Preparation Of Metal Modified Molecular Sieve Catalyst And Study On Its Catalytic Performance For Isoamyl Alcohol

With the emphasis on environmental issues,the process of.green oxidation of alcohols has been paid more and more attention,In this paper,a series of modified HMS catalysts were prepared and the obtained catalysts were used for the selective oxidation of isoamyl alcohol to isovaleric acid using molecular oxygen(O2)as oxidant under solvent-free condition to investigate the difference of catalytic activities of different catalysts.The parts of catalysts were also characterized.The main issues discussed in this paper include the following:(1)Pure silica molecular sieve HMS and metal-doped molecular sieves Al-HMS and Co-HMS were prepared by sol-gel method,and subsequently metal oxide ZnO was supported on these supports to obtain the catalysts.The samples were characterized by different characterization methods and the catalytic activities of the catalysts for catalytic oxidation of isoamyl alcohol were studied.The results showed that metal heteroatoms being introduced to molecular sieve HMS could improve the dispersion of ZnO species on the support,and the effect of Co-HMS was more obvious;5wt%ZnO/Co-HMS(100)catalyst exhibited excellent catalytic performance with a isoamyl alcohol conversion of 43.6%,isovaleric acid yield of 18.9%,and isovaleric acid selectivity of 43.3%.(2)The effect of the doping content of Co on the catalytic performance of the catalyst was investigated by using Co-doped molecular sieve as catalyst carrier and 5wt%of ZnO loading.The parts of catalysts were analyzed by different characterization methods.The results showed that the doping amount of Co could affect the structural properties of zeolite catalysts.The doping of suitable metal Co could increase the dispersion of the supported active species and enhance the catalytic activity of the catalyst.When the value of Si/Co was equal to 100,the catalytic performance of the synthesized catalyst was better.(3)The effects of the loading amount of ZnO,calcination temperature and ZnO precursor species on the catalytic performance of the catalysts was investigated.The results showed that when ZnO loading was 3wt%,the calcination temperature was 550? and Zn(NO3)2·6H2O was ZnO precursor,the obtained catalyst exhibited the best catalytic activity for the oxidation of isoamyl alcohol to isovaleric acid.(4)Through the discussion of the preparation conditions,the catalyst 3wt%ZnO/Co-HMS(100)was decided the best catalyst.The conditions of the synthesis for the selective oxidation of isoamyl alcohol to isovaleric acid were optimized with catalyst 3wt%ZnO/Co-HMS(100).The experimental results showed that the catalytic reaction conditions significantly affected the conversion of isoamyl alcohol and the yield and selectivity of the target product,isovaleric acid.When the amount of the substrate was 15 mL,the reaction was carried out at 120? for 8 h using 0.5 g of the catalyst,the conversion of isoamyl alcohol,the yield and selectivity of isovaleric acid reached to the highest values and the values was 52.2%,26.9%,51.5%,respectively.The results of catalytic kinetics indicated that the catalyst 3wt%ZnO/Co-HMS(100)could reduce the activation energy of the catalytic reaction system and make the catalytic oxidation reaction proceed smoothly under mild conditions.