Deoxygenation of beef fat for the production of hydrogenated biodiesel : effect of active metals

Abstract

The production of hydrogenated biodiesel through the catalytic deoxygenation of vegetable oil has been extensively studied; however, the study of animal fats as feedstock is still limited. The objective of this research is to investigate the catalytic deoxygenation of animal fats (beef tallow) to hydrogenated biodiesel over various alumina-supported active metal catalysts, i.e. Ni-based catalysts (Ni, NiMo, NiCu, NiW, NiRu, NiRh, Nilr), Cu-based catalysts (Cu, CuMo, CuCo, CuW, CuZn), Pt, and Pd. All catalysts were prepared by sequential incipient wetness impregnation. The prepared catalysts were tested for their catalytic activity in a continuous flow packed-bed reactor for 12 h at 325°C, 500 psig, LHSV of 1 h⁻¹, and H₂-to-feed molar ratio of 30. The results show that all catalysts gave the products in the diesel specification range. The monometallic Ni/Al₂O₃, Pt/Al₂O₃, Pd/Al₂O₃ catalysts gave high selectivity towards hydrodecarbonylation reaction, which resulted in n-heptadecane (n-C17) and n-pentadecane (n-C15). On the other hand, the Cu-based catalysts gave high selectivity towards hydrodeoxygenation reaction, which resulted in n-octadecane (n-C18) and n-hextadecane (n-C16). The presence of second metals could alter the reaction pathway depending on the reactivity of second metals. In addition, the presence of second metals could reduce the coke formation over Ni-based and Cu-based catalysts.