Spectroscopic characterization andthermal decomposition kinetics of 1,3-dibutyl-imidazolium bromide synthesized through a solvent-free and one-pot method

Abstract

Imidazolium-based ionic liquids (ILs), as one of the most popular and investigated classes of ILs owing to their outstanding physicochemical features, find applications in different fields over the last decades. Their thermal stability is of paramount importance for their effective use at elevated temperatures. 1,3-dibutyl-imidazolium bromide ([BBIm][Br] is an interesting IL, which may be employed for different purposes. Nevertheless, its thermal stability and decomposition kinetic are scarce. In the present work, 1,3-dibutyl-imidazolium bromide ([BBIm][Br]) is successfully synthesized through a simple, clean, and efficient solvent-free and one-pot ultrasonic method. Its structure was assessed by DSC, FTIR, Raman spectroscopies, µXRF, one-dimensional (1-D) liquid state 1H, 13C, and 15N NMR. The 2-D NMR analyses thoroughly discussed herein corroborated the structure of the cation as well as the alkyl side chains. Its thermal stability and decomposition kinetic were performed with non-isothermal thermogravimetry analysis at different heating rates. The kinetic triplet was determined using isoconversional kinetic methods. It is revealed that [BBIm][Br] undergoes a single step mass loss in the temperature range of 180–380 °C for which the activation energy is 140 kJ/mol. Furthermore, it is proved that the decomposition mechanism that best represents the experimental data is the nth order (Fn) reaction mechanism