Nickel nano-particles encapsulated inside zeolite crystal for active and stable CO2 methanation

Methane synthesis derived from CO 2 hydrogenation has attracted great attention in terms of CO 2 recycling while suffering from the loss and sintering of active nickel species. Hence, we synthesized the Ni@Beta (Si/Al = 40) catalyst with a specific encapsulated structure by a simple hydrothermal synthesis using conventional Ni/SiO 2 as a unique silicon source. Compared to the conventional Ni/SiO 2 and Ni/Al 2 O 3 , the Ni@Silicalite-1 and Ni@Beta with encapsulated structures showed better stability. In addition, the Ni@Beta simultaneously exhibited the highest CO 2 conversion (74.2 %) and methane selectivity (93.5 %). All obtained catalysts were characterized by BET, ICP- OES, XRD, SEM-EDS, HRTEM, H 2 -TPR, CO 2 -TPD, in situ XPS, in situ DRIFTS, and NAP-XPS. Compared with the Ni@Silicalite-1 (Al-free zeolite), the aluminum-containing zeolite frameworks of the Ni@Beta got more electrons from the nickel active phases, so the metal-support interaction on the Ni@Beta was stronger, which was favorable for the stability of the Ni 0 phase. In addition, the Al-containing zeolite frameworks of the Ni@Beta inhibited the formation of volatile metal–molecule intermediates (gaseous Ni(CO) x ), which prevented serious sintering and loss of the nickel species. The in situ DRIFTS and NAP-XPS results not only successfully unveiled that the main reaction pathway was a formate route, but also showed that the Ni@Beta had the strongest capacity to adsorb and convert CO 2 , so it had the highest methanation activity.