The UK government and owners Ineos say the funding will support 500 jobs at the site's ethylene plant.
Choices over oil, gas, nuclear and the transition to renewables are to set to feature highly in the debate and battle for votes.
Up to 460 roles are expected to be created at the site of the former oil refinery and across Scotland.
Academics say the Acorn project in Aberdeenshire is facing difficulties, but the company insists it is viable.
Scotland's only oil refinery stopped processing crude oil at Grangemouth in April, after a century of operations.
It is half a century since the Forties field was inaugurated - one of the first in the North Sea.
Ministers have also been told they should have been better prepared for the closure of the Grangemouth refinery.
The co-leaders pledged to "bring hope back to this country's politics" during their first conference speech after they were elected in August.
The Falkirk area has been hit by the loss of jobs at two major employers in the past year.
