有氧补偿乳状液中多不饱和脂肪酸氧化模型

研究了恒表面氧压搅拌式有氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)的氧化。通过综合考虑气液边界传质阻力、油水边界乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应动力学,建立了相应的扩散-氧化数学模型。实验验证该模型能较好地拟合搅拌式有氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并在乳化剂浓度变化对乳状液中PUFA氧化的影响方面表现出很好的适用性。研究对揭示乳状液中PUFA的氧化机制最终有效控制PUFA的氧化具有重要的理论研究价值。     

无外界氧补偿条件下乳状液中多不饱和脂肪酸氧化模型

建立了在无外界氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)氧化的数学模型。该模型综合考虑了乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应以及油水相比表面积等因素的影响。实验验证了该模型能较好地拟合无外界氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并模拟计算了乳化剂膜传质系数和油水相比表面积等因素对扩散-氧化的影响程度。结果表明,乳化剂膜传质系数和油水相比表面积是影响乳状液中PUFA的氧化的主要因素。     

填充床电化学反应器普遍化模型方程数值求解方法

以有限差分法与正交配置法联用对填充床电化学反应器的模型方程进行了求解，结果表明该法是一种快速、有效地求解具有较为复杂的边界条件的偏微分方程的计算方法。     

甲缩醛氧化制甲醛固定床反应器的数学模拟

依据甲缩醛氧化制甲醛的宏观动力学模型和固定床拟均相二维模型，采用正交配置法模拟固定床单管反应器，模拟结果与试验数据基本一致，表明该反应器数学模型具有一定的可靠性和实用性。用此模型进一步考察了主要操作条件，催化剂稀释比和床展稀释长度对甲醛收率和热点温度的影响，为该过程的工业放大和反应器设计提供了依据。     

气液液三相体系的二维非均相传质模型与求解

在柱坐标系中建立了描述分散第二液相增强气液传质的轴对称二维非均相传质模型,采用有限差分法计算了传质组分在液膜区内的轴向和径向浓度分布以及传质增强因子,计算方法快捷、有效,并且能很好地吻合现有文献中的实验数据.     

搅拌反应器中氧气 - 正癸烷 - 水溶液体系的气液传质实验

用亚硫酸钠氧化法测定了机械搅拌高压釜中氧气-亚硫酸钠溶液体系、氧气-正癸烷-亚硫酸钠溶液体系和氧气-正癸烷-亚硫酸钠溶液+表面活性剂体系的气液体积传质系数(k La).研究了搅拌转速、搅拌桨高度、有机相与水相体积比和表面活性剂浓度对k La的影响,得到了经验关联式.k La随有机相体积分率和表面活性剂浓度的增大而降低,随搅拌转速、搅拌桨高度与液相高度比的增大而增大.     

基于POD降阶模型的正弦波翅片扁管管翅式换热器流动与传热特性分析

为了提高正弦波翅片扁管管翅式换热器的数值设计效率,以FVM (finite volume method,有限体积法)的计算结果作为样本数据构建POD降阶模型,研究换热器空气侧的流动与传热特性。结果表明：单参数和双参数变化时POD降阶模型重构的温度场与FVM计算结果的偏差集中表现在正弦波翅片表面区域,且沿主流方向呈减小趋势,2种方法所得速度分布的差异主要集中在主流区域。随着变量参数个数的增多,POD降阶模型的计算精度及计算效率均有所降低。POD降阶模型重构的物理场与FVM结果间的平均相对偏差最大值为2.921%,平均计算速度比传统FVM计算速度最大提高了11752倍。     

搅拌式有限氧补偿条件下乳状液中多不饱和脂肪酸氧化模型

The oxidation of polyunsaturated fatty acids （PUFA） in emulsion with stirring and limited oxygen compensation was studied. A mathematical model of diffusion-oxidation was developed considering the mass transfer resistance of a gas-liquid boundary, the resistance of the boundary layer from the emulsifier membrane, and the autocatalytic-type autoxidation reaction of PUFA. The dynamic mass transfer coefficient of the emulsifier membrane, k0, was introduced. The model was verified by comparing the predictions of the model with the experi- mental data. The results indicated that the model was in good agreement with the oxygen diffusion and linoleic acid oxidation in the emulsion, and showed good applicability in the prediction of the effect of the emulsifier type on the oxidation of PUFA in the emulsion. It indicated that the oxidation of PUFA in emulsions, with stirring and limited oxygen compensation from the atmosphere, was controlled mostly by mass transfer resistance from the emulsifier membrane.     

Oxidation of linoleic acid in emulsions: Effect of substrate, emulsifier, and sugar concentration

Linoleic acid oxidation in oil-in-water emulsions stabilized by a nonionic surfactant (Tween-20) was studied. The emulsion composition was varied at a constant oil droplet size. Lipid oxidation was measured as a function of time in the presence of a catalyst (FeSO₄ corbic acid) by two methods: gas chromatographic determination of residual substrate and ultraviolet-visible spectrophotometric determination of conjugated dienes. Rate of oxidation was influenced by the emulsion composition (relative concentrations of substrate and emulsifier) and especially by the partition of the emulsifier between the interface and water phase. Concentrations of emulsifier exceeding the critical micelle concentration protected the fatty acid against oxidation. Excess surfactant formed micelles and mixed micelles with linoleic acid, which retarded oxidation by diluting the substrate or perhaps by replacing linoleic acid at the interface, making it less accessible to radical attack. The addition of sucrose also had a protective effect, but only up to a certain concentration, indicating the effect may involve factors other than viscosity.     

Liquid-phase oxidation of anthracene in acetic acid with an oxygen/Nitric acid system

Oxidation of anthracene in acetic acid by the oxygen/nitric acid system has been studied and an attempt has been made to ascertain a practical limit of the amount of solvent keeping the commercial prospects in view. The effects of other reaction parameters such as flow rate, amount of nitric acid and water, residence time, etc., have been investigated. While opting for a solvent/substrate ratio of 10, the optimum conversion of anthracene to anthraquinone free from nitro-compounds has been found to be 91% with purity of 98.7%, acceptable to dye-stuff industries.     

Behavior of phenolic antioxidants in a partitioned medium: Focus on linoleic acid peroxidation induced by iron/ascorbic acid system

The peroxidation of linoleic acid was induced by the Fe²⁺/ascorbic acid system in a micellar medium, and the kinetics of the produced conjugated dienes to a weak level (0.7 μM) in order to initiate only the sequential oxidative reactions without superimposed antioxidant activity. Other conditions were established to obtain a simple kinetic profile. With a linoleic acid/Fe²⁺ ratio of 10 and an Fe²/ascorbic acid ratio of 23 in the medium emulsified by Tween and saturated in oxygen, no limiting effect of substrates was observed for several hours. Fe²⁺ disappeared in less than 5 min, while a linear propagation rate was reached after 1 h for up to 15 h. Two parameters were chosen to quantify the level of the oxidation: the slope of the linear phase, and the extrapolated absorbance of this step at zero time. These two parameters were used in order to compare the antioxidant power of different phenolic compounds in this partitioned medium.     

平流多效蒸发系统的数学模型与求解

为了充分利用能量,采用冷凝水闪蒸、引出额外蒸汽及引出各效完成液预热原料液等节能措施,考虑蒸发过程有固相析出的情况,建立了由多效蒸发和多级预热两个子系统构成的平流多效蒸发系统数学模型。将物料衡算和热量衡算方程组写成矩阵方程的形式,保留或舍弃矩阵方程中的相关块矩阵,模型就能代表有或无固相析出、有或无冷凝水闪蒸、有或无引出各效完成液预热原料液以及不同情况任意组合的平流多效蒸发过程,该模型还可以用于计算不同效数的平流多效蒸发过程,实现模型的通用。利用智能拟合法,将系统的固液相平衡数据拟合成相平衡方程,实现模型的计算机编程求解。用迭代法结合矩阵法求解模型,研究结果表明,平流多效蒸发系统常规设计的数学模型具有通用性,采用冷凝水闪蒸、引出额外蒸汽预热原料液、引出各效完成液预热原料液是有效的节能技术,对四效平流蒸发含NaCl的NaOH溶液系统,采用以上节能措施可节省加热生蒸汽30%左右,节能效果显著。求解模型的算法稳定且高效。     

Influence of ascorbic acid and ascorbyl palmitate on the aroma composition of an oxidized vegetable oil and its emulsion

The formation of conjugated diene hydroperoxides and hexanal was compared to the development of aroma profiles during initial lipid oxidation of a vegetable oil and its 40% oil-in-water emulsion at 60°C. The aroma profiles of the oil and the emulsion with and without addition of ascorbic acid or ascorbyl palmitate were compared. The aroma compounds were isolated under a model mouth system and analyzed by gas chromatography/sniffing port analysis. Detectable odors were found and corresponded to 11 and 14 volatile compounds in the oil and the emulsion, respectively. The emulsion had higher lipid oxidation rates than the oil. Addition of ascorbic acid and ascorbyl palmitate had little influence on the aroma composition of the oil. In the emulsion, addition of these compounds resulted in diminished generation of odor active compounds. Results of measurements of conjugated diene hydroperoxides and headspace hexanal corresponded to that of the lipid oxidation rate in general, but predicted insufficiently the alterations in the aroma compositions by antioxidants.     

Synthesis of adipic acid through oxidation of K/A oil and its kinetic study in a microreactor system

Synthesis of adipic acid (AA) through the oxidation of cyclohexanol and cyclohexanone (K/A oil) with nitric acid was conducted in a capillary microreactor system. Effects of the temperature, the nitric acid concentration, the volumetric flow rate ratio of nitric acid to K/A oil, and the capillary length on the selectivity and the product yield were investigated systematically to achieve optimal reaction conditions. Notably, a high yield of AA (i.e., 90%) was achieved just in 6 seconds at 85°C with the use of 55 wt% nitric acid. Gas components produced in this oxidation process and its total volumetric flow rate were determined under various operational conditions, which was beneficial for reaction mechanism characterization and process optimization. Finally, a kinetic model was established, which was of crucial theoretical significance and practical value for optimizing the reactor design and better understanding such fast and highly exothermic multiphase processes with abundant gas production.