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。     

在S101型钒催化剂上二氧化硫氧化过程的本征动力学研究

本文叙述了在等温良好的二段反应器内,在细颗粒S101型钒催化剂上二氧化硫氧化过程的本征动力学的研究结果。在模拟工业条件下进行了广泛的动力学数据测定,第一次成功地将序贯法用于二氧化硫氧化过程动力学的研究,根据十组基本实验数据,用非线性最小二乘法求出竞争模型的参数估算值。利用离散度最大原理选择补充实验条件,从十一个竞争模型中筛选出适定的等效模型。应用最小联合置信容积准则精估了模型参数。在全操作区内,推荐的二氧化硫氧化过程的本征速率方程式是:     

TS-1催化环己酮氨氧化反应本征动力学模型

由TS-1催化环己酮氨氧化反应机理出发,分析了反应过程的特点及反应规律,根据推测的机理,建立了反应本征动力学模型.结合搅拌釜中测得的动力学数据,对动力学模型进行了参数估值及模型筛选.结果表明,假设反应合乎羟胺机理、双氧水吸附、表面反应为控制步骤时所导出的模型能较好地拟合实验数据,并满足统计检验.根据该动力学模型,通过模拟计算对部分操作条件进行了分析和优化.     

基于直流内阻和交流阻抗特性的铝空气电池输出特性分析

基于二阶RC等效电路模型与工作机理,建立铝空气电池直流内阻特性模型、交流阻抗特性模型和U-I输出特性模型,研究操作条件变化对电池工作性能的影响。通过研究电池在不同操作条件、不同电流密度工作下的直流内阻特性曲线、电化学阻抗谱图以及U-I输出特性曲线的变化规律,分析操作条件变化对电池总内阻与输出性能的影响规律。仿真和实验结果表明,模型具有较高的准确性;操作条件对电池交流阻抗特性与U-I输出特性有明显的影响作用;不同操作条件下电池的交流阻抗谱图和U-I输出特性曲线具有对应的变化规律和量化关系,通过研究操作条件对这两者的影响作用,可为后续操作条件优化、电池输出性能提升奠定基础。     

重油催化裂解集总动力学模型研究

建立了重油催化裂解七集总动力学模型,给出了模型的反应网络和数学表达式.利用小型固定流化床实验装置对大庆常压渣油进行了催化裂解实验,获得求取动力学参数的实验数据.提出了一个新的基于原料性质和操作条件的裂解催化剂失活模型.结合实验数据,编程求取了集总模型的动力学参数,催化裂解的反应活化能基本上都大于100kJ/mol,介于催化裂化活化能和热裂化活化能之间.根据所建立的集总动力学模型,预测了原料转化率、裂解产品产率和分布随操作条件的变化趋势,发现重油催化裂解宜采用高温、短油气停留时间的操作方式.     

钙钛矿型致密膜透氧过程的应用研究

对钙钛矿型致密膜的透氧过程进行了实验研究,验证了所建数学模型的正确性,并对数学模型中的材料参数、应用范围、模型对厚度的敏感性及模型在极限条件下的适用性等进行了分析研究,力图实现以模型为手段,优化实验操作条件,用模型来预测不同工艺条件对膜透氧速率的影响,减少探索性实验的工作量,进而为实现其工业化应用提供指导。     

环氧丙烷开环聚合反应的工程研究 (Ⅱ)间歇和半连续操作时聚醚的数均分子量和双键度

本文通过实验考察了间歇和半连续操作时聚醚的数均分子量和双键度与反应条件之间的关系,并在此基础上,运用数学方法导出了这种操作方式下聚(?)的数均分子量和双键度的半经验模型。经实验结果的检验,这些半经验模型具有较高的准确性。     

浆态反应器中苯氯化反应的宏观动力学

采用自行设计的三相鼓泡浆态实验反应器 ,在半连续操作条件下 ,通过改变催化剂粒度 ,消除了内扩散的影响 ;测定了不同催化剂浓度、通氯量以及苯回流量条件下的苯氯化反应的宏观动力学数据。建立了宏观动力学模型 ,并由实验数据估计出模型参数 ,模型计算值和实验值吻合较好     

在管壁式催化反应器中苯气相氧化为顺酐的研究 (Ⅰ)催化剂,化学计量学及反应动力学

研究了苯气相氧化为顺酐用的 V-Mo-P-Ni-α-Al_2O_3系催化剂,筛选出顺酐收率最大时的最佳配方,并用等离子射流法将氧化铝载体喷涂在反应器壁上,然后喷涂活性组分及助剂,获得了良好效果。苯氧化反应的化学计量关系不仅取决于系统中所含的物种数目及类别,且与所使用的催化剂有关。在所研制的催化剂上进行了苯氧化反应实验,操作条件范围如下:689～724K;原料气空速0.092～0.22mol/(h·g);苯浓度0.5～1.98%。根据实验结果提出了相应的化学计量式,筛选出最佳反应动力学模型。     

苯酚废水萃取工艺的模拟研究

运用流程模拟软件Aspen Plus模拟苯酚废水萃取过程。在所建模型的基础上筛选出合适的萃取剂为1,1,1-三氯乙烷。通过模拟研究了萃取相比、萃取温度、萃取级数等操作条件对萃取结果的影响,为离心萃取机选型及萃取条件的选定提供参考。     

Adsorption/desorption models: How useful for predicting reaction rates under cyclic operation

A computational study is reported of the behaviour of three catalytic reaction models containing conventional adsorption, desorption, and surface reaction steps under conditions of forced composition cycling in a mixed reactor. The models contained varying degrees of non-linearity. With long cycle periods, the time-average rate of reaction asymptotically approached the quasi-steady state. Time-average rate behaviour was found to be bounded by the asymptotes of quasi-steady state rate under slow cycling, and the relaxed steady state under rapid cycling. It is concluded that the approach used until now to model catalytic reactions is very likely inadequate to describe the dynamics of forced cyclic operation observed in a number of experimental systems     

Modeling of Methane Oxidative Coupling under Periodic Operation by Neural Network

A set of feed forward multilayer neural network models have been proposed to predict CH₄ conversion, C₂ and ethylene selectivity of methane oxidative coupling under periodic operation. These parameters predicted by the proposed neural network are based on cycle period, cycle split, and CH₄ and O₂ mole fractions in the first and second part of the period. Due to the dynamic nature of periodic operation and the kinetic complexity of the investigated reactions, the proposed approach is an effective tool to model the system. The agreement between model predictions and experimental data was quite satisfactory. The models could be employed to optimize the experimental conditions in order to get better output from the catalytic reaction. It is concluded that the neural network is an effective tool for modeling catalytic chemical reactions under periodic operation.     

Influence of oscillating external pressure on gas-phase reactions in porous catalysts

It is shown that the effectiveness factor of an isothermal, first order, gas-phase catalytic reaction may be increased by operation under conditions of oscillating total pressure. The mathematical analysis considers two models. An Eulerian model, based on the bulk diffusion control and high permeability limit of the dusty gas model, is used to study the simple isomerization reaction. To extend the results to polymerization and cracking reactions which experience volume change, a Lagrangian model which neglects diffusion is developed. Solutions from both models agree in the limit of large Thiele modulus. It is in this limit that the pressure oscillation technique shows greatest promise for improving catalyst performance. Perhaps the most important conclusion of the present analysis is that pressure oscillations also show promise as a means to control the selectivity of complex reactions.     

THREE-WAY CATALYTIC CONVERTER MODELING AND APPLICATIONS

The advent of stricter U.S. and European exhaust emissions regulations has increased the need for reliable 3-way catalytic converter models supporting the design of demanding exhaust systems for low-emitting vehicles. Although a number of tunable models have been presented in the literature, their efficient performance in actual 3-way applicaions requires further development and validation. The major difficulties posed in such modeling efforts arise from the complexities in the reaction schemes and the respective rate expressions for the multitude of currently used catalyst formulations. This paper addresses the details of tuning and real world application of a two-dimensional catalytic converter model, which accounts for the HC (hydrocarbons) and CO oxidation, as well as NO reduction reactions. The model features a number of innovations regarding the catalyst transient behaviour modelling and the reaction kinetics scheme. The advanced oxygen storage submodel presented is capable of accounting for the redox and temperature dependence of the oxygen availability under transient operation. The redox sensitivity of the reaction scheme allows to get clearer insight in the “lambda-window” behavior of 3-way catalysts. It is concluded, that mathematical modelling may successfully describe important aspects of real world three-way catalytic converter operation under dynamic conditions, and thus, is a valid tool in exhaust aftertreatment systems optimization.     

A recycle reactor for measuring hydrogen isotope exchange kinetics under vapour phase and trickle bed conditions

A recycle reactor system has been developed to measure the activities of catalysts for isotope exchange between hydrogen gas and water vapour. To allow testing of reasonably large quantities of catalysts, the reactor was operated with a high recirculating flow of hydrogen gas passing through a saturator to provide the water vapour required for the reaction. In this mode of operation, only a small spiking gas flow was required as feed compared to the very high feed flow that would be required for once-through operation. The reactor was also operated as a trickle bed by recirculating the saturator water. By testing catalysts under both vapour and trickle bed modes, it was possible to investigate the effect of trickling water over the catalyst on the catalytic activity. Kinetic exchange rates under vapour phase operation were calculated from both plug flow and well-mixed reactor models. The former model was found to be the appropriate one for the ranges of operating conditions investigated. However, for trickle bed operation, the well-mixed reactor model was found to be the suitable one. Vapour phase and trickle bed tests done with random bed and structured bed catalysts indicated that the gas phase isotope exchange reaction was not impaired by the presence of liquid water in the reactor.     

Performance Enhancement by Unsteady‐State Reactor Operation: Theoretical Analysis for Two‐Sites Kinetic Model

Theoretical analysis of the reactor performance under unsteady‐state conditions was carried out. The reactions are described by two kinetic models, which involve the participation in catalytic reaction of two types of active sites. The kinetic model I assumes the blocking of one of the active sites by a reactant, and the kinetic model II suggests a transformation of active sites of one type into another under the influence of the reaction temperature. The unsteady‐state conditions on the catalyst surface are supposed to be created (i) by forced oscillations of temperature and concentration in the reactor inlet (periodic operation of reactor) and (ii) by catalyst circulation between two reactors in a dual‐reactor system (spatial regulation). The influence of various parameters like concentration of reactant, cycle split, length of period of forced oscillations, temperatures and the ratio of catalyst volumes in the dual‐reactor was investigated with respect to the yield of the desired product. It is shown that for both cases of unsteady‐state conditions (periodic reactor operation as well as in a dual‐reactor system), a mean reaction rate predicted by the kinetic model I was up to two times higher than the steady‐state value. The kinetic model II shows a 20 % increase of the selectivity towards the desired product.     

Kinetic Modelling in Automotive Catalysis

There are no general accepted models for CO and HC oxidation and NO _x reduction in automotive catalysis. Many factors affect the observed kinetics e.g. the catalyst preparation method and conditioning, the composition of the exhaust gases, mass and heat transfer, and all the reaction conditions that the catalyst has been exposed to prior to an experiment. However, most experiments are done under idealized conditions with a fresh catalyst and without water, SO₂, etc. Simple models will only describe the individual experiments and more complex models require determination of the parameters from independent measurements under realistic conditions. The kinetic models available in the literature are only reliable for the exact catalyst and reaction conditions for which they have been developed.     

Numerical analysis of a reactive extrusion process. Part II: Simulations and verifications for the twin screw extrusion

A newly designed extruder reactor for grafting vinyl monomers onto polyolefins was studied experimentally and theoretically. The process was made up of a self‐wiping co‐rotating twin screw extruder with a separated reaction zone and two vent zones. The reactive extrusion was performed using a linear low density polyethylene, vinyltrimethoxysilane and di‐t‐butylperoxide under different operation conditions. For the purpose of process analysis, we built a computer simulation based on the reaction kinetics and rheological models studied in the preceding paper. The flow field in the extruder was calculated by the flow analysis network (FAN) method with non‐isothermal non‐Newtonian flow conditions. The iterative procedure was organized to predict local pressure, filling factor, cumulative residence time and temperature along the extruder. Furthermore, we succeeded in representing the profiles of reaction conversion and shear viscosity. Calculated results showed good agreements with the experimental data.     

Keggin型硅钨酸高效催化一锅法合成β-氨基酮衍生物

温和条件下,以硅钨酸为催化剂,酮、芳香醛和芳香胺为原料,三组分"一锅法"合成了15个β-氨基酮衍生物,并考察了反应条件对产率的影响。该反应条件温和,操作简单且产物易分离,产率较高。     

多孔球形催化剂颗粒的随机网络模型

提出了一种多孔球形催化剂颗粒随机网络构造方法,并以等温一级不可逆反应为例,对催化剂孔道网络内发生的反应扩散过程进行了模拟计算。模拟结果表明,计算出的曲折因子既是孔网络配位数的函数,又随Thiele模数的变化而不同,在纯扩散条件下测得的有效扩散系数只能应用于扩散影响不严重的反应扩散区域。同时对在不同的网络模型上的模拟结果进行了分析,并对各自得出的结论之间存在的分歧进行了解析。