Toward Understanding Metal-Catalyzed Ethanol Reforming

Steam reforming of ethanol (SRE) is a strategic reaction for H-2 production. However, despite considerable work, several aspects of the mechanism and catalytic system for this reaction are not fully understood. There have been many efforts to improve the understanding of the catalysts' behavior during SRE, using both theoretical studies and experimental investigations based on operando characterization techniques. Even though cobalt and nickel are considered the most promising catalytically active metals for industrial SRE, acquiring further knowledge on the reaction mechanism, metal support interactions, and catalyst deactivation (due to carbon accumulation, sintering, or metal oxidation) will enable the successful design of new and stable catalysts. In this review, we analyze the reaction pathways for metal-catalyzed SRE and discuss the available experimental and theoretical data to suggest alternatives to address three major issues: (i) the impact of particle size and metal oxidation state in the SRE performance; (ii) the importance of metal surface electronic properties to obtain a balanced and stable catalyst; and (iii) the influence of support on the catalyst selectivity and stability. Clarification of these issues is a key point for understanding the SRE reaction and for the development of new high performance catalysts.