Kinetics and mechanism study on catalytic oxidation of chlorobenzene over V2O5/TiO2 catalysts

• In-situ FTIR and kinetic methods were combined to study the catalytic mechanism.
• The nucleophilic substitution and surface reaction are kinetically significant steps.
• Chlorination degree of chlorinated benzenes is an important factor in competition reactions.
• Polychlorinated benzenes react easily with the catalyst but significantly affected by internal diffusion limitations.

In this article, we present a detailed study combining the kinetic studies and in-situ FTIR experiments to investigate the oxidation behavior of chlorobenzene over V2O5/TiO2 catalysts. The catalytic data show the 3–5 wt.% V2O5/TiO2 catalysts are best fit for the oxidation of chlorobenzene. The calculated apparent reaction orders are about 0.6 and 0.2, respectively. The results of in-situ FTIR provided mechanism insights into the catalytic reaction, which supports the following proposal: (i) a nucleophilic substitution on VO species and (ii) attacking by surface oxygen through a electrophilic substitution, then (iii) followed by the cracking of ring structure, and further oxidation of the resulting species to form final products. The above results further suggest that the nucleophilic substitution process and surface reaction are kinetically significant steps for chlorobenzene oxidation, determining the overall rate of the reaction. Furthermore, 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,2,4-trichlorobenzene as additional reactants were tested together with chlorobenzene in binary mixtures to examine their competition reactions.

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