Insight into exhaust gas-methane reforming over La2O3-modified Ni/Ca-Al for enhanced hydrogen-rich production

Herein, we aimed to enhance the activity and stability of Ni-based catalysts used in exhaust gas -methane reforming process. To achieve this, modifications were made to the Ni/Ca-Al2O3. The influence of La addition and Ni loading on the physicochemical properties of the Ni/Ca-Al2O3 catalyst used in exhaust gas-methane reforming was investigated. The results demonstrated that adding La as a structural promoter improved the grain size and dispersion of Ni on Al2O3. However, increasing the Ni loading beyond 18 wt% had a detrimental effect on these properties. Therefore, it was determined that the optimal catalyst composition was 18 wt% Ni loading with 2 wt% La addition (2La-18Ni/Ca-Al). Furthermore, a 72-hour lifetime test on the 2La-18Ni/Ca-Al catalyst was conducted, which demonstrated its excellent resistance to carbon deposition and stability under the permissible exhaust temperatures. The catalyst's regeneration stability was evaluated in terms of its service life and economy in the REGR system, and it was found that even after six regeneration cycles, 2La-18Ni/Ca-Al maintained high activity. Moreover, the Ni-based catalyst was successfully modified to achieve gas phase composition closer to thermodynamic equilibrium. The complex mechanism of exhaust gas-methane reforming was proposed under different feedstock temperature: methane follows a sequential dehydrogenation path of CH4 -> CH3 -> CH2 -> CH -> C + H-4 on the surface of Ni; during this reforming process, O-2, H2O, and CO2 all serve as oxidants, and the O atoms dissociated from these molecules participate in the oxidation of both CH and C. It was worth noting that CO2 contained in exhaust gas could be efficiently recycled on-board by conducting exhaust gasmethane reforming at feedstock temperatures above 700 degree celsius.