The acidity of surface silanol groups. A theoretical estimate based on ab initio calculations on a model surface

Sauer, Joachim; Hill, Jörg‐Rüdiger

doi:10.1016/0009-2614(94)00002-6

Cited by 68 publications

(26 citation statements)

References 7 publications

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“…It is known through ab initio calculations and experiment that the deprotonation energy for surface bound silanol groups is around 1390 kJ mol −1 . 61 This shows that the silanol group is more acidic than H 2 O, which has a deprotonation energy of approximately 1630 kJ mol −1 in the gas phase. 62 This is also demonstrated by the difference in solution phase pK a values of 7 and 14 for surface silanol groups 63 and H 2 O, 42 respectively.…”

Section: B Adsorption Of C 6 H 6 On Aswmentioning

confidence: 96%

Thermal desorption of C6H6 from surfaces of astrophysical relevance

Thrower

Collings

Rutten

et al. 2009

The Journal of Chemical Physics

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The thermal desorption of C(6)H(6) from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO(2) substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C(6)H(6) on grains surrounded by H(2)O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C(6)H(6) from the amorphous SiO(2) substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C(6)H(6) on the H(2)O surface. The astrophysical implications of these observations are briefly outlined.

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Section: B Adsorption Of C 6 H 6 On Aswmentioning

confidence: 96%

Thermal desorption of C6H6 from surfaces of astrophysical relevance

Thrower

Collings

Rutten

et al. 2009

The Journal of Chemical Physics

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“…The termination of these clusters was achieved by H-Si≡ groups instead of H-O-Si≡ groups, to avoid additional intramolecular hydrogen bonds and unrealistic physico-chemical properties. [33][34][35][36] The [PdO] 2+ species were represented by the structures shown in Figure 1. These models were chosen based on our previous study on models of mesoporous Al-MCM-41 surface sites.…”

Section: Theoretical Modelsmentioning

confidence: 99%

Oxidation of Methane to Methanol over Single Site Palladium Oxide Species on Silica: A Mechanistic view from DFT

et al. 2017

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Abstract:A theoretical analysis was carried out on the mechanism of methane oxidation to methanol occurring on single site palladium oxide species [PdO] 2+ supported on a model of Al-MCM-41 silica. Both 6 and 8-membered ring structures were considered to represent the support.The energy profile for each elementary reaction was determined from density functional theory calculations with the OPBE functional. The calculated overall activation energies are close to the experimental values. Our calculations confirm that spin inversion can play a significant role in decreasing the barrier heights for the pathways. Indeed, in this type of reactions we could show a crossing between singlet and triplet reaction paths. We showed that the mechanism for the C-H bond cleavage and for the formation of methanol has a radical nature. According to our results, the [PdO] 2+ species located on a 8-membered ring of silica is more active than that deposited on a 6-membered ring. The calculated activation energies to cleave the methane C-H bond are 35 and 84 kJ/mol for the radical and ionic pathways, respectively. The activation barrier and the transition state geometry of this H-abstraction step are directly correlated with the optimal angle at which the substrate should approach the [Pd=O] 2+ moiety, with the elongation of the Pd-O oxo bond and finally with the energy of the π* acceptor orbital.2

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“…The structure of the chosen cluster strongly depends on the properties being investigated [32]. In our attempts to investigate the mechanism, it was assumed that the major interactions typically occur between starting materials and propyl-SO 3 H moiety (the functionality of the surface) and the surface did not directly involved in the reaction.…”

Section: <>mentioning

confidence: 99%