The Exploration Of Highly Efficient And Stable Catalysts For The Condensation Of Ethanol To N-butanol

As an important organic intermediate,n-butanol is widely used in the production of medicine,coating and fine chemical products.In addition,n-butanol as a new gasoline additive and substitute has attracted worldwide attention.With the development of global industry,the demand for fossil fuels is increasing,resulting in the depletion of non-renewable energy.The use of traditional energy can bring great pollution to the environment,which seriously influence health and life of human beings.Therefore,we try to find a clean and sustainable fuel as a substitute for petrol.Compared with ethanol,n-butanol has more advantages:its physical and chemical properties are closer to gasoline,and it has a higher mixing ratio with gasoline;The energy density of n-butanol is about 30%higher than that of ethanol;N-butanol is not soluble in water and easy to separate;N-butanol has no corrosive effect on the engine and automobile pipeline,so there is no need to modify the existing automobile engine;So n-butanol has great potential as a substitute for gasoline.The traditional methods for preparing n-butanol in industry mainly include propylene carbonyl synthesis,acetaldehyde condensation and biological fermentation.But these methods have some problems,such as complicated processes,high equipment requirements,environmental pollution and low yield of n-butanol,Therefore,it is urgent to adopt a more green and efficient synthetic route to prepare n-butanol.The green and environmentally friendly process route using ethanol as the raw material to synthesize butanol via the Guerbet reaction path has the characteristics of short process,clean process and low cost.It is the most competitive reaction path at present and has attracted the attention of many researchers.In this work,we prepared a series of magnesium-aluminum based catalysts by a co-precipitation method and systematically compared the performance of these catalysts.The results show that the acidic centers can promote the dehydration of ethanol to form ether,while the basic centers are suitable for the dehydrogenation of ethanol to form aldehyde and acetaldehyde condensation reaction.The recombination between magnesium and aluminum weakens the number and strength of the acid or basic centers on the surface of the single oxide,which facilitate the conversion of ethanol at low temperatures.When the metal center is introduced into the magnesium aluminum composite catalyst system,the conversion rate of ethanol at low temperature is obviously improved,which makes the process of ethanol dehydrogenation easily.We also prepared a kind of mesoporous carbon(MC)with a large number of oxygen-containing functional groups and high specific surface area.Using this carbon as a support,a catalyst with highly dispersed ceria and copper nanoparticles was prepared by a two-step impregnation method.We systematically investigated the influence of the loading amount of ceria and copper,reaction temperature,different supports and components on the catalytic performance and the stability of the optimized catalyst.The results showed that Cu-CeO_x/MC catalysts with a copper load of 10 wt%and a cerium load of 7.3 wt%had better catalytic performance,the conversion of ethanol can reach 54.9%and the yield of n-butanol reached 23.5%.The catalytic performance maintained good stability in 110 h long-term reaction.Characterization results show that cerium oxide exists in a highly dispersed form on the surface of the catalyst.Compared with bulk cerium oxide,this highly dispersed cerium oxide contains a large number of oxygen defects,the presence of a large number of oxygen defects will cause the catalyst to produce much more basic centers,which is more suitable for the acetaldehyde aldol condensation.Compared with other supports,mesoporous carbon cause cerium oxide uniformly dispersing on the surface of the catalyst.The resultant catalysts expose more active centers and could be fully in contact with the reactants,which are beneficial to improve the catalytic performance of catalysts.In conclusion,a series of catalysts with excellent catalytic performance and stability were prepared for the condensation of ethanol to n-butanol,which could provide a reference for the development of highly efficient catalysts for condensation reactions.