Gas adsorption equilibria : experimental methods and adsorptive isotherms

CONTENTS Preface xi Acknowledgements xiii Introduction 1. 2. 3. 4. Introduction 1 1 Gas Adsorption Processes in Separation Technology 2 Experimental Methods 6 What Is Not Considered 10 References 11 Chapter 1: BASIC CONCEPTS 17 1. 2. 3. 4. Introduction 17 Adsorption Phenomena 18 Sorbent Materials 25 Characterization of Porous Solids 31 4.1 4.2 4.3 Mercury Intrusion Porosimetry 32 Helium Measurements 34 Gas Adsorption 43 5. Mass and Volume of Adsorbed Phases 52 5.1 Models for the Void Volume of a Sorbent Material and the Volume of a Sorbate 56 5.2 Outline of Calorimetric-Dielectric Measurements of Absolute Masses of Adsorbates 66 6. List of Symbols 70 References 72 Chapter 2: VOLUMETRY / MANOMETRY 79 1. 2. Introduction 79 Volumetric Measurement of Pure Gas Adsorption Equilibria (N = 1) 81 2.1 2.2 2.3 2.4 Experimental 81 Theory 82 Uncertainties or Errors of Measurements 85 Example 87 3. 4. Thermovolumetry 88 Volumetric Measurement of Multicomponent Gas Adsorption Equilibria (N > 1) 91 vi 4.1 4.2 4.3 4.4 Experimental 91 92 94 95 Theory Uncertainties or Errors of Measurements Example 5. Volumetric – Calorimetric Measurements The Sensor Gas Calorimeter (SGC) 97 5.1 99 5.2 5.3 Experimental Outline of Theory and Calibration 103 106 109 109 109 111 114 Example 6. Pros and Cons of Volumetry / Manometry 6.1 6.2 Advantages Disadvantages 7. List of Symbols References Chapter 3: GRAVIMETRY 117 117 120 120 120 122 127 129 129 131 134 135 153 1. 2. Introduction Gravimetric Measurements of Pure Gas Adsorption Equilibria (N = 1) 2.1 Two Beam Balances 2.1.1 2.1.2 2.1.3 Experimental Theory Uncertainties or Errors of Measurements 2.2 Single Beam Balances 2.2.1 2.2.2 2.2.3 Experimental Theory Uncertainties or Errors of Measurements 2.3 Examples 3. 4. Thermogravimetry Gravimetric Measurement of Multicomponent Gas Adsorption Equilibria (N > 1) 157 157 158 161 162 167 167 170 171 175 4.1 4.2 4.3 4.4 Experimental Theory Uncertainties or Errors of Measurement Examples 5. Pros and Cons of Gravimetry 5.1 5.2 Advantages Disadvantages 6. List of Symbols and Abbreviations References Contents vii Chapter 4: VOLUMETRIC – GRAVIMETRIC MEASUREMENTS 181 1. 2. Introduction 181 Volumetric – Gravimetric Measurements of Binary Coadsorption Equilibria 182 182 185 191 193 2.1 2.2 2.3 2.4 Experimental Theory Uncertainties or Errors of Measurement Examples 3. Densimetric – Gravimetric Measurements of Binary Coadsorption Equilibria 205 205 208 213 214 3.1 3.2 3.3 3.4 3.5 Experimental Theory Uncertainties or Errors of Measurement Example Densimetric-Volumetric Measurements of Binary Coadsorption Equilibria 218 3.6 Volumetric-Densimetric Measurements of Wall Adsorption 222 4. Pros and Cons of Volumetric-Gravimetric Measurements of Binary Coadsorption Equilibria 225 225 226 4.1 4.2 4.3 Advantages Disadvantages Comparison of Densimetric-Gravimetric and Densimetric- Volumetric Binary Coadsorption Measurements 227 229 232 5. List of Symbols and Abbreviations References Chapter 5: OSCILLOMETRY 235 1. 235 2. Introduction Measurement of Pure Gas Adsorption Equilibria (N = 1) by Slow Oscillations of a Rotational Pendulum 237 237 240 241 243 251 252 2.1 2.2 Experimental Outline of Theory 2.2.1 2.2.2 The Motion of the Pendulum in Vacuum The Motion of the Pendulum in Sorptive Gas 2.3 2.4 Uncertainties or Errors of Measurement Examples 3. Oszillometric - Gravimetric Measurements of Gas Absorption in Swelling Materials 256 256 257 260 263 3.1 3.2 3.3 3.4 Introductory Remarks Experimental Theory Example viii 4. Oscillometric – Manometric Measurements of Gas Absorption in Swelling Materials 265 265 266 271 272 275 275 275 277 282 4.1 4.2 4.3 4.4 Introductory Remarks Experimental Theory Example 5. Pros and Cons of Oscillometry 5.1 5.2 Advantages Disadvantages 6. List of Symbols References Chapter 6: IMPEDANCE SPECTROSCOPY 287 287 289 289 299 299 302 1. 2. Introduction Dielectric Measurements of Gas Adsorption Systems 2.1 2.2 Experimental Theory 2.2.1 2.2.2 2.2.3 Basic Concepts Polarization of Dielectrics Models for the Complex Permittivity of Dielectric Sorbent-Sorbate Systems 306 2.3 Uncertainties of Dielectric Measurements of Adsorption Systems 316 2.4 Examples 318 3. Dielectric-Manometric and Dielectric-Gravimetric Measurements of Pure Gas Adsorption Equilibria 332 332 336 342 349 349 350 351 353 3.1 3.2 3.3 Experimental Examples Impedance Measurements in Adsorption Reactors 4. Pros and Cons of Impedance Spectroscopy 4.1 4.2 Advantages Disadvantages 5. List of Symbols References Chapter 7: ADSORPTION ISOTHERMS 359 359 363 363 363 372 377 1. 2. Introduction Simple Molecular Isotherms 2.1 Langmuir Adsorption Isotherm 2.1.1 2.1.2 2.1.3 Classical Form Heterogeneous Surfaces Admolecules with Interactions Contents ix 3. Empirical Isotherms 382 382 384 386 387 391 393 394 394 395 402 404 407 3.1 3.2 3.3 3.4 3.5 3.6 Freundlich-Ostwald-Boedecker (FOB) Virial Expansions Toth’s Isotherm Brunauer-Emmett-Teller Isotherm (BET) Dubinin-Polanyi Theory Integral Equation Approach 4. Thermodynamic Isotherms 4.1 4.2 Gibbs’s Approach Internal Variable Approach 5. 6. Conclusions List of Symbols References Subject Index 415 Author Index 421