Rhodium complexes have been entrapped inside the porous systems of inorganic or hybrid matrices via the sol-gel method. The resulting materials were tested as catalysts in hydroformylation reactions. The microporous materials could be recycled without any rhodium leaching, being active even in the absence of a solvent. High turnover numbers were obtained in the hydroformylation of either 1-hexene or 1-decene. However, the characteristics of the matrix could not be related to the addition (or not) of a hybrid organic-inorganic co-condensation agent, but appeared to depend on the nature of the rhodium complex.
In this study, an aluminosilicate residue from insulators of high voltage transformers was used for the adsorption of basic dyes. The absorbent was characterized by X-ray fluorescence analysis, X-ray diffraction analysis, scanning electron microscopy, multimolecular adsorption theory (Branauer-Emmet-Teller (BET)) and determination of the point of zero charge (pHPZC). The effect of solution pH and adsorbent mass, the kinetic and thermodynamic behavior at different temperatures and the application of non-linear isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushevich were investigated. The pHPZC value for the aluminosilicate was 3.7. The best conditions for adsorption of methylene blue and crystal violet dyes were pH 8.0 and adsorbent mass of 1100 mg in 25 mL. The best fit for the experimental data was obtained applying the pseudo-second-order kinetic model, with an equilibrium time of 480 to 720 min, and the activation energy suggests a physical adsorption mechanism. Isothermal parameters suggest a heterogeneous, favorable and predominantly physical surface adsorption. The thermodynamic studies indicated that the adsorption process is not spontaneous and is exothermic and the Gibbs energy values (ΔGº) suggest physisorption.
3 were immobilized in inorganic and hybrid silica matrices via the sol-gel process. The inorganic matrices were prepared with tetramethylorthosilicate while for the hybrid ones 1,4-bis(triethoxysilyl)benzene or 1,2-bis(triethoxysilyl)ethane were used as co-condensation agents. The system based on [Rh(CO) 2 (acac)]/ Ph 2 P(CH 2 ) 2 S(CH 2 ) 3 Si(OMe) 3 was active in the hydroformylation of 1-hexene and 1-octadecene without any rhodium leaching. It could also be used in the absence of a solvent, as observed in the hydroformylation of 1-decene. Although the best system was based on a hybrid microporous matrix, no straightforward correlation between matrix composition, condensation degree and surface properties could be found.
Zeólitas são aluminossilicatos com propriedades físico-químicas largamente exploradas na indústria. Em particular, sua capacidade de troca iônica tem sido usada na remoção de cátions cálcio e magnésio da água, evitando a dureza da água. A Dinâmica Molecular é uma ferramenta computacional para se obter informações sobre o comportamento das partículas que compõem um sistema. Nesse sentido, objetivou-se neste trabalho estudar a interação de íons cálcio com Zeólita Clinoptilolita, usando a Dinâmica Molecular de Car-Parrinello. Foram simuladas duas trajetórias: a primeira formada por um fragmento linear de clinoptilolita com um íon cálcio e uma segunda, formada por um fragmento cíclico de clinoptilolita com um íon cálcio, que foram dispostas em caixas cúbicas de 15Å e 16Å, respectivamente. A primeira trajetória foi simulada por 43,08 ps e a segunda por 41,86 ps, ambas usando conjunto de funções de base de ondas planas com energia cinética de corte de 25Ry, pseudopotenciais ultrassoft de Vanderbilt, massa fictícia de 400 a.u. e funcional de troca e correlação PBE. As trajetórias foram salvas a cada 5 passos de 5 atu. Percebe-se que o íon cálcio interage fortemente com 4 oxigênios da zeólita linear e 6 oxigênios da zeólita cíclica. Observa-se que há uma tendência da ciclização da estrutura zeolítica linear, devido à forte interação entre oxigênio e íon cálcio. Na zeólita cíclica, essa interação faz com que o íon cálcio fique retido na cavidade da estrutura. Assim, conclui-se que íons cálcio tem grande afinidade pela zeólita clinoptilolita.
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