Molecular Sieve And Condensation And Oxidation Of Metal Oxide Catalytic Methanol Synthesis Of Methylal

In this paper,molecular sieves and metal oxides are used to catalyze the condensation and oxidation of methanol.We used HZSM-5 zeolite and its HZSM-5supported metal oxide to study the condensation reaction of aldehydes.The molecular sieves and their metal supported materials were characterized by SEM,XRD,FT-IR and NH₃-TPD.,surface properties and composition of the treated molecular sieves were determined.The molecular sieves HZSM-5 and its supported materials were used as catalysts to catalyze the condensation reaction of aldehydes,results show,HZSM-5 and its supports have high activity,influence of the acidity of the catalyst on the reaction was discussed,and the reaction was optimized,effects of reaction time,temperature,catalyst dosage and reactant ratio on the reaction were investigated.The optimum process conditions were determined:reaction temperature was 120?,the time was12 h,the amount of catalyst was 0.2 g,and the molar ratio of methanol to trioxazole was7:1.Under this optimization condition,conversion of trioxymethylene was 94.8%,the acetal selectivity was 92.6%,and the yield of methyl acetal was 88.1%.At the same time,the catalytic properties of HZSM-5 supported metal oxides such as CuO,ZnO,Fe₂O₃,Al₂O₃,Ca O and MgO were investigated.Reaction conversion and selectivity were not significantly different from those of HZSM-5.In addition,the bifunctional catalyst SO₄^2-/V₂O₅-ZrO₂ was prepared by impregnation method,prepared catalysts were characterized by XRD,SEM,TEM,FT-IR,XPS and N₂ adsorption-desorption techniques,determine the composition and structure of the material;surface acidity and redox properties of bifunctional catalysts were studied by NH₃-TPD and H₂-TPR.The prepared catalyst was used to catalyze the direct oxidation of methanol to the synthesis of methylal,showing excellent catalytic performance,conversion of methanol was 29.2%and the selectivity of methylal was96.0%.As a result of surface analysis,activity of the catalyst is mainly due to the presence of V₂O₅ redox activity on the surface,and the acidic active sites SO₄^2-.The reaction was optimized to determine the optimum reaction conditions:reaction time 12h,catalyst dosage 0.2 g,O₂ pressure 1 MPa,temperature 180?.And the re-use performance of the catalyst was studied,results show that the recycled catalyst can still maintain high activity and selectivity.