研究生: |
鍾國偉 |
---|---|
論文名稱: |
乙醇在Rh/Ce0.5Zr0.5O2(111)氧化金屬表面脫氫的可能反應機構 Computational Studies of Reaction Mechanisms of Dehydrogenation of Ethanol on the Rh/Ce0.5Zr0.5O2 (111) Surface |
指導教授: | 何嘉仁 |
學位類別: |
碩士 Master |
系所名稱: |
化學系 Department of Chemistry |
論文出版年: | 2007 |
畢業學年度: | 95 |
語文別: | 中文 |
論文頁數: | 71 |
中文關鍵詞: | 乙醇脫氫 、化學含氧量 |
論文種類: | 學術論文 |
相關次數: | 點閱:173 下載:2 |
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中文摘要
隨著化石燃料的日漸枯竭,人們正在找尋可以替代石油的能源來源。而氫氣(H2)是目前較佳的的料燃之一,將氫氣使用於內燃機引擎中,其燃燒產生的物質對環境是沒有污染性的。此外,氫氣也可以應用於H2/O2燃料電池的高效率發電方面,且具有相當的實用價值。乙醇是氫氣主要的來源之一,乙醇在合適的氧化物表面上時,加以合適的溫度,可以有絕佳的催化效果,而產生高效率的脫氫反應。在本文中,我們利用週期性的電子密度泛函理論的計算方法,探討乙醇在Rh/Ce0.5Zr0.5O2(111)表面上之可能的分解反應機構。結果發現,乙醇若以該分子的氧端吸附在Rh/CeO2(111)表極面的Ce上,比起其他表面原子而言(例如Rh與O原子),將有著較高的吸附能。是故乙醇首先將會以該氧端吸附在Rh/CeO2(111)表面的Ce上,而形成
CH3CH2O(H)–Ce(a),再藉由接續的脫氫反應(斷去O–H以及H2C–H)
,之後形成一個穩定環狀的中間物Rh–CH2CH2–Ce(a) (oxametallacycle)。再者,該中間物會先在α-碳上接連斷去兩個C–H鍵而形成吸附中間物Rh–CH2CO–Ce(a)。最後Rh–CH2CO–Ce(a)將藉由斷去C–C鍵結而形成Rh–CH2(a) + 4H(a) + CO(g)的產物,最後這些產物在高溫下再產生脫附反應,而形成CH4(g) + H2(g) + CO(g)。
Abstract
Hydrogen is considered a desirable fuel for several reasons, among which hydrogen is the least polluting fuel that one can use in an internal–combustion engine, and it can serve in a highly efficient hydrogen/oxygen fuel cell to produce electricity. As a result, we applied periodic density–functional theory (DFT) to investigate the dehydrogenation of ethanol on a Rh/Ce0.5Zr0.5O2(111) surface. Ethanol is calculated to have the greatest energy of adsorption when the oxygen atom of the molecule is adsorbed onto a Ce atom in the surface, relative to other surface atoms (Rh or O). Before forming an oxametallacyclic compound (Rh–CH2CH2O–Ce(a)), two hydrogen atoms from ethanol are first eliminated; the barriers for dissociation of the O-H and the β-carbon (CH2–H) hydrogens are calculated to be 15.2 and 26.9 kcal/mol, respectively. The dehydrogenation continues with loss of two hydrogens from the α-carbon, forming an intermediate species Rh–CH2CO–Ce(a), . Scission of the C–C bond occurs at this stage to form Rh–CH2(a) + 4H(a) + CO(g). At high temperatures, these adsorbates desorb to yield the final products CH4(g), H2(g) and CO(g).
參考文獻:
(1) Chou, H. L ; Jiang, J. C. The Chinese Chem. Soc., 2006, 64, No. 3, 301
(2) Taylor, K. C. Catal. Rev. Sci. Eng. 1995, 35, 457.
(3) Basic Research Needs for Vehicles of the Future; Eisenberger, P. M., Ed; Princeton Materials Institute: Princeton, NJ, 1995.
(4) Kaspar, J. ; Fornasiero, P.; Graziani, M. Catalysis Today .1999, 50, 285
(5) Taylor, K. C.; Proc. Catalytic and Automotive Pollution Control, Brussels, Belgium, (1986)
(6) Fisher, G. B.; Thesis, J. R.; Casarella, M. V.; Mahan, S. T.: SAE Tech. Pap. Ser., No. 931034 (1993)
(7) Shriver, D.F.; Atkins, P.W. Inorganic Chemistry thired edition.322
(8) Kenevey, K.; Valdivieso, F.; Soustelle, M.; Pijolat, M. Applied Catalysis B: Environmental 2001, 29, 93.
(9) Kim, Y.J.; Thevuthasan , S.; Shutthananadan , V.; Perkins, C.L.; McCready, D.E.; Herman, G.S.; Gao, Y. ; Tran, T.T.; Chambers, S.A.; Peden, C.H.F. Journal of Electron Spectroscopy and Related Phenomena. 2002,126 ,177
(10) Alan E.; Nelson. Kirk; Schulz, H. Applied Surface Science. 2003, 210, 206
(11) Wang , J.A. ; Lopez , T.; Bokhimi , X.; Novaro, O. Journal of Molecular Catalysis A: Chemical. 2005, 239, 249
(12) Diagne, C.; Idriss , H.; Kiennemann, A. Catalysis Communications. 2002, 3, 565
(13) Handbook of Chemistry and Physics, 76th ed., CRC Press,
Baton Rouge, FL, 1995.
(14) Kaspar, J.; Fornasiero, P.; Graziani, M. Catal. Today 1999, 50, 285.
(15) Madier, Y.; Descorme, C.; Le Govic, A. M.; Duprez, D. J. Phys. Chem. B 1999, 103, 10999
(16) Diagne , C.; Idriss , H.; Pearson , K.; Angel , M.; Kiennemann , A. C. R. Chimie. 2004, 7, 617
(17) Kresse, G.; Hafner, J. Phys. Rev. B .1993, 47, 558.
(18) Kresse, G.; Furthmuller, J. Comp. Mater. Sci. 1996, 6, 15.
(19) Kresse, G.; Hafner, J. Phys. Rev. B 1996, 54, 169.
(20) White, J. A.; Bird, D. M. Phys. Rev. B 1994, 50, 4954.
(21) Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K.A.; Pederson,
M. R.; Singh, D. J.; Fiolhais, C. Phys. Rev. B 1992, 46, 6671.
(22) (a)Blochl, P. E. Phys. Rev. B 1994, 50, 17953. (b) Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, 1758
(23) Alcala, R. ; Mavrikakis, M.; Dumesic, J. A. Journal of Catalysis. 2003, 218, 178
(24) Wyckoff, R.W.G. in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
(25) Chen, H.L.; Liu, S.H. ; Ho, J.J. J. Phys. Chem. B 2006, 110, 14816
(26) Idriss, H. Platinum Metals Rev., 2004, 48, (3), 105
(27) Prakash, D.; Vaidya, A. E. R. Chemical Engineering Journal. 2006, 117 , 39
(28) Duan, S.; Senkan, S. Ind. Eng. Chem. Res. 2005, 44, 6381
(29) Yee, A.; Morrison, S.J.; Idriss, H. Catalysis Today. 2000, 63, 327
(30) Sheng, P.Y.; Yee, A.; Bowmaker, G.A.; Idriss, H. Journal of Catalysis. 2002, 208, 393
(31)Ye, Q.; Gao, Q.; Zhang, X.R.; Xu, B.Q. Catalysis Communications. 2006, 7, 589
(32) Jones, G.S. ; Mavrikakis, M. ; Barteau, M.A.; Vohs, J.M. J. Am. Chem. Soc. 1998, 120, 3196
(33) Atherton, M. J.; Fawcett, J.; Holloway, J. H.; Hope, E. G.; Karacar, A.; Russell, D. R.; Saunders, G. C. J. Chem. Soc. Dalton Trans. 1996, 15, 3215.
(34) Atherton, M. J.; Fawcett, J.; Holloway, J. H.; Hope, E. G.; Martin, S. M.; Russell, D. R.; Saunders, G. C. J. Organomet. Chem. 1998, 555, 67.
(35) Breen, J.P.; Burch, R.; Coleman, H.M. Applied Catalysis B: Environmental. 2002, 39, 65
(36) Roh, H.S.; Platon, A.; Wang, Y.; King, D.L. Catalysis Letters. 2006, 110, Nos. 1–2
(37) Liguras, D.K.; Kondarides, D.I. ;Verykios, X.E. Applied Catalysis B: Environmental. 2003, 43, 345
(38) Ruettinger, W.; Liu, X.; Farrauto, R.J. Applied Catalysis B: Environmental. 2006, 65, 135
(39) Liu, Z.P. ;Jenkins, S.J. ; King, D.A. Physical review letters. PRL 94, 2005, 196102