Conversion of an alcoholic oxygenate to propylene using moving bed technology and an etherification step

Abstract

The average propylene selectivity per on-stream cycle of an alcoholic oxygenate to propylene (OTP) process using one or more fixed beds of a dual-function oxygenate conversion catalyst is substantially enhanced by the use of a feed pretreatment step involving a catalytic etherification reaction, by switching to moving bed reactor technology in the olefin synthesis portion of the OTP flow scheme in lieu of fixed bed technology and by the selection of a catalyst on-stream cycle time of 300 hours or less. These provisions hold the build-up of coke deposits on the dual-function catalyst to a level which does not substantially degrade catalyst activity, oxygenate conversion and propylene selectivity, thereby enabling maintenance of propylene average cycle yield at essentially start-of-cycle levels. The propylene average cycle yield improvement enabled by the present invention over that achieved by the fixed bed system of the prior art using the same or a similar dual-function catalyst system is of the order of about 1.5 to 5.5 wt-% or more.