Dichloromethane

Introduction:

Methylene chloride is also known as dichloromethane, and represented as CH2Cl2. It has a slightly sweet odour, and is widely used as a solvent in many industries. It is immiscible in water, but is miscible with many other polar solvents. It occurs naturally in volcanoes, wetlands and oceanic resources. But mostly, it is manufactured or processed through industrial emissions. In the 1990’s it was estimated that around 400,000MT of dichloromethane were processed around the world. 

Manufacturing process:

Dichloromethane is prepared by making chlorine gas to react with methane at 400–500 °C. The reactants undergo a series of reactions to produce dichloromethane. 

CH4 + Cl2 → CH3Cl + HCl

CH3Cl + Cl2 → CH2Cl2 + HCl

CH2Cl2 + Cl2 → CHCl3 + HCl

CHCl3 + Cl2 → CCl4 + HCl

Through this reaction, chloromethane, dichloromethane, chloroform and carbon tetrachloride is obtained. The products are distilled for separation.

1. Used as solvents in chemical industry, for various chemical processes.

2. Used to decaffeinate coffee and tea, so as to get flavorings in the food industry.

3. Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams.

4. DCM is used in sealing the casing of electric meters, and often sold as plastic welsing adhesives.

5. It is used in the garment printing industry for removal of heat-sealed garment transfers.