Ineos has announced plans to build a new European petrochemical production plant and boost capacity at plants in Scotland and Norway at a cost of about two billion euros (£1.8bn).
The plans include a new propylene production unit, with sites in Belgium among locations being considered.
It also plans to increase the ethylene capacity of its crackers at Grangemouth in Scotland and Rafnes in Norway.
Both rely on fracked shale gas being shipped across to Europe from the US.
Ethylene and propylene are key building blocks in the manufacture of plastics.
In a statement, Ineos said its investment would boost the amount of ethylene it can produce at each plant in Grangemouth and Rafnes by about 50%, to more than one million tonnes.
About 150 new jobs are expected to be created at each location, once the expansion of processing units is completed in three to four years' time.
Gerd Franken, from Ineos, said: "These expansions and new-builds will increase our self-sufficiency in all key olefin products and give further support to our derivative businesses and polymer plants in Europe.
"All our assets will benefit from our capability to import competitive raw materials from the US and the rest of the world."