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.