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University of California – Berkeley

1. Chin, Ya Huei. Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters.

Degree: Chemical Engineering, 2011, University of California – Berkeley

Molecular insights and the kinetic relevance of reaction elementary steps for methane activation on Group VIII metal and oxide clusters are established based on kinetic, isotopic, and theoretical assessments. These fundamental understandings enable accurate prediction of complex rate dependencies and cluster size effects during methane conversion reactions in catalytic partial oxidation, reforming, and combustion processes.Kinetics of methane reactions with oxygen are described by several regimes, each with unique rate dependencies and kinetic requirements, as the identities of the kinetically-relevant step and the most abundant surface intermediates vary with the surface and bulk oxygen contents of Pt and Pd clusters. C-H bond activation is the kinetically-relevant step in all regimes except for one that occurs immediately before the complete oxygen depletion. C-H bond activation steps may, however, proceed via mechanistically distinct paths of oxidative insertion of metal atom, oxidative insertion coupled with H abstraction, or H abstraction routes, over metal-metal, oxygen-metal, or oxygen-oxygen site pairs, respectively, thus exhibiting different activation enthalpies and entropies. The predominant route for C-H bond activation is dictated by the coverages and reactivities of oxygen on cluster surfaces and accessibility of metal atom to methane reactants. In a narrow regime before the complete oxygen consumption, C-H bond activation becomes kinetically inconsequential on oxygen-depleted surfaces and oxygen dissociative-adsorption steps limit methane conversion rates. The relation among oxygen coverages, oxygen reactivities, and methane reaction paths leads to a single-valued functional dependence of reactive methane collision probabilities on oxygen chemical potentials at the cluster surfaces. The oxygen chemical potentials are given by kinetic coupling of the generation and removal of reactive oxygen atoms and thus are kinetic properties of methane reactions; they become a thermodynamic property only in the limiting case of equilibrated oxygen dissociative-recombination steps. The fate of oxygen during catalysis was rigorously defined as the reactive collision probabilities for CO oxidation relative to those for methane and was measured at low oxygen coverages on Pt in which CO is most likely to desorb before encountering an oxygen atom and undergoing further oxidation to carbon dioxide. The reactive collision probabilities are much larger for CO oxidation than for methane oxidation; these results have unequivocally confirmed that CO and hydrogen, if formed on and desorbed from catalytic surfaces, rapidly undergo sequential oxidation to form carbon dioxide and water and that direct CO and hydrogen formation via molecular coupling of methane and oxygen is impractical at any residence time required for practical extents of methane conversion. Thermodynamics of oxygen dissolution from cluster surfaces into the bulk, cluster size and metal coordination effects on thermodynamic tendencies of bulk oxidation, and their…

Subjects/Keywords: Chemical Engineering; Chemistry; catalysis; chemisorbed oxygen; combustion; group VIII metal; kinetics; methane activation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chin, Y. H. (2011). Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/6gd4d71p

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Chin, Ya Huei. “Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters.” 2011. Thesis, University of California – Berkeley. Accessed October 17, 2019. http://www.escholarship.org/uc/item/6gd4d71p.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Chin, Ya Huei. “Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters.” 2011. Web. 17 Oct 2019.

Vancouver:

Chin YH. Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters. [Internet] [Thesis]. University of California – Berkeley; 2011. [cited 2019 Oct 17]. Available from: http://www.escholarship.org/uc/item/6gd4d71p.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Chin YH. Kinetic Consequences of Chemisorbed Oxygen Atoms during Methane Oxidation on Group VIII Metal Clusters. [Thesis]. University of California – Berkeley; 2011. Available from: http://www.escholarship.org/uc/item/6gd4d71p

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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