应用阳离子交换树脂催化水解蔗糖Ⅰ.蔗糖非均相催化水解反应动力学

实验选用两种H+型强酸性阳离子交换树脂为催化剂，研究蔗糖在离子交换树脂柱内的非均相催化反应动力学。结果表明，温度每升高10℃，蔗糖在两种离子交换树脂柱内的水解速度分别增加到2．1和3．3倍；蔗糖在两种离子交换树脂柱内水解反应的表观活化能分别为64．96kJ／mol和79．59kJ／mol，其水解反应有明显的扩散控制。     

高分子科学中的平均场理论和1/N展开

利用1/N展开理论考察高分子物理中的几个典型高分子体系.研究发现,平均场理论只有在体系具备一定对称性时才适用.在中性高分子溶液中,不论是单组分、多组分还是嵌段共聚物体系,1/N展开理论对于N取值不小于6时是适用的.对于聚电解质体系,平均场理论仍然可以粗糙地描述弱带电聚电解质的统计性质.对于强带电聚电解质体系,由于体系对称性大为降低,平均场理论不再适用,标度理论或许会是一个适合的方法.     

Ionic liquid near a charged wall: structure and capacitance of electrical double layer

We study the effects of ion size asymmetry and short-range correlations on the electrical double layer in ionic liquids: we perform molecular dynamics simulations of a model ionic liquid between two "electrodes" and calculate the differential capacitance of each as a function of the electrode potential. The capacitance curve has an asymmetric "bell-shape" character, in qualitative agreement with recent experiments and the mean- field theory (MFT) which takes into account the limitation on the maximal local density of ions. The short-range ionic correlations, not included in the MFT, lead to an overscreening effect which changes radically the structure of the double layer at small and moderate charging. With the radius of cations taken to be twice as large as anions, the position of the main capacitance maximum is shifted positively from the potential of zero charge (PZC), as predicted by MFT. An extension of the theory (EMFT), however, reproduces the simulated capacitance curve almost quantitatively. Capacitance curves for real ionic liquids will be affected by nonspherical shape of ions and sophisticated pair potentials, varying from liquid to liquid. But understanding the capacitance behavior of such model system is a basis for rationalizing those more specific features.     

Reversible kinetics of physical adsorption on homogeneous surface

The kinetics of reversible polymolecular adsorption was studied theoretically in main terms of the BET model. A system of equations that describes the adsorption process is derived and the analytical solution of a given system for the finite number of adsorption sites is found. The effect of equilibrium and kinetic parameters of adsorption system on the kinetics of adsorption is analyzed.     

微波等离子体下一氧化碳氢化制乙炔反应中产物的选择性研究(英文)

采用微波等离子体技术研究了一氧化碳氢化制乙炔反应的产物选择性。对影响乙炔选择性的几个因素,如微波输入功率、反应物的比例和体系压力进行了研究。乙炔的选择性随着微波输入功率的增加,反应物比例和体系压力的降低而增大。在最佳条件下,乙炔的选择性可达到９５．８７％,甲烷选择性的变化规律和乙炔相反,乙烯和乙烷的选择性很低。等离子体中的电子温度（或能量）和密度采用了静电悬浮双探针诊断,电子密度和能量受微波输入功率和体系压力的影响。在反应中,电子能量决定化学反应是否进行,电子密度决定产物的组成。根据自由基反应理论解释了乙炔选择性在Ｈ２＋ＣＯ等离子体化学反应中随影响因素的变化规律。     

Hybrid neural network model of an industrial ethanol fermentation process considering the effect of temperature

In this work a procedure for the development of a robust mathematical model for an industrial alcoholic fermentation process was evaluated. The proposed model is a hybrid neural model, which combines mass and energy balance equations with functional link networks to describe the kinetics. These networks have been shown to have a good nonlinear approximation capability, although the estimation of its weights is linear. The proposed model considers the effect of temperature on the kinetics and has the neural network weights reestimated always so that a change in operational conditions occurs. This allow to follow the system behavior when changes in operating conditions occur.     

A Monte Carlo study of proton adsorption at the heterogeneous oxide/electrolyte interface

Adsorption of protons on a heterogeneous solid surface is modeled using the Monte Carlo (MC) simulation method. The surface of an oxide is assumed to consist of adsorption sites with pK assigned according to a quasi-Gaussian distribution. The influence of the electrostatic interactions combined with the energetic heterogeneity of the surface is examined, and the MC results are compared with the predictions of the mean field theory (MFT). It is demonstrated that the heterogeneity affects strongly the shape of the isotherms while it does not change the location of the common intersection point of the isotherms. On the other hand, introduction of repulsive interactions into the system is found to shift the CIP toward lower values of pH. It is also shown that the MFT, in general, describes correctly the behavior of the system. On the contrary the condensation approximation, used to derive relatively simple expressions for the adsorption isotherms, introduces serious errors unless the surface is strongly heterogeneous. Some practical remarks how to eliminate the errors associated both with the MC simulations and with the theory are also presented.     

未添加晶种结晶过程的中后期动力学模拟

以KNO₃-H₂O为模型体系, 考察了未添加晶种的间歇结晶过程动力学, 将历经爆发成核后的结晶体系近似为添加晶种的结晶体系. 并结合光学关联方法, 推导了可描述历经爆发成核后的晶体形成和生长速率模型. 模型中含有可反映结晶固相信息的透光率变量, 从而避免了以往模型仅靠液相浓度数据求解模型参数的不便. 运用该模型拟合未添加晶种结晶过程的中后期实验数据, 得到了KNO₃晶体的二次成核和生长动力学参数, 参数结果与文献中报道的添加晶种结晶过程的参数值相近. 在此基础上, 针对添加晶种的结晶过程, 提出了晶种添加量的定量设计方法, 并得到了实验的初步验证.     

Sensitivity of PSA process performance to input variables

Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.     

固定床F-T合成Fe-Cu-K催化剂3000小时模试

进行了两段法Ｆ－Ｔ合成（ＭＦＴ）Ｆｅ－Ｃｕ－Ｋ催化剂３０００小时模试工艺改进后的适应性,催化剂性及共影响因素,结果表明,ＣＯ转化率达到了７５～８５％,烃选择性达７８～９４％,Ｃ６＾＋产率达８５～１００ｇ／ＮＭ＾３（ＣＯ＋Ｈ２）。     

Removal of heat of adsorption from adsorbent by forced convection

An analytical mathematical model is used to investigate the effectiveness of forced convection for removal of the heat of adsorption from an adsorbent mass undergoing a differential adsorption process in a flow system. An example of such a process is measurement of gas adsorption kinetics using a differential adsorption bed. Isothermal operation may not be achieved even when a high gas flow rate is used, particularly if the sorption kinetics is relatively fast. Very small changes in the adsorbent temperature can cause significant departure from the isothermal uptake behavior when the heat of adsorption is moderately large. A criterion for validity of isothermal data analysis is given.     

Expanded Bed Chromatography as a Tool for Nanoparticulate Separation: Kinetic Study and Adsorption of Protein Nanoparticles

Expanded bed adsorption was investigated together with its suitability for the practical recovery of nanoparticulate mimics of products such as plasmid DNA and viruses as putative gene therapy vectors. The study assessed the binding of protein nanoparticles fabricated from bovine serum albumin (BSA) with average size of 80 nm as a model system and viral size/charge mimic to the streamline DEAE adsorbent in the expanded bed column chromatography. The adsorption kinetics and adsorption mechanism for the BSA nanoparticles on the adsorbent were studied. In batch adsorption studies, the factors nanoparticle concentration, contact time and adsorbent amount, affecting adsorption isotherms were investigated. Subsequently the data were regressed against the Lagergren equation, which represents a first-order kinetics equation and also against a pseudo-second-order kinetics equation. The results demonstrated that the adsorption process followed a Langmuir isotherm equation. The kinetics of the adsorption process followed a pseudo-second-order kinetics model with a rate constant value of 0.025 g mg^?1 min^?1. The dynamic binding capacity of the BSA nanoparticles on an expanded bed was calculated. The recovery of the nanoparticles was more than 85%.     

Some estimates of the surface tension of curved surfaces using density functional theory

Density functional theory is used to calculate the surface tension of planar and slightly curved surfaces, which can be written as gamma(R)=gamma(infinity)(1-2delta(infinity)R), where R is the radius of curvature of the surface. Calculations are performed for a Lennard-Jones fluid, split into a hard-sphere repulsive potential and an attractive part. The repulsive part is treated using the local density approximation. The attractive part is treated using a high temperature approximation (HTA) in which the pair correlation function is approximated by the Percus-Yevick pair correlation function of a uniform hard-sphere fluid evaluated at a position-dependent average density. An expression relating the Tolman length delta(infinity) to the density profile of the planar surface is derived. Numerical results are presented for the planar surface tension gamma(infinity) and for delta(infinity) and are compared with those using mean field theory (MFT) and with those using the square-gradient approximation. Values for gamma(infinity) using the HTA are 30%-40% higher than those using MFT. Values for delta(infinity) using the HTA are around -0.1 (in units of the Lennard-Jones parameter sigma) and only weakly dependent on temperature. These values are less negative than the values from MFT. The square-gradient approximation gives reasonable estimates of the more accurate nonlocal results for both the MFT and the HTA.     

Hydrophobic agglomeration kinetics of fine kaolinite particles in aqueous suspensions

The hydrophobic agglomeration kinetics of kaolinite has been studied through the in-situ turbidity meter measurement system. The effects of surfactant dosage, stirring rate and particle size on the hydrophobic agglomeration dynamics have been investigated. Appropriate surfactant concentrations provided the strongest hydrophobicity, modest stirring rate offered a higher agglomerates formation rate and a lower disruption rate, and smaller particles had lower energy barrier and higher attachment efficiency. The best hydrophobic agglomeration conditions have been determined and a kinetic model of hydrophobic agglomeration has been proposed by experimental results. The kinetic model has been turned out to be fitted to the dynamic process well and can characterize as well as assess the hydrophobic agglomeration kinetics appropriately.     

Cadmium sorption properties of poly(vinyl alcohol)/hydroxyapatite cryogels: I. kinetic and isotherm studies

A new adsorbent for removing heavy metal ions from wastewater, poly(vinyl alcohol)/hydroxyapatite(PVA/HAp) composite cryogel, has been investigated. The PVA/HAp cryogel was prepared through a clean process by using water and freeze-thawing. The PVA/HAp cryogel is provided with interconnected macropores varying from 0.1 um to several um and well dispersed and immobilized HAp in cryogel. Batch experiments of cadmium sorption were carried out to test the sorption ability of PVA/HAp cryogel. The isotherm and kinetics of cadmium sorption were studied by fitting the experimental results to isotherm and kinetics models. The Langmuir isotherm suitable for this system shows the maximum sorption capacity of 53.3 mg/g. For kinetics, the double-exponential model presents best fit compared with pseudo-first-order and pseudo-second-order models. The double-exponential model indicates a diffusion-controlled and a two-step mechanism.     

乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学

通过差示扫描量热仪(DSC)研究了乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学,用Jeziorny和Ozawa方程描述了结晶动力学过程.共混物的结晶温度和结晶焓强烈依赖于淀粉含量和冷却速率.结果表明,随着冷却速率的增加,每个试样的结晶放热曲线均变宽,并向低温区移动.当温度一定高时,所有试样均具有较快的结晶速率. Jeniorzy方程可以较好地描述POE/淀粉共混物的非等温结晶模式,而Ozawa方程对于POE/淀粉共混体系不太适合.     

Oriented attachment kinetics for ligand capped nanocrystals: coarsening of thiol-PbS nanoparticles

In this work, the growth kinetics of thiol-capped PbS nanoparticles was studied. Two-stage growth process was observed, which was controlled first by oriented attachment (OA) mechanism and then by the hybrid Ostwald ripening (OR) and OA mechanism. Different from the NaOH-ZnS system, where OA will occur between any two multilevel nanoparticles, an OA kinetic model only considering the attachment related to original particles was fitted well with the experimental results. Analysis reveals that this model may be a universal one to describe the OA crystal growth process of nanocrystals capped with easily destroyed ligands, such as thiol-ZnS in the previous report. The OA crystal growth characteristics determined by the surface agent were discussed and compared. We propose that with stronger surface capping, the OR growth of nanocrystals is hindered, which facilitates the size controlling via OA kinetics during nanosynthesis.     

Thermal Behavior of Zn(Thr)SO_4·H_2O

IntroductionRecently,a considerable interest has been fo-cused on the complexes of zinc with amino acidsdue to their excellent additives in medicine foodstuff and cosmetics[1— 6] .The investigation on thethermal behavior and the thermochemistry of somezinc amino acids is important to its further applica-tion,which has been reported in references[4,5 ,7— 1 0 ].However,the studies on solid complexZn( Thr) SO4· H2 O has not been reported,whichcan provide the necessary data and the foundation…     

Modelling and simulation of styrene-acrylonitrile emulsion polymerization kinetics

The emulsion polymerization kinetics of the styrene-acrylonitrile system have been studied. A dynamic time-dependent model has been developed, which successfully describes the course of the conversion of styrene as compared with that of acrylonitrile. This model avoids the difficulties encountered by previous models when applied to high acrylonitrile-content polymers, and is able to predict the conversion process for both batch and continuous reactors. The model is aimed at the simulation and operation of composition-controlled semibatch and continuous processes.