For evaluation of solvent involving coal derived liquids during coal liquefaction, reaction mechaninsm and rate of coal dissolution and semi-coke formation were examined at 723 K under 10 MPa of nitrogen or hydrogen with tetralin, naphthalene and creosote oil for Taiheiyo and Illinois No.6 coals.
Semi-coke was defined on the basis of kinetics as pyridine insolubles obtained by rehydrogenating reaction residue at 723K and 10 MPa of hydrogen with an excess amount of tetralin and its fromation reaction was decelerated in the presence of hydrogen donor solvent.
The reaction rate of coal dissolution to pyridine solubles can not represent as a n-th order reaction with respect to concentration of hydrogen donor solvent under the conditions in which semi-coke formation is observed at the same time with formation of lighter liquid products during coal liquefaction.
Pyridine solubles contained inherently in original Illinois No.6 coal seemed to be not concerned with the semi-coke formation even under nitrogen atmosphere. The semi-coke formation, however, occurred with mixed solvent such as creosote oil even under 10 MPa of hydrogen.
These results suggested that the semi-coke formation reaction depended on the concentration of transferable hydrogen in solvent, and mass transfer in the solvent and coal particles was also not ignored to evaluate solvent for coal liquefaction as well as chemical parameters such as the hydrogen donating ability, the amount of transferable hydrogen in solvent.
