Ultra-deep Desulfurization Of Diesel By Selective Oxidation In Emulsion System

Sulfur oxides, coming from the combustion of organic sulfide in fuel oil, can causehaze, acid rain and other environmental problems. Many countries and regions in theworld impose severe restrictions on contents of sulfur in fuel oil. Our country has alsointroduced Europe IV Standard for motor gasoline and motor diesel oil since2013, whichrequires the content of sulfur be below50μg/g. Compared with theconventional hydrodesulfurization, oxidative desulfurization performs better forrefractory compounds under mild reaction conditions, so that it is regarded as a highlypromising alternative process.In this work, water-in-oil type emulsion oxidation system is formed bymixing amphiphilic catalyst, hydrogen peroxide and diesel, under suitableconditions, organic sulfur compounds in the diesel is oxidized to sulfone or sulfoxide.followed by extracting with DMF, low sulfur diesel meeting the Euro IV standard isobtained.In this experiment, two kinds of amphiphilic catalysts, paratungstate (C₂₁H₄₆N)8[Na2H₂W12O42]·9H₂O and two lacunary polyoxotungstensilicate (C₂₁H₄₆N)6[K₂γ-SiW₁₀O₃₆],are synthesized, IR,UV-vis, X-ray single crystal diffraction and TG areused to investigate the structure. After the oxidative desulfurization of diesel, it is foundthat, emulsion system has good oxidation activity on organic sulfur compounds ofdifferent types and concentration under suitable conditions（50℃,O/S=5/1）,dibenzothiophene and its derivatives are more easily oxidized than benzothiophene and itsderivatives,and the rate of oxidation reaction is accelerated as the sulphide concentrationincreased.As for the paratungstate (C₂₁H₄₆N)₈[Na₂H₂W₁₂O₄₂]·9H₂O which has better catalyticoxidation activity, we also investigate its performance on recycling and desulfurizationcapability of genuine diesel. The experimental results show that: There is no apparentdecrease of the catalytic activity after re-use of the catalyst5times, and the conversionrate of dibenzothiophene can reach to95.3%without significant changes of the c atalyst’s chemical structure. The catalyst shows excellent oxidative desulfuriztion performances onthe genuine diesels with different compositions and sulfur contents, and the sulfur contentin the dieselcanbe reduced to below50μg/gafter one oxidation-extractionprocess.