Process for synthesizing naphthol through indirect sulfonation reaction of sulfur trioxide

Abstract

The invention discloses a process for synthesizing naphthol through indirect sulfonation reaction of sulfur trioxide, which comprises the following steps: dropwise adding excessive sulfuric acid into refined naphthalene, generating naphthalene sulfonic acid through sulfonation reaction, and completely reacting naphthalene; carrying out melt crystallization on the sulfonation reaction product to obtain refined naphthalene sulfonic acid and crystallized sulfuric acid mother liquor; introducing sulfur trioxide gas into the crystallized sulfuric acid mother liquor, reacting sulfur trioxide with water to generate sulfuric acid, using the sulfuric acid for a sulfonation reaction, and realizing indirect sulfonation reaction with sulfur trioxide as the raw material; adding molten refined naphthalene sulfonic acid into a sodium sulfite mother solution, neutralizing to obtain sodium naphthalene sulfonate and sulfur dioxide, acidifying by using sulfur dioxide, carrying out alkali fusion, acidifying and rectifying to obtain 1-naphthol and 2-naphthol, and finally recovering sodium sulfite. The content of sulfuric acid in refined naphthalene sulfonic acid obtained through melt crystallization is extremely low, and the influence of sodium sulfate impurities on the alkali fusion process and the quality of byproduct sodium sulfite is avoided. In the process, the utilization rate of the raw materials naphthalene and sulfur trioxide is high, high-salt-content organic wastewater is not generated, and clean production is realized.

Description

technical field [0001] The invention relates to the technical field of organic synthesis, in particular to a process for synthesizing naphthol through indirect sulfonation reaction of sulfur trioxide. Background technique [0002] 1-Naphthol is commonly known as methylnaphthol, also known as α-naphthol, and it is currently mainly used as an intermediate of the pesticide carbaryl, and it can also be used as an intermediate of some drugs and fine chemical products. The main production processes of 1-naphthol are sulfonation and nitration. The sulfonation method is low-temperature sulfonation of naphthalene and sulfuric acid, and then neutralization, alkali dissolution, acidification, and rectification to obtain 1-naphthol. Since the isomers produced by sulfonation need to be removed, the product yield is low, about 40%. , The discharge of three wastes is large. The nitration method is a naphthalene nitration, reduction, and hydrolysis process. Due to the nitration reaction, ...

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Problems solved by technology

The sulfonation method is low-temperature sulfonation of naphthalene and sulfuric acid, and then neutralization, alkali dissolution, acidification, and rectification to obtain 1-naphthol. Since the isomers produced by sulfonation need to be removed, the product yield is low, about 40%. , the discharge of three wastes is large

The nitration method is a naphthalene nitration, reduction, and hydrolysis process. Due to the nitration reaction, about 4% of 2-nitronaphthalene is produced, and the general product content is about 96%. The superior product 1-naphthol needs to be separated and purified by nitronaphthalene crystallization or product Crystallization and separation, long steps, high cost, and many wastes

[0003] 2-naphthol is commonly known as ethyl naphthol, also known as β-naphthol, widely used as dyes, pigments and pharmaceutical intermediates, using naphthalene and concentrated sulfuric acid at high temperature for sulfonation, hydrolysis, hydrolysis blowing naphthalene, neutralization, cooling and crystallization , filtration, alkali fusion, acidification, boiling and rectification. The 1-naphthol isomer produced in the sulfonation process is removed by hydrolysis. The production process is mature, but a large amount of high-salt organic wastewater is produced, which is difficult to treat. Big pollution

In order to maintain the reactivity, the most traditional process 1 promotes the reaction to the positive direction by adding a large excess of sulfuric acid, and try to completely react the naphthalene. The problem with this process is that a large amount of liquid caustic soda must be added to neutralize the excess Sulfuric acid, then add the sodium sulfite mother liquor that acidification process generates, naphthalenesulfonic acid and sodium sulfite react to generate sodium naphthalenesulfonate and sulfur dioxide (sulfur dioxide circulation deacidification process), obtain solid sodium naphthalenesulfonate through cooling crystallization, filtration, due to neutralization in the mother liquor Contains a large amount of sodium sulfate, the solid sodium naphthalenesulfonate obtained by filtration will contain more sodium sulfate, put the naphthalenesulfonic acid into the alkali melting pot and carry out alkali melting at about 300°C, and the solid sodium naphthalenesulfonate will bring more sulfuric acid On the one hand, sodium will quickly corrode the alkali melting pot. On the other hand, due to the high melting point of sodium sulfate, the sodium sulfate in the alkali melting pot will exist in solid form, which will affect the operation of alkali melting in the future.

The biggest problem of this production process is that the secondary sulfonation directly feeds sulfur trioxide into the sulfonation reaction system. chemical reaction, so as to promote the reaction to proceed in the positive direction

But in fact because the reactivity of sulfur trioxide is extremely high, directly pass into sulfur trioxide in the sulfonation reaction system, sulfur trioxide can directly react with the naphthalene in the sulfonation reaction system and generate a large amount of polysulfonic naphthalene, which is also The reason why the production process of naphthol cannot use sulfur trioxide as raw material for direct sulfonation reaction

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