1. School of Chemistry and Chemical Engineering; Jiangsu University; Zhenjiang 212013 P. R. China
2. College of Chemistry and Chemical Engineering; Hainan Normal University; Haikou 571158 P. R. China
3. Institute for Energy Research, Jiangsu University; Zhenjiang 212013 P. R. China
4. State Key Laboratory of Coal Conversion; Institute of Coal Chemistry, Chinese Academy of Sciences; Taiyuan 030001 P. R. China