Effects of Organosolv Fractionation Process on the Properties of Switchgrass Lignin as a Precusor for Carbon Products Pyoungchung Kim, 1* Darren Baker 1 , Nicole Labbé 1 1 Center for Renewable Carbon, University of Tennessee, Knoxville TN 37996 * Corresponding Author. Email: [email protected] Introduction Feedstock : Switchgrass Extractives Removal Accelerated Solvent Extractor (ASE) H 2 O extraction • 100 o C, 7 min/cycle, 3 cycles EtOH extraction • 100 o C, 7 min/cycle, 3 cycles Solvent Fractionation : Extractive-free feedstock Solvent mixture H 2 O (50%), EtOH (36%), MIBK (14%), Catalyst : H 2 SO 4 (0.6 %, 0.05 M) Study variables Reaction time : 10, 20, 30, 40, 60, 80 min 10 min/cycle Pressure : 1600 – 1700 psi Temperature : 140, 160, 180 o C Products Cellulose : washed with DI water (2L) Lignin : washed with DI water (2L) Moisture content Extractives Ash Cellulose Hemicellulose Lignin Average (%) 7.4 6.3 2.4 33.7 28.1 22.3 St dev (%) 0 0.0 0.3 0.7 0.9 0.6 0 20 40 60 80 100 Remained biomass (%) 20 40 60 80 140 oC 160 oC 180 oC Time (min) 0 20 40 60 80 100 Hemicellulose (%) 0 10 20 30 40 50 60 140 oC 160 oC 180 oC Time (min) 0 20 40 60 80 100 Cellulose (%) 50 60 70 80 90 100 110 120 140 oC 160 oC 180 oC Time (min) 0 20 40 60 80 100 Lignin (%) 0 10 20 30 40 50 60 140 oC 160 oC 180 oC Biomass recovery Cellulose in solid fraction Hemicellulose in solid fraction Lignin in solid fraction Biomass loss in the reactor showed a gradual increase by reaction time under different temperature and presented a loss up to 45 % at 140 o C, 55 % at 160 o C and 64 % at 180 o C for 60 min reaction time. Of the solid fraction, cellulose decreased less than 3 % under 140 o C, 7 % under 160 o C for 60 min, and 30 % under 180 o C for 60 min. Hemicellulose fraction significantly decreased for 60 min to 78 % under 140 o C, 88 % under 160 o C and 95 % under 180 o C. Simultaneously, lignin fraction also decreased to 72 % under 140 o C, 87 % under 160 o C and 87 % for 30 min and did not decreased by time under 180 o C. Principal component analysis (PCA) of FTIR spectra of lignin showed that lignins produced at 180 o C were apparently separated with other lignins produced 140 and 160 o C by the first principal component (PC1, accounting for 75% of the total spectral variance) (Scores plot). TGA showed that lignins produced at high temperature produced more residues (40.8±1.0%) than lignins produced at low temperature (35.6±2.1% – 36±1.0%). This indicates that lignins at high temperature may contain more condensed aromatic structures, which is more thermally stable. Derivative thermograms (DTG) showed that the first stage of maximum degradation (T max ) at 280 o C is related to thermally weak side chains such as β-O-4 linkage in lignin. The second stage of T max at 380 o C is related to lignin itself. The third stage of T max at higher than 650 o C is related to functional groups present in lignins and their derivatives leading to complex crosslinked structures that are thermally stable. With increasing reaction time and temperature to isolate lignin from biomass, side chains were broken and decreased. Experimental set-up Chemical composition (switchgrass) Biomass recovery by Wet chemistry Lignin by FT-IR Introduction The desire to reduce fossil fuel derived products and mitigate greenhouse gas emissions with increasing demand for natural products has led to the rapid expansion of the biomass-based industry. The application of biomass fractionation provides clean product streams to produce a wide range of value added products such as materials, chemicals, fuel, heat and power. Clean fractionation is a type of organosolv pre-treatment that upgrades biomass feedstocks for a biorefinery by separating the cellulose, hemicellulose, and lignin into pure streams for conversion into value-added products. Organosolv fractionation uses a mixture of an organic solvent and water to cleanly separate the three major components of biomass. Through this solvent fractionation technique, the extraction efficiency is improved, which reduces conversion times and increases yields, allowing the biomass to be processed more economically. After fractionation, the solvent fraction is rich in lignin and hemicellulose components and cellulose is present in the solid phase. Objective The objective of this study was to optimize processing parameters of organosolv fractionation, including time and temperature in terms of producing a derived lignin for carbon based materials production Switchgrass ASE (H 2 O, EtOH, MIBK, H 2 SO 4 ) Cellulose Liquid fraction extractives ASE (H 2 O, EtOH) Lignin Hemicellulose Solid fraction Evaporation Washing Accelerated Solvent Extractor (ASE) Scores plot of PC2 (12%) showed that lignins were also separated by longer reaction time with higher temperature. Loadings plot of PC2 indicate that lignins produced at longer reaction time with higher temperature were more oxidized. Loadings plot by PC1 indicate that more condensed aromatic structures are produced from lignins produced at 180 o C Lignin by Pyrolysis-GC/MS Lignin by Thermogravimetric analysis Gas chromatograms produced by pyrolysis at 450 o C for 12 s showed that lignins produced at different temperature and time contained dominantly peaks of guaiacyl and syringyl subunits and small peaks of carbohydrates (acetic acid, furfural) that were chemically bonded to lignin even after washed by deionized water. 0 5 10 15 20 25 30 35 40 Intensity (a.u.) Time (min) Furfural MIBK Acetic acid Acetic acid Phenol Methyl Phenol Guaiacol Dimethyl phenol Methyl guaiacol Mehtyl benzalde hyde Ethylguai acol Vinyl guaiacol Propenyl guaiacol Syringol Vanillin Vanillic acid Acetosyringone Methoxy methylbenzo furan Methyl eugenol Vanillin Coniferyl aldehyce 140-80 160-80 180-80 Temp ( o C) 100 200 300 400 500 600 700 800 900 Wt (%) 0 20 40 60 80 100 DTG (d wt(%) /d temp ) -0.06 -0.04 -0.02 0.00 180 o C-80min 180 o C-40min 160 o C-80min 160 o C-40min 140 o C-80min 140 o C-40min Maximum yield of lignin was produced at 160 o C for 60 min and 180 o C for 30 min. Increasing temperature and reaction time produced more condensed aromatic skeleton and less β- O-4 linkage. Lignins produced from switchgrass contained complex crosslinked structures with functional groups and their derivatives. Future work Structural features of lignin by Nuclear Magnetic Resonance. Molecular weight distribution by Gel Permeation Chromatography. References Conclusion and Future work Sing et al. “Lignin–carbohydrate complexes from sugarcane bagasse: Preparation, purification, and characterization, Carbohydrate Polymers, 62, 57-66 (2005) Bozell et al. “Biomass fractionation for the biorefinery: Heteronuclear mulitple quantum coherence-nuclear magnetic resonance investigation of lignin isolated from solvent fractionation of switchgrass, Agriculture and food chemistry, 59 9232-42 (2011) SunGrant Initiative Acknowledgement Wavenumber (cm -1 ) 600 800 1000 1200 1400 1600 1800 Loading plot (PC1 75%) -0.10 -0.05 0.00 0.05 0.10 Loadings plot of PC1 Wavenumber (cm -1 ) 600 800 1000 1200 1400 1600 1800 Loadings plot (PC2 12%) -0.10 -0.05 0.00 0.05 0.10 0.15 1600 1504 G 1464 G 1408 1123 G 1030 1530 1719 1295 1220 G 1157 830 Loadings plot of PC2 PC1 (76%) -6 -4 -2 0 2 4 6 PC2 (12%) -2 -1 0 1 2 3 140-60 140-80 160-60 160-80 180-30 180-40 180-50 180-60 180-80 Scores plot