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

Abstract

Dry and combined (with O 2 ) reforming of synthetic biogas were studied at 700 °C using 0.5 % Rh catalysts prepared by impregnation on different supports: γ-Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 and CeO 2 . Gas hourly space velocity (GHSV) was varied between 150 and 700 N L CH 4 /(g cat ·h), and two O 2 /CH 4 molar ratios of 0 and 0.12 were studied. Rh/Al 2 O 3 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/SiO 2 > Rh/ZrO 2 ≈ Rh/CeO 2 > Rh/TiO 2 . 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 CH 4 conversions and syngas yields could be achieved, as well as increasing CO 2 conversions, though at the expense of lower H 2 /CO molar ratios.