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

Abstract

Three perovskite-type catalysts including LaMnO₃, La_0.8Ce_0.2MnO₃, and La_0.8Ce_0.2 Mn_0.8Ni_0.2O₃ are prepared using citric acid sol-gel method and evaluated as catalyst for the oxidation of trichloroethylene (TCE) in air with temperature ranging from 100 to 600 °C. The physicochemical properties of three perovskite-type catalysts were characterized by SEM, EDS, XRD, BET, and XPS to investigate the relationship with catalytic activities. The results show that the removal efficiency of TCE achieved with La_0.8Ce_0.2Mn_0.8Ni_0.2O₃ (the best one) reaches 100% at 400 °C and the mineralization efficiency reaches 100% at 600 °C. The enhanced activity can be attributed to the addition of Ce and Ni which increases the surface areas, active oxygen species, and the redox ability of the Mn⁴⁺/Mn³⁺ ratio on the catalyst surface. As La_0.8Ce_0.2Mn_0.8Ni_0.2O₃ is applied for TCE oxidation, the main intermediate chlorinated byproduct detected is tetrachloroethylene (C₂Cl₄) which is generated by the reaction of TCE and chlorine (Cl₂). The activation energy for the TCE oxidation with La_0.8Ce_0.2Mn_0.8Ni_0.2O₃ catalyst is 51 kJ/mol using kinetic models of power–law type.