JPH0153866B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new process for producing nitrilotriacetate from triethanolamine.

More specifically, the present invention relates to characteristic reaction conditions, additives, and catalysts for producing nitrilotriacetate by reacting triethanolamine in the presence of an alkali metal hydroxide.

The production of sodium nitrilotriacetate from triethanolamine proceeds according to reaction formula [1] shown below, and the production of nitrilotriacetic acid from sodium nitrilotriacetate proceeds according to reaction formula [2], for example.

N(CH ₂ CH ₂ OH) ₃ +3NaOH water, catalyst――――→ N(CH ₂ COONa) ₃ +6H ₂ …(1) N(CH ₂ COONa) ₃ +3/2H ₂ SO ₄ →N(CH ₂ COOH) ₃ +3
/2Na ₂ SO ₄ ...(2) Due to its excellent chelating ability, nitrilotriacetate is used as a water softener, scouring aid, dyeing aid, paper coating agent, scale inhibitor, detergent builder, and soap deterioration inhibitor. It is used in a wide range of fields such as

Today, the Stretzker process, which uses hydrocyanic acid and formaldehyde as main raw materials, is generally known as an industrial method for producing nitrilotriacetates. 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 nitrilotriacetate by oxidative dehydrogenation of triethanolamine in caustic alkali is disclosed in US Pat. No. 2,384,816 and US Pat.
3535373, U.S. Patent No. 3578709, U.S. Patent No.
It is disclosed in No. 3739021 etc. US Patent No.
Example 5 of No. 2384816 discloses a method of reacting triethanolamine potassium hydroxide without a catalyst, but the reaction time is long and the conversion rate is low. U.S. Patent No. 3535373, U.S. Patent No.
No. 3,578,709 and US Pat. No. 3,739,021 disclose methods using cadmium oxide as a catalyst, and the highest yield of nitrilotriacetic acid in these examples is 87.8%. Furthermore, Example 6 of US Pat. No. 3,578,709 discloses a method using zinc oxide as a catalyst, but the reaction time is long and the yield of nitrilotriacetic acid is 77.3%, which indicates that the catalyst activity is inferior to that of cadmium oxide. There is.

As described above, in the conventional technology, the yield is too low in reactions without catalyst or using zinc oxide as a catalyst, and in the reaction using cadmium oxide as a catalyst, there is a risk that cadmium compounds, which are toxic substances, may be mixed into the reaction product. Because of this, it cannot be used at all for some purposes, and it causes major social problems if it flows into rivers as wastewater, so until now it has not been able to become a technology that can compete with the Stretzker method.

As a result of intensive research into the oxidative dehydrogenation method of triethanolamine as a method for producing nitrilotriacetate that can be used as an alternative to the Stretzker method, the present inventors found that it is possible to produce nitrilotriacetate without using cadmium compounds that have toxicity problems. We have discovered a new method for producing nitrilotriacetate in high yield and completed the present invention.

The present invention relates to a method for producing nitrilotriacetate, which is characterized by reacting triethanolamine with an alkali metal hydroxide, water, and copper in the coexistence of a zirconium-containing catalyst.

A feature of the present invention is that when producing nitrilotriacetate from triethanolamine, a safe catalyst containing copper and zirconium is used without using a cadmium catalyst.

Even if the copper-containing catalyst is not supported on zirconium oxide, the yield of nitrilotriacetate can be made 89 to 93 mol% based on triethanolamine by using it under very mild conditions of 140 to 220°C. However, the catalyst containing copper and zirconium not only has improved heat resistance and longer catalyst life, but also has improved selectivity and catalytic activity.
It became possible to achieve a yield of nitrilotriacetate of 91 to 94 mol% and a reduction in reaction temperature of 10 to 20°C. By carrying out the present invention, it has become possible to improve the yield of nitrilotriacetate, shorten the reaction time, and use milder reaction conditions as compared to conventional methods. As a result, it is possible to significantly reduce the manufacturing cost of nitrilotriacetate,
This work has completed an innovative method for producing nitrilotriacetate using oxidative dehydrogenation of triethanolamine, which is easy to implement industrially.

In one embodiment of the present invention, the catalyst used in the method of the present invention contains copper and zirconium as essential components. The catalyst is as it is.
Alternatively, it can be used by being 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 triethanolamine.

The copper- and zirconium-containing catalyst of the present invention uses nitrate as a raw material compound of copper or zirconium,
Examples include inorganic salts such as sulfates, carbonates, oxides, halides, and hydroxides, and organic salts such as acetates, oxalates, citrates, and lactates. In particular, highly water-soluble salts are preferred.

Although the form of the catalyst is not particularly limited, an alkaline aqueous solution is added to a solution of a copper compound and a zirconium compound dissolved in water to precipitate the hydroxide, the precipitate is washed with water, and after drying, it is exposed to air or oxygen. Copper- and zirconium-containing catalysts that have been oxidized in a hydrogen atmosphere and then reduced in a hydrogen atmosphere are preferred. Moreover, a catalyst in which zirconium oxide is impregnated with an aqueous solution of a copper compound, dried, oxidized in air or oxygen, and then reduced in a hydrogen atmosphere and supported on zirconium oxide is 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 is used to form a homogeneous system of triethanolamine and alkali metal hydroxide.
The reaction conditions can be made mild, which is essential for obtaining a high yield of nitrilotriacetate. 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 triethanolamine.

The alkali metal hydroxide used in the present invention includes lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Among these, sodium hydroxide and potassium hydroxide are particularly preferably used. The amount of alkali metal hydroxide used is at least an equivalent equivalent to the conversion rate of triethanolamine used in the reaction, preferably in the range of 1.0 to 2.0 equivalents. As the alkali metal hydroxide, any of flakes, powder, pellets, etc. and aqueous solutions thereof can be used, but aqueous alkali metal solutions are generally preferably used because they are convenient in terms of handling.

Triethanolamine is preferably of high purity in order to avoid contamination of the nitrilotriacetate with impurities. Although there are no particular limitations on the purity, a purity of 96% by weight or more, preferably 99% by weight or more is used.

The reaction temperature is usually 220°C or lower to prevent thermal decomposition and hydrogenolysis of the C-N bond of triethanolamine and the C-N bond of nitrilotriacetate.
The temperature range is 140-220°C, preferably 150-200°C. Also, copper and zirconium catalysts
Temperatures exceeding 220°C will cause some of the surface to sinter, reducing the surface area and reducing catalyst activity. Therefore, if the catalyst is used repeatedly,
Temperatures below 0 C are more preferred.

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 180° C., reaction pressure of 10 Kg/cm ² G, and a catalyst amount of 10% by weight based on triethanolamine, the reaction time is 5 to 7 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 triethanolamine and the selectivity of nitrilotriacetate are derived from the following equation.

Conversion rate of triethanolamine (%) = Number of moles of triethanolamine reacted/Number of moles of triethanolamine subjected to reaction x 100 Selectivity of nitrilotriacetate (%) = Number of moles of nitrilotriacetate produced/ Number of moles of reacted triethanolamine x 100 Example 1 Add water to a solution of 74.5 g of triethanolamine, 63.0 g of sodium hydroxide, 137.5 g of water, and 24.8 g of zirconium oxychloride and 4.0 g of copper nitrate as catalysts dissolved in 300 ml of water. Copper and zirconium obtained by adding an aqueous sodium oxide solution to precipitate hydroxide, washing the precipitate with water, drying, heating in air at 500°C for 3 hours, and reducing in a hydrogen stream at 230°C for 6 hours. After charging 7.5 g of the catalyst contained in a 500 ml autoclave and purging the inside with hydrogen gas three times,
The reaction was carried out at a reaction temperature of 180° C. and a reaction pressure of 9 kg/cm ² G until no hydrogen was generated. The time required for the reaction was 5.5 hours after the temperature was raised to 180°C. After the reaction was completed, the reaction solution was taken out and analyzed.
The conversion rate of triethanolamine was 98.4 mol%, and the selectivity of nitrilotriacetate was 95.4 mol%.

Example 2 74.5 g of triethanolamine, 63.0 g of sodium hydroxide, 137.5 g of water, and as a catalyst, 10 g of zirconium oxide was impregnated with an aqueous solution containing 4.2 g of copper nitrate, and after drying, heat treated in air at 500°C for 3 hours. , 7.5 g of a catalyst in which copper supported on zirconium oxide was obtained by reduction treatment at 230°C in a hydrogen stream for 6 hours.
was charged into a 500 ml autoclave, and after the interior was purged with hydrogen gas three times, the reaction was carried out at a reaction temperature of 180° C. and a reaction pressure of 9 Kg/cm ² G until no hydrogen was generated. The time required for the reaction was 6 after raising the temperature to 180℃.
It was time. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of triethanolamine was 98.0 mol%, and the selectivity of nitrilotriacetate was
It was 94.2 mol%.

Example 3 In order to check the repeated activity of the catalyst, repeated experiments were conducted under the same reaction conditions as in Example 1.
The reaction time required for the 10th reaction was 6.5 hours after the temperature was raised. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of triethanolamine was 97.3.
The selectivity for nitrilotriacetate was 93.5 mol%.

Claims (1)

[Claims] 1. A method for producing nitrilotriacetate, which comprises reacting triethanolamine with an alkali metal hydroxide, water, and copper in the coexistence of a zirconium-containing catalyst.