1. Catalysis Laboratory, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, South Korea, Department of Chemical Engineering, Yonsei University, Shinchondong 134, Seodaemoonku, Seoul, Korea, and A.V. Topchiev Institute of Petrochemical Synthesis, Leninsky Prospect, 29, 117912 Moscow, B-71 Russia