Desempenho catalítico de óxidos multifuncionais sintetizados por spray pirólise para a obtenção de biodiesel: investigação estrutural
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Data
2019-04-30
Autores
Storti, Fernando
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho foram investigados a síntese, por Spray Pirólise, e a caracterização de catalisadores heterogêneos de estrutura perovskita para obtenção de biodiesel via rota etílica. Em uma primeira etapa foram sintetizados nanopós à base de titanatos de estequiometria CaTiO3 e das soluções sólidas de Ca1-xKxTiCux/2O3, onde x = 0,10 ≤ x ≤ 0,50, de estrutura perovskita. Esta síntese é baseada na pirólise de um aerossol produzida por pulverização ultrassônica. A otimização dos parâmetros necessários à obtenção de partículas nanoestruturadas e de suas soluções sólidas foi investigada por difração de raios X, com o refinamento dos parâmetros estruturais pelo método realizado de Rietveld, considerando o grupo espacial Pbnm. As partículas também foram caracterizadas por espectroscopia vibracional de absorção na região do infravermelho (I.V.), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), onde foi possível observar a forma das partículas. As imagens da microscopia eletrônica de transmissão mostraram partículas esféricas com tamanho entre 0,1 e 0,7 µm. A investigação dos sítios ácidos/básicos foi realizado pelo método de indicadores Hammett, o qual evidenciou a presença de sítios com maior força básica, com o aumento da adição de cátions K e Cu na estrutura pervoskita. A análise da atividade catalítica dos pós sintetizados, na obtenção de biodiesel oriundo de óleos vegetais, foi avaliada em função da temperatura, tempo do catalisador na mistura reacional, pressão, razão molar e quantidade de catalisador. Os produtos obtidos foram avaliados e calculado o grau de conversão por cromatografia gasosa acoplada a espectrometria de massa (CG-SM). O catalisador com estequiometria Ca0,7K0,3TiCu0,15O3 foi o mais eficiente, para a obtenção do biodiesel, apresentando uma elevada conversão na reação de transesterificação, em torno de 89%, a 120º C e pressão de 40 bar. O catalisador Ca0,7K0,3TiCu0,15O3 foi lavado e regenerado em forno a 600º C por 3 horas e após 3 ciclos, apresentou uma conversão de 83,2 % no primeiro ciclo, 75,9 no segundo ciclo e 71,2 % no terceiro ciclo.
In this work the synthesis, by Spray Pyrolysis, and the characterization of heterogeneous catalysts of perovskite structure to obtain biodiesel via ethyl route were investigated. In a first step, nanopoids based on CaTiO3 stoichiometry titanates and Ca1-xKxTiCux/2O3 solid solutions were synthesized, where x = 0.10 ≤ x ≤ 0.50, with perovskite structure. This synthesis is based on the pyrolysis of an aerosol produced by ultrasonic spraying. The optimization of the parameters required to obtain nanostructured particles and their solid solutions was investigated by X-ray diffraction, with the refinement of the structural parameters by the Rietveld method, considering the space group Pbnm. The particles were also characterized by infrared absorption spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), where it was possible to observe the shape of the particles. Transmission electron microscopy images showed spherical particles ranging in size from 0.1 to 0.7 μm. The investigation of the acid / base sites was performed by Hammett method, which showed the presence of sites with higher basic force, with the increase of the addition of K and Cu cations in the pervoskite structure. The analysis of the catalytic activity of the synthesized powders in the biodiesel production from vegetable oils was evaluated as a function of temperature, catalyst time in the reaction mixture, pressure, molar ratio and amount of catalyst. The obtained products were evaluated and the degree of conversion by gas chromatography coupled to mass spectrometry (CG-SM) was calculated. The catalyst with stoichiometry Ca0,7K0,3TiCu0,15O3 was the most efficient for obtaining the biodiesel, presenting a high conversion in the transesterification reaction, around 89%, at 120º C and a pressure of 40 bar. The catalyst Ca0,7K0,3TiCu0,15O3was washed and regenerated in a furnace at 600 ° C for 3 hours and after 3 cycles, presented a conversion of 83.2% in the first cycle, 75.9% in the second cycle and 71.2% in the third cycle.
In this work the synthesis, by Spray Pyrolysis, and the characterization of heterogeneous catalysts of perovskite structure to obtain biodiesel via ethyl route were investigated. In a first step, nanopoids based on CaTiO3 stoichiometry titanates and Ca1-xKxTiCux/2O3 solid solutions were synthesized, where x = 0.10 ≤ x ≤ 0.50, with perovskite structure. This synthesis is based on the pyrolysis of an aerosol produced by ultrasonic spraying. The optimization of the parameters required to obtain nanostructured particles and their solid solutions was investigated by X-ray diffraction, with the refinement of the structural parameters by the Rietveld method, considering the space group Pbnm. The particles were also characterized by infrared absorption spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), where it was possible to observe the shape of the particles. Transmission electron microscopy images showed spherical particles ranging in size from 0.1 to 0.7 μm. The investigation of the acid / base sites was performed by Hammett method, which showed the presence of sites with higher basic force, with the increase of the addition of K and Cu cations in the pervoskite structure. The analysis of the catalytic activity of the synthesized powders in the biodiesel production from vegetable oils was evaluated as a function of temperature, catalyst time in the reaction mixture, pressure, molar ratio and amount of catalyst. The obtained products were evaluated and the degree of conversion by gas chromatography coupled to mass spectrometry (CG-SM) was calculated. The catalyst with stoichiometry Ca0,7K0,3TiCu0,15O3 was the most efficient for obtaining the biodiesel, presenting a high conversion in the transesterification reaction, around 89%, at 120º C and a pressure of 40 bar. The catalyst Ca0,7K0,3TiCu0,15O3was washed and regenerated in a furnace at 600 ° C for 3 hours and after 3 cycles, presented a conversion of 83.2% in the first cycle, 75.9% in the second cycle and 71.2% in the third cycle.
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Palavras-chave
Titanato de cálcio, Perovskita, Catálise heterogênea, Caracterização estrutural, Biodiesel, Calcium titanate, Perovskite, Heterogeneous catalysis, Structural characterization