Abstract: The invention relates to a method for producing di- and polyisocyanates of the diphenylmethane series, in which (i) the liquid product flow created in the phosgenation, (ii) the reaction mixture present in an optionally provided reactor for carbamic acid chloride cleaving, (ii) the liquid product flow leaving such an optionally provided reactor for carbamic acid chloride cleaving, (iv) the reaction mixture present in the dephosgenation, or (v) the liquid product flow created in the dephosgenation, is treated with a gaseous hydrogen chloride flow in one stage in a bubble column or in a plate column within a contact time of 1 min to less than 30 min. The product flow treated din this way or in the reaction mixture treated in this way is fed directly (i.e. in particular without further treatment with an inert gas) to the next step of the reaction or workup.

Abstract: The present invention relates to a process for preparing di- and polyamines of the diphenyl methane series. More specifically, the process comprises reacting aniline and formaldehyde by (1a) mixing aniline with hydrochloric acid to form aniline hydrochloride, and (1b) mixing the aniline hydrochloride with a first portion of aqueous formaldehyde; or (1c) mixing aniline with a first portion of aqueous formaldehyde to form an aminal, and (1d) mixing the aminal with hydrochloric acid; to obtain a first reaction product; (2) converting the first reaction product to a second reaction product comprising di- and polyamines of the diphenyl methane series in a cascade of 4 to 25 reaction zones arranged in series, wherein a second portion of aqueous formaldehyde is added to the second of the reaction zones, in which second reaction zone the temperature is equal to or up to 20° C.

Abstract: The invention relates to a process for the preparation of di- and polyamines of the diphenylmethane series (MDA), in which firstly crude MDA is prepared and is then subjected to a distillation process, wherein the distillation process comprises the following: in a distillation column, separating off a stream containing aniline and water as head product so as to obtain the first product stream as sump product, in said distillation column or in an apparatus arranged downstream of said distillation column, performing a stripping with steam so as to obtain a gaseous stream containing aniline, water and MMDA, partially condensing this gaseous stream containing aniline, water and MMDA so as to obtain a liquid stream containing MMDA and water (and optionally aniline) and a gaseous stream containing aniline and water (and optionally MMDA), drying the liquid stream containing MMDA and water (and optionally aniline) obtained by the partial condensation so as to obtain the second product stream.

Abstract: The invention relates to a process for the preparation of di- and polyamines of the diphenylmethane series (MDA), in which firstly crude MDA is prepared and is then subjected to a distillation process, wherein the distillation process comprises the following: in a distillation column, separating off a stream containing aniline and water as head product so as to obtain the first product stream as sump product, in said distillation column or in an apparatus arranged downstream of said distillation column, performing a stripping with steam so as to obtain a gaseous stream containing aniline, water and MMDA, partially condensing this gaseous stream containing aniline, water and MMDA so as to obtain a liquid stream containing MMDA and water (and optionally aniline) and a gaseous stream containing aniline and water (and optionally MMDA), drying the liquid stream containing MMDA and water (and optionally aniline) obtained by the partial condensation so as to obtain the second product stream.

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 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 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 present invention relates to a process for producing diamines and polyamines of the diphenylmethane series (MDA) by reacting aniline and formaldehyde in the presence of an acid catalyst, wherein the aniline contains in total less than 0.5 wt. %, based on the total weight of aniline, of one or more compounds which contain at least one carbonyl group or of one or more compounds that are formed by reaction of these compounds which contain at least one carbonyl group with aniline.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series in which, by using a coalescence auxiliary in the phase separation of the process product obtained in the scrubbing of the neutralized crude product, the fraction of water and thus also of water-soluble impurities in the organic MDA-containing phase is reduced. According to the invention, the coalescence auxiliary used is a filter bed made of coalescence fiber material. The di- and polyamines of the diphenylmethane series obtained after distillative purification of this MDA-containing organic phase are exceptionally suitable for the preparation of the corresponding isocyanates.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series, wherein first aniline and formaldehyde are reacted in the absence of an acidic catalyst to form a reaction mixture containing animal and water and, after the water has been separated the aminal is reacted by acid catalysis to form a reaction mixture containing diamines and polyamines of the diphenylmethane series, wherein the separation of the water from the aminal is supported by the use of a coalescence aid. According to the invention, a filter bed made front coalescence fiber material is used an coalescence aid.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series, wherein first aniline and formaldehyde are reacted in the absence of an acidic catalyst to form a reaction mixture containing aminal and water and, after the water has been separated, the aminal is reacted by acid catalysis to form a reaction mixture containing diamines and polyamines of the dephenylmethane series, wherein the separation of the water and aminal is supported by the use of a coalescence aid. According to the invention, a filter bed made of coalescence fiber material is used as coalescence aid.

Abstract: The invention relates to a method for producing diamines and polyamines of the diphenylmethane series, wherein first aniline and formaldehyde are reacted in the absence of an acidic catalyst to form a reaction mixture containing aminal and water and, after the water has been separated the aminal is reacted by acid catalysis to form a reaction mixture containing diamines and polyamines of the diphenylmethane series, wherein the separation of the water from the aminal is supported by the use of a coalescence aid. According to the invention, a filter bed made from coalescence fiber material is used an coalescence aid.

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 polyamines of the diphenylmethane series.

Abstract: The invention relates to a process for preparing methylenediphenyl diisocyanates which comprises at least the steps: A) reaction of aniline with formaldehyde in the presence of hydrochloric acid as catalyst to give a mixture of diamines and polyamines of the diphenylmethane series (MDA) and subsequent at least partial neutralization of the hydrochloric acid by means of alkali metal hydroxide, B) reaction of the mixture of diamines and polyamines of the diphenylmethane series obtained in step A) with phosgene to give a mixture of diisocyanates and polyisocyanates of the diphenylmethane series (MDI) and hydrogen chloride, wherein C) the hydrochloric acid which has been neutralized in step A) is separated off in the form of a solution containing alkali metal chloride and is subsequently at least partly fed to an electrochemical oxidation to form chlorine, alkali metal hydroxide and optionally hydrogen and D) at least part of the chlorine produced in step C) is used for preparing the phosgene used in step B).

Abstract: The present invention relates to a process for the preparation of isocyanates by reacting the appropriate amines with phosgene, condensing the gas mixture thereby obtained, stripping the liquid phase thereby obtained and returning the solvent so retained in liquid form to the reaction stage. The gaseous constituents are then purified further in an absorption process.

Abstract: The present invention relates to a process for producing diamines and polyamines of the diphenylmethane series (MDA) by reacting aniline and formaldehyde in the presence of an acid catalyst, wherein the aniline contains in total less than 0.5 wt. %, based on the total weight of aniline, of one or more compounds which contain at least one carbonyl group or of one or more compounds that are formed by reaction of these compounds which contain at least one carbonyl group with aniline.

Abstract: The invention relates to a process for preparing methylenediphenyl diisocyanates which comprises at least the steps: A) reaction of aniline with formaldehyde in the presence of hydrochloric acid as catalyst to give a mixture of diamines and polyamines of the diphenylmethane series (MDA) and subsequent at least partial neutralization of the hydrochloric acid by means of alkali metal hydroxide, B) reaction of the mixture of diamines and polyamines of the diphenylmethane series obtained in step A) with phosgene to give a mixture of diisocyanates and polyisocyanates of the diphenylmethane series (MDI) and hydrogen chloride, wherein C) the hydrochloric acid which has been neutralized in step A) is separated off in the form of a solution containing alkali metal chloride and is subsequently at least partly fed to an electrochemical oxidation to form chlorine, alkali metal hydroxide and optionally hydrogen and D) at least part of the chlorine produced in step C) is used for preparing the phosgene used in step B).

Abstract: The present invention relates to a process for the preparation of isocyanates by reacting the appropriate amines with phosgene, condensing the gas mixture thereby obtained, stripping the liquid phase thereby obtained and returning the solvent so retained in liquid form to the reaction stage. The gaseous constituents are then purified further in an absorption process.

Abstract: The invention provides an improved process for preparing diamines and polyamines from the diphenylmethane series by reacting aniline and formaldehyde in the presence of an acid catalyst, the improvement involving the aniline containing less than about 3 wt. % of diamines and polyamines from the diphenylmethane series, based on the weight of the aniline.

Abstract: The present invention relates to a process for the production of mixtures of di- and polyamines of the diphenylmethane series (MDA) containing less than 1,000 ppm of water and less than 200 ppm of aniline by reaction of aniline and formaldehyde in the presence of acid catalysts and subsequent separation of the acid catalyst and subsequent distillative separation of water and aniline in an at least a two-stage distillation including a flash evaporation and subsequent cooling.