Abstract:
In recent years, environmental and economic considerations have promoted process innovation towards cleaner technologies. Therefore, it is desirable to use heterogeneous catalysts that can perform under milder reaction conditions. In the present work, different types of nanocatalysts in single, binary and ternary systems with different molar ratios (1:1, 2:1, 3:1 and 4:1) of CdS/ CeO2/Ag3PO4 and ternary nanocomposites like CdS/ZnO/Ag3PO4 (10:80:10 molar ratios), Fe3O4/ZrO2/Al2O3 (70: 05: 25 molar ratios) and CdS/UiO-66/Ag3PO4 (4:1 molar ratio) were synthesized by precipitation method. Crystal structure, morphology and surface functional groups of the as synthesized single, binary and ternary systems of CdS/CeO2/Ag3PO4 nanocatalysts were characterized by using XRD, SEM-EDX and FTIR respectively. And also CdS/ZnO/Ag3PO4, Fe3O4/ZrO2/Al2O3 and CdS/UiO-66/Ag3PO4 were characterized by using XRD and SEM. The catalytic activities of CdS/ZnO/Ag3PO4, CdS/CeO2/Ag3PO4, Fe3O4/ZrO2/Al2O3 and CdS/UiO-66/Ag3PO4 were evaluated by applying to the Knoevenagel condensation reaction between aromatic aldehydes and malononitrile. The effect of solvents, concentration of malononitrile/acetic anhydride, catalyst load and temperature were optimized for further reactions. The catalytic activities of CdS/CeO2/Ag3PO4 (4:1) nanocomposite (95%) was found to be higher than those of other as-synthesized ternary composites. Then catalytic activities of single, binary and different molar ratios (1:1, 2:1, 3:1 and 4:1) of CdS/CeO2/Ag3PO4 nanocomposite were evaluated via Knoevenagel condensation reaction between benzaldehyde and malononitrile. From the result, CdS/CeO2/Ag3PO4 (4:1) nanocomposite showed higher catalytic activity (95.4 ± 3.2%) than single, binary and other molar ratios and then used for further application of acetylation and esterification reactions. The reusability of the nanocatalyst was tested and only about 7.5±2% decrement was observed after four successive runs and 23.3% after five runs.
