DE1015789B - Process for the continuous production of isopropenyl acetate - Google Patents

Description

GERMAN

It is known to use isopropenyl acetate by condensation of ketene with acetone in the presence of an enolizing agent Catalyst, such as concentrated sulfuric acid, or by organic or inorganic residues substituted sulfuric acid, such as chlorosulfonic acid or acetylsulfoacetic acid, or others in the sense of a Enolization to produce effective catalysts. The best yields are obtained when using Acetylsulfoacetic acid as a catalyst in a concentration between 0.1 and 5% at a reaction temperature between 60 and 75 ° and a ratio from 1 mole of ketene to 2 to 3 moles of acetone. Under these conditions, about 8% ketene conversion is obtained a yield of about 75% based on acetone and about 70 to 75% based on ketene. Most of all so far processes described by the American side are almost exclusively of a discontinuous type, while the few known continuous processes give significantly lower yields.

It has now been found that isopropenyl acetate is formed continuously from ketene and acetone at approximately the molar level Ratio of 1 to 2 to 3 in the presence of an enolizing catalyst, preferably in the presence of acetylsulfoacetic acid as a catalyst, thereby producing at temperatures between about 60 and about 75 ° lets that a circulation evaporator is used as the reaction vessel, which is equipped with a gas inlet tube for ketene and an overflow device for continuous removal of the reaction product is provided.

According to the present, continuously operating process, in addition to quantitative ketene conversion Yields of about 95% based on acetone and about 92% based on ketene achieved. Also owns this new process, especially with regard to its technical usability, still has the advantage that it is without Stirrer or pump, i.e. without any moving parts, works. This is a significant benefit as the Acetic anhydride, which is a by-product in small quantities, is an extremely aggressive substance is. One leg of the reaction vessel 1 is, as the sketch shows, provided with a heating device 2, which allows the reaction mixture in the reactor, consisting of about 50% acetone, 50% isopropenyl acetate, along with contact and by-products, to the boil. Below this An inlet pipe 3 for ketene is provided on the same leg of the heating device. The evaporating Acetone is condensed in a packed column 4 that is attached to the reactor and is cooled to -20 ° and fed back through the return line 5 to the reactor. The resulting circulation of the Reaction mixture is made by introducing ketene through the inlet pipe 3 in the manner of the mammoth

Process for continuous production of isopropenyl acetate

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brüningstr. 45

Dr. Otto Horn, Frankfurt / M.-Höchst,

and Dr. Walter Krause, Frankfurt / M.-Unterliederbach,

have been named as inventors

the pump principle is still significantly supported. An overflow device 6 attached to the reactor above the mouth of the return line 5 serves for the continuous removal of the reaction product. The packed column 4 is connected to a brine cooler 7 and can be sprinkled with fresh acetone from a storage tank 8. Below the column 4 there is a dropping device 9 for fresh contact, from which the amount of fresh contact necessary to maintain the desired contact concentration can be metered into the acetone return line 5. The vigorous circulation of the reaction mixture brings about intimate contact between ketene, acetone and contact and thus the conversion of ketene and acetone is significantly promoted. Unreacted ketene is quantitatively dissolved in the absorber column by the acetone, which is cooled to about -20 ° and trickling in countercurrent to the ketene, and is returned to the reactor via line 5. In this way, in addition to quantitative Ketenumsatz an increase in yields is achieved which essentially are to learn more about where the \ ⁷ previously known.

US Pat. No. 2,481,669 already describes a continuous process for the production of Isopropenyl acetate described. However, this is just like the method of the German patent specification 908 017, in contrast to the present process, carried out in two stages, the first stage in an absorption of ketene in acetone at reduced pressure and low temperature and the second stage is carried out in the presence of catalysts at temperatures of 30 to 100 °. This means that the solvent (acetone, isopropenyl acetate or a mixture thereof) is combined with the ketene dissolved therein and by-products such as diketone, acetic anhydride, etc., by a

709 697/416

Pump is circulated. In contrast, in the present method, the aggressive By-products, such as ketene, diketene, acetic anhydride, etc., are not circulated and do not keep coming with the moving parts, stuffing boxes and other sealing devices an apparatus in contact, as in the methods of U.S. Patent 2,481,669 and German Patent 908 017, which is a major advantage. Incidentally, the yield is that of the known one Procedure only minor. It is less than 45%, calculated on the Keten, and on the (consumed) Acetone calculated, about 90% or in the case of the Germans Patent 68% based on the ketene.

Finally, Swiss patent 239 537 describes a continuous process for production of vinyl esters described, in which the reaction of the reaction components in a reaction furnace with a catalyst filling, an upstream evaporator and downstream Heat exchanger is carried out. In this process, however, no circulation evaporator is used, and the reaction carried out thereby is different from the present reaction.

example

The reaction vessel, which has a capacity of about 500 ecm up to the overflow 6, is filled with a mixture of 250 g Acetone, 250 g of isopropenyl acetate and 5 g of acetylsulfoacetic acid filled. This mixture is made possible by the Heater "is brought to the boil, and at the same time 2 moles (84 g) of ketene per hour are introduced. The column 4 is sprinkled with 316 g of acetone per hour from the acetone tank, and in the same time 4 g of fresh contact are fed to the reaction mixture via line 5. The temperature in the reaction vessel is about 70 °. After a running time of 5 hours, 2006 g of crude product overflowed and im Reactor there are another 503 g of crude product. The distillation in vacuum gives:

1265 g acetone,

1170 g isopropenyl acetate, b.p. 200: 59 to 61 °,

44 g residue,

30 g distillation losses.

The isopropenyl acetate yield is% based on acetone and 92% based on ketene.

Claims (3)

Patent claims: 1. Process for the continuous production of isopropenyl acetate by reacting ketene and acetone in the presence of an enolizing catalyst, preferably in the presence of Acetylsulfoacetic acid as a catalyst, at temperatures between about 60 and about 75 ° and one Ratio of 1 mole of ketene to 2 to 3 moles of acetone, characterized in that the reaction vessel a circulation evaporator is used, which is equipped with a gas inlet pipe for ketene and a Overflow device is provided for continuous removal of the reaction product. 2. The method according to claim 1, characterized in that the evaporating in the circulation reactor Acetone condenses and together with fresh acetone the reactor via a return line is fed back. 3. The method according to claim 1 and 2, characterized in that the circulation reactor is not reacted ketene dissolved in it in countercurrent trickling acetone and then the reactor is fed again. Considered publications:
German patent application B 18802 IVd / 12 ο;
Swiss Patent No. 239 537;
U.S. Patent No. 2,481,669. 1 sheet of drawings 1 705 697/416 9.57