Auto-thermal and dry reforming of landfill gas over a Rh/γAl2O3 monolith catalyst

Abstract

Auto-thermal and dry reforming of methane and carbon dioxide mixtures was investigated experimentally at temperatures between 300°C and 800°C at atmospheric pressures using a Rh/γAl2O3 monolith catalyst. CH4:CO2 ratios of 1:1 and 1.4:1 were tested. The Rh catalyst reached equilibrium conversions of CH4 and CO2 to H2 and CO for both CH4:CO2 ratios. Equilibrium analysis shows that carbon formation is likely for dry reforming but not for auto-thermal reforming. Experimentally, carbon formation was seen after long-term exposure to 1.4:1 CH4:CO2 ratios without oxygen, but the catalyst has shown the ability to be regenerated in air. Auto-thermal tests, with and without external heat input, operating at an equivalence ratio of 4.3 (O2:CH4=0.46) and maintaining the CH4:CO2 ratio of either 1:1 or 1.4:1, did not show signs of carbon formation or deactivation. ATR experiments resulted in H2:CO ratios between 1.0 and 2.0 that can be tuned depending on the monolith temperature, beneficial in the case of downstream Fischer–Tropsch processes. For the auto-thermal experiments, theoretical reaction extents were calculated based on experimental data and showed two primary regimes in catalyst operation: a CH4 combustion and partial oxidation regime, and reforming and water–gas shift regime.