Selective hydrogenation of CO2 to ethanol and higher alcohols using Li-supported Rh nanoparticles

One of the greatest and most complicated challenges of the 21st century for preventing even more disastrous effects on the habitability of our planet, is to minimize the increasing CO2 emissions representing the main cause of climate change. The focus of this thesis is the CO2 hydrogenation to higher alcohols. Particular attention is given to finding new catalysts and alternative catalyst synthesis methods that allow a good control over the structure of the catalyst involved in the CO2 hydrogenation reaction. Following both literature studies and previous results obtained by the research group, rhodium (Rh) nanoparticles (NPs) supported on mesosilica have been chosen as metal catalyst. An innovative hybrid method was developed, combining sol immobilization with impregnation. The best catalytic results showed 14.3% CO2 conversion for 1wt%Rh/meso-SiO2@Li10% and 5.8% of methanol selectivity for 1wt%RhFe/meso-SiO2@Li10% (both at 250°C, 80 bar, 20 mL/min of CO2/H2 with 1/3 ratio). Despite the low selectivity towards ethanol production, XPS spectra confirmed the presence of the desired species, and TEM and BET analysis a mesoporous structure with uniform dispersion of Rh NPs throughout all the surface. The efficacy of the synthesis strategy adopted was thus validated.