| 摘要 |
<p>Preparing chlorine comprises subjecting a hydrogen chloride stream having a sulfur content of less than 100 ppm, based on weight of the hydrogen chloride stream, to catalytic oxidation. An independent claim is included for preparing an isocyanate by phosgenation of an amine comprising: (a) reacting carbon monoxide with chlorine to form phosgene, (b) reacting an amine with phosgene to form, a crude isocyanate mixture and a gas stream containing hydrogen chloride, (c) distilling the crude isocyanate mixture to purify the mixture and obtain the isocyanate and a mixture containing isocyanate and non-vaporizable residue (10-70 wt.%), based on the weight of the mixture, (d) working up the mixture of isocyanate and non-vaporizable residue obtained in (c) to recover isocyanate by evaporation in a kneader dryer or in residue pans or the amine by hydrolysis of the residue, and recycling at least a portion of the isocyanate obtained or of the amine obtained to the reaction in (b), and (e) subjecting the gas stream containing hydrogen chloride with a content of sulfur in elemental or bonded form at less than 100 ppm, based on weight of the gas stream, obtained in (b) to catalytic oxidation to produce chlorine, and (f) recycling at least a portion of the chlorine prepared in (e) to the preparation of phosgene in (a).</p> |
