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 CO 2 hydrogenation was studied over a cheap, widespread and non-precious Cu catalyst in a potassium ion conducting membrane (K-βAl 2 O 3 ) reactor at bench scale, under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H 2 /CO 2 ratios and using gas compositions representative of post-combustion CO 2 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 CH 3 OH and the unusual small selectivity to CO and CH 4 . Selectivities to CH 3 OH, C 2 H 5 OH and C 2 H 6 O were electrochemically enhanced up to a maximum of 34, 22 and 3.4 times, respectively. The optimum temperature for the electrochemically assisted CO 2 hydrogenation was selected to be 325 °C. Higher gas flow rates favoured the synthesis of dimethyl ether at the expense of methanol and ethanol formation. CO 2 conversion increased with H 2 /CO 2 ratio, whereas selectivity to fuels showed a maximum for a H 2 /CO 2 ratio of 2. Selectivity to dimethyl ether follows an opposite trend vs. H 2 /CO 2 ratio with respect to methanol and ethanol ones.