Copper for Sulfur Removal
Sulfur in fuels such as natural gas or gasoline can be oxidized during combustion to form sulfur dioxide, a pollutant that contributes to acid rain. Removing sulfur from these fuels during refining helps control emissions and protects catalysts used in the refining process.
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State of the Art
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In 2011, sulfur is generally removed from fuels through a catalytic hydrogenation process, where hydrogen is used as a reducing agent and reacts with sulfur in the fuel to generate hydrogen sulfide. This process has its limitations, however, and it's typically difficult to reduce sulfur content past a certain point. Consequently, some researchers have sought alternative methods, including techniques involving copper-exchanged zeolites.
Function
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Zeolites are minerals full of microscopic pores like a tiny sieve. Sulfur compounds like dimethyl sulfide can be adsorbed or become stuck to the copper zeolite and be removed from the fuel.
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Considerations
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According to the Pacific Northwest Laboratory, zeolites with divalent copper seem to be more successful at removing sulfur compounds from natural gas, while monovalent copper zeolites seem to perform better in removing sulfur compounds from liquid fuels like gasoline. Improving the performance of these and similar materials is a subject of ongoing research.
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References
- Department of Energy Hydrogen, Fuel Cells and Infrastructure Technologies: Sulfur Removal from Reformate
- Institute for Interfacial Catalysis at Pacific Northwest National Laboratory: Removal of Sulfur Components from Low Sulfur Gasoline
- University of Tulsa: Zeolite Y
- Penn State University: Selective Adsorption for Removing Sulfur for Making Ultra-Clean Transportation Fuels
- Photo Credit gasoline tank image by Anna Fedoruk from Fotolia.com
