Miike coal was quantitatively oxidized at 150℃ using ^<18>O_2 in a closed system equipped with a circulator. Gas evolution during oxidation was monitored by mass spectrometer (MS). To investigate the surface reactivity, the oxidized coal was pulverized under vacuum. Composition of out gas was monitored by MS. Water and carbon monooxide were main products in both oxidation and pulverization. Changes in coal surface before and after oxidation was observed by an environment controlled atomic force microscope (AFM). No pore structure was observed under inert atomosphere and a slight surface deformation was detected when coal surface was exposed to oxygen.
