Production principle and process flow of m-aminobenzene sulfonic acid

Metanilic acid (m-aminobenzenesulfonic acid), also known as aniline-sulfonic acid, 3-amino-acid , of the formula C _.
6 H _.
7 NO _.
3 S, molecular weight of 173.
19, the formula

1.
Product performance

White flake crystals; relative density 1.
69; solubility in water at 16.
8℃ is 2.
37%, slightly soluble in ethanol and ether , soluble in concentrated hydrochloric acid; decomposes on hot
.

2.
Production principle

Nitrobenzene is sulfonated with fuming sulfuric acid and then neutralized into salt by alkali, then reduced with iron filings, and the reduced product is filtered and acidified to obtain m-aminobenzenesulfonic acid
.

3.
Process flow

4.
Technical formula (kg/t)

5.
Main equipment

Sulfonation reactor, filter, reduction reaction pot, acid precipitation pot, centrifuge, storage tank
.

6.
Production process

Add 1500L 20% fuming sulfuric acid into the acid boiler at a rate of 500L/h, and keep the temperature around 250℃
.

In the reduction reaction pot, add 1/5 of the above sulfonated diluent (not neutralized with liquid caustic soda) and 660 kg of iron filings
.

The sodium salt solution is acidified by adding sulfuric acid in the acidification pot until the Congo test paper turns blue, and the temperature is maintained at 70°C
.

7.
Product Standard

8.

Determination of total amino content: Weigh about 0.
5g of m-aminobenzene sulfonic acid sample, weigh to 0.
001g, transfer it into a 600mL beaker to dissolve it, add 30mL of concentrated hydrochloric acid (density 1.
19g/cm ² ) and 300mL of distilled water, When cooled to 10～15℃, add 10 mL of 10% potassium bromide solution, titrate with 0.
2mol/L sodium nitrite standard solution, and test the end point with potassium iodide starch test paper
.

Where: V—the volume of sodium nitrite solution consumed by the sample, mL;

V ₁ ——The volume of sodium nitrite solution used in the blank experiment, mL;

c—The molar concentration of sodium nitrite solution for titration, mol/L;

G——The mass of the sample, g
.

9.

Mainly used in the manufacture of azo dyes and sulfur dyes, such as weak acid dark blue 5R, GR, acid golden G, reactive brilliant orange KG, K-GN, KR, K-7R, etc.
, also used in the manufacture of fluorescent self-enhancing agent B, Tianlai Stilbene fluorescent brighteners such as Bao 2B and Blankophor BBU
.

10.
Security measures

(1) The raw material nitrobenzene, the intermediate meta-nitrobenzene sulfonic acid and the products are all toxic, and fuming sulfuric acid is used.
The equipment should be sealed to prevent leakage.
The operators should wear protective equipment and the workshop should be well ventilated
.

(2) Packed in iron drum lined with plastic bag, sealed and protected from light and stored in a cool and ventilated place to prevent heat, sun and moisture
.