The Study Preparation Of Novel Porous Catalytic Materials And Their Carbon Dioxide Addition Reactions

Carbon dioxide is the most important gas in the greenhouse effect.On the other hand,carbon dioxide is also the most abundant C1 raw material on the earth.It is a hot spot of current research how to convert carbon dioxide into high value-added chemical products.The reaction of carbon dioxide with epoxides to form cyclic carbonates is the most promising route in the conversion of all carbon dioxide.However,due to the high chemical stability of carbon dioxide,it has been reported that the catalyst for catalyzing the cycloaddition of carbon dioxide with epoxides to form a cyclic carbonate is not catalytically active or difficult to separate from the product.It is an urgent problem to develop a highly efficient and easily separable heterogeneous catalyst of the reaction of carbon dioxide with epoxides to form cyclic carbonates.Therefore,the research work in this thesis focuses on the development of high-efficiency catalysts for the formation of cyclic carbonates from carbon dioxide and epoxides.The first type of catalyst is a metal organic framework（MOFs）catalytic system.In this study,Zn（II）and terephthalic acid（bdc）,3-amino-1,2,4,-triazole（atz）were used to construct a microporous MOF[Zn（atz）（bdc）_0.5].It was found that Zn（atz）（bdc）_0.5 can catalyze the reaction of carbon dioxide and epoxides at a reaction temperature of 60℃and a carbon dioxide pressure of 1 MPa with n-butylammonium bromide（TBAB）as a cocatalyst.,The conversion of propylene oxide can be as high as 97%,and the selectivity of propylene carbonate（PC）is greater than 99%when the PO.In addition,the microporous Zn（atz）（bdc）_0.5 has a high selectivity for the substrate of the cycloaddition reaction,and the conversion of epoxides is rapid reduction when PO is replaced with other larger epoxides.However,due to the co-catalyst TBAB can be dissolved in the reaction system,It is difficult to separate TBAB from the cyclic carbonate.and its application is limited.The second type of catalyst is a high nitrogen content porous carbon material catalytic system.In this study,melamine cotton was used as a precursor,and various porous carbon catalysts with different nitrogen and oxygen contents were synthesized at different temperatures and different mass ratios of carbonized precursor and potassium hydroxide.The porous carbon is applied to the cycloaddition reaction of carbon dioxide and epichlorohydrin without the aid of any co-catalyst,and the pressure of carbon dioxide is normal pressure,the reaction temperature is 100℃,and the catalyst is only 1%of the mass of epichlorohydrin.At the same time,the conversion of epichlorohydrin is as high as 94%and the selectivity of carbon carbonate is as high as 98%,which solves the problem that the separation of the product from the reactants and the catalyst.What is more,this study also found a synergistic effect on the cycloaddition reaction of carbon dioxide when pyridine nitrogen and hydroxyl groups coexist.Porous carbon is expected to be a next-generation catalyst for carbon dioxide and cycloaddition to form cyclic carbonates due to its high catalytic activity,its own high stability,and its low cost and easy availability.