Sorption Accompanied by Chemical Reaction on Zeolites

The importance of zeolites as catalysts hardly needs to be emphasized. In the recent past the research activity in this area registered a noticeable increase after the discovery of ZSM-type zeolites. A single-step conversion of methanol into a mixture of hydrocarbons, predominantly in the gasoline range, would have been considered highly improbable before this discovery. Apart from their unusual shape selectivity, the low coking character of these zeolites is of particular importance to industrial practice. The discovery has clearly demonstrated promise for further research on the synthesis of new types of zeolites and exploration of novel reactions on zeolite catalysts. The exponential increase in research activity [68, 220] observed over the last 10 years is evidence of worldwide recognition of the potential of zeolite catalysts.     

Sorption Accompanied by Chemical Reaction on Zeolites

The importance of zeolites as catalysts hardly needs to be emphasized. In the recent past the research activity in this area registered a noticeable increase after the discovery of ZSM-type zeolites. A single-step conversion of methanol into a mixture of hydrocarbons, predominantly in the gasoline range, would have been considered highly improbable before this discovery. Apart from their unusual shape selectivity, the low coking character of these zeolites is of particular importance to industrial practice. The discovery has clearly demonstrated promise for further research on the synthesis of new types of zeolites and exploration of novel reactions on zeolite catalysts. The exponential increase in research activity [68, 220] observed over the last 10 years is evidence of worldwide recognition of the potential of zeolite catalysts.     

A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix

Particle size distribution affects strongly physical and mechanical properties of filled polymers. The proposed model uses agglomerate size population balance in its new mathematical formulation expressing agglomeration, break‐up and erosion as an evolution of one particle subjected to mean‐filed type interaction with others. The erosion parameters have been calculated with experiments in an internal mixer. Controlled breakup of agglomerates was carried out through capillary dies to evaluate breakup parameters. Calcium carbonate filled polypropylene system was used to validate the formulation.     

Mass Transfer to a Semi-infinite Medium Accompanied by Reversible Chemical Reactions

A mathematical method is developed for deriving asymptotic relationships for the mass-transfer acceleration factor at the boundary of a semi-infinite medium. This method is applied to systems described by arbitrary first- and second-order kinetic equations. The relationships derived are valid at large values of time. A linear and two nonlinear problems are considered as an example. An expression for the acceleration factor in a reversible chemical reaction is derived for the first time. The potential of the method is limited by the assumption that the diffusion coefficients of all reactants are equal.     

反应动力学贯串的化学反应工程教学思路及教学案例

化学反应工程是一门工程学科.学生在掌握基本概念的同时,需要与实验研究、工程实践相结合,培养分析、解决工程问题的能力.我们基于化学反应工程课程教学,提出了以反应动力学作为主线,贯串化学反应工程的教学思路,同时结合自身科研实践及工程实例,使学生能直观、系统地掌握知识点,为工程实践打下坚实的基础.     

Analysis of the Operation of a Nonisothermal Flow Reactor in Terms of the Relaxation Model of Longitudinal Dispersion

A set of equations and additional conditions for the relaxation model of longitudinal dispersion are proposed to describe the operation of a nonisothermal reactor. The near-perfect-mixing, adiabatic, and near-isothermal steady-state modes of operation of a mixing apparatus are analyzed. The analysis is performed for a irreversible first-order chemical reaction. For the adiabatic mode, the problem formulation is relevant to an isothermal reactor with a modified mass source. The perfect-mixing mode is illustrated by analytical and graphical data on the number of solutions of the model equations.     

Nonlinear Heat and Mass Transfer with Consideration of Deformation in a Chemical Reaction Wave

A new approach is developed to perform mathematical modeling of heat transfer with consideration of deformation of a physical system in a chemical reaction zone. This approach describes boundary conditions using fractional differential-integral calculus. A numerical analysis using the model proposed is undertaken to examine processes during nonlinear heat transfer accompanied by deformation of a physical system due to intense gas release in chemical reactions, particularly in processes of the production of materials by self-propagating high-temperature synthesis.     

相际传质(二) 具有一级不可逆化学反应液相传质的表面膜更新修正模型

本文将修正的表面膜更新模型用于具有一级不可逆化学反应的液相传质,导得了如下的数学模型: 本文对于用“化学法”测定相际面积的问题作了分析,提出了反应穿透时间θ_K和溶质反应几尽的渗透深度σ_K的概念;并以k_1θ=2作为吸收已趋稳定状态的条件,拟定了一个计算相际面积和表面更新频率的方法。还用这方法处理了一些文献数据,并与Danckwerts模型作了比较。     

Phase Disequilibrium in the Course of an Exothermic Reaction Accompanied by Liquid Evaporation in a Catalytic Trickle-Bed Reactor

-Methylstyrene hydrogenation in a fixed catalyst bed is studied experimentally and theoretically for a cocurrent downflow of the gas and liquid. Gas-phase hydrogenation on dry catalyst granules disturbs the liquid–vapor phase equilibrium. A dimensionless parameter related to the Raoult–Dalton law for a liquid–vapor mixture is suggested to characterize phase disequilibrium in the system.     

Properties of Diagrams of Equilibrium Open Evaporation Accompanied by Instantaneous Chemical Reactions

The rules of embedding various chemical equilibrium manifolds into a concentration simplex are established. An approach to the synthesis of equilibrium distillation diagrams for the instantaneous reaction A₁ + A₂ A₃ + A₄ is suggested. The number of possible diagram types is determined, and diagram classification is reported.     

Limiting Phenomena in the Reaction of Fluorine with Hydrogen

Reactions involving energy branching and deceleration by the end product were studied using as an example the reaction of fluorine with hydrogen. It has been shown that for such reactions, entrance into the autoignition region determined by static conditions (reagent concentration, pressure, and temperature) due to variation in the pressure of the mixture may be or may not be accompanied by mixture autoignition. The parameter determining the behavior of a particular mixture is the rate of variation in the mixture pressure. A process of fast (in the range of seconds) preparation of fluorocarbon mixtures with minimal yield of hydrogen fluoride is substantiated.     

综合案例法在化学反应工程教学中的应用研究

化学反应工程学是一门研究涉及化学反应的工程问题的学科,是化工和应化等工科专业的专业基础课,在培养化工类专业人才中起着由理论到工程、由基础到专业的桥梁作用。本文提出"综合案例"教学法,以实际工程案例专题为例介绍了该方法在化学反应工程课程中的应用情况和实施效果。实践证明,综合案例式教学法优于传统教学法,实用性和趣味性较强,有助于加强和巩固学生的学习能力。     

Matlab在微分法求反应级数和速率常数中的应用

Matlab是Mathworks公司推出的适用于科学和工程计算的数学软件系统,可高效地解决数值线性代数、微分方程数值解、最优化等科学和工程问题,以Matlab语言编写程序,用于确定物理化学实验乙酸乙酯皀化反应级数和速率常数,与传统手工作图相比,可避免人为因素的误差,简便快捷,计算结果和所作的图形均符合实验要求。     

氨合成反应化学平衡常数计算模型的研究

针对目前氨合成反应化学平衡常数计算模型所存在的问题，提出一种基于径向基函数网络并结合主成分回归方法的网络模型。试验结果表明，该模型用于氨合成反应化学平衡常数的计算，效果良好。     

用热力学方法分类化学反应

本文阐述了用热力学方法以自由能，熵、焓等物理量相互变化关系来分析化学反应，判断化学反应的可能性。     

Profile of Chemical Potential in Pressure-Driven Membrane Processes Accompanied by Gel-Enhanced Concentration Polarization

Abstract

A model for distribution of chemical potential and concentration polarization enhanced by gel accumulated on membrane surface has been proposed. It provides distribution of chemical potential and concentration in the liquid phase and within the gel layer. The model allows analyzing the influence of thickness of fouling gel layer on the CP degree, surface concentration and chemical potential.

The model is based on the following assumptions:

1. process is accompanied by accumulation of gel layer at membrane surface along with concentration polarization;

2. diffusion layer and deposited gel consist of different components and these layers are characterized by different values of diffusivity coefficients;

3. correlation for effective hindered back diffusion coefficient within deposited layer is adopted from [Boudreau, Geochim. Cosmochim. Acta, 60, 1996];

4. transverse transport is based on the following mechanisms: convection due to pressure difference and back diffusion owing to concentration gradient.

The following conclusions have been drawn: (A) diffusion resistance within the gel layer is getting dominant and cannot be ignored; (B) In the presence of a gel layer the membrane surface concentration, C_1M, is enhanced due to hindered back diffusion of salt ions that in turn, results in growth of osmotic pressure and chemical potential at the membrane surface. It provides elevated salt concentration in permeate and decreases the net driving force; (C) Analysis of calculated data indicates high sensitivity of CP degree to coefficient of hindered back diffusion within gel layer.     

Longitudinal Dispersion of the Continuous Phase in Spray Extraction Columns

Longitudinal dispersion of the continuous phase was studied in spray extractors operated in the loose, close, and turbulized drop packing modes. The Peclet number was found to depend on the Reynolds number modified to take into account the hydrodynamic conditions in the working zone of the column. When the continuous phase is pulsed, the Peclet number is also governed by the modified Reynolds number, which accounts for the effect of pulsation on the longitudinal dispersion.     

Comparison between the Diffusion and Relaxation Models of Longitudinal Dispersion

The properties of the relaxation (wave) model of longitudinal dispersion are considered. The diffusion and relaxation models of longitudinal dispersion are compared. It is shown that, depending on its coefficients, the relaxation model can be assigned to two main classes and one intermediate class provided the boundary conditions for the model equations are correctly formulated. New equations are obtained, whose solutions are asymptotically close to the solutions of the diffusion model.     

Longitudinal Dispersion of the Dispersed Phase in Spray Extraction Columns

Theoretical Foundations of Chemical Engineering -     

三传一反结合模型的化学反应工程教学思路

化学反应工程是化学工程与工艺类专业的一门核心专业课,具有较强的工程性特点,学生缺乏工程经验,通常较难理解。基于化学反应工程课程的教学尝试,提出了以反应动力学表达式为中心、三传一反结合的教学模型,形成贯穿化学反应工程的教学思路,使学生能系统的掌握知识点,为进一步提高学生分析和解决实际工程问题的能力打下基础。