Study On Modified Ba-MgO Supported Ruthenium Catalyst For Ammonia Synthesis

In this paper, we studied from the modified supports of Ba-doped nano-magnesia（Ba-MgO）, and the effects of preparation methods, conditions, modification of surfactants on the Ba-MgO and its Supported Ruthenium Catalyst for Ammonia Synthesis were also investigated, then scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, X-ray diffraction（XRD） and N2-physisorption were carried out to investigate surface morphology, phase and surface texture of the modified supports and Ru-based catalysts, the activities of catalysts for ammonia synthesis were measured at 10 MPa, 10000 h^-1 and 375～425℃. The main research contents and results are as follows:1. The preparation method had significant influence on the surface morphology of MgO. Compared with the one step precipitation method, ultrasonic precipitation method could make Ba-MgO increasing the specific surface area, reducing particle size, and pores becoming more uniform, the phenomenon of particles agglomeration was also greatly reduced. And the effective doping amount of Ba could greatly increase the dispersion of Ru particles.2. The preparation conditions has significant influence on the surface structure of Ba-MgO support and catalyst activity of Ru/Ba-MgO, the best preparation conditions are as follows: washing with ethanol for 20 min, the ammonia as precipitation agent, the pH value of precipitation liquid is 10.5, the precipitation temperature is 60～70℃, drying with IR, roasting the support precursor in the vertical tube.3. A series of modified Ba-MgO supports and Ru/Ba-MgO catalysts were prepared by ultrasonic-precipitation method. The results showed: the cation and anion of surfactants could form freezer on the precipitated surface, it not only inhibited the growth rate of ions on the formation of precipitated surface, but also prevented the agglomeration, and effectively improved the surface morphology of support. the outlet ammonia concentration of as-prepared catalyst can reach 17.01% at 10 MPa, 425℃, 10000 h^-1 under .4. A preliminary study the periodic adsorption behavior of BaO molecules on MgO surface was used with density functional theory, the research results show that, MgO （200） crystal face is the most stable in five crystal faces and tending to fact of Mg and O atoms are simultaneously exposed. The best adsorption geometry of BaO molecules adsorbed in the MgO（200） crystal face is parallel adsorption of Ba and O atoms.