So far,it is still a controversial issue which status of gold species is a better active site for catalyzing CO oxidation.Herein,the influence of the different atmospheres pretreatment(oxidative and reductive)on gold ...So far,it is still a controversial issue which status of gold species is a better active site for catalyzing CO oxidation.Herein,the influence of the different atmospheres pretreatment(oxidative and reductive)on gold state of Au/La-CeOx(1 wt%gold loading)catalyst during CO oxidation was studied.The changes of Au species were monitored by combined in situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS)and X-ray photoelectron spectroscopy(XPS).For the sample pretreated with oxidative atmosphere,the data show that the initial Au^(3+)is transformed to Au^(δ+)(0<δ<1)during CO oxidation,which is a key step to lead to higher reactivity.For the sample after reductive atmosphere pretreatment,Au^(δ+)is mixed with a small amount of Au^(0)which can be converted to Au^(δ+)with the increase of temperature in reaction.Meanwhile,the sample always maintains high activity during the reaction.Therefore,the Au®+obtained by reductive pretreatment is more active than the Au^(3+)obtained by oxidative treatment in catalyzing CO oxidation.展开更多
Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these...Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these pretreated catalysts were aged at 1000 °C for 3 h to study their anti-aging properties. The catalytic activities of the catalysts were investigated detailedly, and the results showed that the catalyst pretreated at 800 °C before aging treatment possessed the best anti-aging performance for CHoxidation. XRD and XPS results indicated that well-crystallized CeOparticles were formed during calcinations at 800 °C, which made CeOan effective promoter. HRTEM revealed that Pd particles found on the edge of CeOover the aged catalyst pretreated at 800 °C were relatively smaller than those over the catalysts without pretreatment. H-TPR and XPS results also implied that the interaction between well-crystallized CeOand Pd suppressed the deactivation of PdO sites and further enhanced the catalytic performance.展开更多
基金Project supported by the Excellent Young Scientists Fund from the National Science Foundation of China(NSFC)(21622106)other projects from the NSFC(21771117,21805167).
文摘So far,it is still a controversial issue which status of gold species is a better active site for catalyzing CO oxidation.Herein,the influence of the different atmospheres pretreatment(oxidative and reductive)on gold state of Au/La-CeOx(1 wt%gold loading)catalyst during CO oxidation was studied.The changes of Au species were monitored by combined in situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS)and X-ray photoelectron spectroscopy(XPS).For the sample pretreated with oxidative atmosphere,the data show that the initial Au^(3+)is transformed to Au^(δ+)(0<δ<1)during CO oxidation,which is a key step to lead to higher reactivity.For the sample after reductive atmosphere pretreatment,Au^(δ+)is mixed with a small amount of Au^(0)which can be converted to Au^(δ+)with the increase of temperature in reaction.Meanwhile,the sample always maintains high activity during the reaction.Therefore,the Au®+obtained by reductive pretreatment is more active than the Au^(3+)obtained by oxidative treatment in catalyzing CO oxidation.
基金Project supported by the National Natural Science Foundation of China(21173153)the National Hi-tech Research Development Program of China(863 Program,2013AA065304)the Sichuan Science and Technology Agency Supported Project(2012FZ0008)
文摘Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these pretreated catalysts were aged at 1000 °C for 3 h to study their anti-aging properties. The catalytic activities of the catalysts were investigated detailedly, and the results showed that the catalyst pretreated at 800 °C before aging treatment possessed the best anti-aging performance for CHoxidation. XRD and XPS results indicated that well-crystallized CeOparticles were formed during calcinations at 800 °C, which made CeOan effective promoter. HRTEM revealed that Pd particles found on the edge of CeOover the aged catalyst pretreated at 800 °C were relatively smaller than those over the catalysts without pretreatment. H-TPR and XPS results also implied that the interaction between well-crystallized CeOand Pd suppressed the deactivation of PdO sites and further enhanced the catalytic performance.
