离子型稀土矿对铵离子的吸附-解吸行为直接影响矿区氨氮污染的去除效率。本文以NH_(4)^(+)和碱金属离子(Li^(+)、Na^(+)、K^(+))饱和稀土矿为对象,通过NH_(4)^(+)吸附-解吸热力学和动力学试验,研究了NH_(4)^(+)在矿土表面的吸附-解吸特...离子型稀土矿对铵离子的吸附-解吸行为直接影响矿区氨氮污染的去除效率。本文以NH_(4)^(+)和碱金属离子(Li^(+)、Na^(+)、K^(+))饱和稀土矿为对象,通过NH_(4)^(+)吸附-解吸热力学和动力学试验,研究了NH_(4)^(+)在矿土表面的吸附-解吸特性。结果表明,碱金属饱和矿土对NH_(4)^(+)的吸附量由大至小的顺序为Li饱和矿土>Na饱和矿土>K饱和矿土,而在碱金属离子作用下铵饱和矿土中NH_(4)^(+)的解吸量由大至小的顺序为K^(+)>Na^(+)>Li^(+);上述吸附-解吸行为均能较好地符合Langmuir等温模型。动力学分析结果表明,NH_(4)^(+)的吸附-解吸过程更契合准一级动力学模型,且计算所得的低反应活化能(<40 k J/mmol)进一步证实了该吸附过程受扩散主导。在不同碱金属离子体系中,NH_(4)^(+)解吸活化能呈现Li^(+)>Na^(+)>K^(+)的递减趋势,而碱金属饱和矿土对NH_(4)^(+)的吸附活化能顺序则相反(即K^(+)>Na^(+)>Li^(+))。这种活化能的能垒差异引发的动力学限制,最终导致了矿土中NH_(4)^(+)亚稳态平衡吸附的离子特异性。展开更多
Under the context of global energy transition and carbon neutrality,controlling nitrogen oxide(NO_(x))emissions from biomass combustion is of great significance,and the development of high-efficiency low-temperature c...Under the context of global energy transition and carbon neutrality,controlling nitrogen oxide(NO_(x))emissions from biomass combustion is of great significance,and the development of high-efficiency low-temperature catalysts has become a current research focus.In this study,Nb was used to dope and modify the Mn_(7)-Cu_(3)/BCN catalyst to construct the Mn_(7)-Cu_(3)-Nb_(x)/BCN system.The doping amount was optimized through selective catalytic reduction(SCR)activity tests.The reaction mechanism was explored by combining in situ DRIFTS and density functional theory(DFT)simulations.Experimental findings revealed that the catalyst doped with 0.05%Nb achieved the optimal performance,sustaining a NO conversion efficiency of≥94%within the temperature window of 150−275℃while demonstrating improved resistance to alkali metal K poisoning.Mechanistic analyses showed that at low temperatures,the catalyst facilitated the SCR reaction via both the Eley-Rideal(E-R)and Langmuir-Hinshelwood(L-H)pathways,with the synergistic interaction between multiple active sites driving the efficient conversion of NH3 and NO.DFT calculations further confirmed that both pathways had the characteristics of low reaction energy barriers and significant exothermicity,ensuring the high activity and feasibility of the low-temperature reaction.The findings provided foundational theoretical support for the design of Nb-doped Mn-Cu-supported catalysts and the exploration of the underlying working mechanisms.展开更多
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
本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_...本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_(3)占比的增大,火焰高度变长,燃烧室出口的NO排放量呈先增大后减小的趋势且在NH_(3)占比为50%达到峰值;在50%掺氨工况下采用轴向空气分级使一级燃烧室处于富燃状态可以有效降低NO的排放,其中分级风的最佳比例范围是30%~50%(当量比1.21~1.70),且随着分级风高度的增大呈下降趋势;此外,在最佳分级风比例和高度条件下(分级风高度80 mm、占比30%),增加分级风的喷口数目可减轻分级风碰撞对上游主燃区富燃状态的影响,使NO排放进一步降低。展开更多
文摘离子型稀土矿对铵离子的吸附-解吸行为直接影响矿区氨氮污染的去除效率。本文以NH_(4)^(+)和碱金属离子(Li^(+)、Na^(+)、K^(+))饱和稀土矿为对象,通过NH_(4)^(+)吸附-解吸热力学和动力学试验,研究了NH_(4)^(+)在矿土表面的吸附-解吸特性。结果表明,碱金属饱和矿土对NH_(4)^(+)的吸附量由大至小的顺序为Li饱和矿土>Na饱和矿土>K饱和矿土,而在碱金属离子作用下铵饱和矿土中NH_(4)^(+)的解吸量由大至小的顺序为K^(+)>Na^(+)>Li^(+);上述吸附-解吸行为均能较好地符合Langmuir等温模型。动力学分析结果表明,NH_(4)^(+)的吸附-解吸过程更契合准一级动力学模型,且计算所得的低反应活化能(<40 k J/mmol)进一步证实了该吸附过程受扩散主导。在不同碱金属离子体系中,NH_(4)^(+)解吸活化能呈现Li^(+)>Na^(+)>K^(+)的递减趋势,而碱金属饱和矿土对NH_(4)^(+)的吸附活化能顺序则相反(即K^(+)>Na^(+)>Li^(+))。这种活化能的能垒差异引发的动力学限制,最终导致了矿土中NH_(4)^(+)亚稳态平衡吸附的离子特异性。
基金Supported by National Key Research and Development Program of China(2020YFD1100302)。
文摘Under the context of global energy transition and carbon neutrality,controlling nitrogen oxide(NO_(x))emissions from biomass combustion is of great significance,and the development of high-efficiency low-temperature catalysts has become a current research focus.In this study,Nb was used to dope and modify the Mn_(7)-Cu_(3)/BCN catalyst to construct the Mn_(7)-Cu_(3)-Nb_(x)/BCN system.The doping amount was optimized through selective catalytic reduction(SCR)activity tests.The reaction mechanism was explored by combining in situ DRIFTS and density functional theory(DFT)simulations.Experimental findings revealed that the catalyst doped with 0.05%Nb achieved the optimal performance,sustaining a NO conversion efficiency of≥94%within the temperature window of 150−275℃while demonstrating improved resistance to alkali metal K poisoning.Mechanistic analyses showed that at low temperatures,the catalyst facilitated the SCR reaction via both the Eley-Rideal(E-R)and Langmuir-Hinshelwood(L-H)pathways,with the synergistic interaction between multiple active sites driving the efficient conversion of NH3 and NO.DFT calculations further confirmed that both pathways had the characteristics of low reaction energy barriers and significant exothermicity,ensuring the high activity and feasibility of the low-temperature reaction.The findings provided foundational theoretical support for the design of Nb-doped Mn-Cu-supported catalysts and the exploration of the underlying working mechanisms.
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.
文摘本研究基于自行搭建的5 k W旋流预混火焰实验台,开展了轴向空气分级方式下CH_(4)/NH_(3)旋流预混火焰的实验测试,重点考察了分级风比例、分级风高度及分级风喷口数目对CH_(4)/NH_(3)旋流预混火焰燃烧及排放特性的影响。结果表明:随着NH_(3)占比的增大,火焰高度变长,燃烧室出口的NO排放量呈先增大后减小的趋势且在NH_(3)占比为50%达到峰值;在50%掺氨工况下采用轴向空气分级使一级燃烧室处于富燃状态可以有效降低NO的排放,其中分级风的最佳比例范围是30%~50%(当量比1.21~1.70),且随着分级风高度的增大呈下降趋势;此外,在最佳分级风比例和高度条件下(分级风高度80 mm、占比30%),增加分级风的喷口数目可减轻分级风碰撞对上游主燃区富燃状态的影响,使NO排放进一步降低。
