Patent ID: 8283511

Claim:
A process for preparing a feedstream to be charged to a steam cracking unit producing ethylene, the process comprising: (a) passing a process feed stream comprising C 5 to C 9 hydrocarbons including C 5 to C 9 normal paraffins into an adsorption zone of a simulated moving bed adsorptive separation zone operating at an A/Fn of about 0.90 to about 0.92 and selectively retaining normal paraffins on an adsorbent located in the adsorption zone to yield a raffinate stream comprising non-normal C 5 to C 9 hydrocarbons and hydrocarbon desorbent containing 12 carbon atoms; (b) passing the desorbent into a desorption zone in the simulated moving bed adsorptive separation zone as at least part of a desorbent stream and removing normal paraffins from adsorbent present in the desorption zone to yield an extract stream comprising C 5 to C 9 normal paraffins and desorbent; (c) separating the extract stream in an extract fractionation zone into a second process stream comprising desorbent and a third process stream comprising C 5 to C 9 normal paraffins; and (d) passing the third process stream into a cracking zone and producing ethylene.