Hydrocarbon Fuels From Gas Phase Decarboxylation of Hydrolyzed Free Fatty Acid

Gas phase decarboxylation of hydrolyzed free fatty acid (FFA) from canola oil has been investigated in two fix-bed reactors by changing reaction parameters such as temperatures, FFA feed rates, and H₂-to-FFA molar ratios. FFA, which contains mostly C₁₈ as well as a few C₁₆, C₂₀, C₂₂, and C₂₄ FFA, was fed into the boiling zone, evaporated, carried by hydrogen flow at the rate of 0.5–20 ml/min, and reacted with the 5% Pd/C catalyst in the reactor. Reactions were conducted atmospherically at 380–450 °C and the products, qualified and quantified through gas chromatography-flame ionization detector (GC-FID), showed mostly n-heptadecane and a few portion of n-C₁₅, n-C₁₉, n-C₂₁, n-C₂₃ as well as some cracking species. Results showed that FFA conversion increased with increasing reaction temperatures but decreased with increasing FFA feed rates and H₂-to-FFA molar ratios. The reaction rates were found to decrease with higher temperature and increase with higher H₂ flow rates. Highly selective heptadecane was achieved by applying higher temperatures and higher H₂-to-FFA molar ratios. From the results, as catalyst loading and FFA feed rate were fixed, an optimal reaction temperature of 415 °C as well as H₂-to-FFA molar ratio of 4.16 were presented. These results provided good basis for studying the kinetics of decarboxylation process.