MCr2O4 (M=Co, Cu, and Zn) nanospinels for 2-propanol combustion: Correlation of structural properties with catalytic performance and stability

Abstract

Abstract The correlation between structure and activity of MCr 2 O 4 nanospinels (M=Co, Cu, and Zn) synthesized by a sol–gel combustion method was investigated for the oxidation of 2-propanol. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N 2 adsorption/desorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Wide-angle XRD patterns show that the samples are pure spinel phases with cubic structure for CoCr 2 O 4 and ZnCr 2 O 4 , and tetragonal structure for CuCr 2 O 4 . FTIR spectra confirmed the spinel structure of samples. The spinels were tested for total oxidation of 2-propanol as a model reaction for the catalytic combustion of oxygenated organic pollutants. ZnCr 2 O 4 exhibited the highest activity and stability than the others toward the combustion of 2-propanol. The higher activity of ZnCr 2 O 4 was ascribed to existence of excess surface oxygen on catalyst, active Cr 3+ –Cr 6+ pair sites, and synergistic effect between ZnO and ZnCr 2 O 4 confirmed by TPR and XPS techniques. The high stability of ZnCr 2 O 4 and CuCr 2 O 4 was explained by the existence of stable Cr 6+ species on the surface of catalysts. The study showed that ZnCr 2 O 4 could be used as a promising catalyst in the catalytic conversion of organic compounds.