CHARACTERIZATION OF SILICA CATALYST SUPPORTS BY SINGLE AND MULTIPLE-QUANTUM PROTON NMR-SPECTROSCOPY


HWANG S., UNER D. , KING T., PRUSKI M., GERSTEIN B.

JOURNAL OF PHYSICAL CHEMISTRY, vol.99, no.11, pp.3697-3703, 1995 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 99 Issue: 11
  • Publication Date: 1995
  • Doi Number: 10.1021/j100011a042
  • Title of Journal : JOURNAL OF PHYSICAL CHEMISTRY
  • Page Numbers: pp.3697-3703

Abstract

Cab-O-Sil HS5, used as the support in silica supported ruthenium (Ru/SiO2) catalysts, was characterized via single and multiple quantum (MQ) H-1 NMR spectroscopy. The samples were studied both in the presence and in the absence of ruthenium. Single quantum spin counting of protons on silica support with and without ruthenium metal indicated that the total number of hydroxyl groups decreased significantly with increasing reduction temperature over the range of 350-530 degrees C. Two different components shown in static H-1 NMR were found to reveal homogeneous and inhomogeneous broadening via spectral hole burning experiments. H-1 MQ-NMR spin counting, based on the number of MQ coherences observed, showed the existence of small clusters of proton spins on the silica surface. The maximum measured cluster size was 6-7, or less, spins. Segments of silica resembling the 100 face of cristobalite on the surface are postulated to be possible sites for the clusters. The clusters in pure silica became smaller as the reduction temperature increased over 500 degrees C. No such change was detected in the presence of ruthenium.