4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

Iron And Chromium Incorporation To SBA-15 Mesoporous Structures Using Surface Sulfanation
SBA-15 mesoporous silica structure which also includes considerably high micro porosity, is formed as one dimensional hexagonal uniform channels with high surface area and high mechanical and hydrothermal stability. Its low catalytic activity can be improved with the modifications, during or after the synthesis. The hydrothermal incorporation of metals has the advantages of both the uniform distribution of metal species in the matrix and preservation of the ordered structure. Iron and chromium have been selected through their activities in the reaction of low carbon-chain organic compounds. Sulfanation which gives rise in increase the number of surface functional groups also used in the present study. The recipe suggested by Zhao et al. [1] was used in the synthesis of SBA-15 and iron and chromium incorporation to SBA-15 matrix was carried out hydrothermally by use of different metal/Si ratios. Pluronic 123, TEOS, FeSO4.7H2O and Cr2(SO4)3.12H2O were used as chemicals. The surface sulfonation was carried out by changing the synthesis acid as H2SO4 and use of the sulfate containing salts of the active metals with single and multiple modifications. Formation of well-ordered metal-SBA-15 catalysts were confirmed by several characterization techniques. XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy) characterization showed that the replacement of HCl with H2SO4 as synthesis acid does not impair observed sequence of regular pore structure of support however, the increase of pore wall thickness from 4.93 nm to 5.61 nm and again a decrease in the pore wall thickness was observed by metal loading. Metal incorporation resulted increases in the intensity of 100 diffraction confirmed the formation of long scale hexagonal arrays as also seen in TEM images. The textural properties obtained from nitrogen sorption data were found in harmony with them. Nitrogen adsorption data showed that micro- mesoporous structure were successfully synthesized with surface areas and pore dimensions reaching to 1130 m2/g and 6.5, respectively. It was concluded that surface functional groups and metal loading success increased by use of H2SO4 as synthesis acid. In FTIR (Fourier Transform Infrared Spectroscopy) spectrums, sulphate and sulphite groups were clearly observed by changing synthesis acid in addition to improvements in surface acidities measured by probe molecule doping. XPS (X-ray photo electron spectroscopy) method showed presence of the metal oxide bands and sulphur form in structure. It was also observed that the iron had +2, +3 and +4 atomicity and the chromium had +2, +3. It was observed from EDX (Energy dispersive X-ray spectroscopy) analysis that, the metal loadings found as much more lower than theoretically % 5 molar ratio loadings.
Keywords: SBA-15, hydrothermal synthesis, sulfanation, characterization
Cansu Musaoğlu, Suna Balcı