共查询到19条相似文献,搜索用时 62 毫秒
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对影响脂肪酶活性、稳定性和对映选择性的因素,如有机深剂和反应温度等首先进行了优化。其次,使用悬浮于环已烷的粉末状游离脂肪酶作生物催化剂,成功地构建了一个高效的非水相游离酶连续搅拌釜反应器。当使用高度反应性的丙酸酐作为薄荷醇的酰基给体,进行连续的酶促对映选择性酯化反应时,醇的转化率在两周内可保持40%以上,所生成酯的光学纯度超过95%e.e。但是,当使用相应的游离丙酸(而不是酸酐)作酰基给体时,薄荷 相似文献
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离子液体和有机溶剂中薄荷醇催化选择性酯化 总被引:1,自引:0,他引:1
研究了离子液体和有机溶剂中(dl)-薄荷醇立体选择性酯化反应。结果表明,在疏水性离子液体[BMIM][PF6]和正己烷介质中的薄荷醇酯化率较高。通过对反应温度、孵育时间和回收次数等影响因素的测定,发现离子液体[BMIM][PF6]作为酶催化反应介质具有比正己烷更大的优势。尤其是酯酶在离子液体中孵育60 d后表现出的活性增大为原来的2.5倍,而正己烷中的酶活性则在两天内变为原来的60%。此外,离子液体在回收利用中表现的优势更说明它作为绿色溶剂替代传统有机溶剂的巨大潜力。 相似文献
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薄荷醇是工业上应用广泛的一类重要的环萜醇.光学活性的左旋薄荷醇在医药卫生方面可用作清凉剂、止痒剂、杀菌剂等;在香料行业是需求量最大的环状单萜醇,可用作日化香精的调配剂,还能充作多种食品的调味剂;其需求量正大幅度增加,因此寻求一种好的拆分外消旋体薄荷醇的方法是极其重要的.主要综述了目前国内外薄荷醇拆分的一些方法,比较了这些拆分方法的优缺点,其中生物酶法拆分是一个很有发展潜力的方法. 相似文献
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分别测定了2-萘基丙酸类药物萘普生R-,S-对映体在有机溶剂中的酶促酯化反应初速度,并研究了反应温度,酰基受体和有机溶剂等反应条件对脂肪酶的反应活性和对映选择性的影响。在一定范围内,酶反应活性随温度升高而增加,温度过高易使酶失活;酶选择性则随温度升高而下降;反应温度以35 ̄40℃为佳。 相似文献
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连续法固体超强酸催化酯化反应的研究 总被引:2,自引:0,他引:2
以SO2-4/TiO2型固体超强酸为催化剂,在固定床反应器上,通过连续法考察了乙酸与乙醇酯化反应的情况。确定了反应的最佳条件:加料速度10mL/h,反应温度100℃。在该条件下,起始物90%可转化为产物酯。同时考察了该催化剂对其他几种酯化反应的催化情况,并与硫酸催化作了对比,结果表明本方法优于硫酸法 相似文献
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模拟连续直接酯化过程的数学模型 总被引:2,自引:0,他引:2
根据引进装置运行状况,将原始的物料衡算、反应动力学方程及汽液相平衡等结合起来,推导出数学模型:模拟酯化阶段各釜操作过程,并编制成相应的应用软件。计算结果与原始参数吻合,与装置实际运行情况一致。为调整工艺,指挥生产提供了依据。 相似文献
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Multiplicity analysis gives practical guidance for process design to eliminate difficult operating regions associated with input and output multiplicities. Continuous stirred tank reactors (CSTRs) present challenging operational problems due to complex behavior such as input and output multiplicities, ignition/extinction, parametric sensitivity, and nonlinear oscillations. In the absence of a unified mathematical theory for representing various nonlinear system characteristics, the present study was aimed at understanding the dynamic behavior of CSTRs by means of experiments and to link the experimental data to theoretical considerations for further detection and elimination of operating problems. Theoretical modeling and analysis of a non‐isothermal CSTR with acid‐catalyzed hydrolysis of an acetic anhydride system for input multiplicity are discussed. Theoretical modeling of a non‐isothermal CSTR using a root‐finding technique was carried out for predicting steady‐state temperatures. Alternatively, a mathematical model for a non‐isothermal CSTR using unsteady‐state mass and energy balance equations is proposed. Computer‐based simulation was carried out using a program developed in MATLAB for final transient temperature and time‐temperature data of the CSTR system under investigation. The results of a theoretical analysis conducted for confirming the existence of input multiplicity in non‐isothermal CSTRs with acid‐catalyzed hydrolysis of acetic anhydride were compared with experimental investigations for validation. 相似文献
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Fast Production of Diacylglycerol in a Solvent Free System via Lipase Catalyzed Esterification Using a Bubble Column Reactor 下载免费PDF全文
Manman Liu Junning Fu Yinglai Teng Zhen Zhang Ning Zhang Yong Wang 《Journal of the American Oil Chemists' Society》2016,93(5):637-648
In this study, diacylglycerols (DAG) were synthesized rapidly (~30 min) in a solvent‐free system via esterification of glycerol with fatty acids (FA, the mixture of 60 wt% palm oil deodorizer distillate and 40 wt% oleic acid) catalyzed by Lipozyme 435 (Novozymes A/S, Copenhagen, Denmark) using a bubble column reactor. The content of DAG, monoacylglycerols (MAG), triacylglycerols (TAG) and free fatty acids (FFA) in the crude product were 57.94 ± 1.60 wt%, 24.68 ± 2.08 wt%, 2.67 ± 1.72 wt% and 14.69 ± 1.22 wt%, respectively under the selected conditions, which were enzyme load of 5.0 wt%, glycerol/FA mole ratio of 7.5, initial water content of 2.5 wt%, reaction temperature of 60 °C, reaction time of 30 min and N2 gas flow of 10.6 cm min?1. The final product containing 91.30 ± 1.10 wt% of DAG was obtained by one‐step molecular distillation at 200 °C. The reusability of Lipozyme 435 was investigated by evaluating the esterification degree (ED) and the DAG content in the crude products in 30 successive runs. The enzyme retained 95.10 % of its original activity during 30 successive runs according to comparison of the ED. The new process showed a very high efficiency in production of DAG with a high purity. The ratio of positional isomers 1,3‐DAG to 1,2 ‐DAG was 2:1 in the final product. The certain plasticity (melting point of 44 °C) and content of unsaturated fatty acids made the product a valuable food ingredient. 相似文献
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Jichen Qin 《Chemical engineering science》2006,61(18):6154-6164
A model of continuous melt transesterification of bisphenol-A and diphenyl carbonate in a continuous stirred tank reactor is developed using phase equilibria assumption and the method of molecular weight moments. The model equations can be simplified into a polynomial system that has 17 equations and 17 unknowns. Solution of the polynomial system gives out almost every aspects of the continuous transesterification process. Molecular weight and polydispersity index, end group ratio of hydroxyl to phenyl carbonate, contents of molecular species, and lost diphenyl carbonate fractions are studied in different operation parameters. 相似文献
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N.S. Jayakumar A. AgrawalM.A. Hashim J.N. Sahu 《Computers & Chemical Engineering》2011,35(7):1295-1303
The continuous stirred tank reactor is a dynamic system exhibiting nonlinear behavior such as multiplicity and oscillations and, in certain range of operating conditions, may exhibit a parametric sensitivity where small changes in one or more of the input parameters lead to large changes in the output variable. In the present work, hydrolysis of acetic anhydride reaction system was used to demonstrate the existence of parametric sensitivity with respect to the input parameter, the cooling water flow rate. The applications of parametric sensitivity analysis were used for detection of parametric sensitivity in a continuous stirred tank reactor using catalyses hydrolysis of acetic anhydride reaction system. Also, theoretical investigation revealed that the effect of wall capacitance has definite influence on the dynamics of continuous stirred tank reactor. The continuous stirred tank reactor showed parametric sensitivity both in the regions of uniqueness and multiplicity, and a mathematical model was developed for the reactor. The numerically simulated results are in satisfactory agreement with the experimental data. 相似文献
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Delia Teresa Sponza Hakan Çelebi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(7):961-975
BACKGROUND: The antibiotics in industrial and munipical wastewaters could not be removed effectively in conventional anaerobic and aerobic biological treatment plants. Few studies have been performed to investigate the biodegradation and inhibition kinetics of oxytetracycline (OTC) on methanogens and total volatile fatty acids (TVFA). RESULTS: A high rate anaerobic multichamber bed reactor (AMCBR) was effective in removing the molasses‐chemical oxygen demand (COD), and the OTC antibiotic with yields as high as 96% at an influent OTC loading rate of 133.33 gOTC m?3 day?1 at a hydraulic retention time (HRT) of 2.25 days. Increasing the OTC loading rates from 22.22 gOTC m?3 day?1 to 133.33 gOTC m?3 day?1 improved both hydrolysis and specific utilization of molasses‐COD. The inhibition constants of TVFA (KI?TVFA?meth) and OTC (KI?OTC?meth) on methanogens decreased at OTC loadings > 133.33 gOTC m?3 day?1. The direct effect of OTC loadings > 133.3 gOTC m?3 day?1 on acidogens and methanogens was evaluated using the Haldane inhibition kinetic. CONCLUSION: OTC antibiotic was effectively removed in a sequential AMCBR/completely stirred tank reactor (CSTR). The Haldane inhibition constant (KID) decreased significantly at high OTC loads indicating the increase in toxicity. Copyright © 2012 Society of Chemical Industry 相似文献
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Identification and Characterization of a Novel Thermophilic,Organic Solvent Stable Lipase of <Emphasis Type="Italic">Bacillus</Emphasis> from a Hot Spring 下载免费PDF全文
A novel lipase gene lip256 was cloned and identified from the genomic library of hot spring strain Bacillus sp. HT19. The deduced amino acid sequence of lip256 has less than 32% identity to a predicted esterase (Cog1752) from Photobacterium leiognathi lrivu.4.1 and contains a novel motif (GTSAG) that differs from other clusters in the lipase superfamily. Following purification, a single band was obtained with a molecular mass of 33 kDa by SDS-PAGE, and the optimal temperature and pH for lipolytic activity of Lip25 were 70 °C and 9.0, respectively. Lip256 exhibited high activity at high temperatures, with 40% maximum activity at 80 °C and good stability at temperatures ranges between 50 and 80 °C. Additionally, the enzyme was highly stable in the presence of butyl-alcohol, glycerol, acetonitrile, pyridine, and urea. However, the presence of acetone, methanol, trichloromethane, petroleum ether, hexane, tert-butanol, isopropanol, dithiothreitol, ethylenediaminetetraacetic acid, polyhexamethylene biguanide, dimethyl sulfoxide, benzene, Triton X-100, Tween-20, Tween-80, and sodium dodecyl sulfate suppressed or absolutely inhibited enzyme activity. Furthermore, Ca2+, Mg2+, and Cu2+ suppressed enzyme activity, whereas Na+, Fe3+, K+, Fe2+, and Sr2+ enhanced enzyme activity. The unique characteristics of novel lipase Lip256, including its thermo-alkaliphilic performance, high tolerance toward metal ions, inhibitors, and detergents, and high stability in organic solvents, implied that this enzyme might be an interesting candidate for industrial processes. 相似文献
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Effects of mixing on the rate of second-order chemical reactions have been studied by measuring the time-average degree of conversion at enough points in a steady-state, continuous-flow stirred reactor to provide comparisons with numerical simulations of the same reactions using a standard Reynolds-averaged turbulence simulation code with an added closure. The reactants were introduced in widely separated feed streams in order to provide a difficult test for the measurements and simulations. Concentration and segregation measurements were made with two fluorescence based methods - one remote and one using a fiber optic probe. The rates of mixing and reaction were simulated using the Corrsin mixing term and the Spalding segregation production term with the Paired-Interaction reaction closure term. 相似文献