Fremgangsmåte for fluid katalytisk krakking av hydrokarboner

A process for the fluid catalytic cracking of hydrocarbons includes contacting relatively heavy hydrocarbons with a fluidized particulate catalyst in a reaction zone under catalytic cracking conditions to convert at least some of the heavy hydrocarbons to light olefins having from 3 to 4 carbon atoms, conveying a reaction mixture containing spent catalyst particles and a gaseous stream containing the light olefins and other reaction products to a cyclone separation system directly connected to the reaction zone, at least part of the cyclone separation system being positioned within an interior space enclosed by a vessel, the interior space including a stripping region and an upper region in which the cyclone separation system is positioned. The cyclone separation system includes at least one cyclone connected directly to the reaction zone and having an interior pressure at least 0.05 psig lower than the pressure in the stripping region.