Mechanism and Reaction Kinetics for Hydrotreatment of PALM OIL for Greendiesel Production

MECHANISM AND KINETICS REACTION HYDROTREATMENT OF PALM OIL FOR GREENDIESEL PRODUCTION

J.F. Vélez¹, K. Sakashita^{1, 2}, S. Asaoka^{1, 3}, A. Ishihara^{1, 4}, D. López⁵, G. Hincapié⁵, J.D. Tapia⁵, A. Molina^1*

¹Universidad Nacional de Colombia-Sede Medellín, Facultad de Minas, Bioprocesos y Flujos reactivos

²Office of Ks Processtech, 9-41-2101, Shinonome 1-chome, Kouto-ku, Tokyo, 135-0062, Japan

³Office Asaoka, 1-23-1, Konandai, Konan-ku, Yokohama, 234-0054, Japan

⁴ Division of Chemistry for Materials, Graduate School of Engineering, Mie University, Mie Pref., Japan

⁵Química de Recursos Energéticos y Medio Ambiente, Instituto de Química, Universidad de Antioquia, Medellín, Colombia

^*Corresponding author: amolinao@unal.edu.co

Experiments for the hydrotreatment of Refined, Bleached and Deodorized Palm Oil (RBDPO) were carried out in a batch reactor at temperatures varying from 335°C to 365°C and pressures in the range of 30 bar to 60 bar. Hydrotreatment transforms vegetable oils, in this case RBDPO, into a zero-sulfur liquid with properties that resemble those of diesel fuel. In a hydrotreatment reactor, high-pressure addition of hydrogen reduces the size of the triglycerides molecules through deoxy and decarbonate hydrocracking. The experiments to determine the HVO kinetics involved a commercial catalyst. The catalyst presulfurization for activation and stabilization was carried out ex situ in a continuous fixed bed reactor. DMDS was entrained by a nitrogen flow at 400°C to guarantee, due to the decomposition of DMDS, that the catalyst was exposed to H₂S for 9 hours. The activated catalyst was then used in a batch reactor to carry out the hydrotreatment reaction. The liquid products formed through the reaction (mainly fatty acids and hydrocarbons) were analyzed by means of a GC-MS and the gaseous products were characterized with a micro GC. The sample of RBDPO was obtained from a local palm oil company and was mainly composed of oleic (38.8 %w), palmitic (34.6 %w), linoleic (13.1 %w) and stearic (8.1 %w) triglycerides. The analysis of the products showed the presence of hydrocarbons varying from 13 to 20 carbon atom; palmitic, oleic and steric acids and di and monoglycerides. Conversion of the RBDPO was higher than 50% for all the experiments. A mechanism that considers the conversion of triglycerides to mono-glycerides and carboxylic acids and the subsequent hydrodeoxygenated to form hydrocarbons was proposed, as well as kinetic expressions for the reactions in the mechanism following a constrained optimization procedure.