1. State Key Laboratory of Heavy Oil Processing; Institute of New Energy; China University of Petroleum (Beijing); Beijing 102249 P.R. China), Fax: (+86) 010-89731300
2. Anhui Province Key Laboratory of Biomass Clean Energy; Department of Chemistry; University of Science and Technology of China; Hefei 230026 P. R. China), Fax: (+86) 551-3606689