The kinetics of coal electrolysis was studied on a bench continuous coal electrolytic cell setup at intermediate temperatures by applying galvanostatic polarization techniques. The results showed that coal oxidation takes place during the contact of the coal particles with the electrode and it is directly related to electrode composition and the presence of Fe(III) ions in the slurry solution. Coal electro-oxidation by Fe(III) is the limiting step in the oxidation of a 0.02 g mL(-1) coal slurry containing 100 mM Fe(II)/Fe(III) at high currents (100 mA) at 108 degrees C with a 65 mL min(-1) flow rate. The study suggests that the films that grow at the surface of the coal particles limit the coal conversion. A mechanism is proposed to describe the coal oxidation process. (C) 2010 Elsevier B.V. All rights reserved.