Thermal decomposition kinetics and mechanisms of long alkyl chain ionic liquids with carboxylate anions

Abstract

This work presents the synthesis and analysis of the thermal decomposition kinetics and mechanisms of long alkyl chain ionic liquids (ILs) with cations 1-decyl-3-methylimidazolinium ([C10MIM]+), 1-dodecyl-3-methylimidazolinium ([C12MIM]+), and 1-hexadecyl-3-methylimidazolinium ([C16MIM]+) and butanoate ([C3COO]−) and heptanoate ([C6COO]−) anions. The kinetics analysis was performed using the Kissinger-Akahira-Sunose isoconversional methodology. The results indicated that the carboxylate ILs are less thermally stable than their bromide analogues and the order of thermal stability was explained by the values of the kinetic parameters (Ea and lnA) and their variation with α. For most of the studied carboxylate ILs there was a considerable variation in Ea as the decomposition progressed, indicating multiple decomposition steps. The thermal decomposition mechanism was studied by analyzing the thermal degradation residue from 1H NMR spectroscopy.