alpha-Bi2Mo3O12 and gamma-Bi2MoO6 were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of C-4 raffinate-3 to 1,3-butadiene. Both alpha-Bi2MO3O12 and gamma-Bi2MoO6 catalysts were thermally and structurally stable during the catalytic reaction. They exhibited a stable catalytic performance in the oxidative dehydrogenation of C-4 raffinate-3 without catalyst deactivation. However, the catalytic performance of gamma-Bi2MoO(6) was superior to alpha-BiNO3O12 due to the facile oxygen mobility of gamma-BiMoO6. The reactivity of n-butene isomers in the C-4 raffinate-3 decreased in the order of 1-butene > trans-2-butene > cis-2-butene over both alpha-Bi2Mo3O12 and gamma-Bi2MoO6 catalysts. Steam played an essential role in suppressing CO2 formation, and furthermore, served as a heat sink for preventing hot spots or reactor run-away. In the catalytic reaction with respect to reaction temperature, the maximum conversion of n-butene (ca. 66%) and the maximum yield for 1,3-butadiene (ca. 60%) were achieved at 440 degrees C over the gamma-Bi2MoO6 catalyst (n-butene: oxygen: steam = 1:0.75:15). (c) 2006 Elsevier B.V. All rights reserved.