Page 14 - Adsorbents fundamentals and applications

PREFACE

Since the invention of synthetic zeolites in 1959, innovations in sorbent devel-
opment and adsorption process cycles have made adsorption a key separations
tool in the chemical, petrochemical and pharmaceutical industries. In all future
energy and environmental technologies, adsorption will likely play either a key
or a limiting role. Some examples are hydrogen storage and CO removal (from
hydrogen, to <1 ppm) for fuel cell technology, desulfurization of transportation
fuels, and technologies for meeting higher standards on air and water pollutants.
These needs cannot be fulfilled by current commercial sorbents.
The past two decades have shown an explosion in the development of new
nanoporous materials: mesoporous molecular sieves, zeolites, pillared clays, sol-
gel-derived metal oxides, and new carbon materials (carbon molecular sieves,
super-activated carbon, activated carbon fibers, carbon nanotubes, and graphite
nanofibers). The adsorption properties for most of these new materials remain
largely unexplored.
This book provides a single and comprehensive source of knowledge for all
commercial and new sorbent materials. It presents the fundamental principles
for their syntheses and their adsorption properties as well as their present and
potential applications for separation and purification.
Chapter 2 provides a simple formula for calculating the basic forces or poten-
tials for adsorption. Thus, one can compare the adsorption potentials of two
different molecules on the same site, or that of the same molecule on two dif-
ferent sites. The calculation of pore size distribution from a single adsorption
isotherm is shown in Chapter 4. The effects of pore size and shape on adsorp-
tion are discussed in both Chapters 2 and 4. Chapter 3 aims to provide rules
for sorbent selection. Sorbent selection is a complex problem because it also
depends on the adsorption cycle and the form of sorbent (e.g., granules, powder,
or monolith) that are to be used. The attributes sought in a sorbent are capacity,
selectivity, regenerability, kinetics, and cost. Hence, Chapter 3 also includes a
summary of equilibrium isotherms, diffusion steps, and cyclic processes. Simple
sorbent selection criteria are also presented.
The fundamental principles for syntheses/preparation, adsorption properties, and
applications of the commercially available sorbents are covered in Chapters 5–7.
Mesoporous molecular sieves are discussed, along with zeolites, in Chapter 7.

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