PNNL

Abstract

Vanadia supported on well-defned ceria nanocubes are synthesized at various loadings using a liquid-phase chemical grafting technique and are compared to those prepared using traditional incipient wetness impregnation. Raman and IR characterization reveal that, as vanadia loading is increased to near monolayer coverage, vanadia deposited using grafting shows greatly enhanced dispersion (i.e., improved VOx monomer/dimer distribution). Methanol is used as a probe molecule to explore the redox behavior of the catalysts. IR and temperature programmed desorption of methanol show increased CO2 formation occurs on the bare ceria support and increasing the dispersion of vanadia promotes dehydrogenation to formaldehyde due to the inhibited oxygen vacancy formation on VOx/CeO2. Hydrogen temperature programmed reduction demonstrates that the catalyst reducibility and formation of surface oxygen vacancy are directly related to the degree of vanadia oligomerization. The samples prepared using grafting exhibit superior catalytic performance for methanol oxidative dehydrogenation to formaldehyde compared to the impregnated samples, due to the presence of highly dispersed VOx species (i.e., monomers and dimers). Funding This work was supported by U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences for funding this project (DE-AC05-RL01830).