N2O5 Formation Mechanism during the Ozone-Based Low-Temperature Oxidation deNOx Process

With advantage of the solubility improving from NO into a higher valence state of nitrogen oxides, especially N2O5, the ozone-based low-temperature oxidation deNO(x) process was investigated, especially the N2O5 formation mechanism. The temperature ranging from 60 to 150 degrees C and O-3/NO ratios and residence time changing were investigated by a well-designed experiment. N2O5 was detected by Fourier transform infrared spectroscopy (FTIR). A 24-step mechanism was also proposed, specially for describing the formation of N2O5. Results demonstrated that the formation of N2O5 was greatly influenced by the temperature and residence time. N2O5 could be formed at relatively low-tempera-hires, such as 60-80 degrees C, within 3-5 s when O-3/NO > 1.0. There was no N2O5 detected when the temperature was higher than 130 degrees C as a result of the decomposition of NO3. The proposed mechanism could give a good prediction of the experimental results with kinetic simulation. To speed up the N2O5 formation process and reduce the O-3 dosage and O-3 slip, a type of MnOx-based catalyst was developed. Results showed that the MnOx-loaded spherical alumina catalyst had obviously a positive effect on the formation of N2O5, with more than 90% NO converted into N2O5 at 80 degrees C,Within 0.24 s and O-3/NO = 1.5, with less than 15 ppm of O-3 leftover.