The China Petroleum and Chemical Corporation, Asia's largest oil refiner, will buy the Hong Kong petroleum products distribution unit of China Resources Enterprise for 4 billion Hong Kong dollars ($511 million).

The two companies signed a framework agreement, and the final purchase price remains subject to review, according to China Resources. A formal agreement will be signed in mid-April, the company said.

The Beijing-based China Petroleum and Chemical, which is known as Sinopec, is expanding its refining and fuel distribution system to keep pace with the rapidly growing Chinese economy.