Calorimetric studies of hydrocarbon adsorption on metal films V. Hydrocarbons on platinum

Palfi, S.; Lisowski, Wojciech; Smutek, M.; Černý, S.

doi:10.1016/0021-9517(84)90006-x

Cited by 39 publications

(14 citation statements)

References 33 publications

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“…Indeed, the heat of adsorption (Δ H ads ) measurements showed marked differences across samples. At 298 K, the Δ H ads for C 2 H 2 and C 2 H 4 on Pt comm was 200 kJ mol –1 and 190 kJ mol –1 , respectively, consistent with literature values. ,− The maximum uncertainty in the calorimetry measurements is estimated to be 10 kJ mol –1 through previous experiments with a similar setup . In stark contrast, C 2 H 4 adsorption on the core–shell nanoparticles was much less exothermic, measuring 125 kJ mol –1 for 2 ML Pt/TiWC and below instrumental detection limits (∼20 kJ mol –1 ) for 2 ML Pt/TiWN as would be expected from the differences in amounts of C 2 H 4 adsorption and reactivity trends.…”

Section: Resultssupporting

confidence: 85%

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

et al. 2020

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We demonstrate that atomically thin Pt shells deposited on transition metal carbide or nitride cores induce up to a 4-fold enhancement in C2H4 selectivity during the partial hydrogenation of acetylene compared with commercial carbon-supported Pt (Ptcomm) nanoparticles. While Pt typically catalyzes the complete hydrogenation of alkynes to alkanes, a catalyst comprising a nominal one monolayer (ML) Pt shell on titanium tungsten nitride cores (Pt/TiWN) is capable of net C2H4 generation under industrial front-end reaction conditions featuring a large excess of C2H4 and H2. Microcalorimetry measurements are consistent with a change in the Pt electronic structure that decreases C2H4 binding strength, thus increasing partial hydrogenation selectivity. Density functional theory (DFT) calculations and X-ray absorption near edge structure (XANES) both indicate broadening of the Pt d-band and concomitant down-shifting of the d-band center. The ability to control shell coverage and core composition opens up extensive opportunities to modulate the electronic and catalytic properties of noble metal-based catalysts.

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Section: Resultssupporting

confidence: 85%

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

et al. 2020

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“…0.3 monolayers. Adsorption at room temperature gave an initial heat of 157 kJ/mol, which is in agreement with the value of 160 kJ/mol for the heat of ethylene adsorption on Pt powder 62 and of 150 kJ/mol for 1.2 wt % Pt/SiO 2 7 and for Pt film . The heat of adsorption decreased with coverage up to about 35 μmol/g, after which the heat increased and passed though a maximum with coverage.…”

Section: Resultssupporting

confidence: 85%

Microcalorimetric, Infrared Spectroscopic, and DFT Studies of Ethylene Adsorption on Pt/SiO₂ and Pt−Sn/SiO₂ Catalysts

et al. 1999

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Microcalorimetric and infrared spectroscopic measurements for adsorption of ethylene on Pt/SiO2 and Pt−Sn/SiO2 (5−8 wt % Pt) have been carried out at temperatures from 173 to 300 K. Ethylene adsorption on Pt and Pt−Sn at temperatures lower than 233 K leads to the formation of π-bonded and di-σ-bonded ethylene species. Ethylidyne species begin to form at temperatures higher than 263 K. Formation of ethylidyne species is suppressed by the presence of Sn. The main surface species observed during ethylene adsorption at room temperature are ethylidyne species on Pt/SiO2, di-σ-bonded ethylene on 7Pt/Sn/SiO2, and π-bonded ethylene on 3Pt/Sn/SiO2. The heat of formation of ethylidyne species and coadsorbed atomic hydrogen on Pt was found to be 157 kJ/mol, while the average heat for the formation of π-bonded and di-σ-bonded ethylene species on Pt was 125 kJ/mol. The heats for formation of π-bonded and di-σ-bonded ethylene on Pt−Sn surfaces were found to be between 98 and 106 kJ/mol. Results from quantum chemical calculations employing density functional theory (DFT) for Pt19 and Pt16Sn3 clusters indicate that Sn donates electrons to the 6sp and 5d orbitals of platinum. These calculations show that the bonding between ethylidyne species and 3-fold hollow sites composed of adjacent Pt atoms involves electron donation from ethylidyne into 6sp orbitals of Pt and back-donation of electrons from 5d orbitals of Pt to the ethylidyne species. The higher electron density on the Pt atoms caused by Sn leads to more repulsive interactions for the formation of ethylidyne species than for the formation for π-bonded and di-σ-bonded ethylene species, and the higher occupation of the Pt 5d orbitals in the presence of Sn requires more extensive back-donation of electrons from Pt to ethylidyne species. These electronic effects caused by Sn weaken the bonding of ethylidyne species at neighboring 3-fold hollow sites.

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“…The heat of adsorption of ethylene to form ethylidyne species and surface hydrogen atoms on Pt(111) was reported by King et al to be −174 ±4 kJ/mol, based on calorimetric measurements . Calorimetric measurements on supported Pt samples yielded slightly lower values of −145 to −157 kJ/mol. , Similar values of about −150 kJ/mol were obtained for Pt films . Results from DFT calculations for Pt(111) predict an energy change of −156 kJ/mol for this dissociative adsorption process …”

Section: Introductionsupporting

confidence: 54%

DFT Calculations and Monte Carlo Simulations of the Co-Adsorption of Hydrogen Atoms and Ethylidyne Species on Pt(111)

et al. 2001

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A grandcanonical Monte Carlo (MC) simulation is described for calculating surface coverages of adsorbed hydrogen atoms and ethylidyne species on Pt(111) as a function of temperature and partial pressures of ethane and hydrogen. The MC simulation is based on self-consistent, gradient-corrected density functional theory (DFT) calculations of the energies of adsorption of H atoms and ethylidyne species at various positions on a periodic Pt(111) slab. DFT calculations of lateral interaction energies between pairs of adsorbates at various distances of separation on the Pt(111) slab are reported. The MC simulation results are in agreement with results from microcalorimetric measurements at 300 K and 573−673 K of the heats of hydrogen adsorption versus adsorbate coverage on two silica-supported Pt samples and on Pt powder. The MC simulation results for the coadsorption of H atoms and ethylidyne species on Pt(111) are used to develop analytical expressions that describe the surface coverages by these species over a wide range of temperatures and pressures (i.e., hydrogen pressures from 1 to 101 kPa, ethane pressures from 0.1 to 10 kPa, and temperatures from 550 to 750 K). The application of these results is discussed for modeling the kinetics of ethane hydrogenolysis over Pt catalysts.

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Calorimetric studies of hydrocarbon adsorption on metal films V. Hydrocarbons on platinum

Cited by 39 publications

References 33 publications

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

Microcalorimetric, Infrared Spectroscopic, and DFT Studies of Ethylene Adsorption on Pt/SiO₂ and Pt−Sn/SiO₂ Catalysts

DFT Calculations and Monte Carlo Simulations of the Co-Adsorption of Hydrogen Atoms and Ethylidyne Species on Pt(111)

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Calorimetric studies of hydrocarbon adsorption on metal films V. Hydrocarbons on platinum

Cited by 39 publications

References 33 publications

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

Microcalorimetric, Infrared Spectroscopic, and DFT Studies of Ethylene Adsorption on Pt/SiO2 and Pt−Sn/SiO2 Catalysts

DFT Calculations and Monte Carlo Simulations of the Co-Adsorption of Hydrogen Atoms and Ethylidyne Species on Pt(111)

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Microcalorimetric, Infrared Spectroscopic, and DFT Studies of Ethylene Adsorption on Pt/SiO₂ and Pt−Sn/SiO₂ Catalysts