Patent EP-2599770-A1 (EP)
Inventor: KINTRUP JUERGEN
IPC: C07C263/10
Filed: 2012-11-29
Abstract: Producing isocyanates, comprises e.g. (a) reacting a stream containing a primary amine with a phosgene-containing stream to obtain a product stream comprising isocyanates, hydrogen chloride, unreacted phosgene and carbon oxides, (b) separating the product stream into a liquid and gaseous product stream, (c) mixing the liquid product stream with a gaseous product stream to form a gaseous mixed stream, and (d) oxidizing the gaseous mixed stream in presence of a catalyst to form a gaseous product stream comprising hydrogen chloride, carbon dioxide, excess oxygen, chlorine and water. Producing isocyanates, comprises (a) reacting a stream (E1) containing a primary amine with a phosgene-containing stream to obtain a product stream (P1) comprising isocyanates, hydrogen chloride, unreacted phosgene and carbon oxides, (b) separating the product stream into a liquid product stream (P2) comprising isocyanates, and a gaseous product stream (P3) comprising hydrogen chloride, unreacted phosgene and carbon oxides, (c) mixing the product stream (P3) comprising hydrogen chloride, unreacted phosgene and carbon oxides with a gaseous product stream (P4) comprising oxygen to form a gaseous mixed stream (P5), (d) oxidizing the gaseous mixed stream (P5) in presence of a catalyst to form a gaseous product stream (P6) comprising hydrogen chloride, carbon dioxide, excess oxygen, chlorine and water, (e) partly to fully separating hydrogen chloride and water from the (P6) as hydrochloric acid-containing stream (P7) to form a product stream (P8) depleted of hydrochloric acid and water, (f) separating the product stream (P8) in to a liquid chlorine-rich product stream (P9) comprising chlorine, carbon dioxide and oxygen, and in to a gaseous chlorine-poor product stream (P10) comprising the residual amount of chlorine not-contained in (P9) from (P8), carbon dioxide and oxygen, (g) dividing the gaseous product stream (P10) into a gaseous purge-stream (P11) and into a gaseous product stream (P12), (h) treating the purge-stream (P11) with an aqueous base to form a gaseous purge-stream (P13) and a liquid wastewater stream (P14), (i) mixing the gaseous stream (P12) with a gaseous stream (E4) comprising oxygen to form the gaseous product stream (P4) comprising oxygen, which is used in the step (c), (j) evaporating the liquid chlorine-rich product stream (P9), mixing the resulting gaseous chlorine-rich product stream with carbon monoxide and chlorine, and converting the resulting mixture into a gaseous product stream (P15) comprising phosgene and carbon oxides, and (k) separating the gaseous product stream (P15) in a separating device into a phosgene rich product stream (P16), which is used in the step (a) comprising phosgene and carbon oxides, and into a phosgene poor purge-stream (P17) comprising the residual amount of the phosgene not included in the (P16) from (P15) and carbon oxides, where the separation of (P8) into (P9) and (P10) in the step (d) is carried out by cooling the (P8) at a temperature of -10[deg] C to -80[deg] C under an absolute pressure of 1-30 bar without subsequent distillation.