Isoconversional kinetic analysis applied to five phosphonium cation-based ionic liquids

Abstract

Thermal degradation of five phosphonium cation-based ionic liquids ([P 66614 outperforming the other ones in both pyrolytic and oxidising conditions. Although the thermal degradation mechanism is affected by atmospheric conditions, the degradation trend remains practically constant. As the dynamic methodology usually overestimates the long-term thermal stability, an isoconversional methodology is better for predicting the long-term thermal stability of these ionic liquids in order to be used as base oil or additive in lubricants formulation. Finally, the model-free methodology can predict at lower costs the ILs performance in isothermal conditions. Highlights• Weakly coordinating anions provoke good thermal stability of ILs.• • Isoconversional methods are better than dynamic ones for long-term thermal studies.• Activation energy behavior at low conversions is related to a single reaction.• Model-free methodology can predict the ILs performance in isothermal conditions.

Thermal Stability of Ionic Liquids: Current Status and Prospects for Future Development

“…Although many studies have indicated Tonset obtained by dynamic TGA overestimates the thermal stability [36,39,44], it is still widely used to express the stability of ILs from divergent papers [45,46]. Despite the long-term isothermal experiments can more accurately reflect the real stability of ILs [44,[47][48][49], but it should be noted that the time in these experiments is still far less than the heat exposure time in many real applications. To provide the method in predicting long-term thermal stability, different models have been developed [50][51][52].…”

“…To solve the problem when the entire sample cannot be decomposed [47,48], nonisothermal TGA is developed as the most popular method to determine the kinetic parameters in the thermal decomposition process, and the combination of TGA data allows researchers to calculate the activation energy and pre-exponential factor in this process. Arrhenius methods are widely used in kinetics analysis due to their simple calculation process.…”

Long-term thermal stability of fatty acid anion-based ionic liquids

“…In a thermogravimetric (TG) experiment, where the variation of mass versus temperature is obtained, the extent of reaction is calculated using the following Eq. ( 2) [96,104,108,109]:…”

“…Their basic assumption is the isoconversional principle (the reaction rate for a constant α depends only on temperature). There are a variety of isoconversional methods and two different mathematical categories [95,98,99,102,104,[109][110][111] can be…”

“…Considering the importance of longterm thermal stability in industrial applications, it is essential to obtain reliable data to evaluate the feasibility of employing a specific IL in each application [95][96][97][98][99][100][101]. The search for models capable of predicting long-term stability from the typical dynamic thermogravimetric measurements is more efficient (less time-consuming) and allows the lifetimes of ILs to be used in industrial applications to be estimated [71,95,[102][103][104][105].…”