Solid-State NMR Investigations of Supported Ionic Liquid Phase Water-Gas Shift Catalysts: Ionic Liquid Film Distribution vs. Catalyst Performance

Abstract

The ionic liquid film distribution in supported ionic liquid phase (SILP) catalysts has been studied by solid-state NMR. EMIMNTf2 was immobilized onto silica gel 100 support with loadings between 0 and 40?vol.-%. The 1H NMR signals indicated an exchange process between the support's surface silanol groups and the protons of the ionic liquid. At ionic liquid loadings below 10?vol.-%, islands of ionic liquids seemed to form, whereas at higher loadings complete coverage of the support was achieved. The NMR-based film model was confirmed by gas phase water-gas shift experiments using known SILP catalysts with different ionic liquid loadings. At high ionic liquid loading, the activity of the catalyst decreased due to pore blocking. The NMR technique provided easy and reliable data for film formation and distribution and allows for optimization of SILP catalysts in the future