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Process and catalysts for C8 alkylaromatic isomerization

a technology of alkylaromatic isomerization and catalyst, which is applied in the direction of hydrocarbon preparation catalysts, physical/chemical process catalysts, bulk chemical production, etc., can solve the problems of capital-intensive gas phase processes, and achieve the effects of saving hydrogen consumption, promoting stability, and saving considerable capital

Inactive Publication Date: 2005-06-16
NEMETH LASZLO T +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] Most gas phase processes are capital intensive and require installation of a fired heater, compressor, and gas-liquid separation system. A liquid phase process reduces required equipment to a reactor and heat exchanger thus saving considerable capital. Also, most gas phase processes use hydrogen to promote stability, which can be eliminated in a liquid phase process, thus saving hydrogen consumption and reducing loss of aromatics rings due to hydrogen saturation.
[0010] Accordingly, a principal object of the present invention is to provide a liquid phase process for the isomerization of alkylaromatic hydrocarbons. More specifically, the process of the present invention is directed to catalytic isomerization of C8 aromatic hydrocarbons over a beta zeolite and a pentasil zeolite such as MFI-type zeolite in order to obtain improved yields of desired xylene isomers.
[0011] Another broad embodiment of the present invention is directed toward a catalyst system for the isomerization of alkylaromatics based upon contacting a C8-aromatics rich hydrocarbon feed stream comprising less than the equilibrium amount of para-xylene with a catalyst comprising beta zeolite and a catalyst comprising a pentasil zeolite such as MFI-zeolite. The contacting occurs under at least partial liquid phase conditions in the absence of substantial hydrogen and allows a product stream to be recovered which comprises a greater amount of para-xylene than the feed stream. Preferably the amount of para-xylene in the product stream is at or greater than the equilibrium amount.

Problems solved by technology

Most gas phase processes are capital intensive and require installation of a fired heater, compressor, and gas-liquid separation system.

Method used

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Examples

Experimental program
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Effect test

examples

[0041] The following examples are presented only to illustrate certain specific embodiments of the invention, and should not be construed to limit the scope of the invention as set forth in the claims. There are many possible other variations, as those of ordinary skill in the art will recognize, within the spirit of the invention.

example i

[0042] Samples of the three catalysts comprising zeolites were prepared for comparative pilot-plant testing.

[0043] Catalyst A contained zeolite mordenite bound by alumina prepared in accordance with the teachings of U.S. Pat. No. 4,861,935. As received, mordenite powder was mixed with alumina powder to an approximate weight ratio of 9: 1, peptized, extruded, and acid washed by means known in the art.

[0044] Catalyst B contained aluminum-phosphate-bound MFI type zeolite prepared in accordance with U.S. Pat. No. 6,143,941. A first solution was prepared by adding phosphoric acid to an aqueous solution of hexamethylenetetraamine (HMT) in an amount to yield a phosphorus content of the finished catalyst equal to about 11 mass-%. A second solution was prepared by adding an ammonia-exchanged MFI-type zeolite having an Si / Al2 ratio of about 39 to enough alumina sol, prepared by digesting metallic aluminum in hydrochloric acid, to yield a zeolite content in the finished catalyst equal to abo...

example ii

[0047] The catalysts were evaluated for liquid phase isomerization of C8 aromatics using a pilot-plant flow reactor processing a non-equilibrium C8 aromatic feed having the following composition in wt-%:

Ethylbenzene7.17Para-xylene0.03Meta-xylene70.46Ortho-xylene22.28C9+ Aromatics0.05C9+ Non-aromatics0.01

[0048] This feed was contacted with catalyst at a liquid hourly space velocity of about 1.5 hr−1. Pressure was at 1200 kPa sufficient to maintain liquid phase. Reactor temperature was adjusted to effect a favorable conversion level. Catalyst C appeared as the most stable catalyst during this testing. Results were as follows:

CatalystABCTemperature, ° C.247245246EB conversion, mol- %19.72.150.1C10 Aromatics1.310.153.44p-xylene / xylenes, mol- %23.722.122.7

Catalyst C was particularly effective in converting undesired ethylbenzene isomers while still achieving a good proportion of para-xylene isomers in total xylene isomers.

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Abstract

A liquid or partially liquid phase process for isomerizing a non-equilibrium mixture of xylenes and ethylbenzene uses a zeolitic catalyst system preferably based on zeolite beta and on pentasil-type zeolite. The invention obtains an improved yield of para-xylene from the mixture relative to prior art processes in a more economical manner. A preferred beta zeolite is a surface-modified zeolite beta resulting from acid washing of a templated native zeolite at conditions insufficient to effect bulk dealumination. A preferred pentasil zeolite is a MFI-type.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a Division of copending application Ser. No. 10 / 736,312 filed Dec. 15, 2003, the contents of which are hereby incorporated by reference in its entirety.FIELD OF THE INVENTION [0002] The present invention relates to catalytic hydrocarbon conversion, and more specifically to the use of a catalyst system comprising pentasil zeolite such as MFI-type zeolite and beta zeolite in aromatics isomerization, and even more specifically to a process without hydrogen addition to convert a non-equilibrium feed depleted in para-xylene into an equilibrium product that is enriched in para-xylene. BACKGROUND OF THE INVENTION [0003] The xylenes, para-xylene, meta-xylene and ortho-xylene, are important intermediates that find wide and varied application in chemical syntheses. Para-xylene upon oxidation yields terephthalic acid that is used in the manufacture of synthetic textile fibers and resins. Meta-xylene is used in the manufacture of...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01J29/06C07C5/22C07C5/27
CPCC07C5/2708C07C2521/04C07C2521/08C07C2529/70C07C15/08Y02P20/52
Inventor NEMETH, LASZLO T.MAHER, GREGORY F.
Owner NEMETH LASZLO T
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