STRUCTURAL PROPERTIES OF MANGANESE-FUNCTIONALIZED SILICA AEROGELSTatjana Kobal
, 2016, master's thesis
Abstract: Manganese-functionalized silica with interparticle mesoporosity and isolated Mn sites (Mn/Si = 0.01) is an excellent Fenton catalyst for water cleaning. However, there is a problem that needs to be solved, i.e., Mn leaching from the silica support during the reaction. The solution may lie in using aerogels as the silicate supports for the manganese. The goal of this master thesis is the synthesis and characterization of manganese-functionalized silica aerogels with different Mn/Si molar ratios and a determination of their structural properties. The emphasis is on the preparation of manganese-functionalized silica aerogels with isolated manganese sites.
Firstly, manganese-functionalized microporous and mesoporous silicates with a molar ratio Mn/Si = 0.005–0.02 were synthesized according to the literature and characterized as reference materials for manganese-functionalized aerogels. Manganese silicalite-1 (MnS-1) as a microporous zeolite-type silicate and manganese-functionalized silica (MnKIL-2) as a mesoporous silicate were prepared by the sol-gel process with a hydrothermal and solvothermal treatment, respectively. MnS-1 and MnKIL-2 with a molar ratio of Mn/Si ≤ 0.01 contain manganese as isolated sites in the silica framework and with a molar ratio of Mn/Si > 0.01 contain manganese as manganese oxides.
Secondly, manganese-functionalized aerogels (MnAEG) with a molar ratio Mn/Si = 0.005–0.02, were prepared according to the acid-base of the sol-gel polymerization of a tetraethylorthosilicate precursor, which is followed in combination with a supercritical drying using CO2. The prepared materials were characterized using the following techniques: X-ray powder diffraction (XRD), energy-dispersive X-ray elemental analysis (EDX), nitrogen physisorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results on manganese-functionalized aerogels (MnAEG) showed Mn oxide nanoparticles incorporated into the aerogel already at a low Mn concentration (Mn/Si = 0.005), which means that Mn aerogels are not promising silica supports for Mn catalysts applied for water cleaning, because they do not contain isolated Mn sites.
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Summary of found: ...which is followed in combination with a supercritical drying using CO2. The prepared materials were...
Keywords: : SiO2 aerogels, manganese-functionalized SiO2 aerogels, sol–gel process, CO2 supercritical drying
Published: 02.09.2016; Views: 5069; Downloads: 235
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