Coal Liquefaction Reaction Mechanism and Coal Reactivity Based on Hydrogenation Characteristics Using Tetralin Solvent
Reaction mechanism of coal liquefaction and coal reactivity of 10 different coals for liquefaction were examined with an excess amount of tetralin at 723K under 10MPa of nitrogen gas atmosphere. The amount of naphthalene formed from tetralin during coal liquefaction was measured by FID-GC for the determination of hydrogen consumptions of coals.
Coal was considered consisting of three different reactive components, I0, C1 and C2 defined from their hydrogenation characteristics. The component I0 was inherently inert in the present reaction condition. The component C1 formed consecutively oils and gases via preashaltenes and asphaltenes with consuming hydrogen. On the other hand, the component C2 formed oils and gases directly without consuming external hydrogen from the solvent and the gas phase.
Hydrogen consumptions for various coals were predicted by the initial content of C1 in original coals within negligible small error. The amount of hydrogen consumed for formation of preaphaltenes and asphaltenes was not as predominant as that for oil formation involving gases formed. These results, furthermore, showed that reaction selectivities between intermolecular hydrogen of tetralin and gaseous hydrogen were different even in the same reaction condition, i.e. temperature and pressure. It was suggested that the difference among chemical structures of solvent having transferable hydrogen affected an efficient hydrogen utilization in coal liquefaction and that the role of hydrogen donor solvent might be enhanced by hydrogenation of aromatic ring during heating in the presence of catalyst.