On the Mechanism of Catalytic Conversion of Fatty Acids into Hydrocarbons in the Presence of Palladium Catalysts on Alumina

A conversion of stearic acid into hydrocarbons in the presence of palladium on alumina has been studied. It has been shown that heptadecane and carbon monoxide are formed as the main products, diheptadecylketone is formed as a by-product, and the contribution of the decarbonylation reaction increases as compared to decarboxylation in the presence of hydrogen with an increase in its pressure. The formation of heptadecene and formic acid as intermediate products has allowed the conclusion that the cleavage of the carbon-carbon bond in the stearic acid molecule R-COOH takes place in the Pd coordination sphere, resulting in the formation of formic acid ( or its fragment associated with palladium) and the corresponding olefinic product. Depending on the reaction conditions, formic acid and/or its fragment decompose, yielding CO and H2O or CO2 and H-2. The main routes of the reaction have been simulated using quantum-chemical methods, and it has been shown that the reaction rate-limiting stage is the cleavage of C-C bond in the acid molecule.