Ceria-zirconia based(CZ) materials are still a crucial component of three-way catalysts(TWCs) now.Compared with traditional cubic or tetragonal phase,CZ material with pyrochlore-type κ-Ce_(2)Zr_(2)O_(8) phase shows a...Ceria-zirconia based(CZ) materials are still a crucial component of three-way catalysts(TWCs) now.Compared with traditional cubic or tetragonal phase,CZ material with pyrochlore-type κ-Ce_(2)Zr_(2)O_(8) phase shows an excellent oxygen storage capacity,and thus is examined as a promising material for developing TWCs.Considering the remarkable surface Ce/Zr ratio change during the κ-Ce_(2)Zr_(2)O_(8) formation,we investigated the effects of surface Ce/Zr ratio on the formation of κ-Ce_(2)Zr_(2)O_(8) and on the supported Pdonly three-way catalysts.Raman and transmission electron microscopy(TEM) results demonstrate that partial κ-Ce_(2)Zr_(2)O_(8) structure is formed in the three oxides,and the content of κ-Ce_(2)Zr_(2)O_(8) structure increases with increasing surface Ce/Zr ratio,but its stability declines.After thermal aging,the proportions of Ce^(3+) and oxidized palladium(Pd^(δ+)+Pd^(2+)) in the catalysts,which are shown to be positively correlated with catalytic activity,follow the same sequence as the stability of κ-Ce_(2)Zr_(2)O_(8),namely Pd/M0.33 ROa> Pd/M0.4 ROa> Pd/CeM0.33 ROa.In particular,Pd/M0.33 RO,which possesses 100%((Pd^(δ+)+Pd^(2+))/Pd) even after thermal aging at 900℃ for 4 h,owing to the strengthened metal-support interaction by the presence of stable κ-Ce_(2)Zr_(2)O_(8),shows the best catalytic performance.This work is instructive to the application of κ-Ce_(2)Zr_(2)O_(8) in three-way catalysis.展开更多
采用柠檬酸溶胶 凝胶法制备的Ce Zr La O固溶体为载体,制备CuO Ce Zr La O催化剂,用XRD,Raman,TPR等实验技术对Ce Zr La O固溶体及CuO Ce Zr La O的物相、Redox性能进行了表征。实验结果表明,Ce0.7Zr0 3-yLayO固溶体的还原性能与La含量...采用柠檬酸溶胶 凝胶法制备的Ce Zr La O固溶体为载体,制备CuO Ce Zr La O催化剂,用XRD,Raman,TPR等实验技术对Ce Zr La O固溶体及CuO Ce Zr La O的物相、Redox性能进行了表征。实验结果表明,Ce0.7Zr0 3-yLayO固溶体的还原性能与La含量有关,适量的La能促进固溶体的氧化还原。CuO的负载量为6%时,CuO Ce0.7Zr0.15La0.15O的活性最高,高分散且与载体相互作用的CuO是CO氧化活性相。展开更多
Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improv...Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.展开更多
基金Project supported by the National Natural Science Foundation of China (21972097,21773189)。
文摘Ceria-zirconia based(CZ) materials are still a crucial component of three-way catalysts(TWCs) now.Compared with traditional cubic or tetragonal phase,CZ material with pyrochlore-type κ-Ce_(2)Zr_(2)O_(8) phase shows an excellent oxygen storage capacity,and thus is examined as a promising material for developing TWCs.Considering the remarkable surface Ce/Zr ratio change during the κ-Ce_(2)Zr_(2)O_(8) formation,we investigated the effects of surface Ce/Zr ratio on the formation of κ-Ce_(2)Zr_(2)O_(8) and on the supported Pdonly three-way catalysts.Raman and transmission electron microscopy(TEM) results demonstrate that partial κ-Ce_(2)Zr_(2)O_(8) structure is formed in the three oxides,and the content of κ-Ce_(2)Zr_(2)O_(8) structure increases with increasing surface Ce/Zr ratio,but its stability declines.After thermal aging,the proportions of Ce^(3+) and oxidized palladium(Pd^(δ+)+Pd^(2+)) in the catalysts,which are shown to be positively correlated with catalytic activity,follow the same sequence as the stability of κ-Ce_(2)Zr_(2)O_(8),namely Pd/M0.33 ROa> Pd/M0.4 ROa> Pd/CeM0.33 ROa.In particular,Pd/M0.33 RO,which possesses 100%((Pd^(δ+)+Pd^(2+))/Pd) even after thermal aging at 900℃ for 4 h,owing to the strengthened metal-support interaction by the presence of stable κ-Ce_(2)Zr_(2)O_(8),shows the best catalytic performance.This work is instructive to the application of κ-Ce_(2)Zr_(2)O_(8) in three-way catalysis.
文摘采用柠檬酸溶胶 凝胶法制备的Ce Zr La O固溶体为载体,制备CuO Ce Zr La O催化剂,用XRD,Raman,TPR等实验技术对Ce Zr La O固溶体及CuO Ce Zr La O的物相、Redox性能进行了表征。实验结果表明,Ce0.7Zr0 3-yLayO固溶体的还原性能与La含量有关,适量的La能促进固溶体的氧化还原。CuO的负载量为6%时,CuO Ce0.7Zr0.15La0.15O的活性最高,高分散且与载体相互作用的CuO是CO氧化活性相。
基金supported by the National Natural Science Foundation of China(21506194,21676255)the Provincial Natural Science Foundation of Zhejiang Province(LY16B070011)the Commission of Science and Technology of Zhejiang Province(2017C33106,2017C03007)~~
文摘Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.
