Chenln Li, Bernhard Knierim, Chithra Manisseri, Rohit Arora, Henrik V. Scheller, Manfred Auer, Kenneth P. Vogel, Blake A. Simmons, Seema Singh Auer P Vogel A Simmons Lis Nimani Biological Systems Engineering October 29th, 2010
Pretreatment is a very important step in Lignocellulosic biomass conversion. Li ll l i bi i ◦ Accounts for 16-19% of total Capital Investment (Sousa et al., 2009). ◦ E h Enhances rate of hydrolysis 3-10 f ld t f h d l i 3 10 fold. ◦ Separates Lignin and Hemicellulose for value added products. Objectives of Pretreatment: ◦ Remove cross-linked matrix of lignin and hemicellulose that embeds cellulose. ◦ Disrupt crystalline structure of cellulose. ◦ D t Destroy matrix structure of f d t k t i t t f feedstock. ◦ Increase surface area.
Several Pretreatment technologies are available: Dilute Acid Ionic Liquid Steam Explosion Ammonia Fiber Explosion Organoslov SPORL Hot Water Lime And more…
Dilute Sulfuric Acid Pretreatment Vs. Vs Ionic Liquid Pretreatment
Dilute Sulfuric Acid Pretreatment ◦ Leading pretreatment process under commercial development. d d ld l ◦ Works well with herbage, hardwood, but not softwood. • R Reactions th t t k place t Li ti that take l to Lignocellulose: ll l Cellulose: Partial degradation of the cellulose (amorphous). Hemicellulose: Dissolved by acidic hydrolysis. Formation of inhibitory compounds to fermentation organisms. Lignin: Condensed Lignin remains on cellulose.
Ionic Liquid Pretreatment ◦ Use of Ionic Liquid Solvents for Pretreatment Purposes. f dS l f Separation of Lignocellulose. Cellulose recovered with anti-solvent solutions. Disruption of cellulose structure. structure ◦ Ionic liquids are organic salts that are liquid at room temperature and are stable to 300 °C. ◦ 1-ethyl-3-methylimidazolium acetate ([ y y ([C2mim][Oac]) can ][ ]) solubilize switchgrass and reject lignin from the recovered polysaccharide. This Ionic liquid has been shown to increase the Cellulase activity on Cellulose. ◦ R Recent R t Reports h t have also shown th complete di l h the l t dissolution and l ti d partial delignification of sugarcane, softwood and hardwood in various ionic liquids.
◦ Biomass: Switchgrass (Panicum virgatum L.) Milled (Thomas Wiley Mill) with a 40 mesh screen Extraction with water followed (Thomas-Wiley with ethanol using NREL procedure.◦ Enzymes: Cellulase, β-glucosidase◦ Ionic Liquid: 1-ethyl-3-methylimidazolium acetate ([C2mim][Oac])◦ Acids/Basses: Acetic Acid Sodium Acetate Sulfuric Acid Acid, Acetate, Acid, 3,5-dinitrosalicylic Acid, Trifluoroacetic Acid, NaOH
Ionic Liquid Pretreatment: ◦ 3% (w/w) switchgrass solution prepared. (300 mg of Switchgrass with 9.7 g [C2mim][OAc]. o Heated and stirred at 160 °C for 3 hr. o After 3 hr incubation water added for regeneration of hr. incubation, dissolved cellulose, then centrifuged for 10 min. Cellulose I⇀Cellulose II (Stable Form) Dilute Acid Pretreatment: ◦ Switchgrass presoaked at room temperature with 1.2% (w/w) sulfuric acid at 3% (w/w) total solid loading for 4 hr hr. ◦ Samples were than heated at 160 °C for 20 min.
•Table 1 summarizes the various pretreatment conditions and the various amountsof cell wall components.•Both Dilute Acid and Ionic liquid pretreatments remove hemicellulose and lignin. •Dilute Acid removed 22.4 % lignin. •IL removed 69 2 % li i i ) IL d 69.2 lignin, ie)•IL pretreatment removes more lignin and less hemicellulose than dilute acidpretreatment. •IL produces recovered materials with hi h sugar and l IL d d i l i h higher d less li i lignin.
•Figure above represents sugar yields and monosaccharide composition.•This Analysis was done using HPAEC on dissolved material after pretreatment.•Dilute Acid Removes the majority of hemicellulose as well as some cellulose.•Hemicellulose removal is less in Ionic Liquid Pretreatment. •From Table 1: There is 87 % and 81% loss in Hemicellulose between Dilute Acid and Ionic liquid Pretreatments respectively.
•Table 2 data indicates the Crystallinity (CI) index as well the amount of sugar that Table index,was hydrolyzed. This data was taken using powder X-ray diffraction.•Crystallinity affects the amount of hydrolysis of cellulose. •Amorphous vs Crystalline Amorphous vs.•IL pretreatment makes cellulose amorphous changing it from cellulose I to CelluloseII. Thus, greater potential for hydrolysis.•Dilute Acid has higher CI. This is due to amorphous breakdown. •It does not have the ability to breakdown the H-bonds between fibrils.
•Chemical Fingerprinting •ATR-FTIR: (7 bands on Figure 2) •Band at 1510 and 1329(1/cm) •Indicates Lignin molecule. •Are smaller for IL than DA, UN. •Band at 1100 (1/cm) •Indicates Crystalline Cellulose. •Missing for IL; Increasing for DA. •Band at 900 (1/cm) •Indicates Amorphous Cellulose. •Are smaller for DA than IL. Indicating Increased CI for Dilute Acid Pretreatment. •Band at 1056, 1235, and 1375 (1/cm). •Indicates HemicelluloseFigure 2: ATR-FTIR, Raman Spectra •Significant Decrease for DA indicating removal of Hemicellulose.
•Ratio of 1500/900 (1/cm) •Indicates Lignin/Cellulose •IL<DA as indicated in Table 3: IL<DA i di t d i T bl 3 •Raman Spectra: (Figure 2) •Provides Molecular Understanding •Lignin features monitored. •1600 (1/cm)-lignin aromatic ring •1620 (1/cm)-Ring Conj. C=C bond. Data Indicates that IL removes much more lignin than DA.Figure 2: ATR-FTIR, Raman Spectra
Figure 4: SEM Images of Untreated (a), Dilute Acid (b), Ionic Liquid (C) g g•Untreated: Highly fibrillar and intact morphology•Dilute Acid: Cell wall not disrupted by pretreatment. Some lignin may Dilute be condensed on the surface of fibers.•Ionic Liquid: Significantly alters fibrillar structure. No fibrous structure.
•IL pretreated showed higher kinetics with digestibility reaching 96 % within 24 hrs. •Initial rates of Ionic liquid were 16.7x greater than Dilute Acid and 54 4 Dil te 54.4x greater than untreated Switchgrass. (Table 2). •Reasons for higher Kinetics in IL:Figure 5: Comparison of Saccharification by •Amorphous structure!different pretreatments •Less Lignin!
Ionic Liquid Pretreatment offers advantages over Dilute Acid Pretreatment: 1. Disrupts the matrix structure of switchgrass 2. Increases Surface Area 3. Reduces Crystallinity of Cellulose ⇒Amorphous 4. 4 Higher Delignification ⇒ Offers Purer Lignin for use of co-products. co products 5. Higher enzyme hydrolysis Problems with Ionic Liquid Pretreatment 1. New Method 2. High Cost