Influence of Ce/Nb Molar Ratios on Oxygen-Rich CexNb1-xO4+δ Materials for Catalytic Combustion of VOCs in the Process of Polyether Polyol Synthesis

Catalytic combustion is an efficient and economical technique to deal with the air pollution of diluted volatile organic compounds (VOCs). In this work, oxygen-rich CeO 2 -Nb 2 O 5 mixed oxides (Ce x Nb 1-x O 4+δ ) with varied Ce/Nb molar ratios in the bulk synthesized by modified sol–gel method were investigated for complete catalytic combustion of VOCs as exemplified by monochlorobenzene and toluene. To reveal the structure–function relationship of these materials, comprehensive catalytic performance evaluation and characterizations were performed, which showed that the 4Ce1Nb catalyst (CeO 2 -Nb 2 O 5 with Ce/Nb molar ratio of 4:1) displayed superb apparent catalytic activity. Complete oxidation could be accomplished below 300 °C, which was significantly lower than that of single-component CeO 2 or Nb 2 O 5 , as well as some other types of V and Cr based mixed oxide catalysts. Moreover, the apparent catalytic activity of 4Ce1Nb could be maintained for at least 100 h at 280 °C with high selectivity to the formation of HCl and CO 2 . The improved catalytic performance of 4Ce1Nb could be ascribed to the formation of oxygen-rich Ce x Nb 1-x O 4+δ mixed oxides with high dispersion of Ce and Nb species into each other, the strong interaction of Ce–O-Nb, an abundance of active oxygen species, high specific surface area and mesoporous structure. Graphic Abstract