Background and overview[1-2]
Ethylene glycol dimethyl ether is also known as 1,2-dimethoxyethane, dimethyl cellosolve, α,β-dimethoxyethane, Glyme, or GDME for short. Colorless liquid. Smells of ether. Relative molecular mass 90.12. Relative density 0.8628. Melting point -58℃ (there are also reports of 69℃ and 71℃). Boiling point: 83~84℃, 20℃ (8.159×103Pa), 16℃ (6.666×103Pa), -14℃ (1.333×103Pa). Flash point 4.5℃. Refractive index 1.3796. Viscosity 1.10mPa·s (20℃). Soluble in hydrocarbon solvents and water, miscible with ethanol, ether and acetone. Stable in nature and not prone to chemical reactions. Has strong dissolving ability. Low toxicity. Ethylene glycol dimethyl ether is an aprotic polar solvent with superior performance and is widely used in the chemical industry as well as in the synthesis of pharmaceutical extractants and organic intermediates. Ethylene glycol dimethyl ether produced by the traditional Williamson synthesis method is prepared under the action of sodium ethoxide phase transfer catalyst. This process has a long reaction path and many by-products, making it difficult to separate products. In order to obtain pure products, it is necessary to neutralize the waste alkali liquid with acid. The whole process will produce a large amount of industrial salt and wastewater, causing serious environmental pollution, and the use of liquid acid and alkali will cause serious damage to the equipment. The corrosion resistance requirements are high. With the need for product upgrading and the improvement of people’s awareness of environmental protection, the use of environmentally friendly solid acid catalyst technology has become an urgent need.
Purpose[3-4]
Ethylene glycol dimethyl ether is used as a reactive solvent, such as a reactive solvent for alkali metal hydrides and boron derivatives, a reducing solvent for lithium borohydride, and a solvent for the Wurtz hydrocarbon synthesis method. Solvents for reagents; solvents for cellulose and derivatives, coatings and inks, such as varnishes and Chinese paints, thinner whitening inhibitors, fiber and leather leveling agents, picture printing leveling agents; used as separation extraction agents, from Extraction of fatty acids from aqueous solutions, refining of alkyl phosphoric acids, separation and leaching of uranium ores, and refining of pharmaceuticals. For example, preparing glutaric acid monomethyl ester sodium salt and glutaric acid monomethyl ester includes: (1) dissolving sodium methoxide and glutaric anhydride in anhydrous ethylene glycol dimethyl ether respectively; (2) dissolving glutaric anhydride The anhydrous glycol dimethyl ether solution is added dropwise to the sodium methoxide anhydrous glycol dimethyl ether solution to react; the reaction product is concentrated, filtered, and dried to obtain glutaric acid monomethyl ester sodium salt; (3) Glutaric acid Mix the monomethyl ester sodium salt with an organic solvent to obtain a suspension. Adjust the pH value of the suspension to strong acidity; let it stand for layering, extract the water layer, combine the organic layers, dry, and remove the organic solvent to obtain pentadienyl alcohol. acid monomethyl ester. The present invention uses ethylene glycol dimethyl ether as the reaction solvent, the entire reaction is carried out in a homogeneous phase, and has the advantages of stable reaction, high product purity, mild reaction conditions, and no production of dimethyl glutarate; in addition, the method of the present invention also Glutaric acid monomethyl ester sodium salt can be prepared simultaneously, with high synthesis yield and product purity.
Preparation[1]
The specific steps for the preparation method of ethylene glycol dimethyl ether are as follows:
(1) Add a certain amount of ethylene glycol monomethyl ether to the reaction kettle, then put a certain amount of caustic soda into the ethylene glycol monomethyl ether for the first time, stir it, and then cool the temperature of the reaction solution to 15°C ~ 20°C, then add a certain amount of caustic soda into ethylene glycol monomethyl ether for the second time, stir thoroughly and then cool down the reaction system. Control the temperature of the reaction solution at 25°C ~ 30°C. Ethylene glycol monomethyl ether reacts with sodium hydroxide to generate ethylene glycol monomethyl ether sodium salt; the molar ratio of ethylene glycol monomethyl ether and sodium hydroxide is 1:0.5, and the first step is to ethylene glycol monomethyl ether. The amount of caustic soda put into the monomethyl ether is the same as the amount of caustic soda put into the ethylene glycol monomethyl ether for the second time.
(2) Pour methyl chloride gas into the ethylene glycol monomethyl ether sodium salt solution generated in step (1), maintain the pressure in the reaction kettle at 0.05MPa~0.5MPa, and control the temperature of the reaction system At 70℃~75℃, continuously feed methyl chloride gas for 8 hours. With the introduction of methyl chloride gas, white sodium chloride crystals will slowly precipitate until the reaction is completed, and the reaction liquid will be colorless or extremely white. Light yellow, will not turn reddish brown.
(3) Filter the reaction solution obtained in the above step (2). The filter cake is clean sodium chloride, and the filtrate is a solution of sodium chloride in ethylene glycol dimethyl ether. The filtrate is distilled, and the effluent is ethanol. Glyme product, the residual solid is crude sodium chloride.
Main reference materials
[1] Practical Fine Chemical Dictionary
[2] One-step synthesis of ethylene glycol dimethyl ether using ZrO2/TiO2 catalyst
[3] Practical Fine Chemical Dictionary
[4] CN201110120577.2 Glutarate monomethyl ester sodium salt and synthesis method of glutarate monomethyl ester
[5] CN201510246776.6 A preparation method of ethylene glycol dimethyl ether
