Upgrading of methane emissions via chemical looping over copper-zeolites: Experiments and modelling

The interest in methane direct conversion into methanol has increased in the last years. A copper-mordenite looping process, based on the separation of methanol formation (200 °C) and copper re-activation (450 °C), has been studied. Methane partial pressure (studied in the range 5–100 kPa) had a positive effect on methanol productivity (10.7 μmol/g zeolite at 100 kPa CH4). It was found that the adsorption time had some impact on the productivity; a minimum value of 60 min was needed to reach the equilibrium. Using the experimental results, the equilibrium and kinetics of methane chemisorption were modelled. The proposed model is based on the formation of two adsorbed species: methoxy and CO2-precursors. Many methane emissions and feedstocks are diluted and contain oxygen. Thus, methane adsorption has also been studied at aerobic conditions, to apply the looping conversion of methane into methanol to these sources. High oxygen concentrations were considered (2.5–16 mol%), resulting in a decrease in methanol productivity and the over-oxidation of most adsorbed CO2-precursors during the adsorption step. The model was updated for considering the over-oxidation to CO2.