Membrane desulfurization of liquid hydrocarbons using an extractive liquid membrane contactor system and method

Abstract

The process of the present invention is directed to the desulfurization of a sulfur-containing hydrocarbon stream with a membrane contactor, where sulfur compounds are concentrated in a sulfur-rich stream on a permeate side of the membrane using an extractive liquid, and a sulfur-lean stream is recovered as a retentate. The sulfur-rich stream, which has a small volume relative to the original hydrocarbon stream, is conveyed to a recovery zone to recover extractive liquid, and the remaining hydrocarbon stream having an increased concentration of sulfur compounds is passed to a downstream desulfurization apparatus or system, such as a hydrotreating system, to recover the hydrocarbons associated with the organosulfur compounds.

Description

RELATED APPLICATIONS[0001]This applications claims priority to U.S. Provisional Patent Application Ser. No. 61 / 222,411, which is incorporated by reference in its entirety herein.FIELD OF THE INVENTION[0002]The invention relates to processes for desulfurization of a hydrocarbon feed using membrane separation, and more particularly to a process and system for desulfurization of a hydrocarbon feed using an extractive liquid membrane separation contactor.BACKGROUND OF THE INVENTION[0003]Compositions of natural petroleum or crude oils vary significantly, generally based upon the source. However, virtually all crude oils contain some level of sulfur compounds, including inorganically combined sulfur and organically combined sulfur, i.e., organosulfur compounds. Whole crude oil that contains a substantial concentration of sulfur compounds, such as hydrogen sulfide, and organosulfur compounds such as mercaptans, thiophenes, benzothiophenes, and dibenzothiophenes is referred to as “sour,” wh...

AI Technical Summary

Benefits of technology

[0023]In particular, the proposed membrane contactor relies on extractive liquids to solubilize and transfer the sulfur compounds though pores of the membrane, so that the transfer rate of the sulfur compounds is not hindered. The membrane contactor brings the extractive liquid and the liquid feedstream into controlled contact without intermixing. The requirements for creating a vacuum or to convert the permeate in a gaseous phase in order to enhance the transport of the sulfur compounds are obviated, and the operating costs associated with the use of vacuum and energy of vaporization are eliminated.

[0024]In one aspect, a process of the present invention is directed to desulfurization of a sulfur-containing hydrocarbon stream with a membrane separation apparatus in which sulfur compounds are concentrated in a sulfur-rich stream on a permeate side of the membrane and a sulfur-lean stream is recovered as a retentate. The sulfur-rich stream, which has a small volume relative to the original hydrocarbon stream, is subsequently conveyed to a desulfurization apparatus or system, such as a hydrotreating system, to recover the hydrocarbons associated with the organosulfur compounds. The stream desulfurized by conventional processes, such as hydrotreating, and the hydrocarbon stream desulfurized by the membrane separation apparatus can be combined to provide a low sulfur hydrocarbon effluent with minimal or no significant loss of the original volume of hydrocarbons.

Problems solved by technology

The evolution of sulfur compounds during processing and end-use of the petroleum products derived from sour crude oil poses safety and environmental problems.

However, under these more severe conditions, hydrocarbons are typically converted to less desirable intermediates or products.

The processes propose to minimize olefin and naphthene hydrogenation during hydrotreating, particularly problematic in hydrotreating FCC naphtha since the high olefin content is again prone to hydrogenation.

However, the use of unrefined petroleum products (e.g., crude oil) as a feedstream to a membrane separation process remains heretofore unknown to the inventors.

However, this process does not utilize membrane separation units to provide relatively compact and efficient separation.

Various problems exist with the above-described existing membrane desulfurization processes.

However, this required extensive energy consumption to pass the materials through the membrane, and also limits the feed stream.

Transport agents generally cause plasticizing of the selective membrane and has a deleterious impact on its selectively to sulfur compounds.

However, dispersed phase contactors require high solvent holdup, which is often associated with other problems such as emulsion formation, foaming, unloading and flooding.

Further, conventional extraction techniques such as liquid-liquid extraction, in which the two liquids are intermixed, suffers from many drawbacks, including slow phase separation and production of stable emulsions, resulting in the need to produce high surface area for mass transfer.

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