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Synthesis and characterization of Co-Pb/SBA-15 mesoporous catalysts

Akça, Burcu
Co and Pb are soft oxides, making them useful in partial oxidation catalysis. But it is difficult to prepare high surface area, nanometer size particles due to the low melting point of Pb. In the present study, SBA-15 samples are incorporated with Co and/or Pb at different weight loadings to provide a controlled geometry in nanometer scale via using direct synthesis method. The characterization of the synthesized samples was done by XRD, N2 adsorption isotherms, TEM images and XPS analysis. The increase in the metal loading in SBA-15 causes a decrease in the BET surface area due to the filling of pores with metal atoms. No characteristic peaks of metal oxide was observed up to 15 wt %Pb loading into SBA-15 in the large angle XRD pattern indicating that metal particles are dispersed in the SiO2 structure without accumulating and forming crystals. However, 20 wt%Pb loaded SBA-15 showed more appreciable characteristic peaks, indicating appreciable quantities of crystallites of metal oxide on the surface of silica. The introduction of high amount of cobalt and lead oxides to SBA-15 resulted in the loss of long range order of pores according to the low angle XRD patterns. The hexagonal structure of pores of SBA-15 was v confirmed by TEM images for all samples. XPS analysis indicated that binding energies of O 1s and Si 2p are almost similar in Co or Pb loaded samples, while mixed oxide loaded samples showed slightly higher binding energies which means the structure grows into a different type.