Abstract
This work reports on the synthesis, characterization, and catalytic activity of ABO3 perovskites synthesized by the nanocasting technique. Perovskites received much attention in heterogenous catalysis as efficient alternatives to noble metals. These perovskites are well known for their high surface areas, thermal stability, and good catalytic activity. For these reasons, various ABO3 perovskites were synthesized and evaluated for their catalytic activity.
The catalytic activity of the as-synthesized perovskites was evaluated using acetalization reaction of glycerol with cyclohexane. Perovskites containing tin (Sn) at the A or B position of the ABO3 structure showed better catalytic activity. Their catalytic activity was influenced by the acidic nature of the perovskites. The as-synthesized perovskites were also evaluated for catalytic activity via the reduction of 4-nitrophenol (4NP). The Langmuir-Hinshelwood kinetics model was applied to elucidate the mechanism of the surface reaction. The model assumes that both glycerol and cyclohexane adsorbed onto the surface of the catalyst. This led to the successful elucidation of the surface mechanism using electron scavengers such as KI, EDTA, Na2S2O3, and Na2SO4 and the results showed that the reduction of 4NP follows a surface-driven electron transfer mechanism.
Furthermore, the effect of TiO2 and SiO2 supports was studied by immobilizing LaFeO3 and LaSnO3 perovskites on TiO2 and SiO2 supports. The supported perovskites were evaluated using esterification and hydrogenation reactions. The catalytic results showed that supporting perovskites on TiO2 and SiO2 improves the catalytic activity of the perovskites in both esterification and hydrogenation reactions. Furthermore, the low surface areas observed in supported perovskites did not affect their catalytic activity.