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 nano -particles (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 degrees 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 degrees 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 equi-librium of CO2 methanation process.

Automated summary

The Centre of Hydrogen Energy (CHE) has recently developed novel structures of fibrous mesoporous silica nano-particles (FMSN) and fibrous Mobil composition of matter-41 (FMCM-41), namely CHE-SM and CHE-S41. These structures were used as a support, with 5 wt% Ni as the active metal, for carbon dioxide (CO2) methanation. The results from low angle x-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that Ni/CHE-S41 had a hexagonal structure, while Ni/CHE-SM had a lamellar structure. Ni particles were found to be deposited on the surface of CHE-SM due to its smaller support pore size (4.41 nm) compared to the average Ni particles diameter (5.61 nm), resulting in higher basicity and reducibility. On the other hand, Ni/CHE-S41 exhibited deposition of Ni particles in the pore due to the difference in support pore size (4.89 nm) compared to average Ni particles diameter (4.01 nm). As a result, Ni/CHE-SM achieved a higher CO2 conversion (88.6 %) than Ni/CHE-S41 (82.9%) at 500 degrees C, while both showed 100% selectivity towards methane. Furthermore, Ni/CHE-SM demonstrated excellent resistance to coke formation during a 50 h stability test at 500 degrees C, as evidenced by a lower weight loss of 0.469% in TGA analysis and a lower G:D band ratio of 0.43 in Raman spectroscopy compared to Ni/CHE-S41 (0.596% weight loss and 0.74 G:D band ratio). These properties of Ni/CHE-SM are advantageous in the field of methane production, as coke formation can affect the equilibrium of the CO2 methanation process.