Multinuclear NMR study of the structure and dynamics of supported metal oxide catalysts

A review of previously reported research in the area of solid acid catalyst characterization for sulfate promoted zirconium oxide is described in Chapter 1. Chapter 2 reports the characterization of the metal sites by solid state NMR coupled with thermal analysis methods. Experiments performed using solid state {dollar}sp{lcub}119{rcub}{dollar}Sn NMR to characterize sulfate promoted tin oxide were successful and reveal the presence of a disordered surface even during a phase change from an amorphous to crystalline material. In Chapter 3, the characterization and catalytic activity measurements are described for a series of unmodified and pH modified sulfate promoted zirconium oxide catalysts. Samples were modified by adjusting the pH of the sulfate soaking solutions with either NH{dollar}sb4{dollar}OH or NaOH. Samples modified in the pH range between 6-9 showed the highest percent yield of iso-butane for the isomerization of n-butane to iso-butane at 220{dollar}spcirc{dollar}C. In Chapter 4, {dollar}sp1{dollar}H solid state NMR experiments were used to characterize Bronsted acid sites on sulfate promoted zirconium oxide. {dollar}sp1{dollar}H variable temperature NMR results show a two component lineshape for catalyst samples calcined at 600{dollar}spcirc{dollar}C. The two components can be separated by subtraction techniques through the use of T{dollar}sb1{dollar} relaxation measurements. From CRAMPS experiments, the two components are separated based on chemical shifts and correlated with catalytic activity. The catalytically important proton species has a chemical shift value of 2 ppm while the bulk proton species has a value of 8 ppm. Chapter 5 describes efforts to obtain quantitative results from {dollar}sp{lcub}27{rcub}{dollar}Al NMR experiments on aluminum oxide materials. The observation of decreased {dollar}sp{lcub}27{rcub}{dollar}Al NMR intensity as a function of sample surface area can be explained by changes in the population fraction of different sites rather than the presence of large electric field gradients on the surface. Results also indicate that the surface of alumina is static rather than dynamic as previously proposed.