Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/28117
標題: 奈米氧化鐵參雜銅錳對於催化氧化乙烯之動力及機制探討
The Kinetic and Mechanism of Mixing Cu-Mn on the Catalytic Oxidation of Ethylene over Nano-Sized Iron Oxide
作者: 廖崇億
Liao, Chong-Yi
關鍵字: Ethylene;乙烯;Metal Oxides Catalyst;Catalytic Oxidation and kinetic model and XAS;金屬氧化物觸媒;催化氧化;反應動力模式;X光吸收光譜
出版社: 土壤環境科學系所
引用: 中文 吳立偉,以MnO/Fe2O3觸媒焚化處理甲硫醇與乙硫醇之研究,國立成功大學環境工程研究所碩士論文,1995。 吳寶旺,二甲苯在鈀,鈀-鉑觸媒之催化氧化研究,國立中正大學化學工程研究所碩士論文,2001。 郝光輝,以MnO/Fe2O3觸媒焚化處理甲基硫類之研究,國立成功大學環境工程研究所碩士論文,1995。 陳均衡,以MnO/Fe2O3觸媒焚化處理丙烯之研究,國立成功大學環境工程研究所碩士論文,1996。 曾庭科,以MnO/Fe2O3觸媒焚化處理苯乙烯之研究,國立成功大學環境工程研究所碩士論文,1997。 蔡金進,以觸媒氧化含氯烯類化合物之研究,國立中山大學環境工程研究所碩士論文,2003。 楊文毅, 鈀觸媒氧化焚化廢氣中有機物之研究,國立中興大學環境工程研究所碩士論文,1999。 楊玉霞、徐賢倫、孫鯤鵬,CuFeOx催化劑上乙醇催化燃燒,天然氣化工,05期第30卷。 廖偉筑,結合觸媒氧化及高級氧化以處理含氯揮發性有機物之研究,臺灣大學環境工程學研究所碩士論文,2006。 英文 Abdel Halim, K.S., M.H. Khedr, M.I. Nasr, and A.M. El-Mansy. 2006. Factors affecting CO oxidation over nanosized Fe2O3. Materials Research Bulletin In Press, Corrected Proof. ABE, K., and A.E. WATADA. 1991. Ethylene Absorbent to Maintain Quality of Lightly Processed Fruits and Vegetables. Journal of food science. Alvarez-Galvan, M.C., B. Pawelec, V.A. de la Pena O''Shea, J.L.G. Fierro, and P.L.Arias. 2004. Formaldehyde/methanol combustion on alumina-supportedmanganese-palladium oxide catalyst. Applied Catalysis B: Environmental 51:83. Baetzold, R.C., and H. Yang. 2003. Computational Study on Surface Structure and Crystal Morphology of -Fe2O3: Toward Deterministic Synthesis of Nanocrystals. J. Phys. Chem. B 107:14357-14364. Bailen, G., F. Guillen, S. Castillo, M. Serrano, D. Valero, and D. Martinez-Romero.2006. Use of activated carbon inside modified atmosphere packages tomaintain tomato fruit quality during cold storage. Journal Of Agricultural And Food Chemistry 54:2229-2235. Baldi, M., E. Finocchio, F. Milella, and G. Busca. 1998a. Catalytic combustion of C3 hydrocarbons and oxygenates over Mn3O4. Applied Catalysis B: Environmental 16:43. Baldi, M., E. Finocchio, C. Pistarino, and G. Busca. 1998b. Evaluation of the mechanism of the oxy-dehydrogenation of propane over manganese oxide. Applied Catalysis A-General 173:61-74. Beaudry, R.M. 1999. Effect of O2 and CO2 partial pressure on selected phenomena affecting fruit and vegetable quality. Postharvest Biology and Technology 15:293. Belin, T., N. Guigue-Millot, T. Caillot, D. Aymes, and J.C. Niepce. 2002. Influence of Grain Size, Oxygen Stoichiometry, and Synthesis Conditions on the [gamma]-Fe2O3 Vacancies Ordering and Lattice Parameters. Journal of Solid State Chemistry 163:459. Boccuzzi, F., A. Chiorino, M. Manzoli, D. Andreeva, and T. Tabakova. 1999. FTIR study of the low-temperature water-gas shift reaction on Au/Fe2O3 and Au/TiO2 catalysts. Journal Of Catalysis 188:176-185. Cao, J.-L., Y. Wang, X.-L. Yu, S.-R. Wang, S.-H. Wu, and Z.-Y. Yuan. 2007. Mesoporous CuO-Fe2O3 Composite Catalysts for Low-Temperature Carbon Monoxide Oxidation. Applied Catalysis B: Environmental In Press, Accepted Manuscript. Cha, H.G., C.W. Kim, Y.H. Kim, M.H. Jung, E.S. Ji, B.K. Das, J.C. Kim, and Y.S.Kang. 2009. Preparation and characterization of [alpha]-Fe2O3 nanorod-thin film by metal-organic chemical vapor deposition. Thin Solid Films 517:1853. Chen, D., and Z. Wu. 2006. A theoretical and experimental XAS study of monolayer dispersive supported CuO/[gamma]-Al2O3 catalysts. Radiation Physics and Chemistry 75:1921. Chen, Y., X.H. Li, P.L. Wu, W. Li, and X.Y. Zhang. 2007. Enhancement of structural stability of nanosized amorphous Fe2O3 powders by surface modification. Materials Letters 61:1223. Cheng, T., Z. Fang, Q. Hu, K. Han, X. Yang, and Y. Zhang. 2007. Low-temperature CO oxidation over CuO/Fe2O3 catalysts. Catalysis Communications 8:1167. Choi, B.U., D.K. Choi, Y.W. Lee, B.K. Lee, and S.H. Kim. 2003. Adsorption equilibria of methane, ethane, ethylene, nitrogen, and hydrogen onto activated carbon. Journal Of Chemical And Engineering Data 48:603-607. Chu, H., G.H. Hao, and T.K. Tseng. 2003. Laboratory study of poisoning of a MnO/Fe2O3 catalyst by dimethyl sulfide and dimethyl disulfide. Journal of Hazardous Materials 100:301. Conte, J., A. El Blidi, L. Rigal, and L. Torres. 1992. Ethylene removal in fruit storage rooms: A catalytic oxidation reactor at low temperature. Journal of Food Engineering 15:313. Cordi, E.M., and J.L. Falconer. 1996a. Decomposition and oxidation of CH313 CH2OH on Al2O3, Pd/Al2O3, and PdO/Al2O3 catalysts. Catalysis Letters 38:45-51. Cordi, E.M., and J.L. Falconer. 1996b. Oxidation of volatile organic compounds on Al2O3, Pd/Al2O3, and PdO/Al2O3 catalysts. Journal Of Catalysis 162:104-117. Cordi, E.M., P.J. O''Neill, and J.L. Falconer. 1997. Transient oxidation of volatile organic compounds on a CuO/Al2O3 catalyst. Applied Catalysis B-Environmental 14:23-36. El-Shobaky, H.G., and Y.M. Fahmy. 2006. Cordierite as catalyst support for nanocrystalline CuO/Fe2O3 system. Materials Research Bulletin 41:1701. Figueroa, S.J.A., F.G. Requejo, E.J. Lede, L. Lamaita, M.A. Peluso, and J.E. Sambeth. 2005. XANES study of electronic and structural nature of Mn-sites in manganese oxides with catalytic properties. Catalysis Today 107-108:849. Fritsch, S., J. Sarrias, A. Rousset, and G.U. Kulkarni. 1998. Low-temperature oxidation of Mn3O4 hausmannite. Materials Research Bulletin 33:1185. Gomes, J.A., M.H. Sousa, G.J. da Silva, F.A. Tourinho, J. Mestnik-Filho, R. Itri, G.d.M. Azevedo, and J. Depeyrot. 2006. Cation distribution in copper ferrite nanoparticles of ferrofluids: A synchrotron XRD and EXAFS investigation. Journal of Magnetism and Magnetic Materials 300:e213. Graham, T.K., J.N. Veenstra, and P.R. Armstrong. 1998. Ethylene removal in fruit and vegetable storages using a plasma reactor. Transactions Of The Asae 41:1767-1773. Halasz, J., M. Hodos, I. Hannus, G. Tasi, and I. Kiricsi. 2005. Catalytic detoxification of C2-chlorohydrocarbons over iron-containing oxide and zeolite catalysts. Colloids and Surfaces A: Physicochemical and Engineering Aspects 265:171. Haruta, M., S. Tsubota, T. Kobayashi, H. Kageyama, M.J. Genet, and B. Delmon. 1993. Low-Temperature Oxidation of CO over Gold Supported on TiO2, [alpha]-Fe2O3, and Co3O4. Journal of Catalysis 144:175. Heisig, C., W. Zhang, and S.T. Oyama. 1997. Decomposition of ozone using carbon-supported metal oxide catalysts. Applied Catalysis B: Environmental 14:117. Hermia, J., and S. Vigneron. 1993. Catalytic Incineration For Odor Abatement And Voc Destruction. Catalysis Today 17:349-358. Herrera, F., A. Lopez, G. Mascolo, P. Albers, and J. Kiwi. 2001. Catalytic combustion of Orange II on hematite: Surface species responsible for the dye degradation. Applied Catalysis B: Environmental 29:147. Herrero, E., M.V. Cabanas, M. Vallet-Regi, J.L. Martinez, and J.M. Gonzalez-Calbet. 1997. Influence of synthesis conditions on the [gamma]-Fe2O3 properties. Solid State Ionics 101-103:213. Hsu, H.H., H.P. Wang, C.Y. Chen, C.J.G. Jou, and Y.-L. Wei. 2007. Chemical structure of zinc in the Fe/ZnO thin films during sensing of ethanol. Journal of Electron Spectroscopy and Related Phenomena 156-158:344. Hu, R., L. Xie, S. Ding, J. Hou, Y. Cheng, and D. Wang. 2008. CO oxidation and oxygen-assisted CO adsorption/desorption on Ag/MnOx catalysts. Catalysis Today 131:513. Jacob A. Moulijn, and P.W.N.M.V. Leeuwen. 1993. Catalysis: an integrated approach to homogeneous, heterogeneous and industrial catalysis Baker & Taylor Books. Ji, W., Y. Chen, S. Shen, S. Li, and H. Wang. 1996. FTIR study of adsorption of CO, NO and C2H4 and reaction of CO + H2 on the well-dispersed FeOx/[gamma]-Al2O3 and FeOx/TiO2(a) catalysts. Applied Surface Science 99:151. Ko, M.K., and H. Frei. 2004. Millisecond FT-IR Spectroscopy of Surface Intermediates of C2H4 Hydrogenation over Pt/Al2O3 Catalyst under Reaction Conditions. J. Phys. Chem. B 108:1805-1808. Kramer, M., T. Schmidt, K. Stowe, and W.F. Maier. 2006. Structural and catalytic aspects of sol-gel derived copper manganese oxides as low-temperature CO oxidation catalyst. Applied Catalysis A: General 302:257. Li, P., D.E. Miser, S. Rabiei, R.T. Yadav, and M.R. Hajaligol. 2003. The removal of carbon monoxide by iron oxide nanoparticles. Applied Catalysis B: Environmental 43:151. Li, W.B., W.B. Chu, M. Zhuang, and J. Hua. 2004. Catalytic oxidation of toluene on Mn-containing mixed oxides prepared in reverse microemulsions. Catalysis Today 93-95:205. Liu, H., Y. Wei, and Y. Sun. 2005. The Formation of hematite from ferrihydrite using Fe(II) as a catalyst. Journal of Molecular Catalysis A: Chemical 226:135. Liu, T., L. Guo, Y. Tao, T.D. Hu, Y.N. Xie, and J. Zhang. 1999. Bondlength alternation of nanoparticles Fe2O3 coated with organic surfactants probed by EXAFS. Nanostructured Materials 11:1329. Liu, Y., M. Luo, Z. Wei, Q. Xin, P. Ying, and C. Li. 2001. Catalytic oxidation of chlorobenzene on supported manganese oxide catalysts. Applied Catalysis B: Environmental 29:61. Maneerat, C., and Y. Hayata. 2006. Efficiency of TiO2 photocatalytic reaction on delay of fruit ripening and removal of off-flavors from the fruit storage atmosphere. Transactions Of The Asabe 49:833-837. Maneerat, C., Y. Hayata, N. Egashira, K. Sakamoto, Z. Hamai, and M. Kuroyanagi. 2003. Photocatalytic reaction of TiO2 to decompose ethylene in fruit and vegetable storage. Transactions Of The Asae 46:725-730. Marco, J.F., J.R. Gancedo, H. Nguyen Cong, M. del Canto, and J.L. Gautier. 2006. Characterization of Cu1.4Mn1.6O4/PPy composite electrodes. Solid State Ionics 177:1381. Martinez-Romero, D., E. Dupille, F. Guillen, J.M. Valverde, M. Serrano, and D. Valero. 2003. 1-Methylcyclopropene increases storability and shelf life in climacteric and nonclimacteric plums. Journal Of gricultural And Food Chemistry 51:4680-4686. Minico, S., S. Scire, C. Crisafulli, and S. Galvagno. 2001. Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide. Applied Catalysis B: Environmental 34:277. Minico, S., S. Scire, C. Crisafulli, A.M. Visco, and S. Galvagno. 1997. FT-IR study of Au/Fe2O3 catalysts for CO oxidation at low temperature. Catalysis Letters 47:273-276. Minico, S., S. Scire, C. Crisafulli, R. Maggiore, and S. Galvagno. 2000. Catalytic combustion of volatile organic compounds on gold/iron oxide catalysts. Applied Catalysis B-Environmental 28:245-251. Miranda, B., E. Diaz, S. Ordonez, A. Vega, and F.V. Diez. 2007. Oxidation of trichloroethene over metal oxide catalysts: Kinetic studies and correlation with adsorption properties. Chemosphere 66:1706. Morales, M.R., B.P. Barbero, and L.E. Cadus. 2006. Total oxidation of ethanol and propane over Mn-Cu mixed oxide catalysts. Applied Catalysis B: Environmental 67:229. Morales, M.R., B.P. Barbero, and L.E. Cadus. 2007. Evaluation and characterization of Mn-Cu mixed oxide catalysts for ethanol total oxidation: Influence of copper content. Fuel In Press, Corrected Proof:20. Munteanu, G., L. Ilieva, and D. Andreeva. 1997. Kinetic parameters obtained from TPR data for alpha-Fe2O3 and Au/alpha-Fe2O3 systems. Thermochimica Acta 291:171-177. Ordóñez, S., L. Bello, H. Sastre, R. Rosal, and D.F. V. 2002. Kinetics of the deep oxidation of benzene, toluene, n-hexane and their binary mixtures over a platinum on [gamma]-alumina catalyst. Applied Catalysis B: Environmental 38:139. PalDey, S., S. Gedevanishvili, W. Zhang, and F. Rasouli. 2005. Evaluation of a spinel based pigment system as a CO xidation catalyst. Applied Catalysis B: Environmental 56:241. Parida, K.M., and A. Samal. 1999. Catalytic combustion of volatile organic compounds on Indian Ocean manganese nodules. Applied Catalysis A: General 182:249. Petit, F., J. D r, M. Lenglet, and B. Hannoyer. 1993. Thermal behaviour of gamma manganese dioxide: I. Structural evolution. Materials Research Bulletin 28:959. Picasso Escobar, G., A. Quintilla Beroy, M.P. Pina Iritia, and J. Herguido Huerta. 2004. Kinetic study of the combustion of methyl-ethyl ketone over [alpha]-hematite catalyst. Chemical Engineering Journal 102:107. Picasso, G., A. Quintilla, M.P. Pina, and J. Herguido. 2003. Total combustion of methyl-ethyl ketone over Fe2O3 based catalytic membrane reactors. Applied Catalysis B: Environmental 46:133. Porat, R., B. Weiss, L. Cohen, A. Daus, R. Goren, and S. Droby. 1999. Effects of ethylene and 1-methylcyclopropene on the postharvest qualities of `Shamouti'' oranges. Postharvest Biology and Technology 15:155. Ramesh, K., L. Chen, F. Chen, Y. Liu, Z. Wang, and Y.-F. Han. 2008. Re-investigating the CO oxidation mechanism over unsupported MnO, Mn2O3 and MnO2 catalysts. Catalysis Today 131:477. Reddy, B.V., F. Rasouli, M.R. Hajaligol, and S.N. Khanna. 2004a. Novel mechanism for oxidation of CO by Fe2O3 clusters. Fuel 83:1537. Reddy, B.V., F. Rasouli, M.R. Hajaligol, and S.N. Khanna. 2004b. Novel pathway for CO oxidation on a Fe2O3 cluster. Chemical Physics Letters 384:242. Saltveit, M.E. 1999. Effect of ethylene on quality of fresh fruits and vegetables. Postharvest Biology and Technology 15:279. Scire, S., S. Minico, C. Crisafulli, and S. Galvagno. 2001. Catalytic combustion of volatile organic compounds over group IB metal catalysts on Fe2O3. Catalysis Communications 2:229. Sekizawa, K., S.-i. Yano, K. Eguchi, and H. Arai. 1998. Selective removal of CO in methanol reformed gas over Cu-supported mixed metal oxides. Applied Catalysis A: General 169:291. Shaheen, W.M., and K.S. Hong. 2002. Thermal haracterization and physicochemical properties of Fe2O3-Mn2O3/Al2O3 system. Thermochimica Acta 381:153. SnO2 or V2O5. Applied Catalysis B: Environmental 44:53. Wills, R.B.H., and G.H. Kim. 1995. Effect of ethylene on postharvest life of strawberries. Postharvest Biology and Technology 6:249. Yilmaz, E., K.S. Tandon, J.W. Scott, E.A. Baldwin, and R.L. Shewfelt. 2001. Absence of a clear relationship between lipid pathway enzymes and volatile compounds in fresh tomatoes. Journal of Plant Physiology 158:1111. Zaki, T. 2005. Catalytic dehydration of ethanol using transition metal oxide catalysts. Journal of Colloid and Interface Science 284:606. Zamorano, J., B. Dopico, A.L. Lowe, I.D. Wilson, D. Grierson, and C. Merodio. 1994. Effect of low temperature storage and ethylene removal on ripening and gene expression changes in avocado fruit. Postharvest Biology and Technology 4:331. Zhang, J., L.X. Rong, Y. Liu, and B.Z. Dong. 2003. SAXS study on the microstructure of Fe2O3 nanocrystal. Materials Science and Engineering A 351:224. Zhang, Y.-J., Q. Xin, I. Rodriguez-Ramos, and A. Guerrero-Ruiz. 1999. Simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene over dimolybdenum nitride catalysts. Applied Catalysis A: General 180:237. Zimowska, M., A. Michalik-Zym, R. Janik, T. Machej, J. Gurgul, R.P. Socha, J.Podobinski, and E.M. Serwicka. 2007. Catalytic combustion of toluene over mixed Cu-Mn oxides. Catalysis Today 119:321. Zorn, M.E., D.T. Tompkins, W.A. Zeltner, and M.A. Anderson. 2000. Catalytic and Photocatalytic Oxidation of Ethylene on Titania-Based Thin-Films. Environ. Sci. Technol. 34:5206-5210.
摘要: 
Ethylene (C2H4) is produced by fruit and vegetable and acts as a plant hormone. Ethylene is beneficially used in many instances such as the promotion of uniform ripening in bananas and as an abscission agent for many crops. Normal levels of ethylene production by produce is small (< 1 ppm) and under normal conditions, no harmful effects occur. However, in enclosed storage facilities the natural ripening process leads to harmful build-ups of ethylene, resulting in spoiled produce. The accumulation of ethylene induces increase in the pathogen susceptibility and physiological disorders of fruits, and consequently the reduction of postharvest life. To prolong the postharvest life, various storage technologies have been used. Physiological methods by which cold storage and modified atmosphere packaging (MAP) were deployed. Biochemical methods by which gene modified and ethylene inhibitors. Physiological-chemical methods remove C2H4 using ethylene adsorbents, ethylene oxidizers and catalytic oxidation. The oxidizers and adsorbents require continuous replacement for long time storage of fruits and vegetables. Gene modified products or ethylene inhibitors could have great concern for human health. It was advisable to remove ethylene by catalytic oxidation during postharvest, especially for long time and large-scale stockroom.
Catalytic oxidation (combustion) is one of the most attractive ways of controlling the emission of volatile organic compounds (VOCs). Noble metals (e.g., Pt and Pd ) or metal oxides (e.g. Cu, Cr and Mn) are among common conventional catalysts. While noble metal catalysts have been effective in removing VOCs. They are rather expensive. Consequently, current transition metal oxides have received much intention recently.Fe2O3 can decompose VOCs to CO2 and H2O assisted by catalysts. It is easy to produce, environmentally friendly and low cost. The high cost of noble metals has received a great of interest in substitution, since transition metal oxides may fulfill the requirements and these transition metal oxides can be considered environmental friendly. Recently, many studies were focused on composite metal oxides catalysts which can provide higher efficiency of ethylene decomposition than merely single oxide catalysts. The objective of the present study was to investigate the effectiveness of the decomposition of ethylene by composite metal oxides. In this study, the composite metal oxides were prepared with Fe, Mn and Cu. We used different synthetic conditions namely composition molar ratio of metals and calination temperature to prepare our composite metal oxides. The different synthesized conditions (composition rate of metal and calination temperature) were also carried out for catalytic oxidation experiment.
The result of catalysis showed that ethylene conversion to CO2 at 180 - 300 ℃ (C2H4:110 ppmv, 200 sccm, O2: 20 %) and the catalyst of Fe:Mn:Cu=3:1:1 exhibited the highest catalytic activity. To increase calcined temperature to 600 ℃, the catalyst changed from amorphous to crystal measured by XRD analysis. After such high temperature treatment, the catalyst increased the particle size, but decreased surface area, resulting the lower conversion ratio. The increase of C2H4 and O2 concentration would increase the reaction rate of catalyst. By applying the Mars-Van Krevelen model, Ea of the catalysis is calculated as 59.1 kJ/mol. The results of XRD and XAS demonstrated that the catalyst is amorphous, and lower O atom bonding energy, which can offer higher catalytic activity than other catalysts. The results of XAS and XPS indicated the Mn atom as the main activated site of Fe3Mn1Cu1. Compared the result to the reference with data of kinetic model and analysis of structure, the rate-determining step of catalysis is corresponding to the C of C2H4 oxidation to CO2.

乙烯為一植物荷爾蒙,可調節植物生長、發育及促使水果熟化的關鍵因子。在水果採收後的長時間儲存、運輸過程中,由於水果所產生乙烯的累積造成催熟,水果會迅速熟化,進而腐爛;因此,如何避免包裝中乙烯的累積,成為水果保存的重要議題。乙烯的調控,可從二方面著手:一、針對水果的生理反應,藉降低儲藏溫度減緩果實生理反應,或用化學藥劑、基因改良來抑制水果產生乙烯的生化反應。二、針對乙烯處理,利用吸附劑、氧化劑、觸媒和TiO2光觸媒,移除乙烯。在化學藥劑及基改作物對於人體健康仍有疑慮下,利用外部處理方式乙烯似乎較為恰當。已運用在乙烯移除上的材料有:吸附劑、氧化劑、觸媒和TiO2光觸媒。傳統上觸媒常以貴金屬做為觸媒,而後因環境及成本因素,金屬氧化觸媒研究逐漸興起;但與貴金屬觸媒相比,以單一金屬氧化物做為觸媒來進行催化氧化反應,效率相對較低,而將貴金屬摻入金屬氧化物來應用,提高反應效率。而近年來之研究,則以混合兩種以上之金屬氧化物製成觸媒,以獲得較單質金屬氧化物觸媒更高的反應效率。本研究將利用複合金屬氧化物觸媒進行催化氧化乙烯實驗,詳細研究目的如下:
一、不同摻雜銅錳比例之奈米氧化鐵複合材料觸媒之精細結構和表面微觀型態鑑定,並對於不同反應溫度下催化氧化乙烯之活性。
二、鍛燒溫度處理對於觸媒催化活性、結構及外觀型態之變化;並探討觸媒結構變化對於催化反應活性之影響。
三、分析複合金屬氧化物觸媒之精細結構和外觀型態,以瞭解觸媒特性及可能之活性來源。
四、測試複合金屬氧化物觸媒催化氧化乙烯之影響因子:初始C2H4濃度、氧濃度、流量及反應溫度,並探討其催化反應動力。
六、利用奈米複合金屬氧化物觸媒表面特性鑑定、影響因子、產物分析及反應動力模式之綜合探討,探討奈米氧化鐵複合材料觸媒對於催化氧化乙烯反應途徑及機制。
研究結果如下:
由SEM、XRD、比表面積分析顯示,適當混合、摻雜Mn和Cu會使複合金屬氧化物觸媒結構偏向外觀鬆散的不定行氧化物,並具有較大比表面積、較低粒徑,催化實驗結果顯示以Fe:Mn:Cu為3;1:1較佳。不同鍛燒溫度(200-600℃),會對複合金屬氧化物觸媒形成結構上之破壞(熔化,黏聚)、結晶化;在XRD分析顯示500-600℃鍛燒後,產生hematite結晶構造;Fe3Mn1Cu1觸媒在比表面積分析上由259 m2/g(200℃)下降至500℃鍛燒的37 m2/g和600℃鍛燒的11 m2/g (Fe3Mn1Cu1);而所計算出之晶格粒徑亦隨鍛燒溫度升高而增加。
而在XANES和EXAFS分析結果顯示,Fe、Mn和Cu組成的奈米複合金屬氧化物中,Fe主要形式為Fe2O3,而Cu會與Fe形成複合結構Fe2CuO4複合金屬氧化物,Mn主要為γ-MnO2和Mn2O3組成。高溫鍛燒後Cu和Fe的相變化,形成Fe2CuO4構造,助於MnO2的穩定,延遲相轉變。由XPS和XAS分析結果顯示,Mn氧化物為主要Fe3Mn1Cu1之反應活性中心,Fe3Mn1Cu1觸媒中Cu的添加可促使Mn3+與Mn4+複合物形成,助於催化反應電子之轉移;相對於無Mn3+與Mn4+複合物結構的Fe3Mn1,其催化反應效率較低。由Fe、Mn和Cu組成的奈米複合金屬氧化物,可在300-180℃將C2H4轉化為CO2 (C2H4:50~200 ppmv ,O2: 1% ~ >30%,流速200 sccm),以Fe3Mn1Cu1活性最高,可在約246 ℃時達到50% C2H4轉化率(約100 ppmv,流速200 sccm)。不定型金屬氧化物可提供觸媒於較低反應低溫時(<250 ℃)催化反應活性,結晶相金屬氧化物造則有具在較高反應溫度下有較高特性轉化率。不定型金屬氧化物其反應活性可能來自於表面結構不穩定(晶格缺陷)之晶格氧;特定晶格結構形成則有助於穩定之催化反應及特定催化反應形成。在C2H4催化反應中,提高C2H4初始濃度或O2濃度皆會增加反應速率。O2濃度在5%以下時反應速率有明顯降低。增加反應物流量(200~500 sccm)會增加反應物空間流速、減少停留時間,使催化乙烯之轉化率下降。針對於Fe3Mn1Cu1觸媒,由催化反應模式: Mars-van Krevelen model和59.1 kJ/mol較為符合本實驗狀態。在Fe3Mn1Cu1複合金屬氧化物觸媒中,依據反應前後XAS、XPS分析,及反應模式等資訊,可推測反應過程為:C2H4 +6O2- (Mn4+之晶格O) 2CO2 + 2H2O + Mn3+。在於較低能量時,C2H4在金屬氧化物觸媒觸媒表面先部分氧化形成MnO-CO中間產物形式,當中部分電子轉移至Mn4+使Mn4+被還原形成Mn3+,當能量使MnO-CO中之M-O斷鍵-CO完全氧化形成CO2並從表面脫附,Mn3+與氧氣反應再被氧化成Mn4+,形成催化反應循環。
URI: http://hdl.handle.net/11455/28117
其他識別: U0005-1102200912204800
Appears in Collections:土壤環境科學系

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