Patent ID: 6896796

Claim:
A method for lowering the sulfur content of a naphtha hydrocarbon feed stream while substantially maintaining the yield of olefin compounds in the feed stream, said method comprising i) contacting a naphtha feed with a membrane separation zone, said separation zone containing a polyimide membrane having a sufficient flux and selectivity to separate a sulfur-enriched permeate fraction and a sulfur deficient retentate fraction having a sulfur content of less than 100 ppm sulfur and containing greater than 50 wt % of olefin present in the naphtha feed under pervaporation conditions, said naphtha feed being selected from the group consisting of a light naphtha, an intermediate naphtha, a coker naphtha, a straight run naohtha and mixtures thereof, and comprising sulfur containing aromatic hydrocarbons, sulfur containing non-aromatic hydrocarbons and olefin compounds, said sulfur enriched permeate fraction being enriched in sulfur containing aromatic hydrocarbons and sulfur containing non-aromatic hydrocarbons as compared to the naphtha feed; ii) recovering the sulfur deficient retentate fraction as a product stream; iii) subjecting the sulfur-enriched permeate fraction to a non-membrane process to reduce the sulfur content; and iv) recovering the reduced sulfur permeate product stream.