Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve ...Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.展开更多
irritation to human beings.The removal of hexanal has rarely been investigated.In this study,we found that the amount of Mn vacancies inγ-MnOOH significantly affects its catalytic activity toward hexanal degradation ...irritation to human beings.The removal of hexanal has rarely been investigated.In this study,we found that the amount of Mn vacancies inγ-MnOOH significantly affects its catalytic activity toward hexanal degradation and transformation into CO2.The as-synthesized Mn vacancy-richγ-MnOOH exhibited high efficiency toward hexanal removal,achieving 100%degradation of 15 ppm hexanal at 85℃ and complete transformation into CO2 at 160 ℃ under the gas hourly space velocity of 240 L/(g·h);its activity could be completely regenerated by in-situ heat treatment at 180°C.Moreover,it was found that the degradation of hexanal occurred in a stepwise manner,i.e.,losing one CH2 unit per step.Electron spinning resonance studies detected strong indicative signals for the presence of the superoxide anion radical(?O2^–)on Mn-vacancy-richγ-MnOOH,which may act as active oxygen species for the hexanal degradation.Understanding the role of Mn-vacancy and the mechanism of hexanal degradation byγ-MnOOH are essential for developing efficient oxide catalysts for volatile organic compounds besides hexanal.展开更多
To reveal the intraspecific evolution of Leptospirillum ferriphilum isolates which thrived in industrial bioleaching ecosystems and acid mine drainages,genome sequences of L.ferriphilum YSK,L.ferriphilum DX and L.ferr...To reveal the intraspecific evolution of Leptospirillum ferriphilum isolates which thrived in industrial bioleaching ecosystems and acid mine drainages,genome sequences of L.ferriphilum YSK,L.ferriphilum DX and L.ferriphilum ZJ were determined to compare with complete genome of L.ferriphilum ML-04.The genome comparisons reveal that extensive intraspecific variation occurs in their genomes,and that the loss and insertion of novel gene blocks of probable phage origin may mostly contribute to heterogeneity of gene content among L.ferriphilum genomes.Surprisingly,a nif gene cluster is identified in L.ferriphilum YSK and L.ferriphilum ZJ genomes.Intensive analysis and further experiments indicate that the nif gene cluster in L.ferriphilum YSK inherits from ancestor rather than lateral gene transfer.Overall,results suggest that the population of L.ferriphilum undergoes frequent genetic recombination,resulting in many closely related genome types in recent evolution.The combinatorial processes profoundly shape their physiologies and provide the basis for adaptation to different niches.展开更多
基金supported by the National Key R&D Program of China(2016YFC0203900,2016YFC0203901)National Natural Science Foundation of China(51778619,21577173)~~
文摘Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.
基金supported by National Natural Science Foundation of China (21677083)Suzhou-Tsinghua Innovation Guiding Program (2016SZ0104)~~
文摘irritation to human beings.The removal of hexanal has rarely been investigated.In this study,we found that the amount of Mn vacancies inγ-MnOOH significantly affects its catalytic activity toward hexanal degradation and transformation into CO2.The as-synthesized Mn vacancy-richγ-MnOOH exhibited high efficiency toward hexanal removal,achieving 100%degradation of 15 ppm hexanal at 85℃ and complete transformation into CO2 at 160 ℃ under the gas hourly space velocity of 240 L/(g·h);its activity could be completely regenerated by in-situ heat treatment at 180°C.Moreover,it was found that the degradation of hexanal occurred in a stepwise manner,i.e.,losing one CH2 unit per step.Electron spinning resonance studies detected strong indicative signals for the presence of the superoxide anion radical(?O2^–)on Mn-vacancy-richγ-MnOOH,which may act as active oxygen species for the hexanal degradation.Understanding the role of Mn-vacancy and the mechanism of hexanal degradation byγ-MnOOH are essential for developing efficient oxide catalysts for volatile organic compounds besides hexanal.
基金Project(2018YFC1801804)supported by the National Key R&D Program of ChinaProjects(2016JJ3146,2017JJ3160)supported by the Natural Science Foundation of Hunan Province,China。
文摘To reveal the intraspecific evolution of Leptospirillum ferriphilum isolates which thrived in industrial bioleaching ecosystems and acid mine drainages,genome sequences of L.ferriphilum YSK,L.ferriphilum DX and L.ferriphilum ZJ were determined to compare with complete genome of L.ferriphilum ML-04.The genome comparisons reveal that extensive intraspecific variation occurs in their genomes,and that the loss and insertion of novel gene blocks of probable phage origin may mostly contribute to heterogeneity of gene content among L.ferriphilum genomes.Surprisingly,a nif gene cluster is identified in L.ferriphilum YSK and L.ferriphilum ZJ genomes.Intensive analysis and further experiments indicate that the nif gene cluster in L.ferriphilum YSK inherits from ancestor rather than lateral gene transfer.Overall,results suggest that the population of L.ferriphilum undergoes frequent genetic recombination,resulting in many closely related genome types in recent evolution.The combinatorial processes profoundly shape their physiologies and provide the basis for adaptation to different niches.
