Production of propylene glycol fatty acid monoesters by lipase-catalyzed reactions in organic solvents

Fatty acid monoesters of propylene glycol (1,2-propanediol) are good water-in-oil emulsifiers. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. APseudomonas lipase was added to reaction mixtures containing propylene glycol and various acyl donors (fatty acids, fatty acid ethyl esters, fatty acid anhydrides and triglycerides) in organic solvents, and the mixtures were shaken at 30°C. The products were analyzed by gas chromatography. The yield of monoesters was affected by the acyl donors, organic solvents, temperature, water content, pH memory and reaction time. The anhydrous (lyophilized) enzyme and fatty acid anhydrides were best for monoester production. The optimum pH ranges were 4–5 and 8–10. The yields of propylene glycol monolaurate, monomyristate, monopalmitate, monostearate and monooleate with 50 mM fatty acid anhydrides as acyl donors were 97.2, 79.6, 83.7, 89.7 and 93.4 mM, respectively; those with 50 mM fatty acids as acyl donors were 37.3, 28.7, 28.7, 35.3 and 36.2 mM, respectively. The yields of propylene glycol monopalmitate, monostearate and monooleate with 50 mM triglycerides as acyl donors were 87.4, 65.1 and 83.2 mM, respectively.     

Synthesis of propylene glycol monoesters of docosahexaenoic acid and eicosapentaenoic acid by lipase-catalyzed esterification in organic solvents

Propylene glycol monoesters (PGM) of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are potentially health-beneficial water-in-oil emulsifiers useful in the food industry. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. The products were analyzed by gas chromatography. The immobilizedMucor miehei lipase was found to be the best enzyme for the synthesis of both propylene glycol monoesters of EPA and DHA among nine lipases tested. The anhydrous enzyme and hydrophobic organic solvents were favored for the production of both monoesters. The yields of monoesters were also affected by temperature, pH memory, fatty acid/propylene glycol ratio, and reaction time. The yields of PGMDHA and PGMEPA with 50 mM fatty acid and 225 mM propylene glycol as substrates in 1 mL solvent mixture (hexane/t-butyl alcohol=9:1), catalyzed by Lipozyme IM-20 (50 mg) at 40°C for 24 h, were 47 and 49 mM, respectively. The enzyme still retained over 60% of its original activity after 10 d of batch-type operation (1 d per cycle) at 40°C for the synthesis of both PGMDHA and PGMEPA.     

Determination of diester formation in diethylene glycol and tetraethylene glycol monoesters

Polyethylene glycol monoesters on standing rearrange to form diesters. The formation of diester in monoester samples stored at 3 C, 25 C, and 37 C, respectively, for approximately 3 months was determined by reverse phase high performance liquid chromatography (HPLC) in less than one-half hour. Formation of diester increased with increasing storage temperature, regardless of the chemical nature of the     

Heterogeneous photocatalytic degradation of ethylene glycol and propylene glycol

The photocatalytic decomposition of ethylene glycol and propylene glycol was investigated by using UV-illuminated TiO₂ and metal-loaded TiO₂ catalysts. The effects of pH, initial concentration, and wavelength of light on the decomposition rate of the glycols were explored. Platinum-and palladium-loaded TiO₂ catalysts enhanced the rates of photodecomposition compared to unloaded TiO₂. The glycols were oxidized primarily to carbon dioxide and water. Formaldehyde was found to be an important reaction intermediate. A detailed chemical reaction mechanism for the destruction of ethylene glycol and propylene glycol in water via free radical pathway and trapped hole reactions at the particle surface is proposed.     

Clarification of propylene glycol monoester polymorphism

A minor revision based on new data is reported for the polymorphism of 1-propylene glycol monopalmitate and monostearate. Metastable Form I is now found to be intermediate in melting level between α and stable Form II. Form III as previously reported transforms to α below the α mp. For the 80:20 mix of 1-propylene glycol monostearate-2-propylene glycol monostearate, the approximate equilibrium mixture, it is again observed that Form II is stable, melting a little above α; and Form I transforms to α slightly below the α mp; and Form III is missing.     

丙烯酸聚乙二醇酯相变大单体的制备

以聚乙二醇(PEG)4000及丙烯酰氯为原料,采用酯化法合成了丙烯酸聚乙二醇酯(PEGA)相变大单体.利用红外光谱(IR)、偏光显微镜( PLM)、差示扫描量热(DSC)、热重(TG)分析等研究了PEGA相变大单体的结构与性能,通过正交实验获得PEGA的最佳合成工艺.IR显示PEGA中出现酯键及C=C的特征峰;PLM显示PEGA晶体仍有明显的结晶消光截面,但相对纯PEG4000而言,其晶体半径明显减小;DSC分析表明PEGA在46.53℃出现结晶峰,结晶焓为163.21 J/g;TG分析表明PEGA在230℃开始降解,耐热性较好.PEGA交联固化后可制得新型交联网络型固-固相变材料.     

Preparation and phase behavior of acetyl monoglycerides

A homologous series of 1-monoacetyl-3-monoglycerides in which the fatty acyl group varies from C₁₄ to C₂₂ in even C intervals has been prepared by partial acetylation of the appropriate 1-monoglycerides. Crystallization and silica gel chromatography were used to isolate the diglycerides in high purity. The isomeric monoacetyl monostearins were prepared either by application of a similar procedure to 2-monostearin or by acetylation of 1-tetrahydropyranyl-3-monostearin with subsequent removal of the blocking group to obtain 2-acetyl-1-monostearin. In the homologous series of 1-acetyl-3-monoglycerides from monomyristin through behenin the stable form at room temperature, called form I, is a tilted double chain length form, existing up to the melting point for myristin through stearin but transforming to a stable α form before melting for arachidin and behenin. The α form, low melting and entirely metastable for myristin through stearin, transforms reversibly to sub-α on cooling. Both α and sub-α are perpendicular forms and probably of single chain length structure. An interesting feature is the two-step transformation of sub-α to α on warming; the nature of this stepwise transformation, observed for all but myristin, is discussed. A nearly perpendicular double chain length β-like form occurs for palmitin and stearin and perhaps myristin. This form, which has not been well characterized thermally, though possibly entirely metastable, is conceivably a stable form at low temperatures.     

Preparation and phase behavior of acetyl monoglycerides

A homologous series of 1-monoacetyl-3-monoglycerides in which the fatty acyl group varies from C₁₄ to C₂₂ in even C intervals has been prepared by partial acetylation of the appropriate 1-monoglycerides. Crystallization and silica gel chromatography were used to isolate the diglycerides in high purity. The isomeric monoacetyl monostearins were prepared either by application of a similar procedure to 2-monostearin or by acetylation of 1-tetrahydropyranyl-3-monostearin with subsequent removal of the blocking group to obtain 2-acetyl-1-monostearin. In the homologous series of 1-acetyl-3-monoglycerides from monomyristin through behenin the stable form at room temperature, called form I, is a tilted double chain length form, existing up to the melting point for myristin through stearin but transforming to a stable α form before melting for arachidin and behenin. The α form, low melting and entirely metastable for myristin through stearin, transforms reversibly to sub-α on cooling. Both α and sub-α are perpendicular forms and probably of single chain length structure. An interesting feature is the two-step transformation of sub-α to α on warming; the nature of this stepwise transformation, observed for all but myristin, is discussed. A nearly perpendicular double chain length β-like form occurs for palmitin and stearin and perhaps myristin. This form, which has not been well characterized thermally, though possibly entirely metastable, is conceivably a stable form at low temperatures.     

Phase equilibria of the propylene glycol/CO2 and propylene glycol/ethanol/CO2 systems

The high-pressure vapour–liquid phase equilibria (P–T–x–y) of the binary mixture propylene glycol/CO₂ have been experimentally investigated at temperatures of (398.2, 423.2 and 453.2) K over the pressure range from (2.5 to 55.0) MPa using a static-analytic method. Furthermore, the high-pressure vapour–liquid phase equilibria (P–T–x–y) of the ternary mixture propylene glycol/CO₂/ethanol at constant temperatures of (398.2, 423.2 and 453.2) K and at constant pressure of 15.0 MPa have been determined using a static-analytic method. Initial concentrations of components in propylene glycol (PG)/ethanol (EtOH) mixture vary from 10 up to 90 wt.%. In general, for binary system it was observed that the solubility of CO₂ in the heavy propylene glycol reach phase increases with increasing pressure at constant temperature. On the contrary, the composition of gaseous phase is not influenced by the pressure or the temperature. On average the solubility of PG in light phase of CO₂ amounts to 30 wt.%. The system behaviour at temperature of 398.2 K was investigated up to 70.0 MPa and a single-phase region was not observed. Above the pressure 60.0 MPa a single-phase region of the system was observed for the temperature of 423.2 K. For the temperature of 453.2 K the single-phase was observed above the pressure of 48.0 MPa. For ternary system it was observed that the composition of heavy phase is slightly influenced by the temperature when the mass fraction of EtOH in initial mixture is higher than 50 wt.%. If the mass fraction of PG in initial mixture is higher than 50 wt.%, the composition of heavy phase is not influenced by the temperature anymore. The composition of the PG, EtOH and CO₂ in light phase remains more or less unchanged and it is not influenced by the conditions.     

Analysis of mixtures of glycerol,propylene glycol,and trimethylene glycol

Procedures have been presented for the determination of glycerol, propylene glycol, and trimethylene glycol in the solutions containing all three and for analysis of sweet water concentrates. The methods are not limited to the products studied, but may be applied to mixtures of other hydroxy compounds which possess similar properties.     

聚乙二醇/二氧化硅定形相变材料的制备

采用多孔二氧化硅（SiO₂）、聚乙二醇(PEG)等研究一种定形无机 有机复合相变材料的制备方法,并加入适当的促进剂和改性剂对复合材料进行了改性。利用多孔二氧化硅具有良好的吸附性能特点,将聚乙二醇相变材料吸附在二氧化硅微孔结构内,在毛细管力和表面张力的作用下,聚乙二醇在发生固液相变的时候很难从二氧化硅的微孔结构内渗透出来,从而解决了聚乙二醇在蓄热技术中应用时的液体流动问题。同时对相变材料进行了热性能分析,实验证明该复合相变材料具有形状稳定,导热率高,储热能力大等特点。     

Efficient propylene carbonate synthesis from propylene glycol and carbon dioxide via organic bases

Organic bases were first used as effective catalysts for the synthesis of propylene carbonate from propylene glycol and carbon dioxide in the presence of acetonitrile. Acetonitrile in the reaction acted as not only the solvent but also the dehydrating reagent to remove the water produced from the reaction. It was interesting that upon ammonium carbonate being introduced into the reaction system, the catalytic selectivity was significantly enhanced. With 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, the yield of propylene carbonate could reach 15.3% with the selectivity of 100% under the optimal conditions.     

Effective synthesis of propylene carbonate from propylene glycol and carbon dioxide by alkali carbonates

Quantum-chemical calculations give insight in the experimentally observed higher rate of hydrogen–deuterium exchange for oxidized Ga/HZSM-5 over reduced Ga/HZSM-5. The reaction is computed to be more facile over reduced (Ga⁺) than over oxidized (GaO⁺) cations. The difference lies in the difficult formation of active GaH₂⁺ cations from Ga⁺ compared to facile hydrogen dissociation over GaO⁺ to give active GaHOH⁺ cations. Neutral gallium oxide clusters are shown to have a lower intrinsic activity than GaO⁺ cations.     

Phase behavior of homologous series of monoesters of polyols

Phase behavior of anhydrous monopalmitates and stearates and of most laurates, myristates and behenates of ethylene glycol, erythritol, xylitol, sorbitol, and mannitol has been studied. The compounds, substantially free of diesters, are mostly not isomerically pure but are predominantly primary esters. Also studied were the (nonisomeric) palmitate and stearate of pentaerythritol (Pe) and the oleate of erythritol. Mesomorphism, absent in anhydrous monoglycerides unless of short chain length and symmetrical, is a prominent feature of the members of the present group of compounds containing at least three unesterified hydroxyls. In general, crystal melting points rise with length of polyol, and mesomorphic melting points rise faster. Crystal melting points rise with acyl chain length while mesomorphic melting points run through a maximum. Heats of fusion are of the order 40 cal/g for crystal melting and 0.5 cal/g for melting of mesomorphic states. In the range explored, mesomorphic values fall with both polyol length and acyl length. At higher acyl chain length, notably with behenates, there are new features of mesomorphic behavior. Crystalline phase, from solvent, melts to a neat or lamellar phase, which in turn melts to liquid with subsequent appearance of higher melting middle or cylindrical phase. Polymorphism is general among the crystal states and tends to be complex. In a brief study of solvent crystallized 50–50 binary mixes of xylitol stearate with other xylitol esters and other stearates, considerable evidence of solid solution in Form I crystals (of xylitol stearate type) was observed with very modest eutectic lowering of crystal melting point. Mesomorphic points were almost linearly intermediate between those of components. Of particular interest were mixtures of xylitol stearate and 1-monostearin (50–50 and 25–75), for which mesomorphic melting points were realized, and for which an extrapolation to 100% monostearin leads to a hypothetical mesomorphic melting point far below any monoglyceride crystalline melting point. A brief examination of an aqueous xylitol palmitate system explored to a maximum temperature of 165 C shows extensive occurrence of aqueous mesomorphic state somewhat after the manner of monoglyceride systems. Mesomorphic melting level rises rapidly from the value for anhydrous ester.     

The study of dielectric relaxation in propylene glycol-poly(propylene glycol) mixtures

Dielectric complex permittivity of propylene glycol (PG), poly(propylene glycol) (PPG-2000) and their mixtures with concentration of 25, 50 and 75 vol% of PG were measured in the frequency range 10 MHz-4 GHz at 25°C using time domain reflectometry (TDR). For these molecules and their mixtures, only one frequency independent dielectric loss peak was observed. The relaxation for these systems is described by a single relaxation time using Debye model. The large value of observed relaxation time for PG molecules shows the formation of molecular clusters. It is found that the relaxation time for PG-PPG mixtures is smaller in comparison to the relaxation times of PG and PPG molecules, and it linearly increases with the concentration of the PG in the mixtures. The values of relaxation times of PG-PPG mixtures are discussed particularly with respect to the solvent (PG) behaviour, which can be assigned to unaffected, loosely affected and tightly bound solvent and also with respect to the PPG chain coiling. As a peculiar feature the observed relaxation time is direct evidence of the interchange of solvent-solvent to solvent-polymer interaction.     

聚马来酸单脂肪醇酯钠盐的制备及其性能研究

将马来酸酐(MA)先聚合为低聚物聚马来酸酐(PMA),然后再与脂肪醇反应生成一种低聚表面活性剂.聚合反应主要受溶剂种类的影响,而酯化方法对酯化反应影响比较大,在丙酮中以三乙胺催化回流制备聚马来酸单脂肪醇酯(PMAM)的较佳工艺条件为:m(丙酮):m(PMA)=2.0:1,反应时间4 h,催化剂用量1.0%(相对于PMA的质量).PMA经脂肪醇改性、烧碱液中和后生成聚马来酸单脂肪醇酯钠盐(PMAMS).产品用IR和GPC进行表征,测定了产品的表面活性数据cmc、?cmc以及乳化力等.     

Ethoxylated glycerol and propylene glycol glycoside palmitates from lactose

Polyoxyethylene polyol glycoside palmitates were prepared by the following successive reactions: transglycosylation of lactose by glycerol and propylene glycol to yield crude mixtures of the polyol glucosides and galactosides; alkoxylation with ethylene oxide; and tranesterfication by methyl palmitate. Almost all the solid waxy products exhibited low surface and interfacial tensions and good emulsion stability; they are expected to be effective food emulsifiers, cosmetic surfactants and biodegradable industrial surfactants. ARS, USDA.     

聚乙二醇/石墨烯纳米片复合相变材料的制备及其性能研究

以聚乙二醇(PEG)作为相变工作物质,以具有优异导热性能的石墨烯纳米片(GNPs)作为导热填料,通过熔融共混法制备出一系列不同GNPs含量的PEG/GNPs复合相变材料。采用激光导热仪、差示扫描量热仪、扫描电子显微镜、X射线衍射仪、红外光谱仪等测试PEG/GNPs复合相变材料的导热性能、热物性、微观形貌、结晶性能及化学组成。结果表明,GNPs均匀分散于PEG基体中,形成能够加快热量传递的导热通路,复合材料体系的导热系数得以显著提高,而相变焓仅仅略微下降,当GNPs含量为2%时,复合材料体系的导热系数是PEG的249.7%,而相变焓损失率却仅为3.9%;PEG与GNPs二者间仅是物理吸附,并未发生化学反应,复合材料体系的结晶性能良好;PEG与GNPs复合相变材料的热响应速度更快,能源利用率因而更高。     

Aqueous-phase adsorption of glycerol and propylene glycol onto activated carbon

Adsorption of reactant and product species can have a major effect on local pore concentrations in activated carbon-supported metal catalysts. Individual and combined adsorption of glycerol (GO) and propylene glycol (PG) onto activated carbon in aqueous solution is reported here at concentration ranges of 0.05-2.0 M and temperatures from 25 °C to 160 °C. Langmuir and Freundlich isotherms are used to model the single component data, with the Langmuir model best describing results below 0.75 M. The extended Langmuir model has been used to model the competitive adsorption system - model parameters determined from single component experiments accurately predict two component adsorption data over the temperature and concentration ranges studied. Propylene glycol adsorbs more strongly than GO onto the activated carbon supports studied, and also adsorbs to a somewhat greater extent compared to GO. This is attributed to the greater organic character of PG, which favors its selective adsorption onto the support material.