Preparation of Fe-modified photocatalysts and their application for generation of useful hydrocarbons during photocatalytic decomposition of acetic acid

The present study was focused on the photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid under N2 atmosphere. The photocatalysts applied in the study were prepared from a crude TiO2 modified with Fe(CH3COO)2 and calcinated at the temperatures of 400, 500 or 600 °C in argon atmosphere. In order to compare the results, the commercially available photocatalyst AEROXIDE® P25 (Evonik, former Degussa, Germany) was also used in the experiments. The photocatalysts were characterized by UV–vis/DR and FTIR spectroscopy, N2 adsorption–desorption at 77 K and XRD measurements. The crystallite size of anatase was in the range of 7–28 nm and the anatase over rutile ratio was from 82:18 to 95:5. The main gaseous products of CH3COOH decomposition were CH4 and CO2. Moreover, ethane, propane and hydrogen were detected in the gaseous reaction mixtures. The most active photocatalyst towards CH4 generation was TiO2 containing 20 wt.% of Fe calcinated at 500 °C. After 27 h of the process conducted with this catalyst the amount of CH4, CO2, C2H6, C3H8 and H2 evolved was 3.36, 2.97, 0.13, 0.01 and 0.14 mmol/mol CH3COOH, respectively. It was concluded that photocatalytic decomposition of organic compounds, such as acetic acid, under N2 atmosphere could be regarded as a method of production of environmentally friendly “photo-biogas”; however, since the yield of hydrocarbons formation was very low, deep and extensive investigations are still necessary in order to improve the efficiency of the process.