Propylene oxide

A reactive three-carbon epoxide made from propylene, used mostly to make polyols for polyurethane foam and propylene glycol.

Commodity chemicals · Derivatives & intermediates · No. 38

• Single chemical
• Feedstock: Oil, gas or coal
• about 12 Mt produced a year (2025, indicative: about 16 Mt capacity x about 75%)
• 2.5 t CO₂e per t
• HS 291020

The foam in your mattress, sofa and car seat starts with a volatile liquid that boils at 34 C.

Chart: Illustration: Propylene oxide

Where it comes from

Chart: Map of where it comes from

Propylene is oxidised using chlorine, an organic hydroperoxide that leaves styrene or tert-butanol behind, or hydrogen peroxide. The peroxide route gives water as its only by-product.

Three things to know

1. Unlike its ethylene cousin, PO cannot be made by simple air oxidation at scale, so every route needs a costly oxidant or makes a by-product.
2. China's capacity was heading for about 9.3 Mt a year by end-2025, after 1.54 Mt of new units from June 2025.
3. The old chlorohydrin route uses about 1.4 t of chlorine per tonne and makes about 40 t of salty wastewater.

The journey

1. 1 Propylene0.75-0.8 t per tonne PO
2. 2 OxidantChlorine, hydroperoxide or hydrogen peroxide
3. 3 EpoxidationHPPO is over 95% selective
4. 4 PolyolsMade next door, since PO ships badly
5. 5 PolyurethanePolyol plus MDI or TDI makes foam

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