Ni-CeO2/TS-1 catalyze methane dry reforming: Improving catalytic performance and stability by modulating the amount and strength of Ni-O-X species

In this study, a series of Ni-CeO 2 /TS-1 (Titanium Silicalite-1) catalysts were synthesized for dry reforming of methane (DRM). Among them, 5Ni-10CeO 2 /TS-1 exhibited the highest catalytic performance with 89 % CH 4 and 93 % CO 2 conversions, 4.81 mol CH4 ·g Ni -1 ·h −1 and 4.99 mol CO2 ·g Ni -1 ·h −1 specific activities, 95.5 % H 2 /CO ratio after 50 h, accompanied by the good stability with 2.9 % CH 4 and 2.3 % CO 2 activity loss within 100 h. Combined with various characterizations, the structure–function relationship was also investigated. For the physical and morphological analysis, it was indicated that the appropriate CeO 2 content could effectively diminish, disperse the Ni nanoparticles, and maintain MFI backbone structure. For the electronic structure, the introduced CeO 2 could improve the amount and strength of the surface Ni-O-X (Ti or Ce) species by changing the interaction among Ni nanoparticles, TS-1 and CeO 2 . It led to more Ni nanoparticles in stronger electron-deficient state, as well as more medium-strength basic sites, favoring for the activation of CH 4 and CO 2 . However, Ni nanoparticles would be covered when excessive CeO 2 was introduced, preventing the exposure of the active sites. Therefore, only the suitable CeO 2 in the catalysts could significantly improve catalytic performance for DRM with long-term stability. Furthermore, the good anti-sintering and anti-coking properties of 5Ni-10CeO 2 /TS-1 were mainly dependent on the optimal amount of surface Ni-O-X species with high strength. In-situ DRIFTS (diffuse reflectance infrared spectroscopy) analysis demonstrated that the introduced CeO 2 could help catalyst favor for activating CH 4 and CO 2 molecules, and inhibiting the CH 4 overcracking and carbon accumulation, confirmed by the long-term measurement and structure analysis of spent catalysts.