Recently, CO2 electrochemical reduction (CO2R) has gained popularity, to cope with the strict environmental rules on greenhouse gas emissions, and to convert CO2 to value-added chemicals/fuels. Ionic liquids (ILs) have been considered as potential media for CO2R owing to their multi-functions in enhancing CO2R solubility and improving CO2R reaction rate and product selectivity. To date, there have been many studies related to CO2R in IL-based systems, which primarily focused on fundamental research to offer findings about CO2R performance and reaction mechanisms, and one article focused on evaluating the economic potential of the stand-alone CO2R process without considering the upstream process or integrating into other processes. In fact, the integration of CO2R with upstream or other production processes will make the evaluation more practically significant, and thus deeper knowledge about the viability of the integrated CO2R process is needed, but relevant work is still lacking. Meanwhile, how to further improve the performance of CO2R is another concern. The goal of this work is to perform systematic studies on techno-economic assessment of the integrated CO2R process and experimental research for producing methanol (CH3OH) with ILsas electrolytes as the focus, since CH3OH is an important solvent, energy and hydrogen carrier, and feedstock. In the first part, an intensive literature survey was conducted to summarize the research progress, identify the state-of-the-art and provide the research gap for CO2R in the IL-based systems. It shows that the multi-functions as CO2 absorbents, reaction media, and co-catalysts give ILs a distinctive boosting effect on the CO2R performance. But now the research mainly focused on lab-scale experimental studies, while the viability of this technique on a large scale is unclear. In the second part, stand-alone CO2R producing CH3OH with IL as the absorbent and electrolyte was studied and then further integrated with biomass gasification. The economic feasibility and environmental impact were investigated and compared, under current and future conditions. Stand-alone CO2R process shows high total production cost (TPC) due to the high electrolyzer and electricity costs. The TPC could reduce from 1.44 to 1.02 €/kg-CH3OH under the current conditions after integration. Additionally, based on the analysis, electricity for CO2R is the main part of energy usage and dominates the CO2 emission of the integrated process. In the third part, techno-economic analysis of the integrated processes that combined CO2R in IL to produce CO, syngas, and CH3OH with biomass gasification for producing CH3OH was performed and contrasted with stand-alone biomass gasification and CO2R processes. The process that integrated with CO2R to CO was identified as the optimal pathway with the lowest TPC of 0.38 €/kg-CH3OH under the current condition. Sensitivity analysis confirmed that electricity and H2 prices are two key parameters influencing the TPC of the process, which is combined with CO2R to CO followed by hydrogenation to CH3OH; while for the integrated processes with CO2R to syngas and CH3OH, simultaneously reducing stack and electricity prices as well as improving CO2R performance are significant to make these processes viable in the future. In the fourth part, preliminary experimental research on CO2R to CH3OH with various catalysts in IL-based electrolytes was conducted to evaluate the influence of catalysts and ILs on the CO2R performance. It was found that CO2R to CH3OH by using copper-deposited nickel foam (CuNi) showed the optimal performance with current density and Faradic efficiency of CH3OH of 14 mA/cm2 and 46.31% under -1.7 V vs Ag/Ag+, respectively.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-93716 |
| Date | January 2022 |
| Creators | Li, Fangfang |
| Publisher | Luleå tekniska universitet, Energivetenskap, Luleå |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Licentiate thesis / Luleå University of Technology, 1402-1757 |
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