Preparation, characterisation and selective hydrocarbon transformation applications of flatmodel and zeolite-supported platinum catalysts

English: Allyl, amino and silanol (Si-OH) functionalised silicon wafers with epitaxial layer of SiO2 (SiO2/Si-wafers) were used as two-dimentional supports to prepare flat model Pt/SiO2/Si-wafer catalysts by spin coating and grafting of suitable platinum precursors followed by calcination and reduction. X-ray photoelectron spectroscopy (XPS) revealed that H2PtCl6 reacted with surface allyl groups to form π-olefin Pt2+ supported complexes. Residual Si-OH groups also reacted with H2PtCl6 to form Pt4+ species. Together, the different surface Pt species formed a heterogeneous coating on the surface of Si-wafer. The platinisation of aminated silicon surfaces with K2PtCl4 dissolved in aqueous ethanol resulted in the reduction of the Pt(II) precursor and immobilisation of the resultant metallic Pt particles on the model Si-wafer. Calcination and reduction of the surface Pt species resulted in the formation of relatively small Pt particles, 1-5 nm average particle diameter, which interacted with the silicon surface via boundary Pt2+-O-Si bonds or Pt2+-N-Si bonds. The prepared flat model Pt/SiO2/Si-wafer catalysts had catalytic activity in solvent-free aerobic oxidation of 1-octadecanol to carbonyl compounds. A selection of the prepared flat model Pt/SiO2/Si-wafer catalysts were also shown to have activity in hydrogenation of alkene and carbonyl functional groups. The preparation and characterisation of Pt catalysts supported on alkaline KL-zeolite and acidic HY-zeolites are also described. Two types of Pt/KL-zeolite catalysts were investigated. Those Pt/KL-zeolite catalysts prepared by vapour phase impregnation had a high particle dispersion (91.5 % vs. 75.8 %) and smaller particles sizes (average diameter = 1.2 nm vs.1.5 nm) compared to the equivalent Pt/KL-zeolite catalysts that were obtained by incipient wetness impregnation. In aromatisation of n-alkanes, the Pt/KLzeolite catalysts obtained by vapour phase impregnation were more active and more tolerant to oxygenates present in the feed than the Pt/KL-zeolite catalysts obtained by incipient wetness impregnation. A correlation between the concentrations of acetic acid in the feed, the amount of coke deposit on spent catalysts and catalyst deactivation was established. Pt/KL-zeolite and Pt/HY-zeolite catalysts were also applied in liquid phase oxidation of primary alcohols under mild conditions (ca.100 °C and ambient pressure). Moderate substrate conversion (10-40 %) was achieved.