(2ic) Role of New Class Functionalized Ionic Liquids for Enhancement of CO2 Capturing Performance of N-Methyldiethanolamine: Kinetics Study and Interaction Mechanism Analysis

An increasing concentration of greenhouse gases, in this context, carbon dioxide, is a sure contributor to this global warming. The majority of the CO₂ emissions into the atmosphere are from various industries dealing with fossil fuel resources. Basically, absorption, adsorption, cryogenic separation, and membrane separation are the major technologies used for CO₂ capture. Typically, chemical absorption technology is one of the best suitable technologies to capture at a high rate. The role of absorbent is crucial in the chemical absorption process, and mainly five chemical groups are utilized as absorbent: ammonia, alkanolamines, amino acids, alkali metal carbonates, and ionic liquids. Generally, these absorbents are used as an aqueous form to reduce the economy of the process as water is the cheapest solvent. Industrially, an aqueous solution of primary, secondary, and tertiary alkanolamines are most widely used as these are cheaper and provide good CO₂ loading ability. However, the primary and secondary alkanolamines have several drawbacks: high volatility, heat-stable salt formation, high regeneration cost, and corrosiveness. Interestingly, tertiary alkanolamines overcome these limitations, especially N-methyldiethanolamine (MDEA). The major limitation of MDEA is the low absorption rate; therefore, various promoters (having a potential of high absorption rate) have been blended with MDEA to enhance the absorption performance, such as Piperazine (Pz), Monoethanolamine (MEA), and diethanolamine (DEA). However, these promoters belong to are primary and secondary alkanolamines groups; hence the limitations are the same as aforementioned for alkanolamines. Therefore, we need to find an energy-efficient and high thermal stable new promoter to consider these limitations. Therefore, new class promoters need to be used to overcome these issues. Functionalized ionic liquids (FILs) have the potential to overcome these limitations. Hence, in this work, four different new class functionalized ionic liquids (FILs) were used as promoters and determined their effectivity toward enhancement of the CO₂ absorption performance. The CO2 absorption is performed at different pressure (2 bar, 4.4 bar, and 7 bar) and different temperature (303, 313, 323, and 328 K). The results confirmed that CO₂ loading increases around 18 to 22% after 5wt% FILs blended in the MDEA. It was noticed that the CO₂ loading increases with increasing pressure and decreases with increasing temperature, for all absorbents systems. Further, the absorption kinetics was determined, and results showed that all the FILs provide an excellent absorption rate enhancement. Additionally, for the interaction mechanism study, ¹³C NMR analysis was performed for the blend aqueous MDEA-CO₂ system. The results suggested that the FILs blend MDEA system produced a high amount of carbamates and bicarbonates during CO₂ absorption, which further decreases with increasing temperature. Eventually, regeneration energy was calculated, and results confirmed that the energy heat duty penalty was lower in the [TETAH][Im] blend MDEA system. Overall, [TETAH][Pz], [TETAH][Im], [DETAH][Im] and [DETAH][Tz] showed the promising ability as promoters to enhance CO₂ capturing performance of MDEA.