Application-Related Consideration of the Thermal Stability of [mTBDH][OAc] Compared to Amidine-Based Ionic Liquids in the Presence of Various Amounts of Water

Abstract

The hydrolysis kinetics of 7-methyl-1,5,7triazabicyclo[4.4.0]dec-5-enium acetate [mTBDH][OAc] was investigated in a comprehensive study by the utilization of the well-known Schlenk technique to achieve a better understanding of its stability for dry-jet wet spinning applications (e.g., Ioncell) and due to the course of operation for recovery methods like fractional distillation. Decomposition behavior as a function of temperature, time, acid−base stoichiometry, and water content was extensively analyzed and characterized by nuclear magnetic resonance spectroscopy (NMR), capillary electrophoresis (CE), and thermogravimetric analysis (TGA). Furthermore, kinetic models were formulated for the prediction of the stability and the results were compared with the closely related amidine-based analogues 1,5diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] and 1,8-diazabicyclo[5.4.0]undec-7-enium acetate [DBUH][OAc].

Thermal, chemical, electrochemical, radiolytic and biological stability of ionic liquids and deep eutectic solvents

“…18). 81 3.1.13 Flammability (flammable), flash point, combustibility (combustible), fire safety, ignition, explosion, hypergolicity (hypergolic) and energetics of ILs. Flammability, combustion, ignition and explosion are signs of chemical instability.…”

“…Fig. 18 Effect of water content (a), anion/cation mole ratio (b), cation type (c) and temperature (d) on the hydrolysis rate of superbase-based IL cation 81. …”

Enabling Sustainable Chemistry with Ionic Liquids and Deep Eutectic Solvents: A Fad or the Future?

“…The decomposition kinetics of [mTBDH] depends on the amount of water and acetic acid present in the environment. At 95 °C, a small amount of water promotes the decomposition of [mTBDH], whereas high amounts or super‐stoichiometric amounts of acetic acid stabilize it [26] . Further, the decomposition activation energy depends on the structure of the constituents in the IL.…”

Enabling Sustainable Chemistry with Ionic Liquids and Deep Eutectic Solvents: A Fad or the Future?

“…At 95 °C, a small amount of water promotes the decomposition of [mTBDH], whereas high amounts or super-stoichiometric amounts of acetic acid stabilize it. [26] Further, the decomposition activation energy depends on the structure of the constituents in the IL. In a series of imidazolium ILs, the length of the alkyl side chain and the number of fluorine atoms in the cation were found to impact thermal stability, with longer alkyl side chains and a lower number of fluorine atoms enhancing thermal stability in the liquid state.…”

“…Nevertheless, many decompose under similar conditions as exemplified by the amidine IL, 7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐enium acetate ([mTBDH][OAc]), which decomposes under inert atmosphere at elevated temperature (Figure 3). [26] Also, imidazolium ILs are prone to decomposition, yielding alkyl imidazoles, alkyl chlorides, hydrogen chloride, and alkenes (Figure 3). [27] Density functional theory calculations suggest that environmental polarity influences the kinetics and thermodynamics of the decomposition [28] .…”