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研究生:陳映帆
研究生(外文):Kevin
論文名稱:氫氣對鈀金屬薄膜之滲透機制
論文名稱(外文):Hydrogen permeation of Palladium membrane
指導教授:雷敏宏雷敏宏引用關係郭修伯
學位類別:碩士
校院名稱:長庚大學
系所名稱:化工與材料工程研究所
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:2005
畢業學年度:93
語文別:中文
論文頁數:89
中文關鍵詞:鈀金屬薄膜氫氣
外文關鍵詞:permeationPalladium membrane
相關次數:
  • 被引用被引用:1
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鈀金屬對氫氣的特殊吸附能力,可以利用於純化氫氣;對於純氫氣的滲透效率相當良好,使混合氣氣體通過鈀膜管時,發揮最大效用,將Y氣體(非氫氣氣體)排除在外,使純化效率提升。
量測混合氣的滲透量時,傳統進料方式所使用的是將適當比例的混合氣通入反應器內,量測氫氣滲透膜管的流量,這方法呈現重要的缺點,鈀膜管長度的增加會大幅改變反應器內混合氣氫氣濃度。為克服因膜管長度改變氫氣濃度的問題,所以自行研發”固定濃度方式”,將氣體分壓計算後,在反應器內自行調配,可使鈀膜管外部混合氣的比例保持固定,減少因鈀膜管長度所造成的誤差。
在混合氣的環境之下,由Sievert’s Law可得知,氫氣分壓直接影響氫氣滲透鈀膜的能力,而本實驗觀察出一情況,滲透量的變化較接近[(PH2)1]1-[(PH2)2]1而非理論的[(PH2)1]1/2-[(PH2)2]1/2;而Y氣體的種類與濃度同樣的直接影響氫氣的滲透量。比較Y氣體為氮氣與二氧化碳對於氫氣滲透鈀膜能力的影響;氮氣影響較二氧化碳小的原因,在於二氧化碳與氫氣反應後產生一氧化碳影響著氫氣滲透量,因為該氣體的活性很強,會佔據鈀膜原本可吸附氫原子的活性基造成鈀膜的毒化,嚴重影響氫氣的滲透效率。
在氫氣純度方面,希望能利用鈀薄膜的純化分離,將濃度達99.99%以上。在實驗結果方面,氫氣濃度75%左右的混合氣確可直接純化至99.99%的濃度。而H2/CO2=95/5混合氣在7atm下則可以直接純化到99.9999%以上,並且發現氫氣分壓越高者,可純化出越高純度的氫氣;隨實驗壓力越高,同樣也可純化出越高的氫氣純度。
利用氫原子在觸媒表面上的溢滑現象(spillover)的發生,可利用MDC-3觸媒促進氫分子轉換成氫原子的數目,使氫氣滲透量增加。為確認溢滑現象對鈀膜滲透的影響,以MDC-3觸媒為依據,添加2%Pd金屬改質,進行化學吸附實驗,目的在觀察改質後的MDC-3觸媒對氫氣吸附量的影響。不過在本次實驗尚未觀察出滲透量增加的結果,其原因還須作確認。
Hydrogen permeation by Pd membrane is an excellent method for hydrogen purification .When a hydrogen mixtures, H2+Y was used as a feed for permeation, the hydrogen permeate was found to be perturbed by the nature of Y gas. The different Y gas causes different effects of hydrogen permeation.
Hydrogen permeance of a mixed gases, H2+Y, traditionally measure the hydrogen permeate while the desired composition of the gas mixture is passing through the length of the membrane surface. This method has a serious shortcoming because the composition of the gas mixture changes along the length of the membrane surface; therefore, the measured permeance is not from the original composition in the feed gas. To overcome this difficulty, we deviced a new method by maintaining a fixed composition in the feed gases while hydrogen permeated through the membrane.
Using the constant concentration method we had measured the permeances of H2+Y and H2+Y in various compositions under various operation pressures. By plotting the permeation flux against pressure difference, P1n-P2n (n=1/2 or 1), we found that n =1 gave better coordination than that with n=1/2. This is contract to the well known Sievert’s Law.
A pure hydrogen of 99.99% can be obtained by permeating a gas mixture of either 75%H2+25%N2 or 75%H2+25%CO2; the latter mixture is close to the product mixture of methanol steam reforming reaction. Surprisingly, an extremely high purity hydrogen of 99.99994% was obtained from 95%H2+5%N2 or 95%H2+5%CO2 permeation of Pd-membrane.
The effect of hydrogen spillover on the hydrogen chemisorption over 2%Pd/MDC-3 catalysts and on the hydrogen permeation through a Pd membrane were studied. The enhanced permeation of the Pd-membrane in the presence of catalyst was expected by the prior chemisorption of hydrogen molecules into hydrogen atoms on the large surface area MDC-3 catalyst; the chemisorbed hydrogen atoms then spillover to the Pd-membrane surface and permeated out of the system in higher flux. Unfortunate, our experimental result failed to sustain this expectation.
第一章 緒 論 1
第二章 文獻回顧 3
2.1鈀膜對氫氣的吸附特性 3
2.2氫氣在鈀薄膜之滲透機制 7
2.3混合氫氣鈀薄膜滲透機制 12
2.4氫氣的溢滑 ( Spillover ) 現象 14
第三章 實驗部分 18
3.1實驗藥品與實驗氣體 18
3.1-1實驗藥品 18
3.1-2實驗氣體 18
3.2觸媒製備步驟 19
3.3觸媒分析化學特性 21
3.3-1 BET比表面積測定儀 21
3.3-2 TPD程溫脫附 24
3.4鈀薄膜管氣體滲透實驗 26
3.5鈀薄膜管混合氣體滲透實驗 30
第四章 結果與討論 32
4.1鈀薄膜管混合氣體定濃度滲透實驗 32
4.1-1混合氣滲透實驗之新穎測試方法 33
4.1-2鈀膜管之基本性質測試 35
4.1-3影響滲透端流量之因素探討 42
4.1-4混合氣中二氧化碳比例之影響 48
4.1-5 滲透端純度分析 53
4.1-6鈀膜管旁之氣體純度分析 56
4.2利用Pd改質CuOZnO觸媒吸附特性分析 58
4.2-1 Pd改質CuOZnO觸媒的BET總表面積測定 58
4.2-2 CuOZnO觸媒與其改質觸媒之H2程溫脫附分析(TPD) 60
4.3鈀薄膜氫氣滲透率實驗 65
4.3-1未添加觸媒之鈀薄膜氫氣滲透實驗 65
4.3-2添加觸媒之鈀薄膜氫氣滲透實驗 67
第五章 結論 69
參考文獻 71
附 錄 75
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