This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both...This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) of NO<sub>x</sub> conditions. The XRD, TG and N<sub>2</sub>-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO<sub>2</sub> and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO<sub>2</sub> or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO<sub>2</sub> or propene compared to Cu-SAPO-34 catalyst. The H<sub>2</sub>-TPR results showed that Cu<sup>2 </sup> ions could be reduced to Cu<sup> </sup> and Cu<sup>0</sup> for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.展开更多
In this paper, A2ZnH4(A = K, Rb and Cs) have been synthesized for the first time by a new approach involving in two-step reactions, in which the target samples can be produced under mild conditions(160 ℃ for 4 h). W...In this paper, A2ZnH4(A = K, Rb and Cs) have been synthesized for the first time by a new approach involving in two-step reactions, in which the target samples can be produced under mild conditions(160 ℃ for 4 h). What’s more, the additive effects of A2ZnH4 on the hydrogen storage properties of 2LiH-Mg(NH2)2 composite have been investigated systematically. Experimental results show that K2ZnH4 has the best comprehensive modification effects among these hydrides. The 2LiH-Mg(NH2)2-0.1 K2ZnH4 sample shifts dehydrogenation peak temperature downwards by ca. 30 ℃ as compared to the pristine sample. In addition, about 70% extent of the theoretical hydrogen is able to desorb from the 0.1 K2ZnH4 doped sample at 140 ℃ within 2 h, however, only 20% extent of hydrogen is liberated from the pure sample under the same conditions. The improved desorption kinetics is indicated by the reduced dehydrogenation activation energy(Ea), the Ea of the 0.1 K2ZnH4 doped sample is around 68 ± 1.0 kJ mol-1 which is 28% lower than that of the pristine one. Furthermore, the dehydrogenation mechanism of the K2ZnH4 doped sample has been proposed.展开更多
V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for N...V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.展开更多
文摘This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) of NO<sub>x</sub> conditions. The XRD, TG and N<sub>2</sub>-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO<sub>2</sub> and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO<sub>2</sub> or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO<sub>2</sub> or propene compared to Cu-SAPO-34 catalyst. The H<sub>2</sub>-TPR results showed that Cu<sup>2 </sup> ions could be reduced to Cu<sup> </sup> and Cu<sup>0</sup> for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.
基金the supports provided by National Key R&D Program of China(2018YFB1502101)the National Natural Science Foundation of China(51801197)+3 种基金DICP(DICP I201942)Youth Innovation Promotion Association CAS(2019189)Project supported by the Science Foundation of China Academy of Engineering Physics,China(Grant No.JZX7Y201901SY00900106)K.C.Wong Education Foundation。
文摘In this paper, A2ZnH4(A = K, Rb and Cs) have been synthesized for the first time by a new approach involving in two-step reactions, in which the target samples can be produced under mild conditions(160 ℃ for 4 h). What’s more, the additive effects of A2ZnH4 on the hydrogen storage properties of 2LiH-Mg(NH2)2 composite have been investigated systematically. Experimental results show that K2ZnH4 has the best comprehensive modification effects among these hydrides. The 2LiH-Mg(NH2)2-0.1 K2ZnH4 sample shifts dehydrogenation peak temperature downwards by ca. 30 ℃ as compared to the pristine sample. In addition, about 70% extent of the theoretical hydrogen is able to desorb from the 0.1 K2ZnH4 doped sample at 140 ℃ within 2 h, however, only 20% extent of hydrogen is liberated from the pure sample under the same conditions. The improved desorption kinetics is indicated by the reduced dehydrogenation activation energy(Ea), the Ea of the 0.1 K2ZnH4 doped sample is around 68 ± 1.0 kJ mol-1 which is 28% lower than that of the pristine one. Furthermore, the dehydrogenation mechanism of the K2ZnH4 doped sample has been proposed.
基金supported by the National Natural Science Foundation of China (51372137)the National High Technology Research and Development Program of China (863 Program,2015AA034603)~~
文摘V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.
