1. Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi, P. R. China
2. Department of Chemical Engineering and Department of Petroleum Engineering, University of Wyoming, Laramie, Wyoming 82071, United States
3. School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
4. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Shanxi, P. R. China