Facile one-pot solvothermal synthesis of enlarged mesoporous nickel phyllosilicate spherical catalyst for CO₂ methanation

Nickel and nickel-based silica materials are widely known as CO₂ methanation catalysts. However, current nickel-based SiO₂ catalysts face significant challenges in obtaining highly dispersed Ni species that remain stable and active at high temperatures. Specifically, catalyst deactivation is a problem due to the sintering of metallic Ni species on the inert SiO₂ support. Therefore, obtaining thermally stable nickel phases or ensuring high activity at relatively low temperatures is important for superior CO₂ methanation catalytic performance. Based on these research objectives, in this study, we demonstrated that the use of 1,3,5-trimethylbenzene (TMB) as a pore extender in the preparation of stable nickel phyllosilicate (Ni-PS) particles by a sol-gel method leads to the generation of larger mesopores (i.e., surface areas in the range of 442–527 m²/g) with radially open pores. To determine the optimal point of tuning the structure-directing agent hexadecyltrimethylammonium bromide (CTAB) by introducing hydrophobic TMB, X-ray diffraction (XRD) and H₂-TPR analyses were performed to confirm the Ni phases. It was confirmed, including TEM and BET analysis, that the introduction of suitable amounts of TMB (e.g. w_TMB/CTAB = 0.67) provides porosity suitable for CO₂ methanation. The mesoporous Ni-phyllosilicate sample prepared with TMB offer advantages in low-temperature activity and catalyst stability, as confirmed by catalytic activity and recycle tests. The improvement of catalytic performance is significant regarding how well the reactants can contact the active sites inside the heterogeneous solid phase. Therefore, the results of this study provide appropriate directions for the structural design of catalyst materials to improve the performance of heterogeneous solid catalysts in gas phase reactions.