Effects of SO₂ on selective catalytic reduction of NO with NH₃ over a TiO₂ photocatalyst

Abstract

The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

Selective Catalytic Reduction of NO by NH3 over Photocatalysts (Photo‐SCR): Mechanistic Investigations and Developments

“…Recently, we investigated the effect of SO 2 gas on the activity in the photo‐SCR over a TiO 2 photocatalyst by introducing SO 2 (200 ppm) into the reaction gas. Unfortunately, the activity decreased rapidly with the reaction time in the presence of SO 2 gas when the reaction was carried out at 373 K (Figure ) 31. On the other hand, increase of the reaction temperature increased the lifetime of the catalysts, and the activity was completely stable at the reaction temperature of 553 K.…”

“…(♦) SO 2 : 0 ppm, 433 K. (▲) SO 2 : 300 ppm, 373 K. (▪) SO 2 : 300 ppm, 433 K. (•) SO 2 : 300 ppm, 553 K. NO: 1000 ppm, NH 3 : 1000 ppm, O 2 : 2%, GHSV: 100,000 h −1 . The figure was taken from reference 31.…”

Kinetic modeling for the deactivation of TiO2 during the photocatalytic removal of low concentration SO2

“…(15), (16), (18), and (19), the deactivation kinetic model of the SO 2 removal process by TiO 2 was obtained. The dimensionless parameters were introduced into the partial differential equations (PDE) to modify the kinetic model.…”

“…Different analysis techniques, such as FTIR and X-ray photoelectric spectroscopy, were employed to elucidate the mechanism of the deactivation process. The deactivation was mainly due to poisoning by the oxidation products of SO 2 which could attach to the TiO 2 surface and block the active sites on the surface [14][15][16].…”

Surface Ba species effective for photoassisted NO storage over Ba-modified TiO2 photocatalysts

“…Diffraction peaks of cubic Ba(NO 3 ) 2 appeared in the as-synthesized Ba/TiO 2 catalysts over 250 µmol g −1 of Ba loading, which indicates that the Ba species are loaded on TiO 2 as a nitrate form after the impregnation.Table 1represents the crystalline size of TiO 2 and S BET of the catalysts with various Ba loading. In the as-synthesized catalysts, S BET decreased with increasing the Ba loading although the crystalline size of TiO 2 did not change after the Ba loading.The decrease of the surface area is possibly due to a plugging of pores derived from gaps of TiO 2 particles [40]. Without Ba loading (bare TiO 2 ), the pretreatment at 773 K and the following reaction drastically decreased S BET from 292 to 185 m 2 g −1 and increased the crystalline sizes of TiO 2 from 7.7 to 10.9 nm, which was due to sintering of TiO 2 particles after the pretreatment at 773 K. The crystalline sizes of TiO 2 (8.5−9.3 nm) in Ba/TiO 2 after the reaction were smaller than that of TiO 2 after the reaction (10.9 nm).…”