Thermal Stability and Kinetic of Decomposition of Mono- and Dicationic Imidazolium-Based Ionic Liquids

Caroline Bender,Clarissa Frizzo,Bruna Kuhn,Francieli Ziembowicz,Carla Farias,Thaíssa Beck

doi:10.21577/0103-5053.20190114

Abstract

Phase transitions, thermal stability, thermokinetics and activation parameters of degradation reaction of the dicationic ionic liquids (ILs), 1,n-bis(3-methylimidazolium-1-yl)alkane ([BisAlk(MIM)2][2Br]) and monocationic ILs, 1-(3-methylimidazolium-1-yl)alkane ([Alk(MIM)][Br]), where Alk = Dec, DoDec, TetDec, (decane, dodecane, tetradecane) were evaluated. The influence of an additional cationic head and the alkyl chain length in thermal parameters were also evaluated. The dicationic ILs are more stable than monocationic and thermal degradation of ILs mono- and dicationic did not show linear dependence on the alkyl chain length. Thermokinetic parameters indicated degradation in multiple steps. The monocationic ILs showed a more persistent crystalline phase than dicationic IL, which became totally amorphous after heating. The estimate temperature decomposition, activation energy and thermal transitions enable the determination of which types of ILs are applicable for specific purposes, such as lubricants or solvents at high temperatures, while maintaining ILs physical and chemical properties.

Highlights

Ionic liquids (ILs) are structures broadly defined as organic salts with low melting points that have provoked interest due to their large thermal stability.[1,2] Depending of the cation and anion combination, ionic liquids (ILs) may exhibit different physicochemical properties when compared with conventional electrolytes media or organic solvents.[3,4,5] Properties such as high thermal stability, tunable electrochemical window, low flammability, broad liquid range, and ability to dissolve and stabilize a wide range of materials allow ILs to be used in engineered materials synthesis
The decomposition profile and correlated data were first carried out using a thermogravimetric analysis (TGA) measurement at a heating rate of 283.15 min-1 for each ionic liquid
The the onset temperature of decomposition (Tonset) shows that no thermal degradation, based on mass loss, occurs at temperatures below 528 K

Summary

Introduction

Ionic liquids (ILs) are structures broadly defined as organic salts with low melting points that have provoked interest due to their large thermal stability.[1,2] Depending of the cation and anion combination, ILs may exhibit different physicochemical properties when compared with conventional electrolytes media or organic solvents.[3,4,5] Properties such as high thermal stability, tunable electrochemical window, low flammability, broad liquid range, and ability to dissolve and stabilize a wide range of materials allow ILs to be used in engineered materials synthesis.

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Conclusion