Abstract: The present invention relates to a process for producing isocyanates in process chains, each of which produce an isocyanate end product via at least one intermediate product, wherein the heat energy liberated in a first production plant in a heat-emitting operation of producing an intermediate product, an isocyanate end product or a catalyst required for a substep of the process chain (first chemical product) is at least partly utilized for generating vapour, in particular water vapour, having a pressure of 1.31 bar(abs.) to 1.91 bar(abs.) and a temperature of 107° C. to 119° C. and the thus generated vapour is employed for performing a heat-consuming operation in the preparation of another chemical product (second chemical product) in a second production plant.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series, by condensing aniline and formaldehyde followed by an acid-catalysed rearrangement at different production capacities. By adapting the temperatures in the acid-catalysed rearrangement step, the rearrangement reaction can be fully completed despite the change in dwell time inevitably associated with changed production capacity, with no undesired changes occurring in the product composition.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series, by condensing aniline and formaldehyde followed by an acid-catalysed rearrangement at different production capacities with alteration of the isomer composition in the resulting diamines of the diphenylmethane series (altering the 2,4?-MDA content). Adapting the molar ratios of the total used aniline to the total used formaldehyde and of the total used acid catalyst to the total used aniline, and adapting the reaction temperature, allows the rearrangement reaction to be fully completed despite the change in dwell time inevitably associated with a change in production capacity, and allows the formation of undesired by-products to be avoided as far as possible; the intended modification to binuclear content is likewise achieved.

Abstract: 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.

Abstract: The invention relates to a method for continuous production of nitrobenzene by means of nitration of benzene with nitric acid and sulfuric acid, in which load change (i.e. a reduction or increase in the quantity of nitric acid supplied to the process per time interval) is particularly advantageously developed. The invention particularly relates to a method in which, in the case of a load reduction, the ratio of the masses of benzene and nitric acid supplied per time interval is significantly increased compared to said ratio before the load change and/or the ratio of the masses of nitric acid and sulfuric acid supplied per time interval is significantly reduced compared to said ratio before the load change. In the event of a load increase, the reverse is carried out.

Abstract: This invention relates to methods for producing chemical products, wherein the one or more feed materials are reacted to form a chemical product or a chemical composition. The invention further relates to plants for performing such methods, said plants being designed in such a way that, during an interruption of the methods, no input of at least one feed material into the reaction occurs and the plant parts not affected by a revision measure, maintenance measure, repair measure, or cleaning measure are operated in so-called re-circulation mode. It is thereby achieved, among other things, that only the affected plant part needs to be shut down for the time of the measure, which can be advantageous with regard to the productivity and economy of the method and the quality of the produced products. Finally, the invention relates to methods for operating plants in the event that individual plant parts are taken out of service.

Abstract: 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.

Abstract: 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 vapour, 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.

Abstract: The present invention relates to a process for producing isocyanates in process chains, each of which produce an isocyanate end product via at least one intermediate product, wherein the heat energy liberated in a first production plant in a heat-emitting operation of producing an intermediate product, an isocyanate end product or a catalyst required for a substep of the process chain (first chemical product) is at least partly utilized for generating vapour, in particular water vapour, having a pressure of 1.31 bar(abs.) to 1.91 bar(abs.) and a temperature of 107° C. to 119° C. and the thus generated vapour is employed for performing a heat-consuming operation in the preparation of another chemical product (second chemical product) in a second production plant.

Abstract: 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.

Abstract: The invention relates to a method for the preparation of di- and polyamines of the diphenylmethane series, care being taken during the shutdown of the production process that an excess of aniline and respect to formalin is ensured.

Abstract: The present invention relates to a process for the continuous production of nitrobenzene by the nitration of benzene with nitric acid and sulphuric acid under adiabatic conditions, not the entire production plant being shut down during a production stop, but the production plant being entirely or at least partly operated in recirculation mode. The invention further relates to a plant for producing nitrobenzene and to a method for operating a plant for producing nitrobenzene.

Abstract: The invention relates to a method for the preparation of di- and polyamines of the diphenylmethane series (MDA) from aniline and formaldehyde, care being taken during the start up that a sufficient excess of aniline with respect to formaldehyde is ensured, said excess amounting to at least 105% of the desired molar ratio of aniline to formaldehyde for the target recipe of the MDA to be produced.

Abstract: The invention relates to a method for the preparation of di- and polyamines of the diphenylmethane series, care being taken during the shutdown of the production process that an excess of aniline and respect to formalin is ensured.

Abstract: The present invention relates to a device for separating two immiscible phases and/or for extracting one phase with another phase (phase separation or extraction device), comprising at least one vessel for receiving the at least two phases, at least one pipe for supplying a fluid to the vessel, at least one pipe for discharging a fluid from the vessel, and at least one arrangement comprising a transparent disk for observing the separation operation or the extraction operation, wherein at least the side of the transparent disk that faces the phases to be separated or extracted consists of sapphire (sapphire glass) or mica (mica disk), and to the use of such a device in the preparation of di- and poly-amines of the diphenylmethane series.

Abstract: 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.

Abstract: 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.

Abstract: The present invention relates to a process for the continuous production of nitrobenzene by the nitration of benzene with nitric acid and sulphuric acid under adiabatic conditions, not the entire production plant being shut down during a production stop, but the production plant being entirely or at least partly operated in recirculation mode. The invention further relates to a plant for producing nitrobenzene and to a method for operating a plant for producing nitrobenzene.

Abstract: The invention relates to a method for producing dinitrotoluene, comprising the following steps: a) nitrating toluene with a mixture of nitric acid and sulfuric acid and subsequently separating a sulfuric-acid-containing aqueous phase that arises in the nitration, wherein a raw dinitrotoluene is obtained, b) washing the raw dinitrotoluene in a water wash with neutral and/or alkaline washing water, wherein a pre-cleaned dinitrotoluene, which contains at least water in addition to dinitrotoluene, is obtained after the washing water used in the last wash has been separated, and c) separating the water from the pre-cleaned dinitrotoluene, d) collecting the waste water from steps a), b), and/or c), e) optionally extracting the collected waste water from step d) with toluene and returning the thus obtained organic phase to step a), f) freeing the collected waste water from step d), or, if the optional step e) is performed, the extracted waste water from step e), of toluene in a toluene stripper, wherein a toluene-co

Abstract: This invention relates to a process for operating a gas phase phosgenation plant (100) to form an isocyanate (4) by reacting an amine (2) with phosgene (1), 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 (1) in the main parts of the gas phase phosgenation plant (100) 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 (3) is maintained through the amine and phosgene feeding devices and through all the other essential parts of the gas phase phosgenation plant (100) during the shutdown.