青霉素酰化酶基因工程菌 E.coli A_(56)(pPA22)水解青霉素 G 的动力学

用初速度法测定了青霉素酰化酶基因工程菌 E.coli A_(56)(pPA22)游离细胞和固定化细胞水解青霉素 G 的动力学常数,并进行了动力学模型的检验。该菌体酶活高,米氏常数小,固定化后米氏常数和苯乙酸抑制常数增大,底物抑制常数和6-APA 抑制常数没有变化。通过青霉素 G 裂解过程的考察,验证了青霉裂解动力学模型的适用性及动力学常数测定的可靠性。     

The relationship between thermal decomposition properties of titanium hydride and the Al alloy melt foaming process

Using a new temperature programmed decomposition (TPD) theory and related experimental technique, a set of thermal decomposition kinetics equations of titanium hydride can be acquired by separating and simulating its TPD spectrum. According to these equations, the relation curve of decomposition quantity and time for titanium hydride at temperature of 940 K is obtained and the result coincides well with the Al alloy melt foaming process, which provides a scientific basis for controlling the Al alloy melt foam and then the Al alloy foams with different pore structure are successfully prepared.     

分子筛催化合成MTBE反应失活动力学

在改性β分子筛液相催化异丁烯与甲醇合成MTBE反应动力学的基础上,考察了内扩散阻力和催化剂失活对醚化反应的影响。假设符合平行失活机理,建立了带内扩散阻力的失活动力学方程,通过实验数据拟合确定了失活动力学参数。计算结果表明,醚化失活机理符合平行失活机理,异丁烯与甲醇合成MTBE的同时,发生副反应生成积碳是失活的原因。该失活动力学方程能很好地拟合试验数据,统计检验表明在置信度为99%以下是适合的。用所建失活模型预测了反应温度、催化剂颗粒度及进料时间对催化剂相对活性、有效因子和异丁烯转化率的影响。     

阴离子交换树脂吸附镉的动力学研究

研究了强碱性阴离子交换树脂吸附镉的主要动力学因素。通过实验找出了过程的限制环节，推算出交换反应的活化能、反应级数及动力学方程。     

Adsorption Characteristics of Oxide Coated Buoyant Media (ρs<1.0) for Storm Water Treatment. I: Batch Equilibria and Kinetics

Urban rainfall-runoff mobilizes and transports significant loads of metal species. Promulgation of National Pollutant Discharge Elimination System Phase II regulations has spurred development of Unit Operations and Processes (UOPs) Best Management Practices (BMPs) for control of metal species. Recent UOP designs provide both adsorption and filtration using engineered media such as manganese oxide coated polymeric media (MOPM). Divalent metal species adsorption onto a manganese oxide coated polymeric medium was evaluated through batch adsorption experiments using a flowthrough batch reactor. Freundlich isotherms were utilized to fit the experiment data. For the media examined, MOPM, adsorption is pH dependent and results indicate a favorable solute pH range of >6 for metal species adsorption. The relative adsorption affinity of MOPM for four divalent metal species typically found in storm water is Pb(II)>Cu(II)>Cd(II)>Zn(II). Adsorption rates were rapid for this flowthrough batch system with over 50% removal in the first 30 min and over 90% removal within 5 h at a surface loading rate of 500 mL/cm2?min. The pH drift patterns, due to surface complexation, during each experiment, coincided with the metal species removal rate curve. Study results indicated that the inclusion of a thin manganese coating can significantly increase media adsorption capacity. MOPM has a comparable adsorption capacity for the divalent metal species compared to other commercial and research media.     

Adsorption Characteristics of Oxide Coated Buoyant Media (ρs<1.0) for Storm Water Treatment. II: Equilibria and Kinetic Models

Divalent metal species adsorption onto a manganese oxide coated polymeric medium (MOPM) was evaluated through batch adsorption experiments using a flow-through batch reactor. In this paper, Part II, the batch equilibrium and kinetic data examined in Part I are modeled using a triple layer surface complexation model and a potential driving second order kinetic model. Surface complexation modeling using FITEQL-TLM generated intrinsic surface acidity constants for the MOPM of log?K?a1int = 3.196 and log?K?a2int = ?5.802. The intrinsic surface reaction constants for Pb(II), Cu(II), and Zn(II) were log?K?Pbint = ?1.91, log?K?Cuint = ?2.53, and log?K?Znint = ?4.45, respectively. A potential driving second order kinetic model was developed to predict sorption of the divalent metal ions onto the MOPM. The general adsorption kinetics for MOPM can be described as a fast reaction occurring within 30 min and a slower reaction continuing from 5 to 15 h. Kinetic results can be interpreted using assumptions of the potential driving second order model that the dominant control forces are the chemical potential of the MOPM activated surface sites and chemical potential of sorbate in the solution.     

Understanding CO2 electrochemical reduction kinetics of mixed-conducting cathodes by the electrical conductivity relaxation method

Electrochemical reduction reaction is an important approach to utilize CO₂ and convert it into valuable products. Exceptional reaction kinetics at a high temperature of solid oxide electrolysis cells (SOECs) attracts particular attention. In this work, we propose to investigate CO₂-RR kinetics using a new theoretical method based on the electrical conductivity relaxation (ECR) technique on a typical mixed-conducting Sr₂Fe_1.5Mo_0.5O_6-δ (SFM) electrode. Three kinetic parameters that are commonly adopted in the typical electrochemical test experiments consisting of overpotential, current density and area-specific resistance (ASR) are derived. The overpotential resulted from the difference in the oxygen partial pressure is caused by the change of CO₂ partial pressure, while current density from the surface reaction rate constant. Accordingly, area-specific resistance, as well as overpotential-current density relationship, can be derived. We believe that this work brings a new method to study the kinetic process of CO₂ electrolysis and to evaluate the electrocatalyst activity of developed new electrode materials as well as to benefit the designing of novel electrode electrocatalysts for highly efficient solid oxide electrolysis cells.     

Carotene Degradation and Isomerization during Thermal Processing: A Review on the Kinetic Aspects

Kinetic models are important tools for process design and optimization to balance desired and undesired reactions taking place in complex food systems during food processing and preservation. This review covers the state of the art on kinetic models available to describe heat-induced conversion of carotenoids, in particular lycopene and β-carotene. First, relevant properties of these carotenoids are discussed. Second, some general aspects of kinetic modeling are introduced, including both empirical single-response modeling and mechanism-based multi-response modeling. The merits of multi-response modeling to simultaneously describe carotene degradation and isomerization are demonstrated. The future challenge in this research field lies in the extension of the current multi-response models to better approach the real reaction pathway and in the integration of kinetic models with mass transfer models in case of reaction in multi-phase food systems.     

Solid-state NaBH4 composites for hydrogen generation: Catalytic activity of nickel and cobalt catalysts

Hydrogen generation from tablets of sodium borohydride with chlorides of nickel and cobalt was studied. The nickel catalysts were shown to be less active in the borohydride hydrolysis than the cobalt catalysts. One of the reasons for the lower activity of the nickel catalyst was the presence of hydrogen on its surface, which hampered the adsorption of reactants. The addition of cobalt to the nickel catalyst increases the hydrogen generation rate. This is due to the introduction of active metal with low adsorption capacity for hydrogen and the higher dispersion of the active component.