Generalized kinetic model for the uncatalyzed hydroliquefaction of coal

Abstract

A kinetic model, incorporating dehydrogenation of tetralin, for the liquefaction of coals has been developed and tested with data from a variety of lowand medium-rank coals. The model postulates that coal essentially consists of three lumps. Of these, one dissociates almost instantaneously, the second is characterized by slow internal hydrogen shuttling, and only the third lump requires external hydrogen. The reactivity of each lump does not vary between coals; however, different coals are found to contain different fractions of each lump. The rate of reaction of coal is about 3 orders of magnitude faster than the tetralin dehydrogenation reaction. This study clearly shows that it is not only the solvent's capacity to donate hydrogen but also the rate at which hydrogen is donated that is important in coal liquefaction.

Generalized kinetic model of catalyzed hydroliquefaction of coal incorporating Tetralin dehydrogenation reaction

“…Hydrogen Solubilities in Tetralin. The model proposed (Ghosh et al, 1986) does not differentiate between dissolved hydrogen and hydrogen transferred from tetralin.…”

“…Table I contains a summary of experiments conducted by using continuous-flow or batch reactor with various catalysts. In a previous publication (Ghosh et al, 1986), a generalized model for coal liquefaction was proposed where coal was considered as being comprised of three components. Of these, one component was considered to dissociate almost instantaneously on application of temperature.…”

“…The reactivity of each of these three components in coal was found to be invariant of coal; however, the fractions of these components were coal dependent. Studies with Victorian brown coal revealed that (Ghosh et al, 1986) about 30 wt % coal was involved in pure thermal dissolution, whereas 12 wt % coal degraded very slowly, requiring little external source of hydrogen. The remaining portion underwent dissociative reactions only in the presence of a good donor solvent such as tetralin.…”

“…The amount of hydrogen initially dissolved in tetralin prior to the start of the liquefaction reaction was calculated by using the same procedure as reported earlier (Ghosh et al, 1986). The empirical equation used to calculate the mole fraction of hydrogen in tetralin as a function of liquefaction temperature and pressure is given by In XH2…”

“…Recently Ghosh et al (1986) presented a generalized kinetic model for the uncatalyzed hydroliquefaction of coal incorporating donor solvent (tetralin) dehydrogenation. In this paper, a previously reported kinetic model for the uncatalyzed liquefaction (Ghosh et al, 1986) is examined for its applicability to catalyzed hydroliquefaction (iron-, iron-tin-, and haematite-based catalysts) of Victorian brown coal.…”