CS231782B1 - Process for producing methyl vinyl ketone - Google Patents

Abstract

The invention relates to a method for the production of methyl vinyl ketone by dehydration of 3-ketobutanol in an environment of boiling aqueous sodium chloride solution and in the presence of concentrated hydrochloric acid], when an azeotropic mixture of methyl vinyl ketone and water leaves the reaction mixture. The possibility of continuous implementation of the process according to the invention and regeneration of the reaction residue predetermines the mentioned method for industrial use. Methyl vinyl ketone is an important intermediate in the synthesis of a whole range of important chemical substances, which are used not only in the production of pharmaceuticals, but also in the chemical industry. An important application of methyl vinyl ketone is the production of 3-methylpentene-(2)-iin(4)-ol(1), one of the basic substances in the synthesis of vitamin A.

Description

The present invention relates to a process for the preparation of methyl vinyl ketone by dehydration of 1-hydroxy-3-butanone.

Several methods for the production of methyl vinyl ketone by dehydration of 1-hydroxy-3-butanone (hereinafter 3-ketobutanol) are known. The dehydration of 3-ketobutanol is carried out in an aqueous medium in the presence of strong acids, with the resulting methyl vinyl ketone leaving the reactor as an azeotropic mixture with water. The methods differ mainly in the type of acid used, the arrangement of the apparatus, possibly the presence of another component in the reaction mixture. Another component in the reaction mixture may be e.g. sodium chloride, ammonium chloride, respectively. alkaline earth chlorides (German Pat. No. 2,052,782 and 2,111,723).

Dehydration of 3-ketobutanol can also be carried out under elevated pressure in the presence of sulfuric acid and acetone (German Pat. No. 2,426,039). The disadvantage of all the prior art processes is that all components leaving the reaction except the main product are considered waste, do not solve the continuous process of production and do not solve the disposal of post-reaction residues. These residues always contain a small amount of methyl vinyl ketone, which is very toxic and therefore must be removed from these residues additionally and laboriously.

In the process for the preparation of the methyl vinyl ketone according to the invention, 3-ketobutanol with a water content of not more than 5% by weight is used. is gradually added to a boiling solution of sodium chloride, water and hydrochloric acid. The reaction is carried out at the boiling point of the reaction mixture. The 3-ketobutanol feed rate is equal to the methylvinyl ketone-water azeotrope distillation rate. After the 3-ketobutanol dosing is complete, the reaction mixture is left at the boiling point for a further 2 hours, thereby removing all methyl vinyl ketone from the reaction mixture. The yield of methyl vinyl ketone is 92-95% of theory.

The sodium chloride solution, which was considered a waste in the above-described processes, is left in the reaction vessel, and 1 to 1.5 wt. and a quantity of solid sodium chloride so that a small amount of undissolved sodium chloride remains at the bottom of the reactor. 3-Ketobutanol is added at the boiling point of the mixture. The same methylvinyl ketone yield is obtained as in the first case. Thus, the process can be repeated 5 to 9 times without affecting the quantity and quality of the product produced.

Reactor residue, i. j. the sodium chloride solution and the polymers after completion of the reaction no longer contain any methyl vinyl ketone, so there is no need to remove this toxic substance from waste products.

After the sodium chloride solution has been used three times, polymers will accumulate in the reactor depending on the purity of the 3-ketobutanol used.

The polymers are not miscible with the sodium chloride solution, therefore the two components can be separated from each other, the polymers can be dissolved in an organic solvent, preferably in acetone, hot and disposed of by incineration. The sodium chloride solution may be further used after saturation.

Advantageously, it is possible to work in a duplicate production device operating alternately. In one reactor, the sodium chloride solution used is recovered by removing the polymers, and in the second, methyl vinyl ketone is produced by continuously feeding 3-ketobutanol into a mixture of sodium chloride, water and concentrated hydrochloric acid. After dosing every 200 wt. 1.2 parts by weight of 3-ketobutanol are added to the reactor at a time. parts of concentrated hydrochloric acid, after dosing every 500 wt. 20 parts by weight of 3-ketobutanol are added to the reactor at a time. parts of solid sodium chloride. After dosing the entire amount of 1400 wt. parts of ketobutanol are maintained at reflux for 2 hours, removing all methyl vinyl ketone from the reaction residue.

The examples given above illustrate the process according to the invention, but do not limit it in any way.

Example 1

To a sulfonation flask equipped with a 80 ° C tempered deflegmator, a transfer tube and a condenser, 300 wt. parts by weight of water, 150 wt. parts by weight of sodium chloride and 5 wt. parts of concentrated hydrochloric acid. Nitrogen is supplied below the liquid level. Mechanical mixing is not required. The contents of the sulphonation flask are heated and, when the temperature in the flask reaches 80 ° C, 3-ketobutanol gradually concentrated to a max. water content 5%.

The amount of 3-ketobutanol should be such that it corresponds to 200 wt. % pure 3-ketobutanol. The dosing rate is selected so that the entire amount is added in 2 hours. At the same time it is captured in a template in which 1 wt. part of hydroquinone as stabilizer, methyl vinyl ketone-water mixture. After completion of the dosing, the contents of the sulphonation flask are left at boiling point for 2 hours. 170-175 wt. parts of a methyl vinyl ketone-water mixture containing 145-155 wt. parts of pure methyl vinyl ketone (yield 92-95% of theory J.

The sodium chloride solution is left in a sulfonation flask, 1 wt. 200 parts by weight of concentrated hydrochloric acid are added, and nitrogen is bubbled through. parts of 3-ketobutanol. The methyl-vinyl ketone-water mixture is collected in the same amount and in the same quality as mentioned in the previous paragraph.

This procedure was repeated 7 more times, except that in the fifth, seventh, and ninth repetitions, a portion of the solution was removed from the sulfonation flask to achieve a flood volume of liquid and added increments of 20% each. parts of solid sodium chloride. The yields in the quantity and quality of the product remained the same as in the first case.

The polymers are then separated from the sodium chloride solution, dissolved in an organic solvent, preferably aceitone, hot and disposed of by incineration. The sodium chloride solution is re-usable to the reaction and to the reaction. will be replaced with fresh.

Example 2

The duplicate device described in example 1 shall be used.

This is different from the embodiment of Example 1 in that the amount of 3-ketobutanol corresponding to 1400 wt. % pure 3-ketobutanol. The 3-ketobutanol used must be concentrated to a water content of 3 to 5% by weight. Dosage is continuously administered over 21 hours. After addition every 200 wt. parts by weight of concentrated 3-ketobutanol are added at a time to 1 part by weight of concentrated hydrochloric acid and after each addition of 500 parts by weight. 20 parts by weight of pure 3-ketobutanol are added in one portion. parts of solid sodium chloride. The methyl vinyl vinyl ketone-water azeotrope is continuously collected, which is obtained in total in an amount corresponding to 90 to 94% of theory relative to 3-ketobutanol. After the said amount of 3-ketobutanol has been consumed, the second reactor is operated in the same manner as the first reactor.

The contents of the first reactor are kept at boiling point for a further 2 hours, then allowed to cool, the polymers are separated and dissolved in 200 wt. parts of acetone and disposed of by incineration.

A portion of the aqueous sodium chloride solution is discharged as waste, to the rest is added a photo of solid sodium chloride to keep some of the NaCl undissolved, then 5 wt. parts of concentrated hydrochloric acid. This makes the first reactor ready for further work.

Claims (3)

231782 5 as specified in the previous paragraph. This procedure was repeated 7 times further, except in the fifth and seventh and fifth repetitions, a portion of the solution was removed from the sulphonated flask in order to obtain a flood volume of liquid and 20 wt. solid sodium chloride. Extracts in terms of quantity and civility of the product will remain the same as the first. Polymers are then separated from the sodium chloride solution, dissolved in an orgamic solvent, preferably in acetone under heat and discarded by incineration. The sodium chloride solution is reusable into the reaction, respectively. will be exchanged for fresh. Example 2 A duplicate apparatus as described in Example 1 is used. The embodiment differs from that of Example 1 in that the amount of 3-ketobutanol corresponding to 1400 wt. pure 3-ketobutanol. The 3-ketobutanol used must be concentrated to a water content of 3 to 5% 8 wt. Dosage is carried out continuously over 21 hours. After the addition of every 200 parts by weight of pure 3-ketobutanol, 1 part by weight of concentrated hydrochloric acid is added in one portion and, after addition of 500 parts by weight, 1 part by weight of concentrated hydrochloric acid. parts of pure 3-ketobutanol are added at once to 20 wt. parts of solid chloride sodium. The azeotropmethyl vinyl ketone-water which is obtained in a manner corresponding to 90-94% of theory with respect to 3-ketobutanol is not continuously removed. After consumption of said amount of 3-ketobutanol, the second reactor is activated in the same manner as the first reactor. The contents of the first reactor were left at boiling for 2 hours, then allowed to cool, the polymers separated and dissolved in 200 wt. parts of acetone are discarded by incineration. Part of the aqueous sodium chloride solution is discharged as waste, to the other is added as much solid sodium chloride to keep the NaCl portion undissolved, then 5 wt. parts of concentrated hydrochloric acid. Thus, the first reactor is ready for further work. PŘEĎME A process for the preparation of methyl vinyl ketone by dehydration of 3-ketobutanol in a boiling aqueous solution of sodium chloride and hydrochloric acid, characterized in that the 3-ketobutanol with a water content of up to 5 ° / wt. at a rate of 200 parts by weight for two hours without mechanical stirring and bubbling with nitrogen into a mixture of 150 parts by weight. solid sodium chloride, 300 parts by weight of water and 5 to 6 parts by weight of concentrated hydrochloric acid, each after 200 parts by weight of water; of pure 3-ketobutanol simultaneously adds 1 part by weight of concentrated hydrochloric acid and after every 500 parts by weight. of pure 3-ketobutanol 20 parts by weight are added at once. solid sodium chloride, up to 1400 parts by weight of 3-ketobutanol, the mixture is allowed to boil for 2 hours while still removing azeotropic methyl vinyl ketone / water with a yield of 92 to 95% of theory with respect to 3-ketobutanol, by recovering the sodium chloride solution upon conversion of the reaction and doubling the 3-ketobutanol preparation device and re-generating the sodium chloride solution in the 2. Process according to claim 1, characterized in that the sodium chloride solution, after the addition of the entire amount of 3-ketobutanol is complete, is left to boil for 2 hours to remove the last methyl vinyl ketone and, after cooling the solution, the resulting polymers are separated from the solution by hot dissolution in 200 parts by weight. organic solvents, preferably acetone, and burn. 3. Process according to claim 1, characterized in that a double device is used, in which the dehydration of the 3-ketobutanol is carried out in the first reactor and the regeneration of the sodium chloride solution used in the second reactor. .