Membrane separation for sulfur reduction
First Claim
1. 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 polysiloxane membrane having a sufficient flux and selectivity to separate a sulfur-enriched permeate fraction and a sulfur deficient retentate fraction under pervaporation conditions, said naphtha feed 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 sulfur content; and
iv) recovering the reduced sulfur permeate product stream, wherein the total amount of olefin compounds present in the retentate product stream and the permeate product stream is at least 50 wt % of olefin compounds present in the feed.
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Abstract
A membrane process for the removal of sulfur species from a naphtha feed, in particular, a FCC light cat naphtha, without a substantial loss of olefin yield is disclosed. The process involves contacting a naphtha feed stream with a membrane having sufficient flux and selectivity to separate a sulfur deficient retentate fraction from a sulfur enriched permeate fraction, preferably, under pervaporation conditions. Sulfur deficient retentate fractions are useful directly into the gasoline pool. Sulfur-enriched permeate fractions are rich in sulfur containing aromatic and nonaromatic hydrocarbons and are further treated with conventional sulfur removal technologies, e.g. hydrotreating, to reduce sulfur content. The process of the invention provides high quality naphtha products having a reduced sulfur content and a high content of olefin compounds.
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Citations
18 Claims
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1. 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 polysiloxane membrane having a sufficient flux and selectivity to separate a sulfur-enriched permeate fraction and a sulfur deficient retentate fraction under pervaporation conditions, said naphtha feed 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 sulfur content; and
iv) recovering the reduced sulfur permeate product stream, wherein the total amount of olefin compounds present in the retentate product stream and the permeate product stream is at least 50 wt % of olefin compounds present in the feed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification