GB1149360A - Process for the manufacture of ethylene - Google Patents

Abstract

1,149,360. Olefins. FARBWERKE HOECHST A.G. 12 Dec., 1966 [10 Dec., 1965], No. 55635/66. Heading C5E. A process for the continuous manufacture of ethylene and, if desired, propylene and butylene, by cracking a hydrocarbon feed, e.g. light gasoline, comprises the following steps: (1) mixing the feed in a cracking zone with superheated steam at 1400-1500‹ C. in an amount of 1À5-2À5 times that of the feed; (2) cooling the reaction mixture leaving the cracking zone at about 850‹ C. in three successive stages, viz. (a) indirect cooling to 280-220‹ C. with simultaneous generation of high pressure steam, which is superheated and returned to the cracking zone, (b) direct cooling to effect removal of high boiling hydrocarbons, preferably to 150‹ C., e.g. with a high boiling recycle oil, and (c) indirect cooling to room temperature whereby the readily liquefiable hydrocarbons are separated ; (3) freeing the remainder of the cracked gases from CO 2 , sulphur compounds and acetylenes (e.g. by aqueous alkanolamine or amino-acid solutions for CO 2 and S, and selective hydrogenation for acetylenes); (4) separating normally liquid low boiling hydrocarbons and, if desired, propylene and butylenes by compression at 10-50 atmospheres gauge; (5) recycling at least part, preferably all, of the material separated in step 4 to the cracking . zone after heating and vaporizing separately from the feedstock; (6) washing the gas mixture remaining from step 4 with cuprous salt solution to separate olefins and CO ; and (7) distilling the resulting cuprous salt solution to remove and isolate ethylene or the desired mixture of olefins. The gases which are insoluble in the cuprous salt solution (at step 6) may be used for heat generation e.g. for production and/or superheating of steam for use in the cracking zone. The pressure of the high-pressure steam produced in the first cooling stage may be released with production of mechanical work.