Propylene Oxide CAS 75-56-9
Chelora Chemicals supplies high-purity propylene oxide to polyether polyol, propylene glycol and glycol ether producers worldwide. Because PO is a highly flammable, volatile epoxide that polymerises exothermically, every consignment leaves with a batch-specific COA, the current SDS and full dangerous-goods documentation.
Also known as: PO · 1,2-Epoxypropane · Methyloxirane · Propene oxide · Propylene epoxide
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Price, lead time and a sample COA for Propylene Oxide, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (purity, water, acidity, aldehydes)
- Safety Data Sheet (SDS)
- Transport and dangerous-goods documents
- Third-party inspection on request
- Certificate of origin
What is Propylene Oxide?
Propylene oxide is the methyl-substituted epoxide, C₃H₆O, a colourless, extremely volatile liquid boiling at 34 °C with an ether-like odour. Unlike ethylene oxide it is a liquid at ambient, which makes handling simpler but no less demanding.
The strained epoxide ring opens readily with alcohols, water and amines. Ring opening with a starter alcohol under base catalysis builds the polyether polyols that make polyurethane foams; hydrolysis gives propylene glycol.
Polyether polyols take about two thirds of global production, propylene glycol most of the rest, with glycol ethers and specialty derivatives behind them.
PO is a Category 1B carcinogen, extremely flammable with a flash point near −37 °C, and capable of runaway polymerisation if contaminated with acid, alkali or rust.
Why Propylene Oxide specifically
- A reactive but controllable epoxide. Less violent than ethylene oxide, yet still opens cleanly under mild base catalysis.
- The polyol route. Sequential addition to a polyol starter gives the flexible and rigid foam polyols that underpin polyurethanes.
- A chiral centre. The methyl group creates stereochemistry that matters in specialty and pharmaceutical derivatives.
- Liquid at ambient. Easier to ship and meter than ethylene oxide, though its volatility still demands closed handling.
How Propylene Oxide is Manufactured
Propylene oxide is made by several competing routes, and the route determines the co-product and the plant economics.
- Chlorohydrin process. Propylene reacts with chlorine and water to propylene chlorohydrin, which is dehydrochlorinated with lime; the oldest route, with heavy chloride effluent.
- Styrene co-production (PO/SM). Ethylbenzene hydroperoxide epoxidises propylene, with styrene as the co-product.
- TBA co-production (PO/TBA). Isobutane hydroperoxide epoxidises propylene, giving tert-butyl alcohol as co-product.
- Cumene hydroperoxide process. A recycle route that produces PO with no net co-product.
- HPPO process. Direct epoxidation with hydrogen peroxide over titanium silicalite, producing only PO and water.
- Purification. Distillation removes water, aldehydes, methyl formate and residual chlorides before the product is nitrogen padded.
Typical Commercial Specification
Figures below are representative of commercial high-purity propylene oxide. Tell us your catalyst and starter system and we will advise on the limits you should specify.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless liquid, free of suspended matter |
| Propylene oxide purity | 99.9% min by weight |
| Water | 0.05% max |
| Acidity (as acetic acid) | To grade, typically 20 ppm max |
| Aldehydes (as acetaldehyde) | To grade, typically 50 ppm max |
| Total chlorides | To grade, typically 10 ppm max |
| Methyl formate | To grade, typically 50 ppm max |
| Non-volatile residue | To grade, typically 10 ppm max |
| Iron | To grade, typically 0.5 ppm max |
| Colour (Pt-Co) | 10 max |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₃H₆O (methyloxirane) |
| Molecular weight | 58.08 g/mol |
| Appearance | Clear colourless volatile liquid, ether-like odour |
| Boiling point | 34.2 °C |
| Melting point | −112 °C |
| Flash point | About −37 °C (closed cup) |
| Density | 0.830 g/cm³ at 20 °C |
| Vapour pressure | About 59 kPa at 20 °C |
| Vapour density (relative to air) | 2.0, heavier than air |
| Flammable limits in air | About 2.3 to 36% by volume |
| Autoignition temperature | About 449 °C |
| Solubility in water | About 40% at 20 °C |
| Incompatibilities | Acids, bases, amines, rust, metal chlorides, oxidisers, anhydrous metal halides |
Behaviour in the process
PO's reactivity and volatility together define how it is stored and transferred:
- Exothermic polymerisation. Acids, alkalis, rust and metal halides catalyse runaway polymerisation capable of rupturing vessels.
- Very wide flammable range. 2.3 to 36% in air, with a flash point far below ambient; vapour spaces are flammable unless padded.
- High volatility. Boiling at 34 °C, it flashes readily during transfer and pools as heavy vapour.
- Reacts with water. Slow hydrolysis to propylene glycol; water also acts as a starter in polyol synthesis.
Propylene Oxide and Related Products
PO is bought by sites equipped to handle a volatile, carcinogenic epoxide. For others, the derivative is the right purchase.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| High-purity propylene oxide | 99.9%+, nitrogen padded | Polyether polyol, propylene glycol and glycol ether manufacture |
| Mono propylene glycol | The hydrolysis product, CAS 57-55-6 | Where the glycol is wanted without epoxide handling |
| Ethylene oxide | C₂ epoxide, CAS 75-21-8 | Ethoxylation chemistry; a gas, considerably more hazardous |
| Polyether polyols | Finished polyols | Where polyol production can be bought rather than performed |
Stated plainly: unless you run a polyol or glycol unit, buy the derivative. PO handling demands nitrogen padding, closed transfer and carcinogen controls that only make sense at production scale.
Industries We Supply Propylene Oxide To
PO users are a concentrated group in polyurethanes, glycols and specialty chemistry.
Where Propylene Oxide is Used
Polyether polyols dominate PO demand, with propylene glycol and glycol ethers taking most of the rest.
In polyether polyol manufacture
PO is added stepwise to a glycerine, sucrose or glycol starter under potassium hydroxide or double metal cyanide catalysis. Chain length and functionality set whether the polyol makes flexible or rigid foam. Water in the PO feed acts as an extra starter, broadening the molecular weight distribution and shifting foam properties, which is why the water specification is tight.
In propylene glycol manufacture
PO is hydrolysed with excess water, thermally or catalytically, giving mono, di and tripropylene glycol in proportions set by the water ratio. The process mirrors ethylene glycol manufacture, and the purified MPG goes on to food, pharmaceutical and industrial grades.
Need a specific grade, purity and packing format?
Tell us the grade, your handling capability and the water and chloride limits your catalyst needs, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with water, acidity and chloride reported alongside purity because all three affect both safety and polyol quality.
- Propylene oxide purity — by gas chromatography, the primary grade measure.
- Water content — by Karl Fischer, critical because water acts as an unintended starter.
- Acidity — measured because acid catalyses runaway polymerisation.
- Aldehydes and methyl formate — reported as the characteristic process impurities affecting polyol odour.
- Total chlorides — tested because chloride-route material corrodes and poisons catalysts.
- Iron and non-volatile residue — confirming freedom from contamination that could seed polymerisation.
Common Process Problems & Likely Causes
When PO causes trouble, it is usually water, chlorides, acidity or temperature. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Polyol molecular weight distribution broad | Water in the PO acting as an extra starter | Water figure on the COA and drier performance |
| Pressure or temperature rising in storage | Polymerisation starting, catalysed by acid, rust or alkali | Emergency procedure first; then acidity, iron and system cleanliness |
| Polyol odour or colour poor | Aldehydes or methyl formate in the feed | Aldehyde and methyl formate figures |
| Catalyst consumption up in polyol synthesis | Acidity or chlorides neutralising the base catalyst | Acidity and chloride results |
| Corrosion in storage or transfer lines | Chlorides from chlorohydrin-route material | Chloride figure and production route of the lot |
| Losses during transfer | Flash vaporisation of a 34 °C boiling liquid | Transfer temperature, line cooling and vapour return |
Packaging, Storage & Shipping
- Standard packing. 200 L drums, ISO tank containers and road tankers, all nitrogen padded.
- Nitrogen padding. Mandatory. The vapour space must be kept out of the flammable range and free of air.
- Temperature control. Cool storage with temperature monitoring and alarms; PO boils at 34 °C.
- System cleanliness. Vessels must be clean, dry and free of rust, acid, alkali and amine residues, all of which catalyse polymerisation.
- Material compatibility. Clean carbon steel and stainless steel. Avoid copper, brass and anhydrous metal halides.
- Segregation. Keep strictly apart from acids, bases, amines and oxidisers.
- Shelf life. Typically 12 months in sealed, padded storage. Acidity and water are the practical checks.
- Transport classification. UN 1280, propylene oxide, Class 3 flammable liquid, packing group I.
Hazards & Safe Handling
Propylene oxide is extremely flammable, acutely toxic, carcinogenic and capable of runaway polymerisation. It demands engineered controls and closed handling throughout.
- Carcinogenicity and mutagenicity. Classified Category 1B for both. Exposure must be kept as low as technically achievable with closed systems and monitoring.
- Extreme flammability. Flash point about −37 °C with a flammable range of 2.3 to 36%. Nitrogen padding and ignition control are both mandatory.
- Runaway polymerisation. Acids, alkalis, rust and metal halides catalyse exothermic polymerisation capable of rupturing vessels.
- Acute toxicity. Harmful by inhalation, ingestion and skin contact, with respiratory and central nervous system effects.
- Skin and eye damage. Causes burns; rapid evaporation also freezes tissue on contact.
- Occupational exposure. Limits are low, commonly around 2 ppm or less as an 8-hour average; confirm the limit in your jurisdiction.
- PPE and detection. Closed transfer, gas detection, flame-resistant clothing and supplied-air protection for any breach of containment.
- Environment. Harmful to aquatic life; vent only through approved abatement.
Regulatory & Compliance Notes
Propylene oxide is regulated as a carcinogen and an extremely flammable liquid. The notes below are orientation rather than legal advice.
- GHS classification. Flammable liquid Category 1, carcinogenicity Category 1B, germ cell mutagenicity Category 1B, acute toxicity Category 3 and skin irritation.
- Occupational exposure regulation. Specific exposure limits, monitoring and in some jurisdictions medical surveillance apply.
- Dangerous goods transport. UN 1280, Class 3, PG I. ADR, IMDG, IATA and DOT rules apply to tank design, labelling and routing.
- REACH and inventories. Registered under EU REACH with harmonised classification as a carcinogen and mutagen.
- Quality agreements. Polyol producers commonly expect documented water, acidity and chloride limits with change control.
We Supply Propylene Oxide Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Propylene 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 pallet of drums 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 Propylene Oxide from Chelora
We are an independent sourcing and supply partner. For propylene oxide that means settling three things before nomination: your handling capability and padding arrangements, the water and chloride limits your catalyst needs, and the production route, because chlorohydrin material carries higher chlorides.
- 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 pallet of drums through to full bulk shipments on contract supply.
- Grade matching. High-purity PO to the water, acidity, aldehyde and chloride limits your polyol or glycol unit requires.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. Mono Propylene Glycol, Ethylene Oxide, Propylene and other feedstocks alongside Propylene 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.
Propylene Oxide — Common Questions
The questions our technical desk is asked most often about Propylene Oxide. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of propylene oxide?
The CAS number for propylene oxide is 75-56-9, and its EC number is 200-879-2. Its molecular formula is C₃H₆O with a molecular weight of 58.08 g/mol, and it is classified under HS code 2910.20.
What is propylene oxide used for?
About two thirds goes to polyether polyols for polyurethane foam. Most of the rest goes to propylene glycol, with glycol ethers, propoxylated surfactants and specialty chemicals taking the remainder.
Do you supply propylene oxide worldwide?
Yes, to receivers who can demonstrate the handling capability it requires. Every consignment carries the COA, the SDS and the full dangerous-goods documentation.
How is propylene oxide manufactured?
By several competing routes: the older chlorohydrin process, co-production with styrene or tert-butyl alcohol via hydroperoxide epoxidation, the cumene hydroperoxide recycle route, and direct epoxidation with hydrogen peroxide in the HPPO process.
Why does water content matter so much in polyol production?
Because water acts as an unintended starter molecule in the polyol chain-building reaction, broadening the molecular weight distribution and shifting foam properties. The specification is tight for that reason, not for purity cosmetics.
How does propylene oxide differ from ethylene oxide?
PO is a liquid at ambient temperature with a methyl group that adds a chiral centre and moderates reactivity. EO is a gas, more reactive, and flammable even without air. Both are Category 1B carcinogens requiring closed handling.
Is propylene oxide hazardous?
Yes, severely. It is extremely flammable with a flash point near −37 °C, a Category 1B carcinogen and mutagen, acutely toxic, and capable of runaway polymerisation if contaminated with acid, alkali or rust.
What are the UN number and transport class?
UN 1280, propylene oxide, Class 3 flammable liquid, packing group I. ADR, IMDG, IATA and DOT rules apply to tank design, labelling and routing.
How should propylene oxide be stored?
Under nitrogen pad in clean, dry, rust-free vessels with temperature monitoring and alarms, in cool, earthed and bunded flammable-liquid storage, strictly segregated from acids, bases and amines.
Why do chloride limits matter?
Because chlorohydrin-route PO can carry chloride residues that corrode equipment and poison polyol catalysts. Buyers with sensitive catalyst systems often specify the production route as well as the chloride figure.
Should I buy PO or propylene glycol?
Unless you run a polyol or glycol unit, buy the glycol. PO handling requires nitrogen padding, closed transfer and carcinogen controls that only justify themselves at production scale.
What packing sizes and order quantities are available?
200 L drums, ISO tank containers and road tankers, all nitrogen padded. Orders run from a pallet of drums up to repeat bulk shipments on contract supply.
Ready to source Propylene Oxide?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.