1. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001, P. R. China
2. Taiyuan University of Technology, Taiyuan, 030001, P. R. China
3. University of Chinese Academy of Sciences, Beijing 100049, P. R. China
4. Faculty of Science, Kunming University of Science and Technology, Kunming, 650500, P. R. China