Activated carbon as a template for creating catalyst precursors.: Unsupported cobalt catalyst for ammonia synthesis

Unsupported cobalt catalysts promoted with barium (symbol Co + Ba), cerium (Co + Ce) or both (Co + Cc + Ba) were synthesized and tested in ammonia synthesis at 63 bar. The Ba-free Co and Co+Ce oxide forms of the catalysts were prepared by the templating route, using commercial activated carbon (GF45; Norit) preheated in hydrogen (800 degrees C) as the template and cobalt and cerium nitrates as the active phase precursor and the promoter precursor, respectively. Barium was introduced to the Co and Co + Ce powders by their impregnation with an aqueous solution of barium nitrite. The kinetic studies of NH3 synthesis have demonstrated that the doubly-promoted material (Co + Ce + Ba) is about 2.5 times more active than the system doped with barium and about 20 times as active as that with Ce. At 400 degrees C and at high conversion (8%) NH3), the ammonia synthesis rate over Co + Ce + Ba proved to be almost twice as high as that obtained for the commercial iron catalyst (KM I, H. Topsoe) used commonly in ammonia plants all over the world. (c) 2007 Elsevier B.V. All rights reserved.