The influence of physico-chemical properties of TiO2 on photocatalytic generation of C1-C3 hydrocarbons and hydrogen from aqueous solution of acetic acid

The present study was focused on the influence of physico-chemical properties of TiO2 on a photocatalytic generation of useful C-1-C-3 hydrocarbons (mainly methane) and hydrogen from aqueous solution of acetic acid under N-2 atmosphere. The photocatalysts applied in the study were prepared from a crude TiO2 obtained by the sulphate technology. The crude TiO2 was calcined at the temperatures of 600, 700 or 800 degrees C in air atmosphere. Moreover, two commercially available photocatalysts, Aeroxide (R) P25 and VP TiO2 P90 (Evonik, Germany) were also used in the experiments. The photocatalysts were characterized by UV-vis/DR and FOR spectroscopy, N-2 adsorption-desorption at 77 K and XRD measurements. The main gaseous products of CH3COOH decomposition were CH4 and CO2. Moreover, small amounts of ethane, propane and hydrogen were detected in the gaseous phase. The main by-products identified in the liquid phase were methanol, ethanol, acetone, acetaldehyde and methyl acetate. The most active photocatalyst towards hydrocarbons and H-2 generation was TiO2 calcined at 700 degrees C. The catalyst was composed mainly of anatase (94%) with crystallite size of 32 nm and exhibited BET surface area of 30 m(2)/g. After 27 h of the process conducted with this catalyst the concentrations of CH4, CO2, C2H6, C3H8 and H-2 amounted to 2.92, 2.68, 0.25, 0.08 and 0.22 mmol/g of photocatalyst, respectively. It was found that the main parameters responsible for the photoactivity of the photocatalysts were crystallite size of anatase, phase composition and activity towards hydroxyl radicals formation. (C) 2011 Elsevier B.V. All rights reserved.