TAIPEI (Bloomberg) -- Chinese Petroleum Corp., Taiwan's state oil refiner, bought 75,000 metric tons of so called full-range naphtha for delivery in September at a discount of about U.S.$7 a metric ton below benchmark prices, said a company official.

The cargo will be delivered to Kaohsiung port in southern Taiwan between Sept. 16 and Sept. 30.

The cargo was bought cost- and-freight, requiring the seller to pay for the shipping costs, and priced against Japan quotes for the fuel by oil-pricing service Platts, said the official who asked not to be identified.

Prices of Asian naphtha, which closed at U.S.$643.50 a ton yesterday, have risen 25 percent this year, according to data compiled by Bloomberg.

Brent crude oil prices in London gained 27 percent over the same period.

The Taipei-based company last bought a 75,000 ton cargo of full-range naphtha at a premium of about U.S.$2 a ton above the benchmark prices for delivery to Kaohsiung between Aug. 16 and Aug. 31.

Chinese Petroleum, which can process 720,000 barrels of crude oil a day, also operates three naphtha processing units, or crackers, with a combined capacity to produce 1.1 million tons of ethylene a year.

Ethylene is the building block of plastics used in the manufacture of electronics, auto parts, and soft drink bottles.

Naphtha, distilled from crude oil, is a raw material for chemicals and gasoline. Full-range naphtha is preferred by chemical makers because of the fuel's high ethylene yield.