碩士 / 中原大學 / 化學研究所 / 106 / In this study, sodium hydroxide, sodium aluminate, ethanol, and water in different proportions were employed to synthesize aluminum hydroxide. Through XRD analysis, we found that peaks of aluminum hydroxide with gibbsit phase at 18.277° and 20.305° are evident with decreasing amounts of ethanol during their synthesises. The first peak at 18.277o in XRD becomes short and wide as the concentration of NaAlO2 solution increases. In the mean time, the characteristic peak of the bayerite phase located at 40.798° decreases and turns into a mixed phase of the gibbsite and bayerite phases. It shows that the crystal phase of aluminium hydroxide powder is changing.
The particle size of the powder with the appearance of a sheet structure will gradually become larger due to the decrease in the amount of ethanol, and the ability to catalyze the production of hydrogen tends to become slower.
After considering the comparison of ethanol and water consumption and catalytic hydrogen production, the optimal conditions for the study, Test-11 (sodium metaaluminate(g):ethanol(mL):water(mL)=5:100:50), were found in an ice bath. The synthesis time is only 1 hour. In the system of Al: Al(OH)3:H2O=1:1:200, 100% hydrogen production is completed in 105 minutes. The Arrhenius equation is used to calculate the activation energy for these self-made aluminum hydroxide. The activation energy of Al/water reaction will be reduced from 158 kJ/mole to 54.89 kJ/mole. Compared with those aluminum hydroxides studied in previous years, the catalytic performance is better. Besides a large number of processes, the yield is above 83%. Prior to breaking the study, the Bayerite phase aluminum hydroxide has an active site catalytic ideology. After reducing the synthesized Gibbsite phase aluminum hydroxide particles, the catalytic activity is higher. It is presumed that the active site is higher than the Bayerite phase. More aluminum hydroxide is a major discovery in the study.
In order to reduce the particle size of condition Test-11 Aluminium hydroxide powder, it was also attempted to reduce the particle size by synthesizing CTAB, PEG, and NaBH4 additives, to increase the contact surface with the aluminum powder so that the catalytic power of the powder could be stronger, due to the reaction the concentration of the solution is too high, the concentration of additive is too low in this solution, and there is no significant effect on the powder synthesis.
At the end of the study, the growth of the powder was understood to be essentially a mixed phase of Gibbsite and Bayerite in the presence of ethanol in the sodium metaaluminate solution. However, when the solution is too basic, the powder takes more time to precipitate. On the other hand, as soon as the powder precipitates, it will grow rapidly and form a thick and large sheet-like structure. At this time, the crystallinity is quite good. The high-strength Gibbsite phase characteristic peaks can be observed by XRD without the formation of the Bayerite phase aluminum hydroxide. With the increase of the amount of ethanol added, the powder is more and more easily precipitated, the precipitation time is faster, and finally a lamellar structure is formed. At this time, the crystallinity of the powder is still good, but the thickness is too thin, so the characteristic peak of the Gibbsite phase can be seen by XRD. Wide and short, while the Bayerite phase aluminum hydroxide is crystallinity, the characteristic peak intensity at this time is more obvious.
| Identifer | oai:union.ndltd.org:TW/106CYCU5065016 |
| Date | January 2018 |
| Creators | Shih-Chieh Hsu, 許仕傑 |
| Contributors | Hong-Wen Wang, 王宏文 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 163 |
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