1. Department of Chemical Engineering University of California Santa Barbara CA 93106 USA
2. Present address: Johnson Matthey Technology Centre Chilton P.O. Box 1, Belasis Avenue Billingham TS23 1LB UK
3. Laboratory of Crystallography ETH Zurich Vladimir-Prelog-Weg 5 8093 Zurich Switzerland
4. Present address: Kavli Institute of Nanoscience Delft University of Technology Van der Maasweg 9 2629 HZ Delft The Netherlands
5. Institut des Sciences Analytiques UMR 5280 (CNRS/Université Lyon 1/ENS Lyon) Université Lyon Centre de RMN à Très Hauts Champs 69100 Villeurbanne France
6. Chevron Energy Technology Company Richmond CA 94802 USA