THERMALLY MODIFIED ACTIVE-CARBON AS A SUPPORT FOR CATALYSTS FOR NH3 SYNTHESIS

The effect of thermal treatment of a typical active carbon at 1300 deg rees C and 1900 degrees C on its structural properties was investigate d. It has been found that only a high-temperature heating (1900 degree s C) produced substantial changes in the structure of the carbon used: a disappearance of a considerable part of open micropores and formati on of a turbostratic structure. The prepared materials were used as a support in catalysts for NH3 synthesis. The precursor of the active ph ase was Fe(NO3)(3) . 9H(2)O. The iron nitrate deposited on the raw amo rphous carbon decomposes to finely dispersed, hardly reducible iron ox ides on heating to 470 degrees C in a H-2+N-2 mixture. Even if reduced to more than 33%, iron is inactive in NH3 synthesis (400-470 degrees C, p=10 MPa). When deposited on the turbostratic, low-surface area car bon, iron forms, however, well developed crystallites (similar to 60 n m), and is active in ammonia synthesis. Potassium activates strongly t he surface of Fe, and, in the case of the amorphous support, it stimul ates the reduction of iron oxides.