Production of Green Diesel Via Decarboxylation of Free Fatty Acids

Wednesday, November 10, 2010: 4:30 PM
Grand Ballroom H (Marriott Downtown)
Elvan Sari, Craig DiMaggio, Manhoe Kim, Shuli Yan, Steven O. Salley and K. Y. Simon Ng, Chemical Engineering and Materials Science, Wayne State University, Detroit, MI

Green diesel is a next generation transportation fuel which emerged due to the need of renewable fuel replacement that is compatible with existing automotive technology,has high cetane number, low NOx emissions, and high heating value. Furthermore, the outstanding energy density of hydrocarbons as a fuel makes them a powerful transportation fuel option. It can be produced via a catalytic reaction involving hydroprocessing or/ and decarboxylation/ decarbonylation of the triglyceride . Advances in the production of green diesel have been scarce due to the lack of process knowledge. The literature indicates that decarboxylation of stearic acid with carbon supported catalysts is generally leading to higher raction rates especially with 5% Pd/C which showed the best performance in a semibatch reactor under helium atmosphere at 300 0C and 6 bar. However, it was concluded that catalyst deactivation has been inferred to occur via coking and/or CO poisoning. In this work decarboxylation of stearic and oleic in solvent was investigated under different atmosphere such as He, H2 and He-H2 mixture using carbon based catalyst. Batch experiments were conducted using a 500-mL stirred Parr high pressure reactor and 5% palladium on activated carbon support catalyst (Aldrich). Reaction conditions were 3000C and 220 psi. The liquid product was analyzed by gas chromatography using a Perkin Elmer Arnel Clarus 500 instrument equipped with a MXT-1 capillary column (60 m x 0.28 mm x 1.0 mm). Results show that saturated free fatty acids (FFAs) such as stearic acid can be decarboxylated to the linear alkanes having one carbon number less than the corresponding FFA under inert gas atmosphere with 99.9 % conversion. However, unsaturated FFAs such as oleic need to be hydrogenated before or during decarboxylation in the presence of hydrogen. The significance of this study is to show a better understanding of the processing conditions required, including catalyst support structure, optimization of the reaction conditions and especially the roles that hydrotreating of the catalyst plays, in order to further develop the current green diesel process.

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