A series of CuSO 4 /TiO 2 catalysts were prepared using a wet impregnation method. The activity of each sample in the selective catalytic reduction of NO by NH 3 (NH 3 -SCR) was determined. The effects of SO 2 and H 2 O, and their combined effect, on the activity were examined at 340 °C for 24 h. The catalysts were characterized using N 2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction of H 2 (H 2 -TPR), temperature-programmed desorption of NH 3 (NH 3 -TPD), and in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS). The CuSO 4 /TiO 2 catalysts had good activities, with low production of N 2 O above 340 °C. SO 2 or a combination of SO 2 and H 2 O had little effect on the activity, and H 2 O caused only a slight decrease in activity during the experimental period. The NH 3 -TPD and H 2 -TPR results showed that CuSO 4 increased the amounts of acid sites and adsorbed oxygen on the catalyst. In situ DRIFTS showed that the NH 3 -SCR reaction on the CuSO 4 /TiO 2 catalysts followed an Eley–Rideal mechanism. The reaction of gaseous NO with NH 3 adsorbed on Lewis acid sites to form N 2 and H 2 O could be the main reaction pathway, and oxygen adsorption might favor this process.
Anatase TiO 2 loaded with 0.1wt.% Pt catalyst (0.1Pt/TiO 2 -A) was prepared via the impregnation method, and its CO catalytic oxidation activity was investigated. Noteworthy, introduction of H 2 O into the reaction atmosphere apparently facilitated the catalytic oxidation of CO. Besides, introduction of SO 2 inhibited the catalytic oxidation of CO. In presence of H 2 O and SO 2 , 0.1Pt/TiO 2 -A showed outstanding catalytic stability, and X-ray photoelectron spectroscopy (XPS) and thermogravimetric (TG) characterizations suggested that the amount of sulfate species deposited on the 0.1Pt/TiO 2 -A treated at 230 °C did not increase with time extension, which might be an important reason for the high sulfur resistance of 0.1Pt/TiO 2 -A. XPS results also demonstrated that the dissociation of H 2 O led to considerably increase of hydroxyl groups over the catalyst surface. H 2 18 O isotope-labeling experiments unambiguously showed that C 16 O 18 O was the main product accounting for 88.9%, revealing that the other oxygen atom in the product CO 2 was mostly from H 2 O. Consequently, based on previous researches and our experimental results, the mechanism of H 2 O promoting CO oxidation on 0.1Pt/TiO 2 -A catalyst was proposed.
Experiments were conducted to remove NO from simulated flue gas in a rotating packed bed (RPB) reactor with NaClO2 as wet scrubbing oxidant and diesel exhaust gas as carrier gas. The effects of various operating parameters (rotational speed, solution pH, NaClO2 concentration, liquid-gas ratio, and NO and SO2 concentrations) on NO removal performance were investigated preliminarily. The results showed that with the increase of rotational speed, oxidant concentration, and liquid-gas ratio, NO removal efficiency increased obviously. NO removal efficiency increased largely with the decrease of solution pH, and a complete removal of NO could be attained at pH 4. NO concentration imposed little effect on NO removal efficiency while coexisting SO2 in exhaust gas could enhance NOx removal greatly.
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