S?ntese de peneiras moleculares b?sicas ativas na rea??o de condensa??o de Claisen-Schmidt entre benzalde?do e acetofenona

• Autor(es): Dutra, Tamires da Silva
• Data: 2021
• Origem: Oasisbr
• Assunto(s): Materiais mesoporosos; catalisadores b?sicos; MCM-41; SBA-15; flavonona; Mesoporous materials; basic catalysts; MCM-41; SBA-15; flavonone; Engenharia Qu?mica
• Tipo de Documento: Dissertação de mestrado
• Idioma: Português

Descrição

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, CAPES, Brasil.

In this work, the mesoporous materials Si-MCM-41 and Si-SBA-15 were synthesized by a hydrothermal method, varying the time of synthesis for 24, 48 and 120 hours. Were carried out wet impregnation with 5% of Mg(NO3).6H2O to form basic sites and obtain the heterogeneous catalysts Mg/MCM-41-t and Mg/SBA-15-t. The prepared catalysts were calcined at 540 ?C to eliminate the magnesium precursor and deposition of MgO in the molecular sieves. The Si-MCM-41-t, Si-SBA-15-t and basic catalysts were characterized by X-ray diffraction (XRD), adsorption and desorption of N2 at 77 k, thermogravimetry (TG/ DTG) and backtitration. The catalysts prepared were evaluated in the Claisen-Schmidt condensation reaction between benzaldehyde and acetophenone to obtain flavonone. The samples showed a hexagonal structure and regular pore distribution, characteristic of the mesoporous materials MCM-41 and SBA-15. These characteristics were maintained after impregnation with the basic group (MgO). The Mg/MCM-41-t catalysts had pores diameters in the range of 40,6-51,7 ? and Mg/SBA-15-t between 63,0-77,16 ?. The results obtained by the catalytic test showed conversions in the range of 81,42-98,72% for the catalysts Mg/MCM-41-t and 66,57-80,08% for the catalysts Mg/SBA-15-t. The best conversion values were obtained through samples with lower pore diameter values for MCM-41 and SBA-15. To verify the importance of the basic site in the synthesis of flavonone, the catalytic test was performed with the samples of pure silica. The mesoporous material Si-MCM-41-120 showed conversion of 17,34% and Si-SBA-15-120 obtained a conversion of 12,31%. From the results it was evident that the smaller pore diameter favored the formation of flavonone and that the MgO content was fundamental to improve the catalytic activity of mesoporous Si-MCM-41 and Si-SBA-15 materials.

Neste trabalho, foi feita a s?ntese dos materiais mesoporosos Si-MCM-41 e Si-SBA-15 a partir do m?todo hidrot?rmico, variando o tempo de s?ntese em per?odos de 24, 48 e 120h. Foi realizada a impregna??o ?mida com 5% de Mg(NO3).6H2O para a gera??o de s?tios b?sicos e obten??o dos catalisadores heterog?neos Mg/MCM-41-t e Mg/SBA-15-t. Os catalisadores preparados, foram calcinados a 540 ?C para ocorrer a decomposi??o do precursor formando MgO nas peneiras moleculares. As amostras de Si-MCM-41-t, Si-SBA-15-t e os catalisadores b?sicos foram caracterizados atrav?s das t?cnicas de difra??o de raios X (DRX), adsor??o e dessor??o de N2 a 77k, termogravimetria (TG/DTG) e titula??o de retorno. Os catalisadores preparados foram avaliados na rea??o de condensa??o de Claisen-Schmidt entre benzalde?do e acetofenona para a obten??o da flavonona. As amostras sintetizadas apresentaram estrutura hexagonal e distribui??o regular de poros, caracter?stica dos materiais mesoporosos MCM-41 e SBA-15. Essas caracter?sticas foram mantidas ap?s a impregna??o de MgO. Os catalisadores Mg/MCM-41-t apresentaram poros com di?metros na faixa de 40,6-51,7 ? e Mg/SBA-15-t entre 63,0-77,16 ?. Os resultados obtidos atrav?s do teste catal?tico apresentaram convers?es de 81,42-98,72% utilizando os catalisadores b?sicos Mg/MCM-41-t e de 66,57-80,08% com catalisadores b?sicos Mg/SBA-15-t. Os melhores valores de convers?o foram obtidos atrav?s das amostras com menores valores de di?metro de poros, tanto para o MCM-41 quanto para o SBA-15. Para verificar a import?ncia dos s?tios b?sicos na s?ntese da flavonona, foi feito o teste catal?tico com as amostras de s?lica pura. O material mesoporso Si-MCM-41-120 apresentou convers?o de 17,34% e o Si-SBA-15-120 obteve uma convers?o de 12,31 %. A partir dos resultados ficou evidente que o menor di?metro de poros favoreceu a forma??o da flavonona e que o teor de MgO foi fundamental para melhorar a atividade catal?tica dos materiais mesoporosos Si-MCM-41 e Si-SBA-15.