Sol-Gel controlled dispersion of Nb within TiO2 to obtain water tolerant catalysts with tunable acid-base properties for dihydroxyacetone transformation

Nanostructured Nb doped TiO2 were prepared by a novel Sol-Gel method using new N-methyldiethanolaminemodified precursors of Ti (IV) and Nb(V). Co-hydrolysis of Ti(IV) and Nb(V) precursors in suitable ratio resulted in the introduction of atomically dispersed Nb cation, along with the formation of small Nb oxo clusters homogenously dispersed within the TiO2 matrix. Characterizations showed a progressive decrease of the crystallinity as well as an increase in the defects and the BET surface areas of the TiO2 nanoparticles with the Nb doping. Upon Nb doping, gas phase calorimetry of NH3 and CO2 adsorption, evidenced the acidity but also the basicity increase. The aqueous phase dihydroxyacetone conversion increased significantly over Nb/TiO2 as compared to undoped TiO2. However, upon increasing the Nb doping, the base-catalyzed pathway, which forms hexoses from DHA, became the prevailing mechanism at the expense of the usual acid-catalyzed pathway leading to formation of Pyruvaldehyde.