Preparation of 1,4-butanediol

Details Preparation of 1,4-butanediol Preparation of 1,4-butanediol

1996-12-27

1999-08-31

Shippen, Michael L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C07L 2700

Patent

active

059455713

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the preparation of 1,4-butanediol.
WO 92/20667 relates to a process for the preparation of 4-hydroxybutyraldehyde/2-hydroxytetrahydrofuran mixtures, in which, in a first stage, 2,5-dihydrofuran is isomerized to 2,3-dihydrofuran in the presence of rhodium-phosphine or ruthenium-phosphine complexes homogeneously dissolved in the reaction medium and is then removed, by distillation, from the reaction mixture. The 2,3-dihydrofuran is then caused to react with water over an acid catalyst to form a mixture of 4-hydroxybutanal and 2-hydroxytetrahydrofuran, and this mixture is isolated. The proposal made is to convert the mixture thus obtained to 1,4-butanediol by hydrogenation. Starting from 2,3-dihydrofuran, 2 stages are thus required in order to arrive at 1,4-butanediol.
U.S. Pat. No. 4,859,801 teaches that it is possible to cause reaction of 2,3-dihydrofuran with an aldehyde and hydrogen in the presence of water at a pH of from 8 to 14 using a hydrogenating catalyst to form mixtures of 1,4-butanediol and 2-alkyl-1,4-butanediol. The yield of 1,4-butanediol is moderate in this process. If the 2,3-dihydrofuran used in the reaction is hydrogenated directly, tetrahydrofuran is formed therefrom as main product. 1,4-Butanediol is formed in small amounts only.
EP-A 340,170 relates to the hydrogenation of 4-hydroxybutyraldehyde/2-hydroxytetrahydrofuran mixtures previously prepared in a separate procedure in a basic medium and in the presence of an aldehyde to form 2-alkyl-1,4-butanediols, part of this mixture being hydrogenated to 1,4-butanediol.
It was thus the object of the present invention to provide a process for the preparation of 1,4-butanediol starting from 2,3-dihydrofuran, which makes it possible to obtain 1,4-butanediol in a single stage in good yield and selectivity.
Accordingly, we have found a process for the preparation of 1,4-butanediol, wherein 2,3-dihydrofuran is caused to react in a single stage, in the presence of water and hydrogen at a temperature of from 20.degree. to 300.degree. C. and a pressure of from 1 to 300 bar in a neutral or acidic environment over a hydrogenating catalyst.
In the process of the invention 2 reaction stages are thus carried out in a single process stage, ie 4-hydroxybutyraldehyde and its isomer 2-hydroxytetrahydrofuran as shown in equation (1) ##STR1## and b) the catalytic hydrogenation of the mixture obtained as per equation (1) and consisting of 4-hydroxybutyraldehyde and 2-hydroxytetrahydrofuran--both compounds being in equilibrium with each other--to form 1,4-butanediol as shown in equation (2) ##STR2##
When carrying out the process of the invention the 2,3-dihydrofuran is generally caused to react with water in a molar ratio of 2,3-dihydrofuran to water of from 1:1 to 1:100, preferably from 1:1 to 1:50, and more preferably from 1:1 to 1:10 and in the presence of hydrogen and a hydrogenating catalyst at a pressure of, in general, from 1 to 300 bar, preferably from 5 to 250 bar, and more preferably from generally 15 to 200 bar and at a temperature of from 20.degree. to 300.degree. C., preferably from 40.degree. to 230.degree. C., and more preferably from 80.degree. to 200.degree. C. to form 1,4-butanediol.
The reaction of the invention is carried out in a neutral or acidic environment, ie at pH's of the aqueous phase which are in the acid or neutral pH range, preferably at pH's in the range of from 2 to 7.5, particularly from 4 to 7.2, and more particularly in the range of from 6 to 7. When use is made of water-insoluble heterogeneous catalysts, operating the process in a neutral or acidic environment means that the catalysts used act non-basically and preferably contain Lewis or Broensted acid centers which influence the course of the reaction in the desired manner, that is to say to effect the formation of predominantly 1,4-butanediol.
Suitable hydrogenation catalysts for use in the process of the invention are generally all catalysts which are suitable for the hydrogenation of carbonyl groups.
It is possible to use hydr

REFERENCES:
patent: 4476332 (1984-10-01), Nalepa
patent: 4859801 (1989-08-01), Ernst
Fakely et al., Hydrogenation and Hydrogenation catalysts, Solid Supports and Catalysts in Organic Synthesis, pp. 275-287., 1992.

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