Amorphous silica alumina supported nickel sulfide catalysts for tunable hydrocracking of crude palm oil to biofuel

The development of efficient catalysts for hydrocracking of crude palm oil (CPO) remains important for improving the production of renewable hydrocarbon fuels. This study investigates the hydrocracking of CPO over amorphous potassium hydrogen phthalate (KHP)‒templated Si/Al catalysts modified with NiO and NiS, and proposes structure‒activity relationships supported by detailed physicochemical characterization and response surface methodology (RSM). Nickel impregnation and sulfidation form well dispersed NiO and NiS domains without disrupting the mesoporous Si/Al framework. Acidity analysis reveals that all catalysts lacked medium-strength acid sites, and sulfidation generates a surface dominated by weak acid sites while retaining a small fraction of strong acid sites. Catalytic screening indicates that KHP‒Si/Al‒NiS exhibits the highest conversion (78.58 %) and the most favorable biofuel distribution, producing 44.14 % C₅‒C₉, 30.44 % C₁₀‒C₁₄, and the lowest C₂₂₊ fraction (9.26 %), demonstrating the potential of the KHP‒Si/Al‒NiS catalyst as an alternative sulfided catalyst system for hydrocracking by combining the catalytic functionality of NiS with the structural stability of the amorphous mesoporous Si/Al support. RSM‒CCD was then applied to optimize reaction conditions over KHP‒Si/Al‒NiS, revealing temperature and feed flow rate as the dominant variables controlling both conversion and biogasoline fraction. The optimized reaction conditions (677 °C, 11.12 g/min feed flow rate, and 4 g of catalyst) afford 84.30 % conversion and 44.55 % biogasoline fraction. The observed acidity distribution suggests that the predominance of weak acid sites after sulfidation, together with the remaining strong acid sites, contributes to the formation of C₅‒C₁₄ hydrocarbons while limiting excessive over-cracking, demonstrating the potential of the catalyst system for tunable biofuel production through process optimization of the hydrocracking operating conditions.