The formation of methanol from glycerol bio-waste over doped ceria-based catalysts

A series of ceria-based solid solution metal oxides were prepared by co-precipitation and evaluated as catalysts for glycerol cleavage, principally to methanol. The catalyst activity and selectivity to methanol were investigated with respect to the reducibility of the catalysts. Oxides comprising Ce-Pr and Ce-Zr were prepared, calcined and compared to CeO₂, Pr₆O₁₁ and ZrO₂. The oxygen storage capacity of the catalysts was examined with analysis of Raman spectroscopic measurements and a temperature programmed reduction, oxidation and reduction cycle. The incorporation of Pr resulted in significant defects, as evidenced by Raman spectroscopy. The materials were evaluated as catalysts for the glycerol to methanol reaction, and it was found that an increased defect density or reducibility was beneficial. The space-time yield of methanol normalized to surface area over CeO₂ was found to be 0.052 mmol_MeOHm^-2h^-1, and over CeZrO₂ and CePrO₂, this was to 0.029 and 0.076 mmol_MeOHm^-2h^-1, respectively. The inclusion of Pr reduced the surface area; however, the carbon mole selectivity to methanol and ethylene glycol remained relatively high, suggesting a shift in the reaction pathway compared to that over ceria. This article is part of a discussion meeting issue 'Science to enable the circular economy'.