Process for producing 3-hydroxypropionitrile

Details Process for producing 3-hydroxypropionitrile Process for producing 3-hydroxypropionitrile

2001-01-17

2002-10-08

McKane, Joseph (Department: 1626)

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

Organic compounds

Nitriles

Reexamination Certificate

active

06462219

ABSTRACT:

FIELD OF THE INVENTION
The present invention is concerned with a process for the production of 3-hydroxypropionitrile, which is an important intermediate in the process for the manufacture of panthenol. The end product, especially its d(+) isomer, is a valuable agent for the treatment of dermatoses, burns and infectious ulcers, as well as a valuable additive in shampoos and other cosmetics.
BACKGROUND OF THE INVENTION
Various methods for the production of 3-hydroxypropionitrile are known from the literature. For example, the reaction of 2-chloroethanol with an alkali cyanide to yield 3-hydroxypropionitrile (also known as “ethylene cyanohydrin”) was described in Annalen der Chemie und Pharmacie 128, 1 (1863). Later publications, such as, for example, Org. Synth. 3, 57 (1923), J. Soc. Chem. Ind. 67, 458 (1948) and Britton et al., U.S. Pat. No. 2,311,636, concern the optimization of this basic production method. Despite the high yields allegedly achieved, the process is uninteresting commercially because of the relatively high purchase price of the 2-chloroethanol starting material, as well as the difficulty in controlling the exothermic reaction. Moreover, not only is there contamination with salt but there is also great expense involved in isolating and purifying the product of the process.
The successful production of 3-hydroxypropionitrile by the addition of hydrocyanic acid to ethylene oxide was reported around 1930 in various German patents, namely in German Patents Nos. 561,397, 570,031 and 577,686. The optimization of this addition process was described in Luskin, U.S. Pat. No. 2,653,162, in which a carboxylic acid sodium salt resin is used as the weak base, water is used as the solvent, and the reaction is effected at 45-50° C. Still later disclosures of the production of 3-hydroxypropionitrile by the addition of hydrocyanic acid to ethylene oxide appear in German Offenlegungsschrift No. 4,304,002 as well as in Merger et al., U.S. Pat. No. 5,268,499. However, the two starting materials are very problematical with respect to toxicity and handling. Therefore, these processes would no longer be considered in developing an up-to-date production process for 3-hydroxypropionitrile.
The production of the known 1:1 addition product of water and acrylonitrile (i.e. of 3-hydroxypropionitrile) in the presence of a basic catalyst gives rise to certain difficulties since the product reacts with further acrylonitrile to give the condensation product bis(cyanoethyl)ether, NC(CH
2
)
2
O(CH
2
)
2
CN, as described in Howk et al., U.S. Pat. No. 2,579,580. Howsmon, U.S. Pat. No. 3,024,267 and Japanese Patent Publication (Kokai) No. 196,850/1984 disclose that somewhat better yields of the desired 3-hydroxypropionitrile are achieved when the reaction is carried out in a large excess of water (i.e. at high dilution) or according to J. Org. Chem. USSR 1987, 1087, in the presence of a large amount of base. However, these measures are uneconomical, especially because of the unavoidably complicated working up, the evaporation of water, and the contamination with salt. Moreover, at such high dilution, small to medium amounts of bis(cyanoethyl)ether are also formed.
The reaction of aqueous formaldehyde with acrylonitrile in the presence of strongly basic Amberlyst® IRA-400, OH
−
form, at about 40° C. is proposed in German Patent No. 2,655,794 as a possible solution to the above problems. However, the indicated yield of 3-hydroxypropionitrile, 75%, is moderate in this case, too.
Thus, the processes outlined above for the direct production of 3-hydroxypropionitrile have evident disadvantages.
Japanese Patent Publications (Kokai; JP) Nos. 160,949/1989, 90,160/1989, and 185,550/1983 disclose that bis(cyanoethyl)ether can be produced from acrylonitrile and water in the presence of a strong basic ion exchanger, and that the product can subsequently be pyrolyzed by means of a basic catalyst to yield the desired 3-hydroxypropionitrile and acrylonitrile. The base-catalyzed production of bis(cyanoethyl)ether from acrylonitrile and water is also known from earlier references, such as, for example, Org. Reactions 5, 79 (1945) (review article), J.A.C.S. 65, 23 (1943), J.A.C.S. 67, 1996 (1945), Ind. Eng. Chem. 44, 1388 (1952), German Patents Nos. 731,708 and 1,189,975 as well as U.S. Pat. Nos. 2,382,036, 2,448,979 and 2,816,130 to Bruson, Hopff et al., and Selcer et al., respectively. As the catalyst for this 2:1 addition reaction, a strong base (e.g. sodium hydroxide) is generally used, although a strongly basic Amberlyst® catalyst, such as Amberlyst® IRA-400, OH
−
form, can also be used. At least small amounts of 3-hydroxypropionitrile are formed irrespective of the acrylonitrile:water ratio, the reaction temperature, or the respective strong base that is used. Based on these documents, yields of up to about 77% could be achieved using strongly basic catalysts (e.g. Amberlyst® IRA-400, OH
−
form). The cleavage of the bis(cyanoethyl)ether described in the aforementioned Japanese patent publications is effected using a basic catalyst, especially aqueous or aqueous-methanolic potassium hydroxide/dipotassium phosphate at 72-100° C./5 mm Hg, with about 85% yield (JP 160,949/1989, JP 90,160/1989) or tetraethylammonium acetate at 100-105° C./10 mm Hg, with about 86% yield (JP 185,550/1983).
SUMMARY OF THE INVENTION
One aspect of the claimed invention is a process for the production of 3-hydroxypropionitrile that includes the reaction of water with acrylonitrile to give a mixture of the desired product and the bis(cyanoethyl)ether condensation product, and then the pyrolysis of this product mixture to additional 3-hydroxypropionitrile, whereby not only the mentioned reaction, but also the pyrolysis, are carried out under specific base-catalyzed and other conditions. Another aspect of this process is that, if desired, unreacted reactants, especially acrylonitrile and the water containing the catalyst, can be conducted back into the reaction system for re-use. This overall multi-stage process provides for the altogether surprisingly economical production of 3-hydroxypropionitrile, particularly because this product is formed only to some extent during the first step of the process, yet is obtained in high yield after the penultimate (pyrolysis) step.
The claimed process includes (a) reacting acrylonitrile with water at a defined molar ratio in the presence of a weak base under specific temperature and pressure conditions until a conversion in the range of about 40% to about 80% has been achieved; (b) after cooling the mixture obtained in (a), separating off its aqueous phase; (c) distilling off the acrylonitrile from the organic phase remaining after (b); (d) subjecting the mixture obtained in (c) to pyrolysis at specific temperature and pressure conditions in the presence of a basic catalyst to obtain a mixture consisting mainly of 3-hydroxypropionitrile and acrylonitrile; and (e) isolating the desired 3-hydroxypropionitrile by fractional distillation from the mixture obtained in (d). Such a process in which the basic aqueous phase and the acrylonitrile that has been distilled off are recycled represents a preferred embodiment.
One embodiment of the invention is a process for producing 3-hydroxypropionitrile. This process includes (a) reacting acrylonitrile with water at a molar ratio of about 1:0.5 to about 1:20 in the presence of a weak base at a temperature of about 80° C. to about 150° C. and at a pressure of about 1 bar (0.1 MPa) to about S bar (0.5 MPa) to form a two-phase organic-aqueous mixture and until a conversion of the acrylonitrile and water to 3-hydroxypropionitrile of about 40% to about 80% is achieved, wherein the organic phase consists essentially of bis(cyanoethyl)ether, 3-hydroxypropionitrile and unreacted acrylonitrile, and the aqueous phase consists essentially of an aqueous solution of the weak base; (b) cooling the mixture obtained in (a) and separating the aqueous phase from the organic phase; (c) distilling off the acrylonitrile from the organic phase remaining after (

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