Coupling catalysis and gas phase electrocatalysis for the simultaneous production and separation of pure H2 and C2 hydrocarbons from methane and natural gas

Abstract

This study reports the simultaneous production of pure H2 and C2 hydrocarbons (ethane and ethylene) in a solid oxide electrolysis cell coupled with an active catalyst powder bed. For first time, an Ag/YSZ/Ag double chamber cell was used and high yields to both, hydrogen and C2 hydrocarbons were achieved. The separately feeding of H2O and CH4 to the inner and outer chamber of the reactor, respectively, allows to obtain both kinds of products streams. Thus, steam was electrolyzed on the inner Ag electrode of the electrochemical cell (cathode), producing pure H2 (as the first product) and O2− ions, which were electrochemically supplied through the YSZ solid electrolyte to the outer Ag electrode (anode). On this latter, the reaction of the O2− ions and the oxygen evolved with the methane stream led to the production of C2 hydrocarbons (together with CO and CO2 as secondary combustion products). The C2s yield of this outer stream was strongly enhanced by the addition of an active catalyst powder bed (Ce–Na2WO4/SiO2 or Mn–Ce–Na2WO4/SiO2) to obtain the second product stream (with a high C2 yield up to 15%). The influence of the oxidative coupling catalyst powder bed, the reaction temperature and the gas phase composition was studied. Finally, the optimized system was studied by feeding a synthetic natural gas stream (instead of CH4) in order to approach to a more practical system. The high performance of the system was again verified along with a durability test under polarization conditions in view of the possible practical application of this novel reactor configuration system.