Low-Pressure Hydrogenation of CO2 to CH3OH Using Ni-In-Al/SiO2 Catalyst Synthesized via a Phyllosilicate Precursor

The overall objective of this research is to convert the increasingly concerning CO2 and renewable H-2 to highly demanded methanol (CH3OH), which creates a win-win scenario for simultaneous climate change prevention and sustainable economic development. The key to the success of this targeted CO2 utilization technology is the development of low-pressure methanol synthesis catalysts (NiaInbAl/SiO2; a = 0-8.3, b = 0-9.1) by means of a phyllosilicate precursor, allowing for formation of well-dispersed metallic particles with an average diameter of 2.5-3.5 nm. The catalysts were characterized with various methods including ICP-OES, N-2 physisorption, XRD, SEM, TEM, TGA, H-2 TPR, DRIFTS, and XPS. The performances of the NiaInbAl/SiO2 catalysts and conventional catalyst were compared under various evaluation temperatures at ambient pressure. It was found that catalysts with Ni/In ratios of 0.4-0.7 showed the highest activity. Ni3.5In5.3Al/SiO2 (NIA-0.7) with 15% metal loading was the best among the tested NiaInbAl/SiO2 catalysts with an activity of 0.33 mol h(-1) (mol catalyst metal)(-1) in comparison to the benchmark Cu/ZnO/Al2O3 (CZA) catalyst at 0.17. Several NiaInbAl/SiO2 catalysts also showed similar CO2 conversions in comparison to the CZA catalyst. Infrared studies using DRIFTS determined that CO2 hydrogenation on NiaInbAl/SiO2 catalysts proceeds through monodentate carbonate before further conversion to monodentate and bidentate formate. With a feed of CO/H-2 instead of CO2/H-2 the primary hydrocarbon product changes from methanol to propane, accompanied by a lack of formate and monodentate carbonate IR signals.