Selective conversion of oxygenate to propylene using moving bed technology and a hydrothermally stabilized dual-function catalyst

A continuous process for selective conversion of an oxygenate feed containing methanol or a mixture of DME and methanol to propylene comprising the steps of:

• a) reacting the oxygenate feed and a diluent in an amount corresponding to about 0:5 to 5:1 moles of diluent per mole of oxygenate with particles of a dual-function and hydrothermally stabilized catalyst, comprising a molecular sieve having the ability to convert at least a portion of the oxygenate to C3 olefin and to interconvert C2 and C4+ olefins to C3 olefin dispersed in a phosphorus-modified alumina matrix containing labile phosphorus and/or aluminum anions wherein the anions are available to repair, anneal and/or stabilize a framework of the molecular sieve, in a reaction zone containing at least one moving bed reactor wherein the reaction zone is operated at oxygenate conversion conditions selected to convert oxygenate to propylene and at a catalyst circulation rate through the reaction zone selected to result in a catalyst on-stream cycle time of 400 hours or less to produce an effluent stream containing major amounts of a C3 olefin product and a water by-product and lesser amounts of a C2 olefin, C4+ olefins, C1 to C4+ saturated hydrocarbons and minor amounts of unreacted oxygenate, by-product oxygenates, highly unsaturated hydrocarbons and aromatic hydrocarbons;
• b) passing the effluent stream to a separation zone and therein cooling and separating the effluent stream into a vaporous fraction rich in C3 olefin, a water fraction containing unreacted oxygenate and by-product oxygenates and a liquid hydrocarbon fraction containing heavier olefins, heavier saturated hydrocarbons and minor amounts of highly unsaturated hydrocarbons and aromatic hydrocarbons;
• c) recycling at least a portion of the water fraction recovered in step b) to step a) to provide at least a portion of the diluent used therein;
• d) separating the vaporous fraction into a C2 olefin-rich fraction, a C3 olefin-rich product fraction and a first C4+ olefin-rich fraction;
• e) recycling at least a portion of the olefins contained in the C2 olefin-rich fraction or in the first C4+ olefin-rich fraction or in a mixture of these fractions to step a);
• and
• f) withdrawing coke-containing dual-function catalyst particles from the reaction zone, oxidatively regenerating the withdrawn catalyst particles in a regeneration zone and returning a stream of regenerated catalyst particles to the reaction zone.