(239c) Effect of Palladium Surface Structure On the Hydrodeoxygenation of Organic Acids

Lipid feedstock can be utilized for the production of second-generation biofuels via a catalytic hydrodeoxygenation (HDO) process. The conversion of fatty acids plays an important role in the activity and selectivity of this process. Understanding the HDO reaction mechanism of organic acids on metal surfaces is a prerequisite for the rational design of new HDO catalysts specifically designed for lipid feedstock. In our previous study of the HDO of propionic acid over Pd (111), we found that the dehydrogenation of α-carbon and the C-OH bond dissociation steps are activity descriptors in the HDO of organic acids. However, it is well known that the higher-lying d-states in under-coordinated stepped surfaces lower the C-O and C-C bond dissociation barriers and consequently enhance the reactivity in comparison to flat surfaces.  To investigate the sensitivity of the HDO of organic acids on the Pd surface structure, the reaction mechanism of the HDO of propionic acid has been studied on the Pd(211) model surface and the results are compared to our previous Pd(111) investigation. Periodic density functional theory (DFT) calculations have been carried out to obtain reaction rate parameters which are subsequently used in a microkinetic modeling study. Finally, we performed a sensitivity analysis and computed Campbell’s degree of rate control to identify rate-determining steps.