Reforming of ethanol with carbon dioxide catalysed by silver-promoted copper-ceria-zirconia composites

A CeO2-ZrO2 composite-supported Cu catalyst was prepared by the sol-gel method. The promotion effects of addition of Ag on dry reforming of ethanol were investigated under the conditions of CO2/ethanol ratio 3.4 (mol mol(-1)) and in the temperature range from 625 degrees C to 700 degrees C. It was clarified that using our catalyst system of 10Cu45Ce45Zr, where 10 wt% of copper, 45 wt% of ceria and 45 wt% of zirconia were included, the selective formation of CO and H-2 was achieved in DRE. Furthermore, Ag was added with decreasing copper content and total metal content was adjusted to 10 wt%. It was found for the first time that the conversion of ethanol and yields of CO and H-2 increased with increasing Ag and reached the highest values in 2Ag8Cu67.5Ce22.5Zr although a large amount of coke was also formed. The formation of byproducts, methane, ethane and butane was very low for every catalyst. It was also found from the TG-DTA measurement of the used catalysts that Cu metal species on the 2Ag8Cu67.5Ce22.5Zr catalyst were difficult to oxidize and that the transfer of oxygen to carbonaceous species forming CO would be promoted on the reduced Cu species. Furthermore, it seems that dispersed Ag species could keep Cu species reduced.