Preparation Of Mo-based Catalyst And Its Application In Model Diesel Desulfurization

Petroleum is one of the most needed natural energy sources in this world.Normally petroleum is always used as transportation fuel,such as gasoline,diesel,aviation kerosene and so on.Sulfur compounds in petroleum produce SOx after combustion,which brings many ecological and environmental pollution,but it will also seriously damage our physical health.Some kinds of sulfides in fuel oils can be removed by conventional hydrodesulfurization processes,but some thiophene-like heterocyclic organic sulfides are difficult to be removed by hydrodesulphurization.Oxidative desulfurization process has many advantages over hydrodesulfurization process:the required reaction conditions are milder;the reaction cost is lower;thiophene-type heterocyclic organic sulfides can be oxidized to polar organic sulfur compounds;the obtained polar organic sulfur compounds can also be used as additives or industrial raw materials.Therefore,the oxidative desulfurization processes are being widely studied.There are two types of catalyst for oxidative desulfurization processes:homogeneous and heterogeneous catalysts.Compared with homogeneous catalysts,heterogeneous catalysts have the advantages of convenient recovery and low loss.In the heterogeneous catalytic system,the immobilized catalyst has been widely used due to its advantages of simple preparation process and good stability.Oxidative desulfurization processes are frequently taking transition metal catalysts as oxidative catalysts.Common carriers are including activated alumina,molecular sieves,and zirconia.In this paper,nanosized SBA-15 molecular sieves were selected as carriers,and Mo-based catalysts were selected as catalysts by comparing the desulfurization performance of different transition metal catalysts.A series of M0O3/SBA-15 catalysts were prepared by impregnation method and its catalytic oxidation desulfurization performance was investigated under different reaction conditions.when Mo loading was 15%(wt%),reaction temperature was 60 ?,oxidant amount was n(O)/n(S)=8,reaction time was 1 h and catalyst dosage was 30 mg,the highest DBT conversion rate can reach 84%.Under this condition,the desulfurization rate is reduced to 76%when the catalyst was regenerated and reused for the fifth time.In order to improve the catalytic oxidation desulfurization performance and stability of the previously prepared catalysts,two kinds of modification method were taken:Na modification and Ce modification.The Na-MoO3/SBA-15 catalysts and Ce-MoO3/SBA-15 catalysts were prepared by co-impregnation method respectively and their catalytic oxidation desulfurization performances were investigated under different reaction conditions.When the molar ratio of Na/Mo is 0.1,the reaction temperature is 60?,the amount of oxidant is n(O)/n(S)=8,the reaction time is 1 h,and the catalyst dosage is 20 mg,the highest DBT conversion rate can reach 93%.Under this condition,the desulfurization rate is reduced to 83%when the catalyst was regenerated and reused for the fifth time.Compared with the unmodified catalyst in chapter 3,the Na modified catalyst not only saves one-third of the catalyst dosage,but also has much better catalytic oxidation desulfurization performance and stability.When the molar ratio of Ce/Mo is 0.2,the reaction temperature is 60?,the amount of oxidant is n(O)/n(S)=8,the reaction time is 1 h,and the catalyst dosage is 20 mg,the highest DBT conversion rate can reach 94%.Under this condition,the desulfurization rate is reduced to 89%when the catalyst was regenerated and reused for the fifth time.Compared with the unmodified catalyst in chapter 3,the Ce modified catalyst not only saves one-third of the catalyst,but also has much better catalytic oxidation desulfurization performance and stability.Compared with the Na-modified catalyst prepared in chapter 4,Ce modified catalyst has much better stability.