MORPHOLOGICALLY CONTROLLED SYNTHESIS OF γ-Al2O3 USING REVERSE MICELLE TEMPLATE
<p align="justify"> Gamma alumina (γ-Al2O3) is one of the materials that widely used as a catalyst and catalyst support because it has large surface area and abundant acid sites. In its application as a catalyst, the conventional γ-Al2O3 has a lack of reactant acces...
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| Format: | Theses |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/26645 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | <p align="justify"> Gamma alumina (γ-Al2O3) is one of the materials that widely used as a catalyst and catalyst support because it has large surface area and abundant acid sites. In its application as a catalyst, the conventional γ-Al2O3 has a lack of reactant accessibility. This problem can be resolved by regulating its morphology. The γ-Al2O3 material with open surface structure can increase the reactant's accessibility to its active sites. In this research, we conducted the synthesis of γ-Al2O3 from NaAlO2 using a solvothermal method in reverse micelle template. Reverse micelle acts as nanoreactors that limit the growth of particles and regulate their size, shape, and morphology. The steps taken in this research were the optimation the compositions of substances that form stable emulsions, testing the type of emulsion and synthesis of materials using the stable emulsion. The emulsion preparation was carried out by adding a polar phase solution (water, NaAlO2, urea, surfactant) dropwise into a nonpolar phase (toluene, butanol) with stirring 800 rpm for 1 hour. The stable emulsion was then tested using a burn test and dilution test. Synthesis of materials was performed by reacting the stable emulsion using solvothermal method at 160 ° C for 24 hours. The obtained results were then filtered, washed using deionized water, ethanol and acetone, dried and calcined at 550 oC for 4 hours. The products of synthesis and calcination result were characterized by SEM, HRTEM, ATR-FTIR, XRD and TG / DTA. Parameters varied in this research were surfactant type, water, urea and surfactant composition, and synthesis time. The emulsion test results were showed that the surfactant forming reverse micelles are the CTAB surfactant and dehymuls PGPH, while emulsion using an SDS surfactant form a normal micelle. Based on the analysis using SEM, the morphological regularity of the synthesized material was obtained only in the synthesis using reverse micelle emulsion. The material obtained was composed by nanorods with ± 20-50 nm size that oriented to form spheres of ± 2 μm size. The morphology of this material did not change significantly after calcination, but the crystalline structure changed from γ-AlOOH (boehmite) to γ-Al2O3. In other variations of synthesis, the morphology of the material was not much different but has quite different in crystallinity and particle size distribution. In general, there are only three types of resulting morphology, namely aggregation of a nanorod, nanowire, and nanoplate. In addition, the synthesis material was showed that the morphological changes from nanowire aggregation to nanorod aggregation at longer synthesis time. Through measurements using HRTEM on nanorod aggregated morphological materials, it is seen that the resulting material has a pore on the surface to the center because the nanorods are not tightly arranged. Thermal properties of synthesized boehmite materials using TG / DTA was indicated that the material contains physically adsorbed water and an organic content. At a temperature of about 500 oC, there is a phase transformation into γ-Al2O3 which previously passes through the internal water dehydration. <p align="justify"> |
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