C-13 DIPOLAR NMR-STUDY OF BENZENE CHEMISORBED ON HIGH-SURFACE ALUMINA-SUPPORTED PLATINUM

NMR spectroscopy of dipole-coupled pairs of C-13 nuclei is employed to probe the molecular structure and dynamics of benzene molecules chemisorbed on a Pt/eta-Al2O3 catalyst. A modified Carr-Purcell sequence, which suppresses inhomogeneous broadening, permits good spectral resolution over a broad temperature range. A comparison between spectral data and computer simulations indicates more than one type of site for the chemisorbed molecules. The molecular structure appears to be indistinguishable from that in polycrystalline benzene but with a vastly different motional behavior.