HYDROCARBON SEPARATION

1375316 Separating hydrocarbons by adsorption UNIVERSAL OIL PRODUCTS CO 7 March 1972 [8 March 1971] 10474/72 Heading C5E In a process for separating hydrocarbons from a feed 7 comprising the steps of adsorption 1, purification 2 and desorption 3, a buffer zone 4 is provided in which raffinate 15 from the zone 1 is passed through desorbent from the zone 3 to displace desorbent from the void volume of the adsorbent. Each zone 1 ... 4 may comprise one or more beds, and in an example, a series of 24 beds of a zeolite are used in simulated moving bed operation. Xylenes, diethylbenzenes, ethylbenzene and various C 9 to C 12 aromatic hydrocarbon isomers may be separated in liquid or vapour phase. Recycle raffinate, from which desorbent has been removed, is led in at 6 to displace desorbent from the adsorbent, and recycle extract from the fractionation of extract leaving at 9, is led in at 8 to remove raffinate from the zeolite in zone 2. Desorbent is supplied at 10 for zone 3.