Synthesis of W-Nb-O solid acid for catalytic combustion of low-concentration monochlorobenzene

Abstract WO3-Nb2O5 mixed oxides were prepared by citric acid based sol-gel method, and were tested for catalytic combustion of 1000 ppmv monochlorobenzene (MCB), as a typical chlorinated aromatic hydrocarbon in air pollution. Research results for the structure-function relationship revealed that the physicochemical properties of WO3-Nb2O5 were notably promoted than single component metal oxide, due to the strong electron interaction between W, Nb and O elements, which were confirmed by the techniques of H2-TPR, positron lifetime spectra and XPS characterization. WO3-Nb2O5 were amorphous, in which W and Nb elements were homogeneous dispersed. The functionalized materials contributed to the improvement of adsorption, activation, cracking and deep oxidation of MCB on the catalyst surface, and only non-negligible production of CO byproduct was detected. Both the acid property and oxidative property played important roles in the catalytic degradation process, and their cooperative catalytic effect could be optimized by the catalyst composition and preparation process. 2W1Nb (W/Nb = 2:1, molar ratio) displayed the largest acid amount and the best redox property, and thus it displayed the highest catalytic degradation performance, and 50% conversion of MCB was achieved at 280 °C with the GHSV of 9000 mL gcat−1 h−1. Besides, in the 120 h continuous reaction, only slight decrease (from 91% to 86%) for the catalytic activity of 2W1Nb was observed in initial 7 h, showing that it was desired towards the demanding conditions (such as resistance to water adsorption, chlorine poison and carbon deposition). Moreover, the WO3-Nb2O5 materials also satisfied the environment-friendly and low-cost needs for environmental catalysis, which could be a promising alternative for traditional V2O5-WO3/TiO2 catalyst system.