Kinetic Modeling of Spillover and Temperature-Programmed Oxidation of Oxy-Carbon Surface Species on Pt/Al<sub>2</sub>O<sub>3</sub> Casey P. O’Brien Ivan C. Lee 10.1021/acs.jpcc.7b03858.s001 https://acs.figshare.com/articles/journal_contribution/Kinetic_Modeling_of_Spillover_and_Temperature-Programmed_Oxidation_of_Oxy-Carbon_Surface_Species_on_Pt_Al_sub_2_sub_O_sub_3_sub_/5035886 During propane oxidation over Pt/Al<sub>2</sub>O<sub>3</sub> in the 200–300 °C temperature range, many different oxygenated carbonaceous (oxy-carbon) surface species spillover from the platinum nanoparticles and grow on the Al<sub>2</sub>O<sub>3</sub> support. The rate of oxy-carbon species growth on the Pt/Al<sub>2</sub>O<sub>3</sub> surface is consistent with a diffusion-limited process where the rate of oxy-carbon species diffusion on the Al<sub>2</sub>O<sub>3</sub> support is the rate-determining step. A model based on Fick’s second law for two-dimensional radial diffusion is used to analyze the kinetics of oxy-carbon species spillover on the Al<sub>2</sub>O<sub>3</sub> support. An Arrhenius expression describing the rate of oxy-carbon species diffusion on the Al<sub>2</sub>O<sub>3</sub> support, which has a pre-exponential factor of 7.9 × 10<sup>–14</sup> cm<sup>2</sup>/s and an activation barrier of 24 kJ/mol, was extracted from the kinetic analysis. Following propane oxidation, the oxy-carbon surface species were completely oxidized to CO<sub>2</sub> during temperature-programmed oxidation (TPO). During TPO of the oxy-carbon species, diffusion of the oxy-carbon species on the Al<sub>2</sub>O<sub>3</sub> support is relatively fast, and a surface reaction on the platinum nanoparticles is the rate-determining step. TPO of oxy-carbon surface species was simulated using surface reaction rate expressions with three different reaction orders with respect to the surface carbon concentration (first-order, second-order, and power-law). The kinetics of TPO of the oxy-carbon surface species is most accurately represented by second-order kinetic rate expressions with activation barriers of 147 kJ/mol for oxidation of acetate species and 112 kJ/mol for oxidation of higher reactivity enolate, aliphatic ester, and acetone species. Formation of platinum oxides during propane oxidation increase the activity of the catalyst for TPO of the oxy-carbon species. This work reveals quantitative mechanistic insights into both the carbon growth and burnoff processes, which is important for designing efficient hydrocarbon conversion processes. 2017-05-10 00:00:00 oxy-carbon surface species oxy-carbon species diffusion oxy-carbon species oxy-carbon species growth Al 2 O 3 support oxy-carbon species spillover propane oxidation increase hydrocarbon conversion processes rate-determining step surface carbon concentration CO Oxy-Carbon Surface Species propane oxidation surface reaction rate expressions TPO surface species spillover platinum nanoparticles