Patent ID: 7375257

Claim:
A process for cracking an olefin-rich hydrocarbon feedstock which is selective towards light olefins in the effluent, the process comprising: selecting a crystalline silicate catalyst from the group consisting of an MFI-type crystalline silicate having a silicon/aluminum atomic ratio of at least 180 and an MEL-type crystalline silicate having a silicon/aluminum atomic ratio from 150 to 800, wherein said selected catalyst has been subjected to a steaming step; passing an olefin-rich hydrocarbon feedstock containing one or more olefins through a moving bed reactor containing said selected catalyst at an inlet temperature of from 500° C. to 600° C., an olefin partial pressure of from 0.1 to 2 bars, and a LHSV of from 5 to 30 h −1 to produce an effluent containing propylene having an olefin content of a lower molecular weight than an olefin content of the feedstock; wherein the passing of the olefin-rich hydrocarbon feedstock through the moving bed reactor containing said selected catalyst and the production of the effluent containing propylene, causes concomitant deactivation of said catalyst; removing a first fraction of the deactivated catalyst from the moving bed reactor and transferring said deactivated catalyst to a regenerator; regenerating said first fraction of the deactivated catalyst in said regenerator to produce a second fraction of regenerated catalyst and then recycling said second fraction of the regenerated catalyst to the moving bed reactor; continuing the process of cracking of the olefin rich hydrocarbon feedstock within the reactor and the concurrent deactivation of said catalyst, while continuing to transfer said deactivated catalyst to the regenerator, while also continuing the regeneration of the deactivated catalyst and the recycling of the regenerated catalyst to the moving bed reactor; maintaining a propylene purity of the effluent from the moving bed reactor at a relatively constant value corresponding to an average value of that observed in a fixed bed reactor using the same feedstock, catalyst, and cracking conditions.