China's Sinochem plans to raise up to 35 billion yuan ($5.5 billion) via an initial public offering in Shanghai, in what would easily be the biggest IPO in the mainland market in the past year.

The firm, which has businesses ranging from oil exploration to chemicals to property, will use the proceeds to fund a refinery project in Quanzhou, it said in a filing posted on the environment ministry's website.

In July, Sinochem obtained approval from the environmental watchdog for the 240,000 barrel-per-day plant in the southeastern province of Fujian.

Sinochem plans to sell up to 26.5 billion new shares, or 40% of its enlarged capital, to raise 20-35 billion yuan through the IPO, it said.

Companies with operations that impact the environment, such as miners and oil refinery operators, first need to obtain clearance from the environment ministry before seeking approval from the securities regulator for IPOs, a process that could take months.

Analysts said it was too early to tell how the Sinochem deal would fare, given the uncertain timeframe, though some think demand may not be so strong.

"Compared with more upstream-focused firms such as PetroChina and Sinopec, it doesn't have the same gas resource advantage," said Ao Chao Wang, at UOB Kay Hian in Shanghai.

"The market may not get very excited about a listing. Additionally the market demand is not that strong at the moment."

Sinochem Corp was established in 2009 as the result of a group restructuring of Sinochem Group, which owns four listed units including Sinochem International Corp, Sinofert Holdings, Franshion Properties (China) and Far East Horizon

"The stock market is suffering from a shortage of liquidity, mainly due to pessimism toward the real estate market and the broader economy. Unless investors see concrete evidence of monetary easing, the current rebound is not sustainable."

The benchmark Shanghai stock index has recovered 7.5% after hitting a one-and-a-half-year low on Oct. 21, but it is still down 11.7% so far this year.