Partially reduced multi-component heteropoly compound catalysts with the Keggin structure were prepared and used for the selective oxidation of propane. The influence of the pore diameter of the support on the reaction was also tested. Results show that the partially reduced heteropoly acid catalyst exhibits the highest activity for the selective oxidation of propane under the optimum reaction conditions: T = 390degreesC, C3H8:O-2:H2O:N-2 = 1:2:2:5 (mol/mol) and space velocity = 1500 h(-1). The maximum conversion of propane and the maximum yield of acrylic acid reached 38 and 14.8%, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.