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[Chemical Knowledge]：Propylene glycol diacetate production method and process flow

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Propylene glycol diacetate (Propylene Glycol Diacetate, referred to as PGDA) is a kind of organic compounds widely used in chemical, pharmaceutical, food and other fields. As an important chemical raw material, the manufacturing method of propylene glycol diacetate has attracted much attention. This paper will introduce the manufacturing method of propylene glycol diacetate in detail, including raw material preparation, reaction process, post-treatment and so on.

1. Raw Material Preparation

The main raw materials for the manufacture of propylene glycol diacetate are propylene glycol and acetic anhydride. Propylene glycol is a colorless, tasteless, transparent, viscous liquid with strong moisture absorption and moisture retention. Acetic anhydride is a colorless transparent liquid, irritating and corrosive. In the preparation of propylene glycol diacetate, it is necessary to mix propylene glycol and acetic anhydride in a certain molar ratio.

2. reaction process

propylene glycol and acetic anhydride reaction process needs to be carried out under the action of a certain temperature and catalyst. First, propylene glycol and acetic anhydride are added to the reactor according to a certain ratio, and then heated to a certain temperature. At this temperature, acetic anhydride will be esterified with propylene glycol to form propylene glycol diacetate and water.

In order to promote the reaction, it is necessary to add a certain catalyst. Commonly used catalysts include acidic catalysts such as sulfuric acid and p-toluenesulfonic acid. Under the action of the catalyst, the reaction rate is accelerated, and the conversion rate of propylene glycol and acetic anhydride is increased.

During the reaction, the acidity and temperature of the reaction solution need to be constantly monitored to maintain the stability of the reaction. At the same time, it is also necessary to discharge the water generated by the reaction in time to promote the reaction to the direction of generating propylene glycol diacetate.

3. post-treatment

After the reaction is completed, the reaction solution needs to be post-treated to obtain pure propylene glycol diacetate. First, it is necessary to cool the reaction liquid to room temperature, and then add an alkaline absorbent to neutralize the remaining acid catalyst. Commonly used alkaline absorbents include sodium hydroxide, potassium hydroxide, etc.

Next, the reaction solution needs to be distilled to separate propylene glycol diacetate and other impurities. In the distillation process, it is necessary to select appropriate distillation temperature and pressure conditions according to the difference between the boiling point of propylene glycol diacetate and the boiling point of other impurities to ensure the purity and yield of propylene glycol diacetate.

Finally, the quality inspection of the distilled propylene glycol diacetate is required to ensure that it meets the relevant standards and requirements. Inspection items include purity, acidity, moisture, color and other indicators.

In short, the manufacturing method of propylene glycol diacetate includes raw material preparation, reaction process and post-treatment. In the preparation process, it is necessary to control the reaction conditions and post-treatment process to ensure the purity and yield of the product.

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