A series of TiO_(2)-Al_(2)O_(3) composites with Al/Ti molar ratios of 0.1,0.2,and 0.4 were synthesized by a coprecipitation method and used as supports to prepare supported MnCeO_(x) catalysts by an impregnation metho...A series of TiO_(2)-Al_(2)O_(3) composites with Al/Ti molar ratios of 0.1,0.2,and 0.4 were synthesized by a coprecipitation method and used as supports to prepare supported MnCeO_(x) catalysts by an impregnation method.The physico-chemical properties of the samples were extensively characterized by N_(2) physisorption,X-ray diffraction,Raman spectroscopy,scanning electron micro scopy and energy-dispersive Xray spectroscopy element mapping,X-ray photoelectron spectroscopy,H_(2)-temperature programmed reduction,ammonia temperature programmed desorption,and in-situ diffuse reflectance infrared Fourier transform spectroscopy.The catalytic activity and resistance to water vapor and SO_(2) of the asprepared catalysts for the SCR of NO_(x) with NH_(3) were evaluated at 50-250℃ and GHSV of 80000 mL/(gcat·h).The results reveal that MnCeO_(x)/TiO_(2)-Al_(2)O_(3) exhibits higher activity and better SO_(2) tolerance than MnCeO_(x)/TiO_(2).Combining with the characterization results,the enhanced activity and SO_(2) tolerance of MnCeO_(x)/TiO_(2)-Al_(2)O_(3) can be mainly attributed to higher relative concentrations of Mn4+and chemisorbed oxygen species,stronger reducibility,and larger adsorption capacity for NH_(3) and NO,which originate from the larger specific surface area and pore volume,higher dispersion of Mn and Ce species compared with MnCeO_(x)/TiO_(2).Moreover,in situ DRIFTS was used to investigate the reaction mechanism,and the results indicate that the NH_(3)-SCR reaction over MnCeO_(x)/TiO_(2) and MnCeO_(x)/TiO_(2)-Al_(2)O_(3) takes place by both the E-R and L-H mechanisms.展开更多
Developing low-temperature SO_(2)-tolerant catalysts for the selective catalytic reduction of NO_(x) is still a challenging task.The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate cat...Developing low-temperature SO_(2)-tolerant catalysts for the selective catalytic reduction of NO_(x) is still a challenging task.The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate catalysts,due to the difficult decomposition of the as-formed sulfate species at low temperatures(<300℃).In recent years,metal sulfate catalysts have attracted increasing attention owing to their good catalytic activity and strong SO_(2) tolerance at higher temperatures(>300℃);however,the SO_(2)-tolerant mechanism of metal sulfate catalysts is still ambiguous.In this study,Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2) catalysts were prepared using the corresponding metal sulfate salt as the precursor.These catalysts were tested for their low-temperature activity and SO_(2) tolerance activity.Compared to Ce_(2)(SO_(4))_(3)/TiO_(2),Fe_(2)(SO_(4))_(3)/TiO_(2) showed significantly better low-temperature activity and SO_(2) tolerance.It was demonstrated that less surface sulfate species formed on Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2).However,the presence of NO and O_(2) could assist the decomposition of NH_(4)HSO_(4) over Fe_(2)(SO_(4))_(3)/TiO_(2) at a lower temperature,endowing Fe_(2)(SO_(4))_(3)/TiO_(2) with better low-temperature SO_(2) tolerance than Ce_(2)(SO_(4))_(3)/TiO_(2).This study unraveled the SO_(2)-tolerant mechanism of Fe_(2)(SO_(4))_(3)/TiO_(2)at lower temperatures(<300℃),and a potential strategy is proposed for improving the low-temperature SO_(2)-tolerance of catalysts with Fe_(2)(SO_(4))_(3) as the main active component or functional promoter.展开更多
基金Project supported by the Alliance Project of Shanghai City in China(LM201641)。
文摘A series of TiO_(2)-Al_(2)O_(3) composites with Al/Ti molar ratios of 0.1,0.2,and 0.4 were synthesized by a coprecipitation method and used as supports to prepare supported MnCeO_(x) catalysts by an impregnation method.The physico-chemical properties of the samples were extensively characterized by N_(2) physisorption,X-ray diffraction,Raman spectroscopy,scanning electron micro scopy and energy-dispersive Xray spectroscopy element mapping,X-ray photoelectron spectroscopy,H_(2)-temperature programmed reduction,ammonia temperature programmed desorption,and in-situ diffuse reflectance infrared Fourier transform spectroscopy.The catalytic activity and resistance to water vapor and SO_(2) of the asprepared catalysts for the SCR of NO_(x) with NH_(3) were evaluated at 50-250℃ and GHSV of 80000 mL/(gcat·h).The results reveal that MnCeO_(x)/TiO_(2)-Al_(2)O_(3) exhibits higher activity and better SO_(2) tolerance than MnCeO_(x)/TiO_(2).Combining with the characterization results,the enhanced activity and SO_(2) tolerance of MnCeO_(x)/TiO_(2)-Al_(2)O_(3) can be mainly attributed to higher relative concentrations of Mn4+and chemisorbed oxygen species,stronger reducibility,and larger adsorption capacity for NH_(3) and NO,which originate from the larger specific surface area and pore volume,higher dispersion of Mn and Ce species compared with MnCeO_(x)/TiO_(2).Moreover,in situ DRIFTS was used to investigate the reaction mechanism,and the results indicate that the NH_(3)-SCR reaction over MnCeO_(x)/TiO_(2) and MnCeO_(x)/TiO_(2)-Al_(2)O_(3) takes place by both the E-R and L-H mechanisms.
基金the support of the National Natural Science Foundation of China(No.21976117,21906102)the Shanghai Sailing Program of the Science and Technology Commission of Shanghai Municipality(No.19YF1415300)311 talents Supporting Project(No.RCPY202010)。
文摘Developing low-temperature SO_(2)-tolerant catalysts for the selective catalytic reduction of NO_(x) is still a challenging task.The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate catalysts,due to the difficult decomposition of the as-formed sulfate species at low temperatures(<300℃).In recent years,metal sulfate catalysts have attracted increasing attention owing to their good catalytic activity and strong SO_(2) tolerance at higher temperatures(>300℃);however,the SO_(2)-tolerant mechanism of metal sulfate catalysts is still ambiguous.In this study,Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2) catalysts were prepared using the corresponding metal sulfate salt as the precursor.These catalysts were tested for their low-temperature activity and SO_(2) tolerance activity.Compared to Ce_(2)(SO_(4))_(3)/TiO_(2),Fe_(2)(SO_(4))_(3)/TiO_(2) showed significantly better low-temperature activity and SO_(2) tolerance.It was demonstrated that less surface sulfate species formed on Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2).However,the presence of NO and O_(2) could assist the decomposition of NH_(4)HSO_(4) over Fe_(2)(SO_(4))_(3)/TiO_(2) at a lower temperature,endowing Fe_(2)(SO_(4))_(3)/TiO_(2) with better low-temperature SO_(2) tolerance than Ce_(2)(SO_(4))_(3)/TiO_(2).This study unraveled the SO_(2)-tolerant mechanism of Fe_(2)(SO_(4))_(3)/TiO_(2)at lower temperatures(<300℃),and a potential strategy is proposed for improving the low-temperature SO_(2)-tolerance of catalysts with Fe_(2)(SO_(4))_(3) as the main active component or functional promoter.
