Effect Of Carbon Support And Barium Promoter On Ruthenium-Based Catalyst For Ammonia Synthesis

Carbon-supported ruthenium catalyst is known as the second-generation catalyst for ammonia synthesis due to its high activity at low temperature and low pressure.The interaction of ruthenium nanoparticles with carbon supports and promoters can significantly affect the performance of ammonia synthesis for ruthenium catalysts.In this paper,the surface structure of carbon supports was regulated by introducing heteroatomic functional groups and thermal treatment.The effect of surface structure of carbon supports and the Ba promoter on the performance of carbon-supported ruthenium catalyst in ammonia synthesis were investigated.Major conclusions in this article are listed below:?1?Defect-rich carbon nanotubes?CNTs-D?were prepared by a liquid oxidation and thermal treatment method.The effect of surface defect of carbon nanotubes on the Ru nanoparticles and properties of ammonia synthesis was studied.The surface defect of carbon nanotubes can not only stabilize the Ru nanoparticles,but also significantly improve the activity of Ba-Ru/CNTs-D in ammonia synthesis.The turnover frequency?TOF?of Ba-Ru/CNTs-D was 0.30 s^-1 at 450 ^oC,10 MPa and 10000 h^-1.?2?More defects were introduced into the surface of activated carbon by thermal treatment method with Ba?NO₃?₂ at high temperature,and barium promoters were loaded in this process.The surface defects of activated carbon can not only stabilize Ru nanoparticles,but also enhance the electron donating ability of barium promoters and the interaction between Ba and carbon supports,thereby improving the activity of ammonia synthesis.The TOF value of Ru/?8Ba-AC?-T was twice as high as that of8Ba-Ru/AC.?3?The effects of nitrogen co-doping with ruthenium on the structure and catalytic performance of Ru-N-MC were investigated.The co-doping of ruthenium and nitrogen in Ru-N-MC can not only enhance the electron cloud density on the surface of Ru and promote the dissociation of N₂,but also have a strong interaction between Ru and carbon supports.The TOF value of Ba/Ru-N-MC was 0.16 s^-1 at 400^oC,10 MPa and 10000 h^-1.?4?The interaction between Ba promoter and Ru in Ba/Ru-MC was studied.The Ba promoter can not only provide electrons to the surface of the metal Ru as an electronic promoter,but also can be used as structural promoter to form heterojunctions with Ru nanoparticles.The heat treatment of Ba/Ru-MC can enhance the interaction between barium promoter and Ru nanoparticles,and the TOF value of?Ba/Ru-MC?-600 was found to be doubled compared to Ba/Ru-MC.