chapter  9
46 Pages

9Sorption Processes

ByF. Rodríguez-Reinoso, A. Sepúlveda-Escribano, J. Silvestre-Albero

When an atom or molecule hits a solid surface, several phenomena can appear.Itmayreboundwithitsstartingenergy,oritmayberetainedon thesurfaceforamoreorlesslongtime.Inthiscase,adsorptionisproduced, andthetimeduringwhichtheadsorbedspeciesisretainedonthesurface isrelatedtothestrengthoftheinteractionwiththesurface.Theadsorbed atoms or molecules may stay „xed on a surface site, they may diffuse across

CONTENTS

9.1Introduction ................................................................................................ 307 9.2 Fundamentals of Adsorption ...................................................................308 9.3 Adsorption as a Tool for Characterization of Porous Solids ............... 312

9.3.1 Determination of Adsorption Isotherms.................................... 312 9.3.2Analysis of Adsorption Isotherms .............................................. 314

9.3.2.1Determination of Surface Area ..................................... 315 9.3.2.2 Microporosity .................................................................. 320 9.3.2.3 Mesoporosity ................................................................... 325 9.3.2.4 Macroporosity.................................................................. 329 9.3.2.5Problems Commonly Found in Characterization

by Adsorption ..................................................................330 9.4 Immersion Calorimetry ............................................................................ 341 9.5 Current Challenges in Adsorption Processes ........................................343