| abstract |
Process for preparing organic isocyanates, which comprises the steps n (a) making available a first partial amount of chlorine, with the chlorine of this first partial amount having a content of free and bound bromine and iodine of <400 ppm; n (b) making available a second partial amount of chlorine; n (c) reacting the first and second partial amounts of chlorine with carbon monoxide to form phosgene; n (d) reacting the phosgene from step (c) with one or more primary amines to form the corresponding isocyanates and hydrogen chloride; n (e) separating off and, if necessary, purifying the isocyanates formed in step (d); n (f) separating off and, if necessary, purifying the hydrogen chloride formed in step (d); n (g) catalytically oxidizing at least part of the hydrogen chloride separated off in step (e) by means of oxygen to form chlorine; n (h) separating off the chlorine formed in step (g) and using at least a partial amount of the chlorine which has been separated off as second partial amount of chlorine in step (b). |