To improve the activity of Co/Al_(2)O_(3)catalysts in selective catalytic oxidation of ammonia(NH_(3)-SCO),valence state and size of active centers of Al_(2)O_(3)-supported Co catalysts were adjusted by conducting H_(...To improve the activity of Co/Al_(2)O_(3)catalysts in selective catalytic oxidation of ammonia(NH_(3)-SCO),valence state and size of active centers of Al_(2)O_(3)-supported Co catalysts were adjusted by conducting H_(2)reduction pretreatment.The NH_(3)-SCO activity of the adjusted 2Co/Al_(2)O_(3)catalyst was substantially improved,outperforming other catalysts with higher Co-loading.Fresh Co/Al_(2)O_(3)catalysts exhibited multitemperature reduction processes,enabling the control of the valence state of the Co-active centers by adjusting the reduction temperature.Changes in the state of the Co-active centers also led to differences in redox capacity of the catalysts,resulting in different reaction mechanisms for NH_(3)-SCO.However,in situ diffuse reflectance infrared Fourier transform spectra revealed that an excessive O_(2)activation capacity caused overoxidation of NH_(3)to NO and NO_(2).The NH_(3)-SCO activity of the 2Co/Al_(2)O_(3)catalyst with low redox capacity was successfully increased while controlling and optimizing the N_(2)selectivity by modulating the active centers via H_(2)pretreatment,which is a universalmethod used for enhancing the redox properties of catalysts.Thus,this method has great potential for application in the design of inexpensive and highly active catalysts.展开更多
基金supported by the National Natural Science Foundation of China(No.52260013)Yunnan Major Scientific and Technological Projects(No.202202AG050005).
文摘To improve the activity of Co/Al_(2)O_(3)catalysts in selective catalytic oxidation of ammonia(NH_(3)-SCO),valence state and size of active centers of Al_(2)O_(3)-supported Co catalysts were adjusted by conducting H_(2)reduction pretreatment.The NH_(3)-SCO activity of the adjusted 2Co/Al_(2)O_(3)catalyst was substantially improved,outperforming other catalysts with higher Co-loading.Fresh Co/Al_(2)O_(3)catalysts exhibited multitemperature reduction processes,enabling the control of the valence state of the Co-active centers by adjusting the reduction temperature.Changes in the state of the Co-active centers also led to differences in redox capacity of the catalysts,resulting in different reaction mechanisms for NH_(3)-SCO.However,in situ diffuse reflectance infrared Fourier transform spectra revealed that an excessive O_(2)activation capacity caused overoxidation of NH_(3)to NO and NO_(2).The NH_(3)-SCO activity of the 2Co/Al_(2)O_(3)catalyst with low redox capacity was successfully increased while controlling and optimizing the N_(2)selectivity by modulating the active centers via H_(2)pretreatment,which is a universalmethod used for enhancing the redox properties of catalysts.Thus,this method has great potential for application in the design of inexpensive and highly active catalysts.
