| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 98 === Microspheres are synthesized at room temperature by utilizing C2Cl4 as a solvent, AlCl3 and PtH2Cl6 as precursors, and organic microspheres as a template in this research work. The composite Pt/Al2O3 microspheres with a hollow structure have been fabricated by thermal removal of the organic template at elevated temperatures. Microstructures, morphology, and specific surface area of the hollow microsphere are examined by field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analyses. The Pt loading is determined by inductively coupled plasma (ICP). In addition, hydrogenation catalysis has been carried out for the hollow Pt/Al2O3 microspheres, and is compared with the home-made solid Pt/Al2O3 catalyst.
Evidenced by the TEM and SEM results, uniform composite hollow microspheres consisting of Al2O3 shell and partial Pt particles embedded in the shell with a size of about 5 nm are obtained by the implantation process. Some Pt aggregation has been found on the surface of Al2O3. The Pt particles tend to attach one another on the surface of Al2O3 to form aggregates upon isothermal holding at elevated temperatures. As long as the Al2O3 shell does not transform into α-Al2O3 structure, the Pt particles distribute uniformly and are stable within the shell even after calcination to 1100℃.
The BET results show that Pt/Al2O3 composite hollow microspheres and pure Al2O3 hollow microsphere possess almost identical pore diameter. However, BET surface area of the Pt/Al2O3 was significantly lower than that of pure Al2O3, presumably due to the replacement of micropores by the Pt particles in composite case.
For the hydrogenation ability, the conversion efficiency of the hollow catalyst is three times higher than that of the solid one. After the hydrogenation reaction, the recycled solid and hollow microspheres both show Pt aggregation, but the hollow one is less obvious. More importantly, the recycled hollow microspheres preserve much larger ratio of activated areas than that of the solid one, demonstrating that the hollow composite catalysts may present a better chance to become re-usable.
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