Theoretical investigation of the adsorption of methanol on the (110) surface of γ -alumina

Vito, David Antonio De; Gilardoni, François; Kiwi‐Minsker, Lioubov; Morgantini, Pierre-Yves; Porchet, S.; Renken, Albert; Weber, Jacques

doi:10.1016/s0166-1280(98)00511-9

Cited by 25 publications

(17 citation statements)

References 32 publications

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“…Apparently, indium species exists in two valence states (oxidized and reduced) and is likely that each indium state affects the surface reactivity in a different way. Indium oxide has a less pronounced Lewis acid character than that of aluminum oxide; see ref and references therein. Therefore, increasing surface Al 2 O 3 amount may be related to the increase of the overall catalyst acidity, and vice versa for indium oxide.…”

Section: Results and Discussionmentioning

confidence: 99%

Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

et al. 2013

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The surface state of the Pt/In 2 O 3 /Al 2 O 3 catalyst coated onto a microchannel stainless steel reactor was investigated under working conditions using synchrotron-based ambient pressure photoelectron (APPES) and X-ray absorption near-edge structure (XANES) spectroscopies, combined with online mass spectrometry. The surface of the fresh catalyst consists of metallic Pt, In 2 O 3 , and Al 2 O 3 . Reduction under 0.2 mbar of H 2 at 250 °C leads to surface enhancement of Pt and partial reduction of In 2 O 3 , while Al 2 O 3 remains unchanged. Reoxidation in O 2 atmosphere stimulates surface segregation of In 2 O 3 over Pt, accompanied by partial oxidation of Pt to PtO x . Based on these results a dynamic, gas-phasedependent surface state is demonstrated. Under methanol steam reforming conditions, the surface state rapidly adapts under the reaction stream regardless of the pretreatment. However, correlation of gas phase with spectroscopic results under working conditions pointed out the beneficial effect of surface indium to reduce the CO selectivity. Finally, evidence of a distorted symmetry of Al sites on Pt/In 2 O 3 /Al 2 O 3 catalyst compared to that of γ-Al 2 O 3 is given. The findings obtained in the present study are of fundamental significance in understanding the relation between the surface state and the catalytic performance of a functional methanol reforming catalyst.

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Section: Results and Discussionmentioning

confidence: 99%

Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

et al. 2013

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“…29,30 Their results showed that both molecular and dissociative H 2 O adsorption are obtained on a-Al 2 O 3 (0001) and that the hydroxylated alumina surface is formed exothermically. Quantum chemical calculations were performed to investigate the interaction between g-Al 2 O 3 and small molecules such as H 2 , 31 H 2 O, [30][31][32][33] H 2 S, 31,33 HCl, 34 CO, 35,36 CH 3 OH, 37 MoS 2 38 and pyridine. 32 To the best of our knowledge, the mechanisms of the H 2 O-g-Al 2 O 3 (110) interactions have not been adequately addressed.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen generation by the reaction of H₂O with Al₂O₃-based materials: a computational analysis

Chen

2015

Phys. Chem. Chem. Phys.

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The mechanisms for H2O adsorption on γ-Al2O3(110) surface were investigated to illustrate the influence of oxide modifiers on the hydrogen generation reaction. Periodic density functional theory (DFT) calculations with the projected augmented wave (PAW) approach were carried out to study the adsorption of H2O, OH, O and H species, as well as the reaction mechanisms of H2O splitting and H2 generation. Their corresponding structures and adsorption energies are also reported. The calculation results show that H2O, OH, O and H are preferably bound at Al(I)-top, Al(III)-bridge, Al(I,II)-bridge and Al(III)-bridge sites with adsorption energies of -0.42, -5.01, -8.70 and -2.38 eV, respectively. The potential energy profiles for water splitting and hydrogen generation on the γ-Al2O3(110) surface are mapped out. We find that hydrogen generation on the surface occurs via two processes, namely, H2O dehydrogenation and direct H2 generation with an overall exothermicity of 2.24 eV. The nonexistence of intrinsic transition-state barriers and the high exothermicity for the reaction of H2O(g) + γ-Al2O3(110) → O(ads)/γ-Al2O3(110) + H2(g) result in rapid H2 generation. The stepwise H2 generation mechanism of adsorption on the γ-Al2O3(110) surface was also demonstrated using first-principles molecular dynamics simulations. In addition, the nature of the interaction between the adsorbate and the surface during the reaction was also analyzed by the local density of states and by Bader charge calculations.

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“…10 DeVore and co-workers used temperature programmed desorption-FTIR to develop schematic structures for how methanol can bond to model surfaces of g-alumina. 11 The experimental studies have been supplemen-ted by theoretical investigations on alumina 12 and comparable substrates. [13][14][15] The interaction of methanol with alumina is also important in the industrial scale manufacture of methyl chloride, where methanol and hydrogen chloride are combined over high surface area alumina catalysts, e.g.…”

Section: Introductionmentioning

confidence: 99%

An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of η-alumina and methanol

McInroy

Lundie

Winfield

et al. 2005

Phys. Chem. Chem. Phys.

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The industrially important interaction of methanol with an eta-alumina catalyst has been investigated by a combination of infrared spectroscopy (diffuse reflectance and transmission) and inelastic neutron scattering (INS) spectroscopy. The infrared and INS spectra together show that chemisorbed methoxy is the only surface species present. Confirmation of the assignments was provided by a periodic DFT calculation of methoxy on eta-alumina (110). The thermal conversion of adsorbed methoxy groups to form dimethylether was also followed by INS, with DFT calculations assisting assignments. An intense feature about 2600 cm(-1) was observed in the diffuse reflectance spectrum. This band is poorly described in the extensive literature on the alumina/methanol adsorption system and its observation raised the possibility of a new surface species existing on this particular catalyst surface. INS measurements established that the 2600 cm(-1) feature could be assigned to a combination band of the methyl rock with the methyl deformation modes. This assignment was reinforced by an analysis of the neutron scattering intensity at a particular energy as a function of momentum transfer, which confirmed this particular adsorbed methoxy feature to arise from a second order transition. Similar behaviour was observed in the model compound Al(OCH3)3. The anomalous infrared intensity of the 2600 cm(-1) peak in the diffuse reflectance spectrum is a consequence of the different absorption coefficients of the C-H stretch and the combination mode. The implications for catalyst studies are discussed.

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Theoretical investigation of the adsorption of methanol on the (110) surface of γ -alumina

Cited by 25 publications

References 32 publications

Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

Hydrogen generation by the reaction of H₂O with Al₂O₃-based materials: a computational analysis

An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of η-alumina and methanol

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Theoretical investigation of the adsorption of methanol on the (110) surface of γ -alumina

Cited by 25 publications

References 32 publications

Methanol Steam Reforming over Indium-Promoted Pt/Al2O3Catalyst: Nature of the Active Surface

Methanol Steam Reforming over Indium-Promoted Pt/Al2O3Catalyst: Nature of the Active Surface

Hydrogen generation by the reaction of H2O with Al2O3-based materials: a computational analysis

An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of η-alumina and methanol

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Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

Methanol Steam Reforming over Indium-Promoted Pt/Al₂O₃Catalyst: Nature of the Active Surface

Hydrogen generation by the reaction of H₂O with Al₂O₃-based materials: a computational analysis