JPS632256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 2,4-diaminobenzenesulfonic acid, and more specifically, water is added to a sulfonation reaction mass obtained by direct sulfonation of metadiaminobenzene, 2,4-diaminobenzene produced as a by-product by heating to
1,5-disulfonic acid (hereinafter referred to as disulfonic acid) is demonosulfonated to obtain the desired 2,4-
This is an improved method for producing monosulfonic acid, which involves converting it into diaminobenzenesulfonic acid (hereinafter referred to as monosulfonic acid).

Conventionally, the manufacturing method for monosulfonic acid is 2.4.
- A well-known method is to use dinitrochlorobenzene as a raw material, convert the chloro group into a sulfonic acid group with sulfite, and then reduce the nitro group. Although this method yields a highly pure product, the reaction process is long; Furthermore, since an organic solvent is used, there are various difficulties in waste liquid treatment.

Also known is a method of directly sulfonating metadiaminobenzene with fuming sulfuric acid or the like. This method has shorter reaction steps and is more operationally advantageous than the former, but disulfonation also occurs at the same time as monosulfonation, and the reactant is a mixture of both, so if the reaction conditions are weakened to suppress disulfonation, Not only does the reaction not proceed sufficiently, resulting in a decrease in the yield of monosulfonic acid, but also disulfonation cannot be eliminated. In addition, it is not easy to separate and purify the mono- and disulfonic acid mixture obtained in this way both in terms of equipment and operation, and it is disadvantageous for industrial implementation.

The present inventor has investigated various industrially advantageous methods for producing monosulfonic acid, and in the direct sulfonation method of metadiaminobenzene, the by-product disulfonic acid is converted to the target monosulfonic acid from the sulfonation reaction mass. Noting that it could be an extremely advantageous production method if it could be converted, further study revealed that disulfonic acid begins to be produced as a by-product from the early stage of the reaction in the direct sulfonation of metadiaminobenzene, and most of the reaction raw materials disappear. At the end of the reaction, an amount reaching approximately 30% is produced, but by adding water to the sulfonated reaction mass and heating it to 120-150°C, demonosulfonation of disulfonic acid occurs, converting disulfonic acid to monosulfonic acid. It has been discovered that this can be converted, leading to the present invention.

That is, the present invention is a method for producing monosulfonic acid, which comprises adding water to a sulfonation reaction mass of metadiaminobenzene and keeping the mixture at a temperature of 120 to 150°C.

According to the present invention, one of the by-produced disulfonic groups is eliminated and becomes the target monosulfonic acid, and as a result, the amount of disulfonic acid in the reaction mass decreases, and the amount of monosulfonic acid increases. Good yields exceeding % can be obtained.

The present invention will be explained in detail below.

In the present invention, the sulfonation reaction mass refers to the mass obtained by direct sulfonation reaction of diaminobenzene, but when carrying out the sulfonation reaction, it is preferable to dissolve diaminobenzene in 98 to 100% sulfuric acid in advance. In this case, the amount of sulfuric acid used is preferably at least 5 times the weight of diaminobenzene.

As a sulfonating agent, various concentrations of oleum, chlorosulfonic acid, etc. can be used, but when using oleum, a low concentration of oleum is disadvantageous because it requires a large amount of use and a significant amount of waste acid is emitted. For this reason, it is preferable to use 65% oleum.

In addition, various reaction conditions such as reaction temperature and reaction time are carried out using conventionally known methods.

Demonosulfonation is carried out by adding water to the reaction mass obtained in this way, but since the addition of water causes severe heat generation, the reaction mass is usually heated in advance to a temperature of about 130 to 140°C, which is the temperature at which crystals do not precipitate. After cooling, slowly add water.

The amount of water added to the reaction mass is such that the sulfuric acid concentration in the reaction mass is 60-90%, preferably 70-85%.

The demonosulfonation temperature is preferably in the range of 120 to 150°C. At temperatures lower than this, crystallization of the reactants occurs and the reaction becomes extremely slow and disulfonic acid remains, while at temperatures higher than this, partial decomposition occurs and the yield tends to decrease. The demonosulfonation reaction is completed by keeping the temperature at the above temperature for a predetermined period of time, but after that, water is further added to the reaction mass to lower the sulfuric acid concentration, and by cooling, the desired monosulfonic acid can be obtained as crystals. .

The monosulfonic acid thus obtained contains almost no disulfonic acid and has extremely high purity.

Hereinafter, the present invention will be explained by examples.

Example 1 108 g of metadiaminobenzene was added to a 14-necked flask containing 660 g of 100% sulfuric acid at a temperature below 100°C.
It took some time to add it.

Add 155 g of 65% oleum at 100°C for 10 minutes, and then raise the temperature to 155°C over another hour.

The sulfonation reaction is completed by keeping the temperature at this temperature for 5 hours.

After the reaction is completed, the mixture is allowed to cool, and when the temperature of the contents reaches 130 to 135°, 200 g of water is poured over 1 hour. During this time, keep it at 140℃ while air cooling.

Next, the above reaction solution was poured into two beakers containing 500 g of ice water, cooled to 10°C, and further stirred at this temperature for 1 hour to sufficiently precipitate crystals, and then filtered.

The obtained overcake weighed 246 g.

As a result of analysis by high performance liquid chromatography, the content of 2,4-diaminobenzenesulfonic acid in the cake was 71%, the content of terminally reacted metadiaminobenzene was 0.1% or less, and the content of 2,4-diaminobenzenedisulfonic acid was 71%. It was not recognized. The yield of 2,4-diaminobenzenesulfonic acid was 93%.

Example 2 108 g of metadiaminobenzene was added to a 1-4-neck flask containing 660 g of 100% sulfuric acid with stirring over a period of about 1 hour. During this time, it was cooled to prevent the temperature from exceeding 100°C.

Add 150 g of chlorosulfonic acid to this mixture starting at 100°C, and the temperature will rise to 145°C over 2 hours, during which time the dropwise addition will be completed. Thereafter, the mixture was kept at 145°C for 2 hours and stirred to complete the sulfonation reaction.

Thereafter, the contents were slowly cooled, and when the temperature reached 135-140°C, 200 g of water was added over 1 hour. During this time, it will generate heat, but it will be cooled to maintain it at 140℃ and kept at that temperature for 1 hour. At this point, when a part of the reaction solution is observed by thin layer chromatography, it is found that the by-product disulfonic acid has disappeared. Then ice water
Pour the reaction solution into 2 beakers containing 500g,
After cooling to 10°C, stir for 1 hour and filter out the precipitated crystals. The obtained wet cake weighed 230 g, and as a result of analysis by high performance liquid chromatography, the content of 2,4-diaminobenzenesulfonic acid was 73.5%, the content of metadiaminobenzene was less than 0.1%, and the content of 2.
4-diaminobenzenedisulfonic acid was not detected.

Comparative Example 1 Metadiaminobenzene was added to a four-necked flask containing 660g of 100% sulfuric acid.
Add 108g in about 1 hour at below 100℃. To this, 155 g of chlorosulfonic acid was added in the same manner as in Example 2, and the reaction was carried out at the same temperature and for the same time to perform a sulfonation reaction.

After sampling a portion of the reaction solution and pulverizing it with water to make 50% sulfuric acid, the crystals that precipitated were analyzed and found to be metadiaminobenzene.
65%, metadiaminobenzenedisulfonic acid, 34%, and trace amounts of metadiaminobenzene.

300 ml of water was added to the reaction solution, which was simultaneously cooled to 110°C. Sulfonic acid began to precipitate and the contents solidified. After this, the temperature was raised to 150°C, but a homogeneous solution could not be obtained. After keeping it warm for 3 hours, the crystals were separated and analyzed, and disulfonic acid was found.
The content was more than 30%, almost unchanged from before desulfonation.

Claims (1)

[Claims] 1. A method for producing 2,4-diaminobenzenesulfonic acid, which comprises adding water to a sulfonation reaction mass of metadiaminobenzene and keeping the mixture at a temperature of 120 to 150°C.