A series of hydrogen transfer reactions has been done using model compounds (donors and acceptors) at reaction conditions consistent with coal liquefaction. Emphasis was placed upon acceptors having C-C linkages and oxygen compounds with functionality likely to be present in coal. The cracking of dibenzyl was shown to be faster than that of diphenylbutane, diphenylmethane, and I-phenylhexane at 400-450 O C . With oxygen-containing compounds, the relative order of reactivity was: furans < phenols < ketones < aldehydes < chain ethers. A study of hydrogen transfer using either a deuterium atmosphere or deuterium-tagged donors was undertaken with the oxygen-containing compounds. It was shown that much of the hydrogen necessary to stabilize free radicals comes from the donor solvent or intramolecular rearrangement and not from dissolved gas.A simplified transient model of diffusion and reaction is considered in the stagnant boundary layer that surrounds a carbon particle during combustion. The model is used to develop local asymptotic stability criteria for analysis of the multiple steady states. A special case arises when carbon monoxide burns outside the boundary layer as the linearized conservation equations are then solvable by a finite Fourier transform. In the more general case, results are obtained by Galerkin's method. Regions of instability created by variation of the particle size and ambient oxygen concentration are presented.
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