Propylene Oxide

Propylene Oxide is a strained three-membered epoxide ring carrying a methyl substituent on one ring carbon. The ring strain makes the molecule highly reactive toward nucleophiles — water, alcohols, amines and acids all open the ring readily, which is the chemical basis of its two dominant industrial roles: building long polyether chains by repeated ring-opening, and hydrolysing cleanly to propylene glycol.

At room temperature and atmospheric pressure it is a colourless, highly volatile, flammable liquid with a characteristic ether-like odour, boiling just above room temperature. Commercial material is handled refrigerated or under slight pressure and is typically supplied uninhibited for immediate downstream use given its reactivity, though short-term stabilisation is possible for specific logistics needs.

Where it fits in the value chain

Propylene Oxide's single largest end use is ring-opening polymerisation with a starter polyol and a basic or double-metal-cyanide catalyst to build polyether polyols, the backbone raw material of flexible and rigid polyurethane foams, elastomers and coatings. Its second major use is controlled hydrolysis with water to give propylene glycol (mono-, di- and tripropylene glycol, separated by distillation), and reaction with surfactant alcohols gives propylene glycol ethers, widely used as coating and cleaning solvents. A smaller but established use is as a fumigant/sterilant for certain food and pharmaceutical raw materials, subject to strict regulatory control.

Grade we supply

Chelora Chemicals offers Propylene Oxide in polymer grade (99.9%+ purity), suited to polyether polyol polymerisation and propylene glycol hydrolysis chemistry. The grade is supplied with a batch-wise certificate of analysis.

Propylene Oxide is produced industrially by three main routes. The chlorohydrin process reacts propylene with chlorine and water to form propylene chlorohydrin, which is then treated with lime or caustic soda to eliminate HCl and close the epoxide ring; it is the oldest commercial route and remains in use in some regions despite generating a chlorinated by-product stream. The hydroperoxide (co-product) processes react propylene with an organic hydroperoxide — ethylbenzene hydroperoxide in the styrene-monomer/propylene-oxide (SM/PO) process, or tert-butyl hydroperoxide in the PO/MTBE process — over a molybdenum or titanium catalyst, which epoxidises propylene while reducing the hydroperoxide to a valuable co-product (styrene or tert-butanol) that is recovered and sold alongside the PO.

A newer route, the HPPO (hydrogen peroxide to propylene oxide) process, reacts propylene directly with hydrogen peroxide over a titanium silicalite catalyst, producing only water as a by-product and avoiding both the chlorinated waste of the chlorohydrin route and the co-product dependency of the hydroperoxide routes; it has grown in adoption as a lower-waste alternative where hydrogen peroxide supply economics allow.