JPH01163161A - Production of diisopropylammonium nitrite - Google Patents

Abstract

PURPOSE:To obtain the title compound useful as a volatile rust preventive agent from diisopropylamine sulfate and sodium nitrite in high quality and yield, by removing Glauber's salt and concentrating the resultant reaction solution under reduced pressure and specific conditions. CONSTITUTION:Diisopropylamine sulfate is reacted with sodium nitrite to provide diisopropylammonium nitrite. In the process, Glauber's salt formed as a by-product is removed and the resultant reaction solution is concentrated under reduced pressure while being kept at <=60 deg.C, preferably <=50 deg.C and pH7.0-9.5 to deposit the aimed substance. An alkali (e.g., NaOH, KOH or Na2CO3) is used for controlling the pH. Formation of nitrosamine can be suppressed by the abovementioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing high-yield and high-quality diisopropylammonium nitrite.

[Prior art] Diisopropylammonium nitrite (hereinafter referred to as DIP)
AN) is known as a volatile rust inhibitor and is used alone or together with other rust inhibitors as a corrosion inhibitor for steel products and other metal products.

DIPAN was generally manufactured as follows.

That is, a sodium nitrite aqueous solution is added to a diisopropylamine sulfate aqueous solution to obtain a D I PAN reaction solution. This reaction solution contains mirabilite as a by-product, so after cooling it, the mirabilite is removed by filtration. After the removal of mirabilite, the reaction solution is concentrated under reduced pressure to precipitate D I PAN crystals, which are then filtered and washed. After drying, D I PAN was obtained, while the filtrate was returned to the reaction solution and used again.

[Problems to be Solved by the Invention] However, the above-mentioned production method has problems such as a low yield of D I PAN and an inability to obtain a product of high quality.

Therefore, the present inventors have developed a method for producing high-yield and high-quality DIPA.
We investigated a manufacturing method that can obtain N.

[Means for Solving the Problems] The present invention has solved the above problems. When producing diisopropylammonium nitrite by reacting diisopropylamine sulfate and sodium nitrite,
After removing the by-product Glauber's salt, the reaction solution was heated to a temperature of 60°C or less.
The gist of the composition is to precipitate diisopropylammonium nitrite by concentrating under reduced pressure while maintaining the pH at 7.0 to 9.5.

[Function] As a result of intensive research by the present inventors regarding the above-mentioned problems,
It has been found that the above-mentioned problems occur due to the following factors.

In other words, if the reaction solution is left in a high temperature state after removing the mirabilite produced as a by-product in the reaction solution, the nitrous acid in the reaction solution will be oxidized to produce nitric acid, and as a result, the pH will drop and nitrosamines will be produced. do. This reaction progresses at an accelerated rate once it begins to proceed, and moreover, the reaction progresses more markedly as the temperature and acidity increase. Tables 1 and 2 and FIG. 1 show the results of tests on the influence of pH or temperature on the production of nitrosamines in the filtrate after the removal of Glauber's salt, that is, the DIPAN solution.

From Table 1, Table 2, and Figure 1, the pH of the reaction solution was 7.0.
~9.5. It can be seen that it is important to keep the temperature below 60°C.

Table 1: Effect of pH on nitrosamine production (DI
PAN 25% aqueous solution, 60°C, 72 hours) Table 2: Effect of temperature on nitrosamine formation (DIPANIO%
(Aqueous solution, pH 7.0) As a result of further investigation of this phenomenon, the temperature of the reaction solution after removing the by-produced mirabilite was set to 60°C.
It has been found that the production of nitrosamines can be suppressed by preferably maintaining the temperature at 50° C. or lower and controlling the pH to 7.0 to 9.5 by adding an alkali. At this time, pH 7
If the pH is less than 0, there is no effect of inhibiting the production of nitrosamines, and if the pH exceeds 9.5, it becomes difficult to precipitate D I PAN. Also, if the liquid temperature exceeds 60℃, the pH will change.
The adjustment effect will be lost.

Examples of the alkali for maintaining the pH of the reaction solution at 7.0 to 9.5 include sodium hydroxide, potassium hydroxide, and sodium carbonate.

[Example] Example (1) 515 g of 39.2% diisopropylamine aqueous solution was placed in a beaker 11 equipped with a stirring blade, and 200 g of 50% sulfuric acid was added dropwise over about 30 minutes while cooling with water. After adding 380 g of an aqueous sodium nitrate solution and stirring for 3 hours, the mixture was cooled in a 5° C. cold bath for about 15 hours. The precipitated Glauber's salt was filtered, the Glauber's salt was washed with methanol, and the washing liquid was combined with the filtrate. The weight of the liquid after coalescence was 1086 g, and the weight of the recovered Glauber's salt was 265 g. The pH of the filtrate was 8.6.

The filtrate was charged into a four-loaf flask equipped with stirring blades, and while the liquid temperature was kept at about 50°C in a hot bath, a 2.5% aqueous sodium hydroxide solution was added at a rate of 1.8 mρ/min to adjust the pH to 8.6~
While maintaining the temperature at 7.5, the solution was concentrated under reduced pressure until the liquid weight became 450 g. After filtering the precipitated crystals and washing with acetone,
It was dried at 0° C. to obtain 130 g of DIPAN with a purity of 98.0%. The pH of the filtrate at this time was 8.3, and the conversion rate was 43.
．． It was 0%.

(2) Furthermore, 542 g of the final filtrate obtained in (1) above was added to 1095 g of the reaction solution obtained under the same conditions as in (1) above, and the mixture was cooled to remove the precipitated by-product Glauber's salt. The weight of mirabilite is 349
It was g. The pH of the filtrate after removal of Glauber's salt was 9.1, and the weight of the liquid was 1140 g. Further, under the same conditions as in (1) above, a 2.5% aqueous sodium hydroxide solution was added to adjust the pH to 9.
6 to 7.5, concentrated under reduced pressure until the liquid weight was 662 g, and the precipitated crystals were filtered, washed, and dried to a purity of 98.
．． 270 g of 5% D I PAN was obtained. The pH of the filtrate at this time was 8.0, and the conversion rate was 90%.

(1) pH 8 after removing mirabilite in the same manner as in Example (1)
, 1100 g of the filtrate of No. 4 was concentrated under reduced pressure to a liquid volume of 460 g without adding an alkali while maintaining the temperature at about 50°C.

The precipitated crystals were filtered, washed, and dried to obtain 4 g of D I PAN with a purity of 97.0%.

The conversion rate at this time was 16.1%, and the filtrate pH was 5.7.
Met.

(2) Reaction liquid obtained by the same operation as in Example (2). After adding the final filtrate of Comparative Example (2) and cooling it, filtering out the precipitated Glauber's Salt, 1210 g of the filtrate, pH 8.4, was heated to Approximately 5
D I PAN 1 with a purity of 95.0% is obtained by concentrating under reduced pressure while maintaining the temperature at 0°C without adding alkali until the liquid volume reaches 585 g.
56g was obtained. The conversion rate at this time was 50%, and the filtrate p
H was 5.8.

Table 3 shows the results of Examples and Comparative Examples.
As is clear from Table 3, it can be seen that according to the Examples, products with higher purity can be obtained in higher yields than in the Comparative Examples in which no pH adjustment is performed. In particular, when comparing the conversion rates of Example (1) and Comparative Example (1), and the conversion rates of Example (2) and Comparative Example (2), the conversion rates of Example (1) and (2) are higher. It can be seen that this has improved.

[Effects of the Invention] Since the present invention is configured as described above, according to the present invention, highly purified diisopropylammonium nitrite can be produced at a high yield.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the influence of temperature and time on the production rate of nitrosamines.

Claims (1)

[Claims] When producing diisopropylammonium nitrite by reacting diisopropylamine sulfate and sodium nitrite, the reaction solution after removing the by-produced mirabilite is heated to a temperature of 60°C.
A method for producing diisopropylammonium nitrite, which comprises precipitating diisopropylammonium nitrite by concentrating it under reduced pressure while keeping the pH at 7.0 to 9.5.