Catalyst plays an important role in direct coal liquefaction. This paper focuses on the catalytic behavior of a novel SO42-/ZrO2 superacid catalyst in coal hydro-liquefaction. A series of hydro-liquefaction experiments were conducted under mild conditions -400 degrees C, 30 min and H-2 initial pressure 4 MPa in a batch autoclave with a volume of 100 ml. The catalytic property of SO42-/ZrO2 was compared with FeS and FeS + S by Shenhua coal. The liquefaction products catalyzed by different catalysts were analyzed by FTIR spectrum, H-1 NMR spectrum and element analysis. In addition, the SO42-/ZrO2 solid superacid was characterized. The results indicated that the SO42-/ZrO2 solid superacid shows outstanding catalytic property for direct liquefaction of coal and gives the highest coal conversion and gas + oil yield compared to other two catalysts. The THF conversion and the extraction yield of CS2/NMP mixed solvent of liquefied coal catalyzed with SO42-/ZrO2 are 76.3%, daf and 81.2%, daf respectively, and the yield of gas + oil is 62.5%, daf under the condition used in this study. The pyrolysis of coal macromolecular clusters can be promoted by catalysts such as FeS, FeS + S and SO42-/ZrO2. There may be only the pyrolysis of volatile matter and the relaxation of the structure of coal macromolecular clusters in non-catalytic liquefaction at 400 degrees C. Added sulfur in FeS can improve the catalytic activity of hydrogenation. SO42-/ZrO2 is a notable catalyst in the study of coal direct liquefaction because it shows excellent catalytic activities for the pyrolysis and the hydrogenation. In addition, it has been found that the C-O bond is the most stable group in coal liquefaction reaction except for the covalent bond between carbon and carbon. (c) 2006 Elsevier Ltd. All rights reserved.