The facility in the southwest Trinidadian town of La Brea would produce methanol and dimethyl ether. The Caribbean islands' government says it will be a collaborative effort with Japan's Mitsubishi Corp. and others.
A signing ceremony was held earlier this week. Financial terms were not disclosed Friday and it wasn't clear when production might start.
Japanese Ambassador Mitsuhiko Okada says the plant will be the largest investment the Asian nation has ever made in Trinidad.
Earnings from natural gas and oil made Trinidad one of the richest countries in the Western Hemisphere in recent decades. But the economy has been hurt by a collapse in world oil prices.