高分散还原态Pt基催化剂的制备及其NO氧化的催化性能  

Preparation of Reduced Pt-Based Catalysts with High Dispersion and Their Catalytic Performances for NO Oxidation

作　　者：丁心湄 梁艳丽 张海龙 赵明[1] 王健礼[1] 陈耀强[1] Xinmei Ding;Yanli Liang;Hailong Zhang;Ming Zhao;Jianli Wang;Yaoqiang Chen(Key Laboratory of Green Chemistry&Technology of the Ministry of Education,College of Chemistry,Sichuan University,Chengdu 610064,China;State Key Laboratory of Polymer Materials Engineering of China(Sichuan University),Polymer Research Institute of Sichuan University,Chengdu 610064,China;Department of Chemistry,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,Fujian Province,China)

机构地区：[1]四川大学化学学院,绿色化学与技术教育部重点实验室,成都610064 [2]四川大学高分子材料工程国家重点实验室,成都610064 [3]厦门大学化学与化学工程学院化学系,福建厦门361005

出　　处：《物理化学学报》2022年第4期65-75,共11页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(21972098)资助项目

摘　　要：Pt^(0)被认为是NO氧化的活性物种,而催化剂的制备方法对活性物种的含量起着决定性作用。本文采用非惰性气氛保护的改性醇还原-浸渍法(MARI)合成了高分散高Pt^(0)含量的1%(w,质量分数)Pt/SiO_(2)―Al_(2)O_(3)催化剂(MA-Pt/SA)。X射线粉末衍射(XRD)、CO-漫反射傅里叶变换红外吸收光谱(CO-DRIFTS)和透射电镜(TEM)表征证实在550℃焙烧3 h后催化剂的Pt颗粒仅有3.8 nm。同时,X射线光电子能谱(XPS)和H_(2)-程序升温还原(H_(2)-TPR)结果表明催化剂具有高Pt^(0)含量(60.3%)。模拟柴油车尾气气氛进行活性测试,并与传统浸渍法制备的1%(w)Pt/SiO_(2)―Al_(2)O_(3)催化剂(C-Pt/SA)对比,结果显示MA-Pt/SA具有优异的催化氧化性能,其NO最大转化率高达74%,比C-Pt/SA的NO转化率高了23%。经670℃高温老化15 h后,老化的MA-Pt/SA的NO转化率仍然高达69%。此外NO+O_(2)共吸附原位漫反射傅里叶变换红外吸收光谱(in situ DRIFTS of NO+O_(2) co-adsorption)表明高的Pt分散度和高Pt^(0)含量能够促进中间物种桥式硝酸盐的生成及分解,进而导致了优异的NO氧化活性。最后,利用同样方法将Pt的负载量降低至0.5%(w)制备催化剂,NO转化率仍达64%。这种制备方法能够获得低贵金属高性能的Pt基催化剂。Pt-based catalysts are widely used in diesel oxidation catalyst(DOC)units,primarily to oxidize the harmful HC,CO,and NO emissions.Notably,NO_(2) produced from NO oxidation is beneficial for lowtemperature activity in NH_(3)-SCR and promotes soot oxidation in diesel particulate filters(DPF).Thus,the conversion of NO is an important parameter for determining the performance of DOCs.Considering the increasingly stringent emission regulations and the economic effectiveness,preparation of low-cost and highly active Pt-based catalysts is indispensable.Generally,the Pt0 content is crucial as it is an active component of DOCs.Small Pt size is beneficial for improving the catalytic activity.In this study,we applied a modified alcohol reduction-impregnation(MARI)method to synthesize highly active 1%(w,mass fraction)Pt/SiO_(2)―Al_(2)O_(3)(denoted as MA-Pt/SA)catalyst.Meanwhile,using the conventional impregnation method,we prepared the Pt/SiO_(2)―Al_(2)O_(3) catalyst with the same Pt loading(denoted as C-Pt/SA)as a reference sample.X-ray photoelectron spectroscopy(XPS)and hydrogen temperature program reduction(H_(2)-TPR)analyses proved that the MARI method could produce Pt catalysts with higher Pt0 content.Pt0 content in MA-Pt/SA was~60.3%while that in C-Pt/SA was only~23.1%.X-ray diffraction(XRD),CO-diffuse reflectance infrared Fourier transform spectroscopy(CO-DRIFTS),and transmission electron microscopy(TEM)characterization confirmed that the Pt particle size is much smaller over MA-Pt/SA as compared to that over C-Pt/SA.Performance evaluation of MA-Pt/SA and C-Pt/SA was conducted in a simulated diesel atmosphere.The results showed that the maximum NO conversion into NO_(2) over MA-Pt/SA is 74%and 68%in the absence and presence of H_(2)O,respectively,which were much higher than those over C-Pt/SA(42%and 51%NO conversion with and without H_(2)O,respectively).Furthermore,the temperature for 30%NO conversion over MA-Pt/SA(218℃)markedly decreased as compared to that over C-Pt/SA(248℃),indicating the excellent low temp

关 键 词：柴油车氧化催化剂 改性的醇还原-浸渍法 NO氧化 高性能Pt基催化剂 低Pt含量 

分 类 号：O643[理学—物理化学]