Thermal Kinetics of Monocationic and Dicationic Pyrrolidinium-Based Ionic Liquids

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Ionic liquids (ILs) are versatile compounds with tunable properties.
• Dicationic ILs offer unique structural advantages over traditional monocationic ILs.
• Understanding the thermal degradation behavior of ILs is crucial for their application.

Purpose of the Study:

• To compare the kinetic thermal degradation of monocationic and dicationic ionic liquids.
• To analyze the thermal stability of 1-butyl-1-methylpyrrolidinium bromide ([C4MPyr][Br]) and 1,4-bis(1-methylpyrrolidinium-1-yl)butane dibromide ([BisC4MPyr][Br2]).
• To investigate the relationship between kinetic parameters (activation energy and pre-exponential factor) and thermal stability.

Main Methods:

• Non-isothermal thermogravimetric analysis (TGA) was employed.
• Thermal analyses were conducted across a temperature range of 50-650 °C.
• Multiple heating rates (5, 10, 15, 20, 25 °C/min) were utilized for kinetic analysis.

Main Results:

• Dicationic IL ([BisC4MPyr][Br2]) exhibited lower thermal stability than monocationic IL ([C4MPyr][Br]).
• Kinetic parameters, including activation energy (E) and pre-exponential factor (log A), were calculated using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Starink methods.
• The average E and log A for [BisC4MPyr][Br2] were found to be lower than those for [C4MPyr][Br].

Conclusions:

• The dicationic IL ([BisC4MPyr][Br2]) is less thermally stable compared to its monocationic counterpart ([C4MPyr][Br]).
• Lower activation energy and pre-exponential factor values in the dicationic IL correlate with its reduced thermal stability.
• A significant relationship exists between the kinetic parameters (E, log A) and the thermal stability of ionic liquids.