Síntese e caracterização de um novo agente sililante - imobilização na sílica gel em meio aquoso.

Abstract

The reaction of 3-aminopropyltriethoxysilane (AMPTS) with thioglycolic acid (TGA) resulted in a new sililante agent, AMPTGA. This matrix has nitrogen, oxygen and sulfur as basic centers, that have ability to adsorb metallic cations in solution. The immobilization of AMPTGA onto silica gel surface was carried out in accordance with the principles of green chemistry, which water was used as solvent and at room temperature, under stirred. The new solids were characterized by elemental analysis of CHNS, infrared spectroscopy, NMR 13C and 29Si, thermogravimetric analysis and surface area. The surface area were 0.43 m2g-1 and 193 for solids AMPTGA and Sil-AMPTGA, respectively, which were lower than that of silica gel precursor 484 m2g-1. The thermogravimetric analysis showed four mass losses for the AMPTGA and three mass losses for the Sil-AMPTGA. The infrared spectra regions of the AMPTGA recorded bands of stretch OH, CH, C=O and –S-S–. While the spectrum of Sil-AMPTGA showed stretching bands OH, CH and –Si-O-Si–. The NMR spectrum of 13C AMPTGA recorded seven chemically different carbons. While the 29Si NMR, proved only two chemical shifts at -58 and -67 ppm assigned to the types of bidentate and tridentate immobilization, respectively. The NMR spectrum of 13C-Sil AMPTGA had only three chemically different carbons. The 29Si NMR chemical shifts corresponding were assigned only a portion of the molecule silylating agent and the structure of silica. While, the elemental analysis of Si-AMPTGA showed a molar ratio C/N of only 3:1. Thus the characterizations described, confirms that the reaction of immobilization of the silylating agent, AMPTGA on silica gel in aqueous solution did not occur effectively.