Study of Cobalt Copper Nanoparticles as Catalysts for Ethanol Synthesis from Syngas

Ethanol and higher alcohols have been identified as potential alternative synthetic fuel to be used in automobiles or as a hydrogen carrier for fuel cells. One method of ethanol production is catalytic conversion of syngas derived from natural gas, coal and biomass. According to the study of the heterogeneous catalysts that are employed for ethanol and higher alcohols synthesis, Rhodium-based catalysts give high selectivity towards C₂+ oxygenates, however, their high cost has thrown light on research on less expensive bimetallic catalysts. Cobalt Copper based catalysts have been proposed as an efficient alternative to Rhodium-based catalysts. In Co-Cu based catalysts, CO adsorbs both associatively and dissociatively on different types of sites. Dissociatively adsorbed CO forms surface hydrocarbon species and associatively adsorbed is inserted into these species. Hydrogenation of the resulting intermediate generates alcohols. The effective site pairs for this mechanism is recognized as Co and Cu metal with intimate contact. Conventional catalyst preparation methods cannot create or maintain a surface with close Co and Cu proximity, therefore novel synthesis methods are proposed to synthesize catalysts in an atomic level to maintain high dispersion, small cluster size, and close proximity of Co and Cu. This literature is a comparison of some novel synthesis methods for Co-Cu based catalysts, including electrochemically synthesized nanowire/tube, microemulsions, wet-chemical method and sol-gel. Catalysts were characterized by means of Hydrogen TPR, XRD, XPS and SEM to compare their reduction behavior, dispersion, particle size and site interactions. Activity/Selectivity in CO hydrogenation of these catalysts are performed to compare their overall activity and selectivity towards ethanol and higher alcohols.