(416b) Decarbonylation and Decarboxylation of Heptanoic Acid Over Supported Pt and Pd Catalysts
Deoxygenation refers to a broad class of chemical reactions involving the removal of oxygen from organic compounds that can be accomplished by dehydration, decarbonylation and decarboxylation. Linear carboxylic acids found in vegetable oils and animal fats can be readily converted to chemicals and fuels by decarbonylation and decarboxylation reactions. Recent work on decarbonylation and decarboxylation of carboxylic acids over transition metal catalysts is often performed in the presence of dihydrogen to inhibit catalyst deactivation, but the reactions are highly selective towards the production of paraffins because of the rapid hydrogenation of alkenes formed in the process. Since terminal alkenes formed by decarbonylation are appealing chemical intermediates in the polymer industry, a selective catalyst for decarbonylation of carboxylic acids that is stable in the absence of external dihydrogen is highly desirable.
In this work, we synthesized supported Pt and Pd nanoparticles for the decarbonylation of heptanoic acid with the goal of forming α-olefins. In particular, Pt and Pd nanoparticles were synthesized on Norit activated carbon by an incipient wetness impregnation method. The catalysts were tested for heptanoic acid conversion in a continuous flow fixed bed reactor operating at 573 K and 37 bar for liquid-phase operation and 1 bar for gas-phase operation. The effects of metal weight loading and conversion on catalyst stability and product selectivity will be discussed. Low conversion experiments in liquid-phase and gas-phase operation suggest that the main reaction path over Pt and Pd/Norit C was decarbonylation; however, decarboxylation products appeared at higher conversions presumably because of secondary side reactions such as water-gas shift (WGS) and hydrogenation. Metal sintering was detected by XRD and TEM.