苏云金杆菌生长的结构动力学模型

考察了苏云金杆菌(Bt)的间歇及流加培养.根据对Bt间歇发酵实验现象的分析和讨论,提出了一个基于Williams分室模型的四组分结构模型,并从实验数据确定了各组分的初值.该模型能较好地拟合Bt间歇发酵实验数据.从间歇发酵获得的模型参数推算出流加培养曲线与实验值也基本吻合.     

Kinetics of formation of carbon dioxide clathrate hydrates

The new experimental apparatus capable of observing the clathrate hydrate formation kinetics was developed in this study. Experimental data on the kinetics of carbon dioxide hydrate formation were carefully measured. The experiments were carried out in a semi-batch stirred tank reactor with stirring rate of 500 rpm at three different temperatures between 275.2 and 279.2 K and at pressures ranging from 2.0 to 3.5 MPa. The kinetic model was adopted to predict the growth of hydrates with only one adjustable parameter which represented the rate constant for the hydrate particle growth. The model was based on the crystallization theory coupled with the two-film theory for gas absorption into the liquid phase. The model predictions matched the experimental data very well with the largest deviation of 7.18%, which is within experimental error range. This study is the first for the kinetic data of carbon dioxide hydrate formation and important in developing carbon dioxide fixation process using clathrate hydrate phenomenon.     

Production of Bacillus thuringiensis‐based biopesticides in batch and fed batch cultures using wastewater sludge as a raw material

Bacillus thuringiensis subsp kurstaki was grown in batch and fed batch cultures using wastewater sludge as a raw material. A simple fed batch strategy based on dissolved oxygen measurement during the fermentation cycle was developed in this work. It was established that while shifting the process strategy from batch to fed batch, the maximum spore concentration was increased from 5.62 × 10⁸ to 8.6 × 10⁸ colony forming units per cm³ and resulted in an increase of entomocidal activity from 13 × 10⁹ to 18 × 10⁹ spruce budworm potency units per dm³. Higher entomotoxicity was recorded at low spore concentration using wastewater sludge as a raw material whereas low entomotoxicity was reported at high spore concentration in synthetic medium. Copyright © 2005 Society of Chemical Industry     

Modeling reaction kinetics of rigid polyurethane foaming process

A theoretical model was developed to simulate the polyurethane foaming process for a rigid foam. In the model, multiple ordinary differential equations were solved by MATLAB and the model was able to predict temperature profiles by inputting foam recipe information. This initial study on foam modeling focusses on reaction kinetic parameters that were fitted to experimental temperature data as a function of time. The modeling was able to accurately model temperature profiles of single‐polyol polyurethane formulations and was able to accurately predict temperature profiles of mixtures based on pure component kinetic parameters. A primary goal of this work is to expedite the ability to develop new foam formulations by simulation—especially for incorporation of new bio‐based polyols into formulations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1131‐1138, 2013     

Integrated B2B‐NMPC control strategy for batch/semibatch crystallization processes

The uncertainty in crystallization kinetics is of major concern in manufacturing processes, which can result in deterioration of most model‐based control strategies. In this study, uncertainties in crystallization kinetic parameters were characterized by Bayesian probability distributions. An integrated B2B‐NMPC control strategy was proposed to first update the kinetic parameters from batch to batch using a multiway partial least‐squares (MPLS) model, which described the variances of kinetic parameters from that of process variables and batch‐end product qualities. The process model with updated kinetic parameters was then incorporated into an NMPC design, the extended prediction self‐adaptive control (EPSAC), for online control of the final product qualities. Promising performance of the proposed integrated strategy was demonstrated in a simulated semibatch pH‐shift reactive crystallization process to handle major crystallization kinetic uncertainties of L‐glutamic acid, wherein smoother and faster convergences than the conventional B2B control were observed when process dynamics were shifted among three scenarios of kinetic uncertainties. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Modeling elastic and viscous effects on the texture of ribbon-shaped carbonaceous mesophase fibers

Carbonaceous mesophases are discotic nematic liquid crystals that are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a wide range of different fiber textures and cross-sectional shapes. Circular planar polar (PP), circular planar radial (PR), ribbon planar radial (RPR), and ribbon planar line (RPL) textures are ubiquitous ones. This paper presents, solves, and validates a model of mesophase fiber texture formation based on the classical Landau-de Gennes theory of liquid crystals, adapted here to carbonaceous mesophases. The effects of fiber cross-sectional shape and elongational flow on texture formation are characterized. Emphasis is on qualitative model validation using existing experimental data [1]. The role of elasticity and flow-induced orientation on texture selection mechanism on ribbon-shaped mesophase fibers is characterized. The model is able to predict the formation of the commonly observed line texture, and the fine structure of the line is reproduced and explained in terms of classical liquid crystal defect physics. The results provide additional knowledge on how to optimize and control mesophase fiber textures.     

Study of the bioaccumulation kinetic of lead by living aquatic macrophyte Salvinia auriculata

In the present work, the lead phytoaccumulation by living free floating aquatic macrophytes Salvinia auriculata was investigated in a greenhouse. These plants were grown in lead-doped hydroponic solutions forming, as a function of time, six collections of nutrient media, roots and leaves of plants from a batch system. The synchrotron X-ray radiation fluorescence technique was used in order to determine element concentrations in the nutrient media, dry roots and aerial parts of plant. The aquatic plant-based lead removal data were described by using a non-structural kinetic model. According to the experimental data, both adsorption and bioaccumulation mechanism are present and a competition between the phosphorus macronutrient and lead for plant growth was observed, when great concentration of lead in roots is present. The non-structural kinetic models have shown good agreement with the lead uptake experimental data in all the investigated cases. The results of living macrophytes S. auriculata-based-metal bioaccumulation kinetic parameters can be used in artificial wetlands to predict the heavy metal removal dynamics from wastewaters.     

Refinement of the kinetic model for guaiacol hydrodeoxygenation over platinum catalysts

In our prior work (Ind Eng Chem Res, 2015, 54, 10638-10644), hydrodeoxygenation (HDO) kinetics of guaiacol, a well-known model compound of bio-oil, over Pt/AC (activated carbon) catalysts were investigated under integral operating conditions. It was found that the pseudo-homogeneous plug-flow model utilizing these kinetics describes the experimental observations well (with normalized RMS error = 7.6%). In the present work, under differential operating conditions instead, we refine the kinetic model for the same reaction network over the same catalyst. We show that among the five reaction steps in the network, the reaction order of one step differs from our prior work, while the orders remain unchanged for the other four steps. The activation energies of two steps differ from our prior values by 10–15 kJ/mol, and for the other three steps remain essentially consistent with our prior work. The kinetic parameters from the present work are used to predict fixed-bed reactor performance under integral operating conditions as well. The comparison between experimental and predicted values for both the prior and new sets of data is excellent and even better than our prior model (with reduced normalized RMS error = 4.2%). The kinetic analysis additionally proposed that the direct and indirect pathways of phenol formation from guaiacol HDO depend on guaiacol conversion values. The present work demonstrates that kinetic expressions and parameters obtained from a gradientless differential reactor are more reliable and can be used to successfully predict integral reactor performance data.     

Modeling batch crystallization processes: Assumption verification and improvement of the parameter estimation quality through empirical experiment design

In this work, experimental data of different batches was used for estimation of the kinetic parameters for the secondary nucleation framework of Gahn and Mersmann [Gahn, C. and Mersmann, A., 1999. Brittle fracture in crystallization processes. Chem. Eng. Sci. 54, 1273–1292].An empirical experiment design procedure was used to design an informative batch experiment through optimization of the seed quality, size and mass and process conditions at seeding. The parameters estimated using the data of the designed experiment showed smaller magnitudes of the confidence ellipsoids and standard deviations as compared to those obtained by using the data of conventional (un)seeded batch experiments. It was shown that the designed experiment allowed reducing uncertainty in the initial conditions, namely, the mass and crystal size distribution of the initial population of crystals and the initial supersaturation.It was also demonstrated that the main reason for the model/process mismatch was the origin of nuclei. Dynamic experimental data could be described better if the state of the crystals forming the crystallization system corresponded to the assumptions of the used kinetic model. Differences in the crystal surface properties, shape, and strain content could be responsible for a divergent nucleation and growth behavior in batches that were initiated either by primary nucleation, seeding with small ground seeds or seeding with coarse crystals from the product of the previous batch.     

放射型根瘤菌分批发酵生产辅酶Q10的代谢特性和发酵动力学

以放射型根瘤菌WSH2601作为辅酶Q10分批发酵的试验菌,对其代谢特性进行了初步研究。对分批发酵过程中细胞生长、产物积累、糖消耗、中间产物有机酸及pH的变化规律进行了描述：由Logistic模型方程分别建立了放射型根瘤菌辅酶Q10发酵过程细胞生长、产物合成及基质消耗随时间变化的数学模型。模型模拟计算结果与实验值能较好地吻合。动力学研究结果表明该模型能较好地反映放射型根瘤菌的细胞生长、底物消耗和产物合成过程及其动力学机制。辅酶Q10分批发酵中细胞生长与产物合成属于半偶联型。     

Salt‐Free Aqueous Extraction of a Cell‐Bound Biosurfactant: a Kinetic Study

A cell‐bound biosurfactant produced by Lactobacillus pentosus was obtained under eco‐friendly conditions and used directly as an emulsifying agent in order to stabilize fluorene/water emulsions. The biosurfactant was extracted from L. pentosus cells with an aqueous phosphate buffer solution in the absence of NaCl. This is important because most the cell‐bound biosurfactants are extracted in the presence of NaCl, which is considered highly phytotoxic. A pseudo‐second order kinetic model best described the batch extraction of the biosurfactant from cells. As expected, the initial extraction rate of the biosurfactant increased with the temperature. Calculation of the activation energy with the Arrhenius equation yielded a positive value, indicating that the process is endothermic. The aqueous solution containing the biosurfactant was able to stabilize fluorene/water emulsions, with relative emulsion values of 62.2 % after 7 days of emulsion formation.     

Lag phase model for transient growth of pseudomonas putida on phenol

The successful design of large‐scale bioreactors requires the ability to predict both steady‐state and dynamic operating conditions. At the same time, mathematical models should not be too complex in order to reduce experimental work required to determine kinetic parameters. A simple model which predicts the behaviour of batch and transient continuous culture operations is presented and experimentally verified. The model is based on two regions of metabolic activity: the lag phase and the active phase. Pseudomonas putida growing on phenol as a substrate in a well‐mixed bioreactor was tested in three modes of operation: batch, continuous start‐up and continuous step‐change. The model is demonstrated to predict all the qualitative aspects of the dynamic phases of growth and is quantitatively accurate.     

Rates and equilibria of ester hydrolysis: Combination of slow and rapid reactions

The kinetics and thermodynamics of ester hydrolysis were studied experimentally in a laboratory-scale batch reactor by using ethyl formate as the model molecule. The effects of the reaction conditions, such as temperature, excess water, complexing agent and initial acid charge upon the ester hydrolysis process were investigated and a kinetic model was developed for the system. Autocatalytic kinetics was observed experimentally, which was due to the carboxylic acid formed during the reaction. The reaction rate was further enhanced and the equilibrium was shifted to the product side by adding a complexing agent into the reaction mixture. A mathematical model comprising the mass balances and rate equations were developed for the system by assuming quasi-equilibrium hypothesis for the reaction involving the complexing agent. A robust calculation scheme was developed for the estimation of the kinetic and thermodynamic parameters from experimental data. The proposed model was able to predict the experimental results satisfactorily.     

Kinetic studies of alkyl formate hydrolysis using formic acid as a catalyst

BACKGROUND: The hydrolysis of methyl formate is the major industrial process for the production of formic acid. The aim of the work is to determine the reaction kinetics quantitatively in the presence of formic acid catalyst, develop a mathematical model for the reaction system and estimate the kinetic parameters for the purpose of optimization. RESULTS: Liquid phase hydrolysis kinetics of alkyl formates (ethyl and methyl formate) was studied in an isothermal batch reactor at 80–110 °C and 20 bar nitrogen pressure. The catalyst of choice was formic acid. The reaction rate was enhanced but the formic acid product yield was slightly suppressed relative to the uncatalysed system. A kinetic model comprising mass balances and rate equations was developed and the kinetic and equilibrium parameters included in the rate equations were estimated from the experimental data with non‐linear regression analysis. CONCLUSION: The model was able to predict the experimental results successfully. The results obtained were compared quantitatively with an earlier model involving alkyl formate hydrolysis in a neutral aqueous solution. Copyright © 2011 Society of Chemical Industry     

Comparison of the Various Kinetic Models of TAME Formation by Simulation and Parameter Estimation

Various kinetic models proposed for the synthesis of TAME (tert-amyl methyl ether, 2-methoxy-2-methylbutane) were tested against experimental batch reactor data. The experiments were carried out with methanol/isoamylenes molar ratios varying from 0.2 to 2.0 at temperatures between 333 and 353 K. The range of validity of the various models was evaluated by simulating the experimental conditions and by comparing the adequacy of the models to predict the experimental changes of composition as a function of the catalyst contact time and composition at reaction equilibrium. Activity-based models were found to predict the experimental results better within a wider range of conditions than the concentration-based models. The activity-based models were additionally compared by estimating the values for the model parameters from the experimental data.     

Polymerization of 1-hexene using α-diimine nickel catalysts: Stochastic simulation of branch distribution

This work presents a new stochastic model to simulate the chain-walking mechanism during the polymerization of 1-hexene with α-diimine nickel catalysts based on the kinetic mechanism and branching data provided in the literature. Poly(1-hexene)s produced present short-chain branches such as methyl and butyl as well as longer chain branches showing very good agreement with the experimental branching data available. The new stochastic model is capable to cope with regioselective insertions of α-olefins and typical occurrence of 1,ω enchainment leading to the formation of longer chain branches and allows the calculation of molar mass and branching distributions. Another important result is that model simulations were able to unveil deficiencies for the kinetic mechanism to accurately predict the branching distribution at low temperatures. It is also shown that model probabilities may be interpreted in kinetic terms and properly correlated to the reaction polymerization temperature.     

Model discrimination and parameter estimation in the kinetic study of methanol synthesis

The new model discrimination method is based on the correlation coefficient test of experimental data sets for different reactions, without requiring a prior parameter estimation. The new parameter estimation method reduces by n the number of dimensions to be tested, compared to the classical method where n is the number of independent reactions in the system. This has reduced the computation time for most complex reactions to a level, comparable to that needed for single reactions. The example used is the kinetic study of methanol synthesis in which the formation rates of methanol, methane, ethanol and ethane are considered. Two adequately accurate models were obtained from an extensive range of plausible models by using the new model discrimination and parameter estimation method with a relatively small computation effort.     

Simulation and Experiment of the Homogeneously Catalyzed Production of Terpenyl Amine

Continuous terpenyl amine production via a homogeneously catalyzed hydroamination is presented. For the recycling of the catalyst a liquid‐liquid system combined with a subsequent acid complexation as capturing step for the terpenyl amine was used. The whole process was run in pilot plant scale. At first, batch experiments were conducted to determine reaction equilibria of the hydroamination and the acid complexation. On this, a process model was developed which is based on equilibrium stages. This process model was validated by running the continuous process and was able to predict the continuous process in good agreement with experimental data. So, it allows a reduction of the experimental effort.     

Optimization of kinetic data for two‐stage batch adsorption of Pb(II) ions onto tripolyphosphate‐modified kaolinite clay

BACKGROUND: Most adsorption studies consider only the adsorption of pollutants onto low cost adsorbents without considering how equilibrium and kinetic data can be optimized for the proper design of adsorption systems. This study considers the optimization of kinetic data obtained for the removal of Pb(II) from aqueous solution by a tripolyphosphate modified kaolinite clay adsorbent. RESULTS: Modification of kaolinite clay with pentasodium tripolyphosphate increases its cation adsorption capacity (CEC) and specific surface area (SSA) from 7.81 to 78.9 meq (100 g)^?1 and 10.56 to 13.2 m² g^?1 respectively. X‐ray diffraction patterns for both unmodified and tripolyphosphate‐modified kaolinite clay suggest the modification is effective on the surface of the clay mineral. Kinetic data from the batch adsorption of Pb(II) onto the tripolyphosphate‐modified kaolinite clay adsorbent were optimized to a two‐stage batch adsorption of Pb(II) using the pseudo‐second‐order kinetic model. Mathematical model equations were developed to predict the minimum operating time for the adsorption of Pb(II). Results obtained suggest that increasing temperature and decreasing percentage Pb(II) removal by the adsorbent enhanced operating time of the adsorption process. The use of two‐stage batch adsorption reduces contact time to 6.7 min from 300 min in the single‐stage batch adsorption process for the adsorption of 2.5 m³ of 500 mg L^?1 Pb(II) under the same operating conditions. CONCLUSION: Results show the potential of a tripolyphosphate‐modified kaolinite clay for the adsorption of Pb(II) from aqueous solution and the improved efficiency of a two‐stage batch adsorption process for the adsorption of Pb(II) even at increased temperature. Copyright © 2009 Society of Chemical Industry     

A novel kinetic model to describe 1,3-propanediol production fermentation by Clostridium butyricum

Clostridium butyricum is one of the best 1,3-propanediol producers due to the nonpathogenic, less byproducts, and energy-efficient fermentation process. In fermentation process, the relationship among substrate, product, and byproducts is intricate and hard to be analyzed. The present study is aimed at establishing a novel kinetic model not only based on biomass, substrate, and 1,3-propanediol, but also considering the byproduct concentration to describe 1,3-propanediol fermentation process by C. butyricum. The simulative result of the model fit well with that in the batch fermentation process. Furthermore, the model was also used to predict the result of fed-batch fermentation process after some modifications. The predicted result of model fit well with the data in experiment when glycerol was controlled at around 10 g/L. Thus, this novel kinetic model could serve as a tool for further optimization of the fermentation process, and could be improved for some other similar processes.