Catalytic hydrogenation of vegetable oils derivatives

During this project the catalytic hydrogenation of a mixture of fatty acids derivatives was performed in two different reactors (discontinuous batch and continuous flow); the attention was pointed out on the type of the catalyst employed, involving a screening among different noble metals and support with optimization of the reaction parameters. Interesting results were obtained in batch reactions with 0.3% wt Pd/C at 4 bar of H2 and 90°C, ensuring full conversion of the starting material and complete selectivity towards the saturated compounds. An insight of the kinetics of the reaction was performed, conducting the reaction for different time (0-6 hours). Also, fundamental parameters such as H2 pressure, stirring rate, temperature, metal type and support were evaluated for determining the most advantageous conditions to guarantee complete starting material conversion and high yields of desired products. The same tests were then performed employing a continuous flow reactor, confirming the high activity of 0.3% wt Pd/C at low contact time of 0.2 min. Despite stunning results were achieved with a single batch (discontinuous) or for low reaction time (1h in continuous), the catalyst performance started to worsen for multiple batch or longer time respectively. Investigations on the cause were executed, excluding immediately metal leaching thanks to ICP-AES analysis. Deactivation was attributable to absorption of reactants on the catalyst surface, which could lead to formation of oligomers. It was found that the deactivation rate, in the continuous reactor, was directly dependent on the hydrogen pressure, the contact time but even more importantly to the composition of the starting material: an increase of poly-unsaturated fatty acids derivatives affected negatively the catalyst stability, causing a faster decline of conversion and higher decrease in selectively. This was associated to a strong adsorption with consequent formation of oligomers, which occupied the active site, worsening the catalyst’s performance.