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 chemi sorbed on a Pt/eta-Al2O3 catalyst. A modified Carr-Purcell sequence, w hich suppresses inhomogeneous broadening, permits good spectral resolu tion over a broad temperature range. A comparison between spectral dat a and computer simulations indicates more than one type of site for th e chemisorbed molecules. The molecular structure appears to be indisti nguishable from that in polycrystalline benzene but with a vastly diff erent motional behavior.