Preparation and characterization of bismuth molybdate catalyst for oxidative dehydrogenation of n-butene into 1,3-butadiene

alpha-Bi2Mo3O12 and gamma-Bi2MoO6 catalysts were prepared by co-precipitation method, and they were applied to the oxidative dehydrogenation of n-butene into 1,3-butadiene in a continuous flow fixed-bed reactor. Formation of alpha-Bi2Mo3O12 and gamma-Bi2MoO6 catalysts was well confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The gamma-Bi2MoO6 catalyst exhibited a better catalytic performance than the alpha-Bi2Mo3O12 catalyst. Catalytic performance of gamma-Bi2MoO6 strongly depended on the pH value used in the co-precipitation step. It was also revealed that a mixed catalyst comprising gamma-Bi2MoO6 (90 wt%) and small amount of alpha-Bi2Mo3O12 (10 wt%) showed the best catalytic performance due to the synergy effect of two components. It is believed that the high catalytic performance of the mixed catalyst resulted from high diffusion coefficient of lattice oxygen in the gamma-Bi2MoO6 and from abundant chemisorption sites for n-butene in the alpha-Bi2Mo3O12.