Hydrogenation of Acetophenone on Pd/Silica−Alumina Catalysts with Tunable Acidity: Mechanistic Insight by In Situ ATR-IR Spectroscopy
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Open Access
Type
ArticleAbstract
Understanding the cooperative action of metal and acid sites of bifunctional catalysts is essential for developing more efficient catalysts for greener chemical processes. We used in situ ATR-IR spectroscopy in tandem with modulation excitation spectroscopy (MES) and phase-sensitive ...
See moreUnderstanding the cooperative action of metal and acid sites of bifunctional catalysts is essential for developing more efficient catalysts for greener chemical processes. We used in situ ATR-IR spectroscopy in tandem with modulation excitation spectroscopy (MES) and phase-sensitive detection (PSD) to examine the functioning of Pd/silica−alumina (Pd/ SA) catalysts with different acidity of the support in the liquid-phase hydrogenation of acetophenone (AP). The spectroscopic studies revealed that AP was adsorbed on the Pd surface in η1 (O) configuration and initially hydrogenated to 1-phenylethanol (PE) on the metallic Pd sites. On the Pd surface, PE was less strongly adsorbed than AP. PE was preferentially adsorbed on the acidic silica−alumina support via the C−OH group and subsequently dehydrated to styrene on the acidic sites. Hydrogen originating from dissociative adsorption on Pd sites is proposed to hydrogenate part of the formed styrene to ethylbenzene (EB). The intermediate styrene had a short lifetime under hydrogenation conditions. Increasing the support acidity by raising the atomic fraction of aluminum (Al × 100%/(Al + Si)) in SA from 0 to 70% promoted the styrene production, which in turn strongly enhanced the EB yield from 17.3% on Pd/silica to 54.3% on Pd/SA-70, respectively
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See moreUnderstanding the cooperative action of metal and acid sites of bifunctional catalysts is essential for developing more efficient catalysts for greener chemical processes. We used in situ ATR-IR spectroscopy in tandem with modulation excitation spectroscopy (MES) and phase-sensitive detection (PSD) to examine the functioning of Pd/silica−alumina (Pd/ SA) catalysts with different acidity of the support in the liquid-phase hydrogenation of acetophenone (AP). The spectroscopic studies revealed that AP was adsorbed on the Pd surface in η1 (O) configuration and initially hydrogenated to 1-phenylethanol (PE) on the metallic Pd sites. On the Pd surface, PE was less strongly adsorbed than AP. PE was preferentially adsorbed on the acidic silica−alumina support via the C−OH group and subsequently dehydrated to styrene on the acidic sites. Hydrogen originating from dissociative adsorption on Pd sites is proposed to hydrogenate part of the formed styrene to ethylbenzene (EB). The intermediate styrene had a short lifetime under hydrogenation conditions. Increasing the support acidity by raising the atomic fraction of aluminum (Al × 100%/(Al + Si)) in SA from 0 to 70% promoted the styrene production, which in turn strongly enhanced the EB yield from 17.3% on Pd/silica to 54.3% on Pd/SA-70, respectively
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Date
2018Source title
ACS CatalysisVolume
8Publisher
American Chemical SocietyFunding information
ARC DP150103842Licence
Copyright All Rights ReservedFaculty/School
Laboratory for Catalysis Engineering, School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, New South Wales 2006, AustraliaInstitute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hönggerberg, HCl, CH-8093 Zurich, Switzerland
Faculty of Science, School of Physics
Department, Discipline or Centre
The University of Sydney Nano Institute, Sydney, New South Wales 2006, AustraliaCitation
Hydrogenation of Acetophenone on Pd/Silica–Alumina Catalysts with Tunable Acidity: Mechanistic Insight by In Situ ATR-IR Spectroscopy, Mengmeng Chen, Nobutaka Maeda, Alfons Baiker, and Jun Huang, ACS Catalysis 2018 8 (7), 6594-6600, DOI: 10.1021/acscatal.8b00169Share