[membrane science and technology] inorganic membranes: synthesis, characterization and applications...

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PREFACE This book has its origin in the XXII Summer School of the European Membrane Society that took place in Jaca (Spain) in 2005, devoted to ‘‘Inorganic Membranes: Preparation, Characterization and Applications.’’ Experts on inorganic membranes from both industry and the academic world attending the course all agreed that there was a need for a new general book updating the literature in the field. Books on Inorganic Membranes A review of books devoted to inorganic membranes starts with those published by Burggraaf in 1992 and by Burggraaf and Cot in 1996, ‘‘Inorganic Membranes’’ and ‘‘Fundamentals of Inorganic Membrane Science and Technology,’’ respectively. These two books described the basis of ceramic membranes. Also, in 1996, Hsieh’s book ‘‘Inorganic Membranes for Separation and Reaction’’ discussed the possibi- lities of inorganic membranes in what was then the emerging field of inorganic membrane reactors. Subsequent major advances were in the microporous mem- brane field, and ‘‘Recent Advances in Gas Separation by Microporous Ceramic Membranes’’ edited by Kanellopoulus appeared in 2000. There is no recent general book devoted to inorganic membranes with an overview including all such membranes and their main applications, although some aspects have been discussed in recent books such as ‘‘Catalytic Membranes and Catalytic Membrane Reactors’’ by Sanchez and Tsotsis (2002), ‘‘Nonporous Inorganic Membranes: For Chemical Processing’’ by Sammells and Mundschau (2006), ‘‘Membrane Technology: In the Chemical Industry’’ by Nunes and Peinemann (2001 and 2006), and ‘‘Ceramic Membranes for Separation and Reaction’’ by Li (2007). Aim of the Book The main purpose of this book is to gather together in one work the main advances in the field of inorganic membranes, both porous and dense, provided by leading experts in the field. In the case of porous membranes, these advances are related to the synthesis of microporous materials such as silica, carbon, and zeolites in the form of nondefective thin layers and the production of hollow fiber membranes. In addition, the book discusses the increasingly relevant hybrid membranes, which combine the stability of inorganic membranes and the processability of polymers. Attention is also devoted to dense inorganic membranes divided into the hydrogen-selective palladium xiii

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Page 1: [Membrane Science and Technology] Inorganic Membranes: Synthesis, Characterization and Applications Volume 13 || Preface

PREFACE

This book has its origin in the XXII Summer School of the EuropeanMembrane Society that took place in Jaca (Spain) in 2005, devoted to ‘‘InorganicMembranes: Preparation, Characterization and Applications.’’ Experts on inorganicmembranes from both industry and the academic world attending the course allagreed that there was a need for a new general book updating the literature inthe field.

Books on Inorganic Membranes

A review of books devoted to inorganic membranes starts with those published byBurggraaf in 1992 and by Burggraaf and Cot in 1996, ‘‘Inorganic Membranes’’ and‘‘Fundamentals of Inorganic Membrane Science and Technology,’’ respectively.These two books described the basis of ceramic membranes. Also, in 1996, Hsieh’sbook ‘‘Inorganic Membranes for Separation and Reaction’’ discussed the possibi-lities of inorganic membranes in what was then the emerging field of inorganicmembrane reactors. Subsequent major advances were in the microporous mem-brane field, and ‘‘Recent Advances in Gas Separation by Microporous CeramicMembranes’’ edited by Kanellopoulus appeared in 2000. There is no recent generalbook devoted to inorganic membranes with an overview including all suchmembranes and their main applications, although some aspects have been discussedin recent books such as ‘‘Catalytic Membranes and Catalytic Membrane Reactors’’by Sanchez and Tsotsis (2002), ‘‘Nonporous Inorganic Membranes: For ChemicalProcessing’’ by Sammells and Mundschau (2006), ‘‘Membrane Technology: In theChemical Industry’’ by Nunes and Peinemann (2001 and 2006), and ‘‘CeramicMembranes for Separation and Reaction’’ by Li (2007).

Aim of the Book

The main purpose of this book is to gather together in one work the main advancesin the field of inorganic membranes, both porous and dense, provided by leadingexperts in the field. In the case of porous membranes, these advances are related tothe synthesis of microporous materials such as silica, carbon, and zeolites in the formof nondefective thin layers and the production of hollow fibermembranes. In addition,the book discusses the increasingly relevant hybrid membranes, which combine thestability of inorganic membranes and the processability of polymers. Attention is alsodevoted to dense inorganic membranes divided into the hydrogen-selective palladium

xiii

Page 2: [Membrane Science and Technology] Inorganic Membranes: Synthesis, Characterization and Applications Volume 13 || Preface

xiv Preface

membranes and the dense ceramic mixed conducting membranes, all experiencingconstantly improved fluxes and new synthesis methods for obtaining thinner layers andhigher temperature stability. The applications of all these membranes are consideredthroughout the book.

Book Organization

The book is divided into two parts, the first dealing with porous inorganic membranesand the secondwith dense inorganic membranes. This division is very important giventhe very different permeation mechanisms of these two types of membrane and theconsequent differences in selectivity and flux. In general, fluxes are higher in the case ofporous membranes while higher selectivity can be achieved using dense membranes.

Porous membranes

The part of the book devoted to porous inorganic membranes consists of sevenchapters that evaluate the ‘‘state of the art’’ and recent advances in this field. The firstchapter serves as an introduction to these membranes in terms of their structure andprovides a general overview of the stability of ceramic membranes, the principaladvantage of inorganic membranes. Porous ceramic membranes are mainly appliedin harsh circumstances in terms of temperature or when aggressive chemicals such assolvents or highly acidic or caustic solutions are used. In these circumstances,cheaper polymer membranes have limited stability. They can generally only standtemperatures below�100 �C, and they swell or partly dissolve in many solvents andin strong acids or bases. Ceramics, on the other hand, are generally known for theirvery high chemical and thermal stability, although this stability can be limited, duemainly to sintering processes, corrosion, and hydrothermal stability.

Chapters 2–5 describe the inorganic materials processed as planar, tubular, or evenhollow fiber membranes. Chapter 2 deals with microporous silica membranes. Thetwo main routes for the synthesis of these membranes, sol–gel techniques andchemical vapor deposition (CVD), are explained in detail. The main applicationsand goals achieved with these membranes as well as the transport mechanisms arerevised. The preparation of inorganic membranes as hollow fibers provides a highsurface to volume ratio and a good opportunity for these materials to be implementedin the industry. Chapter 3 describes the preparation of carbon and aluminamembranes as hollow fibers.

The possibility of combining polymers and inorganic components in one materialhas emerged in recent decades with the birth of soft inorganic chemistry and theintroduction of the concept of ‘‘hybrid organic–inorganic’’ materials, which allowstailoring innovative materials with organic and inorganic phases coexisting on a nano-scale and with multifunctionalization. These hybrid organic–inorganic membranescould be applied, for example, in the field of fuel cells. Chapter 4 describes thepreparation of these composites either with nonpermeable or permeable fillers.

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Preface xv

Zeolite membranes are presented in Chapter 5. This chapter tackles the peculia-rities of these solids, with more than a hundred different structures, widely used asion-exchangers and catalysts. There have been many significant advances from thefirst zeolite polycrystalline layer prepared in 1987 to achieving complete control ofthe zeolite layer growth and orientation, all of which are reviewed in this chapter.The different zeolite synthesis methods and other important aspects such as supportselection, calcinations, and posttreatments are also described in this chapter. The lastpart of the chapter is dedicated to the characterization and some of the mainapplications of zeolite membranes not only in the field of separation but also asmembrane reactors, microreactors, and sensors.

Porous inorganic membrane applications are described in Chapters 6 and 7 .Chapter 6 considers applications in pressure-driven membrane processes, that is,microfiltration, ultrafiltration, and nanofiltration, using mainly macro- and meso-porous membranes. These processes are applicable in various industries such as thechemical industry, food and beverage processing, and wastewater treatment.Chapter 7 deals with applications of microporous inorganic membranes in perva-poration and gas separation. Moreover, there is a section in this chapter devoted totransport modeling in microporous membranes.

Dense membranes

The last three chapters are devoted to dense membranes and their applications.Palladium is a material that for many years has been proposed for use in hydrogenseparation, including application in membrane reactors. Recent advances leading tothinner palladium films with higher flux and lower cost, as described in Chapter 8,are paving the way toward many applications. Since membrane reactors are a keyapplication of this material, the design of the reactor must be considered. Chapter 9presents a wide-ranging reviewof the different possible approaches to themathematicalmodeling of such membrane reactors.

Finally, the last chapter (i.e., Chapter 10) reviews current knowledge of denseceramic membranes, which hold the promise of solving one of the major problemsof humankind: sustainable energy. This kind of membrane offers high selectivity tohydrogen or oxygen which is transported as charged species in the membranematrix. The main application is in solid oxide fuel cells, but there may also bepotential uses in the generation of gases or the separation of high purity oxygen orhydrogen from mixed streams.

In conclusion, this book provides researchers and users in the field of inorganicmembranes with an updated review of the state of the art and points to future needsand prospective applications. As such, we hope that it will be useful both forresearchers starting out in the field and for those who, having contributed to recentdevelopments in inorganic membranes, wish to have a reference book where currentknowledge is conveniently assembled.

REYES MALLADA

MIGUEL MENENDEZ