Ethylene Oxide CAS 75-21-8

What is Ethylene Oxide?

Ethylene oxide is the simplest epoxide, C₂H₄O, a strained three-membered ring that makes it exceptionally reactive. It is a colourless gas at ambient, liquefying at about 10.4 °C, with a faint sweet odour.

That ring strain is both the commercial value and the hazard. It opens readily with water, alcohols and amines to give glycols, ethoxylates and ethanolamines, and it can also polymerise exothermically and decompose explosively without any air present.

Around three quarters of production goes to ethylene glycols, principally MEG for polyester. Ethoxylated surfactants, ethanolamines, glycol ethers and medical device sterilisation take the remainder.

Ethylene oxide is a Category 1B carcinogen and mutagen, flammable over an extremely wide range, and capable of deflagrating as a pure vapour. It is among the most hazardous products in routine industrial trade.

Why Ethylene Oxide specifically

• Extreme ring strain. The three-membered ring opens under mild conditions, giving clean reactions with a wide range of nucleophiles.
• The glycol route. Hydrolysis gives MEG, DEG and TEG, the backbone of polyester and antifreeze.
• Ethoxylation chemistry. Adds oxyethylene units to alcohols and amines to build surfactants with tunable solubility.
• Low-temperature sterilisation. Penetrates packaging and kills microorganisms without heat, which keeps it essential for medical devices.

How Ethylene Oxide is Manufactured

Ethylene oxide is made by direct catalytic oxidation of ethylene over silver, a process that has changed little in principle for decades.

• Ethylene and oxygen feed. Polymer-grade ethylene and high-purity oxygen are fed with a recycle stream and moderator.
• Silver catalyst oxidation. Partial oxidation over a supported silver catalyst at about 200 to 300 °C and 15 to 25 bar.
• Moderator control. Trace organic chlorides are dosed to suppress total combustion and maintain selectivity.
• Absorption. EO is absorbed from the reactor gas in water as a dilute solution.
• Stripping and purification. EO is stripped from the water, then distilled to remove aldehydes, water and carbon dioxide.
• Glycol integration. Most plants hydrolyse part of the EO directly to glycols on site rather than isolating all of it.

Typical Commercial Specification

Figures below are representative of commercial high-purity ethylene oxide. Tell us your downstream reaction and we will advise on the aldehyde and water limits you should specify.

Physical & Chemical Properties

Behaviour in the process

Ethylene oxide's reactivity is the reason for every rule that governs it:

• Flammable without air. The upper flammable limit is 100%: pure EO vapour can propagate a decomposition flame with no oxygen present.
• Exothermic polymerisation. Acids, bases, rust and metal oxides catalyse runaway polymerisation that can rupture equipment.
• Boils at 10.4 °C. Refrigerated or pressurised storage under nitrogen is mandatory.
• Reacts with almost everything nucleophilic. Water, alcohols, amines and acids all open the ring, so system cleanliness and dryness matter.

Ethylene Oxide and Related Products

Ethylene oxide is bought only by sites equipped to handle it. For most buyers, the derivative is the better purchase.

Stated plainly: unless you operate an ethoxylation or glycol unit, buy the derivative rather than the oxide. Ethylene oxide is one of the few products where the handling requirement, not the price, decides whether a purchase makes sense.

Industries We Supply Ethylene Oxide To

Ethylene oxide users are a small, highly qualified group, and the specification varies little between them.

Where Ethylene Oxide is Used

Ethylene glycols take the largest share, with surfactant ethoxylates and ethanolamines behind them.

In ethoxylation

Ethylene oxide is added to an alcohol, acid or amine under base catalysis to build a polyoxyethylene chain, with the number of units controlling hydrophilic balance. The reaction is strongly exothermic and the reactor must be designed to remove heat faster than it is generated, which is why ethoxylation plants are purpose-built rather than general-purpose.

In sterilisation

Ethylene oxide penetrates sealed packaging and alkylates microbial DNA, sterilising without heat. It remains irreplaceable for heat-sensitive medical devices, but residual EO limits, worker exposure control and emission abatement all apply, and regulatory pressure on emissions has grown significantly.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with acidity and iron reported alongside purity because both affect stability as well as quality.

• Ethylene oxide purity — by gas chromatography, the primary grade measure.
• Water and carbon dioxide — reported because both react and affect downstream chemistry.
• Acidity — measured because acid catalyses runaway polymerisation.
• Aldehydes — reported because they carry colour and odour into ethoxylates.
• Iron and chlorides — tested because both catalyse decomposition and corrode equipment.
• Non-volatile residue — confirming freedom from polymer and contamination.

Common Process Problems & Likely Causes

When ethylene oxide causes trouble, it is almost always contamination or temperature. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. Cylinders and dedicated ISO tank containers under nitrogen pad; pipeline supply where available.
• Nitrogen padding. Mandatory. The vapour space must be kept out of the flammable region and free of air.
• Temperature control. Refrigerated or pressurised storage with temperature monitoring and alarms; EO boils at 10.4 °C.
• System cleanliness. Vessels must be clean, dry and free of rust, acid, alkali and amine residues, all of which catalyse polymerisation.
• Material compatibility. Carbon steel and stainless steel, scrupulously clean. Avoid copper, magnesium, silver and mercury alloys, which can form acetylides.
• Segregation. Keep strictly apart from acids, bases, amines, alcohols and oxidisers.
• Detection and abatement. Continuous gas detection and scrubber or catalytic abatement on vents are standard.
• Transport classification. UN 1040, ethylene oxide with nitrogen, Class 2.3 toxic gas with subsidiary 2.1 flammable.

Hazards & Safe Handling

Ethylene oxide is a flammable, acutely toxic, carcinogenic and mutagenic gas that can decompose explosively without air. It is among the most hazardous products in routine industrial use and demands engineered controls throughout.

• Carcinogenicity and mutagenicity. Classified Category 1B for both. Exposure must be reduced as low as technically achievable, with closed systems, monitoring and medical surveillance.
• Occupational exposure. Limits are very low, commonly around 1 ppm or below as an 8-hour average with action levels beneath that. Confirm the limit in your jurisdiction.
• Flammability without air. The upper flammable limit is 100%: pure vapour can deflagrate. Nitrogen padding and ignition control are both mandatory.
• Runaway polymerisation. Acids, bases, rust and metal oxides catalyse exothermic polymerisation capable of rupturing vessels.
• Acute toxicity. Toxic by inhalation, causing respiratory tract damage and central nervous system effects.
• Skin and eye damage. Causes burns; the liquid also freezes tissue on contact as it evaporates.
• Emergency planning. Gas detection, emergency isolation, water deluge and evacuation procedures are expected on every EO site.
• Environment. Harmful to aquatic life; vent only through approved abatement systems.

Regulatory & Compliance Notes

Ethylene oxide is among the most heavily regulated industrial chemicals, as a carcinogen, a toxic gas and an emission source. The notes below are orientation rather than legal advice.

• GHS classification. Flammable gas Category 1, gas under pressure, acute toxicity Category 3, carcinogenicity Category 1B, germ cell mutagenicity Category 1B and skin corrosion.
• Occupational exposure regulation. Specific ethylene oxide standards with very low exposure limits, monitoring, regulated areas and medical surveillance apply in most jurisdictions.
• Emissions regulation. Sterilisation facility EO emissions are subject to increasingly strict abatement requirements, particularly in the US and EU.
• Dangerous goods transport. UN 1040, Class 2.3 with subsidiary 2.1. ADR, IMDG, IATA and DOT rules apply to cylinder and tank design, labelling and routing.
• Medical device residues. Residual EO and ethylene chlorohydrin limits on sterilised devices are set by ISO 10993-7.
• REACH and inventories. Registered under EU REACH with harmonised classification as a carcinogen and mutagen.

We Supply Ethylene Oxide Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Ethylene Oxide from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
• Flexible volumes. From a single cylinder up to repeat bulk shipments on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying Ethylene Oxide from Chelora

We are an independent sourcing and supply partner. For ethylene oxide that means settling three things before anything is nominated: your demonstrated handling capability and site controls, the purity and aldehyde limits your reaction needs, and the supply format — cylinder, ISO tank or pipeline — that your system can receive safely.

• Documentation on every lot. Batch-specific COA (purity, water, acidity, aldehydes), plus SDS and the full transport paperwork.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
• Quantities. From a single cylinder through to full bulk shipments on contract supply.
• Grade matching. High-purity ethylene oxide to the water, acidity, aldehyde and iron limits your ethoxylation or hydrolysis unit requires.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related products. Mono Ethylene Glycol, Diethylene Glycol, Propylene Oxide and other feedstocks alongside Ethylene Oxide from one supplier.

How ordering works

• Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing format and a sample COA, normally within one working day.
• Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
• Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.

Related Products

Buyers of ethylene oxide generally source its derivatives alongside it, or instead of it — glycols, ethanolamines and glycol ethers are commonly bought on the same programme.