Reducible oxides are considered to be more active than non-reducible oxides in catalytic conversion of biomass to biofuels, but the reasons are unclear and are the object of this talk. The properties of anatase TiO2 and tetragonal ZrO2 (101) surfaces have been studied using DFT calculations with inclusion of dispersion forces. The attention is on the role of surface reduction, either by creation of oxygen vacancies, or by treatment in hydrogen. The presence of reduced centers on the surface of titania or zirconia (either Ti3+ or Zr3+ ions or oxygen vacancies) results in lower barriers and more stable intermediates in two key reactions in biomass catalytic conversion: ketonization of acetic acid and deoxygenation of phenol. The role of supported Ru nanoparticles is also considered. They favour H2 dissociation and hydrogen spillover, resulting in hydroxylated surfaces. H2O desorption from the hydroxylated surfaces may be a relevant mechanism for the regeneration of oxygen vacancies, in particular on low-coordinated sites of oxide nanoparticles. Finally, the role of nanostructuring on oxide reduction is discussed. ZrO2 nanoparticles of diameter of about 2 nm have completely different behaviour compared to the bulk oxide, and are much more reducible. Nanostructured zirconia has a similar behaviour as titania.

TiO2 and ZrO2 in biomass conversion: Why catalyst reduction helps

2019 Fall National Meeting

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