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 comprisingi) contacting a naphtha feed with a membrane separation zone, said separation zone containing a membrane having a sufficient flux and selectivity to separate a sulfur-enriched permeate fraction and a sulfur deficient retentate fraction, said sulfur deficient retentate fraction having a sulfur content of less than 100 ppm sulfur and comprising at least 50 wt % of olefins present in the naphtha feed under pervaporation conditions, said membrane having a sulfur enrichment factor of greater than 1.5, said naphtha feed being selected from the group consisting of a light naphtha, an intermediate naphtha, a coker naphtha, a straight run naphtha and mixtures thereof, and comprising sulfur containing aromatic hydrocarbons, sulfur containing non-aromatic hydrocarbon 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 a reduced sulfur permeate product stream.
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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.
138 Citations
22 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 membrane having a sufficient flux and selectivity to separate a sulfur-enriched permeate fraction and a sulfur deficient retentate fraction, said sulfur deficient retentate fraction having a sulfur content of less than 100 ppm sulfur and comprising at least 50 wt % of olefins present in the naphtha feed under pervaporation conditions, said membrane having a sulfur enrichment factor of greater than 1.5, said naphtha feed being selected from the group consisting of a light naphtha, an intermediate naphtha, a coker naphtha, a straight run naphtha and mixtures thereof, and comprising sulfur containing aromatic hydrocarbons, sulfur containing non-aromatic hydrocarbon 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 a reduced sulfur permeate product stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. 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 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, said sulfur deficient retentate fraction comprising at least 50 wt % of the naphtha feed and at least 50 wt % of olefins present in the naphtha feed under pervaporation conditions, said membrane having a sulfur enrichment factor of greater than 1.5, said naphtha feed being selected from the group consisting of a light naphtha, an intermediate naphtha, a coker naphtha, a straight run naphtha 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 sulfur content; and iv) recovering a reduced sulfur permeate product stream.
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Specification