How propylene is made
Propylene is mostly a byproduct, shaken out of a steam cracker or of the refinery unit that makes gasoline.
- stations
- 5
- things upstream
- 5
- raw sources
- 3
- steps from the ground
- 3
The short version
Propylene is mostly a coproduct. A steam cracker making ethylene from naphtha also produces propylene, and a refinery's fluid catalytic cracker releases it as a gas while turning heavy oil into gasoline. In both cases, the gas is compressed, chilled and distilled apart from its neighbors.
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Crack naphtha with steam
In the steam cracker that makes ethylene, naphtha is heated for milliseconds and a stream of propylene comes out beside it. Heavier feeds give more propylene, and ethane gives almost none.
Goes in -
Crack heavy oil with a catalyst
In the refinery's fluid catalytic cracker, hot powdered catalyst meets vaporized heavy oil and breaks it into lighter molecules. The light gases include propylene, which refiners can collect or burn.
Goes in -
Quench and compress the gas
The gas leaving the cracker is cooled and compressed, with heavy liquids and water removed first. A compressed gas is easier to separate.
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Distill it away from ethylene
Propylene is separated from propane and ethylene in tall cold columns. Propylene and propane boil at nearly the same temperature, so these columns are among the tallest in a refinery.
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Store as a pressurized liquid
Purified propylene is liquefied under pressure and stored in spherical tanks. Polypropylene plants nearby take most of it.
Worth repeating
- Where propane is cheap, as in North America, plants also make propylene on purpose by stripping hydrogen from propane.
- Fluid catalytic cracking units were running at 400 refineries worldwide as of 2006, so refineries are a big second source of propylene.
Back to the ground
Follow every input upstream and propylene starts as these 3 raw sources.
Where it goes next
Propylene feeds 13 lines directly and reaches 304 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How propylene is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/propylene