Microstructured Devices for Chemical Processing

Faster, cheaper and environmentally friendly, these are the criteria for designing new reactions and this is the challenge faced by many chemical engineers today. Based on courses thaught by the authors, this advanced textbook discusses opportunities for carrying out reactions on an industrial level in a technically controllable, sustainable, costeffective and safe manner. Adopting a practical approach, it describes how miniaturized devices (mixers, reactors, heat exchangers, and separators) are used successfully for process intensification, focusing on the engineering aspects of microstrctured devices, such as their design and main chracteristics for homogeneous and multiphase reactions. It adresses the conditions under which microstructured devices are beneficial, how they should be designed, and how such devices can be integrated in an existing chemical process. Case studies show how the knowledge gained can be applied for particular processes. The textbook is essential for master and doctoral students, as well as for professional chemists and chemical engineers working in this area.

Table of Contents:
Preface XI List of Symbols XIII 1 Overview of Micro Reaction Engineering 1 1.1 Introduction 1 1.2 What are Microstructured Devices? 2 1.3 Advantages of Microstructured Devices 2 1.3.1 Enhancement of Transfer Rates 2 1.3.2 Enhanced Process Safety 5 1.3.3 Novel OperatingWindow 7 1.3.4 Numbering-Up Instead of Scale-Up 7 1.4 Materials and Methods for Fabrication of Microstructured Devices 9 1.5 Applications of Microstructured Devices 10 1.5.1 Microstructured Reactors as Research Tool 11 1.5.2 Industrial/Commercial Applications 11 1.6 Structure of the Book 13 1.7 Summary 13 References 14 2 Basis of Chemical Reactor Design and Engineering 19 2.1 Mass and Energy Balance 19 2.2 Formal Kinetics of Homogenous Reactions 21 2.2.1 Formal Kinetics of Single Homogenous Reactions 22 2.2.2 Formal Kinetics of Multiple Homogenous Reactions 24 2.2.3 Reaction Mechanism 25 2.2.4 Homogenous Catalytic Reactions 26 2.3 Ideal Reactors andTheir Design Equations 29 2.3.1 Performance Parameters 29 2.3.2 BatchWise-Operated Stirred Tank Reactor (BSTR) 30 2.3.3 Continuous Stirred Tank Reactor (CSTR) 35 2.3.4 Plug Flow or Ideal Tubular Reactor (PFR) 39 2.4 Homogenous Catalytic Reactions in Biphasic Systems 45 2.5 Heterogenous Catalytic Reactions 49 2.5.1 Rate Equations for Intrinsic Surface Reactions 50 2.5.2 Deactivation of Heterogenous Catalysts 57 2.6 Mass and Heat Transfer Effects on Heterogenous Catalytic Reactions 59 2.6.1 External Mass and Heat Transfer 60 2.6.2 Internal Mass and Heat Transfer 69 2.6.3 Criteria for the Estimation of Transport Effects 83 2.7 Summary 84 2.8 List of Symbols 86 References 87 3 Real Reactors and Residence Time Distribution (RTD) 89 3.1 Nonideal Flow Pattern and Definition of RTD 89 3.2 Experimental Determination of RTD in Flow Reactors 91 3.2.1 Step Function Stimulus-Response Method 92 3.2.2 Pulse Function Stimulus-Response Method 93 3.3 RTD in Ideal Homogenous Reactors 95 3.3.1 Ideal Plug Flow Reactor 95 3.3.2 Ideal Continuously Operated Stirred Tank Reactor (CSTR) 95 3.3.3 Cascade of Ideal CSTR 96 3.4 RTD in Nonideal Homogeneous Reactors 98 3.4.1 Laminar Flow Tubular Reactors 98 3.4.2 RTD Models for Real Reactors 100 3.4.3 Estimation of RTD in Tubular Reactors 105 3.5 Influence of RTDon the Reactor Performance 107 3.5.1 Performance Estimation Based on Measured RTD 108 3.5.2 Performance Estimation Based on RTD Models 110 3.6 RTD in Microchannel Reactors 115 3.6.1 RTD of Gas Flow in Microchannels 117 3.6.2 RTD of Liquid Flow in Microchannels 118 3.6.3 RTD of Multiphase Flow in Microchannels 122 3.7 List of Symbols 126 References 127 4 Micromixing Devices 129 4.1 Role of Mixing for the Performance of Chemical Reactors 129 4.2 Flow Pattern and Mixing in Microchannel Reactors 136 4.3 Theory of Mixing in Microchannels with Laminar Flow 137 4.4 Types of Micromixers and Mixing Principles 143 4.4.1 Passive Micromixer 144 4.4.2 Active Micromixers 154 4.5 Experimental Characterization of Mixing Efficiency 158 4.5.1 Physical Methods 158 4.5.2 Chemical Methods 159 4.6 Mixer Efficiency and Energy Consumption 171 4.7 Summary 172 4.8 List of Symbols 173 References 173 5 Heat Management by Microdevices 179 5.1 Introduction 179 5.2 Heat Transfer in Microstructured Devices 181 5.2.1 Straight Microchannels 181 5.2.2 Curved Channel Geometry 189 5.2.3 Complex Channel Geometries 191 5.2.4 Multichannel Micro Heat Exchanger 191 5.2.5 Microchannels with Two Phase Flow 193 5.3 Temperature Control in Chemical Microstructured Reactors 195 5.3.1 Axial Temperature Profiles in Microchannel Reactors 197 5.3.2 Parametric Sensitivity 201 5.3.3 Multi-injection Microstructured Reactors 212 5.4 Case Studies 221 5.4.1 Synthesis of 1,3-Dimethylimidazolium-Triflate 221 5.4.2 Nitration of Dialkyl-Substituted Thioureas 222 5.4.3 Reduction of Methyl Butyrate 223 5.4.4 Reactions with Grignard Reagent in Multi-injection Reactor 224 5.5 Summary 226 5.6 List of Symbols 226 References 228 6 Microstructured Reactors for Fluid–Solid Systems 231 6.1 Introduction 231 6.2 Microstructured Reactors for Fluid–Solid Reactions 232 6.3 Microstructured Reactors for Catalytic Gas-Phase Reactions 233 6.3.1 Randomly Micro Packed Beds 233 6.3.2 Structured Catalytic Micro-Beds 235 6.3.3 CatalyticWall Microstructured Reactors 238 6.4 Hydrodynamics in Fluid–Solid Microstructured Reactors 239 6.5 Mass Transfer in Catalytic Microstructured Reactors 243 6.5.1 Randomly Packed Bed Catalytic Microstructured Reactors 244 6.5.2 Catalytic Foam Microstructured Reactors 245 6.5.3 CatalyticWall Microstructured Reactors 246 6.5.4 Choice of Catalytic Microstructured Reactors 253 6.6 Case Studies 255 6.6.1 Catalytic Partial Oxidations 255 6.6.2 Selective (De)Hydrogenations 257 6.6.3 Catalytic Dehydration 259 6.6.4 Ethylene Oxide Synthesis 259 6.6.5 Steam Reforming 260 6.6.6 Fischer–Tropsch Synthesis 261 6.7 Summary 261 6.8 List of Symbols 262 References 262 7 Microstructured Reactors for Fluid–Fluid Reactions 267 7.1 Conventional Equipment for Fluid–Fluid Systems 267 7.2 Microstructured Devices for Fluid–Fluid Systems 268 7.2.1 Micromixers 269 7.2.2 Microchannels 271 7.2.3 Microstructured Falling Film Reactor for Gas–Liquid Reactions 272 7.3 Flow Patterns in Fluid–Fluid Systems 273 7.3.1 Gas–Liquid Flow Patterns 273 7.3.2 Liquid–Liquid Flow Patterns 280 7.4 Mass Transfer 284 7.4.1 Mass Transfer Models 285 7.4.2 Characterization of Mass Transfer in Fluid–Fluid Systems 286 7.4.3 Mass Transfer in Gas–Liquid Microstructured Devices 287 7.4.4 Mass Transfer in Liquid–Liquid Microstructured Devices 296 7.4.5 Comparison with Conventional Contactors 299 7.5 Pressure Drop in Fluid–Fluid Microstructured Channels 300 7.5.1 Pressure Drop in Gas–Liquid Flow 301 7.5.2 Pressure Drop in Liquid–Liquid Flow 304 7.6 Flow Separation in Liquid–Liquid Microstructured Reactors 307 7.6.1 Conventional Separators 308 7.6.2 Types of Microstructured Separators 308 7.6.3 Conventional Separator Adapted for Microstructured Devices 315 7.7 Fluid–Fluid Reactions in Microstructured Devices 315 7.7.1 Examples of Gas–Liquid Reactions 317 7.7.2 Examples of Liquid–Liquid Reactions 319 7.8 Summary 323 7.9 List of Symbols 324 References 325 8 Three-Phase Systems 331 8.1 Introduction 331 8.2 Gas–Liquid–Solid Systems 331 8.2.1 Conventional Gas–Liquid–Solid Reactors 331 8.2.2 Microstructured Gas–Liquid–Solid Reactors 333 8.3 Gas–Liquid–Liquid Systems 346 8.4 Summary 347 8.5 List of Symbols 347 References 348 Index 351

About the Author :
Dr. Madhvanand Kashid, Chemical Engineer, at Syngenta Crop Protection Monthey SA, Switzerland. He secured PhD in Chemical Engineering from Technical University of Dortmund, Germany, on "liguid-liquid slug flow capillary microreactors". Prior to joining Syngenta, he worked at Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. He had been extensively working on different aspects of microprocess engineering such as design and characterization of microstructured devices both by mathematical modelling and experimental validation, development of continuous process with industrial partners, and application of microdevices for educational purpose. He is the co-author of 25 scientific publications, reviews and book chapters. Prof. Dr. Albert Renken, Professor Emeritus, secured PhD and habilitation from University of Hannover and joined EPFL in 1977. He has been working on variety of topics related to chemical and polymer reaction engineering such as multiphase reactions, heterogeneous and enzymatic catalysis and micro reactor technology. He represents Switzerland in the Working Party on Chemical Reaction Engineering in the European Federation of Chemical Engineering. In 2007 he got the DECHEMA-Titan-Medal for his pioneering contributions to Chemical Reaction Engineering and Microreaction Technology. He is author or co-author of more than 450 scientific publications, 3 textbooks and co-author of the "Handbook of Micro Process Engineering". His actual research and teaching is focused on sustainable chemical production and process intensification. Prof. Dr. Lioubov Kiwi-Minsker, Head of the Group of Catalytic Reaction Engineering, GGRC, at Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland . Prof. Kiwi-Minsker received her PhD in 1982 in physical & colloidal chemistry from Moscow University, her habilitation in 1992 from the Novosibirsk University in Physical Chemistry and joined EPFL in 1994. Her teaching and research activities continue to be in the field of Heterogeneous Catalysis and Reactor technology, in particular, the reactors with structured catalytic beds and micro-reactors. She is the co-author of more than 200 scientific publications, patents and book chapters. She is currently a member of the Working party on "Chemical Reaction Engineering" and "Process Intensification" of the European Federation of Chemical Engineering (EFCE) and of the European Federation of Catalysis (EFCATS).