The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature.

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Trichloroethylene (TCE) decomposition over a MnOx/ gamma-Al2O3 catalyst in a fixed-bed reactor was conducted in this study. The MnOx/gamma-Al2O3 powders were prepared by the incipient wetness impregnation method with aqueous solution of manganese nitrate. The catalysts were characterized by DTA-TGA, XRD, porosity analysis, SEM, EDX, and XPS. The results show that the main distinct weight loss is found at the temperature around 373 and 873 K,the MnO peaks (2theta = 34.9 degrees and 40.5 degrees) are only observed crystal phase on the fresh catalyst, the SEM image of the MnOx-impregnated gamma-Al2O3 support is much different from the calcined catalyst, and the Mn element quantity on the catalyst surface is higher than that of the impregnated support. The products and reactants distributions from the oxidation of TCE over MnOx/gamma-Al2O3 were analyzed by GC. The results show that the TCE conversion starts from 5% at 443 K and rises to very high values in the 673-873 K ranges and that the CO2 yield also pushes to 99% at the same temperature ranges. HCl and Cl2 are the other main products with little halogenated VOC intermediates.

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