How styrene is made

Left alone, the liquid turns itself into plastic. Plants must keep dosing it to stop that happening inside the pipes.

stations: 5
things upstream: 9
raw sources: 4
steps from the ground: 5

The short version

Benzene and ethylene join over a zeolite catalyst to make ethylbenzene. Superheated steam and an iron oxide catalyst then pull two hydrogen atoms off, leaving a sweet-smelling oily liquid with a reactive double bond. That bond is what makes it useful, and also why it needs an inhibitor to keep it from turning solid on its way to market.

Join benzene and ethylene

The two petrochemicals react over a zeolite catalyst to give ethylbenzene. Older plants used aluminum chloride for this. More than 99% of ethylbenzene goes straight on to the next step.

Goes in
Benzene Ethylene
Strip off two hydrogens

Ethylbenzene meets superheated steam over an iron oxide catalyst, and hydrogen comes off. The reaction soaks up heat and can run backward, so yields stop at 88 to 94 percent.
Dose with inhibitor

Heat makes the product link up into polymer on its own. An inhibitor is added continuously during the hot stages so that the columns ahead do not fill with plastic.
Distill through many columns

Crude product and leftover ethylbenzene boil only 9 °C apart, so a whole series of distillation columns is needed to split them. It takes a lot of energy.
Ship before it sets

Treated liquid travels by tanker to plants making polystyrene, ABS and styrene-butadiene rubber. Without the inhibitor it would polymerize in storage.

End of the lineStyrene Next it goes into polystyrene, abs plastic, synthetic rubber.

Worth repeating

The compound was first isolated from storax, a balsam from a flowering shrub, and takes its name from it.
At 100 °C the pure liquid polymerizes itself at about 2% per hour.
World output reached around 35 million tonnes by 2018.