Solid-state NMR characterization of heterogeneous catalysts

The application of solid-state NMR techniques assists scientists in the understanding of the geometry and structure of a variety of materials. In particular, NMR techniques were used to investigate silica supported palladium catalysts, an aluminophosphate catalyst, and a group of model organic compounds.; Several supported palladium catalysts were prepared using the ion-exchange technique and the incipient wetness impregnation technique. Labeled {dollar}sp{lcub}13{rcub}{dollar}CO molecules chemisorbed on the palladium surfaces displayed very broad NMR resonances. The Knight shift and the Korringa law were observed for catalysts with large palladium particles. CO surface dynamics and adsorbant-adsorbate interaction were studied using variable temperature relaxation measurements and hole-burning experiments. Catalyst preparation techniques were also discussed.; Rotational Echo Double Resonance technique (REDOR) and Transfer of Population in Double Resonance technique (TRAPDOR) provided qualitative dipolar coupling information on the aluminophosphate Virginia Polytechnic Institute #5 (VPI-5). TRAPDOR was also capable of yielding quadrupolar coupling and symmetry information. These rotor-driven techniques recover dipolar coupling information lost during magic angle spinning (MAS). One finds certain restrictions for TRAPDOR may be relaxed without sacrificing efficiency. TRAPDOR was capable of characterizing materials containing spin 1/2 and quadrupolar nuclei.; Spectral editing of {dollar}sp{lcub}13{rcub}{dollar}C CPMAS spectra was also investigated for a physical mixture of model organic compounds. The carbon composition of the mixture was chosen to mimic that of the Illinois #6 coal. The intensities of the non-protonated {dollar}rmsp{lcub}13{rcub}C, sp{lcub}13{rcub}CH, sp{lcub}13{rcub}CHsb2,{dollar} and {dollar}rmsp{lcub}13{rcub}CHsb3{dollar} groups determined from the subspectra are compared to the actual values of the model mixture. These experiments permit the placement of confidence limits on the numbers derived from spectral editing analysis of a complex mixture of hydrocarbons.