| 摘要 |
1,145,777. Alkali metal cyanates. E. I. DU PONT DE NEMOURS & CO. 28 July, 1967 [1 Aug., 1966], No. 34919/67. Heading C1A. Alkali metal cyanates of high purity (98% or more) and having a cyanide content of less than 1 p.p.m. are prepared by heating an alkali metal carbonate and urea in the presence of a heel of the cyanate to be produced which is at least 90%, preferably at least 95% pure and which constitutes at least 35% by weight of the reaction mixture. When preparing sodium cyanate the heel preferably constitutes 45% of the mixture whilst for the production of potassium cyanate it should constitute 55% thereof. The mixture is heated, preferably whilst being subjected to an "intensive rubbing, smearing and mixing action" to a temperature in the range 80‹ to 225‹ C. until the evolution of vapours ceases, this normally requiring 4 to 7 hours. The reaction may be carried out either as a batch process or a continuous process, e.g. in a screw conveyer using a portion of recycled product as heel or operating several batch reactions in cascade. |
