Direct gas-phase epoxidation of propene to propene oxide over a heterogeneous catalyst holds the potential to revolutionize production of one of the world's major commodity chemicals. New research into fundamental aspects of propene chemistry on nanoparticulate catalysts will help guide strategies for materials development. In the current study, Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) have been employed to explore the molecular-level details of propene and propene oxide binding at a Au/TiO2 catalyst. Competitive binding studies for propene and carbon monoxide reveal that propene readily displaces CO from: first, interfacial Au ||TiO2 sites, then low coordinated Au sites at particulate corners and edges, and finally terrace regions of the particles. DFT calculations show that the [Formula presented] bond of propene weakens upon coordination to Au, which suggests that these sites may activate the molecule for epoxidation. Like propene, propene oxide adsorbs on both Au sites and Ti sites. In addition, Ti-OH sites also readily bind the oxide. However, competitive binding experiments show that the propene oxide adsorption is favored relative to propene on all sites, which would likely passivate the catalyst at room temperature.
Bibliographical noteFunding Information:
Our inspiration for this work and collaboration is all due to John T. Yates, Jr. and his significant advancements in this field of study. We thank him for his love of science and his ability to measure and produce clear and detailed studies for future advancements. This material is based upon work supported in part by the U.S. Army Research Laboratory and the U. S. Army Research Office under contract number W911NF-14-1-0159 . We also gratefully thank the XSEDE computing resources from Texas Advanced Computing Center and San Diego Supercomputer Center for all of the DFT calculations. Lastly, we thank ORAU for an ORISE fellowship for Monica McEntee.
- Density functional theory
- Infrared spectroscopy
- Propene oxide