Investigation of mechanisms of hydrogen transfer in coal hydrogenation. Phase II annual report, January-December 1978

Abstract

The objective of this study is to develop an understanding of the mechanism of hydrogen transfer to coal and its intermediates during liquefaction. The first 18 month period consisted of experimentation with model compounds and the present period is based upon hydrogen transfer liquefaction of coal asphaltenes. This report is written to summarize the first 12 months of the latter period. It appears that the results of experiments with coal and asphaltenes are consistent with those of the model compounds, and the knowledge of both phases can be combined. Specifically, coal liquefaction consists of the thermal cleavage of bonds followed by the stabilization of the resulting free radicals by (1) abstraction of hydrogen from a donor solvent, (2) reaction with other radicals, or (3) attachment (adduction) with products and/or solvent. Coal primarily cracks in C-C, C-O, or C-S linkages between aromatic type units such that transferred hydrogen exists on carbons ..cap alpha.. to a aromatic ring. The coal free-radicals abstract hydrogen from any available source such as hydroaromatics, naphthenes, alkyl aromatics and dissolved hydrogen, in roughly that order. Solvent losses through adduction (particularly in poor donors) and isomerization are significant, and presumably will lead to decreased activity or effectiveness ofmore » recycled solvents. The use of nmr gives an improved understanding of the mechanism of reactions involved in the liquefaction of coal. In this project, the /sup 2/H nmr results in coal liquefaction are consistent with previous kinetic studies on model compounds with deuterium scrambling superimposed.« less