Covestro Deutschland Ag

Covestro Intellectual Property Gmbh & Co. Kg

Jürgen Arras

Christian Steffens

Jan Busch

Javier Pérez-Ramirez

Stefan Wershofen

Dietmar Wastian

Tim Loddenkemper

Markus Dugal

Manfred Keller-Killewald

Tobias Caesar Keller

Holger Conzelmann

Tobias Cäsar Keller

Javier PERÈZ-Ramirez

The invention relates to an improved process for making available the coproduct hydrogen chloride obtained in the preparation of an isocyanate by phosgenation of the corresponding amine for a desired subsequent use (i.e. a chemical reaction), in which part of the total hydrogen chloride obtained is isolated in gaseous form at a pressure which is higher than the pressure desired for the subsequent use of the hydrogen chloride by lowering the pressure of the crude product from the phosgenation and the remaining part of the total hydrogen chloride obtained is separated off at a pressure lower than that desired for the subsequent use from the liquid crude product from the phosgenation remaining after lowering of the pressure and is subsequently compressed to a pressure which is higher than that desired for the subsequent use, and in which the two hydrogen chloride streams obtained in this way are, preferably together after having been combined, purified so as to give a purified hydrogen chloride at a pressure which is higher than the pressure desired for the subsequent use.

Process for providing hydrogen chloride for chemical reactions

The industrial scale preparation of isocyanates gives rise to distillation bottom streams that are in need of further workup. These distillation bottom streams still also contain, as well as a distillation residue consisting of compounds that can be evaporated without decomposition only with great difficulty if at all (also referred to as residue for short), proportions of the desired target product (i.e. isocyanate to be prepared). The present invention relates to a process that enables recovery, in an efficient manner, of this proportion of isocyanate to be prepared in a distillation bottom stream which is obtained in the workup of the crude liquid process product which contains the isocyanate to be prepared and is formed in an isocyanate preparation process. More particularly, the present invention relates to a drying step in which the isocyanate to be prepared is recovered to form a solid material that has been largely to completely freed of this isocyanate. This drying step is characterized by a minimum content of compounds containing carbodiimide groups of 15% by mass, preferably 20% by mass, more preferably 30% by mass, based on the total mass of the distillation residue fed to the drying apparatus used, where this minimum content can also be adjusted by an in situ carbodiimidization.

Process for preparing an isocyanate

The invention relates to a production process for di- and polyamines of the diphenylmethane series by the rearrangement of a condensation product of aniline and a methylene group-supplying agent preferably selected from the group consisting of aqueous formaldehyde solution, gaseous formaldehyde, para-formaldehyde, trioxane and mixtures thereof, wherein said condensation product is reacted in the presence of at least one silica-alumina catalyst, said catalyst having

Process for the production of di- and polyamines of the diphenylmethane series

The invention relates to a production process for polyamines through condensation of aromatic amines with formaldehyde employing at least one solid zeolite catalyst partially or fully ion-exchanged to the protonic form which has been

The present invention relates to a continuous process for preparing a polyisocyanate, in which a polyamine and phosgene are first converted predominantly to carbamoyl chloride and amine hydrochloride and only in minor proportions to polyisocyanate, and a portion of the carbamoyl chloride- and amine hydrochloride-containing reaction mixture thus obtained is recycled into the reaction with phosgene, wherein polyamine, phosgene and the carbamoyl chloride- and amine hydrochloride-containing reaction mixture are mixed intimately in a mixing unit. The portion of the carbamoyl chloride- and amine hydrochloride-containing reaction mixture which is not recycled into the phosgenation is worked up to give the polyisocyanate.

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Itzehoe, Germany

Jürgen Arras