E. Luévano-Hipólito

Enhancement of photocatalytic properties of TiO2 for NO photo-oxidation by optimized sol–gel synthesis

TiO2 samples were prepared by the sol–gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide for the nitric oxide (NO) photo-oxidation reaction. The temperature of calcination and the amount of alcohol and acid used in the course of the sol–gel reaction were selected as critical experimental variables. As the products of the factorial design, 27 TiO2 samples were obtained and characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and adsorption–desorption N2 isotherms. The photocatalytic activity of the TiO2 samples was evaluated in the NO photo-oxidation reaction under UV irradiation. The conversion degree of NO reached by each sample was associated with its physicochemical properties, finding a stronger dependence with the temperature of calcination and morphology of the samples. Different photocatalytic reaction parameters were modified such as mass of photocatalyst, irradiance, flow rate of gas, and relative humidity in order to evaluate their effect in the constants of velocity and adsorption. The TiO2 sample with the highest photocatalytic activity was exposed under different experimental conditions to evaluate its selectivity for the formation of innocuous nitrate ions as final product of the NO photo-oxidation reaction.

Performance of ZnO synthesized by sol-gel as photocatalyst in the photooxidation reaction of NO

ZnO samples were prepared by sol-gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide in the NO photooxidation reaction. The concentrations of zinc acetate and ammonium hydroxide were selected as critical variables in the synthesis of ZnO. Nine samples of ZnO were obtained as product of the factorial design and were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and N2 adsorption-desorption isotherms. The photocatalytic activity of ZnO samples was associated with the physical properties developed by each sample according to its respective conditions of synthesis. Some photocatalytic reaction parameters, such as mass of photocatalyst, irradiance, and relative humidity, were modified in order to evaluate its effect in the photocatalytic conversion of NO. As a relevant point, the relative humidity played an important role in the increase of the selectivity of the NO photooxidation reaction to innocuous nitrate ions when ZnO was used as photocatalyst.

Modeling Synthesis Processes of Photocatalysts Using Symbolic Regression a#x03B1;-a#x03B2;

Symbolic regression is an application of genetic programming and is used for modeling different dynamic processes. Industrial processes problems have been solved using this technique. In this work a symbolic regression algorithm is used for modeling the synthesis process of the oxides Bi2MoO6 and V2O5 in order to provide a model. These oxides are used on heterogeneous photo catalysis. Genetic programming, artificial neural network and linear regression are compared with symbolic regression models using statistics metrics to evaluate them.