物理化学学报 >> 2000, Vol. 16 >> Issue (04): 299-306.doi: 10.3866/PKU.WHXB20000403

研究论文 上一篇    下一篇

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

王伟, 林国栋, 张鸿斌, 熊智涛   

  1. 厦门大学化学化工学院,固体表面物理化学国家重点实验室,厦门 361005
  • 收稿日期:1999-04-23 修回日期:1999-09-13 发布日期:2000-04-15
  • 通讯作者: 张鸿斌

Ag/La0.6Sr0.4MnO3 Catalysts for Deep Oxidation of CH4 and CH3OH at Low Concentrations

Wang Wei, Lin Guo-Dong, Zhang Hong-Bin, Xiong Zhi-Tao   

  1. Department of Chemistry State Key Lab of Phys,Chem.for the Solid Surfaces,Xiamen University,Xiamen 361005
  • Received:1999-04-23 Revised:1999-09-13 Published:2000-04-15
  • Contact: Zhang Hong-Bin

摘要:

用柠檬酸溶胶-凝胶法制备钙钛矿型La0.6Sr0.4MnO3 氧化物, 并用Ag对其进行修饰, 制得Ag/La0.6Sr0.4MnO3 系列催化剂. 结果表明 ,6 %Ag/La0.6Sr0.4MnO3 催化剂上甲烷或甲醇氧化转化95 %时的反应温度T95 可低至735K(对CH4)或421K(对CH3OH); 适量Ag的负载修饰并不改变催化剂基质氧化物La0.6Sr0.4MnO3 的纳米级钙钛矿型结构; Ag的掺杂诱使催化剂中部分Mn3 +氧化为Mn4 +;Ag组分与钙钛矿型氧化物基质La0.6Sr0.4MnO3 表面的相互作用促使该催化剂对甲烷或甲醇的完全氧化表现出高而稳定的催化活性.

关键词: Ag,Ag/La0.6Sr0.4MnO3, 钙钛矿型氧化物基催化剂, CH4, CH3OH催化完全氧化

Abstract:

Ag-modified La0.6Sr0.4MnO3 catalysts were prepared and their catalytic performance for deep oxidation of CH4 and CH3OH at low concentrations were investigated. The results showed that the La0.6Sr0.4MnO3 host catalyst with the perovskite-type nano-crystallite structure displayed considerably high catalytic activity for deep oxidation of CH4 and CH3OH at low concentrations. Ag modification to the La0.6Sr0.4MnO3 host catalyst resulted in significant enhancement of the catalyst activity, making the T95 (the reaction temperature needed for conversion of 95%of CH4 or CH3OH) lowered down to 735K (for CH4) and 421K (for CH3OH) from 813 and 465 K over the Ag-free system under the reaction conditions:0.1MPa,CH4/O2/N2=2/12/86(molar ratio),GHSV=45000 h-1 and CH3OH/O2/N2= 0.2/1.0/98.8 (molar ratio),GHSV=58000 h-1,respectively.The carbon containing product was almost CO2 and the contents of HCHO and CO in the reaction exit gas were both under GC detectable limit in both cases.
The results of spectroscopic characterization indicated that modification by proper amount of Ag-dopant did not change the perovskite structure of the La0.6Sr0.4MnO3 host catalyst as a whole. Interaction of Ag-dopant with the surface of the host catalyst,La0.6Sr0.4MnO3,was in favor of high dispersion of the Ag component at the catalyst surface and led to the oxidation of part of the Mn3+species to Mn4+,resulting in an increase of amounts of the reducible Mnn+ species and a decrease of their reduction temperature. On the other hand, this interaction led also to enhancement of adsorption ability of the catalyst toward O2 at relatively low temperature. High activity of the Ag modified La0.6Sr0.4MnO3 catalyst for CH4 and CH3OH complete oxidation was closely related to high redox-activity of the catalyst and its prominent adsorption-activation ability to O2 at relatively low temperatures. 

Key words: Ag;Ag/La0.6Sr0.4MnO3, Perovskite oxide-based catalyst, CH4;CH3OH, Complete oxidation