Study On Ba-MgO Supported Ruthenium Catalyst For Ammonia Synthesis: Barium Promoter Effect And Doping

In this paper, we studied barium promoter that key activity affecting factor of ruthenium catalysts at begins, and doping amount of barium by different method, the effect of promoters on the adsorption of hydrogen inhibition were also studied. Scanning electron microscopy(SEM), temperature programmed reduction of H2(H2-TPR), X-ray diffraction (XRD) and N2-physisorption were carried out to investigate surface morphology, phase and surface texture of supports and Ru-based catalysts, the activities of catalysts for ammonia synthesis were measured at 10 MPa, 10000h-1 and 375?425 ?. The main research contents and results are as follows:1. Barium promoter doped method had significant influence on the property of catalysts. Compared with the traditional water precipitation method, organic solution precipitation method reduced the destruction ofMgO support and it was the same with the trituration method. Although Ba promoter introduced by ultrasonic-precipitation-strong electrical adsorption increased the dispersion of barium promoter, Ba2+ could not be adsorbed on the surface of support with positive charge directly. Control the doping amount of barium promoter was still not able to come true.2. A series of catalysts were prepared by ultrasonic-precipitation with the modified of EDTA. The results showed:the surface hydroxyl group of EDTA could reaction with carbonyl group of MgO, it not only effectively improved the surface morphology of support showing nearly spherical, but also could formed [Ba(EDTA)]2-, and changed the charge of barium promoter, effectively controlled doping amount of barium promoter. The outlet ammonia concentration of catalyst prepared by ultrasonic-precipitation with the modified of EDTA(EDTA/Ba=1/2) reached 18.38% at 10 MPa,425?,1 0000h-1 conditions.3. A series of magnesia supported, ruthenium-based ammonia synthesis catalysts, variously promoted with alkali? alkali-earth and rare earth compounds, were prepared by chemical-coprecipitating with ultrasonic technology, aiming at investigating the effect of such promoters on the adsorption of hydrogen inhibition by temperature programmed desorption(TPD). Alkali promoters were effective electron or structural promoter for Ru/MgO catalysts, but also can increasing the surface alkalinity and hydrogen inhibition; rare earth mental oxides were decrease of hydrogen competition during nitrogen adsorption; The Ru/Sm-Ba-MgO catalyst showed the highest catalytic activity for the ammonia synthesis with Concentration of ammonia 19.53%(10 MPa, 425?,10000 h-1). Such high catalytic activity was due to Synergistic effect of Ba and Sm:electrodonating and structural property of Ba to Ru metal and eliminating hydrogen inhibition by Sm.4. A series ruthenium catalysts were prepared by sol-gel method with the assistance of different surfactant additive. Barium salt was doped directly during the sol-gel process, using reticular structure coated promoter. The outlet ammonia concentration of catalyst prepared by sol-gel method with 5% PAAS reached 17.32% at 10 MPa,425?, 10000h-1 conditions.