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[Chemical Knowledge]：Production process and preparation method of p-hydroxybenzoic acid

Read： 1276 Time：17months ago Source：Transform the World with Simplicity

p-Hydroxybenzoic acid is a very important chemical, widely used in pharmaceuticals, dyes and pigments and other industrial fields. This article will introduce the production process and preparation method of p-hydroxybenzoic acid, so that readers can better understand the production process of p-hydroxybenzoic acid.

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1. p-hydroxybenzoic acid can be obtained by the hydrogenation and oxidation reaction of benzoic acid, the reaction raw materials are benzoic acid and oxygen, and the catalyst is cobalt, manganese, copper and other metals. The reaction conditions are as follows: the temperature is 150-200 ° C., the oxygen gas pressure is 0.5-1.5MPa, and the reaction time is 5-10 hours. The product was p-hydroxybenzoic acid, and the yield was over 70%.

2. p-hydroxybenzoic acid can also be obtained by chemical reaction of phenyl, methyl and hydroxyl. The reaction materials are benzene, formaldehyde and sodium hydroxide. Benzene and formaldehyde were first methylated under the catalysis of copper oxide to obtain benzaldehyde. Benzaldehyde is then reacted with sodium hydroxide to give p-hydroxybenzoic acid. The reaction conditions are as follows: the reaction temperature is 60-80 ° C., and the reaction time is 12-16 hours. The product is p-hydroxybenzoic acid, and the yield can reach more than 85%.

3, p-hydroxybenzoic acid can also be prepared by the reaction of aniline and nitric acid. The reaction materials are aniline and nitric acid, and the catalyst is sulfuric acid. The reaction conditions are: the temperature is 20-40 DEG C, the reaction time is 2-4 hours. The product is p-hydroxybenzoic acid, and the yield can reach more than 90%.

The above three methods are common methods for preparing p-hydroxybenzoic acid. Among them, the first method has a higher yield and is suitable for industrial production; the second method has a simpler operation and is suitable for laboratory preparation; the third method has the highest yield, but requires a higher purity of raw materials.
In short, the production process and preparation methods of p-hydroxybenzoic acid are diverse, and choosing a suitable method can improve the yield and efficiency. I hope this article is helpful to you.

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