Ni/CaO.Ca12Al14O33 Based-Materials for Hydrogen Production by CO2 Sorption Enhanced Steam Methane Reforming

Sorbents with different CaO/Ca12Al14O33 ratios were prepared by microwaveassisted self-combustion. Catalysts were prepared by Ni wet impregnation of sorbents and a catalyst with an optimized composition was also prepared by microwave-assisted self-combustion method. Then, the CO2 sorption capacity and catalytic activity in sorption enhanced steam methane reforming (SE-SMR) for production of hydrogen were evaluated. X-ray diffraction (XRD) analysis of reduced catalysts confirmed Ni, CaO and Ca12Al14O33 phases. Catalysts prepared by wet impregnation favor high surface area, and consequently the CO2 sorption. The CO2 sorption by CaO modifies the equilibrium of the water gas shift reaction (WGS) and consequently the hydrogen production is improved at 650 ºC. The time of breakthrough for H2, CO, CO2, and CH4 depends on both the excess of CaO and operating conditions (H2O/CH4 ratio). Ni-CA75 catalyst obtained by impregnation method with a CaO excess around 75% leads to the optimum activity. It exhibits high sorption capacity and hydrogen selectivity of 100% during 2 h and 16 h for H2O/CH4 ratios of 3 and 1, respectively. Therefore, Ni-CA75 is the most active and stable catalyst during 50 h in CO2 sorption enhanced steam methane reforming, even at an unusually low temperature (650 ºC).

Keywords: CO2 Sorbent, Hydrogen, Microwave-Assisted Self-Combustion, Ni Catalyst, Sorption Capacity, Steam Methane Reforming, Wet Impregnation, Water Gas Shift.