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EP-4739657-A1 - METHOD FOR PREPARING TRIACETONE AMINE

EP4739657A1EP 4739657 A1EP4739657 A1EP 4739657A1EP-4739657-A1

Abstract

A process for preparing triacetone amine (TAA) comprises (i) reacting acetone and ammonia to yield a reaction product comprising TAA, acetone, mesityl oxide and TMDP; (ii) directing the reaction product to an acetone separation tower to obtain an unreacted acetone stream; and a first bottoms stream; (iii) directing the first bottoms stream to an azeotrope separation tower to obtain an azeotrope distillate stream containing aqueous azeotropes of mesityl oxide and TMDP; and a second bottoms stream; (iv) directing the second bottoms stream to a middle-boiler separation tower to obtain a middle-boiler stream; and a third bottoms stream; (v) directing the third bottoms stream to a finishing tower to obtain pure TAA as a distillate stream; (vi) subjecting the azeotrope distillate stream to phase separation to obtain an organic phase and an aqueous phase; directing the organic phase to a TMDP separation tower to obtain a recyclables distillate stream containing mesityl oxide, and a bottoms stream containing TMDP; and (vii) recycling the unreacted acetone stream, the middle-boiler stream and the recyclables distillate stream at least partially to step (i); and discarding the TMDP bottoms stream.

Inventors

  • BENFER, REGINA
  • HEYDT, Thomas
  • SCHMITT, MICHAEL
  • GUENTHER, KLAUS
  • GEBAUER, Felix
  • HALABI, MOHAMED

Assignees

  • BASF SE

Dates

Publication Date
20260513
Application Date
20240701

Claims (10)

  1. 1. A process for preparing triacetone amine, the process comprising (i) reacting acetone and ammonia in the presence of a catalyst to yield a reaction product comprising TAA, acetone, mesityl oxide and TMDP; (ii) directing the reaction product to an acetone separation tower to obtain an unreacted acetone stream; and a first bottoms stream; (iii) directing the first bottoms stream to an azeotrope separation tower to obtain an azeotrope distillate stream containing aqueous azeotropes of mesityl oxide and TMDP; and a second bottoms stream; (iv) directing the second bottoms stream to a middle-boiler separation tower to obtain a middle-boiler stream; and a third bottoms stream; (v) directing the third bottoms stream to a finishing tower to obtain pure TAA as a distillate stream, and a bottoms stream containing high-boilers; (vi) subjecting the azeotrope distillate stream to phase separation to obtain an organic phase and an aqueous phase; directing the organic phase to a TMDP separation tower to obtain a recyclables distillate stream containing mesityl oxide, and a bottoms stream containing TMDP; and (vii) recycling the unreacted acetone stream, the middle-boiler stream and the recyclables distillate stream at least partially to step (i); and discarding the TMDP bottoms stream.
  2. 2. The process according to claim 1, wherein the first bottoms stream contains 2 wt.-% of acetone or less.
  3. 3. The process according to claim 1 or 2, wherein in the azeotrope separation tower a sufficient amount of water is available to permit formation of aqueous azeotropes of essentially the total amount of mesityl oxide and TMDP contained in the first bottoms stream.
  4. 4. The process according to any one of the preceding claims, comprising recycling the aqueous phase at least partially to the azeotrope separation tower.
  5. 5. The process according to any one of the preceding claims, wherein the catalyst is a heterogeneous catalyst, preferably zeolite.
  6. 6. The process according to any one of the preceding claims, wherein the acetone separation tower is operated at a pressure of 0.8 to 1.5 bara.
  7. 7. The process according to any one of the preceding claims, wherein the azeotrope separation tower is operated at a pressure of 0.2 to 0.5 bara.
  8. 8. The process according to any one of the preceding claims, wherein the middleboiler separation tower is operated at a pressure of 0.05 to 0.07 bara.
  9. 9. The process according to any one of the preceding claims, wherein the finishing tower is operated at a pressure of 0.004 to 0.008 bara.
  10. 10. The process according to any one of the preceding claims, wherein the TMDP separation tower is operated at a pressure in the range of from 0.1 to 0.5 bara.

Description

Method for Preparing Triacetone Amine Triacetone amine (2,2,6,6-tetramethyl-4-piperidinone; hereinafter "TAA") is an important chemical intermediate which is used for the synthesis of numerous derivative products, for example hindered amine light stabilizers (HALS), and nitroxyl radicals that are employed, e.g., as polymerization moderators. TAA is produced by the reaction of acetone with ammonia. Known methods for the preparation of TAA include homogeneously catalyzed methods or heterogeneously catalyzed methods. Catalysts used in homogeneously-catalyzed reactions include calcium chloride (e.g., in Chemical Industries 2003, 89, 559-564; Zeitschrift fur Naturforschung 1976, 328-337 and 338-345), ammonium chloride (e.g., in JP 2003-206277 A; JP 2001-31651 A; JPH4-154762 A) and hydrazine derivatives (e.g., in JPS54-88275 A, J PS54-112873 A). Heterogeneous catalysts have been described, for example in DE 28 07 172 A1 and CN 103224465 A. US 10,807,954 discloses a method for preparing triacetone amine while recycling byproducts. The method involves treating the crude product from the triacetone amine preparation with water, which allegedly leads to an increased content of compounds which react readily with ammonia. TAA is generally prepared in a matrix in which acetone is present in a large excess and serves both as a reactant and solvent. The reaction is an equilibrium reaction and hence inherently incomplete. Therefore, at the end of the reaction a crude product is obtained which, aside from TAA, contains unreacted acetone, unreacted ammonia, and water formed by the condensation reaction. In addition, further secondary components are present, e.g., acyclic condensation products (e.g., diacetone alcohol, diacetone amine, mesityl oxide, phorone, etc.), cyclic condensation products (e.g., acetonin, 2, 2,4,6- tetramethyl-2,3-dihydropyridine (hereinafter "TMDP")) or higher molecular weight condensation products ("high boilers"). Some acyclic addition and condensation products (e.g., diacetone alcohol (4-hydroxy-4- methylpentan-2-one), diacetone amine (4-amino-4-methylpentan-2-one), mesityl oxide (4-methylpent-3-en-2-one), phorone, etc.) can be reacted with ammonia to give TAA. Hence they may be used as a partial replacement of acetone. Recycling of the acetone condensation products within the process has been suggested in DE 28 07 172 AT Unreacted acetone is predominantly isolated during downstream distillation steps. The described by-products are difficult to remove from excess acetone and the desired product TAA. The known processes suffer from limited separation efficiency. This is, in part, due to the close proximity of the boiling points of some of the by-products. The situation is aggravated by formation of closely boiling azeotropic mixtures. The following table shows the order of the boiling points (at 1 bar) of the predominant by-products and their azeotropes along with selected boiling points. The most problematic by-product in the synthesis of TAA is TMDP. It has a high thermal stability and, unlike the other by-products of TAA synthesis, cannot be reused as starting material in the synthesis of TAA. In this sense, TMDP is an organosynthetic dead end. Recycling of TMDP into the TAA synthesis adds to the energy consumption of the process or, worse, may lead to undesirable side reactions that reduce the yield of TAA. In addition, TMDP complicates the distillative purification of the TAA from the resulting reaction mixture. TMDP tends to be ubiquitous in the distillation train and significant amounts are found in the isolated TAA. This difficulty arises from the fact that TMDP forms both azeotropes with water and acetone condensation products such as DAAM and DAA. These azeotropes have intermingling boiling points resulting in TMDP being "smeared", that is, having a broad boiling range. In distillative purification, many distillation stages are therefore necessary to recover TAA and unreacted starting material such as acetone or other by-products such as mesityl oxide essentially free of TMDP. This in turn requires a complex distillation apparatus, such as a column with a large number of theoretical plates. Thus, an object of the present invention is to overcome the abovementioned drawbacks and to provide an improved process for producing purified TAA. Another object of the present invention is to provide an improved process for producing TAA with lower amounts of by-products; preferably a lower amount of TMDP. Yet another object of the present invention is to provide an improved process for producing triacetone amine with an efficient re-utilization of the by-products obtained in the TAA synthesis. The invention relates to a process for preparing triacetone amine, the process comprising (i) reacting acetone and ammonia in the presence of a catalyst to yield a reaction product comprising TAA, acetone, mesityl oxide and TMDP; (ii) directing the reaction product to an acetone separation tower to obtain an