Modified Molybdenum-tin Catalyst Used For Dimethoxymethane Synthesis From Dimethyle Ether Oxidation

As a new type of diesel additive,dimethoxymethane is applied to automobile engine fuel,which effectively reduces the emission of nitrogen oxides in automobile exhaust gas without changing the working conditions of the engine,it improves the thermal efficiency,reduces the cost of using diesel oil.In addition,dimethoxymethane has good physical properties such as low toxicity,good water solubility and volatility,so that it can be used in the processing and production of medical drugs and air fresheners,dimethoxymethane can also be used as a substitute for Freon in the production of air conditioning refrigeration products.Dimethoxymethane is a new environmental friendly chemical and plays an important role in the green chemical process.The VO_x-MoO₃/SnO₂ catalysts with different loads of VO_x were prepared by co-precipitation method.XRD,BET,NH₃-TPD and CO₂-TPD were used to characterize the catalysts.The results showed that the catalyst had the largest specific surface area and suitable acidity and alkalinity,the selective growth of active components on the catalyst support when VO_x loading was 3.4%,the active components grew preferentially on the catalyst support is more conducive to the selective oxidation of dimethyl ether to dimethoxymethane.The effects of reaction temperature,catalyst loading and reaction time on catalytic performance of catalysts in catalytic oxidation of dimethyl ether were investigated.The results showed that the catalyst had the highest catalytic activity in the second hour when the reaction temperature was 160?and the catalyst loading was 2.5 ml,the conversion of dimethyl ether was 90.47%,and the selectivity of dimethoxymethane was 66.13%.The VO_x-MoO₃/SnO₂ catalyst was modified to prepare a series of modified catalysts with different molecular sieves,the catalyst samples were characterized by XRD,NH₃-TPD,CO₂-TPD and SEM.The test and characterization results showed that the catalytic performance of the VO_x-MoO₃/SnO₂-HMCM-22 catalyst modified by HMCM-22 was the best for catalytic oxidation of dimethyl ether.The reaction conditions of oxidation reaction were tested by single factor,and the optimum reaction conditions were selected.The test result showed that the catalytic performance of the catalyst was the best when the reaction temperature was 160?,the reaction space velocity was 600 h^-1,and the volume ratio of dimethyl ether to oxygen was 3:1,the conversion of dimethyl ether was 84.35%,and the selectivity of dimethoxymethane was improved to 89.59%.The stability of the modified catalyst was improved,the catalyst could maintain high selectivity for about three hours and could be reused.