Ineos said it had selected the location for a new ethane tank it plans to build at Grangemouth in Scotland, with imports beginning as early as 2016 after a £150 million investment to an import terminal project.
The move will supplement declining North Sea supplies, said Ineos, which threatened to close the petrochemical site in October after a dispute with the Unite union.
The company decided to keep the site open after workers accepted changes to pay, pensions and terms and conditions.
Calum MacLean, chairman of Ineos Petrochemicals UK, said: "This investment is absolutely critical for Grangemouth. Without a second advantaged feedstock supply chain, the petrochemicals business is not sustainable beyond 2017.
"We are delighted to report that Ineos are making good progress on the project that will give Grangemouth a long-term sustainable future.
"After what has been a very difficult three months at Grangemouth, it is very reassuring for our employees to see real progress being made on the tank and infrastructure project.
"The next three years will remain challenging for the Grangemouth site but with a clear focus and support of its shareholders, the site can look forward to a bright future."
Ineos said the announcements were part of its survival plan detailed to staff in October, adding that Grangemouth has lost around £150 million a year over the last three years.
The company has submitted applications to the Scottish Government for a grant of £9 million and a loan guarantee of £125 million.
Unite has warned that up to 200 workers at Grangemouth are set to lose their jobs under cost-cutting moves.
The union said five plants at the huge site will close, while shift payments will be cut by £2,500 a year and new employees will receive lower wages.
Unite's Scottish secretary Pat Rafferty said: "We shouldn't forget that this new facility has only been made possible because of the welcome investment by Scottish and UK taxpayers and the sacrifice of the workforce.
"As the consultation on Ineos's survival plan ends it is becoming clear that part of this sacrifice is the closure of some of the site's plants and job losses. Ineos needs to come clean over job losses, the timescales involved and provide assurances to the workforce this Christmas."