摘要
助剂表面改性是提高铈基材料热稳定性、还原性能及其负载单Pd三效催化剂低温活性的经典方法之一。揭示助剂表面改性的作用机制,对于研发高性能CeO_(2)-ZrO_(2)-Al_(2)O_(3)(CZA)材料,满足日趋严格的汽油车尾气污染物排放标准,解决尾气污染具有现实意义。基于引入助剂Pr_(6)O_(11)可以提升CZA的低温还原性能,进一步研究了不同Pr_(6)O_(11)含量(0、3%、5%、7%和9%,质量分数)对其氧化还原性能和热稳定性的影响。N_(2)吸/脱附、X射线衍射(XRD)、H_(2)-程序升温还原(H_(2)-TPR)和储氧量等表征结果表明,Pr_(6)O_(11)的表面改性可在一定程度上降低CeO_(2)-ZrO_(2)(CZ)纳米晶的烧结驱动力,抑制CZ晶粒烧结。同时,引入Pr_(6)O_(11)促进材料产生了更多氧空位,从而提高了其还原性能和储氧性能。其中,Pr_(6)O_(11)含量为5%时,改性CZA表现出最佳的热稳定性、还原性能和储氧性能,1000℃下老化4 h后比表面积和孔容最大(85 m^(2)/g和0.33 mL/g),CZ晶粒尺寸最小(6.9 nm),还原峰温低至532℃,400℃储氧量增至109μmol/g。因此,该改性CZA负载的单Pd三效催化剂表现出最优的催化活性,其CO、NO、C3H8和C3H6的t50(污染物转化率为50%时所需温度)较未改性催化剂分别降低了6℃、15℃、18℃和6℃。综上,在CZA材料中添加适量的Pr_(6)O_(11),可有效提高其负载单Pd三效催化剂的低温活性。该方法简单经济,具有较好的应用前景。
Surface modification by promoters is one of the classic methods to improve the thermal stability,reducibility,and lowtemperature activity of cerium-based materials and their supported Pd-only three-way catalysts.Revealing the mechanism of surface modification by promoters is of practical significance for the development of high-performance CeO_(2)-ZrO_(2)-Al_(2)O_(3)(CZA)materials to meet the increasingly strict regulations on gasoline vehicle exhaust emission and to solve the exhaust pollution.On the basis of the promoting effects of Pr_(6)O_(11) on improving the low-temperature reducibility of CZA materials,the effects of different content of Pr_(6)O_(11)(0,3%,5%,7%,and 9%,mass fraction)on the redox performance and thermal stability of CZA materials were further studied.The characterization results of N_(2) adsorption/desorption,X-ray diffraction(XRD),H_(2) temperature programmed reduction(H_(2)-TPR)and oxygen storage capacity show that the surface modification of CZA by Pr_(6)O_(11) can reduce the driving force of CeO_(2)-ZrO_(2)(CZ)sintering and thus inhibit the growth of nanoparticles.At the same time,the introduction of Pr_(6)O_(11) also promotes to produce more oxygen vacancies in the material,thus improving its reducibility and oxygen storage performance.Among them,when the content of Pr_(6)O_(11) is 5%,the modified CZA exhibits the best thermal stability,redox performance and oxygen storage performance.After aging at 1000℃for 4 h,it exhibits the highest specific surface area(85 m^(2)/g)and pore volume(0.33 mL/g),the smallest crystal size of CZ(6.9 nm),the lowest reduction temperature(532℃)and the highest oxygen storage capacity of 109μmol/g at 400℃.Therefore,the modified CZA supported Pd-only three-way catalyst exhibits the optimal catalytic activity,with the t50(required temperature at the pollutant conversion rate of 50%)of CO,NO,C3H8 and C3H6 reduced by 6℃,15℃,18℃and 6℃,respectively,compared to the unmodified catalysts.In summary,the low-temperature activity of Pd-only thee-way catalyst
作者
张俊杰
王大军
李珊珊
李洁
陈耀壮
韩太宇
杨禛祯
王光永
ZHANG Junjie;WANG Dajun;LI Shanshan;LI Jie;CHEN Yaozhuang;HAN Taiyu;YANG Zhenzhen;WANG Guangyong(State Key Laboratory of Industrial Vent Gas Reuse,National Engineering Research Center for C1 Chemistry,Southwest Institute of Chemical Co.,Ltd.,Chengdu 610025,Sichuan,China;College of Chemistry,Sichuan University,Chengdu 610064,Sichuan,China)
出处
《低碳化学与化工》
CAS
北大核心
2024年第10期72-80,共9页
Low-Carbon Chemistry and Chemical Engineering
基金
四川省自然科学基金-青年科学基金(2022NSFSC1206)。
