Solvent-free catalytic deoxygenation of palm fatty acid distillate over cobalt and manganese supported on activated carbon originating from waste coconut shell

The deoxygenation of palm fatty acid distillate (PFAD) containing very large amounts of free fatty acids was performed over Co and Mn supported on activated carbon (AC) derived from waste coconut shells to produce green diesel. The biomass-derived AC synthesised from waste coconut shell offers a competitive edge from the aspect of production costs. The effects of mixed metal oxide acid-base Co/AC and Mn/AC catalysts were investigated in the deoxygenation of PFAD in a zero-hydrogen environment. It was found that Co/AC catalysts exhibited higher deoxygenation activity, with 46% selectivity towards n-(C-15+C-17) compared to Mn/AC (34%). When varying Co dopant concentration (Co-x/AC; x=5, 10, 15, 20 and 25 wt %), 25 wt % Co achieved the highest hydrocarbon yield (90%) and n-(C-15+C-17) selectivity (72%) in the deoxygenation screening study. The excellent deoxygenation efficacy was attributed to the employment of a catalyst rich in acid-base-sites, which consecutively catalysed the reaction, favouring C-O bond cleavage through a decarboxylation/decarbonylation route.