【作者】 高静；

【导师】 赵学明；

【作者基本信息】 天津大学 ， 生物化工， 2005， 博士

【摘要】 对以乳酸菌为菌体,以氨水为中和剂,对L-乳酸的发酵工艺进行了探讨,确定出适宜的发酵pH是6.5;在发酵液pH为6.5,以25 ml/h的速度流加浓度为600 g/L葡萄糖,发酵80 h后,乳酸铵的产量为136.8 g/L,葡萄糖流加发酵与非流加发酵相比,达到相同的乳酸铵浓度缩短了约30小时。并建立了细胞生长、产物生成和底物消耗的动力学模型,实验结果和模拟结果吻合良好。将磁性材料Fe₃O₄和SO₄^2-/ZrO₂固体超强酸进行组装。得到了磁基体的适宜制备条件是:n(Fe²⁺) /n(Fe³⁺) =1:6,以0.1mol/L NaOH溶液为沉淀剂,基液的pH为12,Fe²⁺与Fe³⁺混合液滴加速度为2ml/s,滴加方式为将混合液缓慢加入到NaOH基液中,晶化时间为30min;磁性超细固体超强酸的适宜制备条件是:nFe₃O₄:nZrO₂=1:10,焙烧温度为5000C。在反应时间为5h,催化剂用量为乳酸质量的6%,酸醇摩尔比为1:5时最高产率为84%,催化剂回收率为90%以上。采用激光粒度仪、磁强计、XRD、比表面积测定仪等分析测试手段对催化剂的结构和性能进行了表征和评价。结果表明:磁基体的平均粒径小于100nm,且分布范围较窄,磁基体的饱和磁强度（σS）基本上在80 emu·g^-1以上,磁基体XRD谱图与Fe₃O₄标准谱图基本相同。在5000C焙烧时所得催化剂的比表面积为78.9m²/g。表征结果表明制得的催化剂属于超强酸。对以SO₄^2--Fe₃O₄/ZrO₂为催化剂,乳酸和乙醇的酯化反应动力学进行了研究,研究表明只要搅拌转速≥85 r/min,反应就不受外扩散的影响,并且在所制备的催化剂粒度范围内,反应和内扩散无关。并且得到了反应的动力学模型。同时发现在温度较低时,在反应开始阶段存在诱导期现象,并对诱导期现象产生的原因进行了讨论。在自行设计的催化精馏塔内对乳酸和乙醇酯化反应的催化精馏过程进行了研究,建立了催化精馏实验装置,确定了实验流程,得到了适宜工艺条件为:醇酸比为4:1,回流比为1:1,乳酸进料量为0.6482mol/h,乳酸乙酯一次循环收率达到51.64%。并利用“化学理论”并且结合海登-奥康纳尔公式计算逸度系数,用NRTL方程计算活度系数,借助ASPEN PLUS软件,用平衡级模型进行了催化精馏塔的模拟,模拟结果与实验结果吻合较好。更多还原

【Abstract】 A process for efficient production of ammonium lactate by lactic acid bacteriumin pH-controlled batch fermentation was developed. Effects of pH on the biomass andammonium lactate in batch culture were studied. The final concentration of 136.8gammonium lactate per liter was obtained at the preferable condition of pH 6.5 and 25ml/h glucose fed-batch speed after 80h. The time reached the same concentration ofammonium lactate was approximately decreased 30h. Kinetic models of cell growth,ammonium lactate formation and glucose consumption in batch fermentation wereproposed and kinetic model parameters were determined. The calculated valuesagreed approximately with the experimental data.The magnetic particles of Fe₃O₄ and the solid super-acid catalyst SO₄^2--ZrO₂were assemble to become a novel ultra-fine catalyst SO₄^2--Fe₃O₄/ZrO₂ withmagnetism and strong super-acidity. The magnetic particles of Fe3O4 weresynthesized under the optimum conditions of n(Fe²⁺) /n(Fe³⁺) was 1:6, the mixturesolution of Fe²⁺ and Fe³⁺ dropped to 0.1mol/L NaOH solution and dropped speed was2ml/s. The results showed that the appropriate conditions made SO₄^2--Fe₃O₄/ZrO₂ were as follows: nFe3O4:nZrO2 was 1:10, baking temperature was 5000C. Theyield achieved 84 % with reaction time was 5 hours, weight of catalyst was 6.0% oflactic acid mass, the molar ratio of lactic acid to ethanol was 1:5. The catalyst couldbe isolated from other materials by magnetic separation and the reuse rate exceeded90%. The catalyst was characterized by techniques such as XRD, BET et al .The resultsshowed that average particle size of magnetic particles was smaller than 100nm,andmagnetism（σ_s） overtaken 80emu.g^-1 that was higher than the value had reported. XRDcurves of Fe₃O₄ prepared and standard Fe₃O₄ were essential the same. The specificsurface area of catalyst decreased with the increase of baking temperature, and thatwas 78.9m²/g when baking temperature was 5000C. The kinetics of the reaction of ethanol and lactic acid in the presence of SO42--Fe₃O₄/ZrO₂ were experimentally determined and the model for reactive kinetics wasobtained: At the same time, the problem of inducement period was also found whenthe temperature was lower.An extensive investigation of ethyl lactate synthesis by reactive distillation waspresented for the first time. The one-time yield of ethyl lactate achieved 51.64% infollow appropriate condition: the reflux ratio was 1:1, the molar ratio of ethanol tolactic acid was 4:1, lactic acid feeding flux was 0.6482 mol/h respectively. Based onthe experiment and the model for reactive kinetics, ASPEN PLUS software waschosen to simulate the temperature and concentration using equilibrium-staged model,good agreement between experimental data and the simulation results been achieved.The results indicated that the process was little pollution on the environment and littleerosion on the equipment, and ethyl lactate was a “green” solvent, so that technologywas a “green” technique and will have good prospective in the future.更多还原