The causes of deactivation of SCR denitrification catalyst used in a glass furnace were studied by means of low temperature nitrogen adsorption and desorption characterization,X-ray fluorescence spectrometry analysis,...The causes of deactivation of SCR denitrification catalyst used in a glass furnace were studied by means of low temperature nitrogen adsorption and desorption characterization,X-ray fluorescence spectrometry analysis,and thermogravimetric-mass spectrometry-infrared characterization.The results show that the main causes of sample A inactivation were serious alkali/alkaline earth metal poisoning and As poisoning;sample B was weakly affected by alkali/alkaline earth metal poisoning,mainly by As poisoning and P poisoning.Severe micropore and mesoporous blockage occurred in the inactivated samples A and B,mainly due to tar adsorption and the deposition of large amounts of ammonium bisulfate and metal sulfate in the carrier.The tar and ammonium sulfate adsorbed in the catalyst can be effectively removed before being heated to 550℃.展开更多
Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)sh...Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)shows average activity,however,it exhibits a poor N_(2)selectivity.Nb_(2)O_(5)is not active for NH_(3)-SCR.However,the mixed Co_(3)-Nb-O_(x) catalyst shows higher NO conversion and N_(2)selectivity than the single Co_(3)O_(4)and Nb_(2)O_(5)catalysts at 100–300℃.The results of temperature programmed reduction by H_(2)and X-ray photoelectron(XP)spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co^(3+) and Oa,adjusting the activity for catalytic oxidation to a moderate level.This suppresses the formation of undesired N_(2)O from the over-oxidation of NH_(3).Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity,ensuring the high catalytic activity and N2 selectivity in NH3-SCR.展开更多
The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic a...The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic activity measurements indicate that the mixed oxide Ce-Nb-O_(x) presents a higher SCR activity than the single oxide CeO_(2) or Nb_(2)O_(5) catalyst.In addition,the Ce-Nb-O_(x) catalyst shows high resistance towards H_(2)O and SO_(2) at 280℃.The Raman,X-ray photoelectron spectra and temperature programmed reduction with H_(2) results indicate that the incorporation of Nb provides abundant oxygen vacancies for capturing more surface adsorbed oxygen,which provides a superior redox capability and accelerates the renewal of active sites.Furthermore,the Fourier transform infrared spectra and temperature programmed desorption of NH_(3) results suggest that niobium pentoxide shows high surface acidity,which is partly retained in the Ce-Nb-O_(x) catalyst possessing a high content of Lewis and Br?nsted acid sites.Therefore,the incorporation of Nb improves both the redox and acidic capacities of Ce-Nb-O_(x) catalyst for the SCR reaction.Here,the redox behavior is primarily taken on Ce and the acidity is well improved by Nb,so the synergistic effect should exist between Ce and Nb.In terms of the reaction mechanism,in situ DRIFT experiments suggest that both NH_(3) on Lewis acid sites and NH_(4)^(+) on Bronsted acid sites can react with NO species,and adsorbed NO and NO_(2) species can both be reduced by NH_(3).In the SCR process,O_(2) primarily acts as the accelerant to improve the redox and acid cycles and plays an important role.This work proves that the combination of redox and acidic properties of different constituents can be feasible for catalyst design to obtain a superior SCR performance.展开更多
文摘The causes of deactivation of SCR denitrification catalyst used in a glass furnace were studied by means of low temperature nitrogen adsorption and desorption characterization,X-ray fluorescence spectrometry analysis,and thermogravimetric-mass spectrometry-infrared characterization.The results show that the main causes of sample A inactivation were serious alkali/alkaline earth metal poisoning and As poisoning;sample B was weakly affected by alkali/alkaline earth metal poisoning,mainly by As poisoning and P poisoning.Severe micropore and mesoporous blockage occurred in the inactivated samples A and B,mainly due to tar adsorption and the deposition of large amounts of ammonium bisulfate and metal sulfate in the carrier.The tar and ammonium sulfate adsorbed in the catalyst can be effectively removed before being heated to 550℃.
基金This work was financially supported by the National Key R&D Projects(No.2019YFC1907101)the National Natural Science Foundation of China(No.U2002212)+2 种基金the State Key Laboratory for Advanced Metals and Materials(No.2019Z-05)the Fundamental Research Funds for the Central Universities(Nos.FRFIDRY-20-005 and FRF-TP-20-097A1Z)the Postdoctor Research Foundation of Shunde Graduate School of University of Science and Technology Beijing(No.2020BH012).
文摘Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)shows average activity,however,it exhibits a poor N_(2)selectivity.Nb_(2)O_(5)is not active for NH_(3)-SCR.However,the mixed Co_(3)-Nb-O_(x) catalyst shows higher NO conversion and N_(2)selectivity than the single Co_(3)O_(4)and Nb_(2)O_(5)catalysts at 100–300℃.The results of temperature programmed reduction by H_(2)and X-ray photoelectron(XP)spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co^(3+) and Oa,adjusting the activity for catalytic oxidation to a moderate level.This suppresses the formation of undesired N_(2)O from the over-oxidation of NH_(3).Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity,ensuring the high catalytic activity and N2 selectivity in NH3-SCR.
基金Project supported by the Postdoctor Research Foundation of Shunde Graduate School of University of Science and Technology Beijing(2020BH012)the National Key Research&Development Projects(2021YFC1910504)+1 种基金the National Natural Science Foundation of China(U2002212)the Fundamental Research Funds for the Central Universities(FRF-IDRY-20-005)。
文摘The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic activity measurements indicate that the mixed oxide Ce-Nb-O_(x) presents a higher SCR activity than the single oxide CeO_(2) or Nb_(2)O_(5) catalyst.In addition,the Ce-Nb-O_(x) catalyst shows high resistance towards H_(2)O and SO_(2) at 280℃.The Raman,X-ray photoelectron spectra and temperature programmed reduction with H_(2) results indicate that the incorporation of Nb provides abundant oxygen vacancies for capturing more surface adsorbed oxygen,which provides a superior redox capability and accelerates the renewal of active sites.Furthermore,the Fourier transform infrared spectra and temperature programmed desorption of NH_(3) results suggest that niobium pentoxide shows high surface acidity,which is partly retained in the Ce-Nb-O_(x) catalyst possessing a high content of Lewis and Br?nsted acid sites.Therefore,the incorporation of Nb improves both the redox and acidic capacities of Ce-Nb-O_(x) catalyst for the SCR reaction.Here,the redox behavior is primarily taken on Ce and the acidity is well improved by Nb,so the synergistic effect should exist between Ce and Nb.In terms of the reaction mechanism,in situ DRIFT experiments suggest that both NH_(3) on Lewis acid sites and NH_(4)^(+) on Bronsted acid sites can react with NO species,and adsorbed NO and NO_(2) species can both be reduced by NH_(3).In the SCR process,O_(2) primarily acts as the accelerant to improve the redox and acid cycles and plays an important role.This work proves that the combination of redox and acidic properties of different constituents can be feasible for catalyst design to obtain a superior SCR performance.
