H-free hydrodeoxygenation of microalgae biomass using Pd-Ni/γ-AlO bimetallic nanocatalyst in the supercritical environment.

Hydrodeoxygenation (HDO) of Chlorella vulgaris bio-oil as a renewable energy source was evaluated in a supercritical fluid mixture as both a hydrogen donor and solvent, with and without the Pd-Ni/γ-Al₂O₃ nanocatalyst. Firstly, RSM was carried out to improve long-chain hydrocarbons (LCHs) production process in a hydrogen-less supercritical n-hexane medium using dry biomass of Chlorella vulgaris. Then, the reaction was run under optimal conditions, which included isopropanol, temperature, feedstock, and reaction time of 10%V/V, 250 °C, 0.1 g, and 20 min, with the Pd-Ni catalyst with different Pd: Ni ratios. FTIR, XRD, BET, and TEM were the methods used to characterize the catalysts. More than 47% of the final product, in the absence of the catalysts, was made up of LCHs (C-C). However, an interesting change in the product types occurred when the catalyst was present. The catalyst, specifically the Pd metal, directed the reaction towards the production of C and C products. Alkyl benzenes and alkyl phenols were among the several products that the catalyst caused to develop, which themselves are introduced as precursors for LCHs production. The catalyst Pd-Ni/γ-AlO with a Pd: Ni ratio of 3:1 had the best production with a yield of 42.3%.