【作者】 杨艳；

【导师】 戴立益；

【作者基本信息】 华东师范大学 ， 物理化学， 2009， 博士

【摘要】 近临界水是近年来在绿色化学的理念下开发起来的新型介质与优良溶剂。近临界水与常温常压水相比突出的性能是电离常数大和介电常数小,因而近临界水具备自身酸碱催化功能和溶解有机物和无机物的特性。这些优异的性能使它在有机化学反应中可兼作反应物、催化剂和溶剂。其催化性能可使某些酸碱催化反应不必外加酸碱催化剂就能发生,避免了酸碱的中和、废弃盐的处理等工序。鉴于近临界水优良的传质性能和绿色环保的优点,其在有机化学反应、资源循环利用等领域具有潜在的应用研究前景。目前关于近临界水体系中有机合成反应的研究主要集中在以近临界水作为反应介质,并通过改变实验条件来实现,但对少量助剂的引入及助剂对反应的促进作用研究较少。因此根据特定的反应类型,有选择性地引入助剂,并研究不同种类的助剂对反应的影响,具有重要意义。研究过程可以通过探索近临界水这一介质与助剂、原料、产物之间的作用,揭示助剂对近临界水中有机合成反应的作用效果,优化近临界水中有机合成反应条件。以便寻找提高近临界水体系中有机合成反应应用价值的新途径,使近临界水能更好地应用于有机合成反应中,提高经济效益。基于上述想法,本论文选用三种典型二醇,其中包括连有相邻羟基的二醇（2,3-丁二醇）、两端基上连有羟基的二醇（1,4-丁二醇）和含杂原子的二醇（二甘醇）,分别研究了它们在近临界水中的脱水行为。向各反应体系引入不同助剂（酸性气体、水解呈酸性盐及水解呈碱性盐）,以研究近临界水中助剂对三种二醇脱水行为的影响。主要考察了近临界水体系中反应参数（反应温度,反应压力,反应时间、助剂、物料/水比及助剂/原料比）对二醇脱水的影响;考察了不同种类的助剂对醇脱水反应的影响;对醇脱水反应过程中的副产物进行了鉴定并对三种醇脱水机理进行了讨论;利用一级反应动力学方程对助剂存在下三种二醇脱水反应动力学进行了探讨,得到了醇在不同助剂存在下的反应活化能;利用量子化学的方法对二甘醇脱水环化过程进行了量化模拟研究。论文主要包括以下几个方面:1.近临界水体系中2,3-丁二醇脱水重排反应研究首次利用近临界水的特性在自行设计的高压反应装置中研究了2,3-丁二醇脱水重排反应,并向反应体系中引入酸性气体CO₂,以研究近临界水中CO₂对2,3-丁二醇脱水重排反应的影响。实验测定了温度在250～340℃,CO₂初始压力为0.4～5MPa之间,不同反应时间内2,3-丁二醇转化率和目标产物甲乙酮产率。对近临界水体系引入CO₂后pH值进行了计算,从理论角度验证了CO₂的促进作用;采用一级反应动力学方程对2,3-丁二醇脱水重排反应进行动力学拟合,得到了有、无CO₂引入状态下2,3-丁二醇脱水重排反应的动力学方程及表观反应活化能。结果表明引入CO₂,2,3-丁二醇脱水重排活化能为42.77kJ/mol,与无助剂时的活化能46.07 kJ/mol相差不大。2.近临界水体系中1,4-丁二醇脱水环化反应研究在近临界水体系中引入盐（Fe₂（SO₄）₃,ZnSO₄及NaHSO₄）,以考察不同助剂存在下,1,4-丁二醇脱水环化行为。测定了体系压力为18MPa,反应温度260～340℃,反应时间60～180min,物料/水质量比1∶10～1∶50下,各种助剂存在情况下,1,4-丁二醇转化率及四氢呋喃的产率,对比了不同助剂对1,4-丁二醇脱水环化反应的影响。实验表明,引入同浓度的助剂,Fe₂（SO₄）₃的促进作用最大。根据实验过程中收集到的动力学参数拟合得到了1,4-丁二醇脱水环化反应动力学方程和各助剂存在下1,4-丁二醇脱水环化的反应活化能。结果表明引入Fe₂（SO₄）₃为助剂时其反应活化能最小,为37.23kJ/mol。根据实验过程产物的检测,对1,4-丁二醇脱水环化可能的反应机理进行了探讨。3.近临界水体系中二甘醇脱水环化反应研究研究了近临界水体系中含杂原子的二醇——二甘醇脱水环化情况。考察了不同温度（250～360℃）、不同时间（60～240min）和不同助剂引入情况下,不同反应因素对二甘醇脱水环化反应的影响。利用动力学数据拟合得到该反应的反应动力学方程和不同助剂存在下二甘醇脱水环化反应活化能。利用正交试验设计方法优化了二甘醇脱水环化工艺过程,用统计分析的方法讨论了各不同因素影响的显著性,得出了经二甘醇脱水环化生成1,4-二氧六环最佳的反应条件:反应温度为360℃、反应时间为60min、物料/水比为1∶50、助剂/原料为1∶10、Fe₂（SO₄）₃作为助剂及体系反应压力为30Mpa,为二甘醇脱水环化工艺提供了理论依据。根据实验结果及实验过程中副产物的检测提出了二甘醇脱水可能的反应机理。4.二甘醇脱水环化反应量化模拟研究利用量子化学方法,模拟了二甘醇脱水环化反应历程,提出了三种不同脱水反应路径。使用密度泛函中B3LYP方法对各反应路径的反应物、产物、中间体及过渡态构型的在势能面上各驻点的几何构型进行全优化计算;并经振动频率分析确定了过渡态和中间体;通过内禀反应坐标（IRC）的计算,确认了反应物、中间体、过渡态和产物的相关性,得出最佳反应路径。结果表明经量化模拟所得最佳反应路径与经实验结果提出的反应机理相吻合。更多还原

【Abstract】 Recently,Near-critical water（NCW）has been gradually developed based on the arisen green chemistry and used as a new medium and an excellent solvent.The prominent properties of NCW is its high ionization constant and low dielectric constant as compared as the normal water,so that NCW has the characteristics of own acid-base catalytic function and the ability of dissolving organic and inorganic compounds.Those excellent properties make NCW used as catalyst in organic reaction as well as reactant and solvent.NCW is usually used as the reactant,medium and solvent in organic synthesis reaction because of its outstanding characters.Its catalytic performance allows certain acid/base-catalyzed reaction to be happened without additional of acid/base catalysts and avoids the neutralization of salt.The performances of excellent transfer and green environmental etc.of NCW have made its potential applied in organic reactions,waste recycling and other fields.Generally,the organic synthesis reaction would be initiated with the additives assisted.At present,the research of NCW is mainly focused on the use of NCW as the reaction medium and the effects of experimental parameters on the reaction,while the additional of some additives and the promotion effect of additives on the reaction in NCW are seldom considered.Introducing some additives to NCW system according to specific reaction type for purpose and researching the effect of additives on organic reaction are very meaning.In the processing,disclose the mechanism of reaction with additives and find out the optimal experimental condition by exploring the function principle relationship between characteristics of NCW,additives,reactant,and products and.In order to improve the application of NCW in organic synthesis reaction and make use of NCW for better economic results.Base on above ideas,three typical glycols,which are 2,3-butanediol,1,4-butanediol and diethylene glycol,are selected and studied the dehydration of them with additional of different additives in NCW.The work mainly includes the effect of reaction parameters（such as temperature,pressure,time reactant/water（r/w）ratio and additives/reactant（a/r）ratio）and the effect of additives on the dehydration of glycols; the possible by-products identification;the possible dehydration mechanisms of glycols;the kinetics of reaction based on the first order;the mechanism simulation of cyclo-dehydration of diethylene glycol based on the quantum research method.The details are given as follows:1.The rearrangement study of 2,3-butanediol in NCWThe rearrangement of 2,3-butanediol（BDL）after introducing CO₂ as the additives in NCW has been investigated for the first time by utilizing the high-pressure reactor designed by ourselves.Detecting the conversion of BDL and the yield of methyl ethyl ketone（MEK）at the temperature range of 250～340℃with different initial pressure of CO₂ in different time.In order to affirm the stimulative contribution of CO₂,the value of pH was calculated after introducing CO₂ in NCW.The reaction kinetics was fitted based on the first-order reaction.The activity energy（Ea）was calculated based on the experimental data.And the results demonstrated that the values of two Ea weren’t differential each other,which were 46.07 kJ/mol and 42.77kJ/mol without or with introducing CO₂,respectively.2.The dehydration study of 1,4-butanediol in NCWThe dehydration of 1,4-butanediol（BD）in NCW with additional of different additives,which are Fe₂（SO₄）₃,ZnSO₄ and NaHSO₄ have been investigated.The effects of different additives on the yield of target product tetrahydrofuran（THF）and the conversion of BD at the temperature range of 260～340℃,time of 60～180min and with r/w of 1:10～1:50 were studied.Ea was calculated based on the experimental data and the first-order reaction.The results showed Fe₂（SO₄）₃ had the prominent effect on the cyclo-dehydration of BD and the Ea was 37.23kJ/mol.The dehydration mechanism of 1,4-butanediol was proposed based on above results.3.The dehydration study of diethylene glycol in NCWThe dehydration of diethylene glycol（DEG）was studied at the temperature of 250～360℃and time of 60～240min after introducing different additives.The reaction kinetics was fitted based on the first-order reaction and the activity energy（Ea）was calculated base on the experimental data with different additives.The dehydration of DEG was researched by orthogonal array design（OAD）and the optimum cyclo-dehydration condition was reaction temperature of 360℃,time of 60min,r/w ratio of 1:50,a/r ratio of 1:10 and with Fe₂（SO₄）₃ as the additive.Based on the above results,the dehydration mechanism of DEG was proposed.4.The quantum simulation cyclo-dehydration of diethylene glycol The cyclo-dehydration of DEG was researched by the quantum simulation and the different reaction channels were proposed.The geometries of all species（reactant, intermediates,transition state,products）were optimized and the vibration frequencies were calculated by DFT/B3LYP.The relativities of all species were verified by calculating IRC and the optimum pathway was suggested.The results suggested that the optimal pathway by simulating was coincided with the reaction mechanism presented from the result of experiment.更多还原