Cobalt Catalyst Doped with Cerium and Barium Obtained by Co-Precipitation Method for Ammonia Synthesis Process
- PDF / 322,181 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 101 Downloads / 186 Views
Cobalt Catalyst Doped with Cerium and Barium Obtained by Co-Precipitation Method for Ammonia Synthesis Process Wioletta Raro´g-Pilecka • Magdalena Karolewska El_zbieta Truszkiewicz • Ewa Iwanek • Bogusław Mierzwa
•
Received: 18 January 2011 / Accepted: 10 February 2011 / Published online: 26 February 2011 Ó Springer Science+Business Media, LLC 2011
Abstract 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
W. Raro´g-Pilecka (&) M. Karolewska E. Truszkiewicz E. Iwanek Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland e-mail: [email protected] M. Karolewska e-mail: [email protected] E. Truszkiewicz e-mail: [email protected] E. Iwanek e-mail: [email protected] B. Mierzwa Institute of Physical Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland e-mail: [email protected]
123
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. Keywords Ammonia synthesis Cobalt catalyst Barium and cerium promoters Co-precipitation method
1 Introduction Atomic nitrogen is essential for the proper functioning of plant and animal cells. The commercial source of activated nitrogen is ammonia, which is also a significant substrate implemented in production of artificial fertilizers and medicine. Moreover, ammonia is used to obtain paint, explosives and resins. Therefore, research regarding ammonia synthesis, i.e., the reaction itself or new catalytic systems, is of fundamental importance for chemistry [1]. The iron-based catalyst is the first-generation ammonia synthesis catalyst and has been used in the industry for nearly 100 years [1, 2]. The second-generation catalysts are Ru-based catalysts, which have been applied in ammonia synthesis plants for m
Data Loading...
