Abstract
Mixtures of finely ground coals of various ranks and catalysts were pyrolyzed for 2 h in N/sub 2/, usually at 700/sup 0/C. A series of microprobe analyses showed that the catalysts were widely dispersed as a result of this treatment. Aliquots of the chars were ground and the gasification rates in CO/sub 2/ and H/sub 2/O(g) measured in a thermogravimetric balance; BET-surface areas were measured using CO/sub 2/ and N/sub 2/ adsorbents. The effect of alkali catalysts in raising the reactivity of coal chars is not due to a massive increase in the internal surface area of the chars as a result of the catalyst salts. Rather, there is a reduction in both the CO/sub 2/ and N/sub 2/ BET-areas measuring the ultramicropores and the micropores respectively. The effect of large atomic concentrations of Li, and probably other alkali salts, is to occlude some portions of the char from the ingress of reactants (or the egress of products). It is possible that the limited variation of activation energies upon catalysis indicates that the salt primarily acts by creating new active sites. It will be necessary to have a specific probe molecule sensitive only to basal edge sites in the presencemore » of alkali cations, and, therefore this remains a subject worthy of further investigation. 3 figures, 1 table.« less
Published Version
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