Patent ID: 7425663

Claim:
A method for producing a hydrocarbon mixture rich in propylene, consisting essentially of propylene, ethylene and other light hydrocarbons from a liquid charge stream containing C 4 to C 8 olefins, which comprises the steps of: (a) charging the liquid charge stream containing C 4 to C 8 hydrocarbons into an evaporator at a temperature of 25 to 200° C. to evaporate the liquid stream; (b) superheating the evaporated liquid stream at a temperature of 350 to 400° C. followed by an additional superheating of the evaporated liquid stream to 450 to 550° C. using hot water vapor; to form an olefin—water vapor mixture; (c) adiabatically reacting the olefin—water vapor mixture, superheated according to step (b), over a shape-selective, pentasil zeolite fixed-bed catalyst to convert a majority of the C 4 to C 8 olefins in the olefin—water vapor mixture to a mixture of C 3 to C 6 olefins rich in propylene; (d) following step (c), cooling the olefin—water vapor mixture to a temperature of 100 to 200° C.; (e) quenching the olefin—water vapor mixture cooled according to step (d), to a temperature of 40 to <100° C., to partially condense the olefin—water vapor mixture; thereby obtaining a gaseous hydrocarbon phase consisting essentially of ethylene, propylene, C 4 to C 8 olefins and additional hydrocarbons and, a liquid phase consisting essentially of water that is returned to the evaporated liquid stream during step (b); (f) compressing the gaseous hydrocarbon phase obtained according to step (e) at a pressure of 20 to 30 bar absolute to remove accumulated water from the gaseous hydrocarbon phase to obtain a mixture of gaseous and liquid hydrocarbon phases; (g) separating the mixture of gaseous and liquid hydrocarbon phases into a gaseous hydrocarbon phase, rich in propylene, consisting essentially of propylene, ethylene, and other light hydrocarbons, and recovering said gaseous hydrocarbon phase and a liquid hydrocarbon phase containing C 4 + olefins; and (h) separating the liquid hydrocarbon phase into a fraction containing C 4 to C 6 olefins and a fraction containing C 7 + olefins.