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Preliminary Investigation of Catalytic Decarboxylation of Fatty Acids and Esters

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131596347,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Dongyun Wang, Jon Van Gerpen, Bingjun Brian He
Keywords:   Decarboxylation stearic acid methyl stearate catalyst solvent

Abstract. Research and development of biofuels from renewable resources are now expanding from transportation fuels into other areas such as jet fuels. Oxygen removal, or deoxygenation, to produce jet fuels, is a logical way to overcome the drawback of biofuels’ low energy density.

Generally, the process of deoxygenation includes the following chemical reactions: decarboxylation, decarbonylation and hydrodeoxygenation. This study aims to investigate the effectiveness of catalytic decarboxylation without an external supply of hydrogen. The following heterogeneous catalysts were tested on their efficiencies for decarboxylation under different operating conditions, including reaction time, pressure, temperature, solvent application, stirring rate and catalyst application rate: Pd/C, Pd/Al2O3, Pt/C, Ni/SiO2, Pt/Al2O3 and Raney Nickel.

Pd/C was found to be the most reactive catalyst for the decarboxylation of stearic acid. Although the Pt/C catalyst has a similar selectivity as the Pd/C catalyst, the Pt/C catalyzed reaction is slow. Since it was the most reactive, further studies were conducted using the Pd/C catalyst. It was found that increasing the temperature caused an increase in the conversion rate of the reactant to heptadecane and therefore increased the product yield .The conversion was increased from 54% at 265°C to approximately 98% at 300°C after one hour. In general, the decarboxylation rate of stearic acid increases as the concentration of catalyst in the reactant mixture increases. However, the effect of catalyst concentration levels off when it is 8% or higher. Additionally, as the solvent to reactant mass ratio decreases, the reaction takes longer to complete. The effects of pressure and mixing intensity were found to be negligible.

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