Selective catalytic reduction with NH3(NH3-SCR)is an important means of NO_(x) abatement from stationary and mobile sources,and the key element is efficient and stable NH3-SCR catalysts.In this study,we propose a meth...Selective catalytic reduction with NH3(NH3-SCR)is an important means of NO_(x) abatement from stationary and mobile sources,and the key element is efficient and stable NH3-SCR catalysts.In this study,we propose a method to construct superior Fe-Beta catalysts based on Al-rich zeolites.This strategy successfully promotes the formation of NH3-SCR-active isolated Fe^(3+)species,thus effectively improving the low-temperature activity of the Fe-Beta catalysts.Thanks to the abundant Brønsted acid sites of the Al-rich zeolite,the Fe_(2)O_(3) particles are redispersed and anchored as isolated Fe^(3+)during hydrothermal aging.This dynamic evolution of Fe species makes up for the adverse effect of dealumination of the Al-rich zeolite framework and achieves high stability for the Al-rich Fe-Beta catalyst.This study may promote the understanding of highly efficient and stable catalyst design using Al-rich zeolites.展开更多
Hierarchical Fe-Beta obtained by hydrothermal synthesis exhibited higher low-temperature NH_3-SCR activity than conventional Fe-Beta. In order to identify the main factors leading to the difference in catalytic activi...Hierarchical Fe-Beta obtained by hydrothermal synthesis exhibited higher low-temperature NH_3-SCR activity than conventional Fe-Beta. In order to identify the main factors leading to the difference in catalytic activity, we investigated the pore structure, acidity and Fe sites of the hierarchical Fe-Beta and conventional Fe-Beta. The enhanced activity of hierarchical Fe-Beta was mainly due to the increase of the quantity of active Fe species. NH_3-TPD and DRIFTS results of NH_3 adsorption clearly verified that hierarchical Fe-Beta had more Lewis acid sites, which is beneficial to the adsorption and activation of NH_3. The H_2-TPR, UV–vis DRS, and EPR results confirmed that the hierarchical Fe-Beta had more isolated active Fe species, which may be associated with that the hierarchical structure introduced more structural defects as ion-exchange sites. Based on the analysis of kinetics experiments and the abovementioned characterizations, it can be concluded that the improvement of NH_3-SCR activity was not due to an intrinsic effect of the specific structural characteristics, but was related to more Fe active sites and better dispersion of Fe species in the hierarchical Fe-Beta.展开更多
Diesel engine exhaust comprises nitrogen oxides(NOx)and soot particles,which cause serious air pollution.However,owing to the contradictory nature of NO_(x)reduction and soot oxidation,a trade-off exists in the simult...Diesel engine exhaust comprises nitrogen oxides(NOx)and soot particles,which cause serious air pollution.However,owing to the contradictory nature of NO_(x)reduction and soot oxidation,a trade-off exists in the simultaneous removal of NO_(x)and soot.Consequently,catalytic technology has become a hot research topic.This study prepared MOδ/Fe-Beta(M=Fe,Co,Ni,Mn,Cu)catalysts through incipient wetness impregnation using Fe-Beta as the support and explored the catalytic performance of the above catalysts.The results exhibited the good performance of the prepared catalysts.The introduction of Mn resulted in a lower peak temperature of soot combustion for the catalyst,and slightly decreased deNOx performance of Fe-Beta.The soot combustion temperature was as low as 422℃,and the temperature window for 80%NO conversion was 164-423℃.The interaction between MnOd and zeolite can regulate the acid sites and produce sufficient active oxygen species for the catalyst.The catalytic activity of the MnOδ/Fe-Beta catalyst is due to its strong redox property,the appropriate number of acid sites,and sufficient number of active oxygen species.In addition,the catalyst had good stability and water and sulfur resistance,therefore it had great potential for future application in the simultaneous removal of NO_(x)and soot from diesel engine exhaust.展开更多
Two practical methods for highly stereoselective synthesis of (Z)-2-acylamido-4-phenylcrotonates 2a similar to b have been developed. The key step in the first route was how to control the acid-catalyzed isomerization...Two practical methods for highly stereoselective synthesis of (Z)-2-acylamido-4-phenylcrotonates 2a similar to b have been developed. The key step in the first route was how to control the acid-catalyzed isomerization of condensation mixtures of alpha-keto ester 5 with carbomite. In the second route the key step was reduction of oxime 8, derived from alpha-keto ester 5, with iron powder in the presence of acetic anhydride.展开更多
基金supported by the National Key R&D Program of China(No.2023YFC3707200)the National Natural Science Foundation of China(Nos.22306191 and 52270112).
文摘Selective catalytic reduction with NH3(NH3-SCR)is an important means of NO_(x) abatement from stationary and mobile sources,and the key element is efficient and stable NH3-SCR catalysts.In this study,we propose a method to construct superior Fe-Beta catalysts based on Al-rich zeolites.This strategy successfully promotes the formation of NH3-SCR-active isolated Fe^(3+)species,thus effectively improving the low-temperature activity of the Fe-Beta catalysts.Thanks to the abundant Brønsted acid sites of the Al-rich zeolite,the Fe_(2)O_(3) particles are redispersed and anchored as isolated Fe^(3+)during hydrothermal aging.This dynamic evolution of Fe species makes up for the adverse effect of dealumination of the Al-rich zeolite framework and achieves high stability for the Al-rich Fe-Beta catalyst.This study may promote the understanding of highly efficient and stable catalyst design using Al-rich zeolites.
基金financial supports from the National Natural Science Foundation of China (Nos. 51822811, 21637005)the National Key R&D Program of China (Nos. 2017YFC0212502, 2017YFC0211101)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment, CAS (No. CERAE201806)
文摘Hierarchical Fe-Beta obtained by hydrothermal synthesis exhibited higher low-temperature NH_3-SCR activity than conventional Fe-Beta. In order to identify the main factors leading to the difference in catalytic activity, we investigated the pore structure, acidity and Fe sites of the hierarchical Fe-Beta and conventional Fe-Beta. The enhanced activity of hierarchical Fe-Beta was mainly due to the increase of the quantity of active Fe species. NH_3-TPD and DRIFTS results of NH_3 adsorption clearly verified that hierarchical Fe-Beta had more Lewis acid sites, which is beneficial to the adsorption and activation of NH_3. The H_2-TPR, UV–vis DRS, and EPR results confirmed that the hierarchical Fe-Beta had more isolated active Fe species, which may be associated with that the hierarchical structure introduced more structural defects as ion-exchange sites. Based on the analysis of kinetics experiments and the abovementioned characterizations, it can be concluded that the improvement of NH_3-SCR activity was not due to an intrinsic effect of the specific structural characteristics, but was related to more Fe active sites and better dispersion of Fe species in the hierarchical Fe-Beta.
基金supported by National Natural Science Foundation of China(22372107,22072095,22202058)Postgraduate Education Reform Project of Liaoning Province(LNYJG2022400,LNYJG2023280)+3 种基金National Key Research and Development Program of China(2022YFB3506200,2022YFB3504100)Excellent Youth Science Foundation of Liaoning Province(2022-YQ-20)Shenyang Science and Technology Planning Project(22-322-3-28)Liaoning Xingliao talented youth Top talent program(XLYC2203007).
文摘Diesel engine exhaust comprises nitrogen oxides(NOx)and soot particles,which cause serious air pollution.However,owing to the contradictory nature of NO_(x)reduction and soot oxidation,a trade-off exists in the simultaneous removal of NO_(x)and soot.Consequently,catalytic technology has become a hot research topic.This study prepared MOδ/Fe-Beta(M=Fe,Co,Ni,Mn,Cu)catalysts through incipient wetness impregnation using Fe-Beta as the support and explored the catalytic performance of the above catalysts.The results exhibited the good performance of the prepared catalysts.The introduction of Mn resulted in a lower peak temperature of soot combustion for the catalyst,and slightly decreased deNOx performance of Fe-Beta.The soot combustion temperature was as low as 422℃,and the temperature window for 80%NO conversion was 164-423℃.The interaction between MnOd and zeolite can regulate the acid sites and produce sufficient active oxygen species for the catalyst.The catalytic activity of the MnOδ/Fe-Beta catalyst is due to its strong redox property,the appropriate number of acid sites,and sufficient number of active oxygen species.In addition,the catalyst had good stability and water and sulfur resistance,therefore it had great potential for future application in the simultaneous removal of NO_(x)and soot from diesel engine exhaust.
文摘Two practical methods for highly stereoselective synthesis of (Z)-2-acylamido-4-phenylcrotonates 2a similar to b have been developed. The key step in the first route was how to control the acid-catalyzed isomerization of condensation mixtures of alpha-keto ester 5 with carbomite. In the second route the key step was reduction of oxime 8, derived from alpha-keto ester 5, with iron powder in the presence of acetic anhydride.
