Application of density functional theory to propylene to propylene oxide catalytic reaction

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2015
Onay, Deniz
Current propylene oxide production highly relies on costly and environmentally disadvantageous processes. Direct propylene epoxidation on heterogeneous surface is desired to replace these processes. With this ultimate goal in mind, propylene epoxidation has been investigated on Cu2O(001) and RuO2(110) surfaces. Different elementary steps of the reaction mechanism that result in propylene oxide formation are analyzed on these catalytic models by using Density Functional Theory (DFT) calculations via Vienna Ab initio Simulation Package (VASP). CI-NEB method is utilized for the activation barrier analysis. Beside propylene oxide, formations of side products, such as allyl radical, acrolein, acetone and propionaldehyde, are also examined in order compare the activity of the surfaces. Two different mechanisms that lead to propylene oxide are distinguished on the surfaces, namely ‘surface intermediate type mechanism’ and ‘direct mechanism’. For both of the mechanisms, Cu2O(001) surface, which is covered with oxygen, is found to be ineffective for formation of propylene oxide. Rather than propylene oxide, allyl radical which finally results in acrolein is favored over this surface. Both type of mechanisms are investigated on two different type of RuO2(110) surfaces, namely ‘RuO2(110) surface’ and ‘RuO2-Oγ surface’, the latter is modeled by the consideration of oxygenated reaction medium. Surface intermediate type mechanism is found to result in a blocking effect for formation of any of the products on RuO2(110) surface. Unlike RuO2(110) surface, both mechanisms are favored for propylene oxide formation on RuO2-Oγ surface as a result of the higher activity of Oγ species which is also found to be the most electrophilic oxygen species in this study.

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Citation Formats
D. Onay, “Application of density functional theory to propylene to propylene oxide catalytic reaction,” M.S. - Master of Science, Middle East Technical University, 2015.