Sviluppo di tecniche in regime transitorio per lo studio di reazioni di catalisi eterogenea

The research activities reported in this PhD thesis focus on one class of time-depending input variables: temperature and reactant concentration. Specifically, reactivity parameters (reagents conversion and products formation) were recorded as a function of temperature in temperature-programmed experiments with variable feed conditions (reducing or oxidizing atmospheres) and spent materials were characterized with surface analyses (SEM, EDS) to correlate their activity to chemical (mass and heat transfer) and physical (aggregation, segregation) phenomena. Also, the common feature between the catalytic materials investigated is the oxygen-storage capacity, i.e. their ability to store and release oxygen in oxygen-lean conditions, that represents a critical feature for more flexible operations, highly-selective oxidations and safer working conditions. Two model materials were selected as oxygen-donors for two distinct applications: CuO was chosen to correlate the effect of different reaction parameters to its morphological features, long-time stability during redox cycles (H2-O2) and formation of peculiar superficial nanostructures while LaFeO3 (perovskite) was identified as a possible candidate for the oxidative function, in automotive converter by taking advantage of oxygen diffusion in the lattice to transform CO into CO2. The last class of materials (CuY zeolites) was studied in CH4 activation to assess their potential application to an industrial-relevant reaction (methane-to-methanol, MTM) in which the oxygen provided by the zeolites selectively reduces the extent of over-oxidation products in favour of the partial oxidation to methanol.