Crystalline polysilicate magadiite with intercalated n-alkylmonoamine and some correlations involving thermochemical data |
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Authors: | Giovanni C Petrucelli Mauricio A Meirinho Thais R Macedo Claudio Airoldi |
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Institution: | aInstituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, São Paulo, Brazil |
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Abstract: | Synthesized hydrated lamellar acidic crystalline magadiite (H2Si14O29·2H2O) nanocompound was used as host for intercalation of polar n-alkylmonoamine molecules of the general formula H3C(CH2)nNH2 (n = 1–6) in aqueous solution. The original interlayer distance (d) of 1500 pm, determined by X-ray powder diffraction patterns, increases after intercalation. The values correlated with the number of aliphatic amine carbon (nc) atoms: d = (1312 ± 11) + (21 ± 2)]nc. The amount of intercalated amines (Ns), decreased as nc increased: Ns = (5.82 ± 0.04) ? (0.45 ± 0.01)]nc. The acidic layered nanocompound was calorimetrically titrated with the amines and the thermodynamic data gave exothermic values for all guest molecules, as shown by the correlation: ΔintH = ?(24.45 ± 0.49) ? (1.91 ± 0.10)]nc and d = (1576 ± 16) ? (10.8 ± 1.0)]ΔintH. The negative values of the Gibbs energies and the positive entropies also presented the correlations: ΔintG = ?(22.8 ± 0.2) ? (0.2 ± 0.1)]nc and ΔintS = (6 ± 1) + (5 ± 1)]nc, respectively. |
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Keywords: | Magadiite n-Alkylmonoamine Intercalation Calorimetry |
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