What Diethylene Glycol CAS 111-46-6 Is
Diethylene glycol, abbreviated DEG, is a clear, colourless, practically odourless and strongly hygroscopic liquid with the molecular formula C4H10O3, a molecular weight of 106.12 and the CAS registry number 111-46-6. It is also known as 2,2'-oxydiethanol or bis(2-hydroxyethyl) ether. DEG is produced alongside monoethylene glycol when ethylene oxide reacts with water, and it is separated by distillation as the second-largest component of that reaction. Its structure - two hydroxyl groups joined by an ether link - gives it a dual character: it behaves as a high-boiling polar solvent and at the same time as a reactive diol that can be built into polymers.
Physical and Chemical Properties
| Property | Typical value |
|---|---|
| CAS number | 111-46-6 |
| Molecular formula | C4H10O3 |
| Molecular weight | 106.12 g/mol |
| Appearance | colourless, practically odourless liquid |
| Boiling point | about 245 °C at 101.3 kPa |
| Melting point | about -10 °C |
| Density at 20 °C | about 1.118 g/cm3 |
| Solubility | miscible with water and with most organic solvents |
| Hygroscopicity | strong; absorbs moisture from air |
The hydroxyl value, water content, colour and glycol distribution are the parameters most often measured on receipt. Because DEG is miscible with water, it cannot be dried by simple decantation; water content is controlled at the production plant and protected by sealed storage. Commercial grades are sold against a specification rather than a single figure:
| Specification item | Typical commercial requirement |
|---|---|
| Assay (GC) | 99.5 % minimum |
| Water content | 0.05 % maximum |
| Colour | 15 Pt-Co (APHA) maximum |
| Specific gravity at 20/20 °C | 1.117-1.120 |
| Acidity as acetic acid | 0.005 % maximum |
| Ash | 0.01 % maximum |
Benefits of DEG in Industrial Formulations
Strong hygroscopicity. DEG takes up water aggressively, which makes it effective for dehydrating gas streams such as natural gas and for controlling moisture in closed industrial processes.
Good solvency power. It dissolves a wide range of resins, dyes and organic compounds and acts as a coupling agent that helps water-miscible and oil-miscible ingredients stay in one phase.
Low volatility. Its high boiling point of about 245 °C means it evaporates very slowly, so it stays in the formulation as a carrier or humectant instead of flashing off during mixing, coating or drying.
Versatile reactive diol. The two hydroxyl groups react with acids, isocyanates and other reagents, making DEG a building block for polyesters, polyurethanes, plasticisers and specialty chemicals such as morpholine.
Wide liquid range. It remains liquid from about -10 °C to 245 °C and mixes with water in all proportions, which is why it is used in fluid blends for low-temperature service.
Main Applications of Diethylene Glycol
DEG is a workhorse intermediate, and demand is spread across several industries rather than concentrated in one:
Natural gas dehydration. In glycol dehydration units DEG and its lighter relatives absorb water from wet gas, preventing hydrate formation and internal corrosion in pipelines; the rich glycol is regenerated by heating and returned to the contactor.
Unsaturated polyester resins. As a diol it introduces flexibility and toughness into the resin backbone, improving impact behaviour in gel coats, laminates and moulding compounds.
Polyurethanes and plasticisers. It extends polyol chains and forms esters used to soften and stabilise polymer systems.
Brake fluids and antifreeze blends. Its high boiling point and water tolerance help keep the boiling point of hydraulic fluid stable under repeated braking.
Coatings, inks and textile processing. DEG acts as a solvent, viscosity modifier and dye carrier, and helps control drying behaviour in printing inks.
Humectant and softening agent. It keeps adhesives, paper and cellophane flexible by holding a controlled amount of moisture.
Extraction and gas processing. It is used as an extraction solvent in oil refining and aromatics recovery duties.
Safety, Storage and Handling
DEG is toxic if swallowed and can cause serious kidney injury and damage to the central nervous system. It must never be transferred into food, beverage or drinking-water containers, and any container used for it should be permanently labelled for industrial use only so that misuse is impossible. Inhalation of mist or vapour and prolonged skin contact should be avoided, and handling areas should be ventilated; gloves and eye protection are recommended for routine operations. Bulk storage in mild steel or stainless steel tanks with sealed, clearly marked outlets protects both the quality of the product and the safety of the plant. Buyers should confirm that the grade offered meets the purity and regulatory requirements of the intended end use before accepting delivery, and the safety data sheet should be reviewed before first handling.
Frequently Asked Questions
Q: What is diethylene glycol used for?
It is used for natural gas dehydration, as a solvent and humectant, and as an intermediate for unsaturated polyesters, polyurethanes, plasticisers and other specialty chemicals.
Q: Is DEG the same as ethylene glycol?
No. Ethylene glycol has the formula C2H6O2, while DEG is its dimer with the formula C4H10O3 and a much higher boiling point of about 245 °C.
Q: What is the CAS number of diethylene glycol?
The CAS number is 111-46-6, and its molecular formula is C4H10O3.
Q: Is diethylene glycol safe to ingest?
No. DEG is toxic if swallowed and can cause severe kidney and nervous system damage, so it must never be stored in food or drink containers.
Q: Why is DEG used in natural gas processing?
Its strong affinity for water lets it absorb moisture from the gas stream, which prevents hydrate formation and corrosion in pipelines.
Q: Is DEG a solvent or a chemical raw material?
Both. It works as a high-boiling polar solvent in coatings, inks and extraction duties, and its two hydroxyl groups make it a reactive raw material for polyester and polyurethane production.