Mobil Oil Corporation

Jeevan S Abichandani

Jeffrey S Beck

David Lawrence Stern

Ivy Dawn Johnson

Stephen Harold Brown

David H Olson

Chaya R Venkat

Ronald J Cimini

Dimitris K Liguras

David S Shihabi

Mae K Rubin

Sharon B McCullen

Daria N Lissy

Sanjay B Sharma

Ronald H Fischer

P Thomas Reischman

Selma Kwok

A shape-selective catalyst comprises a synthetic porous crystalline material having the structure of ZSM-5 and a composition involving the molar relationship: X O :(n)YO , wherein X is a trivalent element, such as aluminum, boron, iron and/or gallium, preferably aluminum; Y is a tetravalent element such as silicon and/or germanium, preferably silicon; and n is greater than about 12, and wherein the crystals have a major dimension of at least about 0.5 micron and a surface YO /X O ratio which is no more than 20% less than the bulk YO /X O ratio of the crystal. The crystals have a diffusion-modifying surface coating of a refractory material such as silica or coke. The catalyst is useful in a wide variety of selective hydrocarbon conversion processes, particularly the selective disproportionation of toluene to para-xylene.

Shape selective zeolite catalyst and its use in aromatic compound conversion

A method for minimizing the loss of xylenes in an ethylbenzene conversion/isomerization process by adding toluene to the feedstock. The concentration of toluene in the feedstock is increased by co-feeding toluene or by recycling toluene separated from the ethylbenzene conversion reactor effluent. The increased toluene concentration reduces the loss of xylenes during the ethylbenzene conversion reaction and under preferred operating conditions increases the amount of xylenes in the product.

Xylene isomerization process using toluene co-feed

A method for increasing the efficiency of xylene isomerization by using a two stage isomerization process. In the first stage of the process, a C.sub.9.sup.+ aromatics feedstock is subjected to ethylbenzene conversion and xylene isomerization. Non-C.sub.8 aromatics are removed from the effluent, which is then processed in a second stage of the process to remove para-xylene and isomerize the para-xylene depleted effluent. The effluent from the second stage isomerization unit is then recycled into the inlet of the second stage of the process and a slip stream from the para-xylene separator is recycled to the feedstock and to the effluent of the ethylbenzene conversion unit. In this way, the production of para-xylene is maximized. In a preferred embodiment, toluene is co-fed into the feedstock to minimize the loss of xylenes during the ethylbenzene conversion reaction.

Dual-loop xylene isomerization process

A process for ethylbenzene production that involves contacting a hydrocarbon feedstream including benzene and ethylene, under alkylation conditions, with a catalytic molecular sieve which has been modified by being ex situ selectivated with a silicon compound. The ex situ selectivation involves exposing the molecular sieve to at least two selectivation sequences, each selectivation sequence comprising contacting the catalyst with a silicon compound followed by calcination. The modified catalyst used in the process may also be steamed. Optionally, the modified catalyst may be trim-selectivated.

Ethylbenzene production process with ex situ selectivated zeolite

A mixture of aromatic hydrocarbons, comprising ethylbenzene and at least one xylene, is treated to convert the ethylbenzene to compounds that may be removed from the aromatic hydrocarbon stream and to isomerize any xylenes present. The ethylbenzene conversion catalyst is one that is effective for ethylbenzene conversion with minimal xylene loss, e.g., a silica bound intermediate pore size zeolite that has been selectivated. The xylene isomerization catalyst is one which is effective to catalyze xylene isomerization. Each of the catalysts of this invention may contain one or more hydrogenation or dehydrogenation components.

Selective ethylbenzene conversion

There is provided a continuous toluene disproportionation process to selectively produce para-xylene. The process includes a steady-state of operation, wherein the conversion of toluene and selectivity to para-xylene is maintained at essentially constant target levels. Prior to such a steady-state of operation, the reaction is conducted under a relatively high temperature.

Continuous toluene disproportionation process

A mixture of aromatic hydrocarbons, comprising ethylbenzene and at least one xylene, is isomerized using a two component catalyst system to convert the ethylbenzene to compounds that may be removed from the aromatic hydrocarbon stream and to produce a product stream wherein the para-xylene concentration is approximately equal to the equilibrium ratio of the para-isomer. The first catalyst comprises an intermediate pore size zeolite that is effective for ethylbenzene conversion. The first catalyst is preferably silica-bound. The second catalyst comprises an intermediate pore size zeolite, which further has a small crystal size and which is effective to catalyze xylene isomerization. Each of the catalysts of this invention may contain one or more hydrogenation/dehydrogenation component.

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Voorhees, NJ, United States of America

Jeevan S Abichandani