Study On Preparation And Forming Of Ba-MgO Supported Ruthenium Catalyst For Ammonia Synthesis

In this paper,we studied the preparation methods of Ba-doped nano-MgO(Ba-MgO),the impregnation conditions,modification of saccharides on the Ba-MgO and prepared a series of Ba-MgO supported Ru catalysts(Ru/Ba-MgO)for ammonia synthesis.We also investigated the effect of forming conditions on mechanical strength of supports.Then scanning electron microscopy(SEM),X-ray diffraction(XRD)X-ray energy dispersive spectrometer(EDS),N2-physisorption and H2 pulse chemisorption were carried out to investigate surface morphology,phase and surface texture of the 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 ultrasonic-electrical adsorption(UEA)method,co-precipitation(CP)method could make Ba-MgO increasing the specific surface area,but microporous disappeared and the dispersion of Ru was the lowest,so the activity of Ru/Ba-MgO by CP method was the lowest,the suitable Precipitation agent was NH4HCO3.And during sol-gel method process,addition of surfactants could improve the activity of catalyst.The outlet ammonia concentration of catalyst with 5%sodium polyacrylate(PAAS)reached 17.32%at 10 MPa,425?,10 OOOh-1 conditions.2.The impregnation conditions had significant influence on the catalytic activity of Ru/Ba-MgO,the suitable impregnation conditions are as follows:the suitable solvent was tetrahydrofuran,the impregnation time of 10 h was needed,increasing impregnation step and vacuum drying could improve the activity.The mixture of Ru3(CO)12 and MgO was treated at vacuum,80? conditions,the activities of catalysts improved.3.The formed MgO could not be directly prepared from MgO powder without any binder.The mechanical strength of formed MgO increased with the forming pressure,but textural of MgO could be changed and the catalytic activity of Ru/Ba-MgO decreased.The binders could effect mechanical strength and activity,and PEG-6000 was the best one of three binders,the mechanical strength of formed MgO increased with the enhancement of PEG-6000,the appropriate dosage was 10%.The addition of wetting agent also improved the strength of formed MgO,and the formed MgO had higher strength with increasing the holding time of pressure,and the pretreatment of MgO powder before compression forming could improve the strength of formed MgO.4.A series of saccharides modified Ba-MgO supports and Ru/Ba-MgO catalysts were prepared by UEA method.The results showed:the adding of saccharides changed the surface morphology of supports,especially with glucose.When the concentration of glucose was 3 mmol/L,MgO nanoparticles became cube.Also the doping amount of Ba in the Ba-MgO supports could be controlled by modification of glucose.When the concentration of glucose was 1 mmol/L,the outlet ammonia concentration of catalyst reached 17.17%at 10 MPa,400?,10 000 h-1.