An experimental and kinetic study of toluene oxidation over LaMn1-x B (x) O-3 and La(0.8)A(0.2)Mn(0.3)B(0.7)O(3) (A=Sr, Ce and B=Cu, Fe) nano-perovskite catalysts

摘要

Catalytic oxidation of toluene over perovskite-type oxides of the general formula LaMn1-xBxO3 (B=Cu, Fe and x=0, 0.3, 0.7) and La(0.8)A(0.2)Mn(0.3)B(0.7)O(3) (A=Sr, Ce and B=Cu, Fe) was investigated, where the catalysts were synthesized by sol-gel auto combustion method. The catalysts were characterized by XRD, BET, H-2-TPR, XPS, and SEM. Obtained XRD patterns confirmed the perovskites to be single-phase perovskite-type oxides. Specific surface areas of perovskites were obtained between 25-40m(2)/g. The perovskite catalysts showed high activity for the toluene oxidation. Based on the results, Fe-containing perovskite catalysts exhibited higher activity than Cu-containing perovskite catalysts. The substitution of Sr and Ce in A-site of the perovskite catalysts enhanced their activity for toluene oxidation. Among different synthesized catalysts in this research, La0.8Ce0.2Mn0.3Fe0.7O3 has the highest activity. Nearly complete elimination of toluene was achieved at 200 A degrees C with this catalyst. Based on Langmuir-Hinshelwood mechanisms, kinetic studies were conducted on toluene oxidation, indicating LH-OS-ND (adsorption of reagents on same types of sites and non-dissociative adsorption of oxygen) as the most probable mechanism which could predict the experimental data with correlation coefficient of R-2=0.9952.