Monolithic Ni5Ga3/SiO2/Al2O3/Al-fiber catalyst for CO2 hydrogenation to methanol at ambient pressure

A series of Ni5Ga3/m-SiO2/Al2O3/Al-fiber (m = 0, 0.5, 1.0, 3.0 and 5.0 wt%) catalysts have been developed for CO2 hydrogenation to methanol at ambient pressure. Microfibrous-structured SiO2/Al2O3/Al-fiber supports are obtained though endogenous growth of free-standing boehmite (AlOOH) nanosheets onto a three-dimensional (3D) network of 60 mu m-Al-fiber thin felt with the aid of steam-only hydrothermal oxidation reaction between Al metal and H2O (2 Al + 4H(2)O -> 2 AlOOH + 3H(2)), followed by calcination and SiO2-modification using silica sol. The bimetallic Ni5Ga3 nanoparticles are then placed onto the pore surface of as-obtained SiO2/Al2O3/Al-fiber support by co-impregnation method using Ni and Ga nitrates as precursors followed by reduction in H-2 at 630 degrees C. The promising Ni5Ga3/1-SiO2/Al2O3/Al-fiber catalyst is capable of converting 2.3% CO2 into CH3OH with a high selectivity of 86.7% as well as 10.3%/3.0% selectivities to CO/CH4 at 210 degrees C, for a feed of CO2/H-2/N-2 (2/6/1, molar ratio). Such microfibrous-structured catalyst design combines the promising catalytic performance of Ni5Ga3 with the enhanced heat transfer and high permeability of the Al2O3/Al-fiber support. The effect of SiO2 loading on the formation of Ni5Ga3 alloy nanoparticles is also discussed.