Process for producing isocyanate and at least one further chemical product in an integrated production

Patent metadata

Field	Value
Publication number	US-10618871-B2
Application number	US-201716325809-A
Country	US
Kind code	B2
Filing date	Aug 15, 2017
Priority date	Aug 17, 2016
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

The present invention relates to a process for producing isocyanates in process chains, each of which produce an isocyanate end product via at least one intermediate product, wherein the heat energy liberated in a first production plant in a heat-emitting operation of producing an intermediate product, an isocyanate end product or a catalyst required for a substep of the process chain (first chemical product) is at least partly utilized for generating vapour, in particular water vapour, having a pressure of 1.31 bar(abs.) to 1.91 bar(abs.) and a temperature of 107° C. to 119° C. and the thus generated vapour is employed for performing a heat-consuming operation in the preparation of another chemical product (second chemical product) in a second production plant.

First claim

The invention claimed is:

1. A process for preparing m isocyanates in m process chains, in each of which an isocyanate is prepared as end product via at least one intermediate, comprising:
conducting each of the m process chains in at least 2 production plants, comprising a first production plant designed for preparation of the at least one intermediate and a second production plant designed for preparation of the isocyanate end product, wherein the at least 2 production plants are part of an integrated production system, and
preparing a total of n chemical products selected from the group consisting of intermediates, catalysts and isocyanate end products in the integrated production system, where n is a natural number in the range from 2 to 40, and where m is a natural number in the range from 1 to n,
wherein, in the preparation of each of the n chemical products, at least one heat-releasing or heat-consuming operation takes place and, in the process for preparing the m isocyanates, a total of at least one heat-releasing operation and at least one heat-consuming operation takes place,
wherein
(i) the heat energy released in a heat-releasing operation in the preparation of one of the chemical products in the first production plant is utilized at least partly for generation of vapor at a pressure of 1.31 bar (abs.) to 1.91 bar (abs.) and a temperature of 107° C. to 119° C.;
(ii) the vapor generated in (i) is used for performing a heat-consuming operation in the preparation of a chemical product different than the chemical product prepared in step (i), where the preparation of the chemical product different than the chemical product prepared in step (i) takes place in the second production plant, wherein the vapor generated in (i) is guided from the vapor-releasing point in step (i) via a pipeline to the position of the heat-consuming operation in step (ii).

2. The process of claim 1 , in which the isocyanate end product is selected from the group consisting of methylene diphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, mixtures of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, tolylene diisocyanate, xylylene diisocyanate, pentane 1,5-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and naphthyl diisocyanate.

3. The process of claim 1 , in which the isocyanate end product is an aromatic isocyanate and in which a first process chain (α) comprises:
A) nitrating an aromatic hydrocarbon in a first process stage to give an aromatic nitro compound;
B) hydrogenating the aromatic nitro compound in a second process stage by hydrogenation to give an aromatic amine; and
C) converting the aromatic amine in a third process stage by phosgenation to give the aromatic isocyanate end product;

and/or
a second process chain (β) comprises:
A) nitrating an aromatic hydrocarbon in a first process stage to give an aromatic nitro compound;
B) hydrogenating the aromatic nitro compound in a second process stage to give an aromatic amine;
C) converting the aromatic amine in a third process stage to another aromatic amine; and
D) phosgenating the another aromatic amine in a fourth process stage to give the aromatic isocyanate end product.

4. The process of claim 3 , in which the phosgenation in process stage (α) C) and/or in process stage (β) D) comprises:
I) reacting the amine to be phosgenated with phosgene in the liquid phase and separating the process product obtained into a liquid stream comprising the crude isocyanate and solvent, and a gaseous stream comprising phosgene and hydrogen chloride;
II) separating the liquid stream from step I) into a liquid stream comprising solvent and crude isocyanate, and a gaseous stream comprising phosgene and hydrogen chloride in a distillation apparatus;
III) separating the liquid stream comprising and crude isocyanate into a gaseous stream comprising solvent and a liquid stream comprising crude isocyanate in a distillation apparatus;
IV) separating the gaseous stream comprising solvent, after it has been at least partly liquefied in a condenser, into a liquid stream comprising solvent and a gaseous stream comprising phosgene in a distillation apparatus;
V) obtaining a liquid isocyanate stream from the liquid stream comprising crude isocyanate, resulting in a gaseous stream comprising secondary components and optionally solvent, in a distillation apparatus, optionally comprising a step V.1) comprising removing polymeric isocyanate fractions in an upstream unit for polymer removal.

5. The process of claim 4 , comprising process chain (β), wherein the amine phosgenated in process stage (β) D) is a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine, wherein step V.1) is conducted and the isocyanate end product is obtained in two streams and, wherein one stream comprises methylene diphenylene diisocyanate and another stream comprises a mixture of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate.

6. The process of claim 5 , in which the heat-releasing operation from step (i) is the at least partial liquefaction of the gaseous stream comprising solvent in the condenser, and in which the vapor generated by the release of heat is guided into process stage (β) C).

7. The process of claim 6 , in which process stage (β) C) comprises:
in a variant A)
IA) reacting aniline and formaldehyde in a first reactor in the absence of an acidic catalyst to form an aminal, followed by separating the reaction mixture obtained into an aqueous phase and an organic phase comprising the aminal in a phase separation unit integrated into the reactor or in a separate phase separation apparatus;
IIA) reacting at least a portion of the organic phase comprising the aminal which is obtained in step IA) in a second reactor with acid, with reaction of the aminal to give a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine;
or in a variant B)
IB) reacting aniline and acid in a reactor;
IIB) reacting at least a portion of the reaction mixture obtained in step IB) in a reactor with formaldehyde to give a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine;
and in either variant A) or B),
III) neutralizing the reaction mixture obtained in step IIA) or IIB) in a third reactor;
IV) separating the neutralized reaction mixture obtained in step III) into an organic phase comprising a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine and into an aqueous phase in a separation vessel;
V) washing the organic phase with washing liquid in a wash vessel;
VI) separating the mixture obtained in step V) into an organic phase comprising a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine and into an aqueous phase in the separation vessel;
VII) distilling the organic phase from step VI) in a distillation apparatus comprising a first distillation stage for removal of a water- and aniline-containing stream and a second distillation stage for further purification of the process product remaining in the first stage after removal of the water- and aniline-containing stream to obtain a mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine, with optional use of stripping vapor in the second stage for direct transfer of heat; and
VIII) optionally separating methylene diphenylene diamine from the mixture of methylene diphenylene diamine and polymethylene polyphenylene polyamine obtained in step VII).

8. The process of claim 7 , in which process stage (β) C) further comprises:
IX) workup
of the aqueous phase from step IA) or
of the aqueous phase from step IV) or
of

Assignees

• Covestro Deutschland Ag

Inventors

• Spriewald Jürgen
• Adamson Richard
• Knauf Thomas

Classifications

• C07C209/54

  by rearrangement reactions · CPC title

• B01J2219/00495

  Means for heating or cooling the reaction vessels · CPC title

• B01D3/148

  in combination with at least one evaporator · CPC title

• B01J2219/0059

  Sequential processes · CPC title

• C07C265/14

  containing at least two isocyanate groups bound to the same carbon skeleton · CPC title