Method for preparing L-pyroglutamic acid

Abstract

The invention discloses a method for preparing L-pyroglutamic acid, which comprises the following steps: placing L-glutamic acid in an ethanol system; adding a proper amount of a dehydration catalyst; heating to 88 to 100 DEG C to perform the dehydration reaction; after the reaction, carrying out filtering, concentration and crystallization; carrying out suction filtration on crystals to obtain the L-pyroglutamic acid competitive product. The method disclosed by the invention belongs to a closed process, is simple to operate and adopts a proper proportion; the L-pyroglutamic acid generated through dehydration is soluble to ethanol, the L-glutamic acid which is not dehydrated is insoluble to ethanol, the L-glutamic acid which is not dehydrated is directly removed by filtering, crystallization is carried out to obtain the high-purity L-pyroglutamic acid, and the obtained L-pyroglutamic acid has purity of over 99.5 percent and yield of over 85 percent; due to addition of the dehydration catalyst concentrated sulfuric acid, the dehydration reaction is accelerated; moreover, the reaction is performed at a lower reaction temperature, so that the L-pyroglutamic acid is prevented from generating racemization; the concentrated sulfuric acid is in a mother liquor obtained by suction filtration and can be returned together with the L-glutamic acid for next batching; the method is low in cost and is suitable for industrial production.

Description

Technical field

[0001] The invention relates to a method for preparing L-pyroglutamic acid. Background technique

[0002] L-Pyroglutamic acid, English name: L-Pyroglutamic acid, chemical name: L-2-pyrrolidone-5-carboxylic acid. L-pyroglutamic acid can be used as a biochemical reagent, mainly for the resolution of racemic amines. Currently, L-pyroglutamic acid is used as a cosmetic moisturizer in the field of daily chemicals.

[0003] The synthesis of pyroglutamic acid on the market is mainly made by dehydrating glutamic acid as a raw material. The synthesis of L-pyroglutamic acid reported by Feng Dayan in the "Chemical World" magazine is obtained by dehydration and cyclization of glutamic acid, and the yield is generally 75.3-63.3%. This synthesis method is suitable for L-glutamic acid The dehydration reaction temperature and time have strict requirements, which should be controlled at about 150°C and maintained for 45 minutes. If the temperature is higher than 160°C, L-pyroglut...

Examples

Embodiment 1

[0018] A method for preparing L-pyroglutamic acid, including: adding 147g of L-glutamic acid, 500ml of absolute ethanol, 2ml of concentrated sulfuric acid into a 1000L three-necked flask, heating to 90℃, and maintaining at 90℃ for 4 hours. Dehydration reaction. After the reaction, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure at a temperature of 55°C to saturation. The ethanol concentrate of L-pyroglutamate is cooled to 20°C, and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out and dried at a temperature of 55°C to obtain 115 g of L-pyroglutamic acid refined product with a yield of 89.1%.

Embodiment 2

[0020] A method for preparing L-pyroglutamic acid, including: adding 294g of L-glutamic acid, 1200ml of absolute ethanol, 2ml of concentrated sulfuric acid into a 2000L three-necked flask, heating to 92°C, and maintaining at 92°C for 5 hours. Dehydration reaction. After the reaction, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure at a temperature of 60°C to saturation. The ethanol concentrate of L-pyroglutamate is cooled to 20°C, and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out and dried at a temperature of 60°C to obtain 233 g of L-pyroglutamic acid refined product, with a yield of 90.3%.

Embodiment 3

[0022] A method for preparing L-pyroglutamic acid, including: adding 221g of L-glutamic acid, 900ml of absolute ethanol, 2.3ml of concentrated sulfuric acid into a 2000L three-necked flask, heating to 95°C, and maintaining at 95°C for 3 hours The dehydration reaction is carried out. After the reaction is completed, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure to saturation at a temperature of 55°C. The ethanol concentrate of L-pyroglutamate is cooled to 25°C and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out with suction, and dried at a temperature of 55°C to obtain 175g of L-pyroglutamic acid refined product, with a yield of 90.2%.

Technical field

[0001] The invention relates to a method for preparing L-pyroglutamic acid. Background technique

[0002] L-Pyroglutamic acid, English name: L-Pyroglutamic acid, chemical name: L-2-pyrrolidone-5-carboxylic acid. L-pyroglutamic acid can be used as a biochemical reagent, mainly for the resolution of racemic amines. Currently, L-pyroglutamic acid is used as a cosmetic moisturizer in the field of daily chemicals.

[0003] The synthesis of pyroglutamic acid on the market is mainly made by dehydrating glutamic acid as a raw material. The synthesis of L-pyroglutamic acid reported by Feng Dayan in the "Chemical World" magazine is obtained by dehydration and cyclization of glutamic acid, and the yield is generally 75.3-63.3%. This synthesis method is suitable for L-glutamic acid The dehydration reaction temperature and time have strict requirements, which should be controlled at about 150°C and maintained for 45 minutes. If the temperature is higher than 160°C, L-pyroglut...

Examples

Embodiment 1

[0018] A method for preparing L-pyroglutamic acid, including: adding 147g of L-glutamic acid, 500ml of absolute ethanol, 2ml of concentrated sulfuric acid into a 1000L three-necked flask, heating to 90℃, and maintaining at 90℃ for 4 hours. Dehydration reaction. After the reaction, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure at a temperature of 55°C to saturation. The ethanol concentrate of L-pyroglutamate is cooled to 20°C, and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out and dried at a temperature of 55°C to obtain 115 g of L-pyroglutamic acid refined product with a yield of 89.1%.

Embodiment 2

[0020] A method for preparing L-pyroglutamic acid, including: adding 294g of L-glutamic acid, 1200ml of absolute ethanol, 2ml of concentrated sulfuric acid into a 2000L three-necked flask, heating to 92°C, and maintaining at 92°C for 5 hours. Dehydration reaction. After the reaction, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure at a temperature of 60°C to saturation. The ethanol concentrate of L-pyroglutamate is cooled to 20°C, and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out and dried at a temperature of 60°C to obtain 233 g of L-pyroglutamic acid refined product, with a yield of 90.3%.

Embodiment 3

[0022] A method for preparing L-pyroglutamic acid, including: adding 221g of L-glutamic acid, 900ml of absolute ethanol, 2.3ml of concentrated sulfuric acid into a 2000L three-necked flask, heating to 95°C, and maintaining at 95°C for 3 hours The dehydration reaction is carried out. After the reaction is completed, the reaction solution is filtered while it is hot. The ethanol filtrate of L-pyroglutamate is concentrated under reduced pressure to saturation at a temperature of 55°C. The ethanol concentrate of L-pyroglutamate is cooled to 25°C and a large amount of crystals are precipitated. The L-pyroglutamic acid crystals were filtered out with suction, and dried at a temperature of 55°C to obtain 175g of L-pyroglutamic acid refined product, with a yield of 90.2%.

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