(18g) Amino Acid-Based Functionalized Deep Eutetuc Solvents As a Promising Alternative for Efficient CO2 Capture and Consideration of Its Application

Global warming, a phenomenon characterized by the long-term increase in Earth's average temperature, has become one of the most pressing challenges of the ₂1st century. The primary driver of global warming is the increase in greenhouse gas emissions, particularly carbon dioxide (CO₂), resulting from human activities such as fossil fuel combustion, deforestation, and industrial processes. CO₂ is a potent greenhouse gas, capable of trapping heat in the Earth's atmosphere, leading to a gradual rise in global temperatures. This temperature rise has far-reaching consequences for our planet, affecting ecosystems, weather patterns, and sea levels, among other aspects of the environment.

The impacts of global warming are already apparent and are predicted to worsen if greenhouse gas emissions continue unabated. Glaciers and ice caps are melting at unprecedented rates, causing sea levels to rise and putting coastal communities at risk. Extreme weather events, such as hurricanes, heatwaves, and droughts, are becoming more frequent and severe. These consequences not only threaten the natural world but also have profound implications for human societies, as they disrupt agriculture, water resources, and infrastructure, exacerbating global inequality and instability.

Addressing the issue of global warming necessitates the urgent reduction of CO₂ emissions. This reduction can be achieved through a combination of strategies, such as transitioning to renewable energy sources, enhancing energy efficiency, and promoting sustainable land use practices. Another crucial component in combating climate change is the development and implementation of effective carbon capture technologies. These technologies aim to remove CO₂ from the atmosphere or capture it at the source, preventing its release into the atmosphere and mitigating the greenhouse effect. As the threat of global warming becomes increasingly dire, the need for innovative, efficient, and cost-effective carbon capture solutions is more critical than ever.

Alkanolamine absorbers are a widely-used technology for capturing carbon dioxide (CO₂) from various gas streams, including those produced by power plants, natural gas processing facilities, and other industrial processes. These absorbers leverage the chemical properties of alkanolamines to selectively remove CO₂ from gas mixtures, contributing to the mitigation of greenhouse gas emissions and helping combat climate change. Alkanolamine absorbers, also known as amine scrubbers or amine gas treating systems, utilize alkanolamines as chemical absorbents to capture CO₂. Alkanolamines are a class of organic compounds that contain both an alcohol (-OH) and an amine (-NH₂) functional group. The most commonly used alkanolamines in CO₂ absorption processes are monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA).

Alkanolamine absorbers can be used to treat gas streams in various chemical processes, reducing CO₂ emissions and meeting environmental regulations. Despite their widespread use, alkanolamine absorbers face several challenges. The regeneration of alkanolamine solutions demands significant amounts of heat, increasing the overall energy consumption and cost of the CO₂ capture process. Also, Alkanolamine solutions can be corrosive to equipment, necessitating the use of corrosion-resistant materials or coatings, which may increase the capital and maintenance costs.

The development of innovative and efficient carbon capture technologies has become a crucial area of research. In this context, ionic liquids have emerged as a potential game-changer for CO₂ capture, offering several advantages over traditional absorption technologies. The unique properties of ionic liquids that make them suitable for CO₂ capture include low volatility. Due to their ionic nature, ionic liquids have negligible vapor pressure, which minimizes the risk of evaporative losses during the capture process and reduces the release of potentially harmful volatile organic compounds (VOCs). Also, Ionic liquids exhibit excellent thermal stability, allowing them to operate over a wide temperature range without undergoing degradation. This property is particularly beneficial for CO₂ capture processes that involve high temperatures.

However, The synthesis of ionic liquids often involves expensive starting materials and complex procedures, which can limit their economic viability for large-scale CO₂ capture applications. And Many ionic liquids exhibit high viscosity, which can impede mass transfer during the CO₂ absorption process, reducing the overall efficiency of the capture system. High viscosity can also lead to increased energy consumption for pumping and mixing, further affecting the economic feasibility of ionic liquids for CO₂ capture. Although ionic liquids have been shown to possess high thermal stability, their long-term stability and performance under continuous operation conditions remain relatively unexplored.

So, research on new carbon dioxide absorbents continued, and that's how DES(Deep Eutectic Solvent) started. DESs are a unique class of solvents formed by the combination of two or more components, typically a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). DESs have a lower melting point than either of their individual components, which results from the strong hydrogen bonding between the HBD and HBA. And DESs are known for their excellent thermal and chemical stability, enabling their use in a wide range of applications, including those involving high temperatures or harsh chemical conditions.

Further research has been conducted on the use and combination of materials that can further increase the absorption capacity of DES, and this study aims to use an amino acid-based hydrogen bond acceptor (HBA) as a functional group to improve the CO₂ absorption characteristics of DES.

The study utilized two amino acids, glycine (GLY) and proline (PRO), as HBAs, and alkanolamines, including monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA), as hydrogen bond donors (HBDs). The results revealed that the functionalized DESs showed a higher CO₂ absorption capacity and a faster reaction rate than conventional absorbents.

Functionalizing DESs with amino acids offers several advantages. First, amino acids are readily available and cost-effective. Second, the conversion of amino acids into amino acid salts is a simple and efficient process. Third, the resulting amino acid-based HBAs offer additional sites for CO₂ absorption, leading to an improved absorption capacity. Fourth, the enhanced intermolecular interactions resulting from the amino acid-based HBAs promote the formation of stable DESs, which can lead to a more efficient capture of CO₂.

The findings of this study are significant for the development of more effective carbon capture technologies. By enhancing the absorption capacity and reaction rate of DESs, these functionalized materials can reduce the cost and energy required for capturing CO₂. Additionally, the low vapor pressure of DESs makes them a safer alternative to conventional absorbents that can be highly volatile and flammable. Lastly, the use of amino acids as HBAs offers an opportunity to design DESs with customized absorption characteristics.

In conclusion, this study highlights the potential of functionalized DESs for improving the efficiency of CO₂ capture. The use of amino acid-based HBAs provides an effective means of enhancing the absorption capacity and reaction rate of DESs. These functionalized materials could be used as an alternative to conventional absorbents for capturing CO₂, leading to more efficient and cost-effective carbon capture technologies.

The DES manufactured in this way has a disadvantage in that it is applied only in the corresponding process as a wet absorbent. In order to compensate for this, it is possible to improve the usability through a pretreatment process such as impregnation of the porous material and membrane, and at the same time to create a better absorbent than commercial carbon dioxide absorption capacity.