Heterolytic Splitting of H2 and CH4 on -Alumina as a Structural Probe for Defect Sites
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- 作者：Jé ; rô ; me Joubert ; Alain Salameh ; Vincent Krakoviack ; Franç ; oise Delbecq ; Philippe Sautet ; Christophe Copé ; ret ; Jean Marie Basset
- 刊名：Journal of Physical Chemistry B
- 出版年：2006
- 出版时间：November 30, 2006
- 年：2006
- 卷：110
- 期：47
- 页码：23944 - 23950
- 全文大小：452K
- 年卷期：v.110,no.47(November 30, 2006)
- ISSN：1520-5207
文摘
A combined use of DFT periodic calculations and spectroscopic studies (IR and solid-state NMR) shows thata 
hars/gamma.gif" BORDER=0 >-alumina treated at 500 
C under high vacuum contains surface defects, which are very reactive toward H2or CH4. The reaction of H2 on defect sites occurs at low temperature (ca. 25 C) on two types of Al atomsof low coordination numbers, AlIII or AlIV, to give AlIV-H and AlV-H, respectively. The amount of defectsas titrated by H2 at 25 and 150 C is 0.043 and 0.069 site/nm2, 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 correspondingAlIV-CH3 (0.030 site/nm2). The difference of reactivity of H2 and CH4 is fully consistent with calculations(reaction and activitation energy, hars/Delta.gif" BORDER=0 >E and hars/Delta.gif" BORDER=0 >E
hermod.gif">).
hars/gamma.gif" BORDER=0 >-alumina treated at 500 C under high vacuum contains surface defects, which are very reactive toward H2or CH4. The reaction of H2 on defect sites occurs at low temperature (ca. 25 C) on two types of Al atomsof low coordination numbers, AlIII or AlIV, to give AlIV-H and AlV-H, respectively. The amount of defectsas titrated by H2 at 25 and 150 C is 0.043 and 0.069 site/nm2, 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 correspondingAlIV-CH3 (0.030 site/nm2). The difference of reactivity of H2 and CH4 is fully consistent with calculations(reaction and activitation energy, hars/Delta.gif" BORDER=0 >E and hars/Delta.gif" BORDER=0 >Ehermod.gif">).