Description

Ethylene glycol is an organic compound with the formula C₂H₆O₂. It is a clear, colorless, syrupy liquid with a sweet taste — but highly toxic if ingested.

Key facts

Common uses

Primary ingredient in antifreeze and engine coolants

Used as a precursor in manufacturing polyester fibers and PET plastics

Acts as a dehydrating agent in various industrial processes

Physical properties

Boiling point: ~197 °C

Melting point: −12.9 °C

Miscible with water

Viscous and hygroscopic (absorbs water)

Toxicity

Ingestion can cause severe metabolic acidosis, kidney failure, and can be fatal

Metabolized to glycolic acid and oxalic acid, which cause organ damage

Requires prompt medical treatment (e.g., fomepizole)

Why it’s in antifreeze

Lowers the freezing point and raises the boiling point of water

Helps prevent engine coolant from freezing in winter and overheating in summer..

Industrial Routes to Ethylene Glycol (High-Level Overview)
1. Oxidation of Ethylene → Ethylene Oxide → Ethylene Glycol

This is the main commercial process today.

Ethylene is partially oxidized with oxygen using a silver-based catalyst to form ethylene oxide (EO).

Ethylene oxide is then hydrated with water to produce ethylene glycol along with some higher glycols.

This method is efficient and used worldwide in large-scale chemical plants.

2. Hydrolysis of Ethylene Oxide Under Acidic or Neutral Conditions

Ethylene oxide reacts with excess water to produce ethylene glycol.

More water shifts the reaction toward glycol rather than di- or tri-ethylene glycol.

Carried out in controlled industrial reactors.

3. Alternative Routes (Less Common)

Carbonylation of formaldehyde followed by hydrogenation

Direct synthesis from syngas (CO + H₂) via intermediate steps

Biobased approaches, such as fermenting biomass-derived sugars, then catalytic conversion to glycol

These are used where sustainable or non-petroleum pathways are desired.

Notes on Safety and Practicality

Ethylene glycol synthesis involves hazardous intermediates, especially ethylene oxide, which is flammable, carcinogenic, and explosive. As such, synthesis is performed only in industrial facilities with specialized equipment.