Methylene chloride(CAS 75-09-2 DCM) has broad-spectrum solvency, low boiling point, relatively low toxicity and relatively best reaction inertness, making it the most frequently used organic solvent in organic synthesis. As a solvent, its status is almost equivalent to that of water in inorganic salt chemistry. The main production route for dichloromethane is the chlorination of methane or methyl chloride. Its production method firstly adopted methane or methyl chloride high-temperature gas-phase thermal chlorination method, and later developed photochemical chlorination method. In 1972, C-EL ummus company of the United States and Arm-strong company jointly developed the methane oxychlorination method. In 1979, the Japanese Tokuyama Soda Chemical Company developed the low temperature liquid phase free radical induced chlorination method of methyl chloride to produce methyl chloride. Technology. Currently widely used in industrial production is thermal chlorination. In recent years, the application field of dichloromethane has been continuously expanded, and the production quality of the solvent is also required to be improved accordingly.
Improved method for purification of methylene chloride
In experiments such as instrumental analysis and organic synthesis, dichloromethane is a commonly used solvent, and the purity of commercially available methylene chloride cannot meet the required requirements, and generally needs to be purified. The existing purification method is treated with concentrated sulfuric acid, then washed with water, washed with a 5% sodium carbonate aqueous solution and then washed with water, and finally dried with calcium chloride and then distilled. The purification method is complicated and the purification effect is not ideal.
In view of the deficiencies of the existing technology, the purification method is upgraded. The methylene chloride is passed through three adsorbents including modified magnesium silicate, modified activated carbon and modified molecular sieve. methylene chloride first passes through the magnesium silicate adsorbent, and then passes through the layered modified activated carbon and modified molecular sieve. The modified activated carbon and the modified molecular sieve are at least one layer respectively, wherein the modified magnesium silicate is the modified silicon which is impregnated with an inorganic acid solution, then impregnated with an organic acid solution, washed to neutrality and then dried and calcined.
Magnesium silicate, modified activated carbon is activated carbon modified by nitric acid, and modified molecular sieve is Y-type molecular sieve exchanged with copper ions; during the treatment of modified magnesium silicate, the inorganic acid is selected from hydrochloric acid, nitric acid, sulfuric acid or phosphoric acid, and the Concentration is 0.05～0.2mol/L, immersion temperature is 20～70 ℃, and immersion time is 30～90min; Organic acid is selected from Cl～C The organic carboxylic acid of organic acid, the concentration of organic acid solution is 0.05～0.5mol/ L, immersion temperature is 20～70 ℃, and immersion time is 15～60min; Modified activated carbon treatment method is: put activated carbon into the nitric acid solution that mass concentration is 5%～30% and soak 12～24h, then filter , clean to neutrality, dry to constant weight at 100～200 ℃;
Modified molecular sieve processing method is: Y molecular sieve is soaked in cupric chloride solution, carry out ion exchange, then filter, wash, finally carry out heating roasting , wherein the copper dichloride solution concentration is 0.05～1.0mol/L, and the ion exchange temperature is 20～80 ℃, and the ion exchange time is 1～10h, and Q/Y=10:1～40:1, and Q is dichloride Copper solution, in ml, Y is Y molecular sieve, in g
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