Heterolytic splitting of H2 and CH4 on γ-alumina as a structural probe for defect sites

Jérôme Joubert; Alain Salameh; Vincent Krakoviack; Françoise Delbecq; Philippe Sautet; Christophe Copéret; Jean Marie Basset

doi:10.1021/jp0641841

Heterolytic splitting of H₂ and CH₄ on γ-alumina as a structural probe for defect sites

Jérôme Joubert, Alain Salameh, Vincent Krakoviack, Françoise Delbecq, Philippe Sautet^*, Christophe Copéret, Jean Marie Basset

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

139 Scopus citations

Abstract

A combined use of DFT periodic calculations and spectroscopic studies (IR and solid-state NMR) shows that a γ-alumina treated at 500°C under high vacuum contains surface defects, which are very reactive toward H ₂ or CH₄. The reaction of H₂ on defect sites occurs at low temperature (ca. 25°C) on two types of Al atoms of low coordination numbers, Al_m or Al_IV, to give Al _IV-H and Al_v-H, respectively. The amount of defects as titrated by H₂ at 25 and 150°C is 0.043 and 0.069 site/nm ², respectively, in comparison with 4 OH/nm²). In contrast, CH₄ reacts selectively at 100-150°C on the most reactive Al_III sites to form the corresponding Al_IV- CH₃ (0.030 site/nm²). The difference of reactivity of H₂ and CH₄ is fully consistent with calculations (reaction and activitation energy, ΔE and ΔE^‡).

Original language	English (US)
Pages (from-to)	23944-23950
Number of pages	7
Journal	Journal of Physical Chemistry B
Volume	110
Issue number	47
DOIs	https://doi.org/10.1021/jp0641841
State	Published - Nov 30 2006
Externally published	Yes

ASJC Scopus subject areas

Materials Chemistry
Surfaces, Coatings and Films
Physical and Theoretical Chemistry

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@article{293d63586e55489fabe74287ae074e02,

title = "Heterolytic splitting of H2 and CH4 on γ-alumina as a structural probe for defect sites",

abstract = "A combined use of DFT periodic calculations and spectroscopic studies (IR and solid-state NMR) shows that a γ-alumina treated at 500°C under high vacuum contains surface defects, which are very reactive toward H 2 or CH4. The reaction of H2 on defect sites occurs at low temperature (ca. 25°C) on two types of Al atoms of low coordination numbers, Alm or AlIV, to give Al IV-H and Alv-H, respectively. The amount of defects as titrated by H2 at 25 and 150°C is 0.043 and 0.069 site/nm 2, respectively, in comparison with 4 OH/nm2). In contrast, CH4 reacts selectively at 100-150°C on the most reactive AlIII sites to form the corresponding AlIV- CH3 (0.030 site/nm2). The difference of reactivity of H2 and CH4 is fully consistent with calculations (reaction and activitation energy, ΔE and ΔE‡).",

author = "J{\'e}r{\^o}me Joubert and Alain Salameh and Vincent Krakoviack and Fran{\c c}oise Delbecq and Philippe Sautet and Christophe Cop{\'e}ret and Basset, {Jean Marie}",

year = "2006",

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day = "30",

doi = "10.1021/jp0641841",

language = "English (US)",

volume = "110",

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TY - JOUR

T1 - Heterolytic splitting of H2 and CH4 on γ-alumina as a structural probe for defect sites

AU - Joubert, Jérôme

AU - Salameh, Alain

AU - Krakoviack, Vincent

AU - Delbecq, Françoise

AU - Sautet, Philippe

AU - Copéret, Christophe

AU - Basset, Jean Marie

PY - 2006/11/30

Y1 - 2006/11/30

N2 - A combined use of DFT periodic calculations and spectroscopic studies (IR and solid-state NMR) shows that a γ-alumina treated at 500°C under high vacuum contains surface defects, which are very reactive toward H 2 or CH4. The reaction of H2 on defect sites occurs at low temperature (ca. 25°C) on two types of Al atoms of low coordination numbers, Alm or AlIV, to give Al IV-H and Alv-H, respectively. The amount of defects as titrated by H2 at 25 and 150°C is 0.043 and 0.069 site/nm 2, respectively, in comparison with 4 OH/nm2). In contrast, CH4 reacts selectively at 100-150°C on the most reactive AlIII sites to form the corresponding AlIV- CH3 (0.030 site/nm2). The difference of reactivity of H2 and CH4 is fully consistent with calculations (reaction and activitation energy, ΔE and ΔE‡).

AB - A combined use of DFT periodic calculations and spectroscopic studies (IR and solid-state NMR) shows that a γ-alumina treated at 500°C under high vacuum contains surface defects, which are very reactive toward H 2 or CH4. The reaction of H2 on defect sites occurs at low temperature (ca. 25°C) on two types of Al atoms of low coordination numbers, Alm or AlIV, to give Al IV-H and Alv-H, respectively. The amount of defects as titrated by H2 at 25 and 150°C is 0.043 and 0.069 site/nm 2, respectively, in comparison with 4 OH/nm2). In contrast, CH4 reacts selectively at 100-150°C on the most reactive AlIII sites to form the corresponding AlIV- CH3 (0.030 site/nm2). The difference of reactivity of H2 and CH4 is fully consistent with calculations (reaction and activitation energy, ΔE and ΔE‡).

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AN - SCOPUS:33846033125

SN - 1520-6106

VL - 110

SP - 23944

EP - 23950

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

IS - 47

ER -

Heterolytic splitting of H₂ and CH₄ on γ-alumina as a structural probe for defect sites

Abstract

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