Analysis of thermal stability and pyrolysis kinetic of dibutyl phosphate-based ionic liquid through thermogravimetry, gas chromatography/mass spectrometry, and Fourier transform infrared spectrometry

  • Hui-Chun Jiang
  • Wei-Cheng Lin
  • Min Hua
  • Xu-Hai PanEmail author
  • Chi-Min ShuEmail author
  • Jun-Cheng Jiang


To analyze the feasibility of phosphorus-containing ionic liquids used as flame retardants on flammable materials, thermal stability and pyrolysis kinetics of 1-butyl-3-methylimdazolium dibutyl phosphate ([Bmim][DBP]) were investigated using nonisothermal thermogravimetry. The apparent onset decomposition temperature (T0) and mass fraction of residual carbon were 275.2–297.3 °C (± 0.5 °C) and 8.6–10.2% (± 0.1%), respectively. The apparent activation energy (Ea), pre-exponential factor (A), and most probable kinetic function [G(α)] were calculated using thermokinetic methods as Ea = 152–164 kJ mol−1 (± 2 kJ mol−1), ln A = 27.7 ± 0.4 s−1, and G(α) = − ln(1 − α). The maximum operation temperature was estimated as 166.0 ± 0.2 °C, which was considerably lower than T0. The pyrolysis products were identified through gas chromatograph/mass and Fourier transform infrared spectrometers. As a novel finding, the main flame-retarding mechanism of [Bmim][DBP] occurred primarily in condensed phase. Complementally, [Bmim][DBP] was testified to have the flame-retardant effect on epoxy resin by limited oxygen index and vertical burning tests.


Phosphorus-containing ionic liquid Pyrolysis kinetics Maximum operation temperature Pyrolysis products Flame-retardant effect 

List of symbols


Pre-exponential factor (s−1)


Fraction of conversion (mass%)


Heating rate (K min−1)




Reaction order, n = 0.25


First-order reaction


Reaction order, n = 3


Mass loss rate (mass% min−1)


Mass loss rate at the conversion of 0.5 (mass% min−1)


Valensi reaction


Jander reaction


Z–L–T reaction


Apparent activation energy (kJ mol−1)


Most probable kinetic function


Integral mechanism function


1 H-imidazole

ln A

Logarithmic pre-exponential factor (s−1)


Fraction of mass residual (mass%)


Mass charge ratio (°C)


3-Methyl-1 H-imidazole


Methyl imidazole


Maximum operation temperature (°C)


Mass loss less than 1.0% of MOT (°C)


Universal gas constant (8.314 J mol−1 K−1)


Regression coefficient


Time of reaction (min)


Temperature (°C)


Temperature at the conversion of 0.5 (°C)


End temperature (°C)


Maximum temperature (°C)


Apparent onset decomposition temperature (°C)


Peak temperature (°C)


Standard curve


Experimental curve



This study was very grateful to be supported by the Process Safety and Disaster Prevention Laboratory, Postgraduate Research and Practice Innovation Program of Jiangsu Province (KYCX17_0915). The authors appreciate the original suggestions and heartfelt inspiration for provided by the members of IL research groups.


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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.College of Safety Science and EngineeringNanjing Tech UniversityNanjingChina
  2. 2.Graduate School of Engineering Science and TechnologyNational Yunlin University of Science and Technology (YunTech)DouliouTaiwan, ROC
  3. 3.Jiangsu Key Laboratory of Hazardous Chemical Safety and ControlNanjingChina
  4. 4.Center for Process Safety and Industrial Disaster Prevention, School of EngineeringYunTechDouliouTaiwan, ROC
  5. 5.Department of Safety, Health, and Environmental EngineeringYunTechDouliouTaiwan, ROC

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