Review of methanol reforming-Cu-based catalysts, surface reaction mechanisms, and reaction schemes

Recent development in proton-exchange membrane fuel cell technology has stimulated research in fuel processing for hydrogen production. Hydrogen can be produced from four different types of methanol reforming processes, namely methanol decomposition, partial oxidation of methanol, steam reforming of methanol and oxidative steam reforming of methanol. This review paper discusses commonly used Cu-based catalysts including their kinetic, compositional, and morphological characteristics in methanol reforming reactions. Although research exploring surface reaction mechanism over various Cu-based catalysts was first attempted about three decades ago, the scheme remains controversial. This technical discussion will focus on the commonly reported surface intermediate species, which are methoxy, formaldehyde, dioxymethylene, formate and methyl formate. The surface reaction mechanism could be complicated by the introduction of reactants such as oxygen and steam, into the system as they would subsequently initiate secondary reactions. Different reaction schemes of methanol reforming are presented.