JPH0441136B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new process for producing glycine salts from monoethanolamine. More specifically, the present invention relates to characteristic reaction conditions, additives, and catalysts for producing glycine salts by reacting monoethanolamine in the presence of alkali metal and/or alkaline earth hydroxides.

For example, the production of glycine soda from monoethanolamine proceeds according to the reaction formula (1) shown below, and the production of glycine from glycine soda proceeds according to the reaction formula
Proceed according to (2).

H ₂ NCH ₂ CH ₂ OH + NaOH water, catalyst --- → 2COONa + 2H ₂ (1) H ₂ NCH ₂ COONa + 1/2H ₂ SO ₄ →H ₂ NCH ₂ COOH + 1/2Na ₂ SO ₄ (2) Glycine salt is usually neutralized Glycine is widely used as a food additive in meat processing, soft drinks, instant foods, and other processed foods. It is also used in a wide range of fields including medicines, agricultural chemicals, and raw materials for amino acids.

As an industrial method for producing glycine salts, the Stretzker method, which uses prussic acid and formaldehyde as main raw materials, is generally known today. However, since hydrocyanic acid is a highly poisonous gas, there are major restrictions in terms of manufacturing equipment, handling, and location.Furthermore, since most of the hydrocyanic acid is obtained as a by-product during the production of acrylonitrile, there are also major problems in securing a stable supply of raw materials.

On the other hand, a method for producing glycine salt by oxidative dehydrogenation of monoethanolamine in a caustic alkali is disclosed in US Pat. No. 2,384,816 and US Pat. No. 2,384,817. The method disclosed in Example 1 of U.S. Patent No. 2,384,816 involves reacting monoethanolamine and potassium hydroxide without a catalyst, so the reaction time is long and the glycine yield is approximately 33%.
%. It is also stated that the presence of water promotes the attack of amino groups, and potassium hydroxide, which has good solubility in monoethanolamine, is used as a caustic alkali. Meanwhile, US Patent No. 2384817
The method disclosed in Examples 1 and 2 of this issue involves the addition of monoethanolamine and flaked potassium hydroxide in the presence of a toxic cadmium oxide catalyst.
The reaction is carried out while raising the temperature to 160-185°C, and in this case too, the glycine yield is about 6.5%.

In this way, the yield of conventional techniques is too low in non-catalyzed reactions, and in reactions using cadmium oxide as a catalyst, there is a risk that admium compounds, which are toxic substances, may be mixed into the reaction product, so they are not suitable for use as food additives. Since this method is not suitable for producing glycine salts and has a low yield, it has not been possible to compete with the Stretzker method until now.

As a result of extensive research into the oxidative dehydrogenation method of monoethanolamine as a method for producing glycine salts that can replace the Stretzker method, the present inventors have found that a method for producing glycine salts that can be produced without using cadmium compounds, which has toxicity problems, has been developed. We have discovered a new method for producing glycine salts with high yield and completed the present invention.

The present invention relates to a method for producing glycine salts in high yield by reacting monoethanolamine in the presence of an alkali metal and/or alkaline earth metal hydroxide, a copper-containing catalyst, and water.

A feature of the present invention is that when producing glycine salts from monoethanolamine, a safe copper-containing catalyst is used in an aqueous solution of alkali metal and/or alkaline earth metal hydroxides at By using it under extremely mild conditions of 220°C, the glycine salt yield was increased to 92 to 97 mol% based on monoethanolamine.
By carrying out the present invention, it has become possible to improve the yield of glycine salt, shorten the reaction time, and use milder reaction conditions as compared to conventional methods. As a result, the production cost of glycine salts can be drastically reduced, and an innovative method for producing glycine salts using oxidative dehydrogenation of monoethanolamine, which is easy to implement industrially, has been completed.

In one embodiment of the present invention, the catalyst used in the method of the present invention contains copper as an essential component. The catalyst can be used as it is or supported on an alkali-resistant carrier. The amount of catalyst used ranges from 1 to 70% by weight, preferably from 10 to 30% by weight, based on monoethanolamine. The form of the catalyst is not particularly limited, but metal copper whose surface has been oxidized in air, oxygen or with an appropriate oxidizing agent and then reduced in a hydrogen atmosphere, and Raney copper which has been developed with an alkali and then washed with water. Copper activated materials, such as those made by thermally decomposing copper formate and other copper salts, are preferably used.

Since the activity of the catalyst usually decreases little due to reaction, it can be used repeatedly, but it can also be used once.

Water in the reaction of the present invention was conventionally thought to promote the decomposition of amino groups, but under the mild reaction conditions of the present invention, the decomposition of amino groups was very small, and rather, the water used in the reaction of monoethanolamine and alkali metals and/or It has the advantage of being able to react alkaline earth metal hydroxides in a homogeneous system, and is essential for obtaining high yields of glycine salts. The amount of water used in the reaction is at least 10% by weight, preferably in the range of 100 to 500% by weight, based on monoethanolamine.

The alkali metal hydroxide used in the present invention includes lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Further, alkaline earth metal hydroxides include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and the like. Among these, sodium hydroxide and potassium hydroxide are particularly preferably used. The amount of alkali metal and/or alkaline earth metal hydroxide used is at least the equivalent of monoethanolamine used in the reaction, preferably in the range of 1.0 to 2.0 equivalents. As the alkali metal and/or alkaline earth metal hydroxide, any of flakes, powders, pellets, etc. and aqueous solutions thereof can be used, but aqueous solutions of alkali metals are generally preferably used because of their ease of handling.

Monoethanolamine is preferably of high purity in order to avoid contamination of the glycine salt with impurities. Although there is no particular restriction on purity, it is usually 96
The amount used is at least 99% by weight, preferably at least 99% by weight.

The reaction temperature is _NH2 group of monoethanolamine,
In order to prevent thermal decomposition and hydrogenolysis of the NH ₂ groups of the glycine salt, the reaction is carried out at a temperature of 220°C or lower, usually in the range of 120 to 220°C, preferably in the range of 140 to 190°C.
Additionally, at temperatures above 220°C, some of the surfaces of copper catalysts begin to sinter, the surface area decreases, and catalytic activity begins to decline. preferable.

Since the reaction is an oxidative dehydrogenation reaction, it is preferable to lower the reaction pressure as much as possible from the viewpoint of reaction rate. Usually, the pressure is higher than the minimum pressure for proceeding the reaction in a liquid phase, preferably in the range of 0 to 20 kg/cm ² G, more preferably 5 to 15 kg/cm ² G.

The reaction time can be selected as appropriate and is determined by the reaction temperature, amount of catalyst, and reaction pressure. For example, reaction temperature
In the case of 160° C., reaction pressure of 10 Kg/cm ² G, and a catalyst amount of 10% by weight based on monoethanolamine, the reaction time is 4 to 6 hours.

As for the reaction format, any of batch, semi-batch and continuous reaction methods can be used.

Hereinafter, embodiments of the present invention will be specifically illustrated and explained with reference to Examples. The present invention is not limited to these examples.

Here, the conversion rate of monoethanolamine and the selectivity of glycine salt are derived from the following equation.

Conversion rate of monoethanolamine (%) = Number of moles of reacted monoethanolamine/Number of moles of monoethanolamine subjected to reaction x 100 Selectivity of glycine salt (%) = Number of moles of glycine salt produced/Number of reacted monoethanolamine Number of moles of monoethanolamine x 100 Example 1 79.3g of monoethanolamine, 56g of sodium hydroxide, 135.3g of water and 8.0g of developed Raney copper
Pour into a 500ml autoclave and heat with hydrogen gas for 3 minutes.
After internal displacement, reaction temperature 160℃, reaction pressure 9
The reaction was carried out at Kg/cm ² G until no hydrogen was generated. The time required for the reaction was 4 hours after the temperature was raised to 160°C. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of monoethanolamine was found to be
The selectivity for glycine salt was 98.1 mol% and 97.2 mol%.

Example 2 79.3 g of monoethanolamine, 56 g of sodium hydroxide, 135.3 g of water, and copper formate were heated at 200 g in a hydrogen stream.
8.0 g of metallic copper obtained by thermal decomposition for 3 hours at ℃ was placed in a 500 ml autoclave, and after internal displacement with hydrogen gas three times, the reaction temperature was 160 ℃ and the reaction pressure was 9 Kg/cm ² G.
The reaction was continued until no hydrogen was generated. The time required for the reaction was 6 hours after the temperature was raised to 160°C. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion of monoethanolamine was 97.5 mol%, and the selectivity of glycine salt was 95.1 mol%.

Example 3 Monoethanolamine 79.3g, potassium hydroxide
78.5g, water 135.3g and expanded Raney copper 8.0g to 500
ml autoclave, and after internal purge with hydrogen gas three times, the reaction temperature was 160℃, and the reaction pressure was 9Kg/
The reaction was carried out at cm ² G until no more hydrogen was produced. The time required for the reaction was 4 hours after the temperature was raised to 160°C. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of monoethanolamine was found to be
The selectivity for glycine salt was 98.2 mol% and 96.5 mol%.

Claims (1)

[Scope of Claims] 1. A method for producing a glycine salt, which comprises reacting monoethanolamine in the coexistence of an alkali metal and/or alkaline earth metal hydroxide, water, and a copper-containing catalyst. 2. The method according to claim 1, wherein the reaction is carried out at a temperature of 120 to 220°C. 3. The method according to claim 1, wherein the reaction is carried out at a pressure of 0 to 20 kg/cm ² G. 4. The method according to claim 1, wherein the alkali metal hydroxide is sodium hydroxide. 5. The method according to claim 1, wherein the alkali metal hydroxide is potassium hydroxide.