Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2022
Thesis Language: Turkish
Student: MERVE GÖRDESEL YILDIZ
Principal Supervisor (For Co-Supervisor Theses): Özkan Murat Doğan
Co-Supervisor: Duygu Uysal
Abstract:
In this thesis, hydrogen production was carried out from glycerol by electrochemical reforming method. Hydrogen production from glycerol, a by-product of biodiesel, is a promising approach due to its integration into the biorefinery process. In terms of waste management and energy consumption, glycerol electrochemical reforming is a good alternative to water electrolysis. In the study, the performance of the system was evaluated under different operating conditions with the parameter studies carried out on five different systems, and the most suitable operating conditions for glycerol electro-oxidation were determined. In the experiments carried out in the basic electrolysis cell, the current density values with the electrical potential applications under different conditions were recorded. The current density values were associated with the formation of H2. In the study, glycerol concentration was determined as 0.4 M and electrolyte concentration as 0.04 M H2SO4. In the light of the results obtained from the basic electrolysis cell experiments, quantitative and qualitative analysis of the gas products was carried out in Hoffman electrolysis cell. By working with CV method in the three-electrode system, voltammetric behaviors were recorded and specific peaks for glycerol electro-oxidation were determined. In addition, the total reaction rate expression was developed using the Tafel curve. Due to the constraints in the basic electrolysis cell, the experiments were continued in a two-compartment electrolysis cell, which has different types of solution feeding diversity and anode-cathode compartments can be separated from each other by membrane. Experiments were carried out in the form of instantaneous potential-current density measurements, long-term performance tests and GC gas analyses. At this stage of the study, the membrane and the pretreatment effect applied to the membrane were determined. Room temperature and 2 V constant potential were determined as the most suitable conditions. AAS analyses supported this result. According to long-term performance experiments, performance decrease was observed due to the consumption of glycerol during the experiment. FTIR analysis confirmed this result. In order to improve this situation, system was operated as a continuous solution feed and 35% increase in current density values was achieved. Due to constraints such as the inability to use MEA in the two-compartment electrolysis cell, the cubic electrolysis cell, which is the final experimental system, has been used. The highest current density was obtained by using a nozzle type copper current collector and MEA loaded with 5.7 mg/cm2 10% Pt/C (0.57 mg/cm2 Pt) for the cathode and 5 mg/cm2 Zn for the anode. The results obtained with this study contributed to the development of glycerol electrochemical reforming which is still in its beggining in terms of technological development and industrial integration. With system improvement and parameter studies, the most suitable conditions for glycerol electrochemical reforming were determined and hydrogen production was increased.
| Key Words : Hydrogen, glycerol, |