GB1175990A - Benzene Production. - Google Patents

Abstract

1,175,990. Benzene; toluene; treating pyrolysis gasoline. AIR PRODUCTS & CHEMICALS Inc. 29Nov., 1967 [16 Dec., 1966], No. 54359/67. Heading C5E. Benzene is produced from pyrolysis naphtha containing polymerizable unsaturates, e.g. dripolene, by contacting a vaporized mixture of the feed and a hydrogen-containing gas in a first reaction zone with sulphided cobalt molybdate or sulphided nickel cobalt molybdate under conditions effecting hydrogenation of the polymerizable unsaturates, contacting the effluent from the first zone with chrome-alumina catalyst in a second reaction zone under hydrocracking conditions, thus effecting cracking of non-aromatics and dealkylation of alkylaromatics, separating the effluent into vapour and liquid phases, and recovering benzene from the liquid phase. Suitable conditions for the hydrogenation are: inlet temp. 204-343‹ C., pressure 42-84 kg./sq. cm. gauge, LHSV 0À1-5À0, hydrogen to oil mole ratio 1-12, and the catalyst may be supported on alumina. Sulphur may be added to the hydrogenation feed, e.g. as CS 2 or a mercaptan. Suitable conditions for the hydrocracking are: outlet temp. 593-650‹ C., pressure 56-84 kg./sq. cm. gauge, contact time 30-180 seconds, hydrogen partial pressure 17À5-49 kg./sq. cm. gauge, and inlet hydrogen to total aromatics mole ratio 3:1-10:1. Either reaction may be conducted in several reactors, with cooling between successive reactors. The recovered liquid phase is stabilized by removal of hydrogen and light hydrocarbons, clay treated and fractionated to recover benzene. Unconverted products and by-product diphenyl may be recycled to the hydrocracking, though if desired toluene may be recovered as product. The recovered gaseous phase may also be recycled as part of the hydrogen-containing gas to the first stage.