The effects of SO_(2) on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO_(x) by NH_(3) were examined.The addition of SO_(2) inhibited NO_(x) conversion significantly below 300℃,while no effect...The effects of SO_(2) on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO_(x) by NH_(3) were examined.The addition of SO_(2) inhibited NO_(x) conversion significantly below 300℃,while no effect on NO_(x) conversion was observed above 300℃.TGA,TPD,and XPS results showed that the deactivation was caused by the formation of(NH4)2SO_(4),SO_(2) chemisorption on the isolated Cu^(2+)ion sites,as well as the formation of CuSO_(4)-like species.Among them,the site-blocking effect of(NH_(4))_(2)SO_(4) on Cu^(2+)was the primary reason for deactivation.Fortunately,89%of deNO_(x) activity of the poisoned catalyst was recovered after thermal treatment at 500℃ in air,where(NH_(4))_(2)SO_(4) was completely decomposed.The activity was further recovered with regeneration temperature increasing to 600℃,removing the adsorbed SO_(2) on the Cu^(2+)sites.The regeneration at 600℃ could not recover the activity completely,because of the high stability of CuSO_(4)-like species.展开更多
Cerium‐based catalysts are very attractive for the catalytic abatement of nitrogen oxides(NOx)emitted from stationary sources.However,the main challenge is still achieving satisfactory catalytic activity in the low‐...Cerium‐based catalysts are very attractive for the catalytic abatement of nitrogen oxides(NOx)emitted from stationary sources.However,the main challenge is still achieving satisfactory catalytic activity in the low‐temperature range and tolerance to SO2 poisoning.In the present work,two series of Mo‐modified CeO_(2)catalysts were respectively obtained through a wet impregnation method(Mo‐CeO_(2))and a co‐precipitation method(MoCe‐cp),and the roles of the Mo species were systematically investigated.Activity tests showed that the Mo‐CeO_(2)catalyst displayed much higher NO conversion at low temperature and anti‐SO2 ability than MoCe‐cp.The optimal Mo‐CeO_(2)catalyst displayed over 80%NO elimination efficiency even at 150°C and remarkable SO2 resistance at 250°C(nearly no activity loss after 40 h test).The characterization results indicated that the introduced Mo species were highly dispersed on the Mo‐CeO_(2)catalyst surface,thereby providing more Brønsted acid sites and inhibiting the formation of stable adsorbed NOx species.These factors synergistically promote the selective catalytic reduction(SCR)reaction in accordance with the Eley‐Rideal(E‐R)reaction path on the Mo‐CeO_(2)catalyst.Additionally,the molybdenum surface could protect CeO_(2)from SO2 poisoning;thus,the reducibility of the Mo‐CeO_(2)catalyst declined slightly to an adequate level after sulfation.The results in this work indicate that surface modification with Mo species may be a simple method of developing highly efficient cerium‐based SCR catalysts with superior SO2 durability.展开更多
The 2024 anodized aluminum alloy film was sealed by KAl(SO_(4))_(2)solution and the effect of sealing on corrosion resistance was investigated by means of potentiodynamic polarization curves,electrochemical impedance ...The 2024 anodized aluminum alloy film was sealed by KAl(SO_(4))_(2)solution and the effect of sealing on corrosion resistance was investigated by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy,and X-ray photoelectron spectroscopy.The experimental results show that the optimal parameters for KAl(SO_(4))_(2)sealing are 35℃,with the pH value of 8,the concentration of 8 g/L,and the sealing time of 3 min.The corrosion resistance of the KAl(SO_(4))_(2)sealed sample can be significantly improved than that of unsealed one,and is obviously superior to that of the conventional hydrothermal sealed sample.Furthermore,X-ray photoelectron spectroscopy demonstrates that more Al(OH)_(3)will be formed in the process of KAl(SO_(4))_(2)sealing,which will shrink the diameter of the microporous and therefore results in the excellent corrosion resistance.展开更多
Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in...Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in nonelectrical industries.In this study,NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) is greatly improved via Ce(SO_(4))_(2) modification.It has been originally demonstrated that Ce^(4+)-SO_(4)^(2−)pair sites play crucial roles in improving NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) catalysts.The strong interaction between V species and Ce sites of Ce^(4+)-SO_(4)^(2−)pairs triggers the reaction between NH_(4)^(+) species and gaseous NO via Eley-Rideal(E-R)reaction pathway.After K-poisoning,the SO_(4)^(2−)sites of Ce^(4+)-SO_(4)^(2−)pairs as protective sites strongly bond with K and thus maintain the high reaction efficiency via the E-R reaction pathway.This work demonstrates an effective strategy to enhance NO_(x) reduction against alkali poisoning over catalysts via constructing Ce^(4+)-SO_(4)^(2−)pair sites,contributing to developing alkali-resistant SCR catalysts for practical application in nonelectrical industries.展开更多
CuCe/CNT_(x)-SAPO-34(x=0,0.5,1,2) with various CNT doping quantities were synthesized through the one-pot hydrothermal synthesis method using CNT and SAPO-34 as composite supporters.The selected CuCe/CNT_1-SAPO-34 cat...CuCe/CNT_(x)-SAPO-34(x=0,0.5,1,2) with various CNT doping quantities were synthesized through the one-pot hydrothermal synthesis method using CNT and SAPO-34 as composite supporters.The selected CuCe/CNT_1-SAPO-34 catalyst exhibits remarkable SCR activity and high H_(2)O/SO_(2) resistance in a wide temperature range of 200-450℃.X-ray diffraction(XRD),N_(2) adsorption-desorption,scanning electron microscopy(SEM),X-ray photoelectro n spectroscopy(XPS),H_(2)-temperature programmed reduction(H2-TPR),and NH3-temperature programmed desorption(NH_(3)-TPD) were used to characterize the physiochemical structure,surface state of active sites reducibility,and surface acidity of the catalysts.The characterization results reveal that CuCe/CNT_1-SAPO-34 possesses a hierarchical structure,small particle size,high levels of surface Cu^(2+),Ce^(3+) and chemisorbed oxygen,enhanced reducibility,and suitable surface acidity.For comparison,CuCe/CNT_1-SAPO-34(P) mixed mechanically with CuCe/CNT_0-SAPO-34and CNT was investigated through the NH3-SCR with and without H_(2)O/SO_(2),it also displays lower resistance of H_(2)O and SO_(2) than CuCe/CNT_1-SAPO-34.The catalytic performance made CuCe/CNT_1-SAPO-34 a promising catalyst for the NO_(x) emission control from diesel vehicles.展开更多
基金Financial supports from the Natural Science Foundation of Tianjin 19JCTPJC42300.
文摘The effects of SO_(2) on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO_(x) by NH_(3) were examined.The addition of SO_(2) inhibited NO_(x) conversion significantly below 300℃,while no effect on NO_(x) conversion was observed above 300℃.TGA,TPD,and XPS results showed that the deactivation was caused by the formation of(NH4)2SO_(4),SO_(2) chemisorption on the isolated Cu^(2+)ion sites,as well as the formation of CuSO_(4)-like species.Among them,the site-blocking effect of(NH_(4))_(2)SO_(4) on Cu^(2+)was the primary reason for deactivation.Fortunately,89%of deNO_(x) activity of the poisoned catalyst was recovered after thermal treatment at 500℃ in air,where(NH_(4))_(2)SO_(4) was completely decomposed.The activity was further recovered with regeneration temperature increasing to 600℃,removing the adsorbed SO_(2) on the Cu^(2+)sites.The regeneration at 600℃ could not recover the activity completely,because of the high stability of CuSO_(4)-like species.
文摘Cerium‐based catalysts are very attractive for the catalytic abatement of nitrogen oxides(NOx)emitted from stationary sources.However,the main challenge is still achieving satisfactory catalytic activity in the low‐temperature range and tolerance to SO2 poisoning.In the present work,two series of Mo‐modified CeO_(2)catalysts were respectively obtained through a wet impregnation method(Mo‐CeO_(2))and a co‐precipitation method(MoCe‐cp),and the roles of the Mo species were systematically investigated.Activity tests showed that the Mo‐CeO_(2)catalyst displayed much higher NO conversion at low temperature and anti‐SO2 ability than MoCe‐cp.The optimal Mo‐CeO_(2)catalyst displayed over 80%NO elimination efficiency even at 150°C and remarkable SO2 resistance at 250°C(nearly no activity loss after 40 h test).The characterization results indicated that the introduced Mo species were highly dispersed on the Mo‐CeO_(2)catalyst surface,thereby providing more Brønsted acid sites and inhibiting the formation of stable adsorbed NOx species.These factors synergistically promote the selective catalytic reduction(SCR)reaction in accordance with the Eley‐Rideal(E‐R)reaction path on the Mo‐CeO_(2)catalyst.Additionally,the molybdenum surface could protect CeO_(2)from SO2 poisoning;thus,the reducibility of the Mo‐CeO_(2)catalyst declined slightly to an adequate level after sulfation.The results in this work indicate that surface modification with Mo species may be a simple method of developing highly efficient cerium‐based SCR catalysts with superior SO2 durability.
基金Funded by the National Natural Science Foundation of China(No.12175107)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(No.NY220030)
文摘The 2024 anodized aluminum alloy film was sealed by KAl(SO_(4))_(2)solution and the effect of sealing on corrosion resistance was investigated by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy,and X-ray photoelectron spectroscopy.The experimental results show that the optimal parameters for KAl(SO_(4))_(2)sealing are 35℃,with the pH value of 8,the concentration of 8 g/L,and the sealing time of 3 min.The corrosion resistance of the KAl(SO_(4))_(2)sealed sample can be significantly improved than that of unsealed one,and is obviously superior to that of the conventional hydrothermal sealed sample.Furthermore,X-ray photoelectron spectroscopy demonstrates that more Al(OH)_(3)will be formed in the process of KAl(SO_(4))_(2)sealing,which will shrink the diameter of the microporous and therefore results in the excellent corrosion resistance.
基金the National Natural Science Foundation of China(Nos.22125604,22106100,21976117)Shanghai Rising-Star Program(No.22QA1403700)+1 种基金Chenguang Program supported by Shanghai Education Development FoundationShanghai Municipal Education Commission(No.22Z00354).
文摘Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in nonelectrical industries.In this study,NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) is greatly improved via Ce(SO_(4))_(2) modification.It has been originally demonstrated that Ce^(4+)-SO_(4)^(2−)pair sites play crucial roles in improving NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) catalysts.The strong interaction between V species and Ce sites of Ce^(4+)-SO_(4)^(2−)pairs triggers the reaction between NH_(4)^(+) species and gaseous NO via Eley-Rideal(E-R)reaction pathway.After K-poisoning,the SO_(4)^(2−)sites of Ce^(4+)-SO_(4)^(2−)pairs as protective sites strongly bond with K and thus maintain the high reaction efficiency via the E-R reaction pathway.This work demonstrates an effective strategy to enhance NO_(x) reduction against alkali poisoning over catalysts via constructing Ce^(4+)-SO_(4)^(2−)pair sites,contributing to developing alkali-resistant SCR catalysts for practical application in nonelectrical industries.
基金supported by the Basic Science Research Project of Heilongjiang Provincial University,China (145109109)。
文摘CuCe/CNT_(x)-SAPO-34(x=0,0.5,1,2) with various CNT doping quantities were synthesized through the one-pot hydrothermal synthesis method using CNT and SAPO-34 as composite supporters.The selected CuCe/CNT_1-SAPO-34 catalyst exhibits remarkable SCR activity and high H_(2)O/SO_(2) resistance in a wide temperature range of 200-450℃.X-ray diffraction(XRD),N_(2) adsorption-desorption,scanning electron microscopy(SEM),X-ray photoelectro n spectroscopy(XPS),H_(2)-temperature programmed reduction(H2-TPR),and NH3-temperature programmed desorption(NH_(3)-TPD) were used to characterize the physiochemical structure,surface state of active sites reducibility,and surface acidity of the catalysts.The characterization results reveal that CuCe/CNT_1-SAPO-34 possesses a hierarchical structure,small particle size,high levels of surface Cu^(2+),Ce^(3+) and chemisorbed oxygen,enhanced reducibility,and suitable surface acidity.For comparison,CuCe/CNT_1-SAPO-34(P) mixed mechanically with CuCe/CNT_0-SAPO-34and CNT was investigated through the NH3-SCR with and without H_(2)O/SO_(2),it also displays lower resistance of H_(2)O and SO_(2) than CuCe/CNT_1-SAPO-34.The catalytic performance made CuCe/CNT_1-SAPO-34 a promising catalyst for the NO_(x) emission control from diesel vehicles.
