1. Lehrstuhl für Technische Chemie (FB9), Carl von Ossietzky Universität Oldenburg, Postfach 2503, D-26111 Oldenburg, Germany, Hüls Infracor GmbH, experSCience, D-45764 Marl, Germany, Department of Chemical Engineering, Tsinghua University, Beijing, China, and Aventis Research and Technology GmbH & Co. KG, Industriepark Hoechst, D-65929 Frankfurt am Main, Germany