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Computational studies of the structure of vanadium oxide clusters and their reactions with halocarbons

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Computational studies of the structure of vanadium oxide clusters and their reactions with halocarbons

Wei, Yin (2005) Computational studies of the structure of vanadium oxide clusters and their reactions with halocarbons. Masters thesis, Concordia University.

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Abstract

Vanadium oxides are key industrial catalysts in the oxidation and functionalization of various chemical compounds, and studies of gas-phase vanadium oxide clusters provide an avenue to explore the reactive sites implicated in surface catalysis. An extensive amount of experimental data has been reported on the gas-phase fragmentation of vanadium oxide cluster ions and their reactions with environmentally-relevant halocarbons. Our computational studies aim at further understanding the structure and properties of vanadium oxide clusters, as well as their reactivity towards fluorocarbons. Accordingly, we report a systematic density-functional theory (DFT) study of the structural and electronic properties of V x O y + and V x O y clusters, and investigate their reactions with CH 2 F 2 and CH 3 CF 3 by DFT calculations. Our results suggest that both B3LYP/TZVP and PLAP4/DZVP+aux. are appropriate model chemistries to investigate vanadium oxide clusters, but the latter is less computationally intensive, and thus more suitable for large clusters. Stable ground-state and low-lying excited-state structures and their electronic properties are obtained for both V x O y + and V x O y (x = 1-4, y = 1-10) clusters with the PLAP4/DZVP+aux. model chemistry. The molecular structures and electronic properties of large polyvanadium oxide clusters are systematically investigated and reported for the first time. The reaction of V 2 O 4 + with fluorocarbons was investigated with the B3LYP/TZVP model chemistry. Oxygen transfer and stepwise HF abstraction from the fluorocarbon are observed in the reactions of V 2 O 4 + with CH 2 F 2 and CH 3 CF 3 , respectively. These reaction mechanisms help explain why larger clusters such as V 4 O 8 + were observed to be chemically inert towards CH 2 F 2 , while the reactivity of V x O y + cluster ions towards CH 3 CF 3 was not found to depend on cluster size experimentally.

Divisions:Concordia University > Faculty of Arts and Science > Chemistry and Biochemistry
Item Type:Thesis (Masters)
Authors:Wei, Yin
Pagination:viii, 144 leaves : ill. ; 29 cm.
Institution:Concordia University
Degree Name:M. Sc.
Program:Chemistry and Biochemistry
Date:2005
Thesis Supervisor(s):Peslherbe, Gilles H
ID Code:8342
Deposited By:Concordia University Libraries
Deposited On:18 Aug 2011 14:22
Last Modified:18 Aug 2011 15:35
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