【作者】 熊辉；

【导师】 李光兴；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2010， 博士

【摘要】 氧化羰化法在碳一化学的研究与开发中具有重要意义,CuCl催化醇类液相氧化羰化合成碳酸酯具有高反应性、高选择性和环境友好性等特点,符合绿色化学发展趋势；但存在着催化剂寿命短、分离困难及腐蚀严重等缺点,制约了氧化羰化反应的发展。开发新型高效、环境友好和低腐蚀性的催化体系逐渐成为均相催化领域的研究热点。Schiff base化合物易与CuCl配合,既可提高CuCl的催化活性又能减缓CuCl的腐蚀作用,具有重要的理论意义及广阔的应用前景。本文首先研究了CuCl/Schiff base催化体系中,不同含氮配体对甲醇氧化羰化反应性能的影响,筛选出高活性的CuCl/Phen催化体系,其碳酸二甲酯收率比CuCl催化剂提高了3倍。同时探讨了不同含氮配体对乙醇氧化羰化反应性能的影响,筛选出最佳活性的催化体系CuCl/Phen/NMI;考察了配体浓度,反应温度对催化活性的影响,并建立了相关的反应动力学方程。研究结果表明,当CuCl浓度为0.2 mol/L,含氮配体与CuCl的摩尔比为2:1,反应温度393 K,反应压力2.4 MPa,CO与O2的分压比为2：1,反应时间3h的条件下,CuCl/Phen/NMI络合催化体系合成碳酸二乙酯的反应活性最高,乙醇转化率为15.2%,碳酸二乙酯选择性为99.0%,其收率比CuCl催化剂提高了3.5倍。CuCl/Phen/NMI催化反应体系的反应动力学方程为活化能为53.4 kJ/mol。为了克服均相催化剂不易回收分离、寿命短以及对环境腐蚀的缺点,研究了均相催化体系负载化途径,探讨了采用溶胶-凝胶技术以有机-无机杂化材料(OIH)作催化剂载体,制备负载CuCl配合物催化剂。筛选出正硅酸乙酯(TEOS)作硅源,5-氨基-1,10-菲罗啉(NH2-Phen)作有机配体,γ-氯丙基三乙氧基硅烷(CPTES)作间隔剂,合成OIH载体,最佳制备条件：TEOS、CPTES及NH2-Phen物质的量的比为6:1.1:1, NH2-Phen用量10 mg/ml DMF,反应温度343 K,反应时间72h。该载体与CuCl络合制备出铜负载量为7.1 wt%的CuCl/Schiff base/OIH负载催化剂。采用元素分析、傅立叶变换红外光谱、核磁共振(1HNMR,29Si-MAS-NMR)等分析手段对合成中间产物及负载催化剂进行了表征。同时考察了CuCl/Schiff base/OIH负载催化剂在甲醇氧化羰化反应中的催化活性；在反应温度393 K,反应总压2.4 MPa,CO与O2的分压比2:1,CuCl浓度0.1mol/L,反应时间2h的条件下,CuCl/Schiff base/OIH负载催化剂与CuCl催化剂相比,其产率提高了25.0%,负载催化剂循环使用五次,催化活性基本保持不变,催化剂中活性组分铜平均流失率仅为2.2 wt%。实验结果表明,CuCl/Schiff base/OIH催化剂是一种热稳定性好、活性组分流失率低的负载催化剂。本文重点研究了Schiff base配体的引入对CuCl催化氧化羰化合成碳酸二甲酯反应寿命的影响。对CuCl/Phen配合物催化剂进行了330小时稳定性测试,考察了反应过程中甲醇转化率和碳酸二甲酯选择性的变化。反应330小时后CuCl/Phen催化剂活性降至初始活性的78%,结合元素分析、X射线光电子能谱、X射线衍射光谱、热重-差热分析和原子吸收光谱等表征方法,得出催化剂失活的主要原因是：氯的迁移流失和一价铜的歧化,讨论并提出了CuCl/Phen配合物催化剂在甲醇氧化羰化反应中的失活机理。本文还探讨了CuCl/Schiff base催化体系的腐蚀性能。采用挂片失重法研究了一系列含氮配体在CuCl催化氧化羰化体系中对合金材料的缓蚀效果。试验结果表明,含氮配体在CuCl催化体系中对合金材料具有明显的缓蚀作用,在CuCl浓度0.2 mol/L, Phen浓度0.1 mol/L, NMI浓度0.1 mol/L时,对镍基合金TK的缓蚀效率达到98.2%,镍基合金TK的年腐蚀速率为0.0152 mm/a,已达到耐蚀四级标准。同时对合金材料在不同反应条件下的腐蚀试样进行扫描电子探针分析,结合电化学测试结果和氧化羰化反应机理,提出了合金材料在CuCl催化氧化羰化反应体系中的腐蚀机理和含氮配体的缓蚀机理。上述研究结果对今后开发氧化羰化合成碳酸酯新工艺及工业反应器材质的选择具有重要的指导意义。更多还原

【Abstract】 Catalytic synthesis of carbonates by oxidative carbonylation of alcohols is an important method in the research and development of the C1 chemistry, which reduces the environment pollution and resource consumption in the chemical industry; it is also a main topic in the field of green chemical industry. The oxidative carbonylation catalyzed by CuCl is one of the most effective methods to produce the carbonates, but this catalytic system often has many disadvantages, such as short lifetime, difficult separation from the products and corrosive effect on the reactor materials. The research and development in the field of copper based catalysts for oxidative carbonylation is needed. Development of a new efficient, environmentally friendly and low-corrosive catalytic system has become a research focus in the field of catalysis. Schiff base ligands combined with CuCl, not only improve the catalytic activity but also reduce the corrosion, which have great theoretical significance and potential applications.Effects of various Schiff base ligands on the catalytic activity of CuCl in the oxidative carbonylation of methanol was studied and discussed in this article. The CuCl/Phen catalyst had the highest activity and the yield of dimethyl carbonate increased three times compared with pure CuCl catalyst. The effects of various Schiff base ligands on the catalytic activity of CuCl in the oxidative carbonylation of ethanol were subsequently explored, and the CuCl/Phen/NMI was the best one among these catalysts. The reaction conditions (catalyst concentration, reaction temperature, etc.) were investigated and the kinetic equation was also established according to the experiment datas. The results indicated that the conversion of ethanol could reach to 15.2% and the selectivity of diethyl carbonate could exceed 99.0% under the optimum condition:. the CuCl concentration of 0.2 mol/L, ligand and CuCl molar ratio of 2:1, reaction temperature 393 K, reaction pressure 2.4 MPa, CO and O2 partial pressure ratio of 2:1, reaction time of 3 h. The yield of diethyl carbonate with CuCl/Phen/NMI catalyst increased to 3.5 times as that of CuCl catalyst. The reaction kinetics with CuCl/Phen/NMI catalyst for the synthesis of diethyl carbonate was investigated. The kinetic equation is and the activation energy Ea is 53.4 kJ/mol.Heterogeneous catalytic systems have many advantages compared with homogeneous system in liquid-phase reactions, including easy separation of catalysts from reaction mixtures and low corrosion rate of catalysts. Preparation of organic-inorganic hybrid material (OIH) supported CuCl catalysts by sol-gel technology was further explored. A novel CuCl/Schiff base/OIH supported catalyst with 7.1 wt%Cu loading was synthesized by y-chloropropyltriethoxysilane(CPTES) as a spacer,5-amino-1,10-phenanthroline (NH2-Phen) as an organic ligand and tetraethyl orthosilicate(TEOS) as a silica source of OIH. The structure of intermediates and supported catalyst were characterized by EA, FT-IR and NMR (1H NMR,29Si-MAS-NMR). The effects of preparation conditions on the synthesis of OIH were investigated. The optimum preparation conditions were:the concentration of NH2-Phen 10 mg/ml DMF, molar ratio of TEOS and CPTES to NH2-Phen 6:1.1:1, reaction temperature 343 K, reaction time 72 h. The catalytic activity of CuCl/Schiff base/OIH in the oxidative carbonylation of methanol was studied. The yield of dimethyl carbonate with CuCl/Schiff base/OIH supported catalyst increased 25.0% compared with CuCl catalysts under the reaction conditions of CuCl concentration 0.1 mol/L, reaction temperature 393 K, reaction pressure 2.4 MPa, CO and O2 partial pressure ratio of 2:1, reaction time 2 h. After recycling 5 times, the catalytic activity remained with a average Cu loss rate of 2.2%. These results indicated CuCl/Schiff base/OIH catalyst was superior in the thermal stability and Cu loss rate.The stability of CuCl/Phen catalyst in oxidative carbonylation of methanol was tested in a batch reactor under the condition of 393 K and 2.0MPa. The lifetime of CuCl/Phen catalyst was more than 330 h. The chemical structure of the catalyst used before and after 330 h in the reaction were characterized with EA, XPS, XRD, TG-DTA, AAS. The reason for the deactivation of CuCl/Phen catalyst was the loss of chlorine and the disproportionation of Cu(Ⅰ). The deactivation mechanism of CuCl/Phen catalyst in the oxidative carbonylation was also discussed.Effects of Schiff base ligands on the corrosive performance of CuCl catalyst in the homogeneous oxidative carbonylation of methanol were also discussed. The inhibition effect of Schiff base ligands with CuCl on the alloy material in oxidative carbonylation system was studied by the weight loss method. The results showed that the ligands with CuCl catalyst system had obvious inhibition effect on the corrosive of alloy. On the conditions of [CuCl]=0.2 mol/L, [Phen]=0.1 mol/L, [NMI]=0.1 mol/L, the inhibition efficiency of TK nickel-based alloys were 98.2%. The corrosion rate of 0.0152 mm/a on TK reached the corrosion resistance of four criteria. Furthermore, the corrosion phenomenon of the alloy materials under different conditions was studied by scanning electron microprobe analysis, combining with electrochemical measurements and oxidative carbonylation reaction mechanism. The corrosion mechanism of the nickel-based alloys in the oxidative carbonylation system and the inhibition mechanism of Schiff base ligands were proposed.更多还原