Thermal stability of choline based amino acid ionic liquids

Thermal Stability of Ionic Liquids: Current Status and Prospects for Future Development

“…The same results are obtained for some 3,5-dimethylpyrazolum ILs and some paramagnetic ILs [108,109]. In the study of amino acid ILs, [N1,1,14,2O12][Lys] with the longchain alkyl group on the side of nitrogen has higher thermal stability than [N1,1,6,2O12][Lys] under the isothermal condition, while both longer and shorter alkyl side chains harm the thermal stability under the non-isothermal condition [77]. The influence of alkyl chain length on thermal stability can be explained as follows:…”

“…Moreover, ether in alkyl side chains is favorable for thermal decomposition. As the number of introduced ether increases, the thermal stability tends to decrease [66,[114][115][116] because the introduction of oxygen atoms weakens the interaction between the cation and anion [77,115]. Specifically, Figure 14 demonstrates that the oxygen atom at the β-position significantly decreases the thermal stability of ILs, which can be explained by retroalkylation of piperidinium ILs into 1-methyl piperidine and the corresponding oxocarbenium ion intermediates at elevated temperature [117].…”

“…To establish the correlation between the operating temperature and time, it is necessary to investigate the long-term thermal stability of ILs through isothermal TGA [36,75,76]. In this method, samples are heated at a fixed temperature varying from an hour to tens of hours, then Tz/y is determined [49,57,[77][78][79]. As shown in Figure 3, more than three temperatures are usually used in the analysis [75,78], and the interval between different temperatures is determined by Tonset [74].…”

“…1) Increasing the alkyl chain length weakens the bond between the alkyl chain and the cation such as imidazolium and ammonium, making it more vulnerable to attack and therefore more readily thermally decomposed [53,106]; 2) Carbocations and carbon radicals with longer alkyl chains are more stable and easier to leave on heating, and thus ILs with longer alkyl chains favor the decomposition phenomenon [72]; 3) For choline based amino acid ILs, longer alkyl chains on cation create strong hydrophobic interaction with gradually decreased hydrogen bond interaction due to bulkier cationic size. Upon decreasing alkyl chain length, the reverse effect renders lowering the overall thermal stability of the ILs [77].…”

Encapsulated Amino‐Acid‐Based Ionic Liquids for CO2 Capture

“…Task‐specific ionic liquids (TILs), amino acid‐functionalized ILs, IL‐mixed solvents and eutectic solvents, are promising materials for this purpose. Within chemisorption driven solvents, those based on amino acids stand out due to their low cost, abundant availability, easy synthesis and low toxicity and biodegradability , , . However, the use of chemisorption driven solvents present several drawbacks, such as corrosivity, high viscosity of the products resultant from the chemical reaction(s), solvent loss and the high energy requirement for the regeneration processes, leading to high operational costs and ultimately leading to uneconomical, and sometimes technical unfeasible, processes.…”