(727g) Surface Studies of Functional Alcohol Reactions on Oxygen-Precovered Pt

Oxidation of multifunctional oxygenates is of interest for the production of high-value chemicals, but the understanding of the mechanism on Pt catalysts is lacking. Studies on Pd(111) has shown coverage dependence selectivity for oxidation reactions as well. It has been shown that high coverages of furfuryl alcohol on oxygen-precovered Pd(111) produced high value, higher mass products of 2(5H)-furanone and maleic anhydride¹. Unfortunately, Pd(111) is not a completely selective metal for oxidation, however other studies suggest that Pt may be higher performing due to its lower d-band center and weaker binding to adsorbates². In designing effective and efficient catalysts for oxidation, both Pt and Pd must be considered due to their ability to activate H₂, which is necessary in these reactions. It is unknown if Pt and Pd catalyze the reaction of these oxygenates in the same way. Surface science techniques on oxygen-precovered single crystals combined with density functional theory (DFT) calculations can provide a fundamental understanding of the decomposition and oxidation mechanisms.

Our recent studies have found that the presence of oxygen on the Pt(111) surface significantly altered the reactions of furan and furfuryl alcohol in comparison to the clean surface. Furan was found to be active on the oxygen-precovered surface, different than its molecular desorption on clean Pt(111), and incorporated surface O to form H₂O, CO, and CO₂. HREEL spectra and DFT calculations indicated that furan formed a furanone intermediate via a furyl-type intermediate. For furfuryl alcohol, the same products were formed as on clean Pt(111), but maleic anhydride was also produced as a minor product. HREELS and DFT calculations suggested that oxidation proceeded through dehydrogenation at the alcohol and methylene groups and subsequent oxidation to produce a carboxylate intermediate. The carboxylate intermediate underwent decarboxylation to form CO₂ and surface furyl intermediates, which then underwent oxidation to produce furanone and maleic anhydride intermediates.

(1) Williams, R. M.; Pang, S. H.; Medlin, J. W. Ring-Opening and Oxidation Pathways of Furanic Oxygenates on Oxygen-Precovered Pd(111). J. Phys. Chem. C 2014, 118 (111), 27933–27943. https://doi.org/10.1021/jp509284d.

(2) Bhogeswararao, S.; Srinivas, D. Catalytic Conversion of Furfural to Industrial Chemicals over Supported Pt and Pd Catalysts. J. Catal. 2015, 327, 65–77. https://doi.org/10.1016/j.jcat.2015.04.018.