| 摘要 |
<p>Melamine is prepared by heating urea and/or a thermal decomposition product thereof (e.g. biuret, isocyanic acid or cyanuric acid) at a pressure not exceeding 2 atmospheres and at a temperature of at least 220 DEG C., in the presence of ammonia and of boron phosphate and/or aluminium phosphate. The ammonia may be used to maintain a fluidized bed of catalyst, the gases emergent therefrom being subsequently passed to a fixed bed of catalyst. Specifications 767,344, 825,729 and 910,197 are referred to.</p> |
