LAYERED DOUBLE HYDROXIDES: PRESENT AND FUTURE No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services LAYERED DOUBLE HYDROXIDES: PRESENT AND FUTURE VICENTE RIVES EDITOR Nova Science Publishers, Inc New York Copyright © 2001 by Nova Science Publishers, Inc All rights reserved No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services If legal or any other expert assistance is required, the services of a competent person should be sought FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Available upon request ISBN 978-1-61209-289-8 (eBook) Published by Nova Science Publishers, Inc New York CONTENTS Preface Part I: Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Part II: Chapter Chapter 10 Chapter 11 Chapter 12 Chapter 13 Index vii Synthesis, Structure and Characterisation Layered Double Hydroxides: Synthesis and Post-Synthesis Modification A de Roy, C Forano and J P Besse Crystal Structure and X-ray Identification of Layered Double Hydroxides V A Drits and A S Bookin Computer Modelling of Layered Double Hydroxides S P Newman, H C Greenwell, P V Coveney and W Jones Study of Layered Double Hydroxides by Thermal Methods Vicente Rives Infrared and Raman Spectroscopic Studies of Layered Double Hydroxides (LDHs) J T Kloprogge and R L Frost Solid-State NMR and EPR Studies of Hydrotalcities Jỗo Rocha Investigating Layered Double Hydroxides by Mưssbauer Spectroscopy Chr Bender Koch Surface Texture and Electron Mincroscopy Studies of Layered Double Hydroxides Vicente Rives Applications Layered Double Hydroxides in Water Decontamination María Ángeles Ulibarri and María del Carmen Hermosín Applications of Hydrotalcite-Type Anionic Clays (Layered Double Hydroxides) in Catalysis Francesco Basile and Angelo Vaccari Hydrogenation Catalysis by Mixed Oxides Prepared from LDHs A Monzón, E Romeo and A J Marchi Layered Double Hydroxides and their Intercalation Compounds in Photo-chemistry and in Medicinal Chemistry Umberto Costantino and Morena Nocchetti Environmental Chemistry of Iron(II)-Iron(III) LDHs (Green Rusts) Hans Christian Bruun Hansen 41 101 127 153 217 241 257 285 323 367 435 469 495 PREFACE Layered Double Hydroxides (LDH), hydrotalcite-like (HTl), hydrotalcite-type (HTt), anionic clays, , are the commonest names applied to a wide family of layered materials, despite none of these names fully corresponds to the actual situation Also known in some occasions as layered hydroxycarbonates, whichever the name given, these materials are not so extended in nature as the well known cationic clays, but are very easy to prepare and they are not generally expensive The first natural mineral belonging to this family of materials was discovered in Sweden in 1842, is known as hydrotalcite, and was given the general formula Mg6Al2(OH)16CO3·4H2O The first studies on the synthesis, stability, solubility and structure determination date back to 1930 and were mostly carried out by Feitknecht [1,2] Essentially, the structure can be described as a cadmium iodide-type layered hydroxide (e.g., Mg(OH)2, brucite) where a partial Mg2+/Al3+ substitution has taken place (thus the name “layered double hydroxide”), balancing of the electric charge being achieved by location of anions in the interlayer space (carbonate in most of the samples found in nature, so the name “layered hydroxycarbonates”), where they co-exist with water molecules Nowadays, solids with this structure, but containing more than two different (a divalent and a trivalent one) cations in the brucite-like layers, are also known What makes interesting to these materials is the fact that the nature of the layer cations can be changed among a wide possible selection (almost exclusively restricted by size and charge), and the nature of the interlayer anion can be also (almost freely) selected, among organic or inorganic, simple or complex anions, polyoxometalates, simple anionic coordination compounds, etc An additional feature that makes them similar to cationic clays is the fact that they can be also pillared, although doubts still exist in the literature about the thermal stability of the structures formed Also as cationic clays, the interlayer species can be rather easily exchanged, thus increasing their applications and opening new synthetic routes to prepare derivatives A unique property these solids exhibit, so making them different from cationic clays, is that after thermal decomposition under mild conditions, they are able to recover the layered structure, this property representing, again, a new synthetic route for analogues The possibilities all these properties open are surprisingly wide, and so the applications of these materials are widening almost every day The principal areas of interest include their use as catalysts and catalyst supports, adsorbents, anion scavengers, anion exchangers, polymer stabilizers, antacids, antipeptins and stabilizers The restricted interlayer space also represents a viii Vicente Rives sort of “nanoreactor” to perform chemical reactions in a constrained region, which may even modify well known properties of molecules (e.g., photochemical properties) In recent years several reviews have appeared on these LDHs, dealing with their general chemistry and properties [3], structure and pillared derivatives [4], analogues with interlayer organic anions [5] or with intercalated anionic coordination compounds or oxometalates [6] with different nuclearity degree With respect to their applications, Cavani, Trifirò and Vaccari published some years ago a very outstanding review [7] which has somewhat become a guide to learn about the catalytic properties of these solids and their derivatives A general comparison of cationic and anionic clays has been also reported [8] Also, special issues of one of the leading journals on clays have been devoted to different properties of these fascinating materials [9-11], and special sessions dealt to these materials in regional and world-wide international conferences Some of these reviews are rather recent, and so we have intended to avoid any sort of repetition or overlapping with their content, unless the scientific production in its particular area has provided a large number of papers, worthwhile to be reviewed and summarised Most of these studies have insisted or are dedicated to particular areas of interest of LDHs, i e., synthesis, structure, particular applications, etc However, the aim of this book is to present, in an unified form, an updating of current knowledge about LDHs, from different points of view, i e., paying attention to their synthesis, their properties and, finally, their applications We have chosen a rather “academic” way to cope with this subject, and we have tried to present the current knowledge about their structures and properties giving an account on the sort of information which may be known from application of specific, but well known and easily available, characterisation techniques Altogether, we hope this represents an updated and comprehensive description of LDHS from almost every point of view So, the first section comprises a total of eight chapters devoted to the synthesis and physicochemical characterisation of these materials Besse and his coworkers describe the structure of these compounds in relation to their synthesis, their preparative methods, and also providing a developing strategy for post synthesis modification Drits and Bookin perform a detailed study on the structural features of LDHs, namely, the isomorphous substitutions in the brucite-like layers, regularities in anion locations, order-disorder phenomena in the layers and in the interlayer, different LDH polytypes, stacking faults, etc Jones and his coworkers report computer simulations to probe the interlayer structure and dynamics of LDHs, due to the lack of detailed structural information available for these materials, especially when containing organic interlayer anions One of the outstanding properties of LDHs is their ability to recover their layered structure even after being calcined at moderate temperatures The effect of using different atmosphere conditions during decomposition, discriminating steps associated to dehydration, dehydroxylation, structure collapsing and formation of crystalline phases, as well as the effect of the nature of the interlayer anion on the final solids, are the aim of the following chapter Spectroscopic techniques have been also applied to characterise LDHs The main results reported in the literature on these solids, obtained by application of vibrational spectroscopic techniques (Infrared and Raman) are reviewed by Kloprogge and Frost, and Rocha reports on the application of solid state resonance techniques (mainly MAS-NMR, but also, although in a lesser extent, EPR) to characterize the solids in order to obtain a complete description of these systems, for different spectroscopically active nuclei studied so far Environmental Chemistry of Iron(II)-Iron(III) LDHs (Green Rusts) 485 Table Rate constants for reduction of nitrate by GRSO4 ([NO3-] = 14.3 mM, 25 oC) Interlayer ion Fe(II):Fe(III)a kobsb (x 10-5 s-1) SO42- 2.0 0.95 SO42- 3.0 4.70 GRCl → GRSO4 30 SO42- 2.0 32.8 Forched exchange 45 Cl- 3.0 30.8 30 CO32- 2.0 1.48 93 Ctrl ∼0 Comment Reference 51 Fe(II) in solution 51 a Initial Fe(II):Fe(III) ratio in GR b kobs relates to d[NH4+]/dt = kobs·r·[Fe(II)]GR where r is the stoichiometric ratio between NH4+ produced and + Fe(II)GR consumed ( (∆[ NH ] / ∆[Fe(II)] GR ) Figure Rates of nitrate reduction and nitrate accessibility to GR surface sites For GRSO4 and GRCO3 access is via external surface sites only whereas for GRCl (and forced nitrate exchange of GRSO4) internal surface sites can also be approached Nitrite is reduced about 100 times faster by GRs than nitrate Also the products are different At low nitrite concentrations GR is oxidized to magnetite whereas higher nitrite concentrations give rise to lepidocrocite.60 The main reduction products of nitrite is nitrous oxide and probably some dinitrogen as well; only little ammonium is produced.36,60 This is in strong contrast to the reaction with nitrate, where ammonium is the only product, and may indicate that either the reaction pathways of the nitrate and nitrite reductions are different, or that higher concentrations of intermediates in the nitrite reaction enables other reactions to take place E.g., in the nitrite reaction higher concentrations of nitroxyl ions may occur After protonation these can combine and form nitrous oxide: 2HNO ↔ N O + H2 O (Eqn.15) 486 Hans Christian Bruun Hansen Another possibility is the reaction between nitrite and ammonium with formation of dinitrogen.94 Thus, if ammonium is formed during the nitrite reduction it could react with nitrite with formation of dinitrogen: NH + + NO − ↔ N2 + 2H O (Eqn.16) More studies are needed to clarify the mechanisms of the nitrite and nitrate reductions An interesting aspect is how electrons are transferred from Fe(II) in the GR to the nitrogen; and how this is coupled to the formation of magnetite Magnetite may not form directly from the GR, but could form as a reaction product of Fe(III) hydroxy clusters with Fe(II) in solution The GR is not thought to be a good conductor of electricity and thus the reactive N-O species probably have to move from one site to another before complete reduction is achieved Selenium(IV/VI), Chromium(VI) and Other Inorganic Oxidants Myneni et al.95 demonstrated that Se(VI) either as selenate coprecipitated with GR or as selenate added to GRSO4 becomes reduced The oxidation product of the GR was primarily magnetite By use of XANES spectroscopy, the main Se products were found to be amorphous clusters of Se(0); with the coprecipitated samples Se(IV) was detected as intermediates In some experiments traces of Se(-II) was observed The process was further studied by Refait et al.,58 but in contrast to the previous work where Fe(II)GR was always in large excess, these authors used systems with Se(VI):Fe(II) ratios of 2, i.e., more Se(VI) was added than could be reduced even to Se(IV) Iron(II) hydroxide was oxidized by selenate to ferrihydrite and lepidocrocite; a GR with selenate in the interlayer and an Fe(II):Fe(III)-ratio varying between – 2.7 formed as an intermediate The Fe oxide products were found to contain Se(VI) and Se(IV) It seems likely that in this study Se(VI) was not reduced beyond Se(IV), as all reducing equivalents were consumed for the Se(VI) → Se(IV) reduction At lower Se(VI):Fe(II)GR-ratios Se-containing spinels are formed.77 This study also showed that selenite was reduced much faster than was selenate It can be concluded that GRs represent strong reductants of Se(IV) and Se(VI) and that product distributions will depend on the ratio of Se to Fe(II)GR Chromium(VI) is reduced to Cr(III) by GRs in a very fast reaction.47,96 The Cr(III) produced is incorporated into the ferrihydrite which form as an oxidation product of the GR Williams and Scherer47 have shown that the reduction of chromate by GRCO3 at pH follows first order kinetics with respect to Cr(VI) at higher GR surface area concentrations according to: d[Cr(VI)] = k • [Cr(VI) ]• AGR (Eqn.17) dt where k = 7.3 10-4 L m-2 s-1 and AGR is the surface area concentration of GRCO3 The rate of reaction is several magnitudes higher than the reaction between GRCO3 and nitrate mentioned above The authors also showed that chromate sorption to the GR interlayer is insignificant and thus only external surfaces of GRCO3 seems to be exposed to the oxidant In a study of chromate sorption to chloride, forms of non-oxidizable LDHs chromate was not found to exchange for interlayer chloride, indicating that GRCl may not neccesarily react faster with chromate than GRCO3 does.97 Environmental Chemistry of Iron(II)-Iron(III) LDHs (Green Rusts) 487 Preliminary work on GR oxidation by perchlorate shows that in the presence of 14 mM NaClO4 no oxidation can be observed for GRSO4 over a period of 100 h, whereas GRCl seems to oxidize slowly as determined from the net decrease in Fe(II)GR over time corresponding to a reaction rate of 2.3 10-9 ± 0.4 10-9 M s-1 This rate is about 25 times slower than when nitrate is used as an oxidant With arsenate no oxidation of GRSO4 is observed in the presence of 10 mM Na3AsO4 over a period of 100 h However, addition of arsenate causes solution Fe(II) concentrations to become very low, indicating that precipitation is taking place XRD of the solids show the presence of Fe(II)-arsenates (Fe3(AsO4)2 8H2O).77 This reaction sequence is similar to what has been observed in GRSO4 – phosphate systems.35 Organic Oxidants It is well known that hydrocarbons containg chloro- or nitrosubstituents can be reduced in the presence of Fe(II) sorbed to Fe(III) oxide surfaces suggesting that similar redox reactions may occur in the presence of GRs.98,99 Erbs et al.100 found that when an excess of tetrachlormethane was added to GRSO4 chloroform and minor amounts of hexachloroethane were produced; magnetite was formed as the oxidation product The rate of the reaction, which was first order with respect to Fe(II)GR was similar to the rate observed for nitrate reduction by GRSO4 O'Loughlin and Burris,101 also working with reduction of tetrachloromethane by GRSO4, found that addition of Cu(II) to the reaction suspensions (about 2.5 % of the Fe added) gave rise to a much faster reduction and that fully dehalogenated methane and C2 – C5 alkanes and alkenes were produced In another study where an excess of GRSO4 was reacted with different polyhalogenated ethanes, the corresponding ethenes were produced through reductive β-elimination.102 On longer reaction times (300 – 1200 h) ethene and ethane were produced Also in this study a marked catalyzing effect of Cu(II) was observed giving rise to 10 – 160 times higher reduction rates compared to systems with no Cu (Fig 10) The study also showed that bromosubstituted alkanes were more readily reduced than the chlorosubstituted counterparts, and that reduction rates increased with the number of halogens in the alkanes The catalyzing effect of Cu(II) is also known from reduction of nitrate by Fe(II).103 In a similar study Lee and Batchelor104 found that during 60 d GRSO4 reduced halogenated ethenes to less halogenated ethenes, including ethene In addition, acetylene and ethane were detected Magnetite formed as an oxidation product of GR It was also found that synthetic magnetite could act as a reductant of the chlorinated ethenes, suggesting that the magnetite formed in the GR suspensions may act as reductant when the reducing equivalents in the GRs have been consumed It can be concluded that GRs are able to reduce chlorinated alkanes and alkenes to their fully dehalogentated compounds, but that reaction rates are strongly dependent on the type of compound and the presence of catalysts such as Cu(II) in the GR Studies are needed to describe product distributions as function of reactant concentrations, time, pH and interlayer form of GR Ongoing investigations of GR reduction of nitroaromates (nitrobenzene, nitrophenole, nitrobenzoic acid) show that the reaction is fast and of similar nature as the reactions with Fe2+ sorbed to Fe(III) oxides.99 488 Hans Christian Bruun Hansen GREEN RUSTS IN NATURAL ENVIRONMENTS In the laboratory GRs are readily formed from mixed Fe(II)-Fe(III) systems and it is expected that formation of GRs should be a common process in natural anoxic, non-acid aqueous and terrestrial systems However, the high reactivity of the GRs including its oxidation by dioxygen during sampling, handling and analysis is probably the main reason that GRs have not very often been identified in mineralogical analyses Our current understanding of GR occurences in natural environments is therefore far from being complete The most unquestionable identifications of GRs originates from corrosion sheets and tubercles of iron Large crystals of GRCO3 have been identified in drinking water pipes by means of XRD and microscopic examination.12,105 In marsh sediments concretions formed by corrosion of iron fragments was found to contain well crystalline GRSO4.106 Sulphate-GR has also been observed on steel sheets in contact with seawater in harbours by means of Mössbauer spectroscopy.107 Mössbauer spectroscopy indicated that GRCO3 was present in anoxic ochre sludges.108 Iron(0) has gained popularity in remediation of groundwaters polluted with chlorinated solvents, nitroaromatics, nitrate, etc Oxidation of Fe(0) by such organic oxidant results in GR formation, at least as transient phases.22,23,46 Figure 10 Reduction of hexachloroethane to tetrachloroethene by GRSO4 in absence (•) and presence (♦) of 100 µM Cu2+ Approx starting concentrations were 3.5 mM GRSO4 and 20 µM hexachloroethane (Based on data from ref 102) Microbial oxidation of organic matter and concomitant reduction of Fe(III) to Fe(II) is a necessary prerequisite for the formation of GRs in most geoenvironments Fredrickson et al.109 observed precipitation of GR (probably GRCO3) in batch experiments with microbial reduction of ferrihydrite The GR was identified as hexagonal crystals showing a GR XRD pattern It is Environmental Chemistry of Iron(II)-Iron(III) LDHs (Green Rusts) 489 likely that microbially produced mineral reductants or surface adsorbed Fe(II) may represent better reductants of polyhalogenated compounds, nitroaromatics, azocompounds etc than the intercellular enzymatic reduction pathways.99,110,111 Green rust may represent one of such very reactive biominerals A hypothetical reduction sequence may be depicted as: CH2O Red pollut GR CO2 Ox pollut FeOOH (Eqn.18) The occurence and geochemistry of GR in anoxic soil layers have recently been reported by Trolard et al.,112 Génin et al.,14 and Bourrié et al.7 Mössbauer spectra of bluish iron-rich soil materials were shown to have similar quadrupole splittings and isomer shifts as synthetic GRs, although the Fe(II):Fe(III) ratios were lower than those observed for synthetic GRs Raman spectra of the soil samples supported the presence of GR Only small amounts of chloride, sulphate or carbonate could be identified in the samples suggesting the presence of other interlayer ions Hydroxide was postulated as the interlayer ion, and the formulas [Fe3(OH)6]+[OH]-, [Fe2(OH)4]+[OH]- and [Fe3(OH)6]2+[(OH)2]2- were proposed for the soil GRs The Fe2+ activities and pH of the soil waters ranged between 10-4.5 – 10-7 and 5.15 – 6.35, respectively There are at least two properties of the proposed soil GRs which not fit into the knowledge gained so far from studies of synthetic GRs and LDHs First, hydroxide is not very likely as the interlayer anion, as the anoxic more or less water saturated environments contains carbon dioxide which is expected to react immediately with the hydroxide in the interlayer to form bicarbonate or carbonate.113 Second, the pH and the Fe2+ activity of the soil waters are below the pH at which GRs normally are found to precipitate (> 6.5) In a study of Fe(II) mineral formation in an aquifer caused by an increased input of organic matter from the soil surface, Banwar114 found that the groundwater was undersaturated with respect to GRSO4 However, if the solubility products listed elsewhere had been used, the groundwater would be supersaturated with respect to GRSO4 and probably with GRCO3 as well Arden5 thought, that the 'ferroso ferric hydroxide' Fe3(OH)8 (= Fe3O4⋅4H2O = [Fe3(OH)6]2+[(OH)2]2-) was the actual compound controlling Fe2+ activities in Fe(II)- Fe(III) hydroxide suspensions However, by repeating Ardens experiments Hansen et al.36 demonstrated that GRSO4 and not Fe3(OH)8 was the actual compound precipitating Recently, based on mesurements of Fe2+ activities, pH and electrochemical potentials in reduced soil suspensions Brennan and Lindsay115 postulated that "amorphous magnetite" controlled Fe(II) solubility For the reaction: + − Fe 3O (amorphous) + 8H + 2e ↔ 3Fe 2+ + 4H2 O (Eqn.19) a log K of 40.7 was determined In reduced rice soils Ponnamperuma et al.6 determined a log K of 47.1 for Eq 19 but with Fe3O4 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170, 172, 173, 175, 176, 178, 179, 209, 210, 272, 276, 277, 281, 310, 311, 418 BHMBS, 178, 179 brucite layers, 26, 29, 31, 40, 41, 79, 87, 88, 210 brucite-like layers, 1, 3, 8, 12, 27, 39, 40, 42, 45, 46, 48, 49, 52, 55, 57, 58, 61, 62, 63, 64, 68, 70, 71, 74, 76, 77, 78, 79, 80, 81, 82, 84, 85, 86, 87, 88, 89, 115, 116, 119, 121, 122, 129, 133, 144, 151, 229, 233, 241, 243, 248, 347 C CAL, 369, 370, 371 calcination, 27, 29, 33, 116, 117, 120, 121, 122, 123, 124, 125, 126, 127, 129, 131, 132, 133, 174, 178, 179, 182, 230, 232, 233, 234, 238, 243, 247, 248, 253, 256, 258, 260, 268, 272, 275, 280, 286, 287, 288, 289, 291, 293, 296, 298, 299, 300, 301, 303, 304, 305, 307, 308, 312, 324, 325, 326, 327, 334, 335, 339, 344, 347, 348, 356, 358, 359, 361, 363, 364, 365, 366, 368, 370, 372, 374, 376, 377, 378 catalytic partial oxidation, 303 catalytic total oxidation, 304 cation distribution, 39, 49, 57, 61, 67, 68, 69, 82, 84, 86, 218, 219 Charge Equilibration Method, 97 CHT, 252, 253, 254, 255, 256, 260, 261, 262, 265, 267 cinnamaldehyde, 369, 370, 371, 373 Claisen-Schmidt condensation, 293 coalingite, 87, 150 coherent scattering domains, 48 coke concentration, 331, 332, 333, 334, 338, 342, 350, 352, 353 coke deposition, 327, 331, 332, 333, 335, 336, 338, 339, 343, 356, 363 coke formation, 152, 303, 305, 306, 324, 327, 331, 338, 339, 340, 342, 343, 344, 349, 350, 354, 355, 356, 357, 363 consistent valence forcefield, 112 coprecipitation, 8, 9, 10, 11, 14, 15, 16, 17, 18, 24, 26, 42, 88, 151, 152, 178, 222, 230, 261, 310, 323, 327, 328, 344, 359, 362, 364, 365, 366, 367, 368, 370, 372, 373, 375, 376, 377, 388 CP, 195, 202, 205 CPO, 303, 304, 305, 306 cross-polarisation, 193, 195, 205 crystallinity, 10, 14, 16, 88, 113, 120, 122, 149, 162, 231, 247, 265, 266, 269, 271, 272, 327, 328, 366, 388, 389, 416 CSDs, 48 CTO, 304 CVFF, 112 cyclodextrine, 277, 279 D DAS, 196 DBS, 271, 272, 279 496 Index DDS, 271, 276, 277, 278, 279 DEA, 360, 362 decarbonation, 120, 121, 123, 126, 184, 290, 293 decomposition, 14, 34, 82, 115, 119, 120, 122, 123, 124, 125, 126, 128, 129, 130, 133, 153, 193, 211, 216, 229, 243, 245, 290, 291, 296, 298, 300, 301, 302, 308, 309, 311, 312, 324, 335, 339, 344, 357, 360, 363, 372, 374, 375, 377, 378, 395 dehydroxylation, 22, 30, 33, 120, 121, 123, 124, 125, 126, 129, 130, 142, 183, 184, 197, 203, 311 delamination, 34, 35 dimethylformamide, 298 disordered cation distribution, 49, 66, 74, 84 DMF, 298 dodecylbenzenesulfonate, 271 dodecylsulfate, 271, 272, 273, 276, 278 Doppler effect, 215 DOR, 196 double rotation, 196 Dreiding forcefield, 97, 106, 108 DRIFT, 163, 165 DSC, 116, 117, 125, 207 DTG, 116, 117, 120, 123, 124, 125, 129, 133 dynamic angle spinning, 196 E EDTA, 126, 282, 398, 399 EEI, 361, 362 EGF, 404 electrochemistry, 34, 383 epidermal growth factor, 404 EPR, 193, 209, 210, 211 ESFF, 111 ethylene glycol, 55, 56, 231, 232 EXAFS spectroscopy, 298 F FCCU, 287, 296 Fe(II), 163, 164, 165, 166, 209, 216, 217, 219, 220, 222, 363, 413, 414, 415, 416, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431 Fe(III), 163, 164, 165, 166, 202, 209, 216, 217, 219, 220, 221, 222, 226, 227, 251, 267, 268, 274, 346, 363, 413, 416, 418, 419, 420, 421, 423, 426, 427, 428, 429, 430, 431 Fischer-Tropsch reactions, 148, 184 fluid catalytic cracking units, 287 Forcefield I, 97, 98, 107, 108 Forcefield II, 98, 107, 108 forcefields, 96, 97, 107 Fourier transform Infrared Emission Spectroscopy, 142 Fourier-transform infrared, 141 FTIR, 25, 26, 28, 141, 142, 150, 181, 183, 361, 362, 373 FTIR spectroscopy, 141, 142, 362 G GBL, 364, 365, 366, 367 GHSV values, 304, 306 glycerol saturation, 55 grafting, 22, 28, 29, 30, 119, 129, 133, 208, 233, 383 green rusts, 216, 217, 227, 413, 426 GRI, 414 GRII, 414 GRs, 216, 413, 414, 415, 416, 417, 418, 419, 420, 422, 423, 425, 426, 427, 428, 429, 430, 431 H HDSs, 88 hexacyanoferrate anions, 238, 241 HMW alcohols, 307 HT anionic clays, 285, 286, 287, 288, 289, 290, 293, 294, 295, 296, 298, 299, 300, 303, 306, 310, 311, 312, 314 HT compounds, 139, 253, 260, 285, 286, 287, 288, 289, 290, 291, 296, 300, 310, 311, 312, 314 HTs, 139, 268 hydrogenation, 152, 286, 287, 289, 290, 294, 307, 308, 323, 324, 325, 326, 327, 331, 332, 333, 335, 338, 339, 342, 344, 349, 350, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 376, 377, 378 hydrogenation catalysts, 286, 323, 326 hydrohonessite, 53, 76, 77, 78, 152, 160 hydrotalcite-like, 1, 10, 57, 78, 79, 90, 112, 115, 117, 118, 122, 128, 150, 153, 199, 200, 202, 208, 223, 229, 230, 234, 246, 251, 253, 256, 267, 272, 273, 274, 327, 328, 344, 346, 357, 359, 360, 364, 366 hydrotalcite-type, 149, 150, 160, 198, 313, 344, 345 hydroxyl double salts, 88 I IC, 384, 385 Index IES, 142, 183, 184, 186 induced hydrolysis, 15, 18, 416 infrared spectroscopy, 121, 140, 141, 142, 143, 153, 158, 178, 186, 238 interlamellar anions, 3, 8, interlamellar domains, 1, 2, 3, 5, 8, 19, 21, 25, 29, 197 interlamellar species, 3, 5, 7, 33 interlayer anions, 39, 57, 62, 64, 72, 74, 77, 78, 85, 88, 94, 97, 98, 99, 100, 110, 115, 116, 119, 124, 127, 130, 133, 144, 150, 174, 181, 216, 219, 226, 229, 241, 254, 290, 306, 324, 419 interlayer cation, 80, 85, 88, 94 interlayers, 25, 39, 40, 42, 44, 45, 46, 48, 49, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 64, 67, 72, 73, 74, 77, 78, 79, 80, 81, 82, 87, 88, 89, 90, 102, 103, 115, 176, 210, 238, 241, 246, 419, 426 Internal Conversion, 384 Intersystem Crossing, 384 IR spectroscopy, 89, 129, 230, 265, 361 ISC, 384, 385 IUPAC classification, 230, 241, 243 J 497 203, 204, 205, 206, 207, 208 Maxwell-Boltzmann distribution, 95 MEA, 359, 360, 361, 363 mean squared displacement, 98 Meerwein-Ponndorf-Verley reduction, 293, 294 mesityl oxide, 289 metallic cations, 1, 2, 3, 4, 8, 10, 12, 22, 28, 31, 33, 336, 343 methyl isobutyl carbinol, 289 methyl isobutyl ketone, 288, 289, 373 Mg3Al-LDH, 98, 103, 109, 110, 111, 112 MgAl-LDH, 107, 108, 277 MIBC, 289 MIBK, 288, 289, 373 microporosity, 24, 144, 164, 231, 233, 234, 238, 241, 245, 248 molybdates, 166, 167, 233 monoethylamine, 359, 360 Monte Carlo simulations, 94 MOPAC semi-empirical molecular orbital method, 97 motukoreaite, 53, 77, 78, 85 MPA, 361 MSDs, 99, 100, 101, 106, 107 MSO, 289 Jablonsky diagram, 384, 385 K Keggin anions, 12 L LAS, 418, 423, 424 layered double hydroxides, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 35, 94, 133, 139, 175, 193, 194, 197, 205, 206, 229, 244, 251, 257, 258, 276, 277, 285, 313, 323 LDH compounds, 10, 11, 12, 40, 50, 61, 419 LDH polytypes, 40, 64, 74, 80 LDH structures, 3, 44, 61, 71, 82, 125, 227 Lennard-Jones 6-12 potential, 96 linear alkyl-benzene-sulphonates, 424 long-range cation order, 43, 71, 84, 86 Lorentzian doublet, 218 M MA, 364, 365, 366, 367, 368 magic-angle spinning, 193, 194, 211 maleic anhydride, 364, 365 manasseite, 79 MAS, 193, 194, 195, 196, 197, 199, 200, 201, 202, N natural gas, 286, 302 Nernst equation, 419 Ni-Co-Zn-Al catalyst, 341, 342, 343 NIR, 141 NLO, 399 NMR, 25, 26, 89, 113, 120, 125, 150, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212 NMR spectrum, 195, 196, 197, 199, 201, 203, 204, 205, 206 NNN, 216, 217, 218 non linear optics, 383, 399 non-steroidal anti-inflammatory drugs, 406 NSAID, 405, 406 O Ocl, 275, 279 OHT, 275, 277, 278, 279, 280, 281, 282 100 supercell reflection, 70 organoclays, 269, 275, 279, 280 organohydrotalcites, 275, 279 oxidation, 33, 122, 123, 129, 130, 131, 133, 151, 152, 164, 165, 209, 210, 215, 216, 217, 219, 221, 222, 226, 227, 241, 294, 295, 298, 303, 498 Index 304, 305, 308, 311, 312, 330, 350, 375, 383, 395, 397, 413, 414, 415, 416, 417, 419, 420, 423, 424, 425, 426, 428, 429, 430 P peak intensity, 78 penthylamine, 361 pepsin, 403, 404 pesticides, 261, 270, 279 phenylphosphonic acid, 126, 180, 202, 204, 206 phosphates, 20, 33, 170, 255, 383, 407 phosphonates, 5, 178 photochemistry, 383, 384, 395, 409 PILCs, 273 pillared interlayer clays, 273 PO, 286 poly(styrene sulphonate), 125 polyoxometalates, 33, 130, 173, 174, 194, 207, 209, 233, 239 POM, 238, 243, 291, 310, 311, 312 powder X-ray diffraction, 11, 48, 93, 101, 109, 111, 113, 259 PPA, 180 propylene oxide, 286 PSS, 125, 180 PXRD, 13, 18, 22, 24, 93, 102, 116, 117, 119, 120, 126, 128, 350, 388, 392, 397, 399 R radiactive anions, 260 radial distribution function, 97, 98, 105 Raman spectroscopy, 140, 142, 167, 186 Raman spectrum, 148, 150, 155, 156, 158, 159, 160, 161, 163, 165, 166, 167 RDF, 98, 105, 106 redox reactions, 33, 423, 429 rehydration, 20, 118, 125, 204, 222, 256, 258, 290 Rietveld refinement, 50, 84, 93, 111 Rietveld technique, 50, 84 S SA, 365, 367, 405 SAED, 89 SAL, 369, 370 salicilate, 405 salt-oxide method, 15, 17 saturated alcohol, 369 saturated aldehyde, 369 Scaning Electron Microscopy, 244 scattering, 54, 62, 63, 64, 67, 68, 84, 85, 86, 106, 140, 142, 311 SCR, 287, 298, 302 second harmonic generation, 386, 399 selective catalytic reduction, 287, 298 SEM, 10, 35, 244, 331, 417 SHG, 386, 399 shigaite, 53, 77, 78, 85 short-range cation order, 86, 87 silicate layers, 26, 27, 30 silicates, 24, 28, 30, 31, 61, 89, 128, 172, 173, 191, 204, 208 SNG, 325 SOL, 369 specific surface area, 23, 116, 120, 229, 230, 233, 234, 238, 241, 243, 324, 327, 328, 335, 339, 340, 345, 346, 350, 374, 375, 377, 378, 383, 417 SSAs, 231, 238 stacking, 1, 4, 5, 6, 7, 8, 18, 25, 32, 40, 50, 57, 62, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 82, 84, 90, 246, 414 stacking faults, 40, 50, 71, 72, 73, 74, 75, 76, 80, 82, 84, 90, 246 stoichiometry, 15, 17, 68, 70, 71, 84, 86, 219, 431 synthetic natural gas, 325 T Taylor expansion, 95 TCP, 262, 264, 265 TEA, 361, 362 TEM, 35, 230, 241, 244, 360, 361, 375 temperature-programmed desorption, 360 temperature-programmed reduction, 131, 132, 342 TEOS, 172 terephthalate, 20, 94, 101, 102, 103, 104, 105, 106, 107, 167, 170, 176, 199, 234, 238, 239, 240, 241 tetraethylorthosilicate, 172, 204 tetrahydrofuran, 365 thermal decomposition, 39, 115, 116, 117, 119, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 197, 203, 204, 210, 243, 247, 285, 286, 290, 300, 310, 311, 314, 324, 328, 373, 374, 376, 377 THF, 295, 365, 366, 367 TNP, 176, 262, 263, 264, 265, 266, 267, 268 TOF, 362 TPD, 117, 360 TPR, 130, 131, 132, 133, 328, 335, 337, 343, 348, 354, 360, 362, 366, 370, 372 Transmission Electron Microscopy, 244 Index trinitrophenol, 176, 260, 265, 266, 274 U UAL, 369 unit cell parameters, 45, 49, 50, 76 unsaturated alcohol, 294, 368, 369, 378 unsaturated aldehyde, 294, 368, 369, 371, 378 UOL, 369 urea method, 14 V vanadates, 129, 166, 167, 170, 233 W water molecules, 2, 3, 5, 13, 19, 20, 22, 28, 33, 34, 39, 44, 45, 48, 53, 54, 62, 79, 82, 85, 88, 96, 97, 98, 100, 101, 102, 103, 104, 105, 106, 107, 109, 111, 112, 115, 117, 121, 129, 144, 149, 150, 151, 152, 155, 159, 162, 164, 174, 181, 197, 201, 499 206, 210, 229, 230, 234, 246, 251, 273, 285, 392 wermlandite, 53, 78, 85 X XAFS, 20 XAS, 87, 88, 130 X-ray absorption spectroscopy, 87, 88 X-ray diffraction, 8, 10, 16, 17, 34, 48, 99, 100, 112, 116, 118, 144, 155, 159, 167, 170, 175, 176, 179, 183, 185, 186, 230, 233, 243, 244, 253, 257, 265, 268, 270, 272, 329, 336, 340, 346, 348, 351, 388, 417, 418 X-ray Rietveld structure refinement, 4, XRD, 40, 48, 49, 50, 55, 57, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 84, 85, 86, 87, 88, 89, 90, 119, 153, 163, 185, 198, 203, 204, 205, 206, 207, 209, 210, 221, 226, 268, 285, 298, 300, 307, 327, 328, 335, 346, 350, 354, 359, 360, 362, 365, 366, 368, 370, 372, 375, 416, 418, 429, 430 ... Structure and Characterisation Layered Double Hydroxides: Synthesis and Post-Synthesis Modification A de Roy, C Forano and J P Besse Crystal Structure and X-ray Identification of Layered Double. .. Campanati, E Serwicka and A Vaccari (guest editors), Appl Clay Sci 18 (2001) pp 1-110 PART I: SYNTHESIS, STRUCTURE AND CHARACTERISATION In: Layered Double Hydroxides: Present and Future Editor: Vicente... Infrared and Raman Spectroscopic Studies of Layered Double Hydroxides (LDHs) J T Kloprogge and R L Frost Solid-State NMR and EPR Studies of Hydrotalcities Jỗo Rocha Investigating Layered Double