| 年度 | 99 |
|---|---|
| 計劃編號 | NSC99-2221-E-239-026- |
| 研究學門 | 能源科技 |
| 中文計劃名稱 | 從氨裂解產氫之反應器性能研究(III) |
| 執行期限 | 2010-08-01～2011-07-31 |
| 主持人 | 陳炎洲 |
| 職稱 | |
| 預算 | 475000 |
| 中文摘要 | 可攜帶式電力在手機、筆記型電腦、數位相機等電子產品及車輛動力應用上有很好的潛力。質子交換膜燃料電池應用在可攜帶式電力主要問題是純氫氣的供應，為提高氫氣儲存量，現有純氫氣儲存技術包括高壓儲氫、低溫液化儲氫及金屬儲氫等，但這些技術均與商業化目標有一段距離。為克服質子交換膜燃料電池氫氣供應問題，常利用甲醇蒸汽重組反應來產生氫氣；但甲醇重組會產生CO毒化問題，需用水氣轉移反應、選擇性氧化等多個步驟純化氣體，且液態甲醇進入反應器前需先與水混和汽化，因此甲醇重組器的體積就相當大。 氨(NH3)的優點是氨很容易被液化和汽化(氨於25°C的飽和壓力Psat=152 kPa；氨在一大壓力的飽和溫度－32°C)、液化成本遠比氫液化低；於相同體積，氨的能量密度比液化氫高約30%。與甲醇相比，氨的優點為不排放溫室氣體CO2，沒有甲醇重組產氫反應時有CO毒化PEM燃料電池電極問題，氨裂解產氫的氫氣純化步驟比甲醇重組產氫簡單，氨的氫儲存容量(17.6 wt.%)和能量密度(3000 Wh/kg)均比甲醇高。加上氨在的通路已建立完善，因此用氨裂解產氫是一值得探討的主題。 氨裂解產氫反應常用觸媒有Ru, Rh, Ni, Pt, Fe,金屬氮化物等。觸媒載體有石墨碳,奈米碳管,活性碳, Al2O3, MgO, SiO2, TiO2, ZrO2等。促進劑(promoter)有Cs, Ba, Ca, KOH, KNO3, K2CO3, Mg等。甲醇蒸汽重組反應溫度約280°C，但過去氨裂解產氫反應溫度偏高(約400~650°C)；反應溫度高不利於應用在攜帶式燃料電池上。Christensen group [Catalysis Letters, 112, 2006]的研究成果是目前低溫氨裂解產氫文獻中最佳者，他們的實驗研究顯示Cs掺雜於Ru/C的loading量高時，氨裂解反應即使在低溫500K (227°C)時也有相當好的產氫性能提升，但相關問題例如觸媒/載體/促進劑間的loading最佳比例、觸媒及載體製備程序、觸媒分散均勻性、流道設計、觸媒塗佈方式、反應動力和熱質傳模式建立等仍有待進一步探討。 本計畫第一年度重點在於建構氨裂解產氫測試系統，觸媒/載體/促進劑製備程序、檢量線、數值模式等。為提升氨低溫裂解產氫性能，正在執行的第二年度計畫針對影響氨裂解產氫性能的重要參數，包括觸媒/載體/促進劑間的loading最佳比例及製備參數調控等問題進行探討和實驗量測各重要參數對氨裂解產氫量和轉換率的影響，並建立觸媒為packed bed時的反應器反應動力和熱質傳模式。現已有一篇將登於期刊Int. J. Hydrogen Energy (2010, Jan. Vol. 35, issue 2, p. 589-597)上。 因研究結果顯示觸媒直接塗在流道壁上(wall coated)時有氣體流動阻力小、熱阻小、製程簡單等優點，本計畫第三年度主要探討觸媒為wall coated時，針對影響氨裂解產氫性能的重要參數，包括觸媒/載體/促進劑間之合成醬料(ink)製備、觸媒醬料塗佈於流道壁面之製程及參數調控、流道設計等問題進行探討，並量測在較低反應溫度(250~400°C)及流量下的產氫量和轉換率。本計畫也將建立觸媒為wall coated時的反應器反應動力和熱傳/流力/質傳模式，以數值模擬反應器在不同反應溫度及流量的各化學成份(氫氣、氨氣、氮)濃度分佈、產氫量和氨轉換率，並與實驗結果比對，以改善反應器熱流設計，提高其產氫性能。 |
| 英文摘要 | The portable powers have a good potent in the application of cell phone, notebook, digital camera, and vehicle power. The main issue of PEM fuel cell for the portable power application is the pure hydrogen supply. The current hydrogen storage technologies, including H2 in high pressure, liquefied H2, and metal hydrate, still have a big gap for the commercialization. To resolve the hydrogen supply issue, it is often to use the methanol reforming to produce hydrogen. But the methanol reforming will produce CO poison problem. It needs water shift gas reaction and preferential oxidation to purify the hydrogen. The liquid methanol and water requires to be vaporized before they enter the reactor. Thus the size is rather large for the methanol reformer. The advantages of ammonia are that it is easy to be liquefied and vaporized, the liquefied cost of ammonia is much lower than that of hydrogen, and the energy density is 30% more than hydrogen at the same volume. As compared to methanol, the advantages of ammonia are, 1) It is free of CO2 production. 2) It doesn’t have CO poison issue for the fuel cell. 3) The steps to purify the gases are more simple than those of methanol. 4) Both the hydrogen content and energy density are higher than methanol. The infrastructure of ammonia is also well established. Thus it worthy for the study of hydrogen production from ammonia decomposition. The common catalysts used are Ru, Rh, Ni, Pt, Fe and metal nitrides. The nano-carbon tube, activated carbon, Al2O3, MgO, SiO2, TiO2, ZrO2 are often used as supports. The promoters have Ba, Ca, Cs, KOH, KNO3, K2CO3, Mg. The reaction temperature is about 280°C for methanol steam reforming. But the reaction temperature used for ammonia decomposition in the past was high as about 400~650°C, this is not good for the fuel cell application. The research by Christensen group showed that Ru/C catalysts promoted with high loading of Cs can significantly promote the performance of ammonia decomposition at temperatures as low as 500 K. But the related issues such as the catalyst/supports/promoter preparation and loading optimization, catalyst distribution uniformity, flow channel design, catalyst coating method, chemical kinetics and thermal-mass transport model are required further investigation. In the first year of this project, we focus on the establishment of ammonia decomposition test system, catalyst/supports/promoter fabrication process, verification of measurement results, and numerical model. To improve the hydrogen production performance in the second year project, the main parameters on the ammonia decomposition, including the optimal loading ratio of catalyst, support, and promoter, and the control of the fabrication parameters will be investigated. The chemical kinetics and thermal-mass transport models of the ammonia decomposition for the packed bed reactor will be established. The wall coated reactor (catalyst directly coating on the flow channel walls) have the advantages of lower flow resistance, lower thermal resistance, and simple fabrication process. In the third year of this proposal, the effects of the key parameters on the hydrogen production for the wall coated reactor will be investigated, including the ink preparation of catalyst, supports, and promoter mixture, fabrication and parameter control of catalyst coating on channel walls, flow channel design. The hydrogen production and the conversion rate will be measured at lower reaction temperatures (250~400°C) and flow rate. The chemical kinetics and thermal-mass transport models for the wall coated reactor will be established. The temperature and concentration distributions will be simulated numerically for different reaction temperatures and compared with the experiment results. The model can be used in the reactor design. |
| 中文關鍵字 | 氨裂解產氫,Ru/C 觸媒,Cs 促進劑,Cs/Ru 最佳比率 |
| 英文關鍵字 | Hydrogen production from NH3 decomposition,Ru/C catalyst,Cs promoter,optimal ratio of Cs/Ru |
| 檔案 | 從氨裂解產氫之反應器性能研究(III)(952,393 bytes) |