Adsorption of 2-Chlorophenol on the Surface of Silica- and Alumina-Supported Iron Oxide: An FTIR and XPS Study

The adsorption of 2-chlorophenol (2-CPh) on the surface of silica, alumina and silica- and alumina-supported iron oxides was examined at 30 and 250 °C. The formation of a chlorophenolate carbanion/chlorophenoxy radical intermediate on the surface of silica and alumina surfaces is identified by using in situ FTIR spectroscopy. The IR spectra of 2-CPh adsorbed on supported iron oxide at 250 °C highlight significant differences in the adsorption complex between 2-CPh and the two supported iron oxides (on silica and alumina). Under conditions of the low coverage of 2-CPh on the surface of these catalysts, FTIR spectroscopy was used to indicate that the adsorption of 2-CPh on the surface of silica-supported iron oxide commences with the formation of a chlorophenolate species, whereas 2-CPh creates a surface formate species on alumina-supported iron oxide. Moreover, the strong bonds of 2-CPh and a high concentration of the carbonate species are evident on the alumina surfaces by using both FTIR and X-ray photoelectron spectroscopy.