Monoethylene Glycol is an organic compound with the formula CH₂OHCH₂OH. It is a colorless, odorless, sweet-tasting, syrupy liquid. It is miscible with various organic solvents such as water, alcohol, ether, and chloroform. Approximately 1.5 million tons are produced annually.
Monoethylene glycol is used in many areas in both industry and daily life. It can be polymerized or esterified to obtain various ethylene glycol derivatives. These derivatives are used in sectors such as glass, ceramics, soap, fertilizer, paint, textile, cosmetics, pharmaceuticals, adhesives, sealants, water treatment, and others.
Chemical and physical properties of monoethylene glycol are as follows:
- Molecular weight: 62.07 g/mol
- Melting point: -12.9 °C
- Boiling point: 197 °C
- Density: 1.11 g/mL
- Solubility: High in water and alcohol, moderate in ether, low in chloroform
- pKa value: 14.5
Production methods of monoethylene glycol are as follows:
- Ethylene oxide hydrolysis method: This is the most common production method for monoethylene glycol. Ethylene oxide (EO) is hydrolyzed with water under pressure to produce monoethylene glycol. This reaction can be accelerated using acid or base catalysts. In this method, by-products such as diethylene glycol and triethylene glycol are also formed.
- Oxidative carbonylation method: This is an alternative production method for monoethylene glycol. Ethylene reacts with carbon monoxide and oxygen to produce monoethylene glycol. This reaction is carried out using metal catalysts such as palladium or rhodium. Water is also formed in this method
Applications of monoethylene glycol include:
- As antifreeze: Monoethylene glycol is the main component in antifreeze formulations. It is used as a heat transfer agent in automobiles, computers, and cooling systems. When mixed with water, it lowers the freezing point and raises the boiling point. It also helps prevent corrosion.
- For polyester fiber production: Monoethylene glycol is an important raw material in polyester fiber production. It is esterified with terephthalic acid or dimethyl terephthalate to obtain polyethylene terephthalate (PET). PET is then melted or crystallized to form polyester fiber.
- For the plastic industry: Monoethylene glycol is also used in the plastic industry. Polyethylene terephthalate (PET) is used in the production of plastic bottles. Monoethylene glycol is also used in the production of polyurethane foams.
- For natural gas facilities: Monoethylene glycol is also used in natural gas plants. It is used to dehydrate and clean natural gas. It is also used to prevent icing in natural gas pipelines.
- For the tanning and pharmaceutical industries: Monoethylene glycol is also used in the tanning and pharmaceutical industries. It is used to soften and preserve leather in tanning. In the pharmaceutical industry, it is used for tablet coating and improving solubility.