Catalytic conversion of biomass- and petrochemical-derived model compounds over acidic catalysts

Abstract

Silica-aluminas (SA) as solid acids are widely used in the chemical, food, pharmaceutical and petrochemical and bio-refining industries. Their acidic properties depend on their local structure. For the first time, the presence of large amount of surface available AlV species on amorphous SA (ASA) was revealed by 27Al MQMAS NMR spectroscopy in this thesis. These AlV species can enhance the strength of neighboring SiOH groups evidenced by 1H-27Al D-HETCOR. Indeed, significantly enhancing the acidity of ASA at the same Al loading was achieved via increasing AlV concentration by applying higher combustion enthalpy solvent. In H/D exchanged with benzene-d6, ASA exhibited 4 times lower activation energy compared to zeolite H-ZSM-5, which was due to the assistance of AlV species. In the conversion of phenylglyoxal to ethyl mandelate, the performance of ASA correlated well with the enhanced Brønsted acidity, confirmed by using silica-zirconia catalyst. At the same conditions, ASA obtained a 10 times higher TOF than dealuminated zeolite HY. This was attributed to the free diffusion of molecules on ASA surface, confirmed by using [Al]MCM-41. Selective dehydration of glycerol on solid acids is important for the production of the value-added acrolein for sustainable bio-refinery. Most efforts focus on developing strong BAS to improve the acrolein production, since LAS produce by-product acetal. With Al-exchange zeolite H-ZSM-5, the significant increase of the acrolein yield was achieved via the cooperative dehydration between the BAS and LAS. In chemoselective hydrogenation of acetophenone, the selectivity was influenced by electronic properties of noble metal, indicated by FTIR investigation. Solid-state NMR spectroscopy studies revealed electronic properties depends on the strength of BAS covered by metal nanoparticles. Increasing the number of uncovered BAS on the supports can improve the performance of supported metal catalyst with similar product selectivity.