Ca-type todorokite catalysts were designed and prepared by a simple redox method and applied to the selective reduction of NO_(x) by NH_(3)(NH_(3)-SCR)for the first time.Compared with the Na-type manjiroite prepared b...Ca-type todorokite catalysts were designed and prepared by a simple redox method and applied to the selective reduction of NO_(x) by NH_(3)(NH_(3)-SCR)for the first time.Compared with the Na-type manjiroite prepared by the same method,the todorokite catalysts with different Mn/Ca ratios showed greatly improved catalytic activity for NO_(x) reduction.Among them,Mn8Ca4 catalyst exhibited the best NH_(3)-SCR performance,achieving 90%NO_(x) conversion within temperature range of 70-275℃ and having a high sulphur resistance.Compared to the Na-type manjiroite sample,Ca-type todorokite catalysts possessed an increased size of tunnel,resulting in a larger specific surface area.As increased the amounts of Ca doping,the Na content in Ca-type todorokite catalysts significantly decreased,providing larger amounts of Bronsted acid sites for NH_(3) adsorption to produce NH_(4)^(+).The NH_(4)^(+)species were highly active for reaction with NO+O_(2),playing a determining role in NH_(3)-SCR process at low temperatures.Meanwhile,larger amounts of surface adsorbed oxygen contained over the Ca-doping samples than that over Na-type manjiroite,promoting the oxidation of NO and fast SCR processes.Over the Ca-type todorokite catalysts,furthermore,nitrates produced during the flow of NO+O_(2),were more active for reaction with NH_(3) than that over Na-type manjiroite,benefiting the occurrence of NH_(3)-SCR process.This study provides novel insights into the design of NH_(3)-SCR catalysts with high performance.展开更多
基金supported by Self-deployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(No.E055C003)the National Natural Science Foundation of China(Nos.U20B6004 and 22072179)
文摘Ca-type todorokite catalysts were designed and prepared by a simple redox method and applied to the selective reduction of NO_(x) by NH_(3)(NH_(3)-SCR)for the first time.Compared with the Na-type manjiroite prepared by the same method,the todorokite catalysts with different Mn/Ca ratios showed greatly improved catalytic activity for NO_(x) reduction.Among them,Mn8Ca4 catalyst exhibited the best NH_(3)-SCR performance,achieving 90%NO_(x) conversion within temperature range of 70-275℃ and having a high sulphur resistance.Compared to the Na-type manjiroite sample,Ca-type todorokite catalysts possessed an increased size of tunnel,resulting in a larger specific surface area.As increased the amounts of Ca doping,the Na content in Ca-type todorokite catalysts significantly decreased,providing larger amounts of Bronsted acid sites for NH_(3) adsorption to produce NH_(4)^(+).The NH_(4)^(+)species were highly active for reaction with NO+O_(2),playing a determining role in NH_(3)-SCR process at low temperatures.Meanwhile,larger amounts of surface adsorbed oxygen contained over the Ca-doping samples than that over Na-type manjiroite,promoting the oxidation of NO and fast SCR processes.Over the Ca-type todorokite catalysts,furthermore,nitrates produced during the flow of NO+O_(2),were more active for reaction with NH_(3) than that over Na-type manjiroite,benefiting the occurrence of NH_(3)-SCR process.This study provides novel insights into the design of NH_(3)-SCR catalysts with high performance.
