精馏法合成乳酸乙酯的研究

采用带分水器的精馏装置,使乳酸酯化的原有脱水－酯化两步过程,能在该装置上一步进行。通过正交试验, 考察了乙醇的用量、催化剂的用量、带水剂的用量三个因素对乳酸乙酯收率的影响。确定了最佳的配比,并由验证实验得到证明,脱水－酯化反应在2h基本完成,乳酸乙酯的收率可达到96％以上。     

催化合成乳酸乙酯

以对甲苯磺酸为催化剂,乙醇与乳酸的物质的量比为3:1,每物质的量乳酸消耗对甲苯磺酸2.0g,采用用量为理论量0.7倍的苯作为带水剂,在70℃的温度下回流分水4 h,反应生成乳酸的转化率可达93%,若采用温度为70～75℃,且压力为2.53kPa时收集60～62℃的馏分,即得标题物,收率达72%。     

固体酸催化合成乳酸乙酯

用乳酸和乙醇为原料，在ＨＹ型固体酸存在下制备了乳酸乙酯。催化剂用量为１１－３０ｇ，在１００－１６０℃下，乳酸与乙醇反应８－１０ｈ，酯化率可达６０％以上，催化剂可重复使用。     

脱水法合成乳酸乙酯

以乳酸和乙醇为原料 ,在对甲苯磺酸的催化下以氧化钙或 3A分子筛或MgSO3 为脱水剂 ,采用自制的索氏提取器进行回流脱水合成乳酸乙酯。对影响乳酸乙酯产率的诸因素进行了考察。实验结果表明 :加入脱水剂和带水剂可以显著提高乳酸乙酯的产率 ,酯的产率随催化剂用量的增加、醇酸物质的量比的增大、反应时间的延长先增加到最高点后略有降低。当乳酸 0 1mol、乙醇 0 3mol、对甲苯磺酸 1 0g、带水剂环己烷 5 0mL、脱水剂CaO 18 7g和反应 2h时 ,乳酸乙酯的产率达 84 5 %。     

精馏法合成乳酸乙酯的研究

采用带分水器的精馏装置 ,使乳酸酯化的原有脱水 -酯化两步过程 ,能在该装置上一步进行。通过正交试验 ,考察了乙醇的用量、催化剂的用量、带水剂的用量三个因素对乳酸乙酯收率的影响。确定了最佳的配比 ,并由验证实验得到证明 ,脱水 -酯化反应在 2h基本完成 ,乳酸乙酯的收率可达到 96 %以上     

固体酸催化合成乳酸乙酯

用乳酸和乙醇为原料,在HY型固体酸存在下制备了乳酸乙酯.催化剂用量为11～30g(以每100g乳酸计),在100～160℃下,乳酸与乙醇反应8～10h,酯化率可达60%以上,催化剂可重复使用.     

乳腈法合成乳酸乙酯

介绍了乳腈法合成乳酸乙酯的实验方法、最佳工艺条件及应用前景.     

硫酸氢钠催化合成乳酸乙酯的研究

采用硫酸氢钠为催化剂合成乳酸乙酯。研究表明该催化剂具备价廉易得，催化活性高，能有效提高原料利用率，流程简单，操作方便，减少废液排放等优势。产品总收率达88．3％。     

稀土化合物催化合成乳酸乙酯的研究

研究了稀土硫酸盐化合物对合成乳酸乙酯的催化作用，探讨了催化剂用量，酸醇摩尔比和反应时间对酯化反应的影响，适宜条件下，酯化产率可达７４％～７９％。     

离子液体催化合成食用香料乳酸乙酯的研究

以离子液体[HSO3-pmim]HSO4为催化剂,乳酸和乙醇为原料合成乳酸乙酯。通过正交实验考察了影响酯化反应的主要因素,确定最佳合成条件为:[HSO3-pmim]HSO4用量10mL,酸醇摩尔比1.0∶1.5,反应温度110℃,反应时间2.0h,酯化率达96.7%。离子液体易分离回收,可重复使用。     

有机相酶法不对称水解乳酸乙酯

探讨了在有机介质中酶催化外消旋乳酸乙酯不对称水解制备L-乳酸的可行性。 研究了反应介质、不同来源的酶、摇床转速、水含量、乳酸乙酯浓度及温度等因素对反应的影响。结果表明,N435的活性和选择性较高,叔丁醇和异辛烷的混合溶剂（体积比为1∶1）为最合适的反应介质,其余最适条件为：摇床转数200 r•min^-1、水含量（水与底物的质量比）1∶5、乳酸乙酯浓度0.27 g•ml^-1、酶浓0.8 g•mol^-1、反应温度60℃,在此条件下反应16 h得产物ee值为90.02% ,产率为28.69%。 最后研究了乳酸乙酯不对称水解的动力学,结果表明反应符合米氏方程,属于双底物抑制的双乒乓机制,并考察了D-乳酸乙酯和D-乳酸在建立反应动力学模型时的影响。     

催化精馏制备乳酸乙酯

引言 乳酸乙酯具有无毒、溶解性好、不易挥发、可生物降解等特点,是一种极具开发价值和应用前景的"绿色溶剂"[1].     

NO2氧化合成丙酮酸乙酯

研究了以NO2为氧化剂,催化氧化乳酸乙酯合成丙酮酸乙酯的新方法,讨论了氧化剂用量、反应时间、反应温度、催化剂用量等因素对反应的影响。在最佳实验条件下,产品收率大于75%,纯度达98%。本法最大的优点是为NO2废气的回收利用提供了新的途径。     

Effect of solvent and impurity on synthesis of ethyl lactate from fermentation-derived ammonium lactate

Fermentation-derived ammonium lactate was converted into ethyl lactate by decomposition in various organic solvents followed by esterification with ethanol over Amberlyst catalyst. The ammonium lactate was decomposed more efficiently in an organic solvent with high boiling point, where the produced lactic acid was stabilized well as a monomer without oligomerization. However, only the nonreactive phosphate-type solvent such as triethyl phosphate and tributyl phosphate showed a notable ethyl lactate yield in the subsequent esterification reaction compared with dimethyl sulfoxide and N-methyl pyrolidine. The lactic acid yield in ammonium lactate decomposition and the subsequent ethyl lactate yield were also highly dependent on solvent ratio to ammonium lactate, temperature and pressure in ammonium lactate decomposition reaction. The amino acid impurity contained in the fermented ammonium lactate as well as the unreacted ammonium lactate reduced the acid strength of Amberlyst-36, which resulted in the final ethyl lactate yield.     

Low‐temperature clean preparation of poly(lactic acid) foams by combining ethyl lactate and supercritical CO2: correlation between processing and foam pore structure

This study reports the low‐temperature and clean fabrication of porous poly(lactic acid) (PLA) through solid‐state foaming using various mixtures of ethyl lactate (EL) and supercritical CO₂ (scCO₂) as the blowing agent. Results showed that adding a small amount of EL (up to 0.2% molar fraction) to scCO₂ enhanced the plasticizing effect of the blowing agent mixture. As a direct consequence, at an operating temperature of 35 °C, PLA foams could be manufactured with homogeneous morphology, density as low as 0.09 ± 0.01 g cm^?3, mean pore sizes up to 519.0 ± 205.0 µm and pore densities in the range 2.0 × 10⁵ to 3.4 × 10⁸ pores cm^?3. Conversely, at a temperature of 40 °C, an increase of plasticizer concentration in the blowing agent mixture up to 0.2% promoted the crystallization of the polymer during sorption stage and, consequently, foaming was slightly reduced. © 2013 Society of Chemical Industry     

乳酸脱氢酶的分离纯化及其催化合成苯乳酸的研究进展

对乳酸脱氢酶的来源、分离纯化及其催化合成苯乳酸的研究进行了综述。首先,分析了乳酸脱氢酶的微生物来源,重点对乳酸菌中乳酸脱氢酶的分离方法及相关研究现状进行了总结,认为采用晶胶层析方法可直接一步从破胞液中分离高纯度的乳酸脱氢酶;然后,分析了乳酸脱氢酶催化苯丙酮酸的核心反应机理、最适条件及其工程改造,讨论了pH、温度、耐热性等参数对乳酸脱氢酶催化苯丙酮酸的影响,表明不同菌种乳酸脱氢酶催化苯丙酮酸最适pH和温度有很大差异;最后,对比了乳酸脱氢酶酶法合成苯乳酸相关工程改造的研究工作,指出基因修饰能有效提高乳酸脱氢酶酶法对苯丙酮酸的催化能力,同时乳酸脱氢酶与辅酶共表达体系的构建是下一步研究的重点方向。     

Enzymatic esterification of lactic acid,utilizing the basicity of particular polar organic solvents to suppress the acidity of lactic acid

BACKGROUND: Lipase‐catalyzed esterification of lactic acid with ethanol was investigated; however, some difficulties exist with such a system. Because of its high polarity, lactic acid is immiscible with non‐polar organic solvents, which have generally been used for non‐aqueous enzyme reactions. In addition, the strong acidity of lactic acid causes acid inactivation of enzymes and acid‐catalyzed, non‐enzymatic esterification. RESULT: In the present study, particular polar organic solvents, such as 1,4‐dioxane, were found to suppress the enzyme inactivation and non‐enzymatic esterification caused by the acidity. The magnitude of this effect varied with solvents and strongly correlated with the Kamlet‐Taft parameter β, which indicates the basicity of the solvents in non‐aqueous systems. An immobilized lipase from Candida antarctica was found to be the most active and stable enzyme for the reaction. Based on the findings, lipase‐catalyzed esterification of lactic acid (1.0 mol L^?1) could be continued for up to 4 weeks without any loss of enzyme activity. CONCLUSION: In addition to miscibility with lactic acid, the effect of these polar solvents, which is to suppress the acidity of lactic acid and is presumably due to the basicity, appears to play a very important role in the efficient enzymatic reaction of lactic acid. Copyright © 2008 Society of Chemical Industry     

UiO-66(Zr)系列MOFs 催化材料的制备及在乳酸乙酯合成中的应用

以无水四氯化锆ZrCl₄和不同的有机配体,如苯二甲酸、2-硝基苯二甲酸和1,2,4-苯三甲酸为原料,DMF为溶剂,通过溶剂热法合成了一系列UiO-66(Zr)的金属有机骨架MOFs,并用于催化转化二羟基丙酮至乳酸乙酯的反应。UiO-66(Zr)的催化活性和乳酸乙酯的选择性可以通过在制备过程中采用含有不同吸电子基团的无机配体来调节。而且当使用反应中间产物丙酮醛作为起始反应物时,MOFs的活性有了显著的提高。材料表征结果显示,UiO-66(Zr)系列MOFs材料中Brønsted酸的含量低但强度较大,而Lewis酸的含量则较高。本文对二羟基丙酮转化为乳酸乙酯的反应机理进行了详细分析,并实现了100%的二羟基丙酮转化率和乳酸乙酯选择率。