1. Institute of Coal Chemistry; Chinese Academy of Sciences; Taiyuan 030001 P.R. China
2. College of Chemistry and Chemical Engineering; Jinzhong University; Jinzhong 030619 P.R. China
3. University of Chinese Academy of Sciences; Beijing 100049 P.R. China
4. Institute of Applied Chemistry College of Chemistry; Nanchang University; Nanchang 330031 P.R. China