Functionalized silica synthesized by sol-gel process

This work considers some aspects of the chemistry involved in the preparation and description of silicon oxide functionalized by sol-gel process. In this work we studied the synthesis and measured the properties of silicon oxide functionalized with 3-chloropropyl, through a sol-gel process. Thermogravimetic analysis, infrared spectra, and elemental analyses were measured. The samples were prepared in the following proportions of tetraethylorthosilicate (TEOS): 3-chloropropyl trimethoxisilane molar ratio: 1:0, 1:1, 2:1, 3:1 and 4:1. The thermogravimetric data for the resulting materials established the 'minimum formulae' 2:0, 3:1, 4.1, 7:1 and 11:1, respectively. As expected, the relative amount of water is inversely proportional to the presence of propyl groups. Infrared data show Si-C and -CH2-vibration modes at 1250 to 1280 and 2920 to 2940 cm(-1), respectively. Thermogravimetric data and infrared spectra showed that inorganic polymers contained organic polymers. (C) 1999 Elsevier B.V. B.V. All rights reserved

Effect of high-energy ball milling in the structural and textural properties of kaolinite

Through the process of high-energy ball milling it is possible to obtain solid materials with higher surface area and different particle sizes. These characteristics are very important for some application such as adsorption. Besides, applications of some clays depend on the functionalization which, for kaolinite, takes place in the aluminol groups. Modification in the structural and textural properties of kaolinite by high-energy milling can improve functionalization of kaolinite due to the exposure of aluminol groups. In this work studies were done on the influence of high-energy ball milling on the morphological properties of kaolinite, taking into account parameters such as filling of the miller, number of balls and amount of mass to be milled. Moreover, studies involving milling kinetics of purified kaolinite were carried out to verify modification in the morphology of kaolinite with milling time

<b>Comportamento térmico de alguns fármacos e medicamentos</b>

<p class="MsoNormal" style="margin: 0cm 0cm 0pt; line-height: normal; text-align: justify; mso-layout-grid-align: none;"> A técnica de análise térmica apresenta aplicações em diversos ramos da ciência, entre eles a indústria farmacêutica, a qual pode utilizá-la para caracterização e estudo das matérias primas e produtos finais. Os compostos farmacêuticos apresentam diferentes formas morfológicas ou estruturais, que afetam diretamente na sua estabilidade, ação e liberação. O desenvolvimento e fabricação de medicamentos requerem intenso cuidado devido a pureza, qualidade e estabilidade dos componentes. Um dos itens para se obter uma formulação estável e efetiva depende dos cuidados na escolha dos excipientes utilizados, onde uma de suas propriedades é a de interferir na biodisponibilidade e proteção do fármaco frente a degradação. Neste trabalho foram utilizadas técnicas de análise térmica (TG/DTG/ DSC/DTA) e a espectroscopia Raman para estudar possíveis interações entre o fármaco e seus excipientes. Foram selecionados para o estudo os medicamentos Aspirina<sup>®</sup> e AAS<sup>®</sup>, comparados com o seu princípio ativo ácido acetil salicílico. As amostras não sofreram pré tratamento e foram analisadas como adquiridas no mercado. Os resultados obtidos através das técnicas de análise térmica evidenciaram uma possível interação entre os diferentes excipientes utilizados e o princípio ativo. Os espectros Raman corroboram com os resultados obtidos das análises térmicas dos medicamentos. Através dos resultados obtidos concluímos que as diferentes composições existentes na formulação dos medicamentos podem promover mudanças em suas propriedades físicas e conseqüentemente na sua atividade biológica. Palavras-chave: análise térmica; ácido acetil salicílico; Raman. </p&gt

Green and selective oxidation reactions catalyzed by kaolinite covalently grafted with Fe(III) pyridine-carboxylate complexes

The immobilization of Fe(III) picolinate and Fe(III) dipicolinate complexes on kaolinite furnished heterogeneous catalysts, whose catalytic activity was evaluated. The precursor materials were kaolinite grafted with picolinic (Ka-pa) and dipicolinic (Ka-dpa) acids obtained by melting of the pyridine carboxylic acids. To obtain the catalysts Fe(Ka-pa)-n and Fe(Ka-dpa)-n (n = 1, 2, or 3 is the ligand/Fe ratio), the precursors were suspended in Fe3+ solutions with cation/ligand ratios of 1:1, 1:2, or 1:3. The resulting materials were characterized by thermal analyses (simultaneous TG/DTA), X-ray diffraction, UV/vis and infrared spectroscopies, and transmission electron microscopy. The grafted complexes were employed as heterogeneous catalysts in the epoxidation of cis-cyclooctene to cis-cyclooctenoxide and in the oxidation of cyclohexane to cyclohexanol and cyclohexanone at ambient temperature and pressure. Hydrogen peroxide was used as oxygen donor at a catalyst/oxidant/substrate molar ratio of 1:300:100. Fe(Ka-pa)-n catalysts were very efficient for cis-cyclooctene epoxidation (38% conversion). For cyclohexane oxidation, Fe(Ka-dpa)-n was 100% selective for cyclohexanone formation, with substrate conversion of 14%. This last series of catalysts was also very effective in the Baeyer–Villiger reaction, with 60% substrate conversion and 100% selectivity for ξ-caprolactone. After reuse (5 times), the catalysts still led to high substrate conversion