Acta Phys. -Chim. Sin. ›› 2007, Vol. 23 ›› Issue (05): 641-646.doi: 10.1016/S1872-1508(07)60041-2

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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

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


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