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Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics. It is a chiral epoxide, although it is commonly used as a racemic mixture.

This compound is sometimes called 1,2-propylene oxide to distinguish it from its isomer 1,3-propylene oxide, better known as oxetane.

Industrial production of propylene oxide starts from propylene. Two general approaches are employed, one involving hydrochlorination and the other involving oxidation. In 2005, about half of the world production was through chlorohydrin technology and one half via oxidation routes. The latter approach is growing in importance.

Hydrochlorination route

The traditional route proceeds via the conversion of propylene to chloropropanols:

The reaction produces a mixture of 1-chloro-2-propanol and 2-chloro-1-propanol, which is then dehydrochlorinated. For example:

Lime is often used as a chlorine absorber.

Co-oxidation of propylene

The other general route to propylene oxide involves co-oxidation of the organic chemicals isobutane or ethylbenzene. In the present of catalyst, air oxidation occurs as follows:

CH3CH=CH2 + Ph-CH2CH3 + O2 → CH3CHCH2O + Ph-CH=CH2 + H2O
The coproducts of these reactions, t-butyl alcohol or styrene, are useful feedstock for other products. For example, t-butyl alcohol reacts with methanol to give MTBE, an additive for gasoline. Before the current US ban of MTBE, propylene/isobutane was one of the most important production process.

Oxidation of propylene

In April 2003, Sumitomo Chemical commercialized the first PO-only plant in Japan, which produces propylene oxide from oxidation of cumene without significant production of other products.[6] This method is a variant of the POSM process (co-oxidation) that uses cumene hydroperoxide instead of ethylbenzene hydroperoxide and recycles the coproduct (alpha-hydroxycumene) via dehydration and hydrogenation back to cumene.

In March 2009, BASF and Dow Chemical started up their new HPPO plant in Antwerp. In the HPPO-Process, propylene is oxidized with hydrogen peroxide:

CH3CH=CH2 + H2O2 → CH3CHCH2O + H2O
In this process no side products other than water are generated.

Source: https://en.wikipedia.org/wiki/Propylene_oxide