乙烯环氧化反应的动态特性与反应器的动态操作(Ⅰ)——基元过程序列结构与动力学

利用动态响应方法,对乙烯在银催化剂上环氧化反应的基元过程序列结构和动力学进行了系统的实验和模型化研究,为从理论上考察这一反应体系在浓度强制振荡条件下的时间平均性能与基元过程动力学的相互关系,为建立适当的模型来描述浓度强制振荡过程提供了必要的条件.     

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。     

基于B-Z化学振荡反应过程的简化与软件分析

以Belousov—Zhabotinskii反应的Oregonator模型为基础,依据FNK机理,对振荡过程进行了简化,给出了分步基元反应的动力学参数和非线性的常微分方程,借助数学软件Matlab和Maple对方程进行了图解,并与实验数据进行了对比,该文提出的简化分析模型能较好地预测组分的初始浓度和振荡频率。     

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。     

强制振荡条件下的催化反应过程和机理

综述近十多年来催化反应过程强制化学振荡的理论、实验研究和动力学数学模拟研究。强制化学振荡能改善和强化反应过程,特别是强制浓度振荡,在一定的周期操作条件下,能显著提高反应速率,改善平行反应产物的选择性和收率。     

碳酸乙烯酯和乙醇均相酯交换反应研究

研究了以乙醇钠为均相催化剂,碳酸乙烯酯和乙醇酯交换合成碳酸二乙酯同时联产乙二醇的过程。考察了催化剂浓度、醇酯比、温度等因素对反应的影响,得到较适宜的工艺条件。以加成-消除机理为基础,分别以两步亲核加成基元反应为速率控制步骤,提出了两个动力学模型,用Runge-Kutta法和非线性最小二乘法估计了相应的模型参数。统计检验表明,两个模型在所研究的压力、温度和组分的浓度范围内均是适用的。     

001×7(732)阳离子交换树脂催化醋酸甲酯水解反应过程模拟与优化

在充分搅拌和可忽略粒度影响条件下,测定了间歇搅拌反应釜中001×7(732)阳离子交换树脂催化醋酸甲酯水解反应动力学数据,建立了其拟均相与非均相反应动力学模型,进行了模型筛选和参数估值.结果表明,醋酸甲酯与水均吸附,表面反应为控制步骤的非均相反应动力学模型能较好地拟合实验数据,并满足统计检验.根据优选的反应动力学模型,对醋酸甲酯水解过程进行了模拟计算,考察了反应温度、树脂浓度、水酯摩尔比对水解过程的影响,得到的优化反应条件为:反应温度55℃、树脂浓度260 g·L-1、水酯摩尔比1.5∶1.此时反应90 min接近醋酸甲酯平衡水解率34.8%.     

膦铑催化剂对丁二烯系共聚物中C=C键加氢的模拟研究

采用分子模拟方法研究对C=C键的催化加氢过程,构建了各基元反应中的分子模型,并通过构建动力学模型计算了各分子所具有的能量,从而计算出各基元反应的能量变化,揭示了各基元反应的机理,最终解释三苯基膦氯化铑催化剂在丁二烯系共聚物中对C=C键催化加氢的反应机理。     

CSTR中生化反应振荡行为研究

考虑在生化反应中细胞收率系数Ｙｘ／ｓ随物料浓度变化这一事实，改进了原有的发酵动力学方程，同时首次运用分岔理论研究了乙醇连续发酵过程中存在的振荡现象。结果表明：在低糖浓度条件下，振荡的周期和幅值以及振荡出现的入口浓度阈值都将随着稀释率和入口糖浓度的变化而变化     

化学动力学模型筛选与特征函数法

采用强制振荡实验方法,对特征函数法应用于化学反应模型筛选进行了研究。数值模拟结果表明,竞争反应模型在某些操作条件下,特征函数分布差异很大,以此操作条件做实验,就能筛选出真实反应机理模型。     

THE DYNAMIC BEHAVIOR OF A FIXED-BED STEAM-OXYGEN COAL GASIFIER DISTURBED BY WATER INFLUX II. MODEL DEVELOPMENT AND VERIFICATION

A one-dimensional transient model has been developed to simulate the unsteady-state behavior of a fixed-bed coal gasifier disturbed by water injection. The resulting set of differential equations was solved numerically using a finite difference method. The validity of the model was first tested against the steady-state experimental data on the product gas composition and the gas production rate for different feed conditions, and the model has been further extended to include transient operation of the gasifier. The dynamic analysis includes the quantitative validation of the system response to changes in the feed condition—either a step change or a rectangular-pulse type change. The simulation results show that the dynamic behavior has a quite different trend in the product gas composition than equilibrium models predict. Such a discrepancy occurs because dynamic behavior is controlled by the changes in the gasification reaction rate rather than a shift in equilibrium The controlling mechanism can be elucidated in terms of the relative contribution by each gasification reaction.     

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.     

化学反应器的动态操作

尽管1938年就申请了化学反应器动态操作的第一个专利,但是化学反应器人为非定态操作作为一种具有吸引力的新技术和与之相联系的复杂理论仍然是化学反应工程研究的一个新领域.本文简要地综述了这一领域的发展历史、研究现状和未来的前景.对有关的基本科学问题、关键的实验与计算分析技术做了初步讨论.为了促进在动态催化和不同尺度化学反应系统强制周期操作方面更系统、深入的研究,提出了若干建议.     

微分反应器中多相催化反应动态过程的模拟分析

动态响应方法可以为多相催化反应过程提供较多的反应机理的信息。与实验研究顺序相反,本文通过模拟微分反应器中多相催化反应的动态过程,分析了不同基元反应速率常数对 Eley-Riddeal 型机理和 Langmuir-Hinshelwood 型机理的动态响应曲线的影响。以利于阐述动态响应方法的基本思想。     

DYNAMIC SIMULATION OF A DISTILLATION COLUMN SEPARATING A MULTICOMPONENT MIXTURE

In this work, a dynamic model was developed to simulate the transient behaviour of a pilot scale, continuous, siagewise, 15 plate distillation column separating a mixture of ethanol, iso-propanol and isobutanol. The accuracy of the predictions was assessed by transient response data collected during experiments under step changes in reflux ratio, feed flow rate and feed composition.

Results demonstrated the feasibility of simulating multicomponent distillation under unsteady state conditions with fairly good success. Further improvements were suggested for a better accuracy     

MODIFICATION OF PRODUCT DISTRIBUTION THROUGH PERIODIC OPERATION: FISCHER TROPSCH SYNTHESIS OVER Ru/A12O3

Forced concentration cycling was used to study the feasibility of rate and selectivity enhancement in FT synthesis. Our results indicate that it is possible to increase the time averaged rate of reaction by as much as 210% over the equivalent steady state rate. The improvements in selectivity are more complex. In general concentration cycling leads to increased rates of methane production. Under certain operating conditions it is possible to enhance the selectivity to propane by as much as 400% over the equivalent steady state rate. Selectivity enhancements for ethane and butane were also observed

Analysis of the transient response data indicates that perhaps there are separate sites for methane and higher hydrocarbon synthesis. Transient response experiments showed that higher hydrocarbons are always produced before methane. During transient response and periodic operation methane production was found to be in phase with water production     

MACROPROCESS OF PARTICLE FORMATION IN SUSPENSION POLYMERIZATION OF STYRENE WITH INORGANIC STABILIZER SYSTEM

The macroprocess of particle formation from suspension droplets of styrene in a pdymerizationsystem was investigated.Inorganic hydroxyapatite or its mixture with polyvinyl alcohol as thepolymerization system was used.Those items such as the effects of the Weight fraction of dispersed-phase,the amount of the inorganic stabilizer and the agitation speed on the breakup and coalescence of thetransient dispersed drops etc.Were examined.Results showd that the dynamic behavior of the transi-ent polymer droplets changed in the presence of the suspension stabilizer during the reaction.     

MODELING OF THE TRANSIENT AND STEADY STATE OPERATION OF A FLUIDIZED BED REACTOR WITH ADAPTIVE CONTROL OF TEMPERATURE

This paper concerns modeling of the transient and the steady state operation of a fluidized bed reactor for the catalytic ammoxidation of propylene to acrylonitrile. To maintain constant the temperature of the reaction in order to facilitate the phenomenological study as well as to avoid risks of destruction of the catalyst, a self tuning P.I.D. controller has been used. The controller derived from a discrete P.I.D. regulator is based on pole assignment. It uses a recursive parameter estimator based on the least square method. The reactor has been interfaced with an Apple II micro-computer. The results obtained illustrates the inherent capability of self adaptive control to adapt the change of the environment where conventional control fails

Modeling of the reactor is based on the Kato and Wen bubble assemblage model corrected by including the wake of the bubbles with their clouds, as proposed hy Stergiou. This modified model gives good predictions of the operation of the reactor for steady as well as transient operation.