Fracionamento do bagaço de cana-de-açúcar em xilana, lignina e açúcar fermentável via processo organosolv em meio alcalino
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2020-10-27
Autores
Cardoso, Filipi de Oliveira [UNESP]
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Universidade Estadual Paulista (Unesp)
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A partir da biomassa lignocelulósica podem ser obtidos produtos de valor agregado, que podem ser empregados no setor industrial e de biocombustíveis. Sua composição majoritária se dá por celulose, hemicelulose e lignina. Entretanto, essa biomassa necessita de uma etapa de pré-tratamento para que ocorra o fracionamento dos seus componentes. Para realizar esse fracionamento e promover a recuperação desses componentes a estratégia definida foi o pré-tratamento com solvente orgânico e um reagente alcalino, caracterizando o processo organosolv. O objetivo foi promover a separação da xilana, além de obter lignina, a qual é o principal produto do processo organosolv e açúcares fermentáveis. Os pré-tratamentos foram realizados em meio alcalino seguindo um planejamento experimental (hidróxido de sódio de 3 % a 8 % massa de base por massa de material, de 120 ºC a 180 °C, solvente de 30 % a 70 %, e de 25 a 65 min de reação). A separação da xilana e lignina foi efetuada através de mudanças no processo tradicional: após o tratamento térmico a xilana foi precipitada através da adição de 100 mL de etanol e a lignina foi posteriormente precipitada com a acidificação do meio. O ensaio que apresentou o melhor resultado para precipitação da xilana foi exposto a 180 ºC, 65 min, 30 % de solvente e 8 % de hidróxido de sódio. Esta condição resultou em uma recuperação de 88 % de xilana. O ensaio que apresentou o melhor resultado para precipitação da lignina (97 %) teve como parâmetros as seguintes condições: 150 ºC, 45 min, 50 % solvente e 5,5 % de hidróxido de sódio. Nesta condição foi obtido 73 % de xilana, o que foi indicado como mais adequado para recuperação em conjunto de xilana e lignina. Para a recuperação de açúcares fermentáveis a melhor recuperação ocorreu nas seguintes condições: 120 ºC, 65 min, 3% de hidróxido de sódio e 30% de solvente. A concentração de hidróxido de sódio foi a variável de maior influência na recuperação dos três componentes, o etanol se mostrou um parâmetro relevante na seletividade dos componentes, uma vez que quanto maior a quantidade de etanol, maior a recuperação da lignina, entretanto concentrações de etanol elevadas prejudica a recuperação de hemicelulose. Uma condição que se mostrou ideal para a recuperação dos três componentes foram as do ponto central: 150 ºC, 45 min, 50% de solvente e 5,5 % de hidróxido de sódio. Nessas condições a recuperação da lignina 97 %, da xilana 73 % e de açúcares fermentáveis 87 %.
From the lignocellulosic biomass, value-added products can be selected, which can be used in the industrial and biofuels sector. Its main composition is made of cellulose, hemicellulose and lignin. However, this biomass requires a pre-treatment step for the fractionation of its components to occur. To carry out this fractionation and promote the recovery of these components, the strategy defined was the pre-treatment with organic solvent and an alkaline reagent, characterizing the organosolv process. The objective was to promote the separation of xylan, in addition to obtaining lignin, which is the main product of the organosolv process and fermentable sugars. Pretreatments were carried out in an alkaline medium following an experimental design (sodium hydroxide of 3% to 8% mass of base per mass of material, from 120 ºC to 180 ° C, solvent from 30% to 70%, and 25 65 min of reaction). The separation of xylan and lignin was carried out through changes in the traditional process: after heat treatment, xylan was precipitated by the addition of 100 ml of ethanol and the lignin was subsequently precipitated with acidification of the medium. The test that shows the best result for excluding xylan was exposed to 180 ºC, 65 min, 30% solvent and 8% sodium hydroxide. This condition resulted in an 88% recovery of xylan. The test that presents the best result for the separation of lignin (97%) had the following conditions as parameters: 150 ºC, 45 min, 50% solvent and 5.5% sodium hydroxide. In this condition, 73% xylan was established, which was indicated as the most suitable for joint recovery of xylan and lignin. For the recovery of fermentable sugars, the best recovery occurred under the following conditions: 120 ºC, 65 min, 3% sodium hydroxide and 30% solvent. The concentration of sodium hydroxide was the variable of greatest influence in the recovery of the three components, ethanol stood out as a relevant parameter in the selectivity of the components, since the greater the amount of ethanol, the greater the recovery of lignin, high ethanol is determined impairs the recovery of hemicellulose. A condition that proved to be ideal for the recovery of the three components was that of the central point: 150 ºC, 45 min, 50% solvent and 5.5% sodium hydroxide. Under these conditions, the recovery of lignin 97%, xylan 73% and fermentable sugars 87%.
From the lignocellulosic biomass, value-added products can be selected, which can be used in the industrial and biofuels sector. Its main composition is made of cellulose, hemicellulose and lignin. However, this biomass requires a pre-treatment step for the fractionation of its components to occur. To carry out this fractionation and promote the recovery of these components, the strategy defined was the pre-treatment with organic solvent and an alkaline reagent, characterizing the organosolv process. The objective was to promote the separation of xylan, in addition to obtaining lignin, which is the main product of the organosolv process and fermentable sugars. Pretreatments were carried out in an alkaline medium following an experimental design (sodium hydroxide of 3% to 8% mass of base per mass of material, from 120 ºC to 180 ° C, solvent from 30% to 70%, and 25 65 min of reaction). The separation of xylan and lignin was carried out through changes in the traditional process: after heat treatment, xylan was precipitated by the addition of 100 ml of ethanol and the lignin was subsequently precipitated with acidification of the medium. The test that shows the best result for excluding xylan was exposed to 180 ºC, 65 min, 30% solvent and 8% sodium hydroxide. This condition resulted in an 88% recovery of xylan. The test that presents the best result for the separation of lignin (97%) had the following conditions as parameters: 150 ºC, 45 min, 50% solvent and 5.5% sodium hydroxide. In this condition, 73% xylan was established, which was indicated as the most suitable for joint recovery of xylan and lignin. For the recovery of fermentable sugars, the best recovery occurred under the following conditions: 120 ºC, 65 min, 3% sodium hydroxide and 30% solvent. The concentration of sodium hydroxide was the variable of greatest influence in the recovery of the three components, ethanol stood out as a relevant parameter in the selectivity of the components, since the greater the amount of ethanol, the greater the recovery of lignin, high ethanol is determined impairs the recovery of hemicellulose. A condition that proved to be ideal for the recovery of the three components was that of the central point: 150 ºC, 45 min, 50% solvent and 5.5% sodium hydroxide. Under these conditions, the recovery of lignin 97%, xylan 73% and fermentable sugars 87%.
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Palavras-chave
Biomassa, Cana-de-açúcar, Organosolv, Extração de Lignina, Extração de Hemicelulose, Biomass, Sugar cane, Alkaline pretreatment, Lignin extraction, Hemicellulose extraction, Pré-tratamento alcalino