Intercalation of n-alkylamines in the vapor phase into vanadium pentoxide xerogel dispersed into silica matrix
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EE9.32.1
Intercalation of n-alkylamines in the vapor phase into vanadium pentoxide xerogel dispersed into silica matrix
Mariza A. Figueiredo and Herenilton P. Oliveira Depto. de Química, Fac. Fil. Ciências e Letras/Ribeirão Preto, Universidade de São Paulo Av. Bandeirantes 3900, Ribeirão Preto (SP), 14040-901, Brasil.
ABSTRACT In this work, we report a new intercalation reaction: three different n-alkylamines (nbutylamine, n-hexylamine and n-octylamine), in vapor phase, were intercalated into nondispersed vanadium pentoxide xerogel and into this lamellar material homogeneously dispersed in Si–O–Si network (obtained by polycondensation of the silicon alkoxide) interpenetrated with V–O–V and V–OH–V polymeric chains. The reaction with non-dispersed xerogel leads to increase of interlamelar distance for low time of reaction (up to 2 hours) and after 24 hours we observed a new phase. In contrast, for the reaction with xerogel dispersed in silica, it was observed only the increase of the basal distance retaining the original bi-dimensional structure (00l diffractions lines were observed); suggesting that the silica matrix stabilizes the vanadium pentoxide structure as the result of a mutual "solubility" due to cross-linking and entanglement of both components. In addition, for this reaction it was observed a selective amine intercalation. The reactions were monitored using powder X-ray diffraction, Fourier-transform infrared and electronic spectroscopy, electron paramagnetic resonance and scanning electron microscopy.
INTRODUCTION Despite of the intensive studies, intercalation compounds with V2O5⋅nH2O xerogel is still attracting considerable attention due to a broad variety of structural versatility, i.e., the large interlamelar domain allows the access of different quest species. Consequently, a variety of guest species have been intercalated (such as alcohols, pyridine, metal ions, complexes, polymers and alkylamines) with the retention of the lamellar structure and residual water molecules in the gap between the vanadium pentoxide sheets [1]. With regard to the insertion of amines, the investigations have advanced from the fundamental understandings of the intercalation mechanism and host-guest interactions to synthesis of nanostructured oxides using amines as structure-directing templates. From the previous papers describing the intercalation of amines in a wide variety of host structures, there is another approach that involves the vapor-solid reaction aiming to prepare layered compounds [2,3]. In this context, the main objective of this work consist in reporting new experimental results concerning the solids resulted from the intercalation of the alkylamines in the vapor phase (CnH2n+1NH2) in the interlayer vanadium pentoxide xerogel and compare the intercalation when the host structure is dispersed in an inert matrix such as silica. The influence of the length of the hydrocarbon chain of the alkylamines homologous series, the time of reaction, the electrochemical properties were studied on the basis of powder
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