Intercalation and thermochemistry of amines in lamellar titanium phenylarsonate

Abstract

O composto lamelar fenilarsonato de titânio foi sintetizado e intercalado com alquilmonoaminas (metil a heptil), diaminoetano e diaminobutano, lutidina e α-picolina. A matriz original foi caracterizada por análise elementar, difração de raios X, análise de superfície, porosidade, espectroscopia de absorção na região do infravermelho, termogravimetria e microscopia eletrônica de varredura. Os difratogramas de raios X não mostraram aumento significativo de distâncias interlamelares, e a intercalação foi comprovada por técnicas como a termogravimetria que indicou a perda de massa correspondendo às aminas. A condição ideal de intercalação foi efetuada com injeções de 30,0x10 -6 dm 3 da amina 0,50 mol dm -3 em suspensão de aproximadamente 10x10 -3 g das matrizes. Os números de moles intercalados com as alquilmonoaminas seguiram uma ordem aleatória em relação ao aumento da cadeia alifática, com valores entálpicos de -9,18 ± 0,07; -12,10 ± 0,20; -7,61 ± 0,02; -6,88 ± 0,01; -9,47 ± 0,03; -12,84 ± 0,10 e -14,78 ± 0,10 kJ mol -1 para a seqüência das alquilmonoaminas e variaram de -3,66 ± 0,30 a -10,92 ± 1,50 kJ mol -1 para alquildiaminas. Com as aminas aromáticas não ocorreu um efeito térmico significativo nas intercalações, fato que foi atribuído ao grande volume do grupo fenila presente no interior das lamelas, que impede a inserção da base na cavidade lamelar.The lamellar compound titanium phenylarsonate was synthesized and intercalated with alkylmonoamines (methyl to heptyl), diaminoethane, diaminobutane, lutidine and α-picoline. The host was characterized through elemental analysis, X-ray diffraction, surface analysis, porosity, infrared spectroscopy, thermogravimetry and electronic scanning microscopy. The intercalated compounds did not show significant increases in the interlamellar distances through X-ray diffractometry. The intercalation was confirmed by the thermogravimetric technique, indicating mass losses that correspond to the amines. The ideal intercalation was established by adding increments of 30.0x10 -6 dm 3 of 0.50 mol dm -3 of each amine into a suspension of about 10x10 -3 g of matrix. The number of moles intercalated with alkylmonoamines followed an aleatory order in relation to the increase of the aliphatic chain and the enthalpic values gave -9. 18 ± 0.07; -12.10 ± 0.20; -7.61 ± 0.02; -6.88 ± 0.01; -9.47 ± 0.03; -12.84 ± 0.10 and -14.78 ± 0.10 kJ mol -1 for the sequence of alkylmonoamines and varied from -3.66 ± 0.30 to -10.92 ± 1.50 kJ mol -1 for the alkyldiamines. The aromatic amines presented small thermal effects and the unfavorable intercalation is attributed to the large volume of the phenyl group inside the lamella, which hinders insertion of these bases inside the lamellar cavity.Keywords: lamellar compound, intercalation, calorimetry, alkylmonoamines, alkyldiamines, aromatic amines IntroductionA huge number of natural or synthesized materials, normally classified as typical inorganic substances, embodying clays, double hydroxides, phosphates, phosphonates, graphite, silicates, niobates, ...

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