Urea-Nitrate Combustion Synthesis and Physicochemical Characterization of CuO-ZnO-Al2O3 Nanoparticles over HZSM-5

A series of CuO-ZnO-Al2O3 nanocomposites over HZSM-5 (CZA/HZSM-5) have been synthesized by urea-nitrate combustion method. The influence of the fuel to oxidant ratio on the physicochemical properties of synthesized nanocomposites has been studied. The thermal decomposition of urea-nitrate gels and the phase evolution of calcined powder were investigated by TGA/DTG, FTIR and XRD techniques. The FESEM results show that the properties of the CZA/HZSM-5 are significantly influenced by fuel content used in the combustion process. The crystalline size of the CuO and ZnO initially increases with the increase in urea content and then decreases with further addition of urea. The relative crystallinity of CuO and ZnO shows non monotonic trend with increasing of fuel content. With increasing of fuel to nitrate ratio, not only the morphology of the CZA/HZSM-5 becomes ultra-fine and homogeneous, but also the surface porosity increases obviously. FTIR results show that HZSM-5 structure is not damaged even after loading with CuO-ZnO-Al2O3 nanoparticles and there are external linkages between CuO and ZnO with HZSM-5. TGA/DTG curves indicate that the combustion synthesis method is a combination of several phenomena such as thermal decomposition of precursors and exothermal reactions between them. Furthermore, a formation channel of CuO-ZnO-Al2O3 over HZSM-5 was proposed.