天然气化学.pdf
天然气化学.pdf
June 18, 2007 , DICP 天然气化学 Natural Gas Chemistry 潘秀莲 催化基础国家重点实验室， www.fruit.dicp.ac.cn; panxl@dicp.ac.cn Outlines 1. General introduction to energy map 2. General about Natural Gas 3. Conversion and utilization of Natural Gas 3.1 Direct Conversion 3.2 Indirect conversion via syngas 简单历史 ¾19世纪前，以木材、粮食、农副产品为基本原料的化工； ¾19世纪末，煤化工：焦化、干馏、气化等； ¾20世纪初，煤化工进一步发展； ¾20世纪50年代，石油的年消耗量增大，炼油、石油加工 业； ¾20世纪末，化工80％以上的基础原料来自石油化工； ¾20世纪80年代，石油资源日趋枯竭，OPEC禁运措施，价 格猛涨，以及环境影响，研究和开发替代石油的新能源； Energy use grows with economic development Current and historical global energy mix 6.1% 50% 6.1% 45% 37.3% 26.5% 40% 35% 30% 23.9% 25% 20% Oil Coal Hydro Natural Gas Nuclear 15% 10% 5% 预计2025年天然气的比重将高于40％， 超过石油的能源结构中的比重。 0% 1970 1975 1980 1985 Source: BP Statistical Review 1990 1995 2000 Five key drivers of the energy future • significant hydrocarbon resource potential • misalignment between resource location and demand • growing supply challenges • growth of renewables Supply & Resources • rapid GDP growth esp. in developing countries • growth of megacities • changing customer preferences Technology Demand Growth Security of Supply • advances in all technologies especially info-tech, biotech and nanotech • potential for breakthroughs in energy production, conversion or storage Environmental Constraints • significant rise in import dependence • new policy initiatives to enhance energy security • growing competition for energy resources • climate change and potential for carbon constraints • regulation relating to local pollution Source: BP Statistical Review Renewed interest in N Gas: Environmental restriction and Relatively clean N Gas More domestic gas than once thought Energy imbalance and security Expanded uses Outlines 1. General introduction to energy map 2. General about natural gas 3. Conversion and utilization of natural gas What is NG? Colorless, shapeless, and odorless in its pure form, a mixture of hydrocarbon gases. Typical Composition of Natural Gas Methane CH4 70-90% Ethane C2H6 Propane C3H8 Butane C4H10 Carbon Dioxide CO2 0-8% Oxygen O2 0-0.2% Nitrogen N2 0-5% Hydrogen sulphide H 2S 0-5% Rare gases A, He, Ne, Xe trace 0-20% Usa of Natural Gas 1. Clean fuel commercial and residential use； 2. Raw material for chemical industry (ammonia synthesis, methanol, ethylene, propene, hydrogen, syngas, acetylene, carbon black...) Note: 76％ammonia, 80％ methanol, 42％ ethylene comes from Natural Gas. The The supply supply and and demand demand of of NG NG in in China China 2000 Natural Gas,108 m3 1850 supply 1500 demand 1121 1000 1230 960 490 500 500 257 265.4 0 1980 1985 1990 1995 2000 Year 2005 2010 2015 2020 NGas Utilization in China Domestic （108M3） Natural Gas Coal-based 2000 2010 2020 200 740 1030 200 710 30 950 80 260 600 200 60 400 200 1000 1630 Import （108M3） pipe line LNG Total 200 NGas Resource Distribution in China Size Distribution of Gas Fields in China >300 108M3 14 (44.3%) 100～300 108M3 30 (27.9%) 50～100 108M3 27 (12.9%) <50 108M3 138 (14.8%) 204 Gas Fields in Total Pipeline Project in China 12x 109 M3/y Outlines of this lecture 1. General introduction to energy map 2. General about Natural Gas 3. Conversion and utilization of Natural Gas What and how? Why important? 天然气转化和利用的核心是 催化 优化能源结构、保护生态、缓解石油供应不足 催化对社会进步的贡献 Fe3O4-Al2O3-K2O N2 + 3H2 2NH3 合成氨熔铁催化剂 乙烯 丙烯 TiCl3-AlR3 Cp2Ti(Ph)2 聚乙烯 聚丙烯 Ziegler-Natta催化剂 •使化肥工业迅速发展 •塑料产量增加了100倍 •迎来了现代农业 •奠定了石化工业的基础 •1918年诺贝尔化学奖 •1963年诺贝尔化学奖 国际天然气利用研究情势 国际天然气利用研究情势 CH44 Re-injection LNG Gas Sales Power Generation Syngas Syngas(CO, (CO,H2) H2) Hydrogen Refineries Fuel Edib.Oil/Fat Fischer-Tropsch Products Clean Fuels Lubricants Wax Alpha Olefins Acetic Acid Ammonia Methanol Urea Acrylonitrile Fertilisers DME, Formaldehyde Solvents, MTBE Clean Fuels, Fuel Cells Power Generation Olefins Research in Industrial Companies Syngas Manufacture GTL, Methanol in the Joint Research Center with CAS Syngas and GTL in a CNPS Laboratory in the Petroleum University Daqing Beijing Lanzhou Xi’an Syngas, Methanol and GTL in Southwest Institute for Natural Gas BP-CAS Program Clean Energy Facing Future Natural Gas, Hydrogen Shanghai Sichuan Low Alkanes Conversion, Hong Kong in SINOPC Institute Research in Academia Methane Coupling in Lanzhou Institute of Chem. Phys. Syngas from Coal, methanol, GTL in Taiyuan Institute of Coal Chem. Syngas, H2, Oxygenates, olefins , GTL, Aromatics Fundamental Research at DICP Beijing Taiyuan Lanzhou Xi’an Nanjing Sichuan Syngas and Catalytic Combustion in Sichuan Uni. Syngas, Acetylene and Methanol at Institute of Organic Chem. Xiamen Dalian H2 and C1 Chemistry in Tianjing Uni. Shanghai Low Alkane Conversion, Fundamental Research in Nanjing Uni. Hong KongFundamental Research on Methane Activation In Xiaman Uni. National Major Basic Research Program (MOST, 973) 天然气、煤层气优化利用的催化基础 99年10月 – 2004年9月； 设计2个大学，3个研究所，共32位教授和35位研究人 员； 总体目标：发展一系列以催化为核心的科学和技术…转化 为高洁净度液体燃料和具更高经济价值且便于运输的甲 醇、烯烃、芳烃和含氧化物等基本化工原料。 基础研究：以C-H选择活化和定向转化为目标，创新催化 过程和催化剂，建立和发展动态催化理论，从本质上认识 “控制活化、选择转化”的核心问题。 National Major Basic Research Program (MOST, 973) 天然气及合成气高效催化转化的基 础研究 2005年1月 – 2009年12月； 涉及8个大学，2个研究所，60多位研究人员； 子课题：天然气制合成气及规模制氢和CO2处理； 合成气制取高品质液体燃料； 合成气制含氧化物； 基于合成气和天然气的高温燃料电池； 天然气直接催化转化； 天然气高效转化的非常规过程； 催化剂和催化体系的构效关系和动态表征； 催化过程的微观机制和反应中间体的鉴定。 Features of CH4 C-H 键能: 438.8kJ•mol-1 电离势: 12.5eV 质子亲和势: 4.4eV 酸性 (pKa): 48 自然界中最稳定的有机分子之一 自然界中最稳定的有机分子之一 最具挑战性和机遇 Property of CH4 Molecular weight 16.04 Volume (standard)(L/mol) 22.38 Density (101.32kPa, 0°C)(kg/m3) 0.7167 Boiling point/K 111.75 Thermal conductivity (101.32kPa, 0°C)(W/m.K) 0.03 Explosion limit in air (20°C)% 5.3-14.0 Autogenous ignition T/K 811 Combustion heat/(kJ/m3) 35877 一些简单反应的标准自由能变化 Reaction ΔGӨ/ (kcal/mol) 400 K 1000 K 2 CH4 → C2H4 + 2 H2 18.9 9.5 2 CH4 → C2H6 + H2 8.6 8.5 2 CH4 + O2 → C2H4 + 2 H2O -34.6 -36.4 2 CH4 + ½ O2 → C2H6 + H2O -18.4 -14.5 CH4 + Cl2 → CH3Cl + HCl -26.0 -27.8 CH4 + ½ O2 → CH3OH -25.4 -18.0 CH4 + CO → CH3CHO 16.0 33.6 CH4 + CO2 → CH3COOH 19.2 35.5 CH4 + H2O → CO + H2 28.6 -6.5 CH4 + CO + ½ O2→ CH3COOH -40.0 -10.0 甲烷的转化和利用，化学工业出版社，2005 甲烷的催化转化 ¾ C-H 键的活化是催化循环的一部分，而不是 计量反应； ¾ 催化体系有足够的选择性，即产物中C-H键比 甲烷稳定； ¾ 体系的活性应该足够高使反应在温和条件下进 行。 Conversion of methane Selective Oxidation Oxidative coupling (OCM) Direct Conversion Decomposition to H2 + C Aromatization Catalytic Combustion Natural gas (CH4) Electricity NH3 syn Methanol Syngas (CO＋H2) Ethylene, etc DME Liquid fuels: F-T syn. Oxygenates Direct Conv Selective Oxidation 气相均相氧化 反应条件 4 MPa，450－500°C，影 响因素很多。 气固多相催化氧化 反应条件 450－700°C，多采用 SiO2 或 Al2O3负载的MoO3, V2O5等 催化剂；甲醇产率<5％。 注：问题难以控制选择性氧化。从工业化角度，转化 率 >10%，选择性 >80%。 液相催化氧化 常以过渡金属配合物为催化剂，以 强酸、超强酸、超临界流体为溶 剂，以O2 、H2O2 、K2S2O8 、SO3 为 氧化剂。 Direct Conv Difficulty of direct methanol synthesis: C-H bonding of CH4 CH3OH 434.7 kJ/mol 388.7 kJ/mol Some transition metal complexes could selectively activate the more stable C-H bond? Oxidative addition; σ bond displacement; free radical; electrophilic activation. Advantage of low T synth: Protection of product in acid medium (ester) Examples for low T… G. Olah Direct Conv Electrophiles and superacids, Periana et al. Science, 1993, 340; Science 1998, 560. Net reaction: CH4 + 1/2O2 Con.CH4 50%, yield 43% HgSO4/H2SO4 180 ℃ CH3OH More examples… Fujiwara et al. CH4+ CO Direct Conv Angew. Chem. Int. Ed. 2000, 2475 CaCl2, Pd (OAc)2 /Cu(OAc)2 CF3CO2H/(CF3CO2)2O K2S2O8, 85 ºC CH3COOH 20 atm CH4; 0.5 mmol CaCl2, 15 h reaction time, 1.05 mmol product. Bell et al. JACS 2003, 125, 4406 CH4 + SO2 + K2S2O8 CF3SO3H, CaCl2 65 °C CH3SO3H 69 atm CH4; triflic acid; 10 h, 1.44 mmol product. ? Work of Sen et al. H2O2 + CH4 (CF3CO)2O CF3COOCH3 PdCl2, 90 °C 2+ CF3COOH + CH4 + Pd Direct Conv 80 °C CF3COOCH3 + Pd 0 + 2H + CF3COOH + CH3OH ? Stoichiometric E. Gretz, et al. J. Am. Chem. Soc. 109 (1987) 8109; L. Kao, et al. J Am Chem Soc 113 (1991) 700 0 2+ Pd → Pd ? ¾ Wacker process: CuCl2/CuCl/O2 ¾ Others? Direct Conv The Wacker Process Direct Conv Developed simultaneously by Wacker-Chemie and by the group of Moiseev. It involves the reaction of ethylene with PdCl2 in HCl (reaction 1). Pd(II) is reduced to Pd black. To make the reaction catalytic, Pd(0) is reoxidized by CuCl2 and O2 (reactions 2 and 3). 2Pd Cl C 2H 4 + 4 + 3H2O 0 + 2CuCl +2ClPd 2 + 4Cl 4H O C u Cl+ + + O2 3 - C H3CHO + Pd0 + 2H3O + 4Cl (1) Pd Cl42 -+ 2CuCl (2) 4CuCl2 + 6H2O (3) Direct Conv Better to explore… ► To make a catalytic process； ► To avoid HCl, H2SO4, SO3, SO2; ► To use O2 as oxidant. Combination of Pd2+ and Q Run 1 2 3 4 5 6 Pd2+ Q O2 CF3COOCH3 Pd2+a (μmol) (μmol) (atm) (μmol) (%) 10 10 10 10 10 10 10 10 10 10 0 2020 5050 100 2020 5050 0 0 1 1 0 0 0 0 1 1 30 55 34 67 9.5 30 55 60 34 67 --15 27 ---92 15 27 Conditions: CF3COOH: 3 ml (39 mmol), CH4: 54 atm (114 mmol), O2: 1 atm (2 mmol), 80 ºC, 10 h; a: Remaining Pd2+ after the reaction. OH CF3COOH + Pd 2+ + CH4 O + 1/2O2 + H2O OH O OH O + Pd0 +2H + 2 H+ + Pd0 + CF3COOCH3 + Pd 2+ O OH Scheme of methane oxidation OH C H + CF COOH 3 4 Pd 2+ 1/2O OH O CF COOCH 3 3 Pd0 + 2H+ O 2 Search for active oxidants to speed up: O OH + 1/2O2 OH + H2O O ¾ nitrogen oxide /CH2Cl2 Bosch, et al. J. Org. Chem. 1994, 59, 2529. Feasibility test in CF3COOH OH O + NO2 OH + NO + H2O O Direct Conv Direct Conv Combination of Pd2+ & Q: Run Pd2+ (μmol) Q (μmol) NaNO2 (μmol) O2 (atm) CF3COOCH3 (μmol) Pd2+a (%) 1 2 3 4 5 5 6 10 10 10 10 10 10 10 0 20 50 100 20 20 50 0 0 0 0 00 0 0 0 0 0 11 1 9.5 30 55 60 34 34 67 ---92 15 15 27 7 8 9 10 11 10 5 20 10 10 20 20 20 50 100 20 20 20 100 100 1 1 1 1 1 69 32 106 70 67 98 95 54 95 98 CF3COOH: 3 ml (39 mmol), CH4: 54 atm (114 mmol), O2: 1 atm (2 mmol), 80 ºC, 10 h; a: Remaining Pd2+ after the reaction. ¾ A catalytic process CF3COOCH3 (umol) 120 100 Q and NaNO2 key to ¾ prevent the precipitation of Pd 80 60 40 20 0 0 4 8 12 16 reaction time (h) The yield to CF3COOCH3 versus the reaction time. Pd key, determining ¾ the TON ¾ TON: 0.7 h-1 Direct Conv Further confirmation Run Pd2+ (μmol) Q (μmol) NaNO2 (μmol) O2 (atm) 1 2 3 0 0 0 20 0 0 0 20 20 1 0 1 isotope experiments 14 atm 13CH4 40 atm 12CH4 CF3COOCH3 (μmol) 0 0 0 Pd2+a (%) ---- GC-MS O2 -COO13CH3 (m/e = 60) 1 CF3COOH -COO12CH3 (m/e = 59) 3 CF3COOCH3 Direct Conv Low T selective oxidation of CH4 OH CH4 + CF3COOH NO2 Pd2+ OH CF3 COOCH3 Pd0 + 2H+ O H2O + NO 1/2O2 O CH4 + 1/2O2 → CH3OH Catalytic process in one pot at 80 °C O2 as oxidant TON = 0.7 h-1 An, Pan, Bao et al. JACS 128 (2006) 16028. 直接法制甲醇的状况 Direct Conv 直接法的优点： 反应放热，从能耗上有利；工艺和设备简单。 工业化的要求： 单程转化率10 ~ 15%, 选择性 80 ～ 90％ 目前水平： 转化率2 ～ 4％，选择性 40 ～ 70％ Direct Conv High Temperature Conversion of Methane to Aromatics Direct Conv Typical HT Direct Conversion Process z Selective Oxidation CH4 + O2 Ä CH3OH＋CO2＋H2O z Oxidative Coupling CH4 + O2 Ä C2Hx＋CO2＋H2O Direct Conv A New Route … Route… To higher hydrocarbons, without forming CO2 ? ± Mo/HZSM-5 CH44 + O2 6CH Higher HC C H + 9H2 6 6 Y. Xu, et al.,Catal. Lett. 21 (1993) 35-41 Direct Conv Conversion of methane to aromatics H CH3 H CH3 C M C M nCH33 n/2C22Hxx Catalysts Mo, W, Re… HZSM-5, MCM-22… Bifunctionality of Mo/HZSM-5 Acidity and catalytically active sites Aromatization over different Mo species 30 Mo species related to B acid sites(MoCxOy) Mo species in the form of Mo2C Mo species supported on SiO2 20 n Highly active and stable MoCxOy; TOF n Low activity and stability of Mo2C; 10 n 0.5 acidic sites per unit 0 30min 240min 600min cell required for aromatization. D. Ma, X. Bao et al., Chem. Eur. J. 8 (2002), Y. Xu, X. Bao, et al., J. Catal. 216 (2003) . Effect of pore morphology 100 80 MCM-22 Percentage (%) ZRP-1 Conv.of CH4 ZSM-5 60 Sel.of BTX ZSM-11 Sel.of Nap. 40 Sel.of coke JQX-1 20 SBA-15 ESR-7 0 8 ring 0.4nm 10ring 0.55nm 10\12 12ring meso >1nm 0.75nm Applied Catalysis A-general 188 (1-2)，J. Catal. 216 (2003) Comparison between Mo/ZSM-5 and Mo/MCM-22 Open Mo/HMCM-22 Solid Mo/HZSM-5 Y. Shu, X. Bao et al., Catal. Lett. 70 (2000) 67. Pore morphology of carriers Shape selectivity ¾size (dynamic diameter of benzene (0.59 nm) ¾ crossing with two-dimensional structure ¾ micro-mesoporous composite Direct Conv Achievements over the years Convers Yield to Benzene Life time before 99 2003 < 1014 % 18% (Coupled) 12 10 ~12% ～6-8％ 8 6 6～8 h 4 ~50 h yield 2 0 1993 1999 2001 2003 700°C , 1atm with a flow rate of 1500mL/gcat. h Conversion of methane Indirect Conv Selective Oxidation Oxidative coupling (OCM) Direct Conversion Decomposition to H2 + C Aromatization Catalytic Combustion Natural gas (CH4) Electricity NH3 syn Methanol Syngas (CO＋H2) Ethylene, etc DME Liquid fuels: F-T syn. Oxygenates Methane to syngas Direct Conv CH4 + ½ O2 CO + 2 H2 ΔH298K = -35.5 kJ/mol CH4 + H2O CO + 3 H2 ΔH298K = 206.29 kJ/mol CH4 + CO2 2CO + 2 H2 ΔH298K = 247 kJ/mol 一般采用镍催化剂，反应温度700 °C以上，通过调节改变原 料气比例和反应可以调节合成气的组成。 Syngas to ammonia NH3 synth 国际上合成氨的原料构成 / % 1929 1939 1953 1965 焦炭、 65.2 煤 53.6 37.0 5.8 焦炉气 15.8 27.1 22.0 20.0 天然气 － 1.3 26.0 石脑油 － － 重油 － 其他 合计 原料 1975 1980 1985 1990 9.0 5.5 6.5 13.5 44.2 62.0 71.5 71.0 77.0 － 4.8 19.0 15.0 13.0 6.0 － － 9.2 5.0 7.5 8.5 3.0 19.0 18.0 15.0 16.0 5.0 0.5 1.0 0.5 100 100 100 100 100 100 100 100 我国合成氨的原料构成 / % 原料 1983 1991 1994 焦炭、煤 65.4 67.0 64.0 焦炉气 0.8 1.3 1.2 天然气 19.2 17.5 18.9 石脑油 7.9 4.3 6.6 重油 5.9 9.4 8.7 其他 0.8 0.5 0.6 合计 100 100 100 NH3 synth NH3 synth o 25 C 100 N2 Equilibrium Conversion (%) o 100 C 80 VN2 : VH2 = 1:3 60 o 200 C 40 o 300 C 20 o 400 C 0 2 4 6 Reaction Pressure (atm) 热力学平衡转化率 8 10 NH3 synth Fe (111) is 430 times more active than Fe (110) and Fe (100) is 30 times higher. Al2O3 and K2O are additives. A1203 首先在表面生成与 Fe304同晶的 FeA1204,然后以这种新的表面为模板，使 α -Fe 晶体生长向(111)或(211)面定向暴露在反应混合物中 NH3 synth Recent progress in NH3 synthesis N2在不同物质上的吸附热及其与氨合成活性 的关系 Co3Mo3N, Ru, Fe催化剂的氨合成 活性 Norskov, JACS 2001 Ba is a significantly better promoter for metals at the right-hand side of the volcano curve than for metals at the left side, whereas the opposite is true for the alkali metal promoters. JC 2003. NH3 synth Effect of catalyst supports K/Ru/C = 2/10/100, atmospheric pressure, N2/3H2 30 ml/min, GHSV 637 h-1. Activity of K-promoted Ru catalysts supported on: SiO2< zeolite (NaX) < AC<γ-Al2O3 < CeO2 < C60-70 < MWNT Liao DW, Appl. Surf. Sci. 2001. Syngas to methanol methanol Methanol (CH3OH) is an alcohol fuel. lower emissions, higher performance, and lower risk of flammability than gasoline. Methanol is a fundamental raw material for chemicals. The third most demanded raw materials for organics following olefins and aromatics, to HCHO, CH3COOH, MTBE, 醋酸酐，甲酸甲酯，二甲 醚，乙二醇，乙醛，乙醇等。 Syngas to methanol methanol 合成氨和甲醇是天然气化工中具有优势的大宗化学 品领域，工艺成熟，但对新型高效催化剂和反应器 的研究一直没有间断。 CO + 2H2 k1 k -1 CH3OH 第一套装置BASF在20世纪20年代建立。采用ZnO-Cr2O3为 催化剂，反应温度350－450°C，反应压力为25－75MPa。 1966年英国ICI推出了低压合成甲醇，采用高活性的Cu基催 化剂，压力5－10MPa。 MTO Syngas to olefin via methanol 石脑油 合成气 高分子材料 乙 烯 化工原料 MTO Demand of Ethylene Year Ethylene demand/Mton 1995 1997 2000 2010 2.39 2.70 3.50 8.00 分子筛催化性能随结构的变化 90 C2= 95 95 总烯收率 总烯收率 90 90 85 85 80 80 75 75 1998 1998 2000 2000 2003 2003 O le fin s e le c tivity (w t%) 80 C3= 70 60 50 40 30 20 10 0 SAPO-44/A SAPO-44/B SAPO-44/C ZSM-11 SAPO-5 Pulsed methanol reaction at 400 °C, GC analysis results SAPO-34 ZSM-22 low 70% 80% 90% F-T Fischer-Tropsch过程制备液体燃料 汽油 原油 油 油 品 品 柴油 H2O CH4 O2 天然气 CO 部分氧化 H2 合成气 费-托合成 液体燃料 复杂的F-T反应： F-T nCO + (2n+1)H2 → CnH2n+2 + nH2O nCO + 2nH2 → CnH2n + nH2O nCO + 2nH2 → CnH2n+2O + (n-1)H2O CO + H2O → CO2 + H2 还有：水煤气变换、醇脱水、烯烃加氢、异构化、 析炭反应等 产物：低碳烃 (C1 ~ C4)、汽油 (C5 ~ C11)、柴油 (C12 ~ C18)、蜡 (C19+) 及醇、醛、酸、酯等。 F-T F-T 合成油的历史和主要国际公司 ¾1925, Fischer & Tropsch ¾30年代中压合成，先后在德、美、法、前苏联、 南非等建立合成油厂； ¾60年代，石油开采，F－T失去活力 ¾70年代，石油资源紧张，F－T开发继续。 Sasol（南非）;Shell (荷兰）；Exxon(美国); Syntroleum (美国); BP（英国）; Rentech (美国). F-T 合成气制液体燃料 钴基催化剂－500小时稳定性试验结果： 甲烷选择性<6% C5＋选择性>90％ 链增长几率>0.90 蜡油比在3.8左右 形成低甲烷重质烃 固定床工艺 与Shell 公司水平 相当，高于其他国 际公司 中科院山西煤化所 F-T 热力学… CO + H2 → CH4 + H2O ΔH298K = - 206kJ/mol CO + 5H2 → C2H6 + 2H2O ΔH298K = - 347kJ/mol 2CO + 2H2 → CH3COOH ΔH298K = - 215kJ/mol 2CO + 3H2 → CH3CHO + H2O ΔH298K = - 457kJ/mol 2CO + 4H2 → CH3CH2OH + H2O ΔH298K = - 256kJ/mol 强放热反应，在50－350 °C内，产物生成的概率是 CH4>饱和烃>烯烃>含氧化物。 实际产物分布与催化剂、反应条件等相关。 Anderson-Schulz-Flory 分布 mn = (1-a)an-1 F-T m：具有n个碳原子的烃类产物 的mol分数； a：碳链增长概率，取决于催化 剂和反应条件，随温度升高而降 低，随H2/CO ratio而降。 Ru-based cats Co-based cats Fe-based cats 0.85 ~ 0.95 0.70 ~ 0.80 0.50 ~ 0.70 F-T过程中的产物控制 CH4 突破 Schulz-Flory 分布 的限制 柴 油 碳原子数 (n) F-T Product distribution F-T H2 dissociative adsorption on most transition metal. Cu (molecular adsorption) → methanol Ni (dissociative adsorption) → CH4 Co, Fe (strong bonding of Metal-C) → C2+ F-T Reaction mechanisms under debate: 碳化物机理 含氧中间体机理 CO插入机理 双中间体机理 C2活性物种理论 烯烃重吸附理论 涉及：链引发（即反应开始时活泼的表面物种的形成） 链增长（碳链的形成） 链终止（最终产物的生成） F-T ¾ 碳化物机理： CO M－C H2 H H = C M 聚合 金属碳化物 －CH2－CH2－CH2－ 亚甲基 ¾ CO插入机理： M H C O M M -H2O CH2 CH3 CO 2H M M CH3 O = C H H = M = H CO H O C M ¾ 烯烃重吸附机理： 烯烃重新在催化剂表面吸附，加氢生成烷烃、异构化、裂解 反应、插入反应等。 Possibility of syngas to olefins? F-T Fe基催化剂特点： 常用的载体：Al2O3, SiO2, zeolite, Activated carbon 助剂：K, Cu, Mn 优点：低碳烯烃高选择性，高辛烷值的汽油； 缺点：对水煤气变换高活性，高温时易积炭，链增长 能力差。 其它：在反应中复杂的相组成变化。 注：燃烧的抗震程度以辛烷值表示，辛烷值越高表示抗震能力愈高 Possibility of syngas to olefins? Progress Degussa， Fe-ZnO-K2O-V (or Mn, Ti) (100:10:4~8) H2/CO = 1/:1, 75% sel. C2=~C4= Shell, Fe-K-Cu-Zn/SiO2 (25:5:10:20), mainly 58% C5+ cracking in the following step DICP K-Fe-MnO/SiO2, H2/CO = 2, 1000 h test stability F-T Use Carbon as support… Steen, catal.today 2002 Coville, appl.catal. 2005 General finding: Lower CH4 and higher olefin selectivity compared to other Fe/C cats. Reasons are not known yet. F-T 碳材料家族 sp2 bonding carbon graphite fullerene onion-like carbon (OLC) nanotube filaments sp3 bonding carbon diamond carbon black,Shigeo activated MARUYAMAcarbon, , Univ. Tokyo etc Carbon Nanotubes Multiwalled CNTs ¾ Higher purity compared to AC ¾ Well defined morphology of nanochannels – Geometrical confinement; ¾ Graphitic layers –Thermal stability, electron conductivity; ¾ Unique H2 adsorption and activation capability. F-T More examples Cat. Reaction F-T Comments Ref. Rh/MWNT NO decomposition Higher conversion than with a Rh/Al2O3 Luo et al., Catal Lett 2000 Co/MWNT Cyclohexanol dehydrog. Act. & sel. to cyclohexanone Liu et al., Catal Lett 2001 Pt/CNT higher power density Sun et al, Carbon 2002 Cathod catalyst Steen et al, Catal Today 2002; Bezemer et al., JACS 2006 Co/MWNT F-T synthesis Rh/MWNT Cinnamaldehyde hydrog. Pt/CNT Act. 3 times higher than Giordano et al., Eur J Inorg Chem 2003 Rh/C catalyst Nitrobenzen hydro. High act. compared AC Li et al., J Mol Cat 2005 Why encapsulates? F-T Geometrical confinement Curvature causes binding energy: Interior > groove sites > external. [Yates, Chem Phys Lett 383 (2004) 314] Template for Beta-zeolite synthesis and CoFe2O4 Nhut et al., Appl. Catal. 2003, 254, 345 Theoretical calculation: Reaction in CNT channels Santiso et al. Appl.Surf.Sci.2005, 252, 766 F-T Introduction of Fe2O3 nanoparticles into carbon nanotube channels (a) Fe2O3 nanoparticles inside nanotubes; (b) Fe2O3 nanoparticles dispersed on its outer wall Chen, Pan, Bao et. al., JACS, 2006, 128, 3136. Syngas directly to olefin F-T F-T 物理化学性质的表征并与反应活性关联 ¾ TEM, SEM等 → 形貌，如粒子大小，分散情况等； ¾ XRD, Mossobauer谱，XPS →制备过程和反应前后催化剂组成、晶相和价态的变化； ¾ TPR等技术 →表面铁氧化物中在载体表面还原的难易程度，金属－载体的 相互作用，吸附脱附行为等； ¾ FT-IR，Raman →表面活性物种； ¾ XAFS →晶体周围环境的信息，如金属原子的配位数等… Fe2O3@CNTs encapsulates F-T TEM Images RT 600℃ Chen, Pan, Bao et. al., JACS, 2006, 128, 3136. Autoreduction of Fe2O3@CNTs with varying diameters Fe2O3@CNTs T F-T Fe@CNTs + CO Fe Chen, Pan, Bao JACS, article, 2007, 129, 7421 Fe2O3@CNTs encapsulates Fe-O mode: Bulk Fe2O3 at 283 cm-1 F-T Fe2O3@CNTs encapsulates F-T Chen, Pan, Bao JACS, article, 2007, 129, 7421 Oxidation of Fe@CNT encapsulates A Fe@CNTs + O2 → Fe2O3@CNTs Gas 1 MFC Gas 2 MFC Gas 3 MFC Purge Gas B MFC A: Fe-in-CNTs; Preheater 20 ºC Zone control Δf Δm = 2m fo 20 ºC 20 ºC B: Fe-out-CNTs; C: Fe-in-SBA-15 MS GC 20 ºC Heater 2 Transformation monitored in situ by XRD Fe Fe2O3 Chen, JACS, article, 2007, 129, 7421 Stabilization of metallic Fe inside carbon nanotube channels. Corelation between the structure and catalytic activity & selectivity? C2 oxygenates synthesis (mainly ethanol) Fermentation Biomass Coal Natural gas Syngas C2-Oxy Fuel, fuel additive ethanol Raw material for chemical industry Rh-based catalyst. Catalytic process is a beneficial supplementary. C2-Oxy Scheme of oxygenate synthesis from syngas Beyond the effect of particle size… C2-Oxy RhMn-in-CNT RhMn-out-CNT C2 oxygenates yield as a function of time on stream Pam, Fan, Chen, Bao et al, Nature Materials 2007, 6, 507 The effect of particle size C2-Oxy RhMn-out-CNTs RhMn-in-CNTs Catalyst fresh Post-reaction/120 h RhMn-out-CNTs 2-4 nm 5-8 nm RhMn-in-CNTs 1-2 nm 4-5 nm Syngas to higher alcohols alcohols Definition: a mixture of alcohols of C1 ~ C6. Usage: Clean transportation fuel or fuel additives, high octane number; raw material of chemicals. Cats in research: Modified F-T cats (Cu-Co, Mo-based); Modified methanol cats (Cu-Zn, Zn-Crbased). Difficulties: Low activity, selectivity, stability, and economically unfavorable CNT-promoted methanol cats alcohols CNTs+Cu-ZnO-Al2O3 in the syngas conversion to methanol CuZnOAl2O3 12.5%CNTs-CuZnOAl2O3 CO conversion 29.5% 42.4% MeOH formation rate /μmol MeOH s-1 (m2surf Cu)-1 0.095 0.118 493K, 2.0MPa, feed gas H2/CO/CO2/N2 = 62/30/5/3(v/v), GHSV = 3000 h-1 The promotion effect : (1) an excellent dispersant of catalyst components; (2) an excellent adsorbent, activator and reservoir of H2. HB Zhang’s group, Chem. Commun., 2005, 5094; Catal. Lett. 85, 2003, 237 CNT-promoted cats Co3Cu1-11%CNTs alcohols Co3Cu1 At 50 bar, H2/CO/CO2/N2 = 46/46/5/3, GHSV 104 ml h-1gcat-1. TPR indicated a lowered reduction temperature, increasing the CoxCuy species reducible to lower valence-state. alcohols (a)Co3Cu1 and (b) Co3Cu1-11%CNT fed with CO2 containing syngas; (c)Co3Cu1 and (d) Co3Cu1-11%CNT fed with CO2 free syngas. H2-TPD (a) Co3Cu1-11%CNT; (b) Co3Cu1 Indicate: (1) presence of surface Con+ species (CoOOH/Co3O4) may be closely related to the highly selective formation of HAS. (2) Presence of reversible active H species. 主要科学问题 z 选择氧化过程中的氧物种及选择性控制 z 合成气转化中的产物分布的控制调节，尤 其 CH4 形成机理和抑制 z 甲烷的高效直接转化，包括酶催化转化 z 以甲醇为原料的新化学过程 z 贵金属替代的可能性 主要科学问题 z 催化过程的原位、动态表征 z 高温稳定催化剂的控制合成 z 基于纳米概念的催化理论 部分阅读文献： 1. G.A. Somorjai, Chemistry in Two Dimensions: Surfaces. Cornell University Perss, Ithaca, NY 1981 和中译本。 2. G.A. Somorjai, Introduction to Surface Chemistry and Catalysis, John Wiley & Sons, Inc. 1993. 3. A. Sen, Catalytic functionalization of carbon-hydrogen and carboncarbon bonds in protic media, Acc. Chem. Res. 31 (1998) 550. 4. R.H. Crabtree, Aspects of Methane Chemistry, Chem. Rev. 95 (1995) 987. 5. Z. Liu et al., New Progress in R & D of lower olefin synthesis, Fuel Processing Technology 62 (2000) 161. 6. H. Dai, Carbon Nanotubes: Synthesis, Integration, and Properties, Accounts Chemical Research 35 (2002) 1035. 7. R.A. Sheldon, Chemicals from synthesis gas, D. Reidel Publishing Company, 1983. 8. 贺黎明，沈召军，甲烷的转化和利用，化学工业出版社，2005. 9. 汪寿建等，天然气综合利用技术，化学工业出版社，2003. 10. 周怀阳等，天然气水合物，海洋出版社，2000.