The condensed polynuclear aromatic clusters of coal are believed to be linked principally by straight-chain aliphatic bridges varying from 0 to 4 carbon atoms in length and the cleavage of these linkages is expected to be an important step in the coal liquefaction process. This study focuses on the means by which Lewis acid catalysts, specifically AlCl/sub 3/ and ZnCl/sub 2/, promote the cleavage of these linkages. To facilitate product identification and interpretation of reaction mechanisms, organic compounds which model the aliphatic bridges were used on substrates. All experiments were performed in a magnetically stirred autoclave under either an H/sub …
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California Univ., Berkeley (USA). Lawrence Berkeley Lab.
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The condensed polynuclear aromatic clusters of coal are believed to be linked principally by straight-chain aliphatic bridges varying from 0 to 4 carbon atoms in length and the cleavage of these linkages is expected to be an important step in the coal liquefaction process. This study focuses on the means by which Lewis acid catalysts, specifically AlCl/sub 3/ and ZnCl/sub 2/, promote the cleavage of these linkages. To facilitate product identification and interpretation of reaction mechanisms, organic compounds which model the aliphatic bridges were used on substrates. All experiments were performed in a magnetically stirred autoclave under either an H/sub 2/ or N/sub 2/ atmosphere at elevated pressure to determine the role of H/sub 2/. Reaction temperatures ranging from 200 to 350/sup 0/C were used to avoid the complication of pyrolysis reactions. Reaction products were identified with the aid of gas chromatography/mass spectrometry, and quantitative product yields were determined by gas chromatography. Experiments with AlCl/sub 3/ and the substrates containing two phenyl rings linked by 0 to 4 carbon atoms showed that AlCl/sub 3/ catalyzed cleavage of all the aliphatic bridges. ZnCl/sub 2/ was totally inactive in cleaving the alkyl bridges in these compounds. Substitution of a phenyl group by a hydroxyphenyl or a naphthyl group in the model compounds promoted the cleavage of aliphatic linkages in the presence of AlCl/sub 3/. In contrast to reactions with the diphenylalkanes, ZnCl/sub 2/ was also found to catalyze the cleavage of these compounds. Plausible reaction mechanisms are proposed which explain the experimental results. The role of gaseous H/sub 2/ in these mechanisms was also investigated.
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Taylor, N. D.Chemistry of coal model compounds: cleavage of aliphatic bridges between aromatic nuclei catalyzed by Lewis acids.,
thesis or dissertation,
April 1, 1978;
Berkeley, California.
(https://digital.library.unt.edu/ark:/67531/metadc1208587/:
accessed March 30, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT Libraries Government Documents Department.