The average propylene cycle yield of an oxygenate to propylene (OTP)
process using a dual-function oxygenate conversion catalyst is
substantially enhanced by the use of a combination of: 1) moving bed
reactor technology in the catalytic OTP reaction step in lieu of the
fixed bed technology of the prior art; 2) a separate heavy olefin
interconversion step using moving bed technology and operating at an
inlet temperature at least 15.degree. C. higher than the maximum
temperature utilized in the OTP reaction step; 3) C.sub.2 olefin recycle
to the OTP reaction step; and 4) a catalyst on-stream cycle time of 700
hours or less. These provisions hold the build-up of coke deposits on the
catalyst to a level which does not substantially degrade dual-function
catalyst activity, oxygenate conversion and propylene selectivity,
thereby enabling maintenance of average propylene cycle yield for each
cycle near or at essentially start-of-cycle levels.