Fundamental studies of retrograde reactions in direct liquefaction

Abstract

We have tried to get definitive structural information on the CC -O polymers from a variety of analytical techniques. However, in ali cases the results were not conclusive. This lack of confirmation has bothered us. In view of the need for a better characterization of the model polymers before drawing definitive conclusions from liquefaction or pyrolysis results, we have reexamined some of the previous analyses and have conducted further characterization of the CC -O polymers by elemental analysis and FT-lR spectroscopy.

The dual role of oxygen functions in coal pretreatment and liquefaction: Crosslinking and cleavage reactions

“…The reason for this is not clear, but it may be due to catalytic activity of the potassium. In previous work, higher pyrolysis CO 2 yields have generally been associated with lower liquefaction yields [4].…”

“…Also, since 3-methoxy-4-hydroxyphenethyl alcohol (homovanillyl alcohol) is commercially available, we also proceeded with the synthesis of the 3-methoxy analog of the above polymer. Except for the missing methyl side chain, this polymer (-(m-OMe)C 6 H 3 -O-CH 2 CH 2 -) is identical to the polymer that could not be obtained in high purity via direct polymerization of eugenol during the previous contract [4]. With these two polymers in hand, we would then be in a very good position to see whether the unusual cleavage and crosslinking behavior of the -C-C-O-linkage in lignins is mirrored by the behavior of the same linkage in alcohol-free polymers.…”

“…The apparent absence of competitive crosslinking for the -(C 6 H 4 -O-CH 2 CH 2 ) n -polymer is in marked contrast to the polyeugenol (nominal structure -[C 6 H 3 (o-Me)-O-CH(CH 3 )CH 2 ] n -) that we prepared and studied briefly in the previous contract [4]. With that polymeric model of low-rank coal, we saw facile thermal generation of monomeric and other small fragments, but rapid crosslinking, as evidenced by low yields not only in pyrolysis but also from liquefaction in a very good hydrogen-donor solvent.…”

“…The carboxyl radical then decomposes to CO 2 and phenyl radical (3). Phenylnaphthalenes result from net displacement of a naphthyl hydrogen by phenyl radical (4). If the phenyl radical were to abstract hydrogen from pyridine or naphthalene prior to successful addition, pyridinyl and naphthyl radicals would result.…”