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

Abstract

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 = 1000ppm and SV = 20,000ml·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 720min, 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.