Sandwich Ni-phyllosilicate@doped-ceria for moderate-temperature chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) enables the highly selective oxidation of CH4 and reduction of CO2. We designed sandwich and core-shell structured 5% Ni-SiO2@Ce0.8M0.2O2-delta (M = Fe, Co, Ni) catalysts for moderate-temperature CL-DRM. Highly dispersed nano Ni particles are anchored on the surface of SiO2 spheres, and then transition metal oxide-doped CeO2 is dispersed on the inner core to form a shell layer serving as the oxygen storage role. This trilayer structure provides abundant CeO2-Ni interfaces and catalytic sites. Doping of transition metal oxides helps to activate methane for synthesis gas generation at lower temperatures. In the chemical looping cycle, the available OSC (oxygen storage capacity) was enhanced by the introduction of transition metals into ceria and follows the order of Fe-doped (2.92 mmol g(-1)) > Ni-doped (1.69 mmol g(-1)) > Co-doped (0.86 mmol g(-1)) > undoped (0.58 mmol g(-1)) catalysts. The catalyst exhibits high coke resistance and redox reactivity in successive CL-DRM redox cycles at 620 degrees C. In situ Drifts and Raman of CH4/CO2 temperature programmed desorption over recycled/pre-reduced catalysts show that methane is activated into CHx over highly dispersed nickel nanoparticles at 400 degrees C and then converted into H-2 and CO by lattice oxygen. Then, oxygen vacancies are refilled, reduced species (Fe-0 and Fe2+) are re-oxidized using CO2 to produce CO, and deposited carbon from CH4 POx is also removed via CO2 gasification.