Modified Nickel-Indium Catalysts for CH3OH Synthesis from CO2/H2

摘要

The overall objective of this research is to convert the increasingly concerning CO2 and renewable H2 to highly demanded methanol (CH 3OH), which creates a win-win scenario for simultaneous climate change prevention and sustainable economic development. Methanol is an important industrial chemical with a wide variety of uses. Industrial methanol synthesis catalysts are typically composed of Cu, Zn, and Al, but the key to the success of this targeted CO2 utilization technology is the development of novel 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. Due to their unique chemical and physical properties, the light rare earth elements were investigated for use as promoters. The catalysts were characterized with various methods including ICP, N 2 physisorption, XRD, SEM, TEM, EELS, TGA, H2 TPR, TPD, DRIFTS, and XPS. The performances of the new catalysts and conventional catalyst were compared under various evaluation temperatures at ambient pressure. It was found that catalysts with Ni/In ratios of 0. --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 MeOH activity of 0.33 mol h-1 mol catalyst metal -1 compared to the benchmark Cu/ZnO/Al2O3 (CZA) catalyst at 0.17. Several NiaInbAl/SiO2 catalysts also showed higher CO2 conversions compared to the CZA catalyst. The addition of lanthanide promoters to NIA catalysts has been shown to improve activity for all promoters except for La and Ce. The lanthanide promoter found to increase methanol synthesis activity the most was Gd which showed a 27% increase over NiInAl/SiO 2 activity. The heaviest lanthanides tested (Sm, Eu, Gd) all had improved activity and selectivity for methanol, and decreased CO production, but also show a slight increase in methane output. The infrared studies using DRIFTS determined that CO2 hydrogenation on NiaInbAl/SiO2 and lanthanide-promoted catalysts proceeds through monodentate carbonate before further conversion to monodentate and bidentate formate. The rare earth promoters were found to decrease the number of weakly basic sites, allowing for improved CO/CO2 interconversion and formation of surface formate species for improved methanol synthesis activity.