The use of FAU zeolite as a starting material was found to enhance the crystallization rate of *BEA zeolite, suggesting that the dissolution of FAU zeolite provides locally ordered aluminosilicate species that assemble and evolve into *BEA zeolite. Here we show experimental findings that indicate the presence of such locally ordered aluminosilicate species in intermediate phases involved in the hydrothermal conversion of FAU zeolite into *BEA zeolite. On the basis of the previous fact that cetyltrimethylammonium (CTA + ) cations seem to be able to preserve zeolitic fragments or seeds and retain them in the mesoporous framework, this method was applied to the characterization of the obtained intermediate phases. From the detailed characterization of mesoporous products, the different characteristics were found to be observed between intermediate phases. Namely, as the more disordered arrangement was found in the mesoporous products, the presence of evolved, locally ordered aluminosilicate species was strongly indicated.
Lamellar mesostructured calcium phosphates constructed by ionic bonds were prepared by using n-alkylamines (n-C n H 2n+1 NH 2 , n = 8−18) at room temperature in the mixed solvent systems of aliphatic alcohol (C n H 2n+1 OH, n = 1−4) and water, and the synthetic conditions were investigated in detail. The mixed solvent systems suppressed the formation of crystalline calcium phosphates like brushite (CaHPO 4 ・2H 2 O), monetite (CaHPO 4), and so on as discrete phases, successfully affording pure lamellar mesostructured calcium phosphates. Although the excess amount of water in the reaction systems allowed the formation of hydrated phases like brushite, the formation of brushite was suppressed by using the mixed solvent systems. Synthesis at low temperatures in the mixed solvent systems prevented calcium phosphate species from crystallizing to provide crystalline calcium phosphates like anhydrous monetite. Other crystalline phases such as hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2) were not also formed in the conditions with the Ca/P molar ratios in the range of 0.7−1.0 in the starting mixtures. The Ca/P molar ratio of the lamellar mesostructured calcium phosphates was ca. 1.0, calculated by 31 P MAS NMR and elemental analysis data. Interestingly, the kind of alcohols strongly influenced the solubilities of calcium phosphate species and n-alkylamines, and then lamellar mesostructured phases were obtained with some morphological variation.
Mesostructured calcium phosphates constructed by ionic frameworks were synthesized using carboxylic acid- and amine-type surfactants in mixed solvent systems of ethanol and water. A lamellar mesostructured calcium phosphate was prepared using palmitic acid as an anionic surfactant, as in the case using n-alkylamines. A wormhole-like mesostructured calcium phosphate can be obtained using dicarboxyl N-lauroyl- l-glutamic acid, whose headgroup is larger than that of palmitic acid. Similar mesostructured product was obtained using 4-dodecyldiethylenetriamine with a large headgroup containing two primary amine groups. Interactions of carboxyl and primary amino groups in the surfactant molecules with inorganic species are quite important for the formation of mesostructured calcium phosphates. The Ca/P molar ratio of mesostructured calcium phosphates was strongly affected by the molecular structure of surfactants containing carboxyl and primary amino groups. Ca-rich materials can be obtained using carboxylic acid-type surfactants (Ca/P approximately 1.7) rather than amine-type surfactants (Ca/P approximately 1.0).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.