Abstract: The invention relates to a process for preparing isocyanates by thermal dissociation of carbamates and separation by distillation of the reaction mixture from the carbamate dissociation, comprising the corresponding isocyanate and the corresponding alcohol, by distillation in a column (K) having an enrichment section (V) and a stripping section (A), where the carbamate (1) is introduced between the enrichment section (V) and the stripping section (A) and the isocyanate is taken off as a constituent of the bottom stream (2) and the alcohol is taken off as a constituent of the overhead stream (3) from the column (K), in the presence of an inert solvent, wherein an intermediate boiler having a boiling point between the boiling point of the isocyanate and the boiling point of the alcohol under the operating conditions of the carbamate dissociation is used as inert solvent and is fed as external runback (4) in liquid form in a purity of >95% by weight, based on the total weight of the external runback (4), in t

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 present invention relates to a process for continuously preparing a mononitrated organic compound, especially a process for preparing mononitrobenzene. The invention relates more particularly to an improved continuous adiabatic process for preparing nitrobenzene.

Abstract: The invention relates to a process for preparing polyisocyanates by reacting primary amines with phosgene, which comprises the steps a) mixing the amine with the phosgene, b) reacting the amine with the phosgene in a residence reactor and, if desired, c) transferring the output from the reactor of step b) into a distillation column, wherein the residence reactor in step b) is configured as a tube reactor.

Abstract: The invention provides a multistage process for continuously preparing organic, distillable polyisocyanates, preferably diisocyanates, more preferably aliphatic or cycloaliphatic diisocyanates, by reacting the corresponding organic polyamines with carbonic acid derivatives and alcohols to low molecular mass monomeric polyurethanes, and thermally cleaving said polyurethanes, in which at defined reaction stages the polyisocyanates prepared and unusable residues are separated off, and reusable by products and intermediates are recycled to upstream stages.

Abstract: Processes are disclosed comprising: (a) reacting an aqueous formaldehyde solution in a reactor in the presence of a suitable catalyst to obtain a reaction product mixture comprising trioxane, formaldehyde and water; (b) distilling the reaction product mixture to form a top stream comprising crude trioxane; and (c) treating the top stream in one or more additional stages to form pure trioxane; wherein an aqueous sidestream is drawn off during the distilling of the reaction mixture.

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 invention relates to an improved multistage process for the continuous preparation of diisocyanates by reaction of the corresponding diamines with carbonic acid derivatives and alcohols to form low molecular weight monomeric urethanes and thermal dissociation of the latter.

Abstract: An integrated process for preparing trioxane from formaldehyde.

Abstract: This invention relates to a process for working up residues from production of isocyanates. This process involves hydrolyzing residues from production of at least one isocyanate with water to form a hydrolysis product, and processing the hydrolysis product within an extruder or a kneader having a heat transfer surface, to form a mixed product containing at least one amine and water. The amine and the water are separated from the mixed product to form an amine/water mixture, which is then separated to obtain the water and the amine. The process may also involve separating all or part of the water from the hydrolysis, or separating part of the amine from the hydrolysis, prior to the processing of the hydrolysis product.

Abstract: The invention provides a process for preparing isocyanates by reacting amines with phosgene, wherein the amine or a mixture of amine and a solvent is mixed in the form of an aerosol with gaseous phosgene and the amine is subsequently reacted with phosgene.

Abstract: The invention relates to a process for preparing isocyanates and/or polyisocyanates by reacting the corresponding amines with phosgene, optionally in the presence of an inert medium, in a reactor (1), a first reactant stream comprising the amine being supplied to the reactor (1) in liquid form, and a second reactant stream comprising the phosgene being supplied to the reactor in gaseous form. The reactor is a centrifugal reactor (1) having a packing (9) which rotates about a central axis (7) in a housing (13), the first reactant stream and the second reactant stream being supplied to the rotating packing (9) such that the reactant streams are mixed due to the centrifugal force in the rotating packing (9) and are transported outward, the mixing in the rotating packing (9) resulting in reaction of the phosgene with the amine to give the corresponding isocyanate or polyisocyanate.

Abstract: A process for preparing polyoxymethylene homopolymers or copolymers (7) by homopolymerization or copolymerization of trioxane, starting from methanol (1), in which methanol (1) is oxidized in a first reactor in a first production plant (A) to give an aqueous formaldehyde-comprising stream (2) which is fed to a second production plant (B) in which pure trioxane (6) is obtained and removal of low boilers (5) by distillation is carried out and the pure trioxane (6) is fed to a third production plant (C) in which it is homopolymerized or copolymerized to form polyoxymethylene homopolymers or copolymers (7), wherein the low boiler stream (5) from the low boiler removal column (K 2) is recycled to the feed stream into the first reactor in the first production plant (A), is proposed.

Abstract: A process for removing trioxane from a use stream I of formaldehyde, trioxane and water, by a) providing a use stream I which comprises formaldehyde as the main component and trioxane and water as the secondary components, b) feeding the use stream I, a recycle stream V and a recycle stream VII which comprises formaldehyde as the main component and water and trioxane as the secondary components into a first distillation stage and distilling to obtain a stream II a steam III and formaldehyde as the and a steam X c) distilling the stream III, in a second distillation stage the pressure in the second distillation stage being from 0.

Abstract: A process for separating trioxane from a feed stream I comprising formaldehyde, trioxane and water, in which a) a feed stream I comprising formaldehyde as main component and trioxane and water as secondary components is provided, b) the feed stream I, a recycle stream V and a recycle stream VII comprising formaldehyde as main component and water and trioxane as secondary components are fed into a first distillation stage and distilled at a pressure of from 0.1 to 2.5 bar to give a stream II comprising formaldehyde as main component and water as secondary component and a stream III comprising trioxane as main component and water and formaldehyde as secondary components and a stream X comprising water, trioxane and formaldehyde, c) the stream III is, if appropriate after removal of low boilers from the stream III in a low boiler removal stage, distilled in a second distillation stage at a pressure of from 0.2 to 17.5 bar, with the pressure in the second distillation stage being from 0.

Abstract: The present invention relates to a process for preparing polyisocyanates from natural raw material sources, in which a composition comprising low molecular weight aromatics which comprise at least one hydroxy group or at least one alkoxy group per molecule (oxyaromatics) is produced from a biomass material, these oxyaromatics are converted into the corresponding aromatic amines and, optionally after condensation with formaldehyde, reacted further with phosgene to give compounds comprising isocyanate groups.

Abstract: The present invention relates to a process for preparing diisocyanates from diamines and phosgene in the gas phase.

Abstract: The invention relates to a process for the preparation of formamides by reacting aromatic amines with a formic acid ester in the presence of a catalyst, wherein the catalyst is a phosphorus-containing acid or a Lewis-acidic metal salt.

Abstract: Process for preparing aromatic isocyanates by reacting the corresponding formamides with an oxygen-comprising gas over noble metal catalysts at temperatures of from 300 to 600° C. and a contact time of from 1 to 1000 ms, wherein: a. the formamide is vaporized before entering the reaction zone, b. the reaction mixture obtained is quenched with an alcohol-comprising quenching liquid and c. the urethane formed is dissociated into isocyanate and alcohol.

Abstract: A process is proposed for preparing isocyanates by thermally cleaving carbamates to obtain a carbamate cleavage gas comprising the corresponding isocyanate and the corresponding alcohol, which comprises quenching the carbamate cleavage gas in the presence of an ether which functions as an inhibitor for the reverse reaction of the isocyanate with the alcohol.