Abstract: A process for reducing the sulfur content of coal, by the treatment of coal particles, contained in an aqueous slurry, of floatable coal-oil particles, with an oxygen-containing gas at elevated temperature and pressure, comprising the steps of:(a) feeding the oxygen-containing gas and the aqueous slurry of floatable coal-oil particles, at process pressure, to a bottom zone of a vertically disposed, elongated reactor vessel;(b) passing the gas and aqueous slurry in cocurrent flow upwardly through a baffled reaction zone, maintained at reaction temperature and pressure, the baffled reaction zone having a plurality of baffle plates spaced therethrough generally normal to the reactor wall, each baffle plate having a configuration generally conforming to the internal diameter of the reactor vessel and a plurality of apertures disposed about the baffle plate, to provide a total aperture area equal to from about 3% to about 28% of the vessel cross-sectional area as free area;(c) continuously withdrawing the aqueous