Abstract: The invention relates to an integrated process for preparing trioxane from formaldehyde, comprising the steps of: a) a stream A1 comprising water and formaldehyde and a recycle stream B2 consisting substantially of water and formaldehyde are fed to a trioxane synthesis reactor and allowed to react to obtain a product stream A2 comprising trioxane, water and formaldehyde; b) stream A2 is fed to a first low-pressure distillation column and distilled at a pressure of from 0.1 to 2.5 bar to obtain a stream B1 enriched in trioxane and additionally comprising water and formaldehyde, and the recycle stream B2 consisting substantially of formaldehyde and water; c) stream B1 and a recycle stream D1 comprising trioxane, water and formaldehyde are fed to a second low-pressure distillation column and distilled at a pressure of from 0.1 to 2.

Abstract: A process is described for preparing diaminodiarylmethanes comprising the steps a) reacting an aromatic amine with a methylene-donating agent in the presence of homogeneous acid catalysts, b) removing the homogeneous acid catalyst from the reaction product, c) working up and purifying the reaction product, which comprises removing the homogeneous acid catalyst from the reaction mixture by adsorption to a solid adsorbent.

Abstract: The invention relates to a process for preparing isocyanates, which comprises the steps (1) preparation of a crude MDA mixture by reaction of aniline with formaldehyde, with the reaction conditions being selected so that the resulting crude MDA can be converted completely into the gas phase, (2) conversion of the crude MDA mixture from step (1) into the gas phase and (3) phosgenation of crude MDA in the gas phase to give MMDI and PMDI.

Abstract: Process for preparing chlorine from hydrogen chloride, which comprises the steps: a) feeding of a stream a1 comprising hydrogen chloride and of a stream a2 comprising oxygen into an oxidation zone and catalytic oxidation of hydrogen chloride to chlorine, giving a product gas stream a3 comprising chlorine, water, oxygen, carbon dioxide and inert gases; b) cooling of the product gas stream a3 and removal of water and hydrogen chloride as aqueous hydrochloric acid, leaving a gas stream b comprising chlorine, water, oxygen, carbon dioxide and inert gases; c) optional drying of the gas stream b) to leave a gas stream c which is substantially free of water and comprises chlorine, oxygen, carbon dioxide and inert gases; d) at least partial liquefaction of the gas stream c and of a chlorine-rich recycle stream f1 comprising chlorine, oxygen and carbon dioxide by compression and cooling, giving an at least partially liquefied stream d; e) gas/liquid separation of the stream d into a gas stream e1 comprising chlorine,

Abstract: A process for preparing formaldehyde by gas-phase oxidation of methanol vapor by means of a gas stream comprising molecular oxygen in the presence of a fixed-bed catalyst comprising iron and molybdenum, wherein the process is carried out in a reactor (1) having heat-exchange plates (2) which are arranged in the longitudinal direction of the reactor (1) and have a spacing between them and through which a heat transfer medium flows, inlet and outlet facilities (3, 4) for the heat transfer medium to the heat-exchange plates (2) and also gaps (5) between heat-exchange plates (2) in which the fixed-bed catalyst is present and into which the methanol vapor and the gas stream comprising molecular oxygen are passed, is described.

Abstract: Isocyanates are prepared by a process in which a product stream from the isocyanate synthesis is purified.

Abstract: Process for preparing high-concentration formaldehyde solutions having a CH2O content of ?50% by weight from an aqueous formaldehyde solution having a lower CH2O content by evaporation of part of this solution (partial evaporation), in which the aqueous formaldehyde solution is heated to an evaporation temperature T at which the gas phase becomes enriched in water relative to the liquid phase and the gas phase formed is taken off continuously or discontinuously, wherein the evaporation temperature T obeys the relationship: T[° C.]<Tmax[° C.] where Tmax(c)=A+B×(c/100)+C×(c/100)2+D×(c/100)3 and A=+68.759, B=+124.77, C=?12.851, D=?10.095, where c is the instantaneous CH2O content of the aqueous formaldehyde solution during the evaporation in percent by weight and is from 20 to 99% by weight.

Abstract: The invention relates to a process for distillatively preparing TDA from a reactant stream comprising TDA, high boilers and low boilers in a dividing wall column in which a dividing wall is disposed in the longitudinal direction of the column to form an upper combined column region (2), a lower combined column region (3), a feed section (4) having a rectifying section (5) and stripping section (6), and also a withdrawal section (7) having a rectifying section (9) and stripping section (8), which comprises the following steps: a. feeding the reactant stream (13) into the feed section (4) of the dividing wall column (1); b. drawing off a low boiler fraction via the top of the column (11); c. drawing off TDA via a side draw (14) in the withdrawal section (7) of the dividing wall column (1); d. drawing off a low boiler fraction via the bottom of the column (12).

Abstract: A process for preparing a high-concentration formaldehyde solution by removing water from a lower-concentration formaldehyde solution having a formaldehyde content of from 5 to 50% by weight, in which the lower-concentration formaldehyde solution is fed to a preheater and heated in the preheater, depressurized via a pressure maintenance device and concentrated in a helical tube evaporator to give a vapor stream and the high-concentration formaldehyde solution as bottom stream, wherein the heated lower-concentration formaldehyde hyde solution is depressurized in the pressure maintenance device to give a two-phase mixture which is fed into the helical tube evaporator, is proposed.

Abstract: The present invention relates to a process for distillatively removing pure trioxane from a feedstream (I) comprising trioxane in a proportion of at least 50% by weight, based on the total weight of the feedstream (I), and additionally formaldehyde and water, which comprises feeding the feedstream I and a further aqueous stream (II) which does not contain any components extraneous to the feedstream to a dividing wall column (TWK1) having a dividing wall TW which is arranged substantially perpendicularly and divides the column interior into a feed region (A1), a withdrawal reaction (B1), an upper combined column region (C1) and a lower combined column region (D1), and drawing off from the first dividing wall column (TWK1) a bottom stream (III) comprising pure trioxane and a sidestream (IV) at the withdrawal region (B1), comprising pure water.

Abstract: The invention relates to a process for separating hydrogen chloride and phosgene, which comprises bringing a mixture of hydrogen chloride and phosgene into contact with an ionic liquid in which at least part of the hydrogen chloride is dissolved in a step a) and then separating off the hydrogen chloride dissolved in the ionic liquid in a step b).

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: 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) mixing the use stream I with a recycle stream VII which comprises trioxane as the main component and formaldehyde and water as the secondary components to obtain a feed stream Ia which comprises formaldehyde as the main component and trioxane and water as the secondary components, c) distilling the use stream Ia in a first distillation stage at a pressure of from 0.1 to 2.5 bar to obtain a stream II which comprises formaldehyde as the main component and water as the secondary component, and a stream III which comprises trioxane as the main component and water and formaldehyde as the secondary components, d) distilling the stream III, optionally after removing low boilers from the stream III in a low boiler removal stage, in a second distillation stage at a pressure of from 0.2 to 17.

Abstract: The invention relates to a method of operating a liquid ring compressor having an impeller installed eccentrically in a compressor body, with gas being supplied to the liquid ring compressor on a suction side and gas being discharged from the liquid ring compressor on a pressure side. A liquid ring is generated in the liquid ring compressor on the inside of the compressor body by rotation of the impeller. Chambers are formed between blades of the impeller and the liquid ring and gas is drawn into these. The gas is compressed in the chambers which become smaller from the suction side to the pressure side as a result of the rotation of the eccentrically mounted impeller. The compressed gas is ejected on the pressure side. An ionic liquid is used as service liquid for generation of the liquid ring.

Abstract: A process for preparing polyoxymethylene dimethyl ether of the formula H3CO(CH2O)nCH3 where n=2-10, in which methylal and trioxane are fed into a reactor and reacted in the presence of an acidic catalyst, wherein the amount of water introduced into the reaction mixture by methylal, trioxane and/or the catalyst is <1% by weight based on the reaction mixture. Preferably, a fraction comprising polyoxymethylene dimethyl ether where n=3 and 4 is obtained by distillation from the reaction mixture, and methylal, trioxane and polyoxymethylene dimethyl ether where n<3 and optionally n>4 are recycled into the reaction.

Abstract: A process for the preparation of isocyanates by reacting amines with phosgene, the phosgene-containing stream of starting materials (i) being substantially free of isocyanates and (ii) having a mass content of hydrogen chloride (referred to below as HCl) of less than 0.4% by mass, and a production plant for carrying out the process according to the invention.

Abstract: The invention relates to a process for carrying out exothermic chemical equilibrium reactions in a fluidized-bed reactor, wherein there is a temperature distribution in the fluidized bed of the fluidized-bed reactor and the temperature difference between the lowest temperature and the highest temperature is at least 10 K. The invention further relates to a fluidized-bed reactor for carrying out chemical reactions in a fluidized bed (5), wherein at least one heat exchanger (12, 28) is located in the fluidized bed (5) to control the temperature distribution.

Abstract: The invention relates to a reactor and a process for preparing chlorine from hydrogen chloride by gas-phase oxidation by means of oxygen in the presence of a heterogeneous catalyst in a fluidized bed, with gas-permeable plates being located in the fluidized bed. The gas-permeable plates are connected in a thermally conductive manner to a heat exchanger located in the fluidized bed.

Abstract: A process for removing trioxane from a mixture I of formaldehyde, trioxane and water, by a) distilling the mixture I in a first distillation stage at a pressure of from 0.1 to 2 bar to obtain a stream II which comprises formaldehyde and a stream III which comprises predominantly trioxane and additionally water and formaldehyde, b) mixing the stream III with a recycle stream VII which comprises predominantly trioxane and additionally water and formaldehyde to obtain a stream IIIa which comprises predominantly trioxane and additionally water and formaldehyde, c) distilling the stream IIIa, if appropriate after removing low boilers from the stream III or IIIa in a further distillation stage, in a second distillation stage at a pressure of from 0.2 to 10 bar, the pressure in the second distillation stage being at least 0.

Abstract: The present invention relates to a process for preparing sulfur-containing compounds of the general formula I in which Q, R1 and R2 are each independently defined as follows: Q: —S— or —S—S—, R1: hydrogen or saturated or unsaturated, linear or branched C1-C30-alkyl radical, R2: hydrogen or saturated or unsaturated, linear or branched C1-C30-alkyl radical, where R1 and R2 are not simultaneously hydrogen, by reacting a mixed gas stream comprising hydrogen sulfide, with or without oxygen, with linear or branched C1-C30-olefins, which comprises carrying out the reaction in the presence of water and carbon dioxide at a pressure of from 2 to 325 bar.