Covestro Deutschland Ag

Covestro Intellectual Property Gmbh & Co. Kg

Wolfgang Taube

Rainer Bruns

Thomas Knauf

Friedhelm Steffens

Wolfgang Lorenz

Zhangyong Ming

Yuguo Gai

Volker Michele

Joachim Zechlin

Qiang Wei

Thomas Bludowsky

Yiming Mao

Artur Mausbach

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.

Method for cleaning phosgene-conducting apparatuses

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.

Process for quenching a gaseous reaction mixture obtained in the gas phase phosgenation of diamines

The invention relates to a method for preparing an isocyanate by phosgenating the corresponding primary amine in the gas phase, wherein the gaseous reaction product mixture is cooled by being brought into contact with at least one flow stream of a quenching liquid in a quenching zone, wherein the quenching liquid used in total comprises, based on the total mass, organic solvents in a proportion of maximally 50.0% by mass, and the remainder of up to 100% by mass consists of at least the isocyanate to be produced, thereby obtaining a mixture of the reaction product mixture and the quenching liquid. Furthermore, the mixture obtained in this manner of the reaction product mixture and the quenching liquid is separated into a liquid and a gaseous phase in a collection zone, and a liquid solvent intermediate flow comprising more than 50.0% by mass of organic solvents, based on the total mass of the liquid solvent intermediate flow, is conducted into the collecting zone and/or into a collecting tank arranged fluidically downstream of the collection zone for the liquid phase obtained in the collection zone.

Method for producing isocyanates

This invention relates to a process for operating a gas phase phosgenation plant () to form an isocyanate () by reacting an amine () with phosgene (), in which the gas phase phosgenation plant is shut down by first stopping the amine stream and still maintaining the phosgene stream. After a period of time which corresponds to at least 10 times the residence time of phosgene () in the main parts of the gas phase phosgenation plant () in regular operation, calculated from the time at which the amine inflow has been completely stopped, the feed of phosgene is also stopped. An inert gas stream () is maintained through the amine and phosgene feeding devices and through all the other essential parts of the gas phase phosgenation plant () during the shutdown.

Process for operating a gas phase phosgenation plant

This invention relates to a process for operating a gas phase phosgenation plant () to form an isocyanate () by reacting an amine () with phosgene (), in which the gas phase phosgenation plant is started up by first charging the plant with phosgene. At the same time as, or after the first charge of phosgene, the amine supply devices are rendered inert using a hot inert gas stream (). Then, amine is admixed for the first time. In this way and by maintaining a pressure drop in the amine and phosgene devices to the mixing zone, the back mixing of phosgene into the amine-containing reactant stream during start-up is prevented.

Method for operating a gas-phase phosgenation plant

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Neuss, Germany

Wolfgang Taube