YANG Xiaolong1, TANG Liping1,2, XI Chungu1, XIONG Xvmao1, MU Xinyuan1, HU Bin1*
(1. Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P.R. China; 2. Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China)
Abstract: MgO supports were prepared by the different precipitants and further examined as the supports for barium-promoted ruthenium catalyst for ammonia synthesis. The reason resulting in their difference of catalytic activity were explored by X-ray diffraction, N2 adsorption-desorption, X-ray fluorescence spectroscopy, transmission electron microscopy, H2 temperature-programmed reduction, CO2 temperature-programmed desorption, H2 temperature-programmed desorption and N2 temperature-programmed desorption. It is found that MgO prepared by (NH4)2CO3 precipitant facilitate the reduction of ruthenium oxide for Ba-Ru/MgO catalyst, the weak basic sites of Ba-Ru/MgO((NH4)2CO3 as precipitant) appeared at lower temperature and showed higher weak basic site densities compared with the others. At 450 ℃、5.0 MPa and 5000 h-1, catalytic activity of Ba-Ru/MgO catalyst employing (NH4)2CO3 as the precipitant was higher than that of the catalyst prepared by other precipitants under the same reaction conditions, the ammonia concentration in the effluent reached 3.74 %. The addition of Ba promoter significantly decreased the amount of hydrogen chemisorption, increased the number of dissociatively adsorbed N* on the Ru surface and thus accelerated the reaction rate of ammonia synthesis.
Key words: Ammonia synthesis; Ruthenium catalyst; Precipitants; Basic site.
E-mail: yxlwin@163.com
Journal of Molecular Catalysis, Vol. 26, Issue 1, 2012, 1-9
