Comparison of two pre-treatment methods for the chemocatalytical conversion of fibre sludge to lactic acid : Alkaline versus acidic mechanocatalytical pre-treatment for cellulosic feedstock depolymerisation
Knabl, Magdalena (2019)
2019
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2019061717117
https://urn.fi/URN:NBN:fi:amk-2019061717117
Tiivistelmä
The synthesis of valuable chemicals from lignocellulosic biomass is a promising approach to develop the chemical industry in a more sustainable and environmentally friendly way. Following this statement, during this thesis, fibre sludge, a cellulosic residue from the pulp and paper industry, was utilized as feedstock for the production of lactic acid. Lactic acid is an important platform chemical, with possible applications in different industries and in the production of biodegradable plastics, green solvents and many other valuable compounds.
During the practical work of this thesis, two mechanocatalytical pre-treatments in a ball-mill have been performed to depolymerise the cellulosic fibre sludge and make the carbohydrates accessible for further conversion. Besides the, already by other researchers studied, acid-catalysed ball-milling, different bases with respective concentrations are tested as milling catalysts. The aim was the comparison of these two pre-treatment methods. The conversion to lactic acid was performed with 0.5 g specimen of this processed fibre sludge, in 3 mL water at 180 °C for 2 h. During the conversion three different types and concentrations of a base catalyst were tested and additionally also a Lewis acid metal salt catalyst. The alkali conversion conditions originated from the basic milling catalysts directly and the acidic pre-treated samples were neutralized and adjusted respectively. The sample analysis was performed with High-Performance Liquid Chromatograph comprising an Ultraviolet-Visible Spectrometer as detector.
The thereby gained results allow only an estimated discussion and conclusion. The acid-catalysed ball-milling resulted in water-soluble sugars that could be readily converted to lactic acid, nevertheless with low yields (maximum yield = 2.28 %) under the applied conditions. The conversion of the base-catalysed ball-milled fibre sludge did not show improved lactic acid yields when compared to the results generated from fibre sludge that has been milled without catalyst. Apart from the conclusion that the acidic mechanocatalytic pre-treatment depolymerised the cellulose better than the basic one, no further conclusions could be made, due to the non-ideal analysis method. Therefore, the main goal for future research would be the development of a suitable analysis method. Then, the practical approach of this thesis could be researched more reliable and be systematically developed.
During the practical work of this thesis, two mechanocatalytical pre-treatments in a ball-mill have been performed to depolymerise the cellulosic fibre sludge and make the carbohydrates accessible for further conversion. Besides the, already by other researchers studied, acid-catalysed ball-milling, different bases with respective concentrations are tested as milling catalysts. The aim was the comparison of these two pre-treatment methods. The conversion to lactic acid was performed with 0.5 g specimen of this processed fibre sludge, in 3 mL water at 180 °C for 2 h. During the conversion three different types and concentrations of a base catalyst were tested and additionally also a Lewis acid metal salt catalyst. The alkali conversion conditions originated from the basic milling catalysts directly and the acidic pre-treated samples were neutralized and adjusted respectively. The sample analysis was performed with High-Performance Liquid Chromatograph comprising an Ultraviolet-Visible Spectrometer as detector.
The thereby gained results allow only an estimated discussion and conclusion. The acid-catalysed ball-milling resulted in water-soluble sugars that could be readily converted to lactic acid, nevertheless with low yields (maximum yield = 2.28 %) under the applied conditions. The conversion of the base-catalysed ball-milled fibre sludge did not show improved lactic acid yields when compared to the results generated from fibre sludge that has been milled without catalyst. Apart from the conclusion that the acidic mechanocatalytic pre-treatment depolymerised the cellulose better than the basic one, no further conclusions could be made, due to the non-ideal analysis method. Therefore, the main goal for future research would be the development of a suitable analysis method. Then, the practical approach of this thesis could be researched more reliable and be systematically developed.