Prospect of Oxidative Desulfurization with Copper Phosphotungstate Catalyst

With the rapid development of automotive industry, sulfur pollution caused by combustion of automotive fuels is becoming more and more serious. Strict sulfur content standards for gasoline and diesel have been formulated in various countries and regions of the world. Hydrodesulfurization (HDS) is usually used in industry to remove sulfides from gasoline and diesel.

However, due to the steric hindrance effect of thiophene and its derivatives, the desulfurization effect is poor. In order to achieve the purpose of deep desulfurization, higher requirements on reaction conditions and catalysts will be put forward, which will lead to higher cost of gasoline and diesel.

Oxidative desulfurization (ODS) is a new technology developed in recent years to produce ultra-low sulfur fuels. It has mild reaction conditions, no consumption of hydrogen, less investment in equipment, high desulfurization efficiency for benzothiophene compounds which are difficult to remove by catalytic hydrogenation, and has good application prospects.

Recently, some scholars have reported the application of a dual-effect copper phosphotungstate catalyst in oil desulfurization. The desulfurization process can be summarized as the following steps:

A.Take the solid phosphotungstic acid, add water and ethanol, slowly add copper nitrate under constant stirring, and continue stirring to cause the double decomposition reaction; then heat, remove alcohol and part of water, and drop to room temperature. After crystallization, aging, filtration and drying, copper phosphotungstate is obtained.

B.Copper phosphotungstate was added into a 10 mL simulated oil containing 500 ug/g of sulfur, 0.5 mLH₂O₂ and 0.01 g of CTAB. In a constant temperature water bath with magnetic stirring, the reaction mixture was cooled to room temperature after 60 minutes, and the oil phase was separated by layering in a separating funnel. Adding 5 mL N-N-dimethylformamide, stirring for 5 minutes, static stratification, separation of oil phase, determination of sulfur content and calculation of desulfurization rate. Finally, the desulfurization rate using copper phosphotungstate catalyst was 72-93%.

Copper phosphotungstate catalyst has the advantages of simple preparation process, low cost, recyclable use, ideal oxidative desulfurization effect, mild reaction conditions, no consumption of hydrogen, less investment in equipment, high desulfurization efficiency for benzothiophene compounds which are difficult to remove in catalytic hydrogenation, and has good application prospects.

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