Ni, Zn and Fe hydrotalcite-like catalysts for catalytic biomass compound into green biofuel

Abstract

In this study, the deoxygenation pathway was proposed to eliminate oxygen species from biomass-derived oil, thereby producing a high quality of hydrocarbon chains (green fuel). The catalytic deoxygenation reaction of bio-oil model compound (oleic acid) successfully produced green gasoline (C8-C12) and diesel (C13-C20) via activated hydrotalcite-derived catalysts (i.e. CMgAl, CFeAl, CZnAl and CNiAl). The reaction was performed under inert N2 condition at 300 °C for 3 h, and the liquid products were analysed by GC-MS and GC-FID analyses to determine the hydrocarbon yield and product selectivity. The activity of the catalysts towards the deoxygenation reaction presented the following increasing order: CNiAl > CMgAl > CZnAl > CFeAl. CNiAl produced a hydrocarbon yield of up to 89 %. CNiAl demonstrated the highest selectivity with 83 % diesel production, whereas CMgAl showed the highest gasoline selectivity with 30 %. These results indicated that catalysts with a high acidic profile facilitate C-O cleavage via deoxygenation, producing hydrocarbons (mainly diesel-range hydrocarbons). Meanwhile, highly basic catalysts exhibit significant selectivity towards gasoline-range hydrocarbons via cracking and lead to the occurrence of C-C cleavage. The large surface area of CNiAl (117 m2 g-1) offered high approachability of the reactant with the catalyst's active sites, thereby promoting high hydrocarbon yield. Consequently, the hydrocarbon yield and selectivity of the deoxygenation products were predominantly influenced by the acid-base properties and structural behaviour (porosity and surface area) of the catalyst.