Preparation Of Highly Dispersed Zinc Acetate/Ordered Mesoporous Carbon Catalyst And Its Catalytic Performance For Synthesis Of Vinyl Acetate From Acetylnene

The ordered mesoporous carbon materials?OMC?have large specific surface area,large pore volume and adjustable ordered pore structure,they also have good thermal stability,mechanical stability and chemical inertia,as a result they show a broad application prospect in catalysis area.In the industrial application of acetylene gas phase method for producing vinyl acetate,the traditional zinc acetate/activated carbon catalyst shows poor stability,lower activity and short service life.In this paper,using OMC as the catalyst carrier,and through the modification of OMC structure and catalyst preparation process,a series of zinc acetate/OMC catalysts are prepared and applied to the production of vinyl acetate.Firstly,the preparation process of OMC was investigated systematically.Small angle X-Ray diffraction technique was used to investigate the effect of pre-polymerization time,volatilization time,solidification temperature and carbonization heating rate.And the pore structure of OMC was adjusted through adding organic swelling agent TMB in synthesis process.It was found that the sound ordered mesoporous carbon could be prepared with pre-polymerization time of 1 h,volatilization time of 6 h,solidification temperature of 100?and carbonization heating rate of 1?/min.Adding TMB had little effect on the long-range ordered structure,but with the increase of TMB content,the specific surface area,pore volume and pore size were improved.And TMB had greater effect on the mesoporous structure than on the microporous structure of OMC.Based on the studying of each stages in the properation process of OMC,the influences of the preparation process conditions of the OMC–supported zinc actate catalyst and the catalystic activity of catalysts prepared by different methods were investigated.By studying the impregnation time,impregnation liquid concentration and impregnation temperature of excessive impregnation and circulatory impregnation,it was found that excessive impregnation had much better effect than the circulatory impregnation.The catalyst prepared by excessive impregnation with 20wt.%zinc acetate solution impregnating 2 h at 70?showed better catalyst activity which was of 11.74%load of zinc acetate,more uniform loading distribution,acetic acid conversion of 8.6%,and the vinyl acetate selectivity of 94.6%.Next,the effect of loading distribution of zinc acetate by different drying rate was investigated.It was found that loading distribution was more uniform under higher drying rate.Next,the effect of adding co-solvent ethanol was investigated.It was found that with the ethanol added,the loading was increased significantly of zinc acetate and its distribution was more uniform.With the ethanol concentration of 30 wt.%as co-solvent,the load of zinc acetate reached to 24.07%,the acetic acid conversion reached to 62.4%.Finally,it was found that the modification by HNO₃ has little effect on OMC carrier's skeletal structure,but could enhance the oxygen elemental contents and the amount of ester groups on surface significantly,in the meantime the carbonyl groups,carboxylic groups and hydroxyl groups decreased in a small range.With the increase of the HNO₃concentration,the load of zinc acetate was increased,and distributed more uniformly.When modifying OMC carrier using 50 wt.%HNO₃,the load of zinc acetate reached to 30.72%,the conversion of acetic acid reached to 63.5%,and the yield of vinyl acetate reached to 94.4%.