Ni/ZrO2 catalysts for ethanol steam reforming: effect of Ca-doping

Ni/ZrO2 catalysts doped with various percentage of CaO were synthesized and used in the steam reforming of ethanol for hydrogen production. The addition of CaO to the support decreases the Lewis acidity of zirconia, which contributes to the side reactions that lead to coke deposition. Moreover, the replacement of the Zr4+ cation in the ZrO2 lattice with cations with lower positive charge, as Ca2+, generates oxygen vacancies which modify the interaction between the active phase and the support and activate CO2, thus favoring the gasification of coke. The sample doped with the maximum percentage of CaO presents an optimum carbon balance, which can enhance the catalyst durability