Cobalt Catalyst Doped with Cerium and Barium Obtained by Co-Precipitation Method for Ammonia Synthesis Process
Wioletta Raróg-Pilecka , Magdalena Karolewska , Elżbieta Truszkiewicz , Ewa Iwanek , Bogusław Mierzwa
AbstractAbstract Unsupported cobalt catalysts promoted with barium (symbol Co/Ba), cerium (Co/Ce) or both (Co/Ce/Ba) were synthesized and tested in ammonia synthesis at 6.3 MPa. The Ba-free Co and Co/Ce oxide forms of the catalysts were prepared by precipitation/co-precipitation and a subsequent calcination at 500 °C. The Co and Co/Ce powders were impregnated with an aqueous solution of barium nitrite. Nitrogen physisorption and H2 chemisorption measurements revealed that cerium and barium play the role of structural promoters, which hinder the sintering of cobalt oxide during calcination and stabilize the surface of cobalt under reduction conditions. It seems that barium also modifies the surface of the active phase, i.e., cobalt. The kinetic studies of NH3 synthesis have shown that the co-promoted material (Co/Ce/Ba) is about 2–3 times more active than the system doped with barium (Co/Ba) and more than ten times as active as that with Ce. At 400 °C and at low conversion (1\% NH3), the ammonia synthesis rate (TOF) over Co/Ce/Ba proved to be almost 60\% as high as that obtained for the commercial iron catalyst (KMI, H. Topsøe) commonly used in ammonia plants all over the world. Moreover, at the same temperature and a high ammonia concentration (8\%) the co-promoted cobalt catalyst is over two times more active than the fused iron catalyst. Another asset of the cobalt catalyst is its high thermal stability. Graphical Abstract TG/DTG-MS studies of the cobalt catalysts. DTG curves of samples
|Journal series||Catalysis Letters, ISSN 1011-372X, 1572-879X, (0 pkt)|
|Keywords in English||Ammonia synthesis, Barium and cerium promoters, Catalysis, Cobalt catalyst, Co-precipitation method, Industrial Chemistry/Chemical Engineering, Organometallic Chemistry, Physical Chemistry|
|Publication indicators||= 16; = 15|
|Citation count*||6 (2016-05-12)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.