| Acetaldehyde is a basic chemical raw material that can produce industrial products such as acetic acid,acetic anhydride,and pentaerythritol.The synthetic routes to access acetaldehyde include the dehydrogenation or oxidation of ethanol,the partial oxidation of hydrocarbons,the direct oxidation of ethylene and the hydration of acetylene.Although the acetaldehyde production by ethylene oxidation has been the main production method of acetaldehyde in the past few decades,due to the energy structure characteristics of China,petroleum resources are increasingly scarce,it has huge coal reserves.Moreover,with the continuous innovation of acetylene technology in oil and natural gas production,the optimization of the production process of acetylene by calcium carbide process has gradually narrowed the price difference between raw materials of acetylene and ethylene.At the same time,the breakthrough in coal acetylene technology has further expanded acetylene production capacity.Therefore,the acetylene process for the production of acetaldehyde has once again become the advantageous route of the domestic acetaldehyde production industry.Acetylene hydration is mainly divided into gas-liquid phase reaction and gas-solid phase reaction.Although the gas-liquid phase reaction has the advantages of mild reaction conditions and easy separation of products,it has a problem of low conversion rate and selectivity.Therefore,this paper mainly studies the use of Cu-based catalysts to catalyze the liquid phase reaction of acetylene hydration,in an attempt to improve the conversion and selectivity of the reaction.The main research contents are:（1）Using copper chloride as the main catalyst,solvents,cosolvents and ligands（Thiosalicylic acid,mercaptosuccinic acid,mercaptoacetic acid,2-mercaptoethanol,methyl thioglycolate and thiodiglycolic acid）were explored.The results show that when H2O is used as the solvent,the reaction proceeds smoothly with a high selectivity.It was found that the conversion rate of acetylene was higher when ammonium chloride was used as the cosolvent.The results showed that the mercaptosuccinic acid had the best catalytic activity as a ligand;we then screened the amount,reaction temperature and reaction space velocity,and the results showed that 0.02 mol mercaptosuccinic acid was added.Under the reaction conditions of 85°C and 40 h-1,the highest catalytic activity was achieved,the conversion of acetylene was at least 34.92%,and the selectivity of acetaldehyde was at least 87.56%.After characterization of the catalyst powder,it can be inferred that the activity of the catalyst caused by the reduction of the cuprous chloride catalyst during the reaction decreases with the reaction time.（2）Based on the previous chapter,we found that the bimetallic catalyst formed when the second metal was added had a great influence on the reaction,so we started a bimetallic catalyst with Cu as the main metal.The results show that the reaction activity is obviously improved when zinc chloride is added,and the conversion of acetylene is obviously improved.At the reaction temperature of 85°C and the reaction space velocity of 40 h-1,the molar ratio of cuprous chloride/zinc chloride is 10/1,the acetylene conversion and acetaldehyde selectivity were 47.55%and 87.75%,respectively.The solids of the catalyst solution showed that the addition of zinc chloride inhibited the reduction of the main catalyst cuprous chloride to increase the catalytic activity.（3）On the basis of this research,we found one thing in common:When the reaction space velocity is smaller,the higher the reactivity,we guess that because at lower reaction space velocity,acetylene has a longer contact time with water,and the reaction is more sufficient.Therefore,we add ionic liquid to the solvent to increase the solubility of acetylene inthesolvent.When1mL1-butylsulfonicacid-3-methylimidazolium trifluoromethanesulfonate was added,the acetylene conversion was 36.88%,and the acetaldehyde selectivity was 88.24%. |
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