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Review of “Oxide-based Systems at the Crossroads of Chemistry” Edited by A. Gamba, C. Colella and S. Coluccia Elsevier, Amsterdam; ISBN:0-444-50632-2 This book consists of forty-one papers selected from the Second International Workshop on Oxide Based Systems. Its scope encompasses oxides and related oxide based materials such as zeolites. The papers are arranged alphabetically according to the names of the first author, although it seems that there could be more informative ways of grouping them. In general, the papers can be grouped into the following categories: applications; overviews; preparation methods; and physical/chemical/ computational characterization studies. The widely different approaches used in the study of oxides in this collection indeed reflect its title. A significant portion of the book is devoted to more “traditional” catalysis studies that emphasize the application aspect of oxide catalysts. The investigators searched for more active and more stable materials for a particular application. For example, they evaluated the performances of specific materials such as heteropolyacid-modified polymer silica membranes for direct methanol fuel cells (V. Antonuccit et al.); CeO2-ZrO2/Al 2O3 for use in three-way catalyst applications (R. Di Monte et. al.), and Italian phillipsite and chabzites as cation exchangers for wastewater treatments (Colella et al.). Many of these studies strived to establish a structure-reactivity relationship by using a combination of spectroscopic characterization techniques such as IR, NMR, XRD, EPR and diffuse reflectance spectroscopy. Most of these papers are well written and will appeal to readers working specifically in that field. An interesting application overview is on electroceramics in solid oxide fuel technology by A. J. McEvoy A recent emphasis in applied catalysis is to increase the efficiency in catalyst preparation and screening, and examples are given in this book. Katovic et al. demonstrated the factorial experimental design for zeolite synthesis. Bearns et al. used combinatorial methodology to search for better multimetal oxide catalysts for the oxidative dehydrogenation of propane. The selection of primary redox compounds in this library was based on simplifying the assumption that a medium oxygen-metal binding energy is required to ascertain the participation of lattice oxygen in the oxidative dehydrogenation of propane. Using spectroscopic techniques and oxygen adsorption kinetics they were able to conclude that a good propane oxidative dehydrogenation catalyst contains an optimal concentration of the active VOx species dispersed on the support surface. This study demonstrates how
rapidly this methodology can zero in on some desirable compositions for a particular reaction. Yet, despite accompanying spectroscopic and kinetic characterizations of the catalysts, only a general conclusion regarding the desired characteristics of a good oxidative dehydrogenation catalyst could be arrived at. Clearly, additional approaches have to be explored for catalyst design, and indeed investigations into the limitation and potential of some of these approaches are reported in this book. The approaches explored by some investigators were to use state-of–the-art instrumentation to access knowledge not easily obtained by more conventional techniques. The book begins with an overview by J. M. Thomas on this topic. The techniques discussed are HRTEM, neutron diffraction and XFAS in the characterization of oxides. Examples given of the capability of HRTEM include a study of La 2CuO 4, where the surface and bulk compositions differ significantly, and zeolite-L, where the surface structure is well represented by the structure of the bulk. The potential of neutron diffraction with isotropic substitution (NDIS) for in situ characterization of reactant-active site interaction is illustrated with a study of cyclotrimerization of benzene over a Ni-Y zeolite. The power of the coupled XFAS-XRD technique, with respect to interrogation of the nature of the active site and the structural integrity of the mesoporous material under in situ conditions, is discussed with respect to Ti grafted onto MCM41. Another article on the use of in situ EXAF is by Dal Santo et al. They studied the hydrodechlorination of carbon tetrachloride with organometallics-based platinum and palladium catalysts on MgO. EXAF spectroscopy gave useful information about the morphology and the state of the metal particles as well as the co-ordination of chlorine. An overview article by Alberti et al. compares the location of extraframework cations and Brønsted acid sites in different dehydrated zeolites. The authors proposed that bond strength information can be useful to locate Brønsted acid sites even if neutron diffraction data are not available. To validate their claim, they compiled an extensive data base of proton and cation sitings in different zeolites from literature results and compared them with their calculations. Many of the literature data were obtained from sophisticated spectroscopic techniques, and therefore the power of coupling spectroscopy with computation is well illustrated in this article. Other articles of this nature include that of Cavalleri et al. who used a combined IR 131 Volume 6, no. 3, 2002
Book reveiw
spectroscopic and quantum chemical study of dissociative adsorption of H 2 on defect sites of MgO. The assignments of the IR bands were aided by ab initio HF calculations. Stretching frequencies predicted by calculations, but not present in the IR spectra, can be used to exclude the stabilization of H on certain Mg and O sites. One approach that should play a role in accelerating the progress of catalysis is the novel synthesis methodology. There are very few synthesis studies in this collection. Rizzo et al. attempted to control the textural properties by systematically varying the synthesis parameters such as the solvent SiO2/Al 2O3 ratio etc. Unfortunately, the only structural characterization of these materials are N2 adsorption-desorption isotherms. Isomorphous substitution of Al by other cations were also explored. Nigro et al. attempted to incorporate Co into the MFI structure and concluded that part of Co was incorporated, but he was unable to quantify the tetrahedral Co(II). Giordano
et al. described the synthesis of Fe-Al-BEA and Fe-AlMOR and Al-Fe-MFI. With the explosion of work in the use of organic templates to order inorganic materials synthesis over a wide “length scale” (Zhao et al., Science 279(1998)548, nanocomposites that incorporate organic in the channel walls of inorganic (Ozin, G. Chem. Eur. J., 6(2000)2505), and hierarchical zeolite materials with ordered nano-, meso-, and macroporosity (Rhodes et al., Chem. Mater. 12(2000)2832), it is surprising that there are so few novel syntheses studied in this collection. Mayfair Chu Kung Research Associate Professor Chemical Engineering Department Northwestern University Evanston, Il 60208 phone (847) 491-7620 e-mail
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