1. State Key Laboratory of Heavy Oil, China University of Petroleum (East China), Qingdao, Shandong 266580, P. R. China
2. School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo, Shandong 255000, P. R. China
3. Shaanxi Coal Chemical Industry Technology Research Institute Co. Ltd, Xi’an, Shaanxi 610100, P. R. China