Journal
ACS CATALYSIS
Volume 9, Issue 9, Pages 8471-8480Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.9b02340
Keywords
propyne semihydrogenation; theoretical calculation; active sites; Pd octahedrons; apexes
Categories
Funding
- National Key R&D Program of China [2016YFE0129600]
- National Natural Science Foundation of China [21673150, 21611540336, 21771134, 91545127, 51802206]
- Natural Science Foundation of Jiangsu Province [BK20180097, BK20180846]
- Thousand Youth Talents Plan
- 111 Project
- Joint International Research Laboratory of Carbon-Based Functional Materials and Devices,
- Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC)
- Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
- SWC for Synchrotron Radiation
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The development of highly selective catalysts has been remarkably relying on the understanding of catalytic active sites. Pd-catalyzed semihydrogenation of propyne has been a focus of research with industrial applications toward the production of polymer-grade propylene. In this work, combining density functional theory (DFT) calculations and experimental observations, we propose that, different from the existing debates where the formation of palladium carbide (Pd-C) species or specific facets of Pd nanoparticles are critical, the apexes of Pd (111) octahedrons are the active sites for highly selective propyne semihydrogenation. The propylene selectivity on Pd octahedrons can be ascribed to site-selective propyne adsorption on the apexes prior to reactions and subsequent difficult to access intermediate states toward overhydrogenation. To reveal the active sites of Pd, propyne semihydrogenation was performed on shaped-Pd nanoparticles with designed exposed facets: e.g., (111) and (100) facets. Of practical importance, the propyne conversion and propylene selectivity exceed similar to 94% and similar to 96% on Pd octahedrons, respectively, at low temperature (35 degrees C) and atmospheric pressure. In addition, more control experiments have been performed to verify the effects of apexes of Pd octahedrons on propylene selectivity. It is shown that the propylene selectivity decreases to similar to 50% when the apexes of Pd octahedrons are gradually removed. The experimental observations have further confirmed that the apexes of Pd octahedrons can be used as the active sites for propyne semihydrogenation, which is in good agreement with the results from theoretical calculations. This work may not only reveal the active sites of Pd nanoparticles for selective semihydrogenation of propyne but also open an avenue for designing highly active and selective catalysts in the chemical industry.
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