Study On The Preparation Of Cu Based Catalyst By Solid State Grinding And Its Performance For Low-temperature Methanol Synthesis

Methanol synthesis from CO/CO2/H2 is thermodynamically advantageous at low-temperature.However,at low-temperature the feed gas is difficult to activate on the catalyst surface and shows low reactivity.Besides,the conventional preparation of catalysts needs more steps and discharges much wastewater.The solid-state preparation is step-less and effective which attracts interest of researchers.Considering the demand on catalytic activity,CuZnO,CuMgO,and CeO2/ZrO2 modified catalysts for low-temperature methanol synthesis were prepared by the solid-state grinding method.Their physicochemical properties were characterized by means of XRD,N2 physical adsorption,SEM,XPS,CO/CO2-TPD,TG-DSC and N2O titration.Effects of Cu content and CeO2/ZrO2 modification on the catalytic performance were studied aiming to provide reference for catalyst development toward lowtemperature methanol synthesis.Using formic acid assisted solid-state grinding method,CuZnO in molar ratio of x:1(x=1,2,3,4,5)and CuMgO in molar ratio of y:1(y=1,2,3)were prepared.With increase in the Cu content,the Cu dispersion on CuZnO decreased.The catalytic activity at 150℃ and 3 MPa first increased and then decreased;it reached a maximum at x=3.The total carbon conversion of the feed gas and the methanol selectivity increased to 26.55%and 88.01%,respectively.The by-product was ethyl formate.The surface area of CuMgO(1:1)was the largest(38.7 m2/g)exhibiting the best catalytic activity.The conversion of CO2 was 83.50%.The total carbon conversion and the methanol selectivity were 29.81%and 90.94%,respectively.CuMgO showed strong adsorption for CO2 in favor of CO2 converting.Employing the similar procedure CeO2 or ZrO2 modified 3CuZnO and CuMgO were prepared for methanol synthesis at 150℃ and 3 MPa.CeO2 or ZrO2 modification increased the surface area of the catalyst and adding 0.2CeO2 and 0.2ZrO2 showed the best catalytic activity.Compared with CuZnO,the total carbon conversion increased by 3.25%and 7.32%,respectively.The methanol selectivity on 0.2CeO2-3CuZnO,however,decreased.The methanol selectivity on 0.2ZrO2-3CuZnO remained unchanged and the TOF increased from 5.4×10-3·s-1 to 10.8× 10-3·s-1.The reason was that CeO2 and ZrO2 modification increased the surface area of the catalysts and enhanced the adsorption-activation of the feed gas,thus accelerating the reaction.CeO2 or ZrO2 modification did not improve the catalytic performance of CuMgO.CeO2 and ZrO2 co-modified 3 CuZnO improved the dispersion of active Cu.The ratio of CeO2/ZrO2 affected the conversion of the feed gas.For 0.2(CeO2+ZrO2)-3CuZnO,when the molar ratio of CeO2/ZrO2 was 1:9,the highest conversion of CO was 33.81%.As CeO2 was increased,the total carbon conversion decreased whereas the methanol selectivity remained unchanged.Through regulating the preparation and composition of Cu based catalysts,the catalytic activity for methanol synthesis at 150℃ was improved with increased conversion of CO and CO2 and methanol selectivity.