One-pot Green Synthesis Based On Metal Oxide Composite Catalytic Material

Catalysis is the core technology of modern chemistry and chemical engineering,which not only promotes the process of human industrial civilization,but also plays an important role in modern life.In different fields of heterogeneous catalysis,metal oxides have been widely concerned by various industries because of their unique properties and high economic benefits.At present,metal oxides are common as carriers,but the interaction between metals and carriers and the influence of the properties of carriers on catalysts are still being discussed.One-pot reaction can combine multiple reaction steps in the same reaction container,which not only avoids the separation of intermediates,simplifies the operation process,but also minimizes the discharge of chemical waste,and has the advantages of being more green and efficient.However,the one-pot reaction system is complex,so it is very important to develop multifunctional green catalysts with high performance to improve the efficiency of one-pot reaction.Therefore,based on two kinds of one-pot reactions,two kinds of corresponding heterogeneous catalyst systems were established by adjusting the precursors and synthesis schemes in the preparation process.The research content of this paper mainly includes the following five parts:（1）According to the acid site properties ofγ-Al₂O₃,in order to improve its application effect,we adopted the method of alkali metal modification to further optimize its surface properties.As far as the preparation effect is concerned,the carrier modified by alkali metal significantly improves the loading capacity of the supported metal;As far as catalytic activity is concerned,the catalyst prepared by alkali metal modified carrier not only improves the yield of 2-methylbenzimidazole,but also improves the recyclability of the catalyst.（2）In view of the complicated process of modifying the carrier by alkali metals,the use of hydroxide of supported metal onγ-Al₂O₃ is expanded,which plays the role of in-situ modification.High temperature roasting is not needed,so that the specific surface area of the catalyst is higher,the preparation process is safer and more environmentally friendly,and the preparation efficiency of the catalyst is more efficient.The catalytic activity is further improved,and the selectivity and yield can reach>99%.And the stability of the catalyst is stronger.The stability experiment shows that the catalyst can be reused for 8 times,and the catalytic activity is not significantly reduced.The in-situ modified catalyst also has higher universality,and it can still maintain a high yield after replacing the reaction substrate.For this one-pot method,metal Cu is the active metal in the first step and the whole reaction rate-controlling step,and increasing the loading of metal Cu is helpful for alcohol dehydrogenation.In addition,compared with strong acid and strong base sites,weak acid and acidity in the catalyst are more favorable for the reaction.Then the heterogeneous catalysts prepared by CeO₂and ZrO₂as catalysts,carriers and dopants were studied for the one-pot synthesis of carbonate derivatives from carbon dioxide and alcohol.（3）Contradictions in the research of CeO₂ and ZrO₂ as catalysts for the one-pot conversion of carbon dioxide in the current literature,this paper explores.It is undeniable that both metal oxides have the activity of one-pot conversion of carbon dioxide,but the two catalysts have different activities after being improved by making oxygen vacancies and metal doping.Aging and roasting in the preparation process of catalyst are important steps to control the morphology of catalyst,which will also affect the crystal face finally exposed.（4）In view of the low efficiency of CeO₂ and ZrO₂ as catalysts for one-pot conversion of carbon dioxide,bimetallic solid solutions were prepared in different proportions,and the differences between solid melts and single oxides were explored.It was found that the morphology and performance of the catalyst changed with the change of the ratio of the two metals,but there was no result that the performance of one metal was clearly better than the other.No matter whether the proportion of Ce is high or the amount of Zr is more,there are respective optimal doping ratios.（5）In order to improve the catalytic activity of CeO₂ by increasing the ratio of Ce with valence+3 to Ce with valence+4,the cerium oxide cluster doped CeO₂ was prepared by co-aging the cerium oxide cluster with the precursors of different metal Ce.It was found that the morphology and performance of the catalyst changed with the change of the doping ratio of cerium oxide clusters.It is found that the precursor of metal Ce with different valence states has little effect on the activity of the final catalyst,but it is found that the precursor with+3 valence is beneficial to improve the catalytic activity by modulating the cerium core of cerium oxide clusters with different valence states.