DE102008053315A1 - Preparation of tetrahydrofuran, comprises heating 1,4-diacetoxy butane in the presence of a strong acid and excess water to reflux and continuously separating the formed tetrahydrofuran by rectification - Google Patents

Abstract

Preparation of tetrahydrofuran, comprises heating 1,4-diacetoxy butane in the presence of a strong acid and excess water to reflux and continuously separating the formed tetrahydrofuran by rectification.

Description

Industrially tetrahydrofuran is released by intramolecular dehydration Butanediol-1,4 obtained in the presence of an acidic catalyst.

For the preparation of the starting product butanediol-1.4 (hereinafter abbreviated as BDO) exist several competing methods. One of these methods starts with butadiene. Butadiene is first converted into 1,4-diacetoxybutene-2 with acetic acid in the presence of oxygen, and 1,4-diacetoxybutane (hereinafter abbreviated to DAB) is obtained therefrom by catalytic hydrogenation. From DAB, the desired BDO is then subsequently produced by acid-catalyzed hydrolysis (cf., for example, US Pat. US Patent 5,397,439 ).

A serious disadvantage of this process results from the unfavorable position of the self-adjusting hydrolysis equilibrium. Even when using a very large excess of water only partial sales of DAB are achieved, so that in addition to large amounts of water and unreacted DAB and the corresponding monoester with great effort of formed butanediol (BDO) must be separated energy-intensive (see. U.S. Patent 4,010,197 )

A company using this procedure - MCI in Japan - recently announced that it would have to shut down a production facility under this procedure for too high a cost (cf. www.icis.com/v2/chemicals/9075175/butanediol.html ). Thus, according to this method, the important secondary product of the BDO namely the tetrahydrofuran can no longer be made competitive.

It has now become a new, improved process for the production of THF from DAB found that the disadvantages described does not have.

To DAB is in the presence of excess water and a strong acid heated to reflux and the THF which forms by hydrolysis and dehydration continuously overflows distilled off a rectification column attached to the hydrolysis reactor.

THF falls here in the form of its aceotrope with a water content (5-6%) and can if necessary by known methods be converted into anhydrous THF. By suitable Choice of temperature and pressure in the hydrolysis / distillation apparatus manages to obtain directly practically anhydrous THF.

The liberated during the hydrolysis of acetic acid accumulates in this process in the bottom of the distillation apparatus and can be prepared therefrom by known methods ( Ullmann's Encylopedia of Ind. Chem., Sixth Edition, 2002 Electronic Release "Acetic Acid, Chap. 4.5 ) are concentrated to anhydrous acetic acid and used to maintain the value in the oxidative acetoxylation of butadiene.

The new process is characterized by great simplicity and especially through energy-efficient complete sales out.

It can be both batchwise and particularly advantageous perform continuously. In the paragraph-wise driving style becomes the acid catalyst and excess Water in a stirred tank with attached Rektifikationskolonne submitted and then heated to reflux. With continued stirring, one pumps then DAB at a rate as the forming THF in the distillate receiver accumulates. The heat supply to the reactor is regulated in this way A, that up to a turnover of the DAB of approximately 90% a reflux ratio of around 1 is complied with. Then you increase this until the complete sales to around 2-3. After that the entire DAB was fed to the reactor, one sets the Heat to reflux further. You take distillate for so long until the head temperature has risen by about 5 degrees. In general, enough for the addition of DAB 2-3 hours and for the afterreaction 30 minutes completely off. The in the distillate template accumulated THF has a maximum water content of 6%. By gas chromatographic Analysis ensures that the THF thus obtained free of any impurities is. The yield bez. on DAB is virtually quantitative. she lies in any case over 98%.

The remaining in the bottom of the stirred tank hydrous acetic acid can be dehydrated after removal of the catalyst by known methods (see. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition 2002, Acetic Acid, Ch. 4.5 ) and then use value-preserving in the synthesis of the DAB precursor 1,4-diactoxybutene-2. Up to a water content of about 20%, the removal of water by means of flash extraction with NN-disubstituted acetamides has proved successful (cf. DE-A-2545658 ). Even easier, the water separation succeeds at levels greater than 20% by extractive distillation in the presence of the already mentioned acetamides such. B. with Nn-butyl-N-ethylhexyl-acetamide (see. EP 0468303 B1 ).

By addition of the reaction equations for the preparation of the DAB and the hydrolysis thereof and for the elimination of water released during the hydrolysis BDO can be seen that in the claimed process for the synthesis of the Zielpro THF only the precursors butadiene, hydrogen and oxygen are required as starting materials. Suitable catalysts for the hydrolysis of the DAB and the intramolecular dehydration to THF are all strong acids that do not undergo undesirable chemical reactions with BDO such. B. with hydrochloric acid. An enumeration of the acids in question can be found, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2002 Electronic Release, Esters Organic, Ch. 5.1.1 ,

Especially preferred are strong acids in the reaction medium insoluble are such. B. strong acid cation exchangers (Generally crosslinked polystyrenesulfonic acids) such as Amberlite IR 120, Dowex HCR and 50 WX, Lewatit S 100 or Diaion SK 1B H.

example

In a stirred tank with a patch on this Packed column with 10 theoretical plates Place 270 parts of water and 100 parts of Dowex 50 WX and heat boiling the reactor contents. After reaching the boiling point to pump 61 parts DAB every hour. The formation of THF gives by lowering the head temperature to 62-63 degrees C to recognize. After reaching this temperature, you start with the decrease of the THF in the form of its aceotrope with water. The heat supply from the outside you regulate so that a reflux ratio from approx. 1 is complied with. After a total of 183 parts DAB the Reactor were added to increase the reflux ratio on approx. 3 and decreases THF as distillate until the temperature has reached 70 degrees C at the top of the column.

In the distillate sample then have 73.4 parts of THF with a water content by Max. 6% accumulated. In the gas chromatogram of the distillate are to detect any impurities.

The The yield of anhydrous THF is thus 98.4%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 5397439 [0002]
• - US 4010197 [0003]
• - DE 2545658 A [0011]
• - EP 0468303 B1 [0011]

Cited non-patent literature

• - www.icis.com/v2/chemicals/9075175/butanediol.html [0004]
• - Ullmann's Encylopedia of Ind. Chem., Sixth Edition, 2002 Electronic Release "Acetic Acid, Chap. 4.5 [0008]
• Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition 2002, Acetic Acid, Ch. 4.5 [0011]
• - Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2002 Electronic Release, Esters Organic, Chap. 5.1.1 [0012]

Claims (3)

Process for the preparation of tetrahydrofuran (THF), characterized in that 1,4-diacetoxy-butane (DAB) is heated to reflux in the presence of a strong acid and excess water and the forming tetrahydrofuran is continuously separated by rectification. Process according to claim 1, characterized characterized in that the catalyst is a strong, in the reaction medium insoluble acid. Process according to claim 1, characterized characterized in that the resulting in the hydrolysis, aqueous Acetic acid by flash extraction with N.N-disubstituted Acetamides or by extractive distillation in the presence of freed the above-mentioned acetamides of water and then used again for the synthesis of the DAB precursor 1.4.Diacetoxy-butene.