FT-IR Spectroscopic Study of the Oxidation of Chlorobenzene over Mn-Based Catalyst

Adsorption and oxidation of chlorobenzene on Al2O3, TiO2-Al2O3, and MnOx/TiO2-Al2O3 have been studied by in situ Fourier transform infrared (FT-IR) spectroscopy. At room temperature, chlorobenzene is only physisorbed on Al2O3, TiO2-Al2O3, and MnOx/TiO2-Al2O3, and gives the same IR spectrum as that for liquid-phase chlorobenzene. On Al2O3 no further interaction and reaction take place with treatment at higher temperatures (up to 773 K), while phenolates are observed for TiO2-Al2O3 and MnOx/TiO2-Al2O3 at 773 K. When the adsorbed chlorobenzene coexists with oxygen, formates are detected for Al2O3, while acetates are additionally observed for TiO2-Al2O3 above 573 K. For MnOx/TiO2-Al2O3, maleates are present at 573 and 673 K, while formates and acetates develop at 473 and 573 K. Almost all IR bands due to formates, acetates, and maleates disappear at 773 K, indicating that these oxygen-containing species are potential intermediates for the total oxidation of chlorobenzene.