Tailoring the stability of Ni-Fe/mayenite in methane – Carbon dioxide reforming

Abstract Carbon dioxide dry reforming of methane can convert two greenhouse gases into syngas, and realize their high value utilization. A series of Ni-xFe/mayenite (Ca12Al14O33) catalysts were prepared by co-impregnation method, and were tested for dry reforming of methane at 700 °C, atmospheric pressure and a feeding CH4/CO2 ratio of 1. Effects of metal load, support contents, particle size on DRM activity and stability of Ni-xFe/mayenite were systematically investigated. Evolution of the catalyst micro-structures before and after DRM has been examined by XRD, BET, TEM-EDX and XPS. The 7.5%Ni-0.1Fe/Ca12Al14O33 catalyst achieved a high conversion (90.1% for CO2 and 86% for CH4) approximate to thermodynamic equilibrium, along with a H2/CO ration of 0.94, and could be operated stably for 60 h. With mayenite as support, the activity of Ni-xFe/Ca12Al14O33 catalysts improved greatly as Ni content increased from 5 wt% to 10 wt%, whereas limited promotion of activity was observed when metal load further increased to 20 wt%. Ni/Ca12Al14O33 with high metal load was more prone to carbon disposition, which caused the reactor to be plugged, but 2 wt% doping of Fe then efficiently suppressed coking during DRM. Mayenite as support was supposed to enhance the oxygen species transfer from FeOx to Ni sites and nickel-support interface, so promoted oxidation of carbon species. Resultantly, with the synergistic assistance of mayenite support and Fe promotion, high CH4-CO2 conversion and excellent stability was possible for Ni-xFe/Ca12Al14O33 catalysts.