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 + Ce + 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 °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 °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.