Insights into the Reaction Network and Mechanism of Green Aerobic Oxidative Esterification of Methacrolein over Different Heterogeneous Catalysts

The oxidative esterification of methacrolein(MAL)is an important way to prepare high-valued methyl methacrylate(MMA),but this process is ultra-complex due to the high reactivity of both C=O and C=C bonds in MAL molecule.In order to further improve MMA selectivity,the reaction network and relevant mechanisms have been proposed and profoundly investigated in this paper.Five kinds of fundamental reactions are involved in this process,including(a)the acetal reaction;(b)the aerobic oxidation of hemiacetal;(c)the alkoxylation of C=C double bond;(d)the Diels-Alder reaction;and(e)the hydrogenation reaction of unsaturated double bond.Among them,the Diels-Alder reaction of MAL is non-catalyzed,and the Brönsted acid sites or the Lewis acid sites favor promoting acetal reaction of MAL with methanol,while the alkoxylation of C=C bond with methanol is enhanced under alkaline condition.In particular,by employing the Pd-based catalysts,hydrogenation products are formed in alkaline methanol solution,hence with lower than those obtained by the Au-based catalysts.Notably,it is necessary to match the hemiacetal fromation and aerobic oxidation of hemiacetal,which is relevant with the amount and strength of acid and redox sites.Consequently,this work can provide a good guidance for the further design of both catalysts and processes in future.

Esterification by the Plasma Acidic Water:Novel Application of Plasma Acid

This work explores the possibility of plasma acid as acid catalyst in organic reactions. Plasma acidic water was prepared by dielectric barrier discharge and used to catalyze esterification of n-heptanioc acid with ethanol. It is found that the plasma acidic water has a stable and better performance than sulfuric acid, meaning that it is an excellent acid catalyst. The plasma acidic water would be a promising alternative for classic mineral acid as a more environment friendly acid.

Adiabatic correction for the esterification of acetic anhydride by methanol via accurate kinetics

In the field of adiabatic correction for complex reactions,a simple one-stage kinetic model was used to estimate the real reaction kinetics.However,this assumption simplified the real process,inevitably generated inaccurate or even unsafe results.Therefore,it was necessary to find a new correction method for complex reactions.In this work,esterification of acetic anhydride by methanol was chosen as an object reaction of study.The reaction was studied under different conditions by Reaction Calorimeter(RC1).Then,Thermal Safety Software(TSS)was used to establish the kinetic model and estimate the parameters,where,activation energies for three stages were67.09,81.02,73.77 kJ?mol^(-1)respectively,and corresponding frequency factors in logarithmic form were 16.05,19.59,15.72 s^(-1).In addition,two adiabatic tests were performed by Vent Sizing Package2(VSP2).For accurate correction of VSP2 tests,a new correction method based on Enhanced Fisher method was proposed.Combined with kinetics,adiabatic correction of esterification reaction was achieved.Through this research,accurate kinetic parameters for a three-step kinetic model of the esterification reaction were acquired.Furthermore,the correlation coefficients between simulated curves and corrected curves were 0.976 and 0.968,which proved the accuracy of proposed new adiabatic correction method.Based on this new method,conservative corrected results were able to be acquired and be applied in safety assessment.

Insight into the green route to dimethyl succinate by direct esterification of bio-based disodium succinate using CO_(2)and CH_(3)OH

The fermentation for succinic acid production outperforms other methods by low energy consumption and environmental benignity,with the resulting products mainly as disodium succinate(DSA).By directly esterifying DSA using CO_(2) and CH3OH,it is expected to avoid the use of inorganic acids.By high-resolution mass spectrometry analysis and theoretical calculation,this study establishes that the reaction consists of three steps,i.e.,first forming 3-carboxypropanoate,then monomethyl succinate(MMS),and finally dimethyl succinate(DMS).A detailed kinetic analysis is further performed,the results demonstrate that the transformation of DSA to MMS is regarded to be a second-order reaction for reactant DSA,while the transformation of MMS to DMS is a first-order reaction for reactant MMS.The activation energy for the generation of MMS from DSA is 37.15 kJ·mol^(-1),and that for the generation of DMS from MMS is 85.80 kJ·mol^(-1),indicating the latter one is the rate-determining step.

Kinetics and Mechanism of the Uncatalyzed Esterification of Acid-Rich Oil with Glycerol

In this paper, non-catalytic high temperature deacidification process of glycerol rich in acid oil was studied. Through orthogonal experiment, the primary and secondary order of influencing factors was temperature, glycerol dosage and reaction time, and the optimal process conditions were further verified: The ratio of fatty acid to glycerol is 1:1.2, the reaction temperature is 240°C, and the acid value can be reduced to 1.66 mg KOH/g for 2 h. In addition, the activation energy of the reaction was 54.93 kJ/mol by kinetic study. Combined with the K1 value of each reaction, it was confirmed that the temperature rise was conducive to the progress of the reaction. Finally, the high temperature ionization theory of glycerol is put forward, and the mechanism of auto-catalyzed deacidification reaction of glycerol is deduced by using this theory. This theory not only explains this study, but also perfectly explains the slow reaction time of low glycerol dosage.

Hierarchically ordered porous carbon with atomically dispersed cobalt for oxidative esterification of furfural

Nitrogen-rich zeolitic imidazolate frameworks(ZIFs)are ideal precursors for the synthesis of metal single atoms anchored on N-doped carbon.However,the microporous structures of conventional ZIFs lead to low mass transfer efficiency and low metal utilization of their derivatives.Here,we construct a composite of Co single atoms anchored on nitrogen-doped carbon with a three-dimensional ordered macroporous structure(Co-SA/3DOM-NC)by two-step pyrolysis of ordered macro/microporous ZnCo-ZIF.Co-SA/3DOM-NC shows high activity in the oxidative esterification of furfural,achieving a 99%yield of methyl 2-furoate under mild reaction conditions,which is significantly superior to the microporous and the Conanoparticle counterparts.The high activity of Co-SA/3DOM-NC should be attributed to the CoN4 centers with high intrinsic activity and the ordered macroporous structure,promoting the mass transfer of reactants and accessibility of active sites.

Direct Three-Component Synthesis of a-Cyano Acrylates Involving Cascade Knoevenagel Reaction and Esterification

A direct three-component approach has been developed for the synthesis of a-cyano acrylates starting from al- dehydes, alcohols and a-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structur- ally diverse a-cyano acrylates have been provided with good to excellent yields via the cascade transformation of Knoevenagel condensation and amide esterification.

Reaction Kinetics of Biodiesel Synthesis from Waste Oil Using a Carbon-based Solid Acid Catalyst

The kinetics of simultaneous transesterification and esterification with a carbon-based solid acid catalyst was studied.Two solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt.These catalysts were characterized on the basis of elemental analysis,acidity site concentration,the Brunauer-Emmett-Teller（BET）surface area and pore size.The kinetic parameters with the two catalysts were determined,and the reaction system can be described as a pseudo homogeneous catalyzed reaction.All the forward and reverse reactions follow second order kinetics.The calculated concentration values from the kinetic equations are in good agreement with experimental values.

Imidazolium ionic liquid-supported sulfonic acids:Efficient and recyclable catalysts for esterification of benzoic acid

Several imidazolium ionic liquid（IL）-supported sulfonic acids with different anions,[C_3SO_3Hmim]HSO_4,[C_3SO_3Hmim]BF_4, [C_3SO_3 Hmim]PF_6,and[C_3SO_3Hmim]CF_3SO_3,were synthesized and applied as catalysts for esterification reaction of benzoic acid. The experimental results indicate that imidazolium IL-supported sulfonic acid containing anion of HSO_4^- shows the best catalytic activity.Only when less[C_3SO_3Hmim]HSO_4（0.3 equiv.） applied,was the product obtained with high yield of 97%.Furthermore, the produced esters could be separated by decantation,and the catalyst could be reused after the removal of water.

邻叠氮苯甲酸的“一锅法”合成及其酯化反应

邻叠氮苯甲酸是一类有机合成中常用的原料和反应中间体。以六甲基磷酰胺(HMPA)为溶剂,邻硝基苯甲醛通过叠氮化反应转化为邻叠氮苯甲醛中间体。以新制的氧化银为氧化剂,邻叠氮苯甲醛中间体一锅法室温氧化得到相应的邻叠氮苯甲酸。2-叠氮苯甲酸的酰基化中间体后可顺利转化为酯类化合物,其中的邻叠氮苯甲酸丙酮醇酯经过斯陶丁格/N-维悌希反应环化得到2-甲基-3H-苯并[e][1,4]氧杂环戊烯-5-酮。

一种拉帕替尼衍生物的合成及抗HER2阳性乳腺癌作用研究

目的合成一种拉帕替尼的衍生物,探讨其抗HER2阳性乳腺癌的作用和作用机制。方法以阿司匹林为酰化试剂,应用Steglich酯化反应,经DCC-DMAP催化合成了乙酰化拉帕替尼(化合物Ⅰ)。应用CCK8及平板克隆法考察化合物Ⅰ抗HER2阳性乳腺癌细胞增殖的能力,采用分子对接技术预测化合物Ⅰ的作用靶点,通过Western blot法揭示化合物Ⅰ对BT474细胞AMPK/mTOR通路蛋白的影响。结果化合物Ⅰ的结构经1H NMR、13C NMR和MS确证。化合物Ⅰ对BT474细胞的IC50分别为(112.05±3.21)nmol·L^(-1)(24 h)、(35.87±0.79)nmol·L^(-1)(48 h)和(4.98±0.05)nmol·L^(-1)(72 h);化合物Ⅰ可显著抑制BT474细胞的克隆形成;分子对接结果显示化合物Ⅰ与EGFR、HER2、AMPK、mTOR和AKT1均有较好的结合;Western blot结果显示化合物Ⅰ可显著上调p-AMPK、AMPK,且激动作用较拉帕替尼更强,化合物Ⅰ亦可显著下调EGFR、HER2、p-AKT1、AKT1、p-mTOR和mTOR。结论化合物Ⅰ较拉帕替尼有更强的抗HER2阳性乳腺癌增殖活性,其主要通过激动AMPK,抑制AKT1和mTOR,调节AMPK/mTOR通路发挥作用。

氯化胆碱改性聚酰胺纳滤膜的制备与分离性能

为了提高传统聚酰胺纳滤膜的分离性能,利用酰氯与羟基之间的酯化反应将带有正电荷的季铵盐氯化胆碱(CC)引入聚酰胺纳滤膜表面,制备在中性条件下具有近中性荷电性的氯化胆碱/聚酰胺纳滤膜,通过对无机盐的分离测试考察了CC质量分数对薄膜复合(TFC)膜性能的影响。结果表明,当CC质量分数达0.10%时,改性效果最佳,TFC膜对Na_(2)SO_(4)、MgSO_(4)和MgCl_(2)均具有较高的截留率,具有改善的Mg^(2+)/Li^(+)分离能力,渗透通量提升了315%。

纳米炭黑的Steglich酯化反应制备及乙二醇分散性

为解决炭黑在乙二醇溶液中难分散的问题,确保炭黑在聚酯纤维原液着色中具有良好的分散性。先通过液相氧化法对炭黑表面进行改性,在炭黑表面引入反应性基团—羧基,并选取合适的氧化炭黑,通过Steglich酯化反应在氧化炭黑表面接枝乙二醇和不同相对分子质量的聚乙二醇。对氧化炭黑和接枝炭黑的表面结构以及在乙二醇溶液中的分散性进行测试与分析。结果表明:氧化仅发生在炭黑表面并未对炭黑造成严重破坏,随氧化时间的延长,炭黑表面羧基含量显著提高,氧化8 h后,其表面羧基含量为0.616 mmol/g;PEG600接枝的氧化炭黑其接枝率在33%以上,最小平均粒径稳定在132.1 nm左右,其能在乙二醇溶液中分散均匀,无聚集体出现,且制备的接枝炭黑具有良好的分散稳定性,其储存稳定性在93%以上,耐热稳定性在92%以上。

纳米蒙脱土复合改性酯化淀粉及其性能研究

淀粉具有独特的束簇凝聚态结构,分子主链上存在大量的羟基,强烈的分子间氢键限制了分子链的自由运动,使得天然淀粉很难直接进行热塑性加工,为了改善淀粉的加工性,本文采用不同比例乙酰乙酸叔丁酯(t-BAA)与淀粉在二甲基亚砜(DMSO)为溶剂的条件下进行酯交换反应,引入乙酰乙酸基弱极性基团改性淀粉的羟基,以减弱淀粉分子之间的强氢键作用。进一步通过纳米改性蒙脱土(MMT)的加入,使得酯化淀粉的热稳定性得到进一步提升,结果表明:得到了取代度在0~1.57的酯化淀粉,并且成功将蒙脱土的层间距从1.53 nm扩大到2.02 nm,甚至呈现出部分剥离状态,且在不添加增塑剂的情况下实现热塑性加工并降低了其亲水性。

丁香酸多孔淀粉酯的制备与表征

以马铃薯多孔淀粉(porous starch,PS)为材料,制备具有较好溶解性和抗氧化性的丁香酸多孔淀粉酯(syringic acid porous starch ester,SA@PS)。实验通过N 2-吸/脱附、扫描电镜、傅里叶变换红外光谱、液态核磁等方法,研究了SA@PS的特性。结果表明,以PS(比表面积14.69 m^(2)/g)为主体,可制备取代度为0.06~0.25的SA@PS;傅里叶变换红外光谱和液体核磁共振氢谱证明SA和PS之间形成了酯键;X射线衍射表明酯化反应改变了淀粉的结晶类型;SA@PS具备较强的抗氧化活性,可用于光、氧化或高温敏感分子的保护材料。

基于亚磷酸自催化的含磷季戊四醇酯润滑油的合成和性能

以季戊四醇与亚磷酸、脂肪酸为原料,采用两步法合成工艺制备了含磷季戊四醇酯,利用FTIR、NMR及元素分析对其结构进行表征,并对其高温稳定性进行评价。实验结果表明,第一步酯化反应在170~185℃下,无催化剂的体系反应效果与硫酸催化反应体系接近且优于氧化亚锡体系,说明亚磷酸在反应体系中既作底物,同时又起到了催化作用;第二步酯化反应在220~230℃下,无催化剂的亚磷酸体系与表现最佳催化效果的氧化亚锡体系的反应效果相当,进一步说明亚磷酸具有良好的自催化能力。与未进行亚磷酸改性的季戊四醇酯(典型的MIL-PRF-23699规范基础油)相比,含磷季戊四醇酯润滑油的分解温度提升约76℃,HPDSC氧化温度提升约25℃,表明亚磷酸改性可很好地提升季戊四醇酯润滑油的高温性能,使其在高温领域的应用得到拓展。

凝胶树脂负载离子液体固体酸催化酯化反应性能

针对酯化反应传统浓硫酸催化剂易腐蚀和产生大量含酸废水难题,通过一锅法将离子液体负载于凝胶树脂上,制备了绿色高效的凝胶树脂负载离子液体固体酸(SA-ILs)催化剂。研究表明:凝胶树脂载体具有强吸水结构,离子液体通过化学键共价负载在凝胶树脂载体上,SA-ILs催化剂具有优异的酸性和良好的结构稳定性。当离子液体为最佳载量11%时,合成的SA-ILs催化剂酸密度达3.25 mmol·g^(-1),对乙酸和乙醇之间的酯化反应具有良好的催化性能,乙酸乙酯的收率可达81%,并且循环复用5次使用后催化性能没有明显下降,而其较低的活化能是催化酯化反应更易进行的关键。

正交法设计乙酸甲酯制备的教学实验

介绍了应用正交法设计乙酸甲酯制备教学实验的方法,分析了醇酸摩尔比、催化剂用量、分馏柱长度这三个因素对乙酸甲酯收率的影响,筛选出制备的最佳实验条件为醇酸摩尔比为1.3∶1,催化剂用量为1.5 mL,分馏柱长度30 cm,实现以较少的试验次数达到与全面试验相近的结果。在化学实验教学时,将实验操作训练与数据处理知识相结合,不仅提高了学生的学习兴趣,还让他们更好地理解实验设计思想,培养了他们分析问题和解决问题的实践能力和创新能力,取得了良好的教学效果。

HBeta沸石高效催化芳醇/酚酯化

将自制的HBeta用于催化4-甲基苯甲醇与乙酸酐的酯化反应,确定了其最优条件为:以10 mg酸性HBeta沸石为催化剂、0.5 mmol 4-甲基苯甲醇、0.5 mmol乙酸酐、1.0 mL环己烷,N_(2)氛围下室温反应1 h,在该条件下以>99%的产率合成了乙酸4-甲基苄酯。探索了底物的普适性,并以较广的底物范围合成了32种芳香族酯化反应产物。在沸石中掺入不同质量分数的磷(0.2%~1.0%),通过XRD、N_(2)吸附-脱附、NH_(3)-TPD、Py-IR对催化剂的织构参数和酸性特征进行了表征。结果表明,随着HBeta强Br?nsted酸酸性位点(SBAS)酸量的降低,芳醇/酚酯化反应产率从>99%逐渐降至57%,说明催化剂上的SBAS是芳醇/酚反应的活性中心。此外,HBeta催化剂在芳醇/酚的酯化反应中表现出良好的结构稳定性,循环4次而没有明显失活。提出了4-甲基苯甲醇在催化剂的SBAS上首先转化成对应的碳正离子中间体,随后与乙酸酐发生亲核加成反应,从而生成目标产物的反应机理。

PEW-g-MAH改性竹粉机理研究

研究了PEW-g-MAH改性竹粉的机理,借助傅立叶红外光谱、热重分析、差示扫描量热法来探究PEW-g-MAH与竹粉的反应机理。结果表明,PEW-g-MAH中的酸酐基与竹粉中的羟基发生酯化反应,改性后的竹粉热稳定性增加,竹粉与PEW-g-MAH发生了化学键结合。