Abstract
In this work, LaMO3 (M = Co, Cr, Cu, Fe, Mn, Ni, Zn) perovskites were synthesized using solgel method. These catalysts were fully characterized using various techniques and then applied as heterogeneous catalysts in oxidation, reduction, and hydrogenation reactions. The d-orbitals of a transition metal in ABO3 perovskite system are in BO6 octahedral coordination environment. When this system undergoes Jahn-teller distortions it can lead to orbital splitting namely eg and t2g orbital sets. The eg orbital occupancy has been used as activity descriptor in many catalytic reactions. Herein, we focus on sub-orbital (dz 2) of eg orbital set which has proved to be the main descriptor for catalytic activity in oxidation of morin. The kinetic experiments were carried using Plate reader fluorescence with morin showing its absorption peak intensity at λmax= 400 nm and decreases over time until reaction reach its completion. Electronic properties of synthesized structures were studied by DFT calculations then correlate with kinetic experimental data to explain the activity. The depletion of fossil fuels has raised many concerns. Biomass which is abundant serves as an alternative to overcome this crisis. Biomass derived compounds such as furfural can be converted into value-added chemicals and fuel additives using hydrogen gas or hydrogen donor compounds. In this work, the LaMO3 (M = Co, Fe, Mn) perovskites were used as heterogeneous catalysts in hydrogenation of furfural to furfuryl alcohol. The hydrogenation of furfural is one of the important catalytic reaction which take different conversion pathways leading to valueadded chemicals which have found applications in industrial processes. Oxygen vacancies of La-based inorganic perovskites deduced from XPS analysis were used as main activity descriptor. Herein, we found that the catalysts with the most oxygen vacancies gave higher conversions than the one with the least amount of oxygen vacancies. Catalytic reductive degradation of 4-nitrophenol and catalytic oxidative degradation of methylene blue over LaMO3 (M= Cr, Fe, Mn) perovskites were investigated using kinetic analysis. These reactions can be easily monitored by spectroscopic techniques such as UV-vis spectrometer. In the 4-nitrophenol reduction reaction, NaBH4 was used as a reducing agent while in the oxidation reaction of methylene blue H2O2 was used an oxidizing agent. The catalytic activity trend was explored by XPS analysis of the perovskite catalysts using electronic structures and oxygen vacancies as descriptors. We observed that the amount of oxygen vacancies has minimal influence on the activity trend in these redox conversions.
M.Sc. (Chemistry)