The effect of co-adsorbates on activity/selectivity in the hydrogenation of aromatic alkynes

Jackson, S. David; Hardy, H. L.; Kelly, Gordon; Shaw, Lindsay Alexander

doi:10.1016/s0167-2991(97)80918-4

Cited by 6 publications

(8 citation statements)

References 9 publications

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“…24 It has also been suggested that the co-adsorbed molecules can act as a hydrogen transfer agent to neighboring molecules, or to the catalyst surface increasing the surface coverage of hydrogen. 25,26 In this study, we found that adsorbing 1-methylpyrrole on the Rh(111) and Pt(111) surfaces prior to pyrrole hydrogenation significantly promotes the reaction rate. Gas chromatography measurements indicate that the production of ring-cracking products that poison the catalyst surface is significantly reduced in the presence of 1-methylpyrrole.…”

Section: Introductionmentioning

confidence: 64%

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Kliewer¹,

Bieri²,

Somorjai³

2008

J. Phys. Chem. C

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Sum-frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to study the adsorption and hydrogenation of pyrrole over both Pt(111) and Rh(111) single-crystal surfaces at Torr pressures (3 Torr pyrrole, 30 Torr H 2 ) to form pyrrolidine and the minor product butylamine. Over Pt(111) at 298 K it was found that pyrrole adsorbs in an upright geometry cleaving the N-H bond to bind through the nitrogen evidenced by SFG data. Over Rh(111) at 298 K pyrrole adsorbs in a tilted geometry relative to the surface through the π-aromatic system. A pyrroline surface reaction intermediate, which was not detected in the gas phase, was seen by SFG during the hydrogenation over both surfaces. Significant enhancement of the reaction rate was achieved over both metal surfaces by adsorbing 1-methylpyrrole before reaction. SFG vibrational spectroscopic results indicate that reaction promotion is achieved by weakening the bonding between the N-containing products and the metal surface because of lateral interactions on the surface between 1-methylpyrrole and the reaction species, reducing the desorption energy of the products. It was found that the ring-opening product butylamine was a reaction poison over both surfaces, but this effect can be minimized by treating the catalyst surfaces with 1-methylpyrrole before reaction. The reaction rate was not enhanced with elevated temperatures, and SFG suggests desorption of pyrrole at elevated temperatures.

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Section: Introductionmentioning

confidence: 64%

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Kliewer¹,

Bieri²,

Somorjai³

2008

J. Phys. Chem. C

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“…To identify primary and secondary reaction products, we studied the progress of hydrogenation of 1-phenyl-1-propyne ( 6 ) at 40 °C under isobaric conditions (20 bar H 2 ) with Cu/SiO 2–700 and Cy 3 P–Cu/SiO 2–700 catalysts using 0.375 and 0.18 mol % Cu active , respectively (Figure , Table S2). Both catalysts show zero-order dependence on alkyne concentration indicating a strong alkyne adsorption onto the Cu surface . The unmodified catalyst Cu/SiO 2–700 is selective to cis -β-methylstyrene ( 6 - Z -2H) until at least 70% conversion (120 min) and produces phenylpropane with 98% selectivity after 240 min.…”

Section: Resultsmentioning

confidence: 99%

“…An additional set of alkynes (13 substrates), including more challenging terminal alkynes, 53 was then submitted to Cu/ SiO 2−700 and in situ prepared Cy 3 P−Cu/SiO 2−700 under the standard reaction conditions and the same total Cu loading (Figure 2, bottom). Whereas hydrogenation of phthalimidyl alkyne 11 proceeds with low conversion and high Z-selectivity, 2-butynyl benzoate 12 shows no conversion.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

“…Both catalysts show zero-order dependence on alkyne concentration indicat- ing a strong alkyne adsorption onto the Cu surface. 53 The unmodified catalyst Cu/SiO 2−700 is selective to cis-β-methylstyrene (6-Z-2H) until at least 70% conversion (120 min) and produces phenylpropane with 98% selectivity after 240 min. This demonstrates that overhydrogenation to alkane is a secondary process, 24 which is also confirmed by an in situ IR spectroscopy (see Supporting Information for details).…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

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Silica-Supported Cu Nanoparticle Catalysts for Alkyne Semihydrogenation: Effect of Ligands on Rates and Selectivity

et al. 2016

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Narrowly dispersed, silica-supported Cu nanoparticles (ca. 2 nm) prepared via surface organometallic chemistry from a mesityl complex [CuMes] are highly active for the hydrogenation of a broad range of alkynes. High-throughput experimentation allows for identifying the optimal ligand and reaction conditions to turn these supported Cu nanoparticles into highly chemo- and stereoselective catalysts for the preparation of Z-olefins (overall, 23 examples). For instance, PCy-modified Cu nanoparticles semihydrogenate 1-phenyl-1-propyne to cis-β-methylstyrene (20 bar H, 40 °C) with turnover number and turnover frequency of ca. 540 and 1.9 min, respectively, and with 94% selectivity at full conversion.

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“…Previous work by Jackson et al has examined alkyne and alkene hydrogenation in the liquid phase using carbon-supported palladium catalysts. 12,13 Addition of modifiers such as benzonitrile was found to have a marked effect on the activity/selectivity characteristics of the systems studied. For example, in the hydrogenation of phenylacetylene, the addition of benzonitrile shifted the main hydrogenated product from being styrene in the absence of the modifier to ethylbenzene when the benzonitrile was present.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Activated Carbon Using X-ray Photoelectron Spectroscopy and Inelastic Neutron Scattering Spectroscopy

et al. 2002

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The surface chemistry of a commercial activated carbon (Sutcliffe DCL 230), which is representative of carbons used as support materials in finely divided metal catalysts, has been characterized by a combination of traditional methods (surface area, porosity, Boehm titration, adsorption studies) supplemented by X-ray photoelectron spectroscopy (XPS) and inelastic neutron scattering (INS) spectroscopy. pH measurements show the carbon to be highly acidic, with Boehm titration and XPS suggesting a high proportion of carboxylic and lactonic surface groups. Adsorption of phenylacetylene and benzonitrile was followed by UV-vis spectroscopy to determine the affinity of the carbon for substituted aromatics. INS was carried out on the as-received material and also after the adsorption of pyridine on the carbon surface, which was used as a probe of surface acidity. Pyridine chemisorption yielded an excellent INS spectrum, which closely matched solid pyridine, indicating a relatively weak interaction between the carbon and the pyridine. The INS spectrum also confirmed that the number of acid sites capable of protonating pyridine was below an upper limit of 5.6 × 10 19 (g of carbon) -1 . Collectively, this work emphasizes the amphoteric nature of the carbon studied, albeit with a strong acid bias, and indicates that bulk acidity is a poor description of the carbon's chemisorption characteristics.

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The effect of co-adsorbates on activity/selectivity in the hydrogenation of aromatic alkynes

Cited by 6 publications

References 9 publications

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Silica-Supported Cu Nanoparticle Catalysts for Alkyne Semihydrogenation: Effect of Ligands on Rates and Selectivity

Characterization of Activated Carbon Using X-ray Photoelectron Spectroscopy and Inelastic Neutron Scattering Spectroscopy

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