Comparative study of sulfur-free nickel and palladium catalysts in hydrodeoxygenation of different fatty acid feedstocks for production of biofuels

Catalytic hydrodeoxygenation (HDO) of fatty acids has been investigated using different feedstocks for renewable diesel production. Two types of catalysts were studied: sulfur-free nickel supported on H-Y zeolites, γ-Al₂O₃ and SiO₂, and palladium supported on active carbon as a noble metal catalyst. Preliminary HDO experiments were carried out on these catalysts in a semi-batch reactor at 300 °C in H₂ under a total pressure of 30 bar for 6 h with stearic acid as a model for fatty acids. An in-depth comparative study of Ni/H-Y and Pd/C was performed in HDO of fatty acid methyl ester (FAME) obtained from the Chlorella microalga, tall oil fatty acids (TOFA) and animal fat. HDO experiments revealed that Ni/H-Y was a better catalyst for this process providing higher activity for different fatty acids. Ni supported on γ-Al₂O₃ and SiO₂ provided complete conversion upon testing in HDO of stearic acid while total HDO over Pd/C was not reached.