Study On High Performance ZnO-based Catalyst For Hydrogen Production From Dimethyl Ether Steam Reforming

Proton exchange membrane fuel cells(PEMFC)fueled by hydrogen have received widespread attention due to its advantages of high energy conversion efficiency,high energy density,low pollutant emissions or zero emissions.It is widely regarded as a clean and sustainable energy conversion technology to replace the increasingly scarce fossil fuels,and is also an ideal power source for fuel vehicle cells.However,the supply of high-quality hydrogen source is one of the main reasons that hinder the commercial application of PEMFC.Among the hydrogen production technology of hydrogen-containing compounds,dimethyl ether steam reforming is expected to meet the requirements of PEMFC for high-quality hydrogen due to its mild reaction conditions,easy operation,high reforming efficiency and less by-products.The key of steam reforming of dimethyl ether for hydrogen production is to develop catalysts with high hydrogen production rate,low CO selectivity,excellent carbon deposition resistance and stability.In this work,a series of zinc-based oxide catalysts were prepared and their catalytic properties of dimethyl ether steam reforming for hydrogen production were investigated.The catalyst was characterized by XRD,N2 adsorption-desorption test,NH3-TPD,H2-TPR,TEM,TGA,XPS,Raman spectroscopy and so on.The relationship between the structure and properties of the catalyst was analyzed.(1)ZnO-ZrO2 solid solution catalyst was prepared by coprecipitation method,and its catalytic performance for methanol/dimethyl ether steam reforming to produce hydrogen was also investigated.The effect of ratio of ZnO-ZrO2 to solid acid ?-Al2O3 and ZnO content was discussed.The results showed that the optimum content of ZnO in solid solution was 13%.The corresponding catalyst 13%ZnO-ZrO2 showed excellent performance in methanol steam reforming for hydrogen production.At 420?,methanol conversion was 98% and hydrogen yield was 99.9%,the CO selectivity was only 6.9%.when the mass ratio of 13%ZnO-ZrO2 to solid acid ?-Al2O3 was 2:1,the 13%ZnO-ZrO2/?-Al2O3-2:1 catalyst exhibited excellent catalytic performance for dimethyl ether steam reforming.When the reaction temperature was 380?,the conversion of dimethyl ether was 96% and the yield of hydrogen was 99%.In the stability test for 48 h,the catalyst had good catalystic performance,the yield of hydrogen was maintained about 90%.(2)CeXZr1-XO2 solid solution carriers with different Ce/Zr molar ratio was prepared by coprecipitation method,and the active component ZnO-loaded dimethyl ether steam reforming hydrogen catalyst was constructed.The effects of ZnO loading and different CeXZr1-XO2 support on the activity of the catalyst were investigated.The activity test showed that when the reaction temperature was 420?,the ZnO loading was 10wt% and Ce/Zr molar ratio was 3/7,the catalyst 10ZnO/Ce0.3Zr0.7O2/Al2O3 had excellent catalytic performance and the conversion of dimethyl ether was 99%,hydrogen yield was 96.8%,and the CO selectivity was 7.7%.In the temperature range of 360~460?,the methane by-product selectivity was less than 1%.Furthermore,in the 48 h stability test,10ZnO/Ce0.3Zr0.7O2/Al2 O catalyst showed good catalytic activity.