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[Chemical Knowledge]：Production process and preparation method of dioctyl terephthalate DOTP

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Dioctyl terephthalate (DOTP) is an environmentally friendly plasticizer that is widely used in the plastics industry. Its main features are high-efficiency plasticizing effect, good low-temperature performance and excellent oxidation resistance, no harmful substances, and can meet the needs of different fields. In the process of producing DOTP,

adopts efficient technology and preparation methods, which can improve production efficiency, reduce production costs, and enhance product quality stability.

1. Production Process
The production process of
DOTP mainly includes two steps, namely, esterification reaction and separation reaction.

1. Esterification reaction

Esterification reaction refers to the process of obtaining DOTP by esterification reaction between alkanol and terephthalic acid ester. In the reaction, the type and quality of alkanol have an important influence on the reaction rate and product purity.

usually use methanol, isopropanol and other alkanol as the reaction medium, add catalyst such as ammonium sulfate, ferrous chloride, control the reaction temperature and time, accelerate the reaction process. The reaction takes about 5-6 hours. After the reaction is completed, the primary product is obtained by distillation, water washing and other process steps.

2. Disintegration reaction

The disintegration reaction refers to the final synthesis of DOTP by dehydration, condensation and other reaction steps of the primary product. The control of acid value and temperature in the reaction has a critical influence on the yield and quality of the product.

usually uses sulfuric acid, tetramethylsilicic acid, ferric chloride and other catalysts, adding carboxylic anhydride in the reaction, control the reaction temperature and time, promote the condensation reaction. The reaction is carried out at about 160 ° C. for 3-4 hours, and high-purity DOTP is finally obtained.

2. Preparation Methods

1. Catalyst Selection

In the production of DOTP, catalyst is one of the most important factors. The choice of catalyst should be considered comprehensively according to different reaction steps and reaction conditions.

For the esterification reaction, the acidic catalyst with low toxicity and high activity can be selected, such as ammonium sulfate, phosphoric acid, etc.; for the reaction, the acidic catalyst with good stability and catalytic effect should be selected, such as benzoic acid.

2. Control of reaction conditions

The control of reaction conditions has an important influence on the yield and quality of DOTP. In the reaction process, to control the reaction temperature, reaction time, the amount of catalyst, the proportion of raw materials and other factors, in order to obtain the best reaction effect.

For example, in the esterification reaction, the temperature should be controlled between 60-80°C, and the amount of catalyst added should be different according to the ester; in the reaction, the acid value should be controlled between 0.05-0.1mgKOH/g, which also needs to be adjusted according to specific conditions.