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Reactions of phenoxy radicals under coal liquefaction conditions

Citation

Pichaichanarong, Puvin (1985) Reactions of phenoxy radicals under coal liquefaction conditions. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-04102008-152250

Abstract

This thesis presents the results of model compound studies that address the rate parameters for hydrogen abstraction involving phenoxy radicals, and the products, pathways, and kinetics of phenoxy radical recombination, under coal liquefaction conditions. Thermolysis of selected mixtures of model compounds containing functionalities found in coal-related materials were conducted in a batch reactor at temperatures between 250 and 450°C. The reaction products were analyzed by GC, HPLC, GCMS, and NMR, with emphasis on the identification of radical recombination products. Reactions were modeled by free radical mechanisms and rate parameters at liquefaction temperatures for hydrogen abstraction and recombination reactions involving phenoxy radicals were determined.

Phenoxy radicals were found to be more reactive than benzyl radicals, rapidly abstracting hydrogen atoms to form stable molecules. Hydrogen abstraction by a phenoxy radical from a phenol was faster than from a hydrocarbon. Application of the rate parameters determined for one model compound mixture to other systems of compounds indicated good match with experimental data.

Analysis of the recombination products revealed that, when no good hydrogen donor solvents were available, phenoxy-phenoxy radical recombination products were more abundant than phenoxy-benzyl recombination products. Certain differences and similarities were observed between the behavior of single-ring aromatics and their condensed-ring counterparts. Whereas phenol was quite stable at 400° C, 1-naphthol was found to undergo considerable conversion. A mechanistic scheme for 1-naphthol decomposition was proposed which accounted for the major reaction products. Thermolysis of various model compound mixtures indicated similar patterns exhibited by single-ring and double-ring aromatics with respect to the pathways of oxygen-oxygen and oxygen-carbon free radical recombination.

Bimolecular reverse disproportionation was demonstrated to be satisfactory in explaining naphthol conversion. Furthermore, dehydration accounted for furan formation and concerted reactions could possibly be involved in naphthalene formation. Thus, in addition to unimolecular dissociation reactions, several pathways exist for the thermal reactions of oxygen compounds.

These model compound studies indicated that the results of a simple model compound mixture could give insight into the understanding of a more complex reaction network. This insight will ultimately provide the link between model compound results and the reactions of coal-related materials.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Gavalas, George R. (advisor)
  • Corcoran, William Harrison (advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:6 December 1984
Record Number:CaltechETD:etd-04102008-152250
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-04102008-152250
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1335
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:21 Apr 2008
Last Modified:26 Dec 2012 02:37

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