鋁與水反應產氫的研究-雜質與催化劑的影響

The study of Hydrogen Generation from Aluminum/ water reaction – The influences of additives and catalysts

林佑祖(You-Zu Lin)

指導教授 ： 王宏文

中原大學/理學院/化學研究所/碩士(2019年)

https://doi.org/10.6840/cycu201900459

摘要

本篇研究是利用改良自製的氫氧化鋁以更進一步的強化該催化劑在鋁/水產氫反應中的影響力。首先，本實驗室已經發現以不同比例的乙醇、水、鋁酸鈉為原料可以合成出具備不同特性的氫氧化鋁。根據先前的實驗結果可知鋁酸鈉的濃度對合成出的氫氧化鋁有著顯著的影響力。因此第一部分為使用不同濃度的鋁酸鈉進行合成氫氧化鋁，並觀察其特性及其催化產氫能力。根據實驗結果可知隨著鋁酸鈉的濃度上升，氫氧化鋁會從純的Bayerite相變成Gibbsite 相與Bayerite相的混相，粉末的形狀也會隨著鋁酸鈉的濃度上升而逐漸的由顆粒狀轉為薄片狀。而晶相部分則是以No 5為轉捩點，鋁酸鈉濃度低於No 5時會是偏的Bayerite 相混相，而濃度高於No 5時則會轉變為偏Gibbsite 相的混相，催化能力能力是以濃度最高的No 7為最佳、濃度稍低的No 5次之。因此本研究選擇這兩種比例氫氧化鋁進行後續的改質研究。在實驗過程中還發現了乙醇及水的比例對產生的氫氧化鋁的影響，如果水的使用量明顯高於乙醇時會導致氫氧化鋁無法析出，即合成失敗。
而後分別以鐵、鎳、銅對No 5及No 7進行改質，並以不同的乾燥方式觀察會對其產生何種影響。分別經過SEM、XRD、產氫測試後可發現，適量的鐵對催化產氫是有正向的幫助的。不論是在No 5或No 7，這種影響不論何種乾燥方式皆存在。而鎳對催化能力都是正面的，並且不論使用量與乾燥方式，唯獨在強化程度上的存在差別。
最後銅對鋁與水產氫反應是有抑制作用的，且該抑制能力會隨著銅的使用量增加而上升，不論是No 5或No 7皆是如此。
在研究的最後，為了研究在大量產氫上可能會遇到的限制，本論文也對量大進行了測試。一、催化劑在多次反應時及在不同的反應環境下是否能保持其催化能力。在先前皆是在室溫下的單次反應，這裡選擇的是不控制溫度的連續3次反應。並且再加上攪拌與不攪拌做為比較。結果沒攪拌的3次反應都比有攪拌3次反應的快，且一次比一次快。原因是因為攪拌會影響氧化鋁層與催化劑的反應，並且攪拌將快速降低鋁與水反應核心的溫度，因為散熱效果變好。使用4g鋁:4g催化劑，可發現連續3次反應，一次比一次慢。推測這是因為鋁/水反應所產生的氫氧化鋁會妨礙自製氫氧化鋁與鋁反應物之間的接觸。

關鍵字

鋁水反應 ； 產氫

並列摘要

In this study，we use modified self-made aluminum hydroxide to further enhance the influence of the catalyst in the aluminum/water hydrogen production reaction. Firstly, the laboratory has found that different ratios of ethanol, water, sodium aluminate can be used as raw materials to synthesize aluminum hydroxide with different characteristics. According to the previous experimental results, it is known that the concentration of sodium aluminate has a significant influence on the synthesized aluminum hydroxide. Therefore, the first step is to synthesize aluminum hydroxide using different concentrations of sodium aluminate, and investigate its characteristics on the catalytic power for hydrogen generation in Al/water reaction. According to the experimental results, it is known that as the concentration of sodium aluminate increases, the aluminum hydroxide will change from pure Bayerite phase to mixed phase of Gibbsite phase and Bayerite phase. The shape of the powder will gradually change from granular to flake-like as the concentration of sodium aluminate increases. The turning point is based on No 5. When the sodium aluminate concentration is lower than No 5, the synthesized Al(OH)3 will be mix phase and Bayerite phase is higher . When the concentration is higher than No 5, it will be converted into a mixed phase and Gibbsite phase is higher. The best catalytic ability is the No. 7 and No. 5 is the second. Therefore, this two synthesized Al(OH)3 powders were selected for the subsequent modification studies. The effect of the ratio of ethanol and water on the produced aluminum hydroxide was also found. When the amount of water used is significantly higher than that of ethanol, aluminum hydroxide cannot be precipitated. That is, the synthesis will be failed.
Then, No 5 and No 7 were modified with iron, nickel and copper, respectively, and dried in different ways. After the hydrogen production, SEM and XRD tests, it can be found that a proper amount of iron has a positive catalytic effect on the hydrogen production, both No 5 or No 7, regardless of the drying method. Nickel is also positive for the catalytic performance, being only a slight difference in the enhancement, regardless of the amount used and the drying method. Finally, copper has an inhibitory effect on the hydrogen production of Al/water reaction. The inhibition ability increases as the amount of copper increases. And this is true for both No 5 or No 7.
At the final part of the study, in order to study the limitations of large amount of hydrogen generation, this study also do the tests using large amount of Al and catalysts. No.1, whether the catalyst can maintain its catalytic ability in multiple reactions and in different reaction environments. Previously, it was a single reaction at a room temperature. We have done a three consecutive reactions without controlling the temperature. Stirring and non-stirring as a control group. As a result, the three reactions without stirring were faster than those with stirring. The agitation will hinder the reaction of Al(OH)3 catalyst and Al2O3 passive layer. In addition, stirrig also cause rapid dissipation of thermal energy in the core site of Al/water reaction. It can be found that the reaction are slower than its preceding one when the 4g aluminum: 4g catalyst for a consecutive 3 reactions are used. This is considered to be that the aluminum hydroxide produced by the aluminum/water reaction interfered with the contact between the synthesized Al(OH)3 catalysts and the Al reactants.

並列關鍵字

hydrogen generation ； aluminum/ water reaction

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