Hydrogenation of aromatic hydrocarbons is important in the production of higher-quality and more environmentally-friendly diesel and jet fuels as well as in the production of multiple specialty chemicals. Catalytic activity and selectivity for common hydrogenation catalysts, such as palladium, are dependent on the structure of an aromatic molecule. However, effects of the aromatic hydrocarbon structure on catalytic properties are not well understood. In this work, adsorption on Pd of benzene, toluene and tetralin – aromatic molecules with one benzene ring – was studied at the molecular level using temperature programmed desorption, Raman spectroscopy and density functional theory (DFT) calculations. Pd/SiO<sub>2</sub> catalysts were prepared using an incipient wetness impregnation method and analyzed with scanning electron microscopy. Computational results show that the evaluated aromatics preferentially adsorb at low coverage in the same configuration: through the benzene ring on a bridge 30° Pd surface site, with the plane of the benzene ring being parallel to the surface. The adsorption energy decreases with the increasing size of the molecule due to steric effect of the substituted fragments. Experimental Raman spectra of liquid benzene, toluene and tetralin are assigned based on DFT calculations with vibrational analyses. A Raman spectrum of liquid tetralin is reported for the first time. Furthermore, computational results predict Raman spectra for various adsorption structures on Pd. The obtained molecular-level understanding of adsorption structures will be helpful in catalyst development and optimization of reaction conditions.<br/>

Benzene, toluene and tetralin adsorption on palladium catalystsbenzene, toluene and tetralin adsorption on palladium catalysts

2019 Spring National Meeting

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