Abstract: The invention relates to a method of measuring entry of water and resulting corrosion in plants for producing isocyanates by reacting phosgene with one or more primary amines in a solvent. The invention further relates to an apparatus for producing such isocyanates, in the work-up section of which probes for monitoring corrosion are arranged in defined places.

Abstract: A process is proposed for preparing isocyanates by phosgenating the corresponding amines in the gas phase, which comprises dividing a phosgene-containing reaction mixture from the gas phase synthesis of carbon monoxide and chlorine to phosgene, which is run with a stoichiometric carbon monoxide excess over chlorine, by means of a thermal separating process and/or of a membrane separating process into two streams, specifically into a first, low-carbon monoxide stream comprising not more than 1% by weight of carbon monoxide, based on the total weight of the first, low-carbon monoxide stream, and into a second, carbon monoxide-rich stream comprising more than 10% by weight of carbon monoxide, based on the total weight of the second, carbon monoxide-rich stream, and using the first, low-carbon monoxide stream as a reactant stream in the phosgenation of amines to isocyanates in the gas phase.

Abstract: This invention relates to a process for preparing chlorine from HCl and a method of using liquid HCl to cool and optionally liquefy chlorine in the process. The process involves introducing at least one HCl-containing stream and an oxygen-containing stream into an oxidation zone and catalytically oxidizing the HCl to chlorine, contacting the chlorine with aqueous HCl with partial separation of water and HCl to yield a gas stream, drying the gas stream to yield an essentially water-free gas stream, which is compressed and cooled to give an at least partially liquefied stream, and separating the liquefied stream into a gas stream and a liquid stream which is separated into a chlorine stream, such that cooling and partial liquefaction of the gas stream is effected by indirect heat exchange with a liquid HCl stream, resulting in some of the liquid HCl stream vaporizing to form a gaseous HCl stream.

Abstract: The invention relates to a process for separating chlorine from a gas stream I comprising oxygen and chlorine, in which the gas stream I is fed into a lower part of a column K1 and a separately provided liquid, hydrogen chloride stream II is fed into an upper part of the same column and the ascending gaseous stream I is brought into contact with the descending liquid stream II, with chlorine condensing out from the stream I and hydrogen chloride vaporizing from the stream II to give an essentially chlorine-free gas stream III comprising hydrogen chloride and oxygen and a liquid stream IV comprising chlorine.

Abstract: The present invention relates to a process for preparing light-coloured polyphenylene-polymethylene-polyisocyanate (PMDI), comprising the steps (a) providing carbon monoxide and chlorine, (b) reacting carbon monoxide with chlorine to form phosgene, (c) reacting the phosgene from step (b) with at least one primary amine with the exception of mono- and polyphenylene-polymethylene polyamines with an excess of phosgene to form an at least one isocyanate containing reaction solution, and hydrogen chloride, (d) separating excess phosgene from the isocyanate-containing reaction solution obtained in step (c), (e) providing at least one polyphenylene-polymethylene polyamine, and (f) reacting at least a portion of the phosgene separated in step (d) with the at least one polyphenylene-polymethylene polyamine to form the light-coloured polyphenylene-polymethylene polyisocyanate.

Abstract: A process for preparing diisocyanates by gas-phase phosgenation starting out from a feed stream comprising the corresponding diamines and a phosgene-comprising feed stream, in which the feed streams are separately converted into the gas phase and preheated to the reaction temperature of the gas-phase phosgenation, wherein the waste heat from a plant for preparing chlorine by heterogeneously catalyzed oxidation of hydrogen chloride by the Deacon process is utilized for this purpose, is proposed.

Abstract: The invention relates to a process for preparing methylenedi(phenyl isocyanate), which comprises (a) the phosgenation of two-ring and/or multiring methylenedi(phenylamine), (b) the fractionation of the crude methylenedi(phenyl isocyanate) obtained to give two-ring and multiring isomers, (c) the purification and/or fractionation of the resulting mixture of two-ring isomers of methylenedi(phenyl isocyanate) and (d) the storage of the mixtures obtained in step (c) or in step (b), wherein part of the stored mixtures is reused by means of recirculation in at least one of steps (b) or (c).

Abstract: The invention relates to a method of measuring entry of water and resulting corrosion in plants for producing isocyanates by reacting phosgene with one or more primary amines in a solvent. The invention further relates to an apparatus for producing such isocyanates, in the work-up section of which probes for monitoring corrosion are arranged in defined places.

Abstract: The present invention accordingly provides a process for preparing light-coloured polyphenylene-polymethylene polyisocyanates comprising the steps (a) providing an amount of chlorine, (b) separating the chlorine provided in the step (a) to obtain a first chlorine fraction having a content of free and bound bromine and iodine of <50 ppm and a second chlorine fraction having an increased content of free and bound bromine and iodine that depends on the original amount of bromine and iodine in the chlorine provided in step (a) and the separation split, (c) reacting carbon monoxide with at least a portion of the first chlorine fraction to form a first phosgene fraction, (d) reacting carbon monoxide with at least a part of the second chlorine fraction to form a second phosgene fraction, (e) reacting at least a portion of a first phosgene fraction with at least one amine of the diphenylmethane diamine series (MDA) to form the corresponding polyphenylene-polymethylene polyisocyanate (PMDI), and (f) reacting at lea

Abstract: The present invention relates to a process for the production of isocyanates, preferably diisocyanates and polyisocyanates of the diphenylmethane series (MDI), by reacting an amine with phosgene in the liquid phase or in the gas phase to form the corresponding isocyanates, subsequent removal of the solvent in at least two steps to obtain at least two solvent streams, individual treatment of the at least two solvent streams, and re-circulation of at least a portion of the solvent streams.

Abstract: The invention relates to a process for preparing methylenediphenyldiamine (MDA) by reacting formaldehyde and aniline in the presence of an acidic catalyst, wherein the oxygen content in the process for preparing MDA is <10 000 ppm, based on all compounds present in the process. The invention further relates to the phosgenation of MDA to methylenediphenyl diisocyanate (MDI).

Abstract: The invention relates to a process for the preparation of triamides from ammonia and amido-dichlorides.

Abstract: A process for preparing phosgene by reaction of a feed stream (1) obtained by combining and mixing a chlorine feed stream (2) and a carbon monoxide feed stream (3), with the carbon monoxide being introduced in a stoichiometric excess over chlorine, in catalyst tubes filled with beds of activated carbon in a reactor R having a bundle of catalyst tubes, to give a product gas mixture (4) which is separated into a liquid, phosgene-comprising product stream (5) and an offgas stream (6) comprising carbon monoxide which is discharged via a pressure-regulating valve, where the reaction of the feed stream (1) in the reactor R and the separation of the product gas mixture (4) are carried out under a pressure in the range from 2.0 to 6.

Abstract: The present invention relates to a process for preparing an isocyanate, comprising hydrogenating a mixture (Gi) comprising an amine in the presence of a hydrogenation catalyst comprising copper to obtain a mixture (Gii) comprising the amine, and reacting the mixture (Gii) with phosgene to obtain a mixture (Giii) comprising the isocyanate. The present invention further relates to the isocyanate preparable by this process.

Abstract: The invention relates to a process for preparing 4,4?-dichlorodiphenyl sulfone proceeding from monochlorobenzene, wherein the content in the monochlorobenzene used of hydrocarbons having from 5 to 8 carbon atoms is at most 100 ppm; based on the total weight of the monochlorobenzene used, including the secondary components. The present invention further relates to the use of monochlorobenzene with the properties mentioned for preparation of 4,4?-dichlorodiphenyl sulfone.

Abstract: The invention relates to a process for preparing 4,4?-dichlorodiphenyl sulfone, comprising the reaction of monochlorobenzene and liquid sulfur trioxide, wherein the liquid sulfur trioxide used has a boron content of at most 100 ppm based on the total weight of the sulfur trioxide used, including all secondary components.

Abstract: The invention relates to a process for preparing 4-chlorobenzenesulfonic acid from 2-chlorobenzenesulfonic acid and/or 3-chlorobenzenesulfonic acid, comprising the conversion of 2-chlorobenzenesulfonic acid and/or 3-chlorobenzenesulfonic acid to 4-chlorobenzenesulfonic acid in the presence of sulfuric acid at a temperature of 100 to 300° C. The present invention further relates to a process for preparing 4,4?-dichlorodiphenyl sulfone, comprising said process for preparing 4-chlorobenzenesulfonic acid.

Abstract: A process for preparing polyoxymethylene dialkyl ethers of the formula H2m+1CmO(CH2O)nCmH2m+1 where n=2-10, m, identically or differently,=1 or 2, in which a dialkyl ether selected from dimethyl ether, methyl ethyl ether and diethyl ether, and trioxane are fed into a reactor and reacted in the presence of an acidic catalyst, the amount of water introduced into the reaction mixture by the dialkyl ether, trioxane and/or the catalyst being <1% by weight based on the reaction mixture.

Abstract: The invention relates to a process for the preparation of triamides from ammonia and amido-dichlorides.

Abstract: (Chloro)hydrocarbon-free hydrogen chloride and phosgene-free (chloro)hydrocarbons are recovered from a hydrogen chloride stream having (chloro)hydrocarbons and phosgene.