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
A reconstruction strategy has been developed to synthesize Cu-SAPO-34 with a wide crystallization phase region,high solid yield,and tunable Si and Cu contents.Cu-rich SAPO-34 was prepared from a Cu-amine complex,which...A reconstruction strategy has been developed to synthesize Cu-SAPO-34 with a wide crystallization phase region,high solid yield,and tunable Si and Cu contents.Cu-rich SAPO-34 was prepared from a Cu-amine complex,which acted as a precursor and Cu source for the reconstruction synthesis.The role of the Cu-amine complex as a template was restricted,which allowed easier control over the Cu and Si contents than in the previously reported"one-pot"synthesis method.Characterization of the material revealed that the Si(4Al)coordination environment dominates the synthesized Cu-SAPO-34 catalysts.High-temperature hydrothermal treatment increased the isolated Cu2+content slightly,and the acid sites in the low-silica catalyst are more resistant to hydrothermal treatment than those of the existing catalysts.The obtained materials,especially the low-silica Cu-SAPO-34 sample,exhibit excellent catalytic activity and hydrothermal stability for the selective catalytic reduction of NOx by NH3(NH3-SCR).In addition,the influence of the catalyst acidity on the NH3-SCR reaction was also investigated and is discussed.The high synthetic efficiency and outstanding catalytic performance make Cu-SAPO-34 synthesized by the reconstruction method a promising catalyst for the NH3-SCR process.展开更多
The high-temperature(HT) and low-temperature(LT) hydrothermal stabilities of molecular-sieve-based catalysts are important for the selective catalytic reduction of NOx with ammonia(NH3-SCR). In this paper, we report a...The high-temperature(HT) and low-temperature(LT) hydrothermal stabilities of molecular-sieve-based catalysts are important for the selective catalytic reduction of NOx with ammonia(NH3-SCR). In this paper, we report a catalyst, Cu2+ loading SAPO-17, synthesized using cyclohexylamine(CHA), which is commercially available and inexpensive and is utilized in NH3-SCR reduction for the first time. After systematic investigations on the optimization of Si and Cu2+ contents, it was concluded that Cu-SAPO-17-8.0%-0.22 displays favorable catalytic performance, even after being heated at 353 K for 24 h and at 973 K for 16 h. Moreover, the locations of CHAs, host–guest interaction and the Bronsted acid sites were explored by Rietveld refinement against powder X-ray diffraction data of as-made SAPO-17-8.0%. The refinement results showed that two CHAs exist within one eri cage and that the protonated CHA forms a hydrogen bond with O4, which indicates that the proton bonding with O4 will form the Bronsted acid site after the calcination.展开更多
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.
文摘A reconstruction strategy has been developed to synthesize Cu-SAPO-34 with a wide crystallization phase region,high solid yield,and tunable Si and Cu contents.Cu-rich SAPO-34 was prepared from a Cu-amine complex,which acted as a precursor and Cu source for the reconstruction synthesis.The role of the Cu-amine complex as a template was restricted,which allowed easier control over the Cu and Si contents than in the previously reported"one-pot"synthesis method.Characterization of the material revealed that the Si(4Al)coordination environment dominates the synthesized Cu-SAPO-34 catalysts.High-temperature hydrothermal treatment increased the isolated Cu2+content slightly,and the acid sites in the low-silica catalyst are more resistant to hydrothermal treatment than those of the existing catalysts.The obtained materials,especially the low-silica Cu-SAPO-34 sample,exhibit excellent catalytic activity and hydrothermal stability for the selective catalytic reduction of NOx by NH3(NH3-SCR).In addition,the influence of the catalyst acidity on the NH3-SCR reaction was also investigated and is discussed.The high synthetic efficiency and outstanding catalytic performance make Cu-SAPO-34 synthesized by the reconstruction method a promising catalyst for the NH3-SCR process.
文摘The high-temperature(HT) and low-temperature(LT) hydrothermal stabilities of molecular-sieve-based catalysts are important for the selective catalytic reduction of NOx with ammonia(NH3-SCR). In this paper, we report a catalyst, Cu2+ loading SAPO-17, synthesized using cyclohexylamine(CHA), which is commercially available and inexpensive and is utilized in NH3-SCR reduction for the first time. After systematic investigations on the optimization of Si and Cu2+ contents, it was concluded that Cu-SAPO-17-8.0%-0.22 displays favorable catalytic performance, even after being heated at 353 K for 24 h and at 973 K for 16 h. Moreover, the locations of CHAs, host–guest interaction and the Bronsted acid sites were explored by Rietveld refinement against powder X-ray diffraction data of as-made SAPO-17-8.0%. The refinement results showed that two CHAs exist within one eri cage and that the protonated CHA forms a hydrogen bond with O4, which indicates that the proton bonding with O4 will form the Bronsted acid site after the calcination.
