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Otimização de um reator descontínuo para reações de biorrefinação usando catalisadores bifuncionais
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Abstract(s)
No presente trabalho, desenvolveram-se catalisadores bifuncionais para o estudo da reação de hidrodesoxigenação (HDO) do guaiacol e anisol, que são moléculas modelo da biomassa. Os zeólitos foram selecionados como suporte ativo, devido à acidez intrínseca, responsável pela ativação da ligação C−O da molécula reagente. A reação ocorre na presença de hidrogénio e, necessita de uma função metálica para efeitos de hidrogenação, bem como, para a clivagem da ligação C−C. Para este trabalho, selecionaram-se como zeólitos, o Y e o MCM-22 e, como função metálica, a Platina, o Níquel e misturas dos dois metais. O zeólito Y foi utilizado na forma comercial e, no caso do MCM-22, procedeu-se à sua síntese, realizando-se posteriormente um tratamento alcalino assistido por surfactante, CTAB, de modo a alterar as propriedades texturais. A preparação dos catalisadores bifuncionais executou-se a partir de impregnação por solvente mínimo e mecanoquímica com almofariz e moinho de bolas planetário, onde se analisou a influência dos parâmetros de moagem, isto é, o tempo e a velocidade de rotação, nas propriedades dos catalisadores e no comportamento catalítico. A reação de HDO ocorreu num reator descontínuo, a 250 ºC, 20 bar e 300 rpm e, os produtos foram analisados por Cromatografia Gasosa e, em alguns casos por Cromatografia Gasosa acoplada por Espetrometria de Massa. No final do estudo verificou-se que a amostra bimetálica Pt0.5_Ni1_30_200_M_R_HY, submetida à técnica mecanoquímica com o moinho de bolas, com um maior tempo de moagem, correspondente a 30 minutos e menor velocidade de rotação, isto é, 200 rpm, apresentou os melhores resultados catalíticos, tanto a nível de rendimento, como de seletividade para os produtos livres de oxigénio. Relativamente ao zeólito HMCM-22, toda a análise efetuada permitiu retirar que foi criada alguma mesoporosidade, conferindo seletividade de forma ao produto, maioritariamente com a utilização de concentrações de NaOH superiores a 0.1 M.
Abstract In the present work, bifunctional catalysts were developed to study the hydrodeoxygenation (HDO) reaction of guaiacol and anisole, which are biomass model molecules. Zeolites were selected as active support, due to their intrinsic acidity, responsible for activating the C-O bond of the reacting molecule. The reaction occurs in the presence of hydrogen and requires a metallic function for hydrogenation purposes, as well as for the cleavage of the C-C bond. For this work, zeolites, Y and MCM-22 were selected and, as metallic functions, Platinum, Nickel and mixtures of the two metals. Zeolite Y was used in the commercial form and, in the case of MCM-22, its synthesis was carried out, carrying out an alkaline treatment assisted by surfactant, CTAB. The preparation of bifunctional catalysts was carried out using minimal solvent impregnation and mechanochemistry with a mortar and planetary ball mill, where the influence of grinding parameters, that is, time and rotation speed, on the properties of the catalysts was analyzed. and catalytic behavior. The HDO reaction took place in a batch reactor, at 250 ºC, 20 bar and 300 rpm and the products were analyzed by Gas Chromatography and, in some cases, by Gas Chromatography coupled with Mass Spectrometry. At the end of the study, it was found that the bimetallic sample Pt0.5_Ni1_30_200_M_R_HY, subjected to the mechanochemical technique with the ball mill, with a longer grinding time, corresponding to 30 minutes and a lower rotation speed, that is, 200 rpm, presented the better catalytic results, both in yield and selectivity for oxygen-free products. In relation to the HMCM-22 zeolite, all the analysis carried out revealed that some mesoporosity was created, giving the product shape selectivity, mainly with the use of NaOH concentrations greater than 0.1 M.
Abstract In the present work, bifunctional catalysts were developed to study the hydrodeoxygenation (HDO) reaction of guaiacol and anisole, which are biomass model molecules. Zeolites were selected as active support, due to their intrinsic acidity, responsible for activating the C-O bond of the reacting molecule. The reaction occurs in the presence of hydrogen and requires a metallic function for hydrogenation purposes, as well as for the cleavage of the C-C bond. For this work, zeolites, Y and MCM-22 were selected and, as metallic functions, Platinum, Nickel and mixtures of the two metals. Zeolite Y was used in the commercial form and, in the case of MCM-22, its synthesis was carried out, carrying out an alkaline treatment assisted by surfactant, CTAB. The preparation of bifunctional catalysts was carried out using minimal solvent impregnation and mechanochemistry with a mortar and planetary ball mill, where the influence of grinding parameters, that is, time and rotation speed, on the properties of the catalysts was analyzed. and catalytic behavior. The HDO reaction took place in a batch reactor, at 250 ºC, 20 bar and 300 rpm and the products were analyzed by Gas Chromatography and, in some cases, by Gas Chromatography coupled with Mass Spectrometry. At the end of the study, it was found that the bimetallic sample Pt0.5_Ni1_30_200_M_R_HY, subjected to the mechanochemical technique with the ball mill, with a longer grinding time, corresponding to 30 minutes and a lower rotation speed, that is, 200 rpm, presented the better catalytic results, both in yield and selectivity for oxygen-free products. In relation to the HMCM-22 zeolite, all the analysis carried out revealed that some mesoporosity was created, giving the product shape selectivity, mainly with the use of NaOH concentrations greater than 0.1 M.
Description
Dissertação para obtenção do grau de Mestre em Engenharia Química e Biológica, na Área de Especialização de Processos Químicos
Keywords
Catalisadores bifuncionais Hidrodesoxigenação Biomassa Zeólitos Bifunctional catalysts Hydrodeoxygenation Biomass Zeolites
Citation
MATOS, Mariana Filipa Faísca – Otimização de um reator descontínuo para reações de biorrefinação usando catalisadores bifuncionais. Lisboa: Instituto Superior de Engenharia de Lisboa. 2024. Dissertação de Mestrado.