Pré-tratamento de palha de cana-de-açúcar empregando ozonólise, em meio aquoso alcalino e em solventes de baixo ponto eutético para a obtenção de açúcares fermentáveis
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Data
2021-11-03
Autores
Orduña Ortega, Julieth [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Existe atualmente uma tendência mundial no uso de fontes renováveis para processos de obtenção de biocombustíveis, bioenergia e biocompostos. A biomassa lignocelulósica é considerada uma fonte de grande valor, entretanto para alcançar maior valoração é preciso realizar a desconstrução da sua estrutura, a fim de diminuir sua recalcitrância. Existem diferentes metodologias que levam à extração dos biocompostos, sendo eles a celulose, hemicelulose e a lignina, ou derivado desses. Porém, estes métodos ainda se encontram em pesquisa, pois em sua maioria, são ineficientes, envolvem um elevado número de passos, são economicamente inviáveis e/ou precisam de altos consumos energéticos. Nas últimas décadas, adicionalmente, procura-se que sejam realizados em condições de reação condizentes com a química verde. No estudo presente, foi estudado o uso de palha da cana-de-açúcar como fonte de biomassa para a obtenção de açúcares fermentáveis, empregando ozônio com hidratação alcalina e ozônio com hidratação em meio de solventes de baixo ponto eutético (DES). Para a ozonólise foi estudado o efeito do reator (coluna estática e/ou rotatório), tempo e temperatura do tratamento, teor de umidade da biomassa e concentração do ozônio. Para o tratamento de hidratação foram estudados o meio, tempo e a temperatura do processo. Os resultados obtidos demostraram que não houve perdas de holocelulose, pelo contrário, a celulose e hemicelulose aumentaram seu conteúdo em 75 e 42%, respetivamente com a remoção da lignina de até 49%. O tratamento alcalino foi responsável pelas principais mudanças na estrutura química da biomassa, entretanto, o tratamento com ozônio, teve seu efeito principal na hidrólise enzimática, atingindo rendimentos de conversão de 64 e 78% para glicose e xilose, respectivamente. A combinação destes tratamentos deu como resultado a produção de 450 mg g-1 e 150 mg g-1 de glicose e xilose, respetivamente. Além disso, foi encontrado que é possível usar ciclos de ozônio, os quais permitiram atingir a mesma eficiência, mas com uma redução em 80% no consumo. Finalmente, foi estudado o efeito da ozonólise após o tratamento da palha com diferentes misturas de DES. Foram sintetizados e caraterizados DES a partir de cloreto de colina e glicerina como compostos aceptores de hidrogênio e diferentes tipos de ácidos orgânicos (succínico, cítrico, levulínico, lático, oxálico, málico), poliálcoois (sorbitol, glicerina) e ureia como compostos doadores de hidrogênio. Todas as misturas foram sintetizadas pelo método de aquecimento, determinadas suas densidades, viscosidades e caraterizadas por espectroscopia infravermelha e termogravimetria. Para o processo de hidratação foi estudado o efeito do tempo e temperatura. Para os DES que apresentaram os melhores resultados em extração dos acucares fermentáveis foi realizada a aplicação de ozônio.
There is currently a worldwide trend towards using renewable sources in different process such as bioenergy, biofuels and bio-compounds. One of the renewable sources with better projection is the lignocellulosic biomass. However, to increase its value is necessary to carry out the deconstruction of its structure, leading to diminishes of its recalcitrant nature, which can be performed by different methods that enable the extraction of any of its three main components: cellulose, hemicellulose and lignin. Those methods are still under investigation because they are inefficient, with many steps, are economically unfeasible, and/or require high energy consumption. In the last decades, it is also sought that they can be carried according to the principles of green chemistry. In the present study, the use of sugar cane leaf as biomass source in the obtention of fermentable sugars was investigated, employing ozone coupled with hydration alkaline and ozone coupled to hydration with solvents of low eutectic point (DES). For ozonolysis, the reactor effect (fixed bed reactor and/or rotatory), treatment time and temperature, biomass moisture content and ozone concentration were studied. For the hydration treatment the time, temperature of the process and the means were evaluated. The results obtained showed that there was no loss of holocellulose, unlike the cellulose and hemicellulose, which increased their content by 75 and 42 %, respectively, with lignin removal of 49 %. The alkaline treatment was the responsible for the main changes in the chemical structure of lignocellulosic material (LCM), however, the treatment with ozone presented its primary effect on the enzymatic hydrolysis, obtained conversion yields of 64 and 78 % for glucose and xylose, respectively. The combination of both treatments leads to the liberation of 450 mg g-1 and 150 mg g-1 of glucose and xylose, respectively. Additionally, it was found that it is possible to use ozone cycles with the same efficiency, but with an approximately 80% reduction in ozone consumption. Finally, the use of ozone was studied after the pretreatment of the sugar cane leaf with different mixtures of DES. These solvents were synthesized by heating method and choline chloride and glycerin were used as hydrogen acceptor compounds and different types of organic acids (succinic, citric, levulinic, lactic, oxalic, malic), polyalcohols (sorbitol, glycerin) and urea were used as hydrogen donors. The DES were characterized by infrared spectroscopy, thermogravimetry and their density and viscosity were studied. For the hydration process, variations on reaction time and temperature were evaluated and ozone application was performed for the eutectic mixture that presented the best result of lignin extraction.
There is currently a worldwide trend towards using renewable sources in different process such as bioenergy, biofuels and bio-compounds. One of the renewable sources with better projection is the lignocellulosic biomass. However, to increase its value is necessary to carry out the deconstruction of its structure, leading to diminishes of its recalcitrant nature, which can be performed by different methods that enable the extraction of any of its three main components: cellulose, hemicellulose and lignin. Those methods are still under investigation because they are inefficient, with many steps, are economically unfeasible, and/or require high energy consumption. In the last decades, it is also sought that they can be carried according to the principles of green chemistry. In the present study, the use of sugar cane leaf as biomass source in the obtention of fermentable sugars was investigated, employing ozone coupled with hydration alkaline and ozone coupled to hydration with solvents of low eutectic point (DES). For ozonolysis, the reactor effect (fixed bed reactor and/or rotatory), treatment time and temperature, biomass moisture content and ozone concentration were studied. For the hydration treatment the time, temperature of the process and the means were evaluated. The results obtained showed that there was no loss of holocellulose, unlike the cellulose and hemicellulose, which increased their content by 75 and 42 %, respectively, with lignin removal of 49 %. The alkaline treatment was the responsible for the main changes in the chemical structure of lignocellulosic material (LCM), however, the treatment with ozone presented its primary effect on the enzymatic hydrolysis, obtained conversion yields of 64 and 78 % for glucose and xylose, respectively. The combination of both treatments leads to the liberation of 450 mg g-1 and 150 mg g-1 of glucose and xylose, respectively. Additionally, it was found that it is possible to use ozone cycles with the same efficiency, but with an approximately 80% reduction in ozone consumption. Finally, the use of ozone was studied after the pretreatment of the sugar cane leaf with different mixtures of DES. These solvents were synthesized by heating method and choline chloride and glycerin were used as hydrogen acceptor compounds and different types of organic acids (succinic, citric, levulinic, lactic, oxalic, malic), polyalcohols (sorbitol, glycerin) and urea were used as hydrogen donors. The DES were characterized by infrared spectroscopy, thermogravimetry and their density and viscosity were studied. For the hydration process, variations on reaction time and temperature were evaluated and ozone application was performed for the eutectic mixture that presented the best result of lignin extraction.
Descrição
Palavras-chave
Bioenergia, Açúcares fermentáveis, Ozônio, Tratamento alcalino, Etanol de segunda geração, Solventes eutéticos, Bioenergy, Fermentable sugars, Ozonolysis, Alkaline treatment, Second generation ethanol, Deep eutectic solvents