1. Barrer Centre, Department of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K.
2. School of Chemistry, The University of Manchester, Manchester M13 9PL, U.K.
3. School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M1 3AL, U.K.
4. Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, U.K.
5. BP Chemicals Ltd Petrochemicals Technology, Saltend, Hull H12 8DS, U.K.