1. Institute of Oil & Gas, Peking University, No. 5 Yiheyuan Road, Beijing 100871, China e-mail:
2. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, No. 66 Changjiang West Road, Qingdao 266580, China e-mail:
3. e-mail:
4. e-mail: Institute of Oil & Gas, Peking University, No. 5 Yiheyuan Road, Beijing 100871, China
5. e-mail: State Key Laboratory of Heavy Oil Processing, China University of Petroleum, No. 66 Changjiang West Road, Qingdao 266580, China