Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Reexamination Certificate
2000-11-21
2003-02-25
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
Reexamination Certificate
active
06525234
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for alkylating aromatics.
BACKGROUND OF THE INVENTION
Zeolite and other porous crystalline molecular sieve catalysts are increasingly being used in low temperature, liquid phase aromatic alkylation processes including ethylbenzene, cumene, and linear polyalkylbenzene (LAB) synthesis. Operation at lower temperatures improves process economics and, in many cases, product selectivity. However, trace feed impurities such as low molecular weight nitrogen, sulfur, and oxygen compounds, which are not strongly adsorbed in higher temperature vapor phase alkylation processes, are more problematic in the liquid phase processes. The affinity of these compounds for the active sites in the molecular sieve catalyst can cause rapid deactivation by displacing or neutralizing the acid site.
There are numerous methods known for reactivating catalysts. U.S. Pat. No. 2,541,044 to Daugherty discloses catalytic alkylation with simultaneous restoration of the alkylation catalyst activity by contacting the catalyst with an alkylatable hydrocarbon while interrupting the flow of alkylating agent. U.S. Pat. No. 3,148,155 to Schwartz describes removing metal poisons from cracking catalysts by contacting the poisoned catalyst with an aqueous solution of sulfurous acid, a water-soluble salt of sulfurous acid or a water-soluble salt of hyposulfurous acid. U.S. Pat. No. 4,418,235 to Haag discloses aromatic alkylation in the presence of steam to enhance or preserve zeolite catalyst activity. U.S. Pat. No. 4,550,090 to Degnan et al. describes a method for displacing high molecular weight poisons from ZSM-5 catalysts, such as those used in dewaxing, by in-situ treatment with more easily desorbed compounds such as ammonia or by treatment with alkali or alkaline metal cations to effect ion exchange. U.S. Pat. No. 4,276,149 to Chester et al. describes passivating metal contaminants on zeolite cracking catalysts by contacting with steam for limited periods. U.S. Pat. No. 4,678,764 to Le et al. discloses reactivation of noble metal-containing zeolites poisoned with sulfur oxides by contacting with aqueous acid solutions, e.g., nitric, carbon, acetic and formic acids. U.S. Pat. No. 4,319,057 to Kiser discloses regenerating molecular sieve dehydration materials with methanol or acetone. U.S. Pat. No. 5,425,934 to Malla et al. teaches treating zeolites with methanol, ethanol or propanol plus nitric or sulfuric acid for the removal of organic templates. U.S. Pat. Nos. 4,365,104 and 4,477,585 to Kaeding disclose enhancing para-selectivity of zeolite alkylation catalysts by treatment with hydrogen sulfide or carbon dioxide. U.S. Pat. 4,490,570 to Forward et al. discloses para-selective alkylation of a monoalkylbenzene wherein water in the form of steam can be co-fed with the reactants. U.S. Pat. No. 5,077,445 to Le discloses a process for liquid-phase synthesis of an alkylbenzene, such as ethylbenzene, using MCM-22 zeolite catalyst hydrated with liquid water. U.S. Pat. No. 5,191,135 to Dwyeret al. discloses preparing long chain alkyl substituted aromatic compounds by alkylating naphthalenes with C
6+
alkylating agent in the presence of large pore size zeolite such as USY and MCM-22 in the presence of 0.5 to 3.0 wt % co-fed water to increase selectivity to monoalkyl-substituted products.
All of the above patents are incorporated in their entirety herein by reference.
It would be desirable to provide a process for reactivating liquid phase alkylation catalysts which have been contaminated by trace quantities of strongly sorbed poisons. It would be especially useful to provide a method for reactivating such catalysts in-situ by treatment with species that are introduced along with the liquid phase or vapor phase feed streams.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to a process for alkylating aromatics which comprises:
i) contacting a feed containing alkylatable aromatic under liquid phase alkylating conditions with an alkylating agent of no greater than 5 carbon atoms in the presence of an alkylation catalyst comprising a porous crystalline material, to provide an alkylated aromatic product during which contacting said catalyst becomes at least partially deactivated by sorbing catalyst poisons present in said feed;
ii) treating said catalyst in situ by contacting with at least one polar compound having a dipole moment of at least 0.05 Debyes under conditions of temperature and pressure employed in said liquid phase alkylating conditions which are sufficient to at least partially desorb said catalyst poison from said catalyst; and
iii) collecting said alkylated aromatic product.
In another aspect, the present invention relates to a process for alkylating aromatics which comprises:
1) contacting a feed containing alkylatable aromatic under liquid phase alkylating conditions with alkylating agent in the presence of an alkylation catalyst comprising a porous crystalline material to provide an alkylated aromatic product during which contacting said catalyst becomes at least partially deactivated by sorbing catalyst poisons present in said feed;
2) treating said catalyst in situ by contacting with at least one non-aqueous polar compound having a dipole moment of at least 0.05 Debyes under conditions of temperature and pressure employed in said liquid phase alkylating conditions which are sufficient to at least partially desorb said catalyst poison from said catalyst; and
3) collecting said alkylated aromatic product.
The above and other objects, features and advantages of the present invention will be better understood from the following detailed descriptions, all of which are given by illustration only, and are not limitative of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Alkylation Catalysts
Acidic solid oxides which may be used to catalyze the present alkylation reaction include PSH-3, SSZ-25, MCM-22, MCM-36, MCM49 and MCM-56. PSH-3 is described in U.S Pat. No. 4,439,409. SSZ-25 and its use in aromatics alkylation is described in U.S. Pat. No. 5,149,894. MCM-22 and its use to catalyze the synthesis of alkylaromatics, including ethylbenzene, is described in U.S. Pat. Nos. 4,992,606; 5,077,445; and 5,334,795. MCM-36 is described in U.S. Pat. Nos. 5,250,277 and 5,292,698. U.S. Pat. No. 5,258,565 describes the synthesis of alkylaromatics, including ethylbenzene, using a catalyst comprising MCM-36. MCM-49 is described in U.S Pat. No. 5,236,575. The use of MCM49 to catalyze the synthesis of alkylaromatics, including ethylbenzene, is described in U.S. Pat. Nos. 5,493,065 and 5,371,310. MCM-56 is described in U.S. Pat. No. 5,362,697. The use of MCM-56 to catalyze the synthesis of alkylaromatics including ethylbenzene is described in U.S. Pat. Nos. 5,557,024 and 5,453,554. A preferred group of catalysts for use in the present invention is selected from the group consisting of MCM-22, MCM-36, MCM-49 and MCM-56, and most preferably, MCM-22.
Alternative catalysts suitable for use herein include medium pore zeolites having a Constraint Index of 2-12 (as defined in U.S. Pat. No. 4,016,218), such as ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, and ZSM-48. ZSM-5 is described in detail in U.S. Pat. No. 3,702,886. ZSM-11 is described in detail in U.S. Pat. No. 3,709,979. ZSM-12 is described in U.S. Pat. No. 3,832,449. ZSM-22 is described in U.S. Pat. No. 4,556,477. ZSM-23 is described in U.S. Pat. No. 4,076,842. ZSM-35 is described in U.S. Pat. No. 4,016,245. ZSM48 is more particularly described in U.S. Pat. No. 4,234,231.
In addition, large pore zeolites, including those zeolites having a Constraint Index less than 2, are suitable for use as the catalyst in the process of the invention. Suitable large pore zeolites include zeolite Beta, zeolite Y, Ultrastable Y (USY), Dealuminized Y (Deal Y), mordenite, offretite, ZSM-3, ZSM-4, ZSM-18, and ZSM-20. Zeolite ZSM-4 is described in U.S. Pat. No. 3,923,636. Zeolite ZSM-20 is described in U.S. Pat. No.3,972,983. Zeolite Beta is described in U.S. Pat. Nos. 3,308,069, and Re. No. 28,
Dandekar Ajit B.
Degnan Thomas Francis
McWilliams John P.
Venkat Chaya R.
Dang Thuan D.
ExxonMobil Oil Corporation
Tyus Darryl M.
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