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[Chemical Knowledge]：Production process and preparation method of hydroquinone

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Hydroquinone is an important organic compound, widely used in medicine, dyes, synthetic resins and other fields. This article will introduce the production process and preparation method of hydroquinone.

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1. process flow
the production process of hydroquinone usually includes the steps of nitration, reduction, acidification and crystallization of phenol. The specific process flow is as follows:

nitration of 1.1 phenol
the phenol is dissolved in nitric acid and reacted at 350-400 ° C. to obtain a mixture of p-nitrophenol and o-nitrophenol.
1.2 reduction
A mixture of p-nitrophenol and o-nitrophenol is reduced to hydroquinone. The reducing agent is typically sodium sulfite or a sodium sulfite-iron sulfate complex.
1.3 acidification
the reduced hydroquinone is isolated by crystallization under acidic conditions.
1.4 Crystal
by gradually increasing the temperature of crystallization, impurities are removed, and hydroquinone with a purity of more than 98% is obtained.

2. preparation method
there are a variety of preparation methods of hydroquinone, commonly used are the following:
preparation of 2.1 by hydrogenation
hydroquinone is obtained by reacting phenol with hydrogen in the presence of a copper-based catalyst.
Preparation of 2.2 by bromination
phenol and bromine are reacted under the catalysis of ferric chloride to obtain p-bromophenol, which is then reduced by zinc to obtain hydroquinone.
2.3 activated carbon adsorption method
the phenol solution is passed into an adsorption column equipped with activated carbon to remove impurities and obtain hydroquinone.

3. process optimization
in order to improve the yield and purity of hydroquinone, the following optimization measures can be taken:
3.1 Optimized Catalyst
the use of highly active, highly selective catalysts improves reaction efficiency and product purity.
3.2 optimization of reaction conditions
the reaction temperature, reaction time and ratio of reactants were optimized to improve the yield and purity.
3.3 optimization of crystal separation
the impurities were removed and the purity of hydroquinone was improved by suitable crystal separation method.

4. application prospect
hydroquinone is widely used in medicine, dyes, synthetic resins and other fields. In the field of medicine, hydroquinone can be used to prepare analgesics, anti-tuberculosis drugs, etc. In the field of dyes, hydroquinone can be used to prepare mordants for printing and dyeing. In the field of synthetic resins, hydroquinone can be used to prepare phenolic resins, phenolic plastics, etc.

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