Study On Oxidation-Extraction Desulfurization Of Straight-run Diesel By Phase Transfer Catalysis

The research on desulfurization of diesel oil is speeding up all over the world as gradual strict global sulfur content specification. Oxidation-extraction desulfurization technique has many advantages, such as the simple technics and equipments, soft reaction condition, safety and environmental protection and low operation cost, therefore the method is given extensive attention. Building the system of oxidant and catalyst, selection and regeneration of extracting agent are becoming the study emphases.In this essay, two desulfurization methods were examined: hydrogen peroxide-formic and hydrogen peroxide-tungstophosphoric acid catalytic oxidation desulfurization of straight-run diesel by phase transfer catalysis. The sulfur content in diesel oil was analysed with microcoulometer method. Tetrabutylammonium bromide (TBAB) as phase transfer catalyst was added into the catalytic oxidation system, and then the reaction of sulfide can be changed into approximate homogeneous reaction from two phases of water-organic heterogeneous catalytic oxidation reaction, so that the dosage of oxidant was reduced and efficiency of desulfurization was improved. In the process of catalytic oxidation desulfurization, the non-polar organic sulfur compounds of diesel oil were transformed to polar sulfur compounds at low temperature and normal pressure, then the polar sulfur compounds were extracted from diesel with polar solvent. The influences of the content of oxidant, catalyst, extracting agent and phase transfer catalyst, the reaction temperature, reaction time and mixing speed have been investigated. The desulfurization rates reached 82.03% and 71.58% respectively in the optimal condition of the two methods, and the yields of diesel oil were 92.02% and 89.75%. When thiophene as a model sulfur compound was oxidized by hydrogen peroxide-formic catalytic oxidation desulfurization of simulative diesel oil by phase transfer catalysis, the reaction was a pseudo first-order reaction from the kinetics study, and the activation energy was Ea=7.47kJ·mol-1. Catalyst tungstophosphoric acid and extracting agent used in the experimentation can be reused by regeneration and recovery.