共查询到20条相似文献,搜索用时 125 毫秒
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以新型酸性离子液体1-丁基喹啉硫酸氢盐([BQu]HSO4)为催化剂催化月桂酸与甲醇酯化反应制备生物柴油工艺研究,详细考察了离子液体用量、醇酸摩尔比、反应时间及反应温度等因素对月桂酸甲酯产率的影响。在单因素实验基础上利用响应面分析法优化月桂酸甲酯的最佳制备工艺条件为:离子液体用量为月桂酸质量的1.3%,甲醇与月桂酸摩尔比为2.8:1,反应时间3.2 h,反应温度373 K,此条件下生物柴油产率为96.3%,该结果与模型预测值基本相符。最佳条件下,制备月桂酸甲酯反应的活化能为25.25 kJ/mol,动力学方程为: 。 相似文献
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废工业棕榈油制备生物柴油的研究 总被引:3,自引:0,他引:3
利用固体酸作催化剂对酸值较高的废棕榈油进行预酯化,采用正交试验优化预酯化的工艺条件,最佳工艺条件是:反应温度为70 ℃,反应时间为4.0 h,固体酸催化剂的用量为3.0%,预处理后废棕榈油的酸值为2.18 mg KOH/g.研究了预酯化后的废棕榈油与甲醇进行的酯交换反应,得到最优工艺条件是:反应温度为65 ℃,反应时间为1.0 h,催化剂KOH的用量为1.0%,酯交换反应的转化率为96.85%,生物柴油总得率为93.2%.以废棕榈油为原料制备的生物柴油,除倾点较高外,其主要性能均符合柴油标准. 相似文献
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以菜籽油在亚临界水解反应中制取的脂肪酸为原料,研究菜籽油脂肪酸在超临界甲醇中的酯化反应工艺条件及动力学模型。通过单因素试验考察了反应温度、醇酸体积比、反应压力、反应时间对酯化转化率的影响,并采用超高效液相色谱法分析油酸甲酯含量的变化情况。试验结果表明菜籽油脂肪酸在超临界甲醇中酯化反应的最佳工艺条件为:反应温度270℃,反应时间40 min,反应压力25 MPa,醇酸体积比2∶1。在最佳工艺条件下菜籽油脂肪酸酯化转化率超过了98%,动力学模型为-dCA/dt=62.98e-20.14/RTC1.8A。 相似文献
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目的:进行壳聚糖对蔗糖溶液中单宁酸的性能研究。方法:通过吸附动力学和吸附等温线的考察,将吸附动力学实验数据采用粒内扩散模型、准一级动力学模型和准二级动力学模型线性拟合,吸附等温线数据采用Langmuir模型和Freundlich模型线性拟合。结果:在单宁酸的初始浓度为100 mg/L和250 mg/L时,壳聚糖对蔗糖溶液中单宁酸的吸附动力学用准二级动力学模型的拟合效果最好(R2=0.9993和0.9957);壳聚糖对蔗糖溶液中单宁酸的吸附等温线用Langmuir模型拟合效果最好(R2=0.9977)。结论:该吸附属于单分子层的化学吸附,理论饱和吸附量为107.53 mg/g。 相似文献
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烤肠中芽孢杆菌生长动力学模型及货架期预测 总被引:1,自引:0,他引:1
以真空包装烤肠中芽孢杆菌为研究对象,建立其生长动力学模型及货架期预测模型。将同批次真空包装烤肠存放于4,10,25℃条件下,定期进行各指标测定,由此建立其中芽孢杆菌生长的一级和二级模型以及货架期预测模型。结果表明,修正的Gompertz模型可以很好的描述烤肠中的芽孢杆菌的生长情况,建立不同温度下3个一级生长动力学模型,其R2均在0.960以上,其偏差因子Bf与准确因子Af值均在可接受范围内;平方根(Belehradck)模型可以很好的描述温度与延滞时间(λ)、最大比生长速率(μmax)间的关系,建立了温度与延滞时间、最大比生长速率间的二级模型,其R2均在0.940以上,其残差的绝对值均小于0.1;通过一级和二级模型建立出了真空包装烤肠在4~25℃条件下贮存的货架期预测模型。 相似文献
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运用定温法和加速试验相结合的方法,对绿茶中维生素C氧化进行动力学分析研究,探讨通过维生素C的保留量预测绿茶保质期方法的可行性。研究中比较了动力学中常用的4种反应机理函数模式,通过试验与理论分析,得出线性最佳的三维扩散函数作为绿茶中维生素C的反应机理函数,获得了其前因子、活化能等动力学参数以及反应速率常数与温度的关系。研究结果为深入研究茶叶包装及其保质期预测提供了技术基础。 相似文献
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Several groups of popular antibacterial agents (i.e., phenols, fluoroquinolones, aromatic N-oxides, and tetracyclines) were demonstrated in earlier studies to be highly susceptible to oxidation by manganese oxides, a common oxidant in soils. However, because of the high complexity, the reaction kinetics were not fully characterized. A mechanism-based kinetic model has now been developed to successfully describe the entire range of kinetic data for a total of 21 compounds of varying structural characteristics (with R2 > 0.93). The model characterizes the reaction kinetics by two independent parameters, the reaction rate constant (k) and total reactive surface sites (S(rxn)). The model fitting indicates that the reaction kinetics of antibacterials with MnO2 are controlled by either the rate of surface precursor complex formation (for tetracyclines) or by the rate of electron transfer within the precursor complex (for phenols, fluoroquinolones, and aromatic N-oxides). The effect of reactant concentration, pH, and cosolutes on the reaction kinetics was evaluated and correlated to kand S(rxn). All the trends are consistent with the proposed rate-limiting steps. This new model improves the ability to quantitatively evaluate the kinetics of oxidative transformation of organic contaminants by manganese oxides in well-defined systems. 相似文献
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Development of a simple model based on chemical kinetics parameters for predicting respiration rate of carambola fruit 总被引:1,自引:0,他引:1
Hua-Wei Duan Zhi-Wei Wang & Chang-Ying Hu 《International Journal of Food Science & Technology》2009,44(11):2153-2160
The respiration model was parameterised with experimental data obtained at temperatures 10, 15, 20, 25 and 30 °C by the closed system. Reaction orders of O2 and CO2 determined for respiration rate are 0.912 and −0.24, respectively. Estimates of A and E a for rate coefficient are 5.219 × 1010 h−1 and 61.397 kJ mol−1 , respectively. The reliability of the model was verified against new data generated from 18 °C. An enzyme kinetics based model was likewise built and verified as a contrast. Verification results indicate that the chemical kinetics model performs very well and has superiority over the enzyme kinetics one. This study demonstrates that chemical kinetics can be used to underpin the development of simple respiration model and should facilitate the prediction of respiration rate for the carambola fruit in practice. 相似文献
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The enhanced quasi-chemical kinetics (EQCK) model is presented as a methodology to evaluate the nonlinear inactivation kinetics of baro-resistant Listeria monocytogenes in a surrogate protein food system by high-pressure processing (HPP) for various combinations of pressure (P= 207 to 414 MPa) and temperature (T= 20 to 50 °C). The EQCK model is based on ordinary differential equations derived from 6 "quasi-chemical reaction" steps. The EQCK model continuously fits the conventional stages of the microbial lifecycle: lag, growth, stationary phase, and death; and tailing. Depending on the conditions, the inactivation kinetics of L. monocytogenes by HPP show a lag, inactivation, and tailing. Accordingly, we developed a customized, 4-step subset version of the EQCK model sufficient to evaluate the HPP inactivation kinetics of L. monocytogenes and obtain values for the model parameters of lag (λ), inactivation rate (μ), rate constants (k), and "processing time" (tp). This latter parameter was developed uniquely to evaluate kinetics data showing tailing. Secondary models are developed by interrelating the fitting parameters with experimental parameters, and Monte Carlo simulations are used to evaluate parameter reproducibility. This 4-step model is also compared with the empirical Weibull and Polylog models. The success of the EQCK model (as its 4-step subset) for the HPP inactivation kinetics of baro-resistant L. monocytogenes showing tailing establishes several advantages of the EQCK modeling approach for investigating nonlinear microbial inactivation kinetics, and it has implications for determining mechanisms of bacterial spore inactivation by HPP. Practical Application: Results of this study will be useful to the many segments of the food processing industry (ready-to-eat meats, fresh produce, seafood, dairy) concerned with ensuring the safety of consumers from the health hazards of Listeria monocytogenes, particularly through the use of emerging food preservation technologies such as high-pressure processing. 相似文献
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M.A. Del Nobile G.G. Buonocore A. Panizza G. Gambacorta 《Journal of food science》2003,68(4):1316-1323
ABSTRACT: A mathematical model to predict the hydration kinetics of spaghetti during cooking and overcooking is presented. The phenomena involved during the hydration process, such as starch crystalline domains melting kinetics, water diffusion, macromolecular matrix relaxation kinetics, and "residual deformation" release kinetics, were separately described. To validate the developed model, water sorption tests on commercially available spaghetti strands were run at 100 °C. In particular, the weight, diameter, and length of spaghetti strands were monitored over a period of 200 min. The fitting and predictive ability of the model was successfully tested, corroborating the validity of the approach used to derive the model. 相似文献
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A computer model was developed for the estimation of the kinetics of microbial inactivation by pulsed electric field (PEF). The model is based on the electroporation theory of individual membrane damage, where spherical cell geometry and distribution of cell sizes are assumed. The variation of microbial cell sizes was assumed to follow a statistical probability distribution of the Gaussian type. Surviving kinetics was approximated by Weibull equation. The dependencies of two Weibull parameters (shape n and time tau, respectively) versus electric field intensity E and width of cell diameters distribution were studied. 相似文献
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D. Fachin A. Van Loey A. VanLoey Indrawati L. Ludikhuyze M. Hendrickx 《Journal of food science》2002,67(5):1610-1615
ABSTRACT: Polygalacturonase (PG) was extracted from tomato fruit. The inactivation kinetics of the PG crude extract was investigated under isothermal and isobaric-isothermal conditions. Thermal inactivation of tomato PG in the temperature range 58 to 65 °C could be described by a fractional conversion model, and in the temperature range from 70 to 90 °C by a biphasic model. Pressure-temperature inactivation (range 300 to 600 MPa/5 to 50 °C) of tomato PG could be described by a fractional conversion model, which points to first-order inactivation kinetics of a pressure-sensitive enzyme fraction and to the occurrence of a pressure-stable PG fraction. A mathematical model describing the influence of pressure and temperature on the inactivation rate constant was formulated. 相似文献