Effect of redox co-precipitation methods on structure and catalytic activity of Ru/CeO2 catalysts for ammonia synthesis

Abstract

The Ru/CeO2 catalyst was prepared by redox co-precipitation methods, including normal precipitation, reverse precipitation and parallel flow precipitation. The obtained catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), CO chemisorption, and field-emission scanning electron microscopy (FE-SEM). The obvious difference of Ru dispersion and surface texture exist in the catalysts prepared by different methods. The activity test showed that the ammonia synthesis activity of the Ru/CeO2 catalyst prepared by reverse precipitation was 12.6% at 10 MPa, 10000 h-1, and 425°C, which was much higher than those obtained by other methods. Such a high catalytic attributes to three facts: the easier reduction, the much higher dispersion of Ru (45.6%) and bigger surface area (120 m2/g).