Elucidation of hydrogen behavior in coal using a tritium tracer method: Hydrogen transfer reaction of coal with tritiated gaseous hydrogen in a flow reactor

The hydrogen transfer reactions of three Argonne coals with tritiated gaseous hydrogen were carried out using a flow fixed-bed reaction system in the presence of Pt/Al2O3 catalyst at a temperature range 200-300 degreesC and under pressure of 1.5-5.0 MPa to trace the behavior of hydrogen in coal. In the reactions under a constant pressure of 5.0 MPa, it was found that the hydrogen exchange between tritiated hydrogen atoms generated from the Pt catalyst and hydrogen in functional groups such as hydroxy groups proceeded at temperatures as low as 200 degreesC for all coals studied. The results also indicate that hydrogen transfers to decompose ether linkages and reduce carbonyl groups in coal proceeded substantially at temperatures as low as 200 degreesC for lignite Beulah-zap (ND) and middle rank Illinois No. 6 (IL) coals. The amount of functional groups in the tritiated coal achieved a maximum at 250 degreesC for all coals examined. Hydrogen exchanges with hydrogen in the benzylic position and the phenoxy ring were observed at a perceptible extent at 300 degreesC. Substantial decarboxylation of lignite ND coal was also observed at 300 degreesC. When the pressure dependence was investigated at a constant temperature of 250 degreesC, it was found that the amount of hydroxy groups in tritiated coal increased with both the decomposition of ether linkages and the reduction of carbonyl groups.