Catalyst and process for the production of para-xylene
AssigneeExxonMobil Chemical Patents Inc.
InventorsNikolaos Soultanidis, Todd E. Detjen, Scott J. Weigel
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Abstract
A fluidized bed process for producing para-xylene via toluene and/or benzene methylation with methanol using a dual function catalyst system. A first catalyst accomplishes the toluene and/or benzene methylation and a second catalyst converts the by-products of the methylation reaction or unconverted methylating agent, improves the yields of the desired products, or a combination thereof. The inclusion of the second catalyst can suppress the C1-C5 non-aromatic fraction by over 50% and significantly enhance the formation of aromatics.
Claims18
A process for producing para-xylene, the process comprising:
- (a) providing a catalyst comprising core crystals of a first medium-pore size aluminosilicate zeolite having a pore size of about 5 to about 7 Angstroms and a discontinuous layer of shell crystals of a second medium-pore size aluminosilicate zeolite covering at least a portion of the external surface of the core crystals in a fluidized bed reactor, wherein the first medium-pore size aluminosilicate zeolite has a lower silica/alumina molar ratio than that of the second medium-pore size aluminosilicate zeolite;
- (b) alkylating C6+ aromatic hydrocarbons with an alkylating agent selected from methanol, dimethyl ether, and mixtures thereof, on contacting the shell crystals under conditions including a temperature of at least 400° C. to produce a mixture comprising olefins and/or paraffins, para-xylene, unconverted alkylating agent, and unconverted C6+ aromatics hydrocarbons;
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- (c) converting the olefins and/or the paraffins formed in step (b), unconverted alkylating agent, and unconverted C6+ aromatic hydrocarbons to para-xylene on contacting the core crystals.
A process for producing para-xylene, the process comprising:
- (a) providing a core-shell catalyst comprising a discontinuous layer of shell crystals covering at least a portion of the external surface of core crystals in a fluidized bed reactor,
- wherein the shell crystals comprise ZSM-5 having a silica/alumina molar ratio of at least 200, as measured prior to any steaming of the catalyst, and phosphorus or a compound thereof, wherein the catalyst has been steamed at a temperature of at least 900° C., wherein said steamed catalyst has a Diffusion Parameter for 2,2 dimethylbutane of about 0.1-15 sec−1 when measured at a temperature of 120° C. and a 2,2 dimethylbutane pressure of 60 torr (8 kPa),
- wherein the core crystals comprise ZSM-5, and the ZSM-5 of the core crystals has a lower silica/alumina molar ratio than that of the shell crystals;
- (b) alkylating C6+ aromatic hydrocarbons with an alkylating agent selected from methanol, dimethyl ether, and mixtures thereof, on contacting the shell crystals to produce a mixture comprising olefins and/or paraffins, para-xylene, unconverted alkylating agent, and unconverted C6+ aromatics hydrocarbons;
- and
- (c) converting the olefins and/or the paraffins formed in step (b), unconverted alkylating agent, and unconverted C6+ aromatic hydrocarbons to para-xylene on contacting the core crystals.
Dependencies are inferred from the claim text.