1. School of Chemical Engineering, Chemical Engineering Research Center of the Ministry of Education for Advanced Use Technology of Shanbei Energy, Shaanxi Research Center of Engineering Technology for Coal Conversion; Northwest University; Xi'an 710069 P.R. China
2. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences; Dalian 116023 P.R. China
3. University of Chinese Academy of Sciences; Beijing 100049 P.R. China