物理化学学报 >> 2007, Vol. 23 >> Issue (05): 641-646.doi: 10.1016/S1872-1508(07)60041-2

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多元介孔混合氧化物La-Mn-Ce-O催化剂的制备与表征

刘咏; 孟明; 姚金松; 查宇清   

  1. 天津大学化工学院催化科学与工程系, 天津 300072
  • 收稿日期:2006-10-08 修回日期:2006-12-11 发布日期:2007-04-28
  • 通讯作者: 孟明 E-mail:mengm@tju.edu.cn

Preparation and Characterization of the Multi-component Mesoporous Mixed Oxide La-Mn-Ce-O Catalysts

LIU Yong; MENG Ming; YAO Jin-Song; ZHA Yu-Qing   

  1. Department of Catalysis Science and Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China
  • Received:2006-10-08 Revised:2006-12-11 Published:2007-04-28
  • Contact: MENG Ming E-mail:mengm@tju.edu.cn

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摘要： 采用柠檬酸络合鄄有机模板剂分解法制备出具有不同(nLa+nMn)/(nLa+nMn+nCe)比、不同温度焙烧的La-Mn-Ce-O系列多元介孔混合氧化物催化剂, 并与传统共沉淀法制备的La-Mn-Ce-O催化剂进行比较. N2吸附和脱附结果表明, 采用模板剂法制得的样品具有较大的比表面积(高达103.5 m2·g-1)和较均匀的孔径分布(3.4-4.4 nm); 500 ℃焙烧样品的比表面积约为共沉淀法所制样品的三倍. 600 ℃焙烧后, 样品的孔径分布范围稍有加宽, 但仍保持介孔结构. XRD表征结果表明, Mn物种具有高度的分散性, XRD 难以检测, La-Ce和Mn-Ce可能部分形成了固溶体结构. XPS结果揭示, Mn-Ce间存在电子态的强相互作用, 出现了Mn 2p的震激峰, 这种相互作用促进了氧物种在Ce和Mn物种间的传递, 增强了样品的氧化还原性能, 震激峰最明显的样品具有最佳的氧化性能. H2-TPR结果表明, 采用柠檬酸络合鄄有机模板剂分解法制备的催化剂中, 锰氧化物更容易被还原, Mn—O 键的活动度与CO氧化活性密切相关. 活性评价结果表明, 500 ℃焙烧的(nLa+nMn)/(nLa+nMn+nCe)为0.5的样品, 起燃温度比传统共沉淀法制得的样品降低了50 ℃左右, 并表现出较高的热稳定性.

关键词: 多元介孔催化剂, 制备, 柠檬酸络合, 有机模板剂, 结构表征

Abstract: A series of mesoporous multicomponent mixed oxide catalysts La-Mn-Ce-O with various (nLa+nMn)/(nLa+nMn+nCe) ratios were prepared by citric acid complexation-organic template decomposition (CAC-OTD) method. For comparison, the sample with the same composition was also prepared by conventional coprecipitation method. The results of N2 adsorption/desorption showed that the samples prepared by CAC-OTD method possessed relatively large specific surface area and uniformpore diameter distribution (3.4-4.4 nm). The results of X-ray diffraction (XRD) identified the formation of La-Ce and Mn-Ce solid solution. No Mn species were detected by XRD. The results of X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic state interaction betweenMn and Ce species, resulting in the formation of Mn 2p shake-up peak. Such interaction enhanced the transfer of oxygen species from Ce to Mn oxide and therefore increased the redox activity of the samples. The sample with the strongest shake-up peak showed the highest oxidation activity. The results of temperature programmed reduction (TPR) showed that the manganese species in the samples prepared by using CAC-OTD method were easier to be reduced, which was relevant to the oxidation activity of the catalysts. The results of activity evaluation showed that the light-off temperature of the LMC(0.5)-500 sample was about 50 ℃ lower than that of the sample prepared by using coprecipitation method. The samples prepared by using CAC-OTDmethod showed good thermal stability.

Key words: Multi-component mesoporous catalyst, Preparation, Citric acid complexation, Organic template, Structural characterization

MSC2000: 

  • O643