Preparation And Catalytic Performance Of Carbon Aerogel Supported Copper Catalysts For The Hydrogenation Of Methyl Acetate To Ethonal

Ethonal,as a clean and efficient and replaceable source of energy,plays a key role and has important application prospects in our country's sustainable development strategy with the gradual scarcity of global oil resources and the rise in prices.The technics of hydroganation of methyl acetate to ethonal,a new technology of ethanol production with obvious advantage,promote the harmonious development of environment and economy and are getting more and more attention.The core of the technology is the development of catalysts and the one of the main directions is preparation of catalysts with excellent catalytic activity.Properties of the catalyst support are the key factors that affect the performance of the catalyst.Furthermore,the dispersion,size and valence of copper nanoparticles can be improved by using supports with different properties or by adjusting their physical and chemical properties,so as to improve the catalytic performance of catalysts.In this paper,the connection between characteristics and activities of the catalysts has been discussed combine with related characterizations.The carbon materials are used for a catalyst support that has the characteristics of excellent physical and chemical properties and is easy to be adjusted,thus having excellent and wide application value.In this paper,activated carbon aerogels?ACAs?were prepared by mixing sol-gel method,template method and chemical activation method.After the ACAs supported copper,the catalysts were used in hydrogenation of methyl acetate?MA?to ethanol.The effects of water bath temperature and time and KOH activation on the structure and physicochemical properties of supports were discussed.A catalyst containing a large amount of microporous and oxygen-containing functional groups is constructed,and the dispersion,size and valence state of the copper nano-particles were effectively controlled,and further improve the catalytic performance.My research contents are following:1.In the process of preparing the initial support CAs,on the one hand,silica was used as the template and the template were removed at the later period to make the porous structure form in the support.On the other hand,the pore size,specific surface area and the number of micropores in CAs can be controlled by changing the temperature and time of water bath and calcination rate.when the water bath temperature,the resting time and the calcination rate were 50°C,6 h and 5°C/min,respectively,the area of support and the number of micropores is the largest;2.The effect of different content of B on Cu-CAs catalyst was studied.The results showed that when the mass content of B was 3%,the activity of catalyst Cu-3BCAs was the best.The conversion of MA and ethanol selectivity over catalyst Cu-3BCAs were 90.5%and 59.4%,respectively.After the analysis judgments,it howed that the catalyst had higher copper dispersion and smaller copper particle size.Besides,the addition of element B effectively enhanced the interaction betweensupports and copper particles.On the other hand,the presence of some macropores contributed to the transfer of reactants.All properties provided excellent conditions for the reaction and reduced the selectivity of byproducts.As a result,the catalytic performance was better than that of other catalysts;3.During the preparation of activated carbon aerogels,potassium hydroxide was used to activate the initial CAs,and the obtained specific surface area of ACAs,the micropore content and pore volume increased with the increase of the mass ratio of potassium hydroxide and CAs.Besides,micropores have anchoring effect on metal nanoparticles,and contribute to increasing the dispersion of copper,forming smaller copper particle size and changing the content of different copper valence states.Thus that affect the catalytic hydrogenation activity;4.The activation of potassium hydroxide,on the one hand,significantly changed the physical properties of carbon carriers,and on the other hand,increased the oxygen-containing mainly including C=O,COOH and OH functional groups on the surface of supports.With the increase of the amount of potassium hydroxide,the content of various oxygen-containing functional groups also increased,which enhanced interaction force between supports and copper nanoparticles.The strong interaction can effectively promote the formation of copper nanoparticles with smaller average particle size,increament of copper dispersion and specific surface area,influence of copper valence state content,and improvement of the catalytic activity of copper-based catalysts for hydrogenation;5.The activity of Cu-ACAs for the hydrogenation of MA to ethanol was evaluated.The results showed that under the conditions:2 h^-1 of liquid space velocity,10 h of reaction time,T=330°C,P=2.0 MPa,and the MA sample size of 0.023 mL/min.When the dosage ratio of potassium hydroxide and CAs varied from 0 to 6,the catalytic performance showed volcanic type curve.When the mass ratio was 4,the best catalytic activity was abtained.The conversion of MA and selectivity of ethanol reached 95.2%and 62.2%,respectively.The results proved that the large specific surface area,a large number of micropores and functional groups provided favorable conditions for the reaction.Namely,the increased dispersion and specific surface area of copper,smaller average size of copper particles and more content of Cu⁺,thus results howed high hydrogenation activity.