Metallurgical Corp of China Ltd plans to sell as much as HK$19.6 billion ($2.5 billion) of stock in Hong Kong's biggest initial public offering in 18 months, said two people familiar with the matter.

The sale of as many as 2.87 billion shares at HK$6.16 to HK$6.81 apiece will raise as much as HK$17.8 billion for the company and HK$1.78 billion for the National Social Security Fund, the people said, declining to be named before an announcement. The State-owned construction and engineering company is also selling stock in Shanghai.

Metallurgical's IPO will be the largest in Hong Kong since China Railway Construction Corp's HK$20.2 billion offering in March 2008, as an economic recovery buoys demand for Chinese stocks. The Hang Seng China Enterprises Index tracking mainland incorporated companies traded in Hong Kong gained 49 percent this year, rebounding from its steepest decline in 2008.