Abstract: The present invention provides a method for operating a rectification column (1000) for separating a mixture (S) containing a component A and a component B having a boiling point higher than that of the component A at an operating pressure of the rectification column (1000) which is lower than ambient pressure, wherein the method comprises a step for controlling the mass fraction of the component B in the product stream of the component A (P1) to a value within a first target range from 0.1% to 5.0% and the mass fraction of the component A in the product stream of the component B (P2) to a value within a second target range from 0.1% to 5.0%, wherein the control is carried out as a function of a controlling temperature (TC) for which a setpoint TCsetpoint is calculated according to the equation TCsetpoint=T2+F·(T1?T2), where F is a factor which is in the range from 0.1 to 0.

Abstract: The invention relates to a method for cleaning a phosgene-conducting apparatus by pressurization with ammonia gas to constant pressure. In this way, phosgene residues in the apparatus to be cleaned are decomposed effectively.

Abstract: A process for quenching, in a quenching zone, a gaseous reaction mixture that includes a diisocyanate, phosgene and hydrogen chloride that is obtained in a reaction zone upstream of the quenching zone by phosgenation of a diamine in the gas phase. The process includes injecting a deposit preventing liquid in a deposit preventing zone located between the reaction zone and the quenching zone by passing the deposit preventing liquid through spray nozzles for the deposit preventing liquid at the entrance to the deposit preventing zone. Each spray nozzle for the deposit preventing liquid sprays the deposit preventing liquid (i) onto a wall segment of the deposit preventing zone that is adjacent to said spray nozzle for the deposit preventing liquid to produce a film of the deposit preventing liquid flowing along the wall, and/or (ii) to areas in a cross-sectional plane of the deposit preventing zone before the entrance to the quenching zone.

Abstract: The present invention provides a process for quenching, in a quenching zone, a gaseous reaction mixture comprising a diisocyanate, phosgene and hydrogen chloride that is obtained in a reaction zone upstream of the quenching zone by phosgenation of a diamine in the gas phase, the process comprising injecting a deposit preventing liquid in a deposit preventing zone located between the reaction zone and the quenching zone by passing the deposit preventing liquid through spray nozzles for the deposit preventing liquid at the entrance to the deposit preventing zone, wherein each spray nozzle for the deposit preventing liquid sprays the deposit preventing liquid (i) onto a wall segment of the deposit preventing zone that is adjacent to said spray nozzle for the deposit preventing liquid to produce a film of the deposit preventing liquid flowing along the wall, and/or (ii) to areas in a cross-sectional plane of the deposit preventing zone before the entrance to the quenching zone.

Abstract: The invention relates to a method for cleaning a phosgene-conducting apparatus by pressurization with ammonia gas to constant pressure. In this way, phosgene residues in the apparatus to be cleaned are decomposed effectively.