Acid-base properties and catalytic activity of nanophase ceria-zirconia catalysts for 4-methylpentan-2-ol dehydration

The room-temperature high energy ball-milling technique was used to prepare nanophase Ce1-xZrxO2 (x = 0; 0.2; 0.5; 0.8; 1) catalysts. The acid-base properties of these catalysts were investigated by means of adsorption microcalorimetry, using NH3 and CO2 as probe molecules. The catalytic activity for 4-methylpentan-2-ol dehydration was tested at atmospheric pressure in a fixed-bed flow microreactor. The inclusion of increasingly high contents of zirconium into the ceria lattice has a complex influence on the acidity and basicity of the pure parent oxide, in terms of both number and strength of the sites. A maximum in 1-alkene selectivity is observed for the ceria-rich catalyst and a minimum for the zirconia-rich sample. Catalytic results are correlated with the acid-base properties and can be interpreted in the light of the mechanism formerly proposed for zirconia, ceria and lanthania. Surface conditioning of the zirconia-rich catalyst occurs during the run, resulting in a remarkable variation of selectivity.