Síntese e caracterização de suportes a base de óxidos de silício modificados
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2017-04-05
Autores
Soares, Isaac Vaz
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Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho descreve as sínteses e caracterizações de materiais à base de silício organofuncionalizados com 2-amino-5-(4-piridil)-1,3,4-tiadiazol (T8-Pr-APT e SG-Pr-APT) e 4 -amino-5-(4-piridil)-4H-1,2,4-triazol-3-tiol (T8-Pr-APTT e SG-Pr-APTT). Os materiais foram caracterizados por: espectroscopia na região do infravermelho (FTIR), ressonância magnética nuclear 29Si e 13C no estado sólido (RMN) e Microscopia eletrônica de varredura com Espectroscopia de energia dispersiva de raios-X (MEV-EDS). Nos estudos de batelada para os materiais, foram utilizados os íons metálicos de V(III), Fe(III), Cr(III), Cu(II), Pb(II) e os solventes foram água e etanol. Determinou-se a dose de adsorvente na solução e o tempo de equilíbrio, na qual, para o material T8-Pr-APT em todos os meios para os metais Cu, Pb e Cr, a capacidade máxima de adsorção ocorreu em 60 mg de adsorvente e para os metais restantes de 100 mg de adsorvente, o equilíbrio de adsorção em ambos os meios foi de aproximadamente 20 minutos para os metais Cu, Pb e Cr e 30 minutos para os demais, enquanto que, para o SGPr- APT em todos os meios para os metais Cu e Cr, a capacidade máxima de adsorção ocorreu em 60 mg de adsorvente e para os metais restantes de 100 mg de adsorvente, o equilíbrio de adsorção em ambos os meios foi de aproximadamente 40 minutos para todos os metais estudados. Estudou-se ainda a capacidade máxima de adsorção (Nf) para os solventes, na qual a capacidade máxima se deu em meio etanólico > aquoso. Em seguida, as isotermas de adsorção foram ajustadas pelos modelos Langmuir, Freundlich, Temkin e Dubinin-Radushkevich (D-R). Para cinética de adsorção dos metais, foram usados três modelos cinéticos como pseudoprimeira- ordem, pseudo-segunda-ordem e Elovich. Os modelos de Langmuir e Elovich foram os mais apropriados para descrever os dados de adsorção e cinética, respectivamente, de todos materiais. Os parâmetros termodinâmicos ΔGº, ΔHº e ΔSº foram avaliados para os materiais e observou-se que a adsorção de todos os metais, independentemente do adsorvente utilizado, foi um processo endotérmico e espontâneo, devido aos valores positivos de entalpia e negativo de energia livre de Gibbs, respectivamente. Os valores positivos da entropia indicam que o processo de adsorção é favorável e ocorre um aumento da desordem na interface sólido-solução. Estes resultados mostraram que os materiais possuem o mesmo comportamento termodinâmico. A atividade catalítica dos materiais suportados foram testados e comparados, utilizando complexo de molibdênio e tungstênio para epoxidação do 1-octeno, cicloocteno, cis-3-hexen- 1-ol, trans-3-hexen-1-ol e estireno, utilizando como oxidante o hidroperóxido de terc-butil (TBHP), onde ambos os materiais possuem semelhantes conversões e uma boa seletividade.
This work describes how syntheses and characterizations of silicon-based materials organofunctionalized with 2-amino-5- (4-pyridyl) -1,3,4-thiadiazole (T8-Pr-APT and SG-Pr- APT) and 4- Amino-5- (4-pyridyl) -4H-1,2,4-triazol-3-thiol (T8-Pr-APTT and SG-Pr-APTT). The materials were characterized by: infrared spectroscopy (FTIR), 29Si and 13C solid state nuclear magnetic resonance (NMR) and scanning electron microscopy with X-ray dispersive energy spectroscopy (SEM-EDS) V (III), Fe (III), Cr (III), Cu (II), Pb (II) and the solvents for ethanol and water. Determination of a adsorption dose in the solution and the equilibration time in quality for the T8-Pr-APT material in all media for the Cu, Pb and Cr metals, a maximum adsorption capacity occurred in 60 mg of adsorbent and for the remaining 100 mg adsorbent, the adsorption equilibrium in both media for approximately 20 minutes for the Cu, Pb and Cr metals and 30 minutes for the others, whereas for the SG-Pr-APT at all means for Cu and Cr metals, a maximum adsorption capacity occurred at 60 mg adsorbent and for other 100 mg adsorbent, the adsorption equilibrium in both media was about 40 minutes for all metals studied. A maximum adsorption capacity (Nf) was also studied for the solvents, in which a maximum capacity is given in ethanolic> aqueous medium. Then, as adsorption isotherms were adjusted by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) models. For kinetics of adsorption of metals, three kinetic models were used as pseudo-first-order, pseudo-second order and Elovich. The Langmuir and Elovich models were more adequate to describe the adsorption and kinetic data, respectively, of all materials. The thermodynamic parameters ΔGº, ΔHº and ΔSº were evaluated for the materials and it was observed that an adsorption of all metals, independently of the adsorbent used, for an endothermic and spontaneous process, for the enthalpy and negative positive values of Gibbs free energy , respectively. The positive entropy values indicate that the adsorption process is favorable and an increase in the disorder occurs at the solid-solution interface. These results show that the materials have the same thermodynamic behavior. The catalytic activity of the supported materials was tested and compared using a molybdenum and tungsten complex for the epoxidation of 1-octene, cyclooctene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene, Oxidant Or tert-butyl hydroperoxide (TBHP), where both materials have conversions and good selectivity
This work describes how syntheses and characterizations of silicon-based materials organofunctionalized with 2-amino-5- (4-pyridyl) -1,3,4-thiadiazole (T8-Pr-APT and SG-Pr- APT) and 4- Amino-5- (4-pyridyl) -4H-1,2,4-triazol-3-thiol (T8-Pr-APTT and SG-Pr-APTT). The materials were characterized by: infrared spectroscopy (FTIR), 29Si and 13C solid state nuclear magnetic resonance (NMR) and scanning electron microscopy with X-ray dispersive energy spectroscopy (SEM-EDS) V (III), Fe (III), Cr (III), Cu (II), Pb (II) and the solvents for ethanol and water. Determination of a adsorption dose in the solution and the equilibration time in quality for the T8-Pr-APT material in all media for the Cu, Pb and Cr metals, a maximum adsorption capacity occurred in 60 mg of adsorbent and for the remaining 100 mg adsorbent, the adsorption equilibrium in both media for approximately 20 minutes for the Cu, Pb and Cr metals and 30 minutes for the others, whereas for the SG-Pr-APT at all means for Cu and Cr metals, a maximum adsorption capacity occurred at 60 mg adsorbent and for other 100 mg adsorbent, the adsorption equilibrium in both media was about 40 minutes for all metals studied. A maximum adsorption capacity (Nf) was also studied for the solvents, in which a maximum capacity is given in ethanolic> aqueous medium. Then, as adsorption isotherms were adjusted by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) models. For kinetics of adsorption of metals, three kinetic models were used as pseudo-first-order, pseudo-second order and Elovich. The Langmuir and Elovich models were more adequate to describe the adsorption and kinetic data, respectively, of all materials. The thermodynamic parameters ΔGº, ΔHº and ΔSº were evaluated for the materials and it was observed that an adsorption of all metals, independently of the adsorbent used, for an endothermic and spontaneous process, for the enthalpy and negative positive values of Gibbs free energy , respectively. The positive entropy values indicate that the adsorption process is favorable and an increase in the disorder occurs at the solid-solution interface. These results show that the materials have the same thermodynamic behavior. The catalytic activity of the supported materials was tested and compared using a molybdenum and tungsten complex for the epoxidation of 1-octene, cyclooctene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene, Oxidant Or tert-butyl hydroperoxide (TBHP), where both materials have conversions and good selectivity
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Palavras-chave
Adsorção, Metais, Catalise, Silsesquioxano, Silica gel, Adsorption, Metals, Catalisys, Silsesquioxane