Study On Mg-Al Composite Oxide Catalysts For Acetone Condensation To Isophorone

Isophorone is a kind of organic intermediate with excellent performance,which is widely used in industry and has high economic value.The traditional industrial method on the synthesis of isophorone is acetone liquid phase condensation,but this way will produce a large amount of alkaline wastewater in the production process and cause environmental pollution.As the improvement of environmental protection requirements,using solid base catalysts for the reaction of acetone gas-phase condensation has attracted more and more attention.However,the solid base catalysts used still have some problems,such as the catalyst activity needs to be improved and the selectivity of the target product is poor.In this thesis,the Mg-Al composite oxide solid base catalysts were selected as the research object.The research compared the catalytic performance of Mg-Al composite oxide catalysts prepared by different methods(including co-precipitation method,hydrothermal method and mechanical mixing method),the catalytic performance of Mg-Al composite oxide catalysts with different Mg-Al ratios,and the catalytic performance of different Magnesium based composite oxide(Mg-Al,Mg-Ti,Mg-Si).Furthermore,the effects of addition of acid or alkaline oxides and double oxides additives on the performance of Mg-Al composite oxide catalysts were investigated as well.And the effects of the surface properties on the catalyst activity and product distribution were investigated with XRD,TPD and other spectroscopic means.The paper concludes the following points:The catalysts were easily prepared by mechanical mixing method with high catalytic activity and good stability.The Mg-Al composite oxide catalyst showed the best activity compared to Mg-Si composite oxide and Mg-Ti composite oxide,while the Mg-Si composite oxide catalyst increased the selectivity of trimethylbenzene in the product.The suitable Mg-Al ratio for the preparation of Mg-Al composite oxide was 1.2:1.When using Mg1.2Al1 composite oxide doped with 2%zirconium oxide as the catalyst,the acetone conversion was 32.6%,the isophorone selectivity was 30.4%,and the total selectivity of isophorone,mesityl oxide and trimethylbenzene in the product was 98.8%.Further,the Mg1.2Al1Zr composite oxides modified with 1%La metal additives were used as catalyst.The results showed high acetone conversion and isophorone selectivity,with the total selectivity of isophorone,mesityl oxide and trimethylbenzene in the products was 99.2%and the selectivity of isophorone increased to 37.7%.The results of spectroscopic characterization showed that pore structure and the strength and number of acids and basic sites had a great influence on the catalytic activity and the distribution of the products isophorone,mesityl oxide and trimethylbenzene.It was also found that the catalysts roasted at 600℃ had better catalytic activity at the reaction temperature of 280～300℃.