Exploring the Influence of Pd Species Valence State and Chemisorbed Oxygen Concentration on the Catalytic Oxidation Performance of Toluene

The valence state of Pd and chemisorbed oxygen were important factors for catalytic oxidation of toluene. The valence of Pd and chemisorbed oxygen could be adjusted by preparation method. In this paper, a series of Pd/Ce-Zr-Ox (PdCZ-Ox) catalysts were prepared by impregnation (PdCZ-Ox-IM), co-precipitation (PdCZ-Ox-CP), sol–gel (PdCZ-Ox-SG) and hydrothermal (PdCZ-Ox-HT) method, respectively, which could cause the structure alteration of PdCZ-Ox catalysts. These catalysts exhibited a great diverse in catalytic oxidation of toluene reaction due to the structure alteration of PdCZ-Ox catalysts. Through systematic analysis, PdCZ-Ox-CP exhibited higher catalytic performance of toluene oxidation than the other three PdCZ-Ox catalysts, which was attributed to the valence of Pd and the concentration of surface chemisorbed oxygen. The stability of PdCZ-Ox-CP was explored by three consecutives runs, thermal stability and moisture resistance tests. The PdCZ-Ox-CP possessed the good repeatability at three consecutives runs, superior moisture resistance, and the excellent stability.