Deoxygenation of biomass derived oxygenated compounds using metal oxide catalysts

Abstract

Lignocellulosic biomass has emerged as a sustainable carbon source and an alternative to fossil fuels for producing value-added chemicals and fuels. Itaconic acid (IC) obtained from glucose can be a platform chemical for producing industrially potential chemicals such as methacrylic acid (MAA). In this regard, Al2O3 supported alkali (Na and K) and alkaline earth (Mg and Ca) metal-based catalysts were synthesised using the wet impregnation method for the selective decarboxylation of IC to MAA. 5wt% Ca/Al2O3, having higher basic sites, exhibited the best catalytic activity and afforded a maximum yield of 46.7% MAA. newlineLignin pyrolysis to bio-oil can be used as a fuel source but requires to be upgraded via deoxygenation. In connection with this, Ti-Zr and Nb-Zr mixed oxide supported Ni-based catalysts were designed for gas phase hydrodeoxygenation (HDO) of lignin-based compound (anisole) in a fixed bed tubular reactor. Ni/Nb1Zr4 and Ni/Ti1Zr4 showed high selectivity towards deoxygenated products (63 65% benzene). Mono (TiO2, ZrO2) and mixed oxide (TiO2-ZrO2) supports different mol ratios were also prepared by precipitation method followed by Ni doping via wet impregnation. Ni/Ti1Zr1 showed the highest cyclohexane (94%) selectivity under liquid phase anisole HDO. Likewise, niobium oxide (Nb2O5), was also synthesised by various methods (hydrolysis, precipitation, and hydrothermal) for doping Ni. Ni/Nb2O5, synthesised by hydrolysis method, yielded 49-96% cyclohexane from anisole, phenol, catechol, guaiacol, 2,6-dimethoxyphenol, and guaiacyl-glycerol-and#946;-guicyl-ether. Enhanced oxygen vacancy sites played a crucial role in the HDO reaction, paving the way towards synthesising various non-noble metal-based catalysts for upgradation of lignin oil. newline newline