Study of adsorption and reactions of methyl iodide on TiO2

C. Su; J. C. Yeh; C. C. Chen; J. C. Lin; J. L. Lin

doi:10.1006/jcat.2000.2909

Study of adsorption and reactions of methyl iodide on TiO₂

C. Su
, J. C. Yeh
, C. C. Chen
, J. C. Lin
, J. L. Lin

Department of Molecular Science and Engineering

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

35 Scopus citations

Abstract

The adsorption, thermal reactions, and photochemistry of methyl iodide (CH₃I) were studied on powdered TiO₂ by transmission IR spectroscopy, and on a TiO₂(110) single-crystal surface by TPD and XPS. CH₃I dissociated on the powdered surface to form CH₃O. The presence of isolated hydroxyl groups enhanced its dissociation rate. In the thermal chemistry, CH₄(g) was the major product in the absence of O₂. However, only oxygen-containing intermediates and products were found when oxygen was present, including CH₂O(g), (CH₃)₂O(g), CO(g), CO₂(g), and H₂O(g) was formed via coupling reaction of two adsorbed methoxy groups. O₂ was crucial for CH₃I oxidation in the photochemistry. On the TiO₂ single crystal, the TPD experiment was performed with a multilayer of CH₃I, making a link to the solid-liquid interaction. (CH₃)₂O(g) was also the desorption product in the TPD study. The formation of (CH₃)₂O(g) on TiO₂(110) occurred at much lower temperatures. It started to evolve at ~ 200 K and reached its maximum rate at 250-330 K depending on surface heterogeneity in the TPD study. The Williamson synthesis process was proposed for the generation of (CH₃)₂O(g) in this case. Surface iodine formed by X-ray irradiation on CH₃I-covered TiO₂ was not stable and was desorbed by 570 K.

Original language	English
Pages (from-to)	45-54
Number of pages	10
Journal	Journal of Catalysis
Volume	194
Issue number	1
DOIs	https://doi.org/10.1006/jcat.2000.2909
State	Published - 15 Aug 2000

Bibliographical note

Funding Information:
We gratefully acknowledge the financial support of the National Science Council of the Republic of China (Grants NSC-88-2113-M-006-014 and NSC-88-2113-M-001-025) for this research.

Keywords

FT-IR
Methyl iodide
Photochemistry
Powder
Single crystal
TPD
Thermal reaction
TiO
XPS

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10.1006/jcat.2000.2909

Cite this

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title = "Study of adsorption and reactions of methyl iodide on TiO2",

abstract = "The adsorption, thermal reactions, and photochemistry of methyl iodide (CH3I) were studied on powdered TiO2 by transmission IR spectroscopy, and on a TiO2(110) single-crystal surface by TPD and XPS. CH3I dissociated on the powdered surface to form CH3O. The presence of isolated hydroxyl groups enhanced its dissociation rate. In the thermal chemistry, CH4(g) was the major product in the absence of O2. However, only oxygen-containing intermediates and products were found when oxygen was present, including CH2O(g), (CH3)2O(g), CO(g), CO2(g), and H2O(g) was formed via coupling reaction of two adsorbed methoxy groups. O2 was crucial for CH3I oxidation in the photochemistry. On the TiO2 single crystal, the TPD experiment was performed with a multilayer of CH3I, making a link to the solid-liquid interaction. (CH3)2O(g) was also the desorption product in the TPD study. The formation of (CH3)2O(g) on TiO2(110) occurred at much lower temperatures. It started to evolve at \textasciitilde{} 200 K and reached its maximum rate at 250-330 K depending on surface heterogeneity in the TPD study. The Williamson synthesis process was proposed for the generation of (CH3)2O(g) in this case. Surface iodine formed by X-ray irradiation on CH3I-covered TiO2 was not stable and was desorbed by 570 K.",

keywords = "FT-IR, Methyl iodide, Photochemistry, Powder, Single crystal, TPD, Thermal reaction, TiO, XPS",

author = "C. Su and Yeh, \{J. C.\} and Chen, \{C. C.\} and Lin, \{J. C.\} and Lin, \{J. L.\}",

note = "Funding Information: We gratefully acknowledge the financial support of the National Science Council of the Republic of China (Grants NSC-88-2113-M-006-014 and NSC-88-2113-M-001-025) for this research.",

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T1 - Study of adsorption and reactions of methyl iodide on TiO2

AU - Su, C.

AU - Yeh, J. C.

AU - Chen, C. C.

AU - Lin, J. C.

AU - Lin, J. L.

N1 - Funding Information: We gratefully acknowledge the financial support of the National Science Council of the Republic of China (Grants NSC-88-2113-M-006-014 and NSC-88-2113-M-001-025) for this research.

PY - 2000/8/15

Y1 - 2000/8/15

N2 - The adsorption, thermal reactions, and photochemistry of methyl iodide (CH3I) were studied on powdered TiO2 by transmission IR spectroscopy, and on a TiO2(110) single-crystal surface by TPD and XPS. CH3I dissociated on the powdered surface to form CH3O. The presence of isolated hydroxyl groups enhanced its dissociation rate. In the thermal chemistry, CH4(g) was the major product in the absence of O2. However, only oxygen-containing intermediates and products were found when oxygen was present, including CH2O(g), (CH3)2O(g), CO(g), CO2(g), and H2O(g) was formed via coupling reaction of two adsorbed methoxy groups. O2 was crucial for CH3I oxidation in the photochemistry. On the TiO2 single crystal, the TPD experiment was performed with a multilayer of CH3I, making a link to the solid-liquid interaction. (CH3)2O(g) was also the desorption product in the TPD study. The formation of (CH3)2O(g) on TiO2(110) occurred at much lower temperatures. It started to evolve at ~ 200 K and reached its maximum rate at 250-330 K depending on surface heterogeneity in the TPD study. The Williamson synthesis process was proposed for the generation of (CH3)2O(g) in this case. Surface iodine formed by X-ray irradiation on CH3I-covered TiO2 was not stable and was desorbed by 570 K.

AB - The adsorption, thermal reactions, and photochemistry of methyl iodide (CH3I) were studied on powdered TiO2 by transmission IR spectroscopy, and on a TiO2(110) single-crystal surface by TPD and XPS. CH3I dissociated on the powdered surface to form CH3O. The presence of isolated hydroxyl groups enhanced its dissociation rate. In the thermal chemistry, CH4(g) was the major product in the absence of O2. However, only oxygen-containing intermediates and products were found when oxygen was present, including CH2O(g), (CH3)2O(g), CO(g), CO2(g), and H2O(g) was formed via coupling reaction of two adsorbed methoxy groups. O2 was crucial for CH3I oxidation in the photochemistry. On the TiO2 single crystal, the TPD experiment was performed with a multilayer of CH3I, making a link to the solid-liquid interaction. (CH3)2O(g) was also the desorption product in the TPD study. The formation of (CH3)2O(g) on TiO2(110) occurred at much lower temperatures. It started to evolve at ~ 200 K and reached its maximum rate at 250-330 K depending on surface heterogeneity in the TPD study. The Williamson synthesis process was proposed for the generation of (CH3)2O(g) in this case. Surface iodine formed by X-ray irradiation on CH3I-covered TiO2 was not stable and was desorbed by 570 K.

KW - FT-IR

KW - Methyl iodide

KW - Photochemistry

KW - Powder

KW - Single crystal

KW - TPD

KW - Thermal reaction

KW - TiO

KW - XPS

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SN - 0021-9517

VL - 194

SP - 45

EP - 54

JO - Journal of Catalysis

JF - Journal of Catalysis

IS - 1

ER -