摘要:
An arrangement for carrying out chemical reactions comprises at least one distillation column and/or at least one container and at least one circulation evaporator, which are connected to one another via connecting elements, liquid being taken off completely or partly from a tray or from a stacked packing bed or from a dumped packing bed or from a liquid collector of the distillation column or being fed as an external feed stream below the lower tube sheet of the circulation evaporator to said evaporator.
摘要:
In an aqueous formaldehyde solution comprising formaldehyde in the form of monomeric formaldehyde, methylene glycol and polyoxymethylene glycols in a total concentration x of ≧65% by weight, the mean molar mass M of the polyoxymethylene glycols is, as a function of the formaldehyde concentration, equal to or less than the values given by equation I: ( M _ g / mol ) = 48 + 6.589 · 10 - 1 · ( x % by weight ) + 4.725 · 10 2 · ( x % by weight ) 2 - 3.434 · 10 - 3 · ( x % by weight ) 3 + 9.625 · 10 - 5 · ( x % by weight ) 4 - 1.172 · 10 6 · ( x % by weight ) 5 + 5.357 · 10 - 9 · ( x % by weight ) 6 ( I ) where: M is the mean molar mass, and x is the total concentration of formaldehyde in the form of monomeric formaldehyde, methylene glycol and polyoxymethylene glycols in % by weight (total formaldehyde concentration).
摘要:
In a process for preparing mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number by two-stage reaction of the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, separation of the excess phosgene and solvent after the phosgenation is complete and thermal treatment of the reaction product, the mass ratios of phosgene to hydrogen chloride in the residence time apparatus of the second stage of the phosgenation are at the same time 10-30:1 in the liquid phase and 1-10:1 in the gas phase.
摘要:
A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C.In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.
摘要:
The invention relates to a method for producing a highly pure, aqueous hydroxylamine solution by distilling an aqueous solution, devoid of salt, of a hydroxyl ammonium salt in a plate column comprising at least two mechanical plates. Said method is characterised in that packing bodies are arranged between at least two plates of the plate column over the cross-section of said column.
摘要:
Process for preparing organic isocyanates, which comprises the steps (a) making available a first partial amount of chlorine, with the chlorine of this first partial amount having a content of free and bound bromine and iodine of
摘要:
A process for preparing a salt-free aqueous hydroxylamine solution by distilling an aqueous solution of a hydroxylammonium salt and a base in a tray column having at least two mechanical trays, wherein random or structured packings are located above at least one tray of the tray column over the cross section of the column.
摘要:
A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.
摘要:
The invention relates to a process for the preparation of amines by hydrogenation of nitro compounds, which comprises carrying out the hydrogenation in a vertical reactor whose length is greater than its diameter, having a downward-facing jet nozzle arranged in the upper region of the reactor through which the starting materials and the reaction mixture are fed in, and having an outlet at any desired point of the reactor, through which the reaction mixture is fed back to the jet nozzle in an external circuit by means of a conveying means, and having flow reversal in the lower region of the reactor.
摘要:
An aqueous solution of free hydroxylamine is prepared by treating a hydroxylammonium salt with ammonia by the countercurrent method in a stripping column by a process in which hydroxylamine is liberated and at the same time the solution obtained is separated by distillation into an aqueous hydroxylamine solution and a salt fraction. The novel process can be carried out in a simple and gentle manner and on a large scale. The danger of decomposition is minimized owing to the low thermal load, the low concentration of hydroxylamine and the short residence time in the process.