Production of alkyl aromatic compounds

Abstract

Improved integrated processes for the production of alkyl aromatic compounds are disclosed wherein aromatic compounds which may be treated for removal of deleterious substances are reacted with olefin compounds, which may also be treated for contaminant removal, in the presence of acidic zeolite catalyst(s) to produce the desired alkyl aromatic compound(s). The aromatic and preferably also the olefin feeds are treated substantially to remove contaminants, particularly the nitrogen compounds contained therein, before they are brought together for reaction in the presence of the zeolite catalyst(s). In accordance with the present invention, it has been found that feed pretreatment for removal of nitrogen compounds significantly improves the run length and life of the acidic zeolite catalyst(s). The feed pretreatment of this invention may include the steps of distillation, extraction, and / or adsorption by solid adsorbent, which may be regenerated in accordance with further embodiments of this invention.

Description

BACKGROUND OF THE INVENTION[0001]Catalytic reaction of aromatics and olefins in the presence of acidic zeolite catalysts has been used in most of the advanced chemical processes for the production of alkyl aromatic compounds such as cumene and ethylbenzene. Since the early 1990s, new zeolite-based cumene technologies have been developed by Mobil / Badger, Dow / Kellogg, UOP, and others. These cumene technologies carry out the alkylation of benzene and propylene in liquid phase in the presence of a solid acidic zeolite catalyst. A process developed by CDTech effects alkylation of benzene and propylene in mixed phases in a catalytic distillation column which houses both distillation devices and bales of zeolite catalysts. Catalysts that can be used for alkylation of benzene with propylene and also for transalkylation of benzene and polyisopropylbenzenes in liquid phase include zeolite beta, zeolite Y, zeolite omega, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, Faujasite,...

AI Technical Summary

Benefits of technology

[0026]Accordingly, a principal object of this invention is to provide improved methods and processes and related apparatus for the pretreatment of hydrocarbon feedstocks prior to contact with alkylation and / or transalkylation acidic zeolite catalyst bed(s) to remove or substantially reduce impurities in such feedstocks which otherwise might adversely affect the performance, operation or life of the catalyst bed(s).

[0027]A general object of this invention is to provide pretreated hydrocarbon feedstocks which are substantially free of impurities which could damage downstream catalyst bed(s) used for alkylation, transalkylation and similar processes.

[0030]Another specific object of this invention is to provide a hydrocarbon feedstock pretreatment method comprising one or a combination of distillation, extraction, and / or adsorption steps for removing or substantially reducing impurities which might poison a downstream catalyst bed.

[0033]Although production of alkyl aromatic compounds like cumene and ethylbenzene in the presence of acidic zeolite catalysts has attained much commercial success, the susceptibility of acidic zeolite catalysts to deactivation has severely limited catalyst run length and catalyst life. In accordance with the present invention, it has now been found that nitrogen-containing impurities in one or both feedstocks may neutralize the acidic active sites on the acidic zeolite catalyst and thereby reduce catalyst activity and its ability to effect the desired reaction. Long-term accumulation of these nitrogen-containing impurities on the catalyst gradually reduces catalyst activity to the point where plant performance becomes unacceptable, requiring that the plant be shutdown to reactivate, regenerate, or replace the catalyst.

[0034]The cost of such a plant shutdown often includes not only the cost of the operations required to bring plant performance back to a desirable or commercially acceptable level but also includes the lost profit the producer failed to realize from sale of the product which otherwise could have been produced during the plant shutdown. In some cases, frequent reactivation or regeneration of the poisoned catalyst also reduces catalyst life. In such cases, additional catalyst replacement cost is also incurred.

[0035]Pretreatment of one or both feedstocks to remove nitrogen compounds and / or other contaminants which are present in amounts sufficient to adversely affect the performance of an acidic zeolite catalyst by one or a combination of pretreatment processes in accordance with this invention prior to alkylation and / or transalkylation, together with regeneration of adsorbents used in an adsorption pretreatment, has now been found to be the most cost-effective way to minimize the costs association with harmful impurities in the feedstock(s).

Problems solved by technology

Although production of alkyl aromatic compounds like cumene and ethylbenzene in the presence of acidic zeolite catalysts has attained much commercial success, the susceptibility of acidic zeolite catalysts to deactivation has severely limited catalyst run length and catalyst life.

Long-term accumulation of these nitrogen-containing impurities on the catalyst gradually reduces catalyst activity to the point where plant performance becomes unacceptable, requiring that the plant be shutdown to reactivate, regenerate, or replace the catalyst.

The cost of such a plant shutdown often includes not only the cost of the operations required to bring plant performance back to a desirable or commercially acceptable level but also includes the lost profit the producer failed to realize from sale of the product which otherwise could have been produced during the plant shutdown.

In some cases, frequent reactivation or regeneration of the poisoned catalyst also reduces catalyst life.

In such cases, additional catalyst replacement cost is also incurred.