GB1248814A - Hydrocarbon conversion process - Google Patents

Abstract

1,248,814. Steam cracking; separating hydrocarbons. STONE & WEBSTER ENG. CORP. 5 May, 1969 [10 May, 1968], No. 22748/69. Heading C5E. Ethylene and/or propylene are produced as follows: (a) a petroleum distillate boiling in the gas oil range and comprising aromatic, naphthenic and paraffinic components is treated to remove at least some of the aromatics; (b) the treated feed is mixed with steam in a weight ratio of steam: hydrocarbon in the range 0À1- 2À0; (c) the feed is then cracked for 0À15-1À5 seconds to an outlet temperature of 1300- 1700‹ F. in a tubular reaction zone, the hydrocarbon partial pressure at the outlet being maintained at 6-20 p.s.i.a.; and (d) rapidly cooling the effluent and recovering olefin product. Suitable feeds are light, heavy and vacuum gas oils and light and heavy catalytic cycle oils. The tubular furnace is suitably of the type having a convection-heated preheat section and a radiant-heated cracking section. The removal of aromatics in step (a) may be performed by solvent extraction or by solid adsorbents. Suitable solvents are furfural, SO 2 , phenol and dimethylformamide, and suitable solids are silica gel and molecular sieves. A dual column extraction is also referred to, in which the feed is contacted in the first column with an aromatics selective solvent, e.g. furfural-furfuryl alcoholwater mixture, aqueous DMF or aqueous tetrahydrofurfuryl alcohol, and the aromatic extract is then contacted in the second column with a displacer liquid, e.g. a naphtha-xylene mixture, which removes the extracted aromatics from the solvent.