Electrochemical synthesis of fuels by CO2 hydrogenation on Cu in a potassium ion conducting membrane reactor at bench scale

Abstract

The electrochemical synthesis of fuels by CO2 hydrogenation was studied over a cheap, widespread and non-precious Cu catalyst in a potassium ion conducting membrane (K-βAl2O3) reactor at bench scale, under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H2/CO2 ratios and using gas compositions representative of postcombustion CO2 capture exit streams and easily scalable catalyst-electrode configurations, as an approach towards its potential practical application. The Cu catalyst film was deposited by electroless and characterised both as prepared and after testing. The presence of Cu+ and relatively big Cu particles probably determined the high selectivity to CH3OH and the unusual small selectivity to CO and CH4. Selectivities to CH3OH, C2H5OH and C2H6O were electrochemically enhanced up to a maximum of 34, 22 and 3.4 times, respectively. The optimum temperature for the electrochemically assisted CO2 hydrogenation was selected to be 325 ºC. Higher gas flow rates favoured the synthesis of dimethyl ether at the expense of methanol and ethanol formation. CO2 conversion increased with H2/CO2 ratio, whereas selectivity to fuels showed a maximum for a H2/CO2 ratio of 2. Selectivity to dimethyl ether follows an opposite trend vs. H2/CO2 ratio with respect to methanol and ethanol ones.