1. Department of Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
2. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China
3. College of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China
4. Department of Electrical and Computer Engineering, Texas A&M University, 188 Bizzell St., College Station, Texas 77843-3128, USA