SBA-15 and carbon supported nickel, heteropoly acid catalysts for the hydrodeoxygenation of lignin derived trans-anethole to sustainable aviation fuel

Abstract

Catalyst is the key for the hydrodeoxygenation (HDO) of lignin derivatives to produce alkyl aromatics and alkyl cycloalkanes, key components of 100% sustainable aviation fuels (SAF). Mono and bi-functional catalysts of nickel (Ni) and heterophosphotungstic acid (HPW) supported on SBA-15 and carbons were prepared, characterized and evaluated for the HDO of lignin derived trans-anethole. The SBA-15 structure was intact but its surface area and pore volume decreased with the incorporation of Ni and HPW. UV–Visible DRS and XPS confirmed the presence of Nio and Ni2+ in the bi-functional catalysts. FTIR spectra of pyridine adsorbed Ni(10)-HPW(10)/SBA-15 catalyst showed the presence of both Brønsted and Lewis acid (Ni2+) sites and hence its acidity was higher than mono functional HPW/SBA-15 catalyst as indicated by the ammonia TPD studies. The synergy between them might be the possible reason for the higher and stable conversion, higher HDO selectivity, and more importantly higher selectivity for propyl benzene and propyl cyclohexane over bi-functional catalysts. Among the bi-functional catalysts, the highest conversion and HDO selectivity were observed over Ni(10)-HPW(10)/SBA-15. Its highest selectivity for propyl cyclohexane was due to its mean Ni particle size of 31.02 nm, large enough for the co-adsorption of hydrogen and benzene ring of propyl benzene, thus led to its saturation. Optimum temperature for the maximum conversion and HDO selectivity was found to be 400 °C for the bi-functional catalysts. Comparing carbon and SBA-15 supported Ni-HPW catalysts, later have shown higher HDO selectivity owing to strong metal-support interaction.