HYDROGENATION OF COALS CATALYZED BY MO - EFFECT AND TRANSFORMATION OFPOROUS TEXTURE

The hydrogenation of 24 coals (LV bituminous to lignite) in the presen ce of Mo was studied. The hydrogenation temperatures were 300, 350 and 400 degrees C, the hydrogen pressures 5 and 10 MPa, and the reaction time 30 min. At 300 degrees C the Mo salts deposited on the coals do n ot decompose to the active MoS2 state, so the hydrogenation process is not significantly different from that in the absence of a catalyst an d is influenced by the ease of diffusion, with a consequent increase i n conversion with increasing macropore volume. At 350 and 400 degrees C, MoS2 acts as a good catalyst and conversion is much greater than in the absence of a catalyst. Under these conditions, opening of pores i n the coals has been detected as conversion increases; micropores deve lop to macropores in such a manner that the MoS2 particles can penetra te progressively into pores originally inaccessible, so an increase in the micropore volume or surface area favours conversion. This pore-op ening is accompanied by an increase in cross-link density. At 5 MPa of H-2, and increasing with temperature, some of the radicals formed are incorporated into the macromolecular structure by repolymerization re actions which result in blockage of the microporosity.