Catalytic oxidation of trichloroethylene from gas streams by perovskite-type catalysts

Promoting effect of Ru-doped Mn/TiO2 catalysts for catalytic oxidation of chlorobenzene

Mn/TiO2 catalysts were synthesized using deposition-precipitation method. Ru-doped Mn/TiO2 catalysts were prepared by incipient-wetness impregnation method. To investigate the effect of Ru and Mn species, the catalytic performances of Mn/TiO2...

Nano-oxides washcoat for enhanced catalytic oxidation activity toward the perovskite-based monolithic catalyst

In order to explore a superior washcoat material to give full play to the catalytic activity of perovskite active components on the monolithic catalysts, three novel types of LaCoO₃/washcoat/cordierite monolith catalysts were prepared by a facile two-step procedure which employed the cordierite honeycomb ceramic as the monolith substrate, the nano-oxides (ZrO₂, ɤ-Al₂O₃, TiO₂) as the washcoat, and the perovskite of LaCoO₃ as the active components. The blank cordierite, powdered LaCoO₃, semi-manufactured monolithic catalysts (washcoat/cordierite), and manufactured monolithic catalysts (LaCoO₃/washcoat/cordierite) were characterized by XRD, SEM, XPS, N₂ adsorption-desorption, H₂-TPR, and ultrasonic test, and their catalytic activities and catalytic stability were evaluated by the toluene oxidation test. The research results indicate that the nanoparticles coated on the cordierite substrate as the washcoat can give full play to the catalytic ability of the LaCoO₃ active components and also showed high catalytic stability. However, the catalytic properties of the monolithic catalysts vary notably with the species of nano-washcoat. Among all the catalysts, the porous honeycomb surface structure, uniform distribution, high ratio of surface adsorbed oxygen, and strong reducing ability together give the LaCoO₃/ZrO₂/cordierite monolithic catalyst the highest catalytic activity on the oxidation of toluene at low temperature, which could be attributed to the excellent interactions of perovskite and nano-ZrO₂ washcoat. Therefore, the nano-oxides, especially the nano-ZrO₂, have a broad practical application potential for toluene oxidation at low temperature as the washcoat of perovskite-based monolithic catalysts.

Catalytic oxidation of toluene, ethyl acetate and chlorobenzene over Ag/MnO2-cordierite molded catalyst

Multi-structured Ag/MnO₂-cordierite molded catalysts were prepared by hydrothermal method and applied to the catalytic oxidation of VOCs. Catalytic activities of Ag/MnO₂-cordierite were evaluated by 1000 ppm of toluene, ethyl acetate and chlorobenzene degradation respectively at the air atmosphere, and their physicochemical properties were characterized through multiple techniques containing XRD, SEM, TEM, H₂-TPR and XPS. It is found that nanorod Ag/MnO₂-cordierite molded catalyst showed prominent catalytic activity for VOCs decomposition and the T₉₀ for toluene, ethyl acetate and chlorobenzene are 275 °C, 217 °C and 385 °C respectively under the space velocity of 10,000 h⁻¹. High valence manganese oxide, more active lattice oxygen proportion and superior low-temperature reducibility were the great contributors to the high activity of the catalyst with nanorod morphology. Studies of space velocity and catalytic stability over nanorod Ag/MnO₂-cordierite molded catalyst have confirmed the good catalytic performance, excellent mechanical strength and satisfied anti-toxicity to Cl at higher space velocity, which indicates that this molded catalyst have promise for industrial application.

Investigation of synergistic effects and high performance of La-Co composite oxides for toluene catalytic oxidation at low temperature

Cobalt oxides have been considered as a kind of highly efficient catalyst for the oxidation of volatile organic compounds (VOCs). In this work, lanthanum-cobalt composite oxides were prepared by using the co-precipitation method, and toluene was used as the model compound. Diversified techniques including XRD, SEM, Raman spectra, XPS, H₂-TPR, and N₂ adsorption-desorption were applied to investigate the physicochemical properties of as-prepared materials. The composite catalysts showed different morphology including larger specific surface area and higher pore volume which would accelerate the adsorption of toluene and improve the amount of active sites on surface. Moreover, the addition of lanthanum could enhance the low-temperature reducibility, and it could be also beneficial to expose more Co³⁺ and adsorbed oxygen species on the surface of catalysts which could accelerate the oxidation of toluene and lower onset oxidation temperature. 0.05La-Co (with a molar ratio of lanthanum against cobalt is 0.05) showed the best catalytic performance. The complete conversion of toluene was achieved at 225 °C under the condition of toluene concentration = 1000 ppm and SV = 20,000 ml·g^-1·h^-1. Stability test over 0.05La-Co was conducted at 225 °C and it could maintain the 100% conversion of toluene for 720 min, indicating the excellent stability of as-prepared catalysts. Undoubtedly, lanthanum-cobalt composite oxide is a kind of promising material for the catalytic oxidation of VOCs.