LED-driven continuous flow carbon dioxide hydrogenation on a nickel-based catalyst

Abstract

Methane can be obtained from the direct hydrogenation of CO2 via the Sabatier reaction. This reaction is usually performed at high temperatures and/or pressures but it has been recently reported that in the presence of certain nanostructured catalysts, CO2 methanation can proceed at lower temperatures in solar photo-assisted processes. In this study, an inexpensive and commercially available nickel-based catalyst (Ni/Al2O3·SiO2) has been selected to perform the continuous CO2 hydrogenation in a fixed bed photocatalytic reactor using high-radiance/low consumption light emitting diodes (LEDs). These illumination conditions allowed us to attain the reaction temperatures required without the need of additional heating sources. Different LED excitation wavelengths and irradiances were evaluated. Under selected irradiation conditions (460 nm wavelength) not only the photothermal but also the photo-catalytic conversion of CO2 into CH4 takes place, with high selectivity. Conversion levels above 70% with production rates of ca. 35 mmol CH4 g−1 h-1 were obtained, outperforming the results obtained by conventional heating methods or with other irradiation wavelengths.