Kinetics and thermodynamic parameters of ionic liquid pretreated rubber wood biomass

Abstract

The impact of ionic liquids (ILs) namely 1-butyl-3-methylimidazolium chloride ([BMim][Cl]) and 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]) on rubber wood pyrolysis kinetic and thermodynamic parameters were investigated using thermogravimetric analysis (TGA). The ILs treated and untreated samples were characterized with FT-IR and elemental (CHNS) analyses. The activation energy for untreated and ILs treated rubber wood (RW) were determined using the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink methods. The average activation energy calculated using FWO, KAS and Starink methods for untreated rubber wood was 120.15kJ/mol, 117.10kJ/mol and 117.60kJ/mol, [BMIM][Cl] treated rubber wood was 87.32kJ/mol, 77.73kJ/mol, and 81.16kJ/mol, while [BMIM][OAc] treated rubber wood was 85.64kJ/mol, 76.63kJ/mol, and 80.47kJ/mol, respectively. Starink method was further used to determine the pre-exponential factor and thermodynamic parameters of untreated and ILs treated samples. The thermo kinetics and thermodynamic parameters indicate that ILs pre-treatment decreases the thermal stability of the rubber wood. From FTIR analysis, it was observed that ILs pre-treatment affected the chemical composition of rubber wood. Elemental analysis showed that ILs treated RW has a higher content of Hydrogen/Carbon ratio because of the separation of lignin and hemicellulose during pre-treatment. It was concluded that ILs pre-treatment provided a potential way to improve the thermal conversion efficiency of rubber wood.