Publicação
Scale-up of an electrocatalytic unit for lignin depolymerization
| Resumo: | Oil dependency is pointed out as one of the main vulnerabilities inherent to the 21st century’s society. In the transportation field, electric vehicles and new forms of fuel such as hydrogen, are being developed. However, in the manufacturing field no incumbent progress has been made to replace petrochemicals. In this research for petroleum alternatives, lignocellulosic materials with particular emphasis on lignin, have been highlighted as candidates. Lignin is an abundant polymer from the pulp and paper industries with a structure that enables the extraction of interesting chemical platforms. Despite this potential, the lack of efficiency in its processing through depolymerization hinders its industrial adoption. In this realm of developing efficient green technologies to depolymerize lignin an electrochemical approach has been highlighted, with few papers already published. However, the focus of these papers lies on achieving the desired product at beaker scale and not in an industrial implementation. To bridge this gap the present thesis focused on the implementation and subsequent scale-up of an electrocatalytic system aimed to depolymerize lignin with obtention of monomeric products. The scale-up process was based on Pi-Buckingham theorem. The project started with the design of a small system, able to depolymerize 100 ml of a lignin solution. Based on the bench studies that were being carried out simultaneously, the electrodes chosen were a titanium anode with a ruthenium layer deposited, through an electrodeposition process, with the cathode used being a nickel electrode. Due to the differences in size between the bench tests’ electrodes and the ones used in the system, different electrodeposition times were tested to assess monomers/oligomers’ (MM< 500g/mol) formation during the depolymerization process, carried with a voltage appliance of 2.5V. After analysis of the HPLC results, from the depolymerization carried out, it was possible to conclude that electrodes subjected to the same depolymerization time of the bench test electrode (300 seconds) were not effectively able to produce monomers/oligomers. The electrodes electrodeposited for 600 and 1200 seconds were able to produce monomers/oligomers and were the ones used in further experiments. The electrodes were named as Ru-Ti followed by the order in which they were produced in between their electrodeposition time group, for example Ru-Ti_1st_600sec, with this electrode being the first one to be produced from the 600 second group. Chronoamperometric tests were carried out to evaluate the electrode’s oxidative capacity, assessing the stability and determining a coefficient that was named transport coefficient. It was possible to verify that the electrode Ru-Ti_1st_1200sec had a peak current value in all steps twice as higher when compared to Ru-Ti_3rd_600sec, but a similar value for the transport coefficient. When a comparison between electrodes with the same electrodeposition times was performed it was verified that the electrode without usage had a 2 times higher current peak and a mass transport value 2 orders of magnitude higher. With these tests was also possible to verify that the equilibrium potential of the reaction was 1.75V. To determine the efficiency of the process an analysis of the HPLC graphs was performed. The time taken until monomers/oligomers’ detection was directly pointed out and lignin depolymerization rate was determined through a new method based in the peak integration of the graphs. In the presence of a 1% solution the results showed that the electrode with higher amount of ruthenium, Ru-Ti_1st_1200sec had a 2.5 higher depolymerization rate when compared with Ru-Ti_3rd_600sec, being this reflected on the capacity to produce monomers/oligomers with a monomers/oligomers’ peak emerging between 7 and 9 hours in the tests performed with the first electrode but only after 24 hours with the second electrode. The results obtained for the 8% solution were not quantifiable due to the lack of accuracy of the method. It was also possible to conclude that an inactivation of the electrode occurs during the depolymerization process with the electrode Ru-Ti_1st_600sec, having a 1.5 lower rate when compared with Ru-Ti_3rd_600sec. During the depolymerization process the analysis of the current evolution with time enabled to affirm that the initial value is higher for the electrode with higher electrodeposition time, followed by the new electrode with an electrodeposition time of 600 seconds. Two other important factors are that this current constantly lowers with time to an approximate value of 0 A and that the 8% solutions have lower currents for all the electrodes tested with higher time needed until identification of the monomeric peaks. Regarding the dimensionless numbers’ determination, experiments to determine essential parameters as viscosity, density and flowrate were performed. Not all dimensionless numbers were determined and a first estimative for the flow rate was based on geometric similarity, with the value obtained pointing to both cells having the same operating flowrate, 1,40E-06 m3/s. After determination of all dimensionless numbers the flowrate will be optimized to obtain the smallest difference between all the values determined. |
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| Autores principais: | Mendes, João Manuel Silva |
| Assunto: | Lignin Electrocatalysis Ruthenium Electrodeposition Electrodes Chronoamperometry Depolymerization |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Instituto Politécnico do Porto |
| Idioma: | inglês |
| Origem: | Repositório Científico do Instituto Politécnico do Porto |
| Resumo: | Oil dependency is pointed out as one of the main vulnerabilities inherent to the 21st century’s society. In the transportation field, electric vehicles and new forms of fuel such as hydrogen, are being developed. However, in the manufacturing field no incumbent progress has been made to replace petrochemicals. In this research for petroleum alternatives, lignocellulosic materials with particular emphasis on lignin, have been highlighted as candidates. Lignin is an abundant polymer from the pulp and paper industries with a structure that enables the extraction of interesting chemical platforms. Despite this potential, the lack of efficiency in its processing through depolymerization hinders its industrial adoption. In this realm of developing efficient green technologies to depolymerize lignin an electrochemical approach has been highlighted, with few papers already published. However, the focus of these papers lies on achieving the desired product at beaker scale and not in an industrial implementation. To bridge this gap the present thesis focused on the implementation and subsequent scale-up of an electrocatalytic system aimed to depolymerize lignin with obtention of monomeric products. The scale-up process was based on Pi-Buckingham theorem. The project started with the design of a small system, able to depolymerize 100 ml of a lignin solution. Based on the bench studies that were being carried out simultaneously, the electrodes chosen were a titanium anode with a ruthenium layer deposited, through an electrodeposition process, with the cathode used being a nickel electrode. Due to the differences in size between the bench tests’ electrodes and the ones used in the system, different electrodeposition times were tested to assess monomers/oligomers’ (MM< 500g/mol) formation during the depolymerization process, carried with a voltage appliance of 2.5V. After analysis of the HPLC results, from the depolymerization carried out, it was possible to conclude that electrodes subjected to the same depolymerization time of the bench test electrode (300 seconds) were not effectively able to produce monomers/oligomers. The electrodes electrodeposited for 600 and 1200 seconds were able to produce monomers/oligomers and were the ones used in further experiments. The electrodes were named as Ru-Ti followed by the order in which they were produced in between their electrodeposition time group, for example Ru-Ti_1st_600sec, with this electrode being the first one to be produced from the 600 second group. Chronoamperometric tests were carried out to evaluate the electrode’s oxidative capacity, assessing the stability and determining a coefficient that was named transport coefficient. It was possible to verify that the electrode Ru-Ti_1st_1200sec had a peak current value in all steps twice as higher when compared to Ru-Ti_3rd_600sec, but a similar value for the transport coefficient. When a comparison between electrodes with the same electrodeposition times was performed it was verified that the electrode without usage had a 2 times higher current peak and a mass transport value 2 orders of magnitude higher. With these tests was also possible to verify that the equilibrium potential of the reaction was 1.75V. To determine the efficiency of the process an analysis of the HPLC graphs was performed. The time taken until monomers/oligomers’ detection was directly pointed out and lignin depolymerization rate was determined through a new method based in the peak integration of the graphs. In the presence of a 1% solution the results showed that the electrode with higher amount of ruthenium, Ru-Ti_1st_1200sec had a 2.5 higher depolymerization rate when compared with Ru-Ti_3rd_600sec, being this reflected on the capacity to produce monomers/oligomers with a monomers/oligomers’ peak emerging between 7 and 9 hours in the tests performed with the first electrode but only after 24 hours with the second electrode. The results obtained for the 8% solution were not quantifiable due to the lack of accuracy of the method. It was also possible to conclude that an inactivation of the electrode occurs during the depolymerization process with the electrode Ru-Ti_1st_600sec, having a 1.5 lower rate when compared with Ru-Ti_3rd_600sec. During the depolymerization process the analysis of the current evolution with time enabled to affirm that the initial value is higher for the electrode with higher electrodeposition time, followed by the new electrode with an electrodeposition time of 600 seconds. Two other important factors are that this current constantly lowers with time to an approximate value of 0 A and that the 8% solutions have lower currents for all the electrodes tested with higher time needed until identification of the monomeric peaks. Regarding the dimensionless numbers’ determination, experiments to determine essential parameters as viscosity, density and flowrate were performed. Not all dimensionless numbers were determined and a first estimative for the flow rate was based on geometric similarity, with the value obtained pointing to both cells having the same operating flowrate, 1,40E-06 m3/s. After determination of all dimensionless numbers the flowrate will be optimized to obtain the smallest difference between all the values determined. |
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