MnO_(2)负载贵金属催化剂用于CO低温催化氧化的研究  

Study on MnO_(2)-supported noble metal catalysts for CO catalyticoxidation at low temperature

作　　者：许文建[1] 贾宏鹏[1,2] 陈金 李晓兰[1] XU Wenjian;JIA Hongpeng;CHEN Jin;LI Xiaolan(Institute of Urban Environment,Chinese Academy of Sciences,Xiamen 361021,China;University of Chinese Academy of Science,Beijing 100049,China)

机构地区：[1]中国科学院城市环境研究所,福建厦门361021 [2]中国科学院大学,北京100049

出　　处：《能源环境保护》2024年第4期189-197,共9页Energy Environmental Protection

基　　金：国家自然科学基金资助项目(22376193,22176187);省部级基金资助项目(2023T3070)。

摘　　要：利用双氧水驱动促进贵金属沉淀的方法在MnO_(2)上负载贵金属制备了一系列Pd/MnO_(2)、Ru/MnO_(2)、Ag/MnO_(2)、Pt/MnO_(2)催化剂。通过对比贵金属负载型催化剂(负载量3.0%)催化氧化CO的活性,得到如下结果:3.0%Pd/MnO_(2)>3.0%Ru/MnO_(2)>MnO_(2)>3.0%Ag/MnO_(2)>3.0%Pt/MnO_(2)。为了探究催化剂活性与材料结构特性之间的关系,分别使用球差电镜、XRD、Raman、H_(2)-TPR、O_(2)-TPD和XPS等表征技术对催化剂表面贵金属的粒径尺寸、晶体结构、缺陷结构、低温还原性、活性氧物种以及金属元素价态分布等物理化学特性进行了系统的表征和分析。研究发现,负载了Ag或Pt的催化剂仅仅改善了MnO_(2)的低温还原性,由于在CO催化氧化过程中催化剂表面的贵金属被快速还原,因此催化活性有所下降。相反地,负载了Pd或Ru的MnO_(2)催化剂在CO氧化反应中的活性显著提高,这是材料良好的低温还原性与表面化学吸附氧物种之间的协同促进作用所致。由于3.0%Pd/MnO_(2)具有更好的低温还原性和更多的表面化学吸附氧物种,其能够在10℃条件下完全催化氧化CO气体(浓度为1%CO/4%O_(2),GHSV=40000 mL/(g·h))。通过分析不同催化氧化反应过程,推测Pd/MnO_(2)催化氧化CO遵循Langmuir-Hinshelwood(L-H)机理。A series of MnO_(2)-supported noble metal catalysts(Pd/MnO_(2)、Ru/MnO_(2)、Ag/MnO_(2)and Pt/MnO_(2))with a noble metal loading of 3.0%were synthesized by redox precipitation.The catalytic oxidation ability of CO followed the order:3.0%Pd/MnO_(2)>3.0%Ru/MnO_(2)>MnO_(2)>3.0%Ag/MnO_(2)>3.0%Pt/MnO_(2).To understand the relationship between activity and textures of the catalysts,characterization techniques such as HRTEM/HAADF-STEM,XRD,Raman,H_(2)-TPR,O_(2)-TPD and XPS were employed to analyze the particle size of noble metals,crystal structure,defection structure,low-temperature reducibility,active oxygen species and elemental composition of the catalysts.The tests indicated that the support of Ag or Pt simply promoted the low-temperature reducibility of MnO_(2).However,Ag and Pt on the catalyst surface were rapidly reduced by CO,leading to partial deactivation.In contrast,supporting Pd or Ru not only enhanced low-temperature reducibility but also created abundant surface chemisorption oxygen species.The superior CO catalytic oxidation ability of 3.0%Pd/MnO_(2)and 3.0%Ru/MnO_(2)was attributed to the combined effect of low-temperature reducibility and abundant surface chemisorption oxygen species.The 3.0%Pd/MnO_(2)catalyst exhibited a lower reduction temperature and a greater abundance of surface chemisorption oxygen species,enabling complete oxidation of a 1%CO/4%O_(2)reaction gas mixture at 10℃(GHSV=40000 mL/(g·h)).It was speculated that the CO catalytic oxidation mechanism of 3.0%Pd/MnO_(2)followed the Langmuir-Hinshelwood(L-H)model.

关 键 词：Pd/MnO_(2) CO氧化 催化剂 低温还原性 化学吸附氧物种 

分 类 号：X505[环境科学与工程—环境工程] X701