Effect of pretreatment conditions on acidity and dehydration activity of CeO2-MeOx catalysts

Article abstract of DOI:10.1016/j.apcata.2020.117722

A series of MeO_x-modified CeO₂ (CeO₂-MnO_x, CeO₂-ZnO, CeO₂-MgO, CeO₂-CaO, and CeO₂-Na₂O) catalysts were prepared by the impregnation of CeO₂ with corresponding metal nitrates. Acidity and oxidation state of cerium were investigated on both oxidized and reduced catalysts by employing Fourier Transform Infrared spectroscopy (FTIR) on adsorbed pyridine and in situ H₂-Temperature Programmed Reduction/X-ray Absorption Spectroscopy (H₂-TPR/XAS) techniques, respectively. Metal oxide addition tended to alter both type and number of acid sites on ceria. EXAFS data showed a significant difference in N_Ce-O between unmodified and CeO₂-MeO_x, suggesting that added MeO_x interferes with vacancy formation on ceria during reduction. In comparison with air-pretreated samples, H₂-pretreated ones under similar conversion of 1,5 pentanediol exhibited a higher selectivity towards linear alcohols. Alcohol conversion found to correlate with total acidity (i.e., Br?nsted and Lewis). CeO₂ benefited from the addition of alkali (Na) or alkaline earth metals (Mg, Ca) by producing unsaturated alcohols.