文献类型：期刊文献

中文题名：析出型LaFe_(0.9)Ru_(0.1)O_(3)钙钛矿催化剂在丙烷催化氧化反应中的自活化现象

英文题名：Unveiling the self‐activation of exsolved LaFe_(0.9)Ru_(0.1)O_(3) perovskiteduring the catalytic total oxidation of propane

作者：王宇[1,2];Jaime Gallego[2,3];汪炜[1,2];Phillip Timmer[2];丁敏[1];Alexander Spriewald Luciano[2];Tim Weber[2];Lorena Glatthaar[2];郭杨龙[1];Bernd M.Smarsly[2];Herbert Over[2]

机构：[1]华东理工大学化学与分子工程学院,工业催化研究所,绿色化工与工业催化全国重点实验室,上海200237;[2]尤斯图斯-李比希大学物理化学研究所,吉森,德国;[3]尤斯图斯-李比希大学材料研究中心,吉森,德国

年份：2023

卷号：54

期号：11

起止页码：250

中文期刊名：Chinese Journal of Catalysis

外文期刊名：催化学报（英文）

收录：CSTPCD;;EI(收录号：20234815119892);Scopus;WOS:【SCI-EXPANDED(收录号:WOS:001124386900001)】；CSCD:【CSCD2023_2024】；

基金：Yu Wang acknowledges the China Scholarship Council for the Joint-Ph.D. program with the Institute of Physical Chemistry of the Justus-Liebig-University Giessen. We acknowledge support from the Center for Materials Research at the JLU. H.O. and L.G. acknowledge funding by the German Research Foundation (DFG, Deutsche Forschungsgemeinschaft - 493681475).

语种：中文

中文关键词：LaFe_(0.9)Ru_(0.1)O_(3)钙钛矿;溶出;氧化还原预处理;RuO_(2);丙烷完全催化氧化

外文关键词：LaFe_(0.9)Ru_(0.1)O_(3)perovskite;Exsolution;Redox treatment;RuO_(2);Catalytic total oxidation of propane

摘要：负载型贵金属催化剂在能源转化和环境污染控制等领域有广泛应用.相对于采用传统方法制备负载型贵金属催化剂,还原析出策略在控制贵金属的粒径,增强贵金属与载体相互作用方面具有独特的优势.但是在高温还原气氛下,贵金属析出的同时往往伴随着母体结构中其它元素的析出,这会对催化剂的性能产生较大影响.因此,理解催化剂在还原气氛下以及后续反应条件下的结构演变,对于催化剂的设计及制备具有重要意义.本文通过800℃还原Ru掺杂的LaFe_(0.9)Ru_(0.1)O_(3)(LFRO)钙钛矿前驱体制备了贵金属析出的LFRO催化剂(LFRO800R),并用于丙烷催化氧化反应.活性测试结果表明,析出Ru催化剂的丙烷氧化性能远远低于原始的LFRO.当第一次反应结束,催化剂床层温度降至室温后再次评价其性能,LFRO 800R催化剂会发生“自活化”现象,在210℃下催化丙烷反应速率达到了22.3 molCO_(2)·h^(-1)·kgcat^(-1),是该温度下贵金属未析出LFRO催化剂的5倍,反应10 h后仍表现出较高的稳定性.为进一步研究LFRO800R在丙烷氧化反应中发生“自活化”的原因,在不同温度对LFRO 800R进行氧化处理,发现经过400℃氧化后得到的LFRO800R400O表现出最佳的丙烷催化活性.采用高分辨透射电镜、能量散射谱、漫反射红外傅立叶变换光谱、扫描电镜、X射线衍射、Raman光谱和X射线光电子能谱等方法对催化剂进行了表征,结果表明,经过800℃还原预处理,伴随着Ru从LFRO钙钛矿结构的体相中析出到表面,钙钛矿A位元素La也会析出并在RuFe(Ru占据主导)颗粒表面形成一层LaO_(x)覆盖层,阻碍了反应物分子在活性位点Ru上的吸附与活化,导致LFRO 800R在丙烷完全氧化反应中的低温区间表现出失活的现象.而在400℃的氧化气氛处理下,该LaO_(x)包裹层会从析出颗粒的表面完全去除,伴随着少部分界面处的Ru重新进入钙钛矿结构,大量有活性的Ru物种被暴露出来,因此催化剂表现出较好的丙烷催化氧化性能.活化后的LFRO800R400O催化剂中Ru的平均粒径为12 nm,远远小于负载型Ru/LFO800R400O催化剂的34 nm,说明还原析出策略在控制贵金属粒径方面有优势.综上,本文揭示了还原析出策略制备的Ru基钙钛矿催化剂的失活原因以及后续的氧化气氛中“自活化”的原因,为理性设计与制备高效的析出型贵金属催化剂提供了借鉴.
The exsolution process enables to produce and control the formation of stable and catalyticallyactive nano particles via reductive extraction of uniformly incorporated precious metal ions from asolid oxide solution. Here we consider the simple and stable perovskite LaFeO_(3) (LFO) where 10% ofFe on B sites are substituted by ruthenium (LFRO). Hydrogen reduction of LFRO at 800 °C leads tothe formation of socketed ruthenium particles whose low-temperature activity in the total propaneoxidation reaction at 210 °C is substantially lower than that of the original LFRO. Upon increasingthe reaction temperature once to 400 °C, the exsolved catalyst undergoes self-activation so that theactivity at 210 °C turns out to be five times higher than that of the original LFRO. High-resolutiontransmission electron microscopy and nanometer-resolved element mapping, together with averagingcharacterization methods, including X-ray diffraction and X-ray photoelectron spectroscopy,Raman spectroscopy, and diffuse infrared spectroscopy, unveil that after reduction at 800 °C theexsolved Ru particles are slightly alloyed with Fe and encapsulated by an inert and protecting LaOxlayer. Mild oxidative treatment at 400 °C leads to the removal of the conforming LaOx layer, whilethe uncovered RuFe alloy particle transforms to catalytically active oxidic Ru species, with no indicationof a separate FeOx phase. We exemplify with our case study of LaFe_(0.9)Ru_(0.1)O_(3) that carefulredox treatment enables to control the exsolution process and to avoid deactivation. This may be ofimportance for the whole class of exsolvable materials.