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[Chemical Knowledge]：Production process and preparation method of diethylene glycol (DEG)

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Diethylene glycol (DEG) is an important organic chemical raw material with many applications, such as solvents, surfactants, plastics, rubbers, fibers, coatings and resins. The production process and preparation method of DEG will be described below.

1. production process

1.1 distillation method

distillation method is the main method of producing DEG. The method is to mix propylene glycol and water, heat under vacuum, and at the same time use cooling water to cool the steam, the diethylene glycol is gasified and cooled into a liquid by a condenser, and then a certain amount of water is removed by the reaction kettle, and finally the diethylene glycol product is obtained.

1.2 solvent method

solvent method is a more advanced method for TEG to directly produce DEG than distillation method. It mainly uses the different separability of TEG and DEG. TEG and DEG are separated from the solution by controlling the water in the solvent and the phase equilibrium conditions of the binary array, and then the diethylene glycol is separated by stepwise distillation to obtain high-purity diethylene glycol products. The technology has the advantages of stable and controllable process, simple equipment and energy saving effect of chemical synthesis reaction.

2. preparation method

2.1 hydrogenation method

In the process of producing DEG by distillation, the yield of DEG can be improved by hydrogenation reaction. The specific method is that ethylene glycol and a small amount of alkali metal salt are used as catalysts, and the hydrogenation reaction is carried out under the condition of high pressure and high temperature under the action of hydrogen, so that ethylene glycol can be converted into DEG. Among them, the catalyst requires high purity, not easy to deactivate, compact reaction assembly, in order to make full use of hydrogen and other advantages.

2.2 chlorination

chlorination is another method for producing DEG. The method is to mix ethylene glycol and ferric hydroxide (Fe(OH)2), add a small amount of alcohol to accelerate the reaction, and then react the mixture with ferric chloride and hydrogen chloride to obtain DEG through acid-base hydrolysis reaction. The reaction has the characteristics of simple operation and low cost.

2.3 dehydration method

dehydration method refers to ethylene glycol under the action of proton acid or alkali catalyst, dehydration reaction to obtain DEG. It mainly has the advantages of wide selection of catalysts, easy operation and continuous production.

To sum up, mastering the production process and preparation method of DEG is helpful to improve the quality and output of DEG products. At the same time, with the increasing development of science and technology, it is expected that the future research and development of DEG will have a broader application prospects.