乙二醇和丙三醇水溶液冻结特性的研究

利用差示扫描量热仪（Pyris-Diamond DSC），研究了乙二醇（甘醇）和丙三醇（甘油）水溶液的过冷行为、水合性质和它们的玻璃化转变温度及反玻璃化温度，分析了它们与分子中羟基个数的关系.进行了12组共24种不同浓度(质量分数）的溶液的差示扫描量热实验.过冷度的实验结果表明，在浓度相等的情况下，两种低温保护剂水溶液冻结的过冷度有相同的变化规律.水合实验的结果表明，浓度相同时，二者结合水的能力大体相当.玻璃化转变的实验表明，二者玻璃化转变温度与反玻璃化温度存在明显差异.     

1,2-丙二醇水溶液玻璃化转变与结构松弛

为了考察水含量对1, 2-丙二醇水溶液玻璃化转变和结构松弛参数的影响, 用差示扫描量热法(DSC), 测量了5种高浓度1, 2-丙二醇水溶液(60%、70%、80%、90%、100%, w)玻璃化转变区域的表观比热容. 用5种降温速率(1、2、5、10、20 K·min-1)和10 K·min-1的升温速率获得玻璃化转变的相关参数. 玻璃化转变温度分析结果表明, 虽然水含量增加能从总体上降低体系的玻璃化转变温度, 但与纯羟基类多元醇相比, 水对1, 2-丙二醇的增塑作用并不显著. 结构松弛活化能计算结果表明, 体系水含量的增加能明显降低结构松弛活化能. 脆度分析结果表明, 随着体系水含量增加, 动力学脆度逐渐降低, 但热力学脆度是先升高后降低, 在80%左右达到最大值. 结构松弛协同重排域计算结果表明, 当浓度由60%增加至100%时, 玻璃化转变特征长度由2.79 nm增加至3.57 nm.     

甘油水溶液氢键特性的分子动力学模拟

为了研究低温保护剂溶液的结构和物理化学特性, 以甘油为保护剂, 采用分子动力学方法, 对不同浓度的甘油和水的二元体系进行了模拟. 得到了不同浓度的甘油水溶液在2 ns内的分子动力学运动轨迹, 通过对后1 ns内运动轨迹的分析, 得到了各个原子对的径向分布函数和甘油分子的构型分布. 根据氢键的图形定义, 分析了氢键的结构和动力学特性. 计算了不同浓度下体系中平均每个原子(O和H)和分子(甘油和水)参与氢键个数的百分比分布及其平均值. 同时还计算了所有氢键、水分子之间的氢键以及甘油与水分子之间的氢键的生存周期.     

改善细胞通透性促进1,3-丙二醇生物合成

克雷伯杆菌发酵生产1,3-丙二醇(1,3-PD)的过程中, 通过加入表面活性剂可改善细胞通透性, 以减少产物和副产物对细胞生长与代谢的抑制作用, 从而促进细菌生长和1,3-PD产出. 对比研究了吐温-80 (Tween-80)、曲拉通X-100 (Triton X-100)、壬基酚聚氧乙烯醚-10 (OP-10)和十六烷基三甲基溴化铵(CTAB)等对发酵中甘油脱氢酶(GDH)、1,3-丙二醇氧化还原酶(PDOR)和甘油脱水酶(GDHt)等3种关键酶活的影响. 实验表明OP-10能较好改善细胞通透性, 胞内释放核酸浓度随添加OP-10量的增加有明显提高. 低浓度的OP-10对GDH, PDOR活性及细胞生长有较好的促进作用; 发酵8～12 h时添加1.0 g•L－1的OP-10可使1,3-PD浓度和摩尔转化率有较大提高. 结合透射电镜发现非离子表面活性剂OP-10损伤膜结构, 致细胞通透性改变, 有利于充分发挥细胞内酶的催化活性, 对细菌生长和1,3-丙二醇的合成有较大促进作用.     

1H NMR研究溶质浓度对三碳多元醇水溶液氢键作用以及玻璃化的影响

为考察溶质浓度对三碳多元醇水溶液氢键作用以及不同物质玻璃态形成能力的影响,采用¹H NMR外标法研究不同浓度的1-丙醇（NPA）,2-丙醇（IPA）,1,2-丙二醇（PG）,1,3-丙二醇（PD）和丙三醇（glycerol）的水溶液在室温常压下质子化学位移.结果表明:具有CH₃CH（OH）一基团的PG烷基质子的化学位移变化趋势与其他几种醇相比有较大差异.醇羟基质子与水分子的氧形成较强O-H…O氢键.相同摩尔分数下,羟基数的增加导致水质子和羟基质子的化学位移降低,而且羟基位置不同也会导致水质子和羟基质子化学位移差异.这几种三碳多元醇碱性强弱的顺序和降低冰的均相成核温度能力的顺序一致,即glycerol>PG>PD>IPA>NPA,¹H NMR技术表明glycerol和PG更适合用作低温保护剂.     

催化选择转化多羟基化合物制备高附加值化学品研究进展

对近年来催化转化多羟基化合物制备5-羟甲基糠醛、乙二醇、1,2-丙二醇、1,3-丙二醇等高附加值化学品进行了综述. 分析了果糖、葡萄糖、纤维素等不同结构的碳水化合物制5-羟甲基糠醛存在的挑战, 并对相应的解决方法进行了总结. 对于5-羟甲基糠醛的转化, 我们重点讨论了5-羟甲基糠醛选择性氧化制备2,5-二甲酰基呋喃和2,5-呋喃二甲酸以及它们作为聚合单体的潜在应用. 概述了催化氢解纤维素、糖醇、甘油等多羟基化合物制备乙二醇、1,2-丙二醇、1,3-丙二醇等二元醇的方法, 并对可能的机理进行了讨论. 依据近年来多羟基化合物催化选择性转化制备高附加值化学品的研究现状, 对今后的研究热点进行了展望.     

负载Pt-WOx催化剂上甘油选择氢解合成1, 3-丙二醇

甘油是重要的生物质基平台分子,可以从生物柴油生产过程中作为副产物大量获得。本文采用等容浸渍法,在氧化钛、三氧化二铝和氧化锆载体上制备一系列具有不同WO₃表面密度的负载Pt-WO_x催化剂,研究了它们在甘油选择氢解合成1, 3-丙二醇反应中的催化性能。实验结果表明,WO₃的表面密度显著影响这些催化剂的活性和1, 3-丙二醇选择性,它们均在1.5–2.0 W∙nm⁻²表面密度时表现出最优性能,表明分散的WO_x物种是影响Pt-WO_x催化剂性能的关键因素。通过原位红外CO吸附表征等方法发现Pt粒子与WO_x物种之间存在电荷转移和强相互作用,进而提高Pt-WO_x催化剂的甘油氢解转化为1, 3-丙二醇的活性。进一步比较甘油、1, 2-丙二醇和1, 3-丙二醇的氢解反应发现,1, 3-丙二醇的氢解速率常数低于甘油和1, 2-丙二醇,表明在Pt-WO_x催化剂上1, 3-丙二醇具有更高的反应稳定性,这跟Pt-WO_x催化剂具有较高的1, 3-丙二醇选择性相一致。结合氢气分压对甘油氢解活性表现出的火山型影响结果和在D₂/D₂O存在下,观察到的1, 3-丙二醇产物中仲碳与伯碳上的H原子数的比例(~1 : 2),我们推测在甘油氢解合成1, 3-丙二醇反应中,甘油首先在Pt-WO_x催化剂上脱氢生成甘油醛中间体,然后甘油醛进一步脱水和加氢转化为1, 3-丙二醇。     

基于修正的Mazur方程的细胞最优化低温保存方案理论预测

为了理论预测细胞最优化低温保存方案,提出了冷冻过程细胞内变组分、变温三元溶液系统的冰晶成核及其生长模型.数值模拟结果表明:(1)较高降温速率下,胞内冰体积份额随初始甘油浓度的增加呈线性减小.(2)实现溶液玻璃化的临界降温速率随初始甘油浓度的增加而减小:没有甘油存在时,1.25×1013℃/min;初始甘油浓度为7.4mol·L-1时,为20℃/min;当初始甘油浓度大于7.4mol·L-1时,所有降温速率均能达到玻璃化保存.本研究通过获得初始甘油浓度和降温速率二维平面图中可实现细胞内玻璃化的区域,从而提供了一种细胞最优化低温保存方案的理论预测方法.     

Ni/SiO_2催化剂的合成及其甘油氢解制1,2-丙二醇性能

以硝酸镍和偏硅酸钠为原料,采用并流共沉淀和氢气还原-钝化的方法制备了Ni/Si O2催化剂,通过BET、XRD、H2-TPD、NH3-TPD、HRTEM、XPS等手段对催化剂的理化性质进行了表征,发现合成得到的Ni/Si O2催化剂具有良好的织构性质、极高的金属分散度和活性比表面积,并且对甘油氢解生成1,2-丙二醇的反应表现出良好的活性和选择性.研究还考察了催化剂的镍硅比、反应停留时间、反应压力、甘油浓度对甘油氢解性能的影响,发现在镍硅比为0.5,反应停留时间为2 h,反应压力为5.5 MPa,甘油浓度为10%的条件下,甘油的单程转化率达78.8%,1,2-丙二醇的选择性高达92.9%.     

甘油催化氢解的研究与应用

近年来由于生物柴油产业的快速发展,甘油作为其生产过程中的副产品大量生成,合理利用这些过剩的甘油将有助于增加整个生物柴油产业的经济效益。本文对近年来利用甘油为原料催化氢解合成二元醇（1,2-丙二醇、1,3-丙二醇和乙二醇）的研究进展进行了综述,介绍了甘油催化氢解的研究背景,着重讨论了甘油催化氢解生成二元醇的反应机理（包括脱水-加氢机理、脱氢-加氢机理和螯合机理）和甘油催化氢解在生产二元醇上的应用,并对甘油催化氢解的发展前景做了展望。     

Enthalpy parameters of molecular interactions of dl-α-alanyl-dl-α-alanine with polyhydric alcohols in the aqueous solution

Russian Journal of General Chemistry - Integral enthalpies of dissolution Δsol H m of DL-α-alanyl-DL-α-alanine in aqueous solutions of glycerol, ethylene glycol, 1,2-propylene...     

Enthalpies of Mixing and State of Components in Aqueous-Organic Mixtures with Nets of Hydrogen Bonds

The enthalpies of mixing of water with glycerol over the entire composition range were determined at 298.15 K. The partial excess enthalpies of the components of mixtures of water with glycerol, ethylene glycol, 1,2- and 1,3-propylene glycol, and formamide were estimated and used for examining solvation and the state of water and the organic components in the solutions. The composition of the solvation shells of the components of the mixtures were shown to depend on the nature and structure of the organic solvent.     

Rapid determination of ethylene glycol at toxic levels in serum and urine

The rapid gas chromatographic detection and determination of ethylene glycol in biological fluids is described. Phenylboronic acid in acetone was used for the esterification of glycol. The phenylboronates of ethylene glycol and 1,2-propylene glycol are not separated on a packed column of medium polarity (OV-17), but they can be separated on a non-polar column (OV-101). In both instances, 1,3-propylene glycol can be used as an internal standard. The method requires only 100 microliters of serum or urine and is suitable for trace analysis in an emergency toxicological laboratory. The utility of the method is demonstrated on two cases of human intoxication with ethylene glycol.     

Analysis of mixtures of glycols by ion-exchange chromatography

Procedures and results of the anion-exchange separation of diethylene glycol, ethylene glycol, 1,2-propylene glycol, the meso and the dl isomers of 2,3-butylene glycol, and glycerol are reported. This separation allows the determination of each of the six compounds present in the mixture by oxidation with dichromate.     

Effect of the composition of aqueous-organic mixtures on the sensitivity of thermal lens measurements

Thermooptical properties of aqueous solutions of methanol, acetonitrile, dimethyl sulfoxide, ethylene glycol, glycerol, 1,4-dioxane, and sucrose were studied, and it was found that the analytical thermal lens signal depends on the nature of the organic component, most of all, on the polarity and molecular size. The sensitivity coefficient of thermal lens measurements is increased to a maximum extent in methanol solutions (by 7.3 times at the concentration 50 vol %) and acetonitrile (by 8.8 times at 26 vol %). It was found that a small concentration of water slightly affects the thermooptical properties of polar organic solvents.     

Stability of intermediates in the glycerol hydrogenolysis on transition metal catalysts from first principles

The hydrogenolysis reaction catalyzed by a transition metal solid catalyst is a potential way to transform glycerol to 1,2-propylene glycol or 1,3-propylene glycol, two important chemicals. We explore the thermodynamic profile of this reaction from first principle simulation, comparing Ni, Rh and Pd catalysts modeled by (111) surfaces. The stability of adsorbed reactants, dehydrated intermediates, and hydrogenated propylene glycol is compared, with a special focus on the factors controlling the selectivity of the reaction. From a global thermodynamic view point, the formation of 1,2-propylene glycol is favored, and in addition the most stable intermediates in the gas phase (acetol and 1,2-aldol) lead to the formation of this product. The metal catalyst has three roles. First it stabilizes the dehydrated intermediates and renders the dehydration more exothermic. Second, the adsorption on the surface modifies the relative stability of the dehydrated intermediates, with implications on the reaction selectivity. Third it catalyses the hydrogenation step, leading to propylene glycol.     

Molecular dynamics study of effects of temperature and concentration on hydrogen-bond abilities of ethylene glycol and glycerol: implications for cryopreservation

The state of intracellular water is important in all phases of cryopreservation. Intracellular water can be transported out of the cell, transferred into its solid phase, or blocked by cryoprotectants and proteins in the cytoplasm. The purpose of the present study is to determine the amount of hydrogen-bonded water in aqueous ethylene glycol and glycerol solutions. The effects of temperature and concentration on the density and the hydrogen bonding characteristics of the solution are evaluated quantitatively in this study. To achieve these aims, a series of molecular dynamics simulations of ethylene glycol/water and glycerol/water mixtures of molalities ranging from 1 to 5 m are conducted at 1 atm and at 273, 285, and 298 K, respectively. The simulation results show that temperature and concentration have variable effects on solution density. The proportion of the hydrogen-bonded water by solute molecules increases with rising molality. The ability of the solute molecules to hydrogen bond with water molecules weakens as the solution becomes more concentrated. Moreover, it turns out that the solution concentration can influence the hydrogen bonding characteristics more greatly than the temperature. The glycerol molecule should be a stronger "water blocker" than the ethylene glycol molecule corresponding to the same conditions. These findings provide insight into the cryoprotective mechanisms of ethylene glycol and glycerol in aqueous solutions, which will confer benefits on the cryopreservation.     

Preparation of N-phosphorylated 2-oxo-1,3-oxazolidines and 6-methyl-2-oxo-1,3-tetrahydrooxazine

Conclusions N-Phosphorylated 2-oxo-1,3-oxazolidines and 6-methyl-3-(diethoxyphosphinyl)-2-oxo-1,3-tetrahydro-oxazine were prepared by allowing N-(diethoxyphosphinyl)imidocarbonyl dichloride to react with ethylene glycol, 1,2-propylene glycol, and 1,3-butylene and 2,3-butylene glycols in the presence of triethylamine in a dioxane medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 396–399, February, 1970.     

Enthalpy pair coefficients of interaction for DL-valine in aqueous solutions of polyatomic alcohols at 298 K

Integral enthalpies of dissolution Δ_sol H ^m of DL-valine are measured via calorimetry of dissolution in aqueous solutions of glycerol, ethylene glycol, and 1,2-propylene glycol. Standard values of the enthalpies of dissolution (Δ_sol H ^○) and transfer (Δ_tr H ^○) of amino acid from water to mixed solvent are calculated from the resulting experimental data. The enthalpy coefficients for pair interactions h_xy of amino acid with polyatomic alcohol molecules are calculated using the McMillan-Meyer theory and have positive values. The obtained results are discussed in light of the theory of the predomination of various types of interactions in mixed solutions and the effect of structural features of interacting biomolecules on the thermochemical parameters of the dissolution of amino acids.