1. Chemical Reaction Engineering Laboratory, Department of Chemical Engineering, Washington University, Campus Box 1198, One Brookings Drive, St. Louis, Missouri 63130, Department of Chemical Engineering, Laval University & CERPIC, Québec, Canada G1K 7P4, and Laboratorie des Sciences du Genie Chimique, 1 Rue Grandville BP, 451-54001 Nancy Cedex, France