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Ion-Pairs in Aluminosilicate-Alkali Synthesis Liquids Determine the Aluminum Content and Topology of Crystallizing Zeolites.

ABSTRACT: Using hydrated silicate ionic liquids, phase selection and framework silicon-to-aluminum ratio during inorganic zeolite synthesis were studied as a function of batch composition. Consisting of homogeneous single phasic liquids, this synthesis concept allows careful control of crystallization parameters and evaluation of yield and sample homogeneity. Ternary phase diagrams were constructed for syntheses at 90 °C for 1 week. The results reveal a cation-dependent continuous relation between batch stoichiometry and framework aluminum content, valid across the phase boundaries of all different zeolites formed in the system. The framework aluminum content directly correlates to the type of alkali cation and gradually changes with batch alkalinity and dilution. This suggests that the observed zeolites form through a solution-mediated mechanism involving the concerted assembly of soluble cation-oligomer ion pairs. Phase selection is a consequence of the stability for a particular framework at the given aluminum content and alkali type.

SUBMITTER: Asselman K

PROVIDER: S-EPMC9404546 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Ion-Pairs in Aluminosilicate-Alkali Synthesis Liquids Determine the Aluminum Content and Topology of Crystallizing Zeolites.

Asselman Karel K Pellens Nick N Thijs Barbara B Doppelhammer Nikolaus N Haouas Mohamed M Taulelle Francis F Martens Johan A JA Breynaert Eric E Kirschhock Christine E A CEA

Chemistry of materials : a publication of the American Chemical Society 20220610 16

Using hydrated silicate ionic liquids, phase selection and framework silicon-to-aluminum ratio during inorganic zeolite synthesis were studied as a function of batch composition. Consisting of homogeneous single phasic liquids, this synthesis concept allows careful control of crystallization parameters and evaluation of yield and sample homogeneity. Ternary phase diagrams were constructed for syntheses at 90 °C for 1 week. The results reveal a cation-dependent continuous relation between batch s ...[more]

PMID: 36032556

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Project description:The comprehension of the nonlinear effects provided by mixed alkali effect (MAE) in oxide glasses is useful to optimize glass compositions to achieve specific properties that depend on the mobility of ions, such as the chemical durability, glass transition temperature, viscosity and ionic conductivity. Although molecular dynamics (MD) simulations have already been applied to investigate the MAE on silicates, less effort has been devoted to study such phenomenon in mixed alkali aluminosilicate glasses where alkali cations can act both as modifiers, forming non-bridging oxygens and percolation channels, and as charge compensator of the AlO4- units present in the network. Moreover, the ionic conductivity has not been computed yet; thus, the accuracy of the atomistic simulations in reproducing the MAE on the property is still open to question. In this work, we have validated five major interatomic potentials for the classical MD simulations by modelling the structure, density, glass transition temperature and ionic conductivity for three aluminosilicate glasses, (25 - x)Na2O - x(K2O) - 10(Al2O3) - 65(SiO2) (x = 0, 12.5, 25). It was observed that only the core-shell (CS) polarizable force field well reproduces the experimentally measured MAE on Tg and the ionic conductivity as well as the higher conductivity of single sodium aluminosilicate glass at low temperature and the higher conductivity of single potassium aluminosilicate glass at high temperature. The MAE is related to the suppression of jump events of the alkaline ions between dissimilar sites in the percolation channels consisting of both sodium and potassium ions as in the case of alkaline silicates. The superior reproducibility of the CS potential is originated from the larger and the flexible ring structures due to the smaller Si-O-Si inter-tetrahedra angle, creating appropriate percolation channels for ion conductivity. We also report detailed assessments for using the potential models including the CS potential for investigating MAE on aluminosilicates.

Dataset Information

Ion-Pairs in Aluminosilicate-Alkali Synthesis Liquids Determine the Aluminum Content and Topology of Crystallizing Zeolites.

Publications

Ion-Pairs in Aluminosilicate-Alkali Synthesis Liquids Determine the Aluminum Content and Topology of Crystallizing Zeolites.

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