Thermal stability and temperature operating windows of hydrogen sulfate protic ionic liquids

Thermal stability and temperature operating windows of hydrogen sulfate protic ionic liquids Full article

Journal

Thermochimica Acta
ISSN: 1872-762X , E-ISSN: 0040-6031

Output data

Year: 2026, Volume: 766, Article number : 180521, Pages count : 17 DOI: 10.1016/j.tca.2026.180521

Tags

Protic ionic liquids; Hydrogen sulfates; Thermal stability; TGA; DSC; Temperature operating window

Authors

Gainutdinov Bulat R. ¹ , Magsumov Timur I. ¹ , Chumakov Yaroslav E. ¹ , Mirgazieva Elina R. ¹ , Trushkov Igor V. ^1,2 , Sedov Igor A. ¹

Affiliations

1	Chemical Institute, Kazan Federal University, Kremlevskaya Str., 18, Kazan, 420008, Russian Federation
2	N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russian Federation

Hydrogen sulfate protic ionic liquids (PILs) represent a promising class of solvents possessing reactive acidic protons in both the cation and the anion, which can be referred to as biprotic ionic liquids. Their thermal stability is a critical parameter for practical applications, which remains underexplored. Herein, we systematically interrogate the thermal properties of 17 hydrogen sulfate PILs across alkylammonium, imidazolium, and pyridinium families using a combination of TGA, DSC, and long-term isothermal annealing coupled with FTIR spectroscopy. TGA revealed that imidazolium-based PILs exhibited the highest decomposition onset temperatures (up to 619 K), followed by pyridinium salts. In alkylammonium hydrogen sulfates, the thermal stability decreases with increasing cation substitution, but not with increasing alkyl chain length. Long-term stability assessments have shown that dynamic TGA significantly overestimates operational temperatures. Chemical degradation can occur at temperatures up to 120 K lower than those at which rapid mass loss begins. FTIR spectroscopic analysis identified the involvement of acidic protons in both cation and anion in decomposition mechanisms. By integrating melting behavior with long-term stability limits, we determined the temperature operating windows of the studied PILs. Among them, [sBA][HSO4], [MIm][HSO4], and [EIm][HSO4] exhibited the widest windows (208, 198, and 190 K, respectively), combining low melting temperatures (283–314 K) with high thermal stability. The results provide essential benchmarks for selecting the most appropriate PIL candidates for high-temperature applications.

Gainutdinov B.R. , Magsumov T.I. , Chumakov Y.E. , Mirgazieva E.R. , Trushkov I.V. , Sedov I.A.
Thermal stability and temperature operating windows of hydrogen sulfate protic ionic liquids
Thermochimica Acta. 2026. V.766. 180521 :1-17. DOI: 10.1016/j.tca.2026.180521

Submitted:	Jul 31, 2026
Accepted:	Oct 14, 2026
Published online:	Oct 16, 2026

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