Síntese e caracterização espectroscópica de novos vanadosilicatos utilizando templates orgânicos derivados de piperidinas
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Data
2016-03-11
Autores
Contro, Janine [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Foram sintetizados neste trabalho novos vanadosilicatos, para suas sínteses foram utilizadas moléculas orgânicas derivadas de 3,5-dimetilpiperidina (SDAs 1 – 4) e 2,6-dimetilpiperidina (SDAs 5 – 8) em sua mistura reacional. Os vanadosilicatos foram nomeados seguindo a numeração dos SDAs utilizados em suas sínteses (VN1 a VN8). As caracterizações físico-químicas dos vanadosilicatos foram realizadas utilizando-se técnicas como difração de raios-X (DRX), microscopia eletrônica de varredura (MEV), espectroscopia no infravermelho (FT-IR), espectroscopia Raman, espectroscopia no UV – Visível e ressonância magnética nuclear com rotação em torno do ângulo mágico (RMN-MAS) no estado sólido para os núcleos de 13C, 29Si e 51V. Os resultados experimentais indicam que as moléculas orgânicas podem atuar como agentes direcionadores de estrutura (SDAs). Os SDAs 1, 3, 4 e 5 direcionaram a formação dos vanadosilicatos VN1, VN3, VN4 e VN5 isomorfos ao titaniosilicato ETS-10 e ao vanadosilicato do tipo AM-6, enquanto os SDAs 2, 6, 7 e 8 direcionam a estrutura de novos vanadosilicatos (VN2, VN6, VN7 e VN8). Evidências experimentais da incorporação de vanádio na estrutura cristalina dos materiais foram obtidas por FT-IR, UV – Visível, 29Si RMN-MAS. Na espectroscopia no infravermelho (FT-IR) o sinal localizado na frequência 870 cm-1 é proveniente da vibração da ligação V-O e o sinal centrado na frequência 1030 cm-1 é proveniente da vibração dos grupos vanadila. Na espectroscopia no UV – Visível o comprimento de onda 600 nm representa os grupos vanadila e os comprimentos onda 450 e 545 nm indicam a presença de vanádios em coordenação octaédrica distorcida (VN2) e ordenada (VN1, VN3 e VN4), respectivamente. E no caso do RMN de 29Si o sinal centralizado em -93 ppm é proveniente de núcleos de silício da forma Si(3Si, 1V), estes dados comprovam a incorporação do vanádio na rede cristalográfica do material microporoso. A espectroscopia no UV – Visível juntamente com a ressonância magnética nuclear de 29Si sugerem que os vanadosilicatos isomorfos ao titaniosilicato VN1, VN3, VN4 e VN5 apresentam uma rede cristalográfica mais ordenada que os vanadosilicatos VN2, VN6, VN7 e VN8. Visto que a espectroscopia no UV – Visível indica que os octaedros VO6 dos vanadosilicatos isomorfos ao ETS-10 são mais regulares que os octaedros de vanádio dos novos vanadosilicatos, e os resultados experimentais de RMN-MAS de 29Si revelam que os vanadosilicatos isomorfos ao ETS-10 apresentam somente o sinal centralizado em -93 ppm, proveniente de núcleos de silício da forma Si(3Si, 1V), enquanto os novos vanadosilicatos apresentam, além do sinal centralizado em -93 ppm, um novo sinal centralizado em -110 ppm, proveniente de núcleos de silício da forma Si(4Si, 0V).
New vanadosilicates were synthesized in this work. They have been synthesized using organic molecules derivatives of 3,5-dimethylpiperidine (SDAs 1 – 4) and 2,6-dimethylpiperidine (SDAs 5 – 8) in their reactional mixture. The vanadosilicates were named using the same numbers of the SDA used in their synthesis (VN1 to VN8). Physicochemical characterization of the new vanadosilicates was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), Raman spectroscopy, UV – Visible spectroscopy (UV – Vis), solid state 13C, 29Si and 51V magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The experimental results suggest that the organic molecules can act as structure directing agents (SDAs). The SDAs 1, 3, 4 and 5 directed the synthesis to the formation of vanadosilicates VN1, VN3, VN4 and VN5 isomorphs to titanosilicate ETS-10 and vanadosilicate AM-6; on the other hand the SDAs 2, 6, 7 and 8 show selectivity to the formation of new vanadosilicates (VN2, VN6, VN7 and VN8). Experimental evidences of the vanadium incorporation into the vanadosilicate framework were obtained by FT-IR, UV – Vis and 29Si MAS NMR. The infrared spectroscopy has a signal at the frequency of 870 cm-1 designed to the vibration of V-O bond and the signal at the frequency of 1030 cm-1 designed to the vibration of vanadyl groups. The UV – Vis spectroscopy reveals the presence of vanadyl groups at 600 nm and the wavelengths 450 and 545 nm indicate the presence of distorted (VN2) and ordely (VN1, VN3 and VN4) octahedrally coordinated vanadium, respectively. And the 29Si MAS NMR shows a chemical shift centred at -93 ppm assigned to the Si(3Si, 1V) neighbourhood. UV – Vis spectroscopy and 29Si MAS NMR evidence that the vanadosilicates VN1, VN3, VN4 and VN5, isomorphs to ETS-10, show their framework more crystalline than the new vanadosilicates framework (VN2, VN6, VN7 and VN8). This affirmative is supported by both UV – Vis and 29Si MAS NMR data. UV – Vis data indicates that VO6 octahedra in vanadosilicates isomorphs to ETS- 10 are more regular than the VO6 octahedra in the new vanadosilicates. 29Si MAS NMR experimental data shows that vanadosilicates isomorphs to ETS-10 have only one chemical shift centred at -93 ppm, assigned to the Si(3Si, 1V) neighbourhood, while the new vanadosilicates have two chemical shifts that one centred at -93 ppm and other centred at -110 ppm assigned to Si(4Si, 0V) neighbourhood.
New vanadosilicates were synthesized in this work. They have been synthesized using organic molecules derivatives of 3,5-dimethylpiperidine (SDAs 1 – 4) and 2,6-dimethylpiperidine (SDAs 5 – 8) in their reactional mixture. The vanadosilicates were named using the same numbers of the SDA used in their synthesis (VN1 to VN8). Physicochemical characterization of the new vanadosilicates was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), Raman spectroscopy, UV – Visible spectroscopy (UV – Vis), solid state 13C, 29Si and 51V magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The experimental results suggest that the organic molecules can act as structure directing agents (SDAs). The SDAs 1, 3, 4 and 5 directed the synthesis to the formation of vanadosilicates VN1, VN3, VN4 and VN5 isomorphs to titanosilicate ETS-10 and vanadosilicate AM-6; on the other hand the SDAs 2, 6, 7 and 8 show selectivity to the formation of new vanadosilicates (VN2, VN6, VN7 and VN8). Experimental evidences of the vanadium incorporation into the vanadosilicate framework were obtained by FT-IR, UV – Vis and 29Si MAS NMR. The infrared spectroscopy has a signal at the frequency of 870 cm-1 designed to the vibration of V-O bond and the signal at the frequency of 1030 cm-1 designed to the vibration of vanadyl groups. The UV – Vis spectroscopy reveals the presence of vanadyl groups at 600 nm and the wavelengths 450 and 545 nm indicate the presence of distorted (VN2) and ordely (VN1, VN3 and VN4) octahedrally coordinated vanadium, respectively. And the 29Si MAS NMR shows a chemical shift centred at -93 ppm assigned to the Si(3Si, 1V) neighbourhood. UV – Vis spectroscopy and 29Si MAS NMR evidence that the vanadosilicates VN1, VN3, VN4 and VN5, isomorphs to ETS-10, show their framework more crystalline than the new vanadosilicates framework (VN2, VN6, VN7 and VN8). This affirmative is supported by both UV – Vis and 29Si MAS NMR data. UV – Vis data indicates that VO6 octahedra in vanadosilicates isomorphs to ETS- 10 are more regular than the VO6 octahedra in the new vanadosilicates. 29Si MAS NMR experimental data shows that vanadosilicates isomorphs to ETS-10 have only one chemical shift centred at -93 ppm, assigned to the Si(3Si, 1V) neighbourhood, while the new vanadosilicates have two chemical shifts that one centred at -93 ppm and other centred at -110 ppm assigned to Si(4Si, 0V) neighbourhood.
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3,5-dimetilpiperidina, 2,6-dimetilpiperidina, 29Si RMN-MAS, 51V RMN-MAS, FT-IR, UV - Vis, Zeólitas, Vanadosilicato, Espectroscopia Raman, Zeolites, Vanadosilicate, 3,5-dimethylpiperidine, 2,6-dimethylpiperidine, Si MAS-NMR, V MAS-NMR, FT-IR, Raman spectroscopy, UV – Vis