Remarkable performance of supported Rh catalysts in the dry and combined reforming of biogas at high space velocities

Dry and combined (with O2) reforming of synthetic biogas were studied at 700 °C using 0.5 % Rh catalysts prepared by impregnation on different supports: γ-Al2O3, SiO2, TiO2, ZrO2 and CeO2. Gas hourly space velocity (GHSV) was varied between 150 and 700 N L CH4/(gcat·h), and two O2/CH4 molar ratios of 0 and 0.12 were studied. Rh/Al2O3 catalysts (prepared using two different commercial supports here denoted as Sph and AA) presented the highest biogas conversion and syngas yields under both dry and combined reforming conditions. Catalytic activities were as follows: Rh/AA ≈ Rh/Sph > Rh/SiO2 > Rh/ZrO2 ≈ Rh/CeO2 > Rh/TiO2. The effect of catalysts’ calcination pre-treatment at relatively low (200 °C) and high temperatures (750 °C) was also studied. Calcination at high temperatures had a detrimental effect on both dry and combined reforming activities. However, a positive effect on the reforming activities and syngas yields was observed when the catalysts were calcined at 200 °C, especially under biogas combined reforming conditions: higher CH4 conversions and syngas yields could be achieved, as well as increasing CO2 conversions, though at the expense of lower H2/CO molar ratios.