About Dichloromethane

Dichloromethane is a non-flammable low-boiling solvent. It is often used to replace flammable petroleum ether and ether. Molecular formula CH2Cl2, molecular weight 84.93. Colorless transparent liquid with a pungent odor similar to ether. Insoluble in water, soluble in ethanol and ether.
Pure dichloromethane has no flashpoint. The solvent mixture containing an equal volume of dichloromethane and gasoline, solvent naphtha, or toluene is not flammable. However, when dichloromethane is mixed with acetone or methanol liquid in a ratio of 10:1, The mixture has a flashpoint, vapor, and air form an explosive mixture with an explosion limit of 6.2% to 15.0%.

Uses of Dichloromethane：

Dichloromethane has the advantages of strong solubility and low toxicity. It is widely used in the manufacture of safety film and polycarbonate, and the rest is used as coating solvent, metal degreasing agent, aerosol spraying agent, polyurethane foaming agent, mold release agent, and release agent. Lacquer.
Dichloromethane is a colorless liquid. It is used as a reaction medium in the pharmaceutical industry to prepare ampicillin, ampicillin, and cephalosporin; it is also used as a solvent in film production, petroleum dewaxing solvent, aerosol propellant, Organic synthetic extractant, a foaming agent used in the production of foam plastics such as polyurethane, and metal cleaning agent.
Dichloromethane is mainly used in film production and medicine. Among them, the consumption for film production accounted for 50% of the total consumption, medicine accounted for 20% of the total consumption, the cleaning agent and the chemical industry accounted for 20% of the total consumption, and other aspects accounted for 10%. Dichloromethane is also used as a refrigerant in industrial refrigeration systems, but it is very harmful and can produce highly toxic phosgene when it comes in contact with open flames or hot objects. It can be hydrolyzed to generate a small amount of hydrogen chloride in humid air, and light can also promote hydrolysis and increase the corrosiveness of metals.
Used for grain fumigation and refrigeration of low-pressure refrigerators and air-conditioning devices. Used as an auxiliary blowing agent in the production of polyether urethane foam, and as a blowing agent for extruded polysulfone foam.
Dichloromethane is also used to make decaffeinated coffee. The coffee is first steamed to dissolve the caffeine and float on the surface, and then use methylene chloride to remove the caffeine.

Dichloromethane preparation method:

1. Natural gas chlorination method: natural gas reacts with chlorine. After water absorbs hydrogen chloride by-produced hydrochloric acid, the residual traces of hydrogen chloride are removed with lye, and then dried, compressed, condensed, and distilled to obtain finished products. Among them, chlorine is 100% 4000, natural gas (standard Under conditions), methane content is 97% 1000 m3/t, liquid caustic soda is 100% 274.
2. Chlorination of methyl chloride: 1) Photochlorination is the reaction of methyl chloride with chlorine under 4000kW of light, and the reaction product is alkali washed, compressed, condensed, dried, and rectified to obtain the finished product; 2) Thermal chlorination is to remove chlorine Methane and chlorine are mixed according to (2～2.5):1 (mass), and the reaction is carried out at a reaction temperature of 400°C and a reaction pressure of 0.2MPa. The reaction product is washed with water, alkali washed, compressed, condensed, dried, and rectified to obtain a finished product.

The industry generally synthesizes through the chlorination of methane. Chlorination of methane yields a mixture of four types of methyl chloride, but because the boiling points of each are separated by a relatively large distance, it can be easily separated and purified by ordinary fractionation techniques.