Vitamin A isomerization method

Abstract

The invention discloses a vitamin A isomerization method. The method comprises the steps of (1) controlling the content of vitamin dimers in VA crude oil containing 11-cis-vitamin A and 9-cis-vitamin A to be 0.001-0.02%; and 2) carrying out an isomerization reaction on the VA crude oil obtained in the step 1) under the action of a homogeneous metal catalyst to generate the all-trans vitamin A. According to the method, 11-cis-vitamin A and 9-cis-vitamin A in the VA crude oil can be isomerized into all-trans vitamin A efficiently at the same time, and the conversion rate of the total cis-vitamin A is high.

Description

technical field [0001] The invention relates to an isomerization method, in particular to a vitamin A isomerization method. Background technique [0002] Vitamin A has different synthesis routes, the most representative of which are the C6+C14 route of Roche and the C5+C15 route of Basf. The composition of vitamin A isomers synthesized by different routes is quite different. The main geometric configurations of vitamin A synthesized by BASF route are all-trans vitamin A, 11-cis vitamin A and 9-cis vitamin A. Among them, all-trans vitamin A has the highest biological activity, isomerizing 11-cis vitamin A and 9-cis vitamin A into all-trans vitamin A can greatly increase the yield of all-trans vitamin A and reduce production costs , which is of great significance to industrial production. [0003] Conventional isomerization methods mainly include thermal isomerization, photoisomerization and chemical isomerization. Thermal isomerization generally needs to be achieved at a h...

AI Technical Summary

Problems solved by technology

Photoisomerization usually requires the addition of a photosensitizer to achieve a good isomerization effect, but photosensitizers are generally highly toxic and even carcinogenic, which affects the quality of the final product. At the same time, due to the particularity of the photoisomerization reaction device, industrialization is not conducive to the realization of

[0004] Chemical isomerization is a common way of isomerization of vitamin A. It is reported in the patent US5908957A that NO or NO, N 2 The mixture is used as a catalyst to isomerize vitamin A. This method is mainly suitable for isomerizing 11-cis vitamin A to all-trans vitamin A, but it is known in the field that the isomerization of 9-cis vitamin A is difficult, so it is implemented As can be seen from the example data, all examples cannot contain 9-cis vitamin A isomerization

[0005] It is reported in the patent US4051174A that 9-cis vitamin A can be converted to all-trans vitamin A by using a palladium-containing compound as a catalyst, but the conversion rate of 9-cis vitamin A is low, and this conversion process can only be carried out in raw materials containing only In the case of 9-cis vitamin A and all-trans vitamin A, when the raw material contains other cis isomers (such as 11-cis vitamin A), 9-cis vitamin A cannot contribute to the all-trans vitamin A conversion, and the conversion of other cis isomers will lead to an increase in the content of 9-cis vitamin A

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