Catalytic sulfur removal from a hydrocarbon stream

Abstract

A process for the catalytic removal of sulfur from a hydrocarbon stream such as gasoline comprising an organo-sulfur compound such as a mercaptan or thiol. The catalyst is a silica based zeolite such as ZSM-5. The process is preferably performed in a downer reactor with a residence time of between 7 and 30 seconds and a volumetric particle concentration of between 15 and 40%. Preferably, substantially all of the sulfur that is removed from the organo-sulfur compound is in the form of hydrogen sulfide.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. provisional patent application Ser. No. 60 / 632,560 filed Dec. 2, 2004, the entire contents of which are hereby incorporated by reference.FIELD OF THE INVENTION [0002] The invention relates to the catalytic removal of sulfur from hydrocarbon streams comprising a sulfur containing hydrocarbon. In particular, the invention relates to the removal of sulfur compounds such as mercaptans and thiols from hydrocarbon streams such as gasoline by catalytic conversion to hydrogen sulfide using a zeolite catalyst such as ZSM-5. The invention may be practiced using a solids transport reactor and is advantageously practiced in a downer reactor. BACKGROUND OF THE INVENTION [0003] Sulfur in fuels for internal combustion engines is generally undesirable. In the auto industry, high sulfur levels in gasoline lead to poisoning of catalytic converters and to corrosion caused by sulfuric acid compounds. Sulfur in fu...

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Benefits of technology

[0013] Surprisingly, the process of the present invention provides high conversion of sulfur compounds to hydrogen sulfide at relatively short residence times with no undesirable thio-paraffin intermediates such as diethyl sulfide. Short residence times decrease the size of the reactor, improving the economics of the process, and reduce the likelihood for secondary olefin condensation reactions on the catalyst. This in turn reduces the production of aromatic hydrocarbons, which desirably limits any detrimental effect of the process on gasoline quality and limits the formation of coke on the catalyst. The process of the present invention is particularly advantageously carried out in a downer reactor, which permits optimization of process conditions over a range that achieves desirably high conversion while maintaining high selectivity.

[0014] The process of the present invention may be operated in a regime that provides the following key advantages:

[0022] The temperature in the reactor is any suitable temperature for promoting catalytic dehydrosulfidation of the organo-sulfur compound. Dehydrosulfidation is the process by which sulfur is removed from an organo-sulfur compound as hydrogen sulfide, for example, in a manner similar to the removal of oxygen from methanol as water in a de-hydration process. Generally, higher temperatures lead to faster reaction rates, but favour undesirable catalytic cracking of the hydrocarbon stream. There is therefore an optimal temperature range for the dehydrosulfidation process. The temperature may be from 300 to 500° C., preferably from 350 to 475° C., more preferably from 375 to 470° C., still more preferably from 400 to 460° C., even more preferably from 425 to 455° C., most preferably about 450° C.

Problems solved by technology

This in turn reduces the production of aromatic hydrocarbons, which desirably limits any detrimental effect of the process on gasoline quality and limits the formation of coke on the catalyst.

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