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[Chemical Knowledge]：Manufacturing method and process of polyethylene glycol

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Polyethylene glycol (Polyethylene Glycol, referred to as PEG) is a widely used chemical products, can be used as solvents, emulsifiers, wetting agents and so on. In the field of chemical production raw materials, there are two main manufacturing methods of polyethylene glycol: chloroethanol method and ethylene oxide method. This article will detail these two manufacturing methods.

1. Chloroethanol method

Chloroethanol method is a kind of chloroethanol as raw material, through the action of alkaline catalyst, intramolecular dehydration reaction to generate ethylene oxide, and then ethylene oxide and water reaction to generate polyethylene glycol method. The specific steps are as follows:

1. preparation of chloroethanol: chlorine gas is introduced into ethanol to react to generate chloroethanol. The reaction is exothermic and the reaction temperature needs to be controlled to avoid the formation of by-products.
2. Ethylene oxide preparation: under the action of alkaline catalyst, chloroethanol undergoes intramolecular dehydration reaction to generate ethylene oxide. Commonly used alkaline catalysts include sodium hydroxide, potassium hydroxide, etc.
3. polyethylene glycol preparation: ethylene oxide and water are mixed according to a certain proportion, under the action of acidic or alkaline catalyst, ring-opening polymerization reaction to generate polyethylene glycol. The type and amount of catalyst have an effect on the molecular weight and molecular weight distribution of polyethylene glycol.

chloroethanol method has the advantages of easy access to raw materials and simple process, a large amount of waste water and waste gas will be produced in the production process, which will cause certain pollution to the environment.

2. ethylene oxide method

ethylene oxide method is a kind of ethylene oxide as raw material, reaction with water to generate polyethylene glycol method. The specific steps are as follows:

1. Preparation of ethylene oxide: ethylene oxide is prepared by ethylene oxidation method, and the commonly used oxidant is oxygen or air.
2. Preparation of polyethylene glycol: ethylene oxide and water are mixed according to a certain proportion, and the ring-opening polymerization reaction is carried out under the action of acidic or alkaline catalyst to generate polyethylene glycol. The reaction temperature and pressure have an effect on the molecular weight and molecular weight distribution of polyethylene glycol.

ethylene oxide method has the advantages of single raw material and high product quality, which is commonly used in industrial production. However, there are still safety hazards and environmental pollution problems in the production process of this method, which need to be further improved and perfected.

In addition to the above two methods, there are some new polyethylene glycol manufacturing methods are being researched and developed, such as enzymatic catalysis, microbial methods, etc. These methods have the advantages of environmental protection and high efficiency, and are expected to replace the traditional methods as the mainstream production methods in the future.

In short, polyethylene glycol is an important raw material for chemical production, and its manufacturing methods are continuously developed and improved to improve product quality, reduce production costs, and reduce environmental pollution. In the future, with the continuous progress and application of science and technology, it is believed that the manufacturing method of polyethylene glycol will be more environmentally friendly, efficient and sustainable.

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