Hydrothermal Fabrication and Catalytic Properties of La1-xSrxM1-yFeyO3 (M = Mn, Co) That Are Highly Active for the Removal of Toluene

A series of La1-xSrxM1-yFeyO3 (M = Mn, Co; x = 0, 0.4; Y = 0.1, 1.0) perovskite-type oxide catalysts have been fabricated via a strategy of citric acid complexation coupled with hydrothermal treatment. The materials are characterized by a number of analytical techniques. The oxidation of toluene is used as a probe reaction for the evaluation of catalytic performance. It is found that both La0.6Sr0.4FeO3 and LaFeO3 exhibit high activities. The partial substitution of manganese and cobalt with iron can significantly improve the catalytic performance of La0.6Sr0.4MnO3 and La0.6Sr0.4CoO3. At toluene/O-2 molar ratio = 1/200 and space velocity = 20 000 h(-1), the catalytic activity decreases in the sequence of La0.6Sr0.4Fe0.1O3 > La0.6Sr0.4FeO3 > La(0.6)Sr(0.4)Mn(0.9)Fea(0.1)O(3) > LaFeO3 > La0.6Sr0.4CoO3> La0.6Sr0.4MnO3. Compared to the Fe-free counterparts, the La0.6Sr0.4Mn0.9Fe0.1O3 and La0.6Sr0.4Co0.9Fe0.1O3 catalysts are, respectively, 50 and 85 degrees C lower with regard to the temperature required for complete toluene oxidation. Toluene can be completely oxidized at 245 C over La0.6Sr0.4Co0.9Fe0.1O3. The excellent catalytic performance of La0.6Sr0.4Co0.9Fe0.O3 can be attributed to the presence of (i) Fe3+-OFe4+ couples, (ii) a transition of electronic structure, and (iii) a trace amount of Co3O4.