Deoxygenation of jatropha oil for the production of hydrogenated biodiesel : effect of active metals

Abstract

Hydrogenated biodiesel is referred to as diesel-like hydrocarbons that do not contain oxygen in their molecules. Its properties are much better than those of typical biodiesel such as higher heating value, higher cetane number, and lower corrosiveness. It can be produced via deoxygenation process. In this work the production of hydrogenated biodiesel from jatropha oil was studied over catalysts containing different active metals. The studied catalysts are Pd/Al₂O₃, Pt/Al₂O₃, Cu/Al₂O₃, NiCu/ Al₂O₃, NiMo/ Al₂O₃, and CoMo/ Al₂O₃. The reactions were carried out in a continuous flow packed-bed reactor at 325°C, 500 psig, H₂/feed molar ratio of 30 by varying liquid hourly space velocities (LHSV) (0.5, 1, 2, 3, and 4 h⁻¹). The results showed that Pt/Al₂O₃ catalyst gave the highest catalytic activity among the others at the same LHSV. The liquid products obtained over these catalysts are hydrocarbons in the range of diesel fuel. The different catalysts give different product distributions. The hydrocarbons obtained over Pd/Al₂O₃, Pt/Al₂O₃, and NiCu/Al₂O₃ catalysts are mainly n-heptadecane (n-C17). In contrast. Cu/Al₂O₃, NiMo/Al₂O₃, and CoMo/Al₂O₃ give n-octadecane (n-C18) as the main product. Moreover, the reaction intermediates which are stearic acid, palmitic acid, hexadecanol, octadecanol, monoglycerides, and fatty esters were also observed. The amount of intermediates increased with increasing LHSV.