China's two largest state-owned energy companies Petrochemical Group (Sinopec Group) and China National Petroleum Corp. (CNPC) appointed new chairmen on Friday. 

CNPC has appointed Dai Houliang as chairman, replacing Wang Yilin who is retiring, CNPC said in a statement. Dai started his Sinopec management experience in 1997 as the deputy managing director of its subsidiary plant, Yangzi Petrochemical Corp., and later became Sinopec chairman.  

Zhang Yuzhuo, who once served as the chairman of China's largest coal miner Shenhua Group and in 2017 became the head of a special economic zone in Tianjin, has been appointed chairman of Sinopec, replacing Dai, Sinopec said on its official site.

CNPC owns nearly 80 percent of China's 80,000 kilometers (49,709 miles) of natural gas pipelines, and Sinopec Group 19 percent. They both rank in the top five of Forbes magazine's Global 500 companies, with each posting annual revenue of roughly 400 billion U.S. dollars. 

China has been accelerating the overhaul of its energy sector in recent years, including changes to its gas pricing policy and merging power and coal mining giants.