Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Chemistry and Biochemistry

First Advisor

Douglas E Raynie


DSC, ionic liquids, lignin, solvent, spectrometry, toxicity


Synthesis and characterization of 1-ethyl-3- methylimidazolium alkylbenzenesulfonate ionic liquids for extraction of lignin from prairie cord grass have been studied. The ionic liquids (ILs) 1-ethyl-3- methylimidazolium benzenesulfonate (EBS), 1-ethyl-3- methylimidazolium toluenesulfonate (ETS) and 1-ethyl-3- methylimidazolium xylenesulfonate (EXS) have been synthesized in this research. An extensive structural, physical, thermal and toxicological characterization has been performed to understand the behavior of these ionic liquids. The reaction yield for the synthesis of EBS, ETS, and EXS ionic liquids was determined to be 91.2 ± 1.5 %, 96.1 ± 0.7 %, 99.0 ± 0.5 % respectively. Spectral analysis using NMR and FTIR confirms the structure of these ionic liquids. The Kamlet-Taft properties of these ionic liquids have been determined using solvatochromic probes limited to Reichardt’s dye, 4-nitroaniline and N,N-diethyl-4- nitroaniline. Viscosity, polarity and hydrogen bond acidity of EBS, EEBS, ETS, and EXS ILs was found to increase with increasing methylation and anion size in the following order EBS < ETS < EXS. Thermal analysis of the ILs has been performed using DSC and TGA. Study of the glass transition and mesomorphic phases has been analyzed using DSC. The TGA has been used to determine thermal stability of the ILs. The EBS and EEBS were found to have decomposition onset around 349 oC, which is higher than the decomposition onset of ETS and EXS at 331°C and 319°C respectively. Thermal behavior of the ILs has been studied at different nitrogen flow rates, where the significant mass loss after 300°C was attributed to thermal decomposition of ILs. Toxicological studies were performed using LDH, MTT and Ames assays. The EXS exhibited highest cytotoxicity and genotoxicity followed by ETS and then EBS. The optimal temperature in the lignin extraction study was found to be at 90 oC for 3 hours without addition of water or steampretreatment. The percent lignin extracted from PCG using EBS, EEBS, ETS and EXS ILs was found to be 17.5±0.28, 17.4±0.53, 19.6±0.07 and 21.9±0.05 respectively.

Library of Congress Subject Headings

Ionic solutions.
Biomass energy.
Renewable energy sources.


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright