1. Clean Energy Research Center, Korea Institute of Science and Technology, P.O.Box 131, Cheongryang, Seoul 130-650, Korea, Research Center for Chemistry, Indonesian Institute of Sciences (LIPI), Kawasan PUSPIPTEK Serpong, Tangerang, Indonesia, and Department of Chemical Engineering, Seoul National University of Technology, 172 Gongreung 2-dong, Nowon-gu, Seoul 139-743, Korea