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
Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst support.The performance of the catalysts was tested to study the effect o...Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst support.The performance of the catalysts was tested to study the effect of support on Mn-based catalyst activity.Performance of the catalysts followed as Mn_(0.4)/Al>Mn_(0.2)/Al>Mn_(0.4)/Ti>Mn_(0.2)/Ti>MnO_(x)>Al_(2)O_(3)on the whole,indicating the synergism of MnO_(x)and Al_(2)O_(3)for NO catalytic oxidation.Results were analyzed according to characterization data.Adsorbed oxygen on catalyst rather than lattice oxygen was detected as the active oxidizer for NO oxidation.As catalyst support,Al_(2)O_(3)provided more sites to carry surface adsorbed oxygen than TiO_(2),resulting in the presence of more active oxygen on Mn O_(x)/Al_(2)O_(3)than on MnO_(x)/TiO_(2).Moreover,MnO_(x)/Al_(2)O_(3)possessed high surface area and pore volume,which greatly benefited the adsorption of NO on catalyst and further favored the oxidation of NO by active oxygen.All these advantages helped Mn_(0.4)/Al exhibited the best catalytic efficiency.展开更多
Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study ...Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study is to provide a reference for the accurate estimation of the total LNO_(x) in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018.The energy of each CG flash was based on the number of return strokes per CG flash,the peak current of each return stroke,and the assumed CG breakdown voltage.The energy of intracloud lightning(IC)was based on the estimated frequencies of IC and the assumed energy of each IC flash.Combining the energy of lightning and the number of nitric oxide(NO)molecules produced by unit energy(ρno),the total LNO_(x) production in the mainland of China was determined.The LNO_(x) in the mainland of China estimated in this study is in the range(0.157-0.321)×10^(9) kg per year[Tg(N)yr-1],which is on the high end of other scholars’works.Negative cloud-to-ground lightning(NCG)flashes produce the most moles of NO_(x),while positive cloud-to-ground lightning(PCG)flashes produce the least total moles of NO_(x).The breakdown voltage of PCG is greater than that of IC or NCG,while the latter has a greater output of LNO_(x).展开更多
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.
基金supported by the National Natural Science Foundation of China(51906193)the Fundamental Research Funds for the Central Universities(xjh012019013)+1 种基金the Basic Research Program of Natural Science in Shaanxi Province(2020JQ-039)support from Young Talent Support Program of Xi'an Association for Science and Technology。
文摘Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst support.The performance of the catalysts was tested to study the effect of support on Mn-based catalyst activity.Performance of the catalysts followed as Mn_(0.4)/Al>Mn_(0.2)/Al>Mn_(0.4)/Ti>Mn_(0.2)/Ti>MnO_(x)>Al_(2)O_(3)on the whole,indicating the synergism of MnO_(x)and Al_(2)O_(3)for NO catalytic oxidation.Results were analyzed according to characterization data.Adsorbed oxygen on catalyst rather than lattice oxygen was detected as the active oxidizer for NO oxidation.As catalyst support,Al_(2)O_(3)provided more sites to carry surface adsorbed oxygen than TiO_(2),resulting in the presence of more active oxygen on Mn O_(x)/Al_(2)O_(3)than on MnO_(x)/TiO_(2).Moreover,MnO_(x)/Al_(2)O_(3)possessed high surface area and pore volume,which greatly benefited the adsorption of NO on catalyst and further favored the oxidation of NO by active oxygen.All these advantages helped Mn_(0.4)/Al exhibited the best catalytic efficiency.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91537209 and 91644224)
文摘Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study is to provide a reference for the accurate estimation of the total LNO_(x) in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018.The energy of each CG flash was based on the number of return strokes per CG flash,the peak current of each return stroke,and the assumed CG breakdown voltage.The energy of intracloud lightning(IC)was based on the estimated frequencies of IC and the assumed energy of each IC flash.Combining the energy of lightning and the number of nitric oxide(NO)molecules produced by unit energy(ρno),the total LNO_(x) production in the mainland of China was determined.The LNO_(x) in the mainland of China estimated in this study is in the range(0.157-0.321)×10^(9) kg per year[Tg(N)yr-1],which is on the high end of other scholars’works.Negative cloud-to-ground lightning(NCG)flashes produce the most moles of NO_(x),while positive cloud-to-ground lightning(PCG)flashes produce the least total moles of NO_(x).The breakdown voltage of PCG is greater than that of IC or NCG,while the latter has a greater output of LNO_(x).
