氧浓度强制振荡下的丙烯氨氧化反应过程

<正>自从70年代初有学者对催化反应过程的强制振荡操作进行实验研究以来,人们已越来越注意到,对于某些催化反应过程,采用合适的强制周期振荡操作条件比相应的稳态操作产生更优的反应效果,尤其是一些催化氧化反应过程,国内外已有许多研究者开展了大量的实验研究,发现在一定强制振荡周期及振幅操作下能显著提高反应速率（转化率）、主产物的选择性及收率。同时,有许多周期性反应体系的数学模拟理论研究也表明强制振荡操作能     

氧浓度振荡操作下的丙烯氨氧化反应动态动力学模型

针对Mo-Bi系催化剂作用下的丙烯氨氧化反应过程，采用氧浓度的强制周期振荡操作，根据理论推导和所定义的催化剂表面活性中心分率α，得到了丙烯转化率X及丙烯腈选择性SAN的动态动力学模型如下。进而结合在不同振荡操作周期，不同振幅条件下所采集到的实验数据，确定了模型参数，并进行优化计算得到最佳的振荡操作条件，丙烯腈周期平均收率达81．1％，比非振荡操作时提高了3．09个百分点。     

强制浓度周期振荡对丙烯部分氧化反应的影响

研究了强制浓度周期振荡对丙烯在 Mo-Co-Bi 氧化物催化剂上部分氧化制丙烯醛的影响。实验考察了在不同强制振荡周期与振幅下的丙烯转化率和丙烯醛选择性及收率的变化,并与稳态反应条件下的结果作了比较。发现丙烯浓度的各种脉冲方式及氧浓度的微量脉冲方式均可改善反应性能,但氧浓度的全脉冲方式效果不佳。对强制周期操作效应的机理作了探讨。     

列管式固定床反应器振荡操作研究——以Bang-Bang控制方法产生强制振荡

本文研究了以Bang-Bang控制产生强制振荡的列管式反应器的操作特性.对邻二甲苯催化氧化反应,以热点温度作为控制参数,进行Bang-Bang控制,使反应器在振荡状态下操作,与定态操作相比,苯酐收率提高3%.Bang-Bang控制比传统定值控制提供了更多的工程操作手段,具有更多的灵活性.     

振荡反应的化学动力学原理

在学习化学的过程中,老师们经常运用一些有趣的化学实验来激发学生的兴趣,振荡反应就是被通常用来达到这样的教学目的反应之一。振荡反应到底是一个什么样的反应呢？它的反应机理是什么？有些老师并不十分了解。     

B-Z类化学振荡反应研究的非催化化学振荡反应

<正>以溴酸盐为氧化剂的化学振荡反应首先是由Belousov发现的,Zhabotinsky对这一反应的研究大大激发了化学家们对这类振荡反应的兴趣,在短短的几十年时间里,发现了大量新的振荡体系,以后把以溴酸盐为氧化剂的化学振荡反应总称为B-Z类振荡反应。一非催化振荡反应的发现:第一个B-Z类非催化化学振荡反应体系是没食子酸(GA表示)-KBrO_3-H_2SO_4组成的反应体系。     

外部强制对CO催化氧化动力学影响的Monte Carlo模拟

利用Monte Carlo方法研究了外部强制过程对CO催化氧化反应过程中振荡动力学行为的影响规律。研究结果表明:通过矩形脉冲可以有效地调控振荡的动力学行为,在一定的脉冲振幅和脉冲宽度下,通过改变矩形脉冲的周期,CO催化氧化出现了短周期振荡、双峰振荡等不同的动力学行为。当强制过程即矩形脉冲的周期小于自发振荡的周期时,可以观察到短周期振荡行为,当矩形脉冲的周期大于自发振荡的周期时,可以观察到双峰振荡等动力学行为。振荡动力学的改变主要是因为强制振荡过程使得催化剂表面发生了从氧化态向还原态的转变。     

化学振荡反应研究进展

本文概述了化学振荡的概念及其基本原理，综述了化学振荡在分析化学、临床诊断、生命科学研究、工业生产等方面的应用的研究进展。     

化学振荡反应在分析检测中的应用

化学振荡反应是一种特殊而又普遍存在的化学反应现象,在分析检测应用学中具有极大发展潜力。本文分为三个部分,第一部分就化学振荡反应在分析检测中的应用进行概述,第二部分进行简单的B-Z振荡反应体系下检测镉离子实验,第三部分进行展望。     

特征函数法在动力学模型研究中的应用

用特征函数法求解分布参数系统中的偏微分方程，状变量用包含特征函数的双正交基函数展开，可以降低方程组维数，比较动态实验获得的特征函数与模型计算值，作为竞争模型鉴别依据，并以丁烯氧化脱氢作为对象，说明该方法在动态动力学模型参数与模型鉴别上有的有效性。     

PARAMETER ESTIMATION IN EXPONENTIAL MODELS

Abstract. In this paper the problems of parameter estimation and order determination of an exponential (EX) model are studied in the time domain. In order to estimate the parameters, the parameter equations of an EX model are given in terms of the autocorrelation function, which is similar to the Yule-Walker equations of an autoregressive moving-average model. Estimates of parameters are obtained with the aid of the parameter equations and theorems are proved relating the convergence rate and asymptotic distribution of the estimates. We present two kinds of methods for estimating the order and prove that the estimates of the order are consistent.     

PARAMETER ESTIMATION OF MONOD KINETICS WITHOUT BIOMASS DATA AND INITIAL SUBSTRATE CONCENTRATION

The uniqueness of the parameters in a Monod kinetics model estimated from substrate depletion and product growth data were analyzed using nonlinear regression. The initial substrate and biomass concentrations were considered as unknown (unmeasured) parameters. Simulated data containing known measurement errors were generated first using specified parameters and then these data were used for the analysis. Sensitivity coefficients were determined by differentiating the original differential equations of the Monod kinetics. A procedure for determining the scale factors for the parameters (used in the nonlinear regression method) has also been developed. The number of parameters that can be determined uniquely depends on the region of substrate depletion (first order, mixed order or zero order). The availability of product data leads to additional estimation of parameters in the mixed order region. The number of parameters that could be estimated are identified qualitatively by the sensitivity coefficient analysis and quantitatively by analyzing the orthonormal eigenvectors of the Gauss-Newton matrix in the nonlinear regression algorithm. Experimental data on aerobic and anareobic substrate depletion were used to estimate the parameters and validate the analysis.     

试差矩阵熬及其在复杂反应动力学研究中的应用

本文提出了一种研究高维拟一级复杂反应动力学的新方法——试差矩阵法.该方法充分运用有效的数学方法和计算技术,以减少实验工作量,并能大大减少待定参数个数,提高估值精度.研究表明,该方法具有良好的方法统计特性,能耐受较大的实验误差。本文还提出了新的八碳芳烃临氢异构化和六碳组份重整体系的反应网络,应用试差矩阵法成功地研究了这两个体系的双曲型动力学模型,求取了各模型参数,模型拟合值与实验值能很好地吻合.     

低温液相甲醇合成反应动力学模型与参数估计

由低温液相甲醇合成的反应机理出发 ,考虑了均相和多相催化剂的不同作用及不同的吸附方式 ,导出了两步法低温液相甲醇合成的动力学模型 .结合搅拌釜中测得的动力学数据 ,对动力学模型进行了筛选和参数回归 .结果表明氢气为分子吸附 ,反应为双位吸附反应 ,甲醇脱附为反应控制步骤的反应动力学模型能较好地拟合实验数据 .由此得到了低温液相甲醇合成反应动力学模型方程 ,模型满足F检验 ,且参数符合各自的物理意义 .该动力学模型由于是对两步反应综合起来进行动力学分析 ,因而结果可在反应器数学模型中应用     

REACTION MECHANISM AND FORCED CONCENTRATION OSCILLATION CHARACTERISTICS OF BENZENE OXIDATION PROCESS

By combining results of transient response tests with forced concentration oscillation experi-ments,behaviors of benzene oxidation over V_2O_5 catalysts has been determined.Product increse canbe observed during periodic operation.The mechanism of catalytic reaction can be elucidated andthe behavior of concentration oscillation during the reaction is determined.The relation betweencycling frequency and response characteristics has also been studied with two different types of peri-odic operation,i.e.,regular and irregular square waves.     

PARAMETER ESTIMATION OF FICK'S LAW DRYING EQUATION

Distributed parameter drying models such as the Fick's law diffusion model, unlike the lumped parameter model of van Meel whose parameters can be easily estimated by regression, suffer from the difficulty in estimating the parameters of the models quantitatively with accuracy. In the past they were estimated by visual inspection of the theoretical drying curves which fit the experimental drying curve best In this work, a quantitative parameter estimation technique originally suggested by Chavent, is developed by minimizing the integrated squares of error between theoretical and experimental curves over the drying lime (the criterion) subjected to the constraints that the theoretical curve is governed by the constant diffusivity Fick's taw diffusion equation (the constraint). Although the estimation of Fick's law constant diffusivity can be done by using the analytical solution developed by Crank, the use of the Fick's law model here is simply to demonstrate the utility of the proposed technique which can be used in more complex distributed models. The optimization problem is to solve for the adjoint equation for which the value of the Fick's law diffusivity minimizes the criterion. The Lagrangian derivative is solved by using a discrete derivative of the criterion. The theoretical curves are generated by using simple explicit (FSE) and modified Crank-Nicholson (FCR) algorithms The drying of oil palm kernels are used as a case study. Ii is found that the estimated diffusivities of moisture in oil palm kernels range from 0 5 to 5.0 × 10^-10 m²sol;s which are comparable with published data. It is also found that the estimated diffusivity is dependent on the initial moisture content.     

PARAMETER ESTIMATION OF FICK'S LAW DRYING EQUATION

ABSTRACT

Distributed parameter drying models such as the Fick's law diffusion model, unlike the lumped parameter model of van Meel whose parameters can be easily estimated by regression, suffer from the difficulty in estimating the parameters of the models quantitatively with accuracy. In the past they were estimated by visual inspection of the theoretical drying curves which fit the experimental drying curve best In this work, a quantitative parameter estimation technique originally suggested by Chavent, is developed by minimizing the integrated squares of error between theoretical and experimental curves over the drying lime (the criterion) subjected to the constraints that the theoretical curve is governed by the constant diffusivity Fick's taw diffusion equation (the constraint). Although the estimation of Fick's law constant diffusivity can be done by using the analytical solution developed by Crank, the use of the Fick's law model here is simply to demonstrate the utility of the proposed technique which can be used in more complex distributed models. The optimization problem is to solve for the adjoint equation for which the value of the Fick's law diffusivity minimizes the criterion. The Lagrangian derivative is solved by using a discrete derivative of the criterion. The theoretical curves are generated by using simple explicit (FSE) and modified Crank-Nicholson (FCR) algorithms The drying of oil palm kernels are used as a case study. Ii is found that the estimated diffusivities of moisture in oil palm kernels range from 0 5 to 5.0 × 10^-10 m²sol;s which are comparable with published data. It is also found that the estimated diffusivity is dependent on the initial moisture content.     

MASS-PRODUCTION OF BIOCATALYST-ENTRAPPING ALGINATE GEL PARTICLES BY A FORCED OSCILLATION METHOD

A forced oscillation method applying reverse-piezo electric effect has been proposed for mass-production of biocatalyst-entrapping polymer gel particles. A jet of aqueous alginate solution flowing out through an orifice was disintegrated into droplets by an oscillating pressure which was exerted by a ceramic plate vibrated by the reverse-piezo electric effect. The droplets formed were immediately solidified into gel particles in calcium chloride solution.

The particle production rate by the method was up to 270 particles s^-1 or 1 × 10^-6m³.s^-1 The size of the particles produced were down to I mm depending on the applied frequency. The smallest matrix size of the gel's polymer network was estimated to be around 5 nm.

The method was applied for immobilization of yeast cells. The diameter of immobilized particles was 2.5 mm. The immobilized yeast grew well in the particle. The damage of yeast cells caused by the immobilization was not remarkable