Layered double hydroxides preparation

One problem associated with the peroxotungstate-catalyzed epoxidation system described above is the separation of the catalyst after the completed reaction. To overcome this obstacle, efforts to prepare heterogeneous tungstate catalysts have been conducted. De Vos and coworkers employed W catalysts derived from sodium tungstate and layered double hydroxides (LDH - coprecipitated MgCU, AICI3, and NaOH) for the epoxidation of simple olefins and allyl alcohols with... 

Zinc hydroxy double salts are layered materials similar to layered double hydroxides which show intercrystalline reactivity and incorporate organic compounds between layers.337 Hydroxy double salts of high crystallinity can be obtained by reacting ZnO with organic metal salts in water. Zinc oxide crystals could then be prepared by thermal treatment of hydroxy zinc acetate.338... 

Anionic complexes can easily be prepared by the sulfonation of the aromatic rings in the complexes. Sulfonated cobalt phthalocyanine intercalated in a layered double hydroxide host was a stable catalyst for the oxidation of thiols162,163 and phenol derivatives.164 It was concluded that the complex has been intercalated with the plane of the phthalocyanine ring perpendicular to the sheet of the host (edge-on orientation) (Fig. 7.2). 

Evans, D.G. and Duan X. (2006) Preparation of layered double hydroxides and their application as additives, polymers, as precursors to magnetic materials and in biology and... 

Keywords Layered double hydroxide Hydrotalcite Preparation LDH... 

Abstract This chapter is intended to provide a state-of-the-art review of nanocomposite materials prepared by the assembly of layered double hydroxides (LDH) and polymers, including their synthesis and characterization, and point out their potential applications. 

Cr3+ can also be integrated into the structures of layered double hydroxides. A mixed oxide, prepared by calcination of ZnCr-LDH-CCh, was used in combination with t-BuOOH for the ketonization of alkyl and of benzyl pyridines and for the oxidation of benzyl amines to give Schiff bases (67,68). In contrast to MgAl-LDHs, for example, these materials display hardly any basicity so that base-catalyzed side reactions such as aldol condensations are avoided. 

Layered double hydroxides (LDHs), also known as anionic clays and hydro-talcite-like materials, are layered solids that are of increasing interest [5-8]. They consist of stacks of positively charged hydroxide layers with interlayer, charge-balancing, anions and are available as naturally occurring minerals [9] and as synthetic materials. They were prepared in the laboratory in 1942 when Feitknecht reacted dilute aqueous metal salt solutions with base [10, 11], although the first detailed structural analyses of LDHs were not performed until the late 1960s by Allmann and Taylor and their co-workers [12-15]. 

Crepaldi, E. L., Pava, P. C., Valim, J. B. and Jones, W. (2000). Synthesis and thermal behaviour of copper-chromium-carbonate layered double hydroxides, in preparation. 

Yichi, M. F. and Alves, O. L. (1997). Preparation of Cd/Al layered double hydroxides and their intercalation reactions with phosphonic acids. J. Mater Chem. 7, 1631. 

Franklin, K. R., Lee, E. and Nunn, C. C. (1995). Preparation and characterization of layered double hydroxides containing monovalent and divalent ions derived from 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid. J. Mater. Chem. 5, 565. 

Park, I. Y., Kuroda, K. and Kato, C. (1989). Preparation of a layered double hydroxide-porphyrin intercalation compound. Chem. Lett., 2057. 

Fudala, A., Palinko, I. and Kiricsi, I. (1999). Preparation and characterization of hybrid organic-inorganic composite materials using the amphoteric property of amino acids amino acid intercalated layered double hydroxide and montmorillonite. Inorg. Chem. 38, 4653. 

Complex precipitates, such as layered double hydroxides, are frequently prepared as precursors of oxide catalysts. Hydrotalcite is a hydrated hydroxy-carbonate mineral with the formula Mg,sAl2(0H)i6C03-4H20. It represents the better known and most popular member of a family of layered double metal hydroxide com-... 

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