Structural modifications of calcium based catalysts by non-thermal plasma in the CO2 reforming of CH4 and the influence of water

Calcium oxide, calcium hydroxide and calcium carbonate were tested for the CO2 /CH4 reaction in a dielectric barrier discharge plasma reactor under humid conditions. It appeared that the presence of water in the gas stream enhanced slightly the selectivity to CO and H-2 syngas on each support (2-5 %), contrary to the selectivities to CxHy that decreased (0.5 to 2%). The water showed little effect on oxygenates selectivities (in the order of 0.1%) compared to dry treatment. The three materials were characterized by thermogravimetric analysis and infrared spectroscopy prior and after, dry and humid, plasma treatments. Addition of humidity in the plasma gas stream led to the formation of calcium hydroxide on the surface of CaO and enhanced the carbonation of Ca(OH)(2). We showed that the carbonation of Ca(OH)(2), H2O proceeded through simultaneous CO2 capture and H2O release, highlighting an oscillating behavior.