旋光法测蔗糖水解反应k实验类型的教学设计

蔗糖水解反应速率常数测定是典型的一级反应动力学实验,是物理化学实验的基本内容之一,针对实验中出现的问题,通过改进实验内容与操作方法,对旋光法测蔗糖水解反应k实验类型进行了重新设计,把过去单纯的验证型实验转变为验证型(新设计)、综合型、设计型、研究创新型、开放型和虚拟仿真型实验,进一步优化实验项目,启迪学生科学的思维方法与创新意识,形成了以自主式、合作式、研究式为主的学习方式,提高了学生实践创新能力。     

明胶的酸水解反应动力学研究 Ⅱ.动力学规律和机理

根据文献的实验数据,计算了明胶的柠檬酸水解反应的反应级数、表观反应速率常数、表观活化能和指前因子等动力学参数,得到了反应速率方程式。并求得实验温度范围内的反应速率常数与温度的关系,符合Arrhenius公式。对明胶的酸催化反应机理进行了探讨,推得的机理动力学方程和实验结果相符合。     

蔗糖水解反应速率测定实验设计的改进

蔗糖水解反应速率测定实验是大学《物理化学实验》有动力学章节一个重要实验,考虑到反应温度及催化剂的浓度对反应速率的影响,增加相关的实验内容,即改变实验的温度和催化剂的浓度取得相关数据。这样便于学生对不同温度和催化剂的浓度条件下得到实验结果进行对比,有利于培养学生独立思考的能力。     

苯酐水解速率实验测定

对邻苯二甲酸酐水解反应动力学进行了研究.在线测定了溶液中pH值的变化,根据pH值与溶液浓度之间一一对应的关系,得到苯酐在水解过程中邻苯二甲酸浓度的变化.由水解结束时溶液的平衡浓度与此时溶液的pH值,计算了不同温度下邻苯二甲酸的一级电离常数Ka,从而确定了水解反应级数α和不同温度下反应速率常数k.得到以下结论:随着温度的升高,水解速率常数也随之增加.根据阿伦尼乌斯方程,求得了水解反应的活化能Ea为9.45 kJ/mol、指前因子A为2.30.     

蔗糖水解速率常数测定实验教学内容的改进

旋光度法测定蔗糖水解速率常数是大学物理化学实验中最常见的实验项目之一。本文对该实验项目的教学内容进行了深入讨论,充分利用实验数据,获得了该反应的正、逆反应速率常数及反应平衡常数的计算,拓展了化学反应动力学相关的微观认识。     

双参数拟合法测定蔗糖水解速率常数

应用Origin2020b软件对"蔗糖水解反应速率常数的测定"的数据进行双参数拟合。结果表明:双参数拟合法不仅快捷方便获得了准确的、可靠的实验结果,直观的图形,还可以有效消除人为误差,节省时间,而且可以获得更多的统计信息量,这为客观评价学生的实验结果提供了依据。解决学生数据处理与绘图难的问题,从而提升学生的数据处理与数据分析问题的能力。     

乙酸乙酯在水玻璃溶液中的水解反应研究

研究了乙酸乙酯在ＳｉＯ２浓度为１．０ｍｏｌ·Ｌ－１的水玻璃溶液中的水解反应。分析讨论了水玻璃溶液中乙酸乙酯水解反应的特点,并通过气相色谱分析测定乙酸乙酯水解生成乙醇的量,计算了不同反应温度下乙酸乙酯水解反应的速率常数,求得了水解反应的活化能     

酸催化蔗糖水解的动力学研究

利用旋光度与蔗糖反应体系浓度的关联,研究了盐酸、硫酸、磷酸、醋酸等不同酸催化剂以及不同浓度的盐酸在不同温度下对蔗糖水解反应速率的影响。结果表明,不同酸催化剂对蔗糖水解起催化作用的是氢离子;[H]+从3 mol/L变化到4 mol/L时,蔗糖水解反应从一级反应近似转变为二级反应;催化剂降低了反应的活化能,加快了反应速率;酸催化蔗糖水解最佳条件是盐酸,浓度为3 mol/L,反应温度为45℃。     

蔗糖水解反应动力学研究

考察了蔗糖水溶液的浓度及反应温度对蔗糖水解反应的影响。结果发现，在浓度比较低的情况下蔗糖水解反应能很好的遵循一级反应的动力学方程，但在浓度较高时却与一级反应的速率方程有较大的偏离，说明此时该反应已不再是一级反应。这与理论分析结果相一致；另外随着反应温度的升高，该反应的速率随之增大，并且速率系数与温度的关系遵循阿仑尼乌斯方程。     

微波辐射对蔗糖水解反应指前因子影响的研究

文献上对于微波辐射是否影响阿氏方程指前因子项有不同见解,因此目前需要累积更多的实验素材。也有蔗糖溶液经微波辐射前处理可加速水解的报道。为累积实验数据,研究了油浴和微波两种供能方式下蔗糖的水解反应速率常数(k);结果表明:在较低的微波辐射能量密度(ED)水平下两种供能方式的k没有显著的差异;在较高的ED水平下k有所提高。反映出能量密度确实影响蔗糖水解的阿氏方程的指前因子项,而且能量密度对指前因子项的影响存在阈值。     

Stability of sucrose fatty acid esters under acidic and basic conditions

The stability of sucrose fatty acid monoesters toward hydrolysis under acidic and basic conditions was evaluated. Mass spectrometric analysis of hydrolysates showed that the glycosidic bond was preferentially hydrolyzed under acidic conditions, whereas the ester bond was selectively hydrolyzed under basic conditions. Under both conditions, the rate of hydrolysis depended on the pH of the solution, the concentration of sucrose monoesters, and the acylated position of the sucrose monoesters. The hydrolysis of the glycosidic bond under acidic conditions was shown to be a first-order process. The rate constants for hydrolysis at various temperatures were measured, and the activation energies were calculated from the slope of the Arrhenius plots. The lifetime of sucrose monoesters estimated from the first-order rate constant for the hydrolysis reaction revealed that the sucrose monoesters have excellent long-term stability over a pH range of 5 to 7 at room temperature.     

Kinetic analysis for effect of initial substrate concentration on growth and secondary metabolite production in cultures of Nicotiana tabacum

Suspension cultures of tobacco cells were studied using airlift and rotary-drum bioreactors. The effect of initial concentrations of a major substrate, sucrose, on the growth and production of a secondary metabolite, phenolic compounds, was investigated. The dry weights and total concentrations of the phenolic compounds increased with the initial sucrose concentration in both bioreactors. Both bioreactors were found to have the same tendency for the effect of initial sucrose concentration. The structured model, presented previously was modified by considering that sucrose was hydrolyzed to glucose and fructose by an enzymatic reaction. The previous and the new models were applied to the above two sets of experimental data obtained with two bioreactors, independently. The hydrolysis of sucrose was elucidated to contribute slightly to the overall kinetics of growth and secondary metabolite production in these cultures. Furthermore, the levels of shear damage in each bioreactor were quantitatively compared based on the death rate constant, k_i, which is one of the model constants.     

Green Medium for the Hydrolysis of 5‐Cyanovaleramide

Hydrolysis of 5‐cyanovaleramide (5‐CVAM) in near‐critical water without the addition of any catalyst has been demonstrated. The results demonstrated that the cyano group at one end of the carbon of 5‐CVAM is more reactive than the amide group at the other end, under the same experimental conditions. The relations between 5‐CVAM concentration and residence time revealed that hydrolysis of 5‐CVAM shows second‐order reaction kinetics in the investigated temperature range. The rate constants, average apparent activation energy and pre‐exponential factor were evaluated according to the Arrhenius equation. Based on the experimental results, a carbon balance was calculated, and a hydrolysis reaction scheme of 5‐CVAM was proposed.     

分子筛催化葡萄糖水解的宏观动力学

分别采用硅铝比为20~25和30的两种ZRP-5分子筛催化剂研究不同温度下葡萄糖水解动力学。研究结果表明,葡萄糖水解属于一级反应,反应温度显著地影响葡萄糖的转化。在相同反应温度下,前者作用下葡萄糖水解的表观反应速率常数大于后者。前者作用下葡萄糖水解的表观活化能为99.24 kJ/mol,后者作用下葡萄糖水解的表观活化能为108.99 kJ/mol。该反应动力学方程的葡萄糖水解转化率计算值与实验值吻合较好。     

泰勒流反应器的流动及反应特性

利用由静态混合器、喷嘴和分气盒组成的新型布气装置在搅拌釜式反应器中诱导生成泰勒流,对反应器流动特性及反应特性进行了实验研究。结果表明,与常规搅拌釜式反应器相比,泰勒流反应器内物料流动更加接近于平推流流型,泰勒流的生成在反应器内构建出局部平推流区域,降低了物料返混程度。反应器反应性能因流动特性改变而得以增强,相同实验条件下,在泰勒流反应器中进行的蔗糖水解反应转化率比在常规搅拌釜式反应器中高出26.7%。在一定操作范围内,局部平推流区域和反应转化率均随搅拌转速或进气量的增加而增大。泰勒流反应器可简化为平推流区和全混流区并联的流动模型,推导出了反应转化率与平推流区域占反应器总体积比率之间的关联关系。     

Auto-Catalyzed Hydrolytic Depolymerization of Poly(Butylene Terephthalate) Waste at High Temperature

Auto-catalyzed hydrolytic depolymerization of poly(butylene terephthalate) (PBT) waste in neutral water was carried out in an autoclave at 200°, 215°, 230°, and 245°C under autogenously pressure. The effects of particle size, agitator speed, charge ratio, and reaction time on PBT hydrolyses were studied. Reaction products were terephthalic acid (TPA) and 1,4-butanediol (BD) that were recovered, analyzed, and confirmed. Yields of TPA and BD were almost equal to PBT conversion. Analyses of PBT waste samples were also undertaken. A kinetic model for PBT hydrolysis was fitted with the experimental data. Moreover, a noncatalytic PBT hydrolysis was studied to understand the effect of auto-catalyzed action during reaction. Various kinetic parameters (i.e., hydrolysis rate constant, equilibrium constant, backward rate constant, Gibbs free energy, enthalpy, and entropy) of reaction were calculated. The transfer of laboratory data is required during process commercialization through pilot plant. The dependence of the rate constant on the reaction temperature was correlated by the Arrhenius plot giving activation energy of 87 kJ/mol and the corresponding Arrhenius constant of 5.56 × 10⁹[(g ET/mol)^1.5 min^?1] for PBT hydrolysis.     

近临界水中鱼肉水解制备氨基酸的反应动力学

利用鱼肉蛋白制备氨基酸不但具有经济效益,而且为生物质资源高效利用提供技术支持。采用HL-F(0.2 L+1.5 MG)/30 MPa-IIA超临界水反应装置,在无催化剂、反应温度分别为220,240,260℃,反应时间为30 min条件下,对鱼肉蛋白在近临界水中水解为氨基酸的反应动力学进行了实验研究。用AAA-Direct氨基酸分析仪测定不同反应时间中氨基酸总产率,以酸水解鱼肉蛋白得到的氨基酸量为完全水解标准。在水过量的情况下,得到了鱼肉蛋白水解率宏观反应动力学方程。结果表明鱼肉蛋白水解动力学的级数为1.614 7,220,240,260℃下的反应速率常数分别为0.001 7,0.004 5,0.009 7,活化能为145.125 kJ/mol,前置因子A为9.475 7×109,为工业化生产提供了基础数据。