己二酸绿色催化合成的动力学研究

【作者】 高敬铭；

【导师】 王向宇；

【作者基本信息】 郑州大学 ， 物理化学， 2007， 硕士

【摘要】 己二酸是一种非常重要的脂肪族二元酸，工业用途广泛。现有的己二酸的工业生产中主要采用硝酸氧化工艺，该工艺产生了大量的N₂O、NO_x等有害气体和废酸液，造成了严重的环境污染。在环保压力日益增大的情况下，开发一种从源头上杜绝污染的绿色合成己二酸技术已成为化学领域中的一个重要课题。随着各种绿色合成己二酸技术的提出和深入研究，以绿色氧化剂H₂O₂催化氧化环己烯合成己二酸的技术受到了广泛的关注。在前人研究的基础上，我们实验室成功开发出一种以30％H₂O₂为氧化剂，以Na₂WO₄为催化剂前驱体，催化氧化环己烯合成己二酸的新工艺。该工艺完全去掉了相转移剂和有机配体，排除了杂质对产品纯度的影响，明显提高了环己烯氧化合成己二酸的一次分离结晶产率，我们还对催化剂的循环使用效果以及催化反应的放大效果进行了系统的研究。在这些研究成果的基础上，本论文对该动力学与反应机理进行了更加深入的考察和研究。1、反应热力学计算分析采用Gaussian03软件、查兰氏手册和基团加和法估算了主反应和可能发生的反应的热力学函数，从热力学上分析了反应进行的趋势，认为主反应在热力学上能够进行且有优势；采用Gaussian03软件计算了Noyori等提出的反应历程的每一步热力学函数，分析了其可行性。2、反应动力学及其机理研究研究反应过程中双氧水的动力学行为，实验考察了H₂O₂在不同酸度和不同温度反应体系中的反应动力学，认为在绿色合成己二酸过程中，H₂O₂在该反应体系中存在平行反应机理，同时发生两种反应，一是氧化环己烯，二是分解生成氧气，这两种反应存在竞争关系；在较低温度下，双氧水反应级数为零级当；pH=0.3、T=72℃时双氧水利用率最高，最有利于环己烯的氧化反应进行。实验考察了环己烯的动力学行为，求取了环己烯不同条件下的反应级数和反应速率常数。在pH=0.3的最佳反应条件下，环己烯的反应级数为2，反应活化能为95.628 kJ/mol。研究了产物己二酸的动力学行为，发现随着温度的升高，己二酸反应速率常数增大，反应级数也随之增大。最后提出涉及钨—二氧配合物催化剂的配位催化反应机理。更多还原

【Abstract】 Adipic acid is a very important dibasic acid and is widely used in industry. The main industrial production process of adipic acid is nitric acid oxidation process, which generates large volumes of N₂O, NOx, and other harmful gases and waste acid, causing serious environmental pollution. With the increasing of environmental protection pressure, the development of green synthesis process for adipic acid have become an important subject in chemical industry.With the green adipic acid synthesis technologies of adipic acid proposed and researched deeply, technology that hydrogen peroxide oxidize cyclohexene to synthesize adipic acid has been widely concerned. Based on the previous research, our lab successfully developed a new technology, in which cyclohexene was directly oxidized with 30% H₂O₂ in homogenous system, without organic solvent, ligands and phase-transfer agents. This technology was very simple and caused no environmental pollution, and the purity of adipic acid could be increased by this method. The recycle of catalyst and scale-up reaction were both studied. In this thesis, the reaction kinetics and mechanism were investigated deeply.1. Study on the reaction mechanismThermodynamic energy data of the main reaction and all the possible reactions was estimated with the Gaussian 03 program, Lange’s Handbook of Chemistry and the group adding method, meanwhile the tendency of each reaction was analyzed. The main reaction is prior to the others in thermodynamics. Then, thermodynamic energy data of each step of the proximate reaction path introduced by Noyori was calculated by the Gaussian 03 program in order to confirm its feasibility.2. Study on reaction kineticsThe reaction kinetics study of hydrogen peroxide under various acidic conditions and temperatures was performed. There was a parallel reaction mechanism in the green synthesis process of adipic acid, in which the hydrogen peroxide either oxidized cyclohexene or decomposed into water and oxygen, and the two reaction paths were competed with each other. The reaction order of hydrogen peroxide is 0 at low temperature.At pH = 0.3 and T = 72℃, utilization of hydrogen peroxide reached the maximum, which is the most favorable conditions to epoxidation of Cyclohexene.The kinetics behavior of cyclohexene under various acidity conditions and temperatures was studied, and the reaction order and rate constant was estimated. At pH = 0.3, which is the best reaction condition, the reaction order is the 2^nd and the activation energy is 95.628 kJ/mol.The kinetics behavior of adipic acid in the reaction was studied, too. As a result, both the reaction constant and the reaction order are increased as the temperature rises. Finally, we proposed coordination catalytic reaction mechanism that involved Tungsten-dioxygen complex catalyst.更多还原