Covestro Deutschland Ag

Covestro Intellectual Property Gmbh & Co. Kg

Dirk Manzel

Thomas Knauf

Peter Plathen

Stefan Wershofen

Jürgen Spriewald

Andreas Karl Rausch

Juergen Spriewald

Charles Bjoerndahl

Matthias Ehlers

Carlos Alvarez Herrero

Francisco Munoz Velasco

Peter Wolf

Udo Boegel

Charles BJÖRNDAHL

The invention relates to a method for operating a production plant for producing a chemical product () by reacting a H-functional reactant () with phosgene () during an interruption in production when taking at least one plant part of the production plant out of operation, wherein low-oxygen and oxygen-rich phosgene-containing exhaust gas flows are directed separately from one another in different phosgene decomposition directions and separately from one another&#x2014;at spatially different points&#x2014;into a combustion device, wherein plant parts that have not been taken out of operation are operated in a closed-circuit operating mode. The invention also relates to a production plant for producing a chemical product by reacting H-functional reactants with phosgene, which is suitable for being operated with the method according to the invention.

Production plant for producing a chemical product by reacting H-functional reactants with phosgene, and method for operating same with an interruption to production

The invention relates to a method for cleaning a phosgene conducting apparatus, comprising: washing the apparatus with hot inert gas, followed by washing the apparatus with cold inert gas; conveying gaseous ammonia for breaking down phosgene residues with a continuous increase in temperature until a maximum temperature ranging between 30&#xb0; C. to 120&#xb0; C. is reached; once the maximum temperature is reached, shutting down the ammonia supply and the conveying of inert gas, optionally followed by washing the apparatus with an aqueous stream.

Method for cleaning phosgene conducting apparatus

The invention relates to a method for producing methylene-diphenylene-diisocyanate and optionally a mixture of methylene-diphenylene-diisocyanate and polymethylene-polyphenylene-polyisocyanate, wherein, in a step &#x3b1;), a fraction () containing a methylene-diphenylene-diisocyanate and secondary components is provided, optionally via a step &#x3b1;.), the separating of methylene-diphenylene-diisocyanate and secondary components from a fraction () containing methylene-diphenylene-diisocyanate and polymethylene-polyphenylene-polyisocyanate, and wherein, in a step &#x3b2;), the fraction () containing methylene-diphenylene-diisocyanate and secondary components is subjected to a purification comprising an isomer separation by distillation and/or crystallization in two or more sub-steps (a, b, . . . ), obtaining two or more methylene-diphenylene-diisocyanate-reinfractions (--, . . . ) and a secondary component fraction (), wherein the secondary component fraction () obtained in step &#x3b2;) is returned to one of the sub-steps of step &#x3b2;), wherein none of the methylene-diphenylene-diisocyanate-reinfractions (--, . . . ) from step &#x3b2;) are obtained as distillation or crystallization, and/or to step &#x3b1;.), insofar as carried out.

Method for producing methylene-diphenylene-diisocyanates and polymethylene-polyphenylene-polyisocyanates

The invention relates to a method for an economically and technically improved embodiment of a production interruption in a production method for isocyanates by phosgenation of the corresponding amines, in which the entire production plant is not closed while one or more parts of the plant is taken out of operation, rather the input materials and/or reaction products available in the production plant are recirculated through at least one part of the plant that has not been taken out of operation. The invention further relates to a plant for producing isocyanates and to a method for operating a plant for producing isocyanates.

Method for producing isocyanates

The invention relates to a method for producing isocyanates, according to which exhaust flows provided for the combustion are guided through an adsorption device before being supplied into the exhaust gas combustion process, and are thereby depleted of solvent, the adsorption device comprising at least two adsorption units connected in parallel, which are alternately (i) exposed to the at least one exhaust flow and (ii) regenerated with water vapor, where, during method step (i), an exhaust flow depleted of solvent is obtained, and during method step (ii), a flow containing water and solvent is obtained, the solvent proportion of which is recycled into a method for producing isocyanates.

The invention relates to a continuously operated method for producing isocyanates by reacting the corresponding amines with phosgene. When changing the target production capacity starting from a starting state with a specified production capacity and ending with an end state with a different production capacity, the current excess phosgene at the time of the transition period between the starting state and the end state, the change of the amine mass flow beginning during said time, is at least equal to and preferably greater than the excess phosgene during the production period when the production capacity is in the starting state prior to the beginning of the transition period; and the average excess phosgene during the transition period is greater than the excess phosgene during the production period when the production capacity is in the starting state prior to the beginning of the transition period.

The present invention relates to a method for operating a phosgene generator for producing phosgene by reacting carbon monoxide with chlorine in the gas phase on an activated carbon catalyst arranged in a reaction chamber, in which method, after a predefinable operating period, the phosgene production is at least temporarily interrupted by shutting down the phosgene generator over a shutdown period and, after a predefinable downtime, is resumed by starting up the phosgene generator over a start-up period, wherein the method is characterized in that the activated carbon catalyst, before the phosgene generator is started up, is freed of chlorine by adding carbon monoxide so that, during the start-up period, a maximum concentration of chlorine in the gas stream immediately downstream of the reaction chamber of 1000 ppmv is not exceeded. The invention also relates to the use of the phosgene thus obtained in the production of polycarbonate and isocyanates.

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Moers, Germany

Dirk Manzel