Ultrasonic effect in the synthesis of catalysts of NiAl oxides prepared starting from the coprecipitation method of a hydrotalcite structure was evaluated in this work. Removal of carbonyl sulfide (COS) at low temperature over the hydrotalcite-derived oxides was studied. The samples were characterized by X-ray Diffraction (XRD), scanning electron microscope (SEM), N2 adsorption/desorption techniques, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and CO2 temperature-programmed desorption (TPD). It is found that hydrotalcite treated with ultrasonic has smaller average crystallite size and higher particle dispersion compared to hydrotalcite without ultrasonic treatment. As a result, mixed oxides derived from hydrotalcite treated with ultrasonic show more developed pore structure which is good for the physical adsorption of gaseous pollutant. The result of desulfuration test showed that removal efficiency of COS on the NiAl mixed oxides prepared by ultrasonic method (30min) is greater than that on the catalyst prepared without the ultrasonic irradiation assistance with the same aging time. One important reason for the high activity is that when the ultrasonic is used the number of weak basic sites (OH(-) groups) and moderate basic sites (M-O) was increased, whereas the number of strong basic sites (O(2-)) was decreased. Therefore, ultrasonic treatment promoted the COS hydrolysis and suppress the poisoning of the catalyst.

The present study is devoted to the investigation of N2O formation characteristics in dielectric barrier discharge (DBD) reactor for environmental application. The effect of operating parameters, such as specific energy density (SED), O2 concentration, NO initial concentration, and residence time on N2O concentration was investigated in dry O2/N2 mixtures. N2O formation from bulk gas (O2 and N2) is inevitable in DBD chemical process and was observed in all DBD reactors. N2O concentration shows an exponential increase or decrease with the variation in operating parameter. The experimental results show that N2O concentration first increases and then reaches saturation with the increase in SED and O2 concentration, respectively. N2O concentration shows a monotonic increase with increasing residence time. N2O concentration decreases with NO concentration increasing from 50 ppm to 600 ppm. The N2O formation is enhanced with γ-Al2O3 pellets packing into the DBD reactor compared with that of DBD reactor alone.

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