Abstract
Ca/ZrCu/ZSM-5 catalysts containing different Zr contents were prepared by incipient wetness impregnation. The catalysts were tested for the selective catalytic reduction (SCR) of NOx with ammonia and characterized by N2-BET, N2O titration, XRD, NH3-TPD, H2-TPR, and XPS techniques. In the temperature range of 100–170 °C, after calcium impregnation, NOx conversion over the Cu/ZSM-5 catalyst decreased by 11.3–24.3%, while that over Zr0.10/Cu/ZSM-5 only decreased by 3.8–12.2%. The improvement of the calcium poisoning resistance of the ZrCu/ZSM-5 catalyst is mainly attributed to an increase in the dispersion and the surface concentration of Cu. Moreover, the addition of zirconium promotes the reduction of CuO by decreasing the interaction between CuO and CaO, which also contributes to the improvement of resistance to CaO poisoning. The apparent activation energy and turnover frequency for the SCR reaction over the Ca/ZrxCu/ZSM-5 catalysts were calculated and discussed.
Highlights
As major air pollutants, nitrogen oxides (NOx) result in a series of environmental issues, such as photochemical smog, acid rain, and ozone depletion.[1,2,3] Recently, researchers found that NOx is one of the key factors for the formation and evolution of haze, which is harmful to the ecological environment and human health.[4]
The turnover frequency (TOF) of the NH3-selective catalytic reduction (SCR) reaction, de ned as the number of NOx molecules converted per metallic copper atom per second, can be calculated by the equation: TOF 1⁄4
Where, XNOx is the conversion of NOx (eqn (2)), FNOx is the volumetric ow rate of NOx, mcatal is the mass of catalyst, NA is the A Fugadero constant, and SCu is the copper surface area determined by N2O titration (eqn (1))
Summary
Nitrogen oxides (NOx) result in a series of environmental issues, such as photochemical smog, acid rain, and ozone depletion.[1,2,3] Recently, researchers found that NOx is one of the key factors for the formation and evolution of haze, which is harmful to the ecological environment and human health.[4]. Paper calcium resistance of the Cu/zeolite catalysts for the selective catalytic reduction of NOx are quite few. Ca/ZrCu/ZSM-5 catalysts containing different Zr content were prepared and tested for the SCR of NOx. This study focuses on the promoting effects of ZrO2 on the resistance to Ca poisoning over the Cu/ZSM-5 catalyst. The physicochemical properties of the catalysts were investigated, and the relationship between the physicochemical properties and the activity of catalysts was discussed
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