 ; the combination of the pipeline and the pump or compressor is the first recycling channel; and (iii) an aromatics-rich stream comprising ortho-xylene, para-xylene, and meta-xylene, which can be removed through outlet 253 and pipeline 255 for further processing. Second separation unit 248 may be a distillation column operated at sufficient pressure to allow separation of dimethyl ether as a liquid without requiring a sufficiently high bottom temperature to cause decomposition of the partially methylated product mixture effluent.

The aromatics-rich stream through line 255 can be introduced into inlet 257 and enter the third separation unit 259 , where the aromatics-rich stream can be separated. The separation can produce a toluene-rich stream, which is sent from outlet 261 through line 263 and can be recycled to the aromatic feed 203 or the methylation reactor inlet 217. Line 263 can include a pump or a compressor so that the toluene-rich stream can enter the aromatic feed or the methylation reactor at a desired pressure, and the combination of the pipeline and the pump or compressor is a second recycling channel. Furthermore, the separation can produce a xylene-rich stream, which is sent from outlet 265 through line 267 , and line 267 can be connected to other systems for further processing (not shown).

The water phase from the first separation unit 233 can be passed through outlet 269 and through pipeline 271 to the inlet 273 of the fourth separation unit 275. The fourth separation unit 275 separates the water-rich stream and the methanol-rich stream. The fourth separation unit 275 can be acted by any suitable method for separating methanol and water, including distillation, osmotic evaporation, membrane separation, or other suitable methods. The water-rich stream can be further processed or disposed of through outlet 277 and pipeline 279. The methanol-rich stream can be sent from outlet 281 to pipeline 283 and pump 285. The methanol-rich stream can then be passed through pipeline 289 and introduced into the methylating agent feed 201 or the methylation reactor inlet 217 (not shown). Lines 283 and 289 may include additional pumps (in addition to pump 285 ) or compressors to return the methanol-rich stream to the methylating agent feed 201 or the methylation reactor inlet 217 at a desired pressure; the combination of the pipeline and the pump is a third recycle channel.

In order to facilitate a better understanding of the specific implementation of the present disclosure, the following examples of preferred or representative specific implementations are provided. The following examples should not be interpreted as limiting, or defining, the scope of the present invention. Examples

Comparative Example C1. Comparative process for producing ortho-xylene with near equilibrium selectivity by methylating an aromatic feed with a methylated feed in the presence of an unmodified precursor methylation catalyst. The MCM-49 based precursor catalyst was loaded into a reactor where the methylation reaction occurred at 600 psig, 350°C and 6.4 hr ^-1 WHSV with a 1:3 molar ratio of methanol to toluene feed. Over a test period of 0 to 4500 grams of feed per gram of catalyst, the ortho-xylene selectivity was measured in the range of about 20 wt % to about 26 wt %, close to equilibrium.

Example 1. An exemplary method for producing ortho-xylene with higher than equilibrium selectivity by methylating an aromatic feed with a methylated feed in the presence of an ex-situ modified methylated catalyst was performed. First, the MCM-49-based precursor catalyst of Example C1 was modified with a 20 wt % SiO ₂ coating. This catalyst was prepared by mixing tetraethyl orthosilicate (TEOS; 4.1 wt % SiO ₂ ; > 99.0 wt % purity, Sigma Aldrich) in n-hexane (97 wt % purity, Sigma Aldrich) at 80° C. with stirring for 1 hour. This step was repeated multiple times, resulting in a total concentration of 20 wt % SiO ₂ added to the methylated catalyst. The methylation catalyst was then loaded into a reactor where the methylation reaction occurred at 600 psig, 350°C, and 6.4 hr ^-1 WHSV, with a 1:3 molar ratio of methanol to toluene feed. FIG3A shows the toluene conversion, and FIG3B shows the xylene isomer selectivity based on the total weight of xylene produced. As seen in FIG3B, the selectivity for ortho-xylene in the methylation product mixture effluent is greater than the 40% mark, which is significantly better than Comparative Example C1.

Example 2. An exemplary method for converting an aromatic feed by methylation with a methylated feed in the presence of an in-situ modified methylation catalyst to produce ortho-xylene with a selectivity higher than equilibrium was performed. First, the MCM-49-based precursor catalyst of Example C1 was loaded into a reactor and modified to form a methylated catalyst by contacting the precursor catalyst with 2,4-dimethylquinolinone at 350°C. The methylated catalyst was then used in a methylation reaction with a toluene feed and a methanol feed at 600 psig, 350°C, and 15.5 hr ^-1 WHSV, and having a molar ratio of methanol to toluene of 1:3. Figure 4A shows the toluene conversion, and Figure 4B shows the xylene isomer selectivity based on the total weight of xylene produced. As seen in Figure 4B, the selectivity for o-xylene in the methylation product mixture effluent was greater than the 70% mark, which was significantly better than that of Comparative Example C1.

Example 3. MCM-49 and ZSM-5 catalysts were exposed to conditions such that coke would be deposited on the surfaces of the catalysts. As coke was deposited, the selectivity of the MCM-49 catalyst to ortho-xylene increased from less than 24% to about 32%. The selectivity of the ZSM-5 catalyst to ortho-xylene decreased from about 32% to about 22%. Non-limiting illustrative embodiments

The present disclosure may further include the following non-limiting specific implementation aspects:

A1. A method comprising: contacting an aromatic feed with a methylating agent feed in the presence of a methylation catalyst in a methylation reactor under methylation reaction conditions to produce a methylation product mixture effluent leaving the methylation reactor, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, the methylation catalyst comprises a modified zeolite, the modified zeolite comprises (a) an MWW framework-type zeolite and (b) a surface modifier on at least a portion of the outer surface of the zeolite, and the methylation product mixture effluent comprises ortho-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

A2. The method of A1, wherein the methylation product mixture effluent comprises the o-xylene at a concentration of at least 30 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

A3. The method of A1 or A2, wherein the surface modifier comprises: silica, large N-containing organic molecules, coke, or any combination thereof.

A4. The method of any one of A1 to A3, wherein the surface modifier at least partially passivates a plurality of acid sites on the outer surface of the zeolite.

A5. The method of any one of A1 to A4, wherein the surface modifier comprises silica.

A6. The method of A5, wherein the methylation catalyst is produced by a method comprising: providing a precursor catalyst comprising the zeolite; and subjecting the precursor catalyst to one or more treatments comprising contacting the precursor catalyst with an organosilicon compound, wherein each treatment is followed by calcining the precursor catalyst to produce the methylation catalyst.

A7. The method of A6, wherein the organic silicon compound comprises polysilicon, siloxane, and/or silane.

A8. The method of A6, wherein the organic silicon compound comprises at least one of the following: dimethyl polysilicone, diethyl polysilicone, benzyl polysilicone, methyl hydropolysilicone, ethyl hydropolysilicone, phenyl hydropolysilicone, methylethyl polysilicone, phenylethyl polysilicone, diphenyl polysilicone, methyltrifluoropropyl polysilicone, ethyltrifluoropropyl polysilicone, polydimethyl polysilicone, tetrachlorophenylmethyl polysilicone, tetrachlorophenylethyl polysilicone, tetrachlorophenyl hydropolysilicone, tetrachlorophenyl phenyl polysilicone, methylvinyl polysilicone, and ethylvinyl polysilicone.

A9. The method of any one of A1 to A8, wherein the surface modifier comprises a large N-containing organic molecule.

A10. The method of A9, wherein the large N-containing organic molecule comprises 2,4-dimethylquinoline, collinaline, and/or di-tert-butyl-pyridine.

A11. The method of A9, further comprising: providing a precursor catalyst comprising the zeolite in the methylation reactor; and contacting the precursor catalyst with the large N-containing organic molecule to produce the methylation catalyst.

A12. The method of A11, wherein the contacting of the precursor catalyst with the large N-containing organic molecule occurs during at least a portion of the contacting of the aromatic feed with the methylating agent feed.

A13. The method of A11, wherein the contacting of the precursor catalyst with the large N-containing organic molecule occurs before the contacting of the aromatic feed with the methylating agent feed and, optionally, during at least a portion of the contacting of the aromatic feed with the methylating agent feed.

A14. The method of any one of A1 to A13, wherein the surface modifier is coke.

A15. The method of A14 further comprises: providing a pre-propellant catalyst comprising the zeolite; and contacting the pre-propellant catalyst with a thermally decomposable organic compound at a high temperature at or above the decomposition temperature of the thermally decomposable organic compound to deposit coke on the surface of the zeolite and produce the methylated catalyst.

A16. The method of A15, wherein the precursor catalyst is provided in the methylation reactor before the precursor catalyst is contacted with the thermally decomposable organic compound.

A17. The method of A15, further comprising: adding the precursor catalyst to the methylation reactor before the aromatic feed and the methylating agent feed are contacted in the presence of the methylation catalyst.

A18. The method of any one of A1 to A17, wherein the methylation reaction conditions comprise a temperature in the range of 200° C. to 500° C. and an absolute pressure in the range of 700 kPa to 8,500 kPa.

A19. The method of A18, wherein the methylation reaction conditions comprise a temperature of 250°C to 450°C.

A20. The method of A18, wherein the methylation reaction conditions comprise an absolute pressure in the range of 1,500 kPa to 6,000 kPa.

A21. The method of A18, wherein the methylation reaction conditions comprise conditions that cause the methylation reaction to occur in a supercritical phase.

A22. The method of any one of A1 to A21, wherein the zeolite comprises MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, or a mixture of two or more thereof.

A23. The method of any one of A1 to A22, further comprising: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation.

A24. The method of any one of A1 to A23, further comprising: separating a p-xylene-rich p-xylene stream from the methylation product mixture effluent by fractionation.

B1. A method comprising: providing a precursor catalyst comprising a zeolite having an MWW framework structure; loading the precursor catalyst in a methylation reactor; contacting the precursor catalyst in the methylation reactor with a surface modifier to produce a methylation catalyst comprising a modified zeolite, the modified zeolite comprising the surface modifier on at least a portion of the outer surface of the zeolite; and subjecting the methylation catalyst to a methylation reaction under methylation reaction conditions. The methylation catalyst in the reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

B2. The method of B1, wherein the surface modifier comprises a large N-containing compound, and wherein contacting of the surface modifier with the precursor catalyst occurs before, and optionally during, contacting of the methylating catalyst with the aromatic feed and the methylating agent feed.

B3. The method of B2, wherein the large N-containing organic molecule comprises 2,4-dimethylquinoline, collinaline, and/or di-tert-butyl-pyridine.

B4. The method of any one of B1 to B3, wherein the surface modifier comprises coke, and wherein the method further comprises contacting the precursor catalyst with a thermally decomposable organic compound at a decomposition temperature of the thermally decomposable organic compound or a high temperature above the decomposition temperature to deposit the coke on the surface of the zeolite and produce the methylated catalyst.

B5. The method of any one of B1 to B4, wherein the methylation product mixture effluent comprises the o-xylene at a concentration of at least 40 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

B6. The method of any one of B1 to B5, wherein the surface modifier at least partially passivates a plurality of acid sites on the outer surface of the zeolite.

B7. The method of any one of B1 to B6, wherein the methylation reaction conditions comprise a temperature in the range of 200° C. to 500° C. and an absolute pressure in the range of 700 kPa to 8,500 kPa.

B8. The method of B7, wherein the methylation reaction conditions comprise a temperature of 250°C to 450°C.

B9. The method of B7, wherein the methylation reaction conditions comprise an absolute pressure in the range of 1,500 kPa to 6,000 kPa.

B10. The method of B7, wherein the methylation reaction conditions comprise conditions that cause the methylation reaction to occur in a supercritical phase.

B11. The method of any one of B1 to B10, wherein the zeolite comprises MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, or a mixture of two or more thereof.

B12. The method of any one of B1 to B11, further comprising: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation.

B13. The method of any one of B1 to B12, further comprising: separating a p-xylene-rich p-xylene stream from the methylation product mixture effluent by fractionation.

C1. A method comprising: providing a precursor catalyst comprising a zeolite having an MWW framework structure; loading the precursor catalyst in a methylation reactor; contacting the precursor catalyst in the methylation reactor with water to produce a methylation catalyst comprising a modified zeolite, the modified zeolite comprising neutralized acid groups on at least a portion of the outer surface of the zeolite; and subjecting the methylation reactor to a methylation reaction under methylation reaction conditions. The methylation catalyst in the reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene in a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

C2. The method of C1, wherein the methylation product mixture effluent comprises the o-xylene at a concentration of at least 30 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

C3. The method of C1 or C2, wherein the methylation reaction conditions comprise a temperature in the range of 200° C. to 500° C. and an absolute pressure in the range of 700 kPa to 8,500 kPa.

C4. The method of C3, wherein the methylation reaction conditions comprise a temperature of 250°C to 450°C.

C5. The method of C3, wherein the methylation reaction conditions comprise an absolute pressure in the range of 1,500 kPa to 6,000 kPa.

C6. The method of C3, wherein the methylation reaction conditions comprise conditions that cause the methylation reaction to occur in a supercritical phase.

C7. The method of any one of C1 to C6, wherein the zeolite comprises MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, or a mixture of two or more thereof.

C8. The method of any one of C1 to C7, further comprising: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation.

C9. The method of any one of C1 to C8, further comprising: separating a p-xylene-rich p-xylene stream from the methylation product mixture effluent by fractionation.

D1. A method comprising: providing a precursor catalyst comprising a zeolite having an MWW framework structure; subjecting the precursor catalyst to one or more treatments comprising contacting the precursor catalyst with an organosilicon compound, wherein each treatment is followed by calcining the precursor catalyst to produce the methylated catalyst, wherein the surface modifier is silica; loading the methylated catalyst into a methylation reactor; and subjecting the precursor catalyst to a methylation reactor under methylation reaction conditions. The methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

D2. The method of D1, wherein the methylation product mixture effluent comprises the o-xylene at a concentration of at least 30 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

D3. The method of D1 or D2, wherein the surface modifier at least partially passivates a plurality of acid sites on the outer surface of the zeolite.

D4. The method of any one of D1 to D3, wherein the organic silicon compound comprises polysilicon, siloxane, and/or silane.

D5. The method of any one of D1 to D4, wherein the organosilicon compound comprises dimethyl polysilicone, diethyl polysilicone, phenyl methyl polysilicone, methyl hydropolysilicone, ethyl hydropolysilicone, phenyl hydropolysilicone, methyl ethyl polysilicone, phenyl ethyl polysilicone, diphenyl polysilicone, methyl trifluoropropyl polysilicone, ethyl trifluoropropyl polysilicone, polydimethyl polysilicone, tetrachlorophenyl methyl polysilicone, tetrachlorophenyl ethyl polysilicone, tetrachlorophenyl hydropolysilicone, tetrachlorophenyl phenyl polysilicone, methyl vinyl polysilicone, and/or ethyl vinyl polysilicone.

D6. The method of any one of D1 to D5, wherein the methylation reaction conditions comprise a temperature in the range of 200° C. to 500° C. and an absolute pressure in the range of 700 kPa to 8,500 kPa.

D7. The method of D6, wherein the methylation reaction conditions comprise a temperature of 250°C to 450°C.

D8. The method of D6, wherein the methylation reaction conditions comprise an absolute pressure in the range of 1,500 kPa to 6,000 kPa.

D9. The method of D6, wherein the methylation reaction conditions comprise conditions that cause the methylation reaction to occur in a supercritical phase.

D10. The method of any one of D1 to D9, wherein the zeolite comprises MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, or a mixture of two or more thereof.

D11. The method of any one of D1 to D10, further comprising: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation.

D12. The method of any one of D1 to D11, further comprising: separating a p-xylene-rich p-xylene stream from the methylation product mixture effluent by fractionation.

E1. A method comprising: providing a precursor catalyst comprising a zeolite having an MWW framework structure; contacting the precursor catalyst with a thermally decomposable organic compound at a decomposition temperature of the thermally decomposable organic compound or a high temperature above the decomposition temperature to deposit coke on the surface of the zeolite and produce a methylation catalyst; loading the methylation catalyst in a methylation reactor; and, under methylation reaction conditions, subjecting the methylation catalyst to a methylation reaction. The methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

E2. The method of E1, wherein the methylation product mixture effluent comprises the o-xylene at a concentration of at least 30 weight percent, based on the total weight of xylene in the methylation product mixture effluent.

E3. The method of E1 or E2, wherein the methylation reaction conditions comprise a temperature in the range of 200° C. to 500° C. and an absolute pressure in the range of 700 kPa to 8,500 kPa.

E4. The method of E3, wherein the methylation reaction conditions comprise a temperature of 250°C to 450°C.

E5. The method of E3, wherein the methylation reaction conditions comprise an absolute pressure in the range of 1,500 kPa to 6,000 kPa.

E6. The method of E3, wherein the methylation reaction conditions comprise conditions that cause the methylation reaction to occur in a supercritical phase.

E7. The method of any one of E1 to E6, wherein the zeolite comprises MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, UCB-3, or a mixture of two or more thereof.

E8. The method of any one of E1 to E7, further comprising: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation.

E9. The method of any one of E1 to E8, further comprising: separating a para-xylene-rich para-xylene stream from the methylation product mixture effluent by fractionation.

One or more illustrative embodiments incorporating one or more elements of the invention are presented herein. For the sake of clarity, not all features of physical implementations are described or shown in this application. It is understood that in the process of developing physical embodiments incorporating one or more elements of the invention, many implementation-specific decisions must be made to achieve the developer's goals, such as complying with system-related, business-related, government-related and other restrictions, which vary from implementation to implementation and from time to time. Although the developer's efforts may be time-consuming, such efforts will be routine work for those skilled in the art and who benefit from this disclosure.

Although compositions and methods are described herein as "comprising" various ingredients or steps, such compositions and methods may also "consist essentially of" or "consist of" the various ingredients and steps.

Many changes, modifications, and variations will be apparent to those skilled in the art from the foregoing description without departing from the spirit and scope of the present disclosure, and when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

101: Methylating agent feed/feed 103: Aromatic feed/feed 105: Fluid transport pipeline 107: Pipeline 109: Heat exchanger 111: Pipeline 113: Heat exchanger 115: Pipeline 117: Inlet 119: Methylation reactor 121: Outlet 123: Pipeline 125: Pipeline 127: Heat exchanger 129: Pipeline 131: Separation system 133: Pipeline 135: Pipeline 137: Toluene-rich stream 139: Pipeline 141: Pipeline 143: Pipeline 201: Methylating agent feed/feed 203: Aromatic feed/feed 205: Fluid transport pipeline 207: Pipeline 209: Heat exchanger 211: Pipeline 213: Heat exchanger 215: Pipeline 217: Inlet 219: Methylation reactor 221: Outlet 223: Pipeline 225: Pipeline 227: Heat exchanger 229: Pipeline 231: Inlet 233: First separation unit 235: Outlet 237: Pipeline 239: Inlet 241: Second separation unit 243: Pipeline 245: Outlet 247: Pipeline 248: Second separation unit 249: Pump 251: Pipeline 253: Outlet 255: Pipeline 257: Inlet 259: Third separation unit 261: Outlet 263: Pipeline 265: Outlet 267: Pipeline 269: Outlet 271: Pipeline 273: Inlet 275: Fourth separation unit 277: Outlet 279: Pipeline 281: Outlet 283: Pipeline 285: Pump 289: Pipeline

To assist one of ordinary skill in the relevant art in making and using the subject matter herein, reference is made to the accompanying drawings. The following drawings are included to illustrate certain aspects of the present disclosure and should not be construed as the only configuration. The disclosed subject matter is capable of considerable modification, alteration, combination, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[ FIG. 1 ] schematically illustrates a method for producing xylene by methylating benzene and/or toluene with methanol and/or DME according to a specific embodiment of the present disclosure.

[ FIG. 2 ] schematically illustrates a method for producing xylene by methylating benzene/toluene with methanol/dimethyl ether according to a specific embodiment of the present disclosure.

[FIG. 3A] is a graph showing toluene conversion, and [FIG. 3B] is a graph showing xylene isomer selectivity based on the total weight of xylene produced.

[FIG. 4A] is a graph showing toluene conversion, and [FIG. 4B] is a graph showing xylene isomer selectivity based on the total weight of xylene produced.

101: Methylating agent feed/feed

103: Aromatic feed/feed

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109: Heat exchanger

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113: Heat exchanger

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117:Entrance

119:Methylation reactor

121:Exit

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127: Heat exchanger

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131: Separation system

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137: Toluene-rich logistics

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Claims (20)

A method for producing a xylene product rich in ortho-xylene, comprising: contacting an aromatic feed with a methylating agent feed in the presence of a methylation catalyst in a methylation reactor under methylation reaction conditions to produce a methylation product mixture effluent leaving the methylation reactor, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, the methylation catalyst comprises a modified zeolite, the modified zeolite comprises (a) an MWW framework-type zeolite and (b) a surface modifier on at least a portion of the outer surface of the zeolite, and the methylation product mixture effluent comprises ortho-xylene at a concentration of at least 27 weight percent, based on the total weight of xylene in the methylation product mixture effluent. The method of claim 1, wherein the methylation product mixture effluent contains the o-xylene at a concentration of at least 30 weight percent, based on the total weight of xylene in the methylation product mixture effluent. The method of claim 1, wherein the surface modifier comprises: silica, large N-containing organic molecules, coke, or any combination thereof. A method as claimed in claim 1, wherein the surface modifier at least partially passivates a plurality of acid sites on the outer surface of the zeolite. The method of claim 1, wherein the surface modifier comprises silica. The method of claim 5, wherein the methylation catalyst is produced by a method comprising: providing a precursor catalyst comprising the zeolite; and subjecting the precursor catalyst to one or more treatments comprising contacting the precursor catalyst with an organosilicon compound, wherein each treatment is followed by calcining the precursor catalyst to produce the methylation catalyst. The method of claim 6, wherein the organic silicon compound comprises polysilicon, siloxane, and/or silane. A method as claimed in claim 1, wherein the surface modifier comprises large N-containing organic molecules. The method of claim 8, wherein the large N-containing organic molecule comprises 2,4-dimethylquinoline, collinaline, and/or di-tert-butyl-pyridine. The method of claim 8 further comprises: providing a precursor catalyst comprising the zeolite in the methylation reactor; and contacting the precursor catalyst with the large N-containing organic molecule to produce the methylation catalyst. The method of claim 10, wherein the contact between the precursor catalyst and the large N-containing organic molecule occurs during at least a portion of the contact between the aromatic feed and the methylating agent feed. The method of claim 10, wherein the contacting of the precursor catalyst with the large N-containing organic molecule occurs before the contacting of the aromatic feed with the methylating agent feed and, optionally, during at least a portion of the contacting of the aromatic feed with the methylating agent feed. The method of claim 1, wherein the surface modifier is coke. The method of claim 13 further comprises: providing a precursor catalyst comprising the zeolite; and contacting the precursor catalyst with a thermally decomposable organic compound at a high temperature at or above the decomposition temperature of the thermally decomposable organic compound to deposit coke on the surface of the zeolite and produce the methylated catalyst. The method of claim 14, wherein the precursor catalyst is provided in the methylation reactor before the precursor catalyst is contacted with the thermally decomposable organic compound. The method of claim 14 further comprises: adding the precursor catalyst to the methylation reactor before the aromatic feed and the methylating agent feed are contacted in the presence of the methylation catalyst. The method of claim 1, wherein the methylation reaction conditions include a temperature in the range of 200°C to 500°C and an absolute pressure in the range of 700 kPa to 8,500 kPa. The method of claim 1, wherein the methylation reaction conditions include conditions that cause the methylation reaction to occur in a supercritical phase. The method of claim 1 further comprises: separating an o-xylene-rich o-xylene stream from the methylation product mixture effluent by fractionation. A method for producing a xylene product rich in ortho-xylene, comprising: providing a precursor catalyst comprising a zeolite having an MWW framework structure; loading the precursor catalyst in a methylation reactor; contacting the precursor catalyst in the methylation reactor with a surface modifier to produce a methylation catalyst comprising a modified zeolite, the modified zeolite comprising the surface modifier on at least a portion of the outer surface of the zeolite; and Under the conditions, the methylation catalyst in the methylation reactor is contacted with an aromatic feed and a methylating agent feed to produce a methylation product mixture effluent, wherein the aromatic feed comprises benzene and/or toluene, the methylating agent feed comprises methanol and/or dimethyl ether, and the methylation product mixture effluent comprises o-xylene at a concentration of at least 27% by weight, based on the total weight of xylene in the methylation product mixture effluent.

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