加料方式对共沉淀法制备的Cu/MnO/Al_2O_3催化剂性能的影响

Effect of addition modes on catalytic performance of Cu/MnO/Al_2O_3 catalysts prepared by coprecipitation method

采用共沉淀法制备Cu/MnO/Al2O3催化剂,运用N2吸附-脱附、XRD、XRF和H2-TPR等对其进行表征,并用于乙酸甲酯加氢制乙醇反应,考察共沉淀加料方式对催化剂结构及其催化性能的影响。结果表明,共沉淀时采用的加料方式显著影响制备的Cu/MnO/Al2O3催化剂的织构性质、CuO晶粒大小、还原性能和化学组成,这些因素共同作用决定了催化剂在乙酸甲酯加氢反应中的催化性能。其中,反加法制得的催化剂Cu和Mn组分含量相对比值接近理论值,且具有较高的比表面积和较佳的还原性能,因而表现出最佳的催化性能,在反应温度200℃、压力6.5 MPa、空速0.6 h-1和氢酯物质的量比50条件下,乙酸甲酯转化率和乙醇选择性分别达98.9%和98.1%。

Cu/MnO/Al2 O3 catalysts were prepared by coprecipitation method and were characterized by N2 adsorption-desorption,XRD,XRF,and H2-TPR. The as-prepared catalysts were used for methyl acetate hydrogenation to ethanol,and the effect of addition modes during preparation on their structure and prop-erties was investigated. The results showed that the addition modes of coprecipitation method had greatly influence on the textural properties,CuO particle sizes,reducibility and chemical composition of Cu/MnO/Al2 O3 catalysts,which gave rise to different catalytic performance in the methyl acetate hydrogena-tion reaction. The catalyst prepared by reverse mode（ base to salt）possessed larger specific surface area and higher reducibility,and exhibited the best catalytic properties in the reaction,which could be attributed to desired control of Cu and Mn contents. Under the condition of 200 ℃,6. 5 MPa,LHSV=0. 6 h-1 ,H2/ester molar ratio=50,methyl acetate conversion and the selectivity to ethanol reached 98. 9% and 98. 1%, respectively.