CO2 hydrogenation on Ru/Ce based catalysts dispersed on highly ordered micro-channelled 3YSZ monoliths fabricated by freeze-casting

Abstract

The activity of Ru–Ce/3 mol% Y2O3 doped ZrO2 (3YSZ) catalysts was studied for the CO2 hydrogenation to form CH4 using catalyst-loaded freeze-cast ceramic monolith as possible substitute to conventional support fixed bed catalysts. Two set of three catalysts were elaborated by varying the Ru loading at 2.5, 5 and 7.5 wt% and by using as support (i) 3YSZ powder and (ii) 3YSZ hierarchically ordered and highly porous freeze-cast monolith. Freeze-cast monoliths present an interesting feature sought for catalytic devices, i.e., large and organized porosity boosting gas transport and minimizing pressure loss through it. The catalytic results reveal the adequate catalytic activity of both catalyst configurations and detail the beneficial effect of a monolith as support on CH4 selectivity and CO production. As expected thermodynamically, an increase in the H2 content in the reactor feed shifts the intermediate Reverse Water Gas Shift (RWGS) reaction to the equilibrium and thus improves CH4 yield. This improvement can be explained by the difference of packing between both configuration and at a similar GHSV, the monolith favors the RWGS reaction further in the monolith length which apparently does not occur in the same proportion in the conventional fixed-bed. Finally a study of the pressure drop through all the catalysts did not reveal any significant increase of pressure due to carbon deposition or high inlet flow.