| abstract |
The average propylene cycle selectivity 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 hydrocarbon synthesis portion of the OTP flow scheme in lieu of the fixed bed technology of the prior art; 2) a hydrothermally stabilized and dual-functional catalyst system comprising a molecular sieve having dual-function capability dispersed in a phosphorus-modified alumina matrix containing labile phosphorus and/or aluminum anions; and 3) a catalyst on-stream cycle time of 400 hours or less. These provisions stabilize the catalyst against hydrothermal deactivation and 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 near or at essentially start-of-cycle levels. |