Epoxidation process using serially connected cascade of fixed bed reactors

Abstract

An olefin epoxidation process is operated using a plurality of reactor vessels, each containing a fixed bed of a heterogenous catalyst such as titania-on-silica. The reactor vessels are connected in series whereby a feedstream comprised of olefin and an active oxygen species is passed through said series of reactor vessels in contact with the heterogenous catalyst to accomplish conversion of the olefin to the corresponding epoxide. As the activity of the catalyst in an individual reactor vessel falls to an undesirably low level, said reactor vessel is taken out of service and a replacement reactor containing fresh or regenerated catalyst introduced. The replacement reactor vessel may, in alternative embodiments of the process, be the first or the last reactor vessel in said series. For example, the feedstream may first be contacted with either the most active or the least active charge of catalyst within the series of reactor vessels. Although the latter embodiment permits somewhat longer catalyst life, the former embodiment requires much smaller capacity heat exchangers. The process of this invention considerably reduces catalyst usage as compared to a conventional fixed bed epoxidation process where all of the catalyst is replaced or regenerated at the same time.

Description

field of invention [0001] The present invention provides a method of operating an epoxidation plant using a heterogeneous catalyst which makes it possible to significantly extend the lifetime of said catalyst. More particularly, the invention relates to a cascade of continuously connected fixed bed reactors in which a single reactor is periodically taken offline for catalyst regeneration or replacement when catalyst activity has dropped to an undesirable level; The catalyst reactor was brought into use so that the epoxidation proceeded without interruption. A feedstream containing olefins and reactive oxygen species is continuously fed through the reactor cascade, ideally with the aid of heat exchangers to control the temperature of the exothermic process to maintain high epoxidation selectivity. In one embodiment, the feedstream is contacted with the most active catalyst in the series first. In another embodiment, the feedstream is contacted with the least active catalyst f...

AI Technical Summary

Problems solved by technology

A deactivated catalyst can alternatively be replaced with fresh catalyst, but will have the same practical disadvantages as regeneration

Also, catalysts of this type tend to be relatively expensive, and it may be desirable to minimize the amount of fresh catalyst that needs to be supplied to the facility

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