Lamellar-structured fibrous silica as a new engineered catalyst for enhancing CO₂ methanation

Recently, Centre of Hydrogen Energy (CHE) has developed new structures of fibrous mesoporous silica nanoparticles (FMSN) and fibrous Mobil composition of matter-41 (FMCM-41) called CHE-SM and CHE-S41, respectively. Both are used as a support, along with adding 5 wt% Ni as active metal and examined on carbon dioxide (CO₂) methanation. The low angle x-ray diffraction (XRD) and transmission electron microscopy (TEM) results proved that Ni/CHE-S41 possessed a hexagonal structure while Ni/CHE-SM was discovered in a lamellar structure. In addition, the XRD and N₂ adsorption–desorption revealed that Ni particles were deposited on the surface of CHE-SM due to the smaller support pore size (4.41 nm) than the average Ni particles diameter (5.61 nm) resulting in higher basicity and reducibility. Meanwhile, Ni/CHE-S41 revealed deposition of Ni particles in the pore due to difference in support pore size (4.89 nm) compared to average Ni particles diameter (4.01 nm). Consequently, Ni/CHE-SM performed higher CO₂ conversion (88.6 %) than Ni/CHE-S41 (82.9%) at 500 °C, while both achieved 100 % selectivity towards methane. Furthermore, the Ni/CHE-SM displayed excellent resistance towards coke formation during 50 h stability test at 500 °C. It is confirmed as Ni/CHE-SM exhibited a weight loss of 0.469% in TGA analysis and a G:D band ratio of 0.43 in Raman spectroscopy, both of which were lower than the corresponding values of Ni/CHE-S41 (0.596% weight loss and 0.74 G:D band ratio). These properties of Ni/CHE-SM are beneficial in methane production field as coke formation could affect the equilibrium of CO₂ methanation process.