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Summary

Abstract

Introduction

Protocol

Representative Results

Discussion

Acknowledgements

Materials

References

Environment

Pretreatment of Lignocellulosic Biomass with Low-cost Ionic Liquids

Published: August 10th, 2016

DOI:

10.3791/54246

1Department of Chemical Engineering, Imperial College London

The pretreatment of lignocellulosic biomass with protic low-cost ionic liquids is shown, resulting in a delignified cellulose-rich pulp and a purified lignin. The pulp gives rise to high glucose yields after enzymatic saccharification.

A number of ionic liquids (ILs) with economically attractive production costs have recently received growing interest as media for the delignification of a variety of lignocellulosic feedstocks. Here we demonstrate the use of these low-cost protic ILs in the deconstruction of lignocellulosic biomass (Ionosolv pretreatment), yielding cellulose and a purified lignin. In the most generic process, the protic ionic liquid is synthesized by accurate combination of aqueous acid and amine base. The water content is adjusted subsequently. For the delignification, the biomass is placed into a vessel with IL solution at elevated temperatures to dissolve the lignin and hemicellulose, leaving a cellulose-rich pulp ready for saccharification (hydrolysis to fermentable sugars). The lignin is later precipitated from the IL by the addition of water and recovered as a solid. The removal of the added water regenerates the ionic liquid, which can be reused multiple times. This protocol is useful to investigate the significant potential of protic ILs for use in commercial biomass pretreatment/lignin fractionation for producing biofuels or renewable chemicals and materials.

Meeting humanity's energy demand sustainably is one of the greatest challenges that our civilization faces. Energy use is predicted to double in the next 50 years, putting greater strain on fossil fuel resources. 1 The buildup of greenhouse gases (GHG) in the atmosphere through wide-spread fossil fuel use is particularly problematic, as CO2 generated from combustion of fossil fuels is responsible for 50% of the anthropogenic greenhouse effect. 2 Therefore, large-scale application of renewable and carbon neutral technologies is essential for meeting the increased energy and material needs of future generations. 1, 3

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Note: The protic ionic liquids used in the process are synthesized in our laboratory, although some might be or become commercially available. The resulting ionic liquids are acidic and corrosive and probably skin/eye irritants (depending on the amine used), and must therefore be handled with care wearing appropriate PPE (lab coat, safety specs, resistant gloves).

1. Preparation

  1. Preparing and storing the lignocellulosic biomass
    1. Obtain the lignocellulosi.......

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The exact amount of lignin removal and lignin precipitation, recovered pulp and glucose yield depend on the type of biomass used, the temperature at which the treatment is run and the duration of the treatment. Short pretreatment times and low temperatures lead to incomplete pretreatment while at higher temperatures the cellulose becomes unstable in the ionic liquid, leading to hydrolysis and degradation. The selected ionic liquid also plays an important role in the outcome of the fractio.......

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The technique for the fractionation of lignocellulosic biomass presented here produces a cellulose-rich pulp and a lignin. Most of the hemicelluloses are dissolved into the ionic liquid and hydrolyzed, but not recovered. If hemicellulose sugars are desired, a hemicellulose pre-extraction step prior to the Ionosolv delignification may be necessary. It has so far been impossible to fully close the mass balance for the biomass, as it is not possible to identify and quantify all degradation products found in the ionic liquid.......

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The authors acknowledge the Grantham Institute for Climate Change and the Environment, Climate-KIC and EPSRC (EP/K038648/1 and EP/K014676/1) for funding and Pierre Bouvier for providing experimental data for pine pretreatments.

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Name Company Catalog Number Comments
IL synthesis
Round bottom flask, with standard ground joint 24/29 NS, 1000 ml Lenz 3 0024 70 VWR product code 271-1309 
250mL Addition Funnel, Graduated, 29/26 Joint Size, 0-4mm PTFE Valve GPE CG-1714-16
Dish-shaped dewar flask, SCH 31 CAL  KGW-Isotherm 1197
Volumetric flask, 200 ml VWR 612-3745 
Cork rings, pasteur pipettes and teet, wash bottle with deionised water, large magentic stir bar
Biomass size reduction
Heavy Duty Cutting Mill SM2000  Retsch  Discontinued Replaced with Cutting Mill SM 200 (20.728.0001) 
Bottom sieves (10 mesh square holes, for particle size <2 mm) Retsch  03.647.0318 Part of cutting mill
Analytical Sieve Shaker AS 200 Retsch  30.018.0001 Part of sieving machine
Test Sieve 200 mm Ø x 50 mm height ISO 3310/1 (180 µm) Retsch  60.131.000180 Part of sieving machine
Test Sieve 200 mm Ø x 50 mm height ISO 3310/1 (850 µm) Retsch  60.131.000850 Part of sieving machine
Collecting pan, stainless steel, 200 mm Ø, height 50 mm  Retsch  69.720.0050 Part of sieving machine
Rotary evaporator:
Rotary evaporator (Rotavapor R-210) Buchi  Discontinued Replaced with Rotavapor R-300
Water bath (Heating bath B-491) Buchi  48201 Part of rotary evaporator
Recirculator  Julabo F25 Part of rotary evaporator
Vacuum pump (MPC 101 Z) Ilmvac GmbH 412522 Part of rotary evaporator
Vacuum controller (Vacuum Control Box VCB 521) Ilmvac GmbH 600053 Part of rotary evaporator
Parallel evaporator:
StarFish Base Plate 135mm (for Radleys & IKA)  Radleys RR95010 Part of parallel evaporator
Monoblock for 5 x 250ml Flasks Radleys RR95130  Part of parallel evaporator
Telescopic 5-way Clamp with Velcro Radleys RR95400 Part of parallel evaporator
Gas/Vacuum Manifold with connectors Radleys RR95510  Part of parallel evaporator
650mm Rod Radleys RR95665  Part of parallel evaporator
Quick Release Male, R/A Barbed 6.4mm + Shut-off (3.2mm ID)  Radleys RR95520 Part of parallel evaporator
Stirrer/hot plate Radleys RR98072 Part of soxhlet extractor
Temperature controller Radleys RR98073 Part of soxhlet extractor
Elliptical Stirring Bar 15mm Rare Earth Radleys RR98097  Part of parallel evaporator
Vacuum cold trap, plastic coated, PTFE stopcock Chemglass CG-4519-01 Part of parallel evaporator
Vacuum pump (MPC 101 Z) Ilmvac GmbH 412522 Part of parallel evaporator
Tygon tubing E-3603, 6,40 mm (internal) 12,80 mm (external)   Saint-Gobain/VWR 228-1292  Part of parallel evaporator
Parallel Soxhlet extractor:
StarFish Base Plate 135mm (for Radleys & IKA) Radleys RR95010  Part of soxhlet extractor
Monoblock for 5 x 250ml Flasks Radleys RR95130  Part of soxhlet extractor
Telescopic 5-way Clamp with Velcro Radleys RR95400  Part of soxhlet extractor
Telescopic 5-way Clamp with Silicone Strap and Long Handle Radleys RR95410  Part of soxhlet extractor
Water Manifold with connectors Radleys RR95500  Part of soxhlet extractor
650mm Rod Radleys RR95665  Part of soxhlet extractor
Quick Release Male, R/A Barbed 6.4mm + Shut-off (3.2mm ID) Radleys RR95520  Part of soxhlet extractor
Coil condensers with standard ground joints 29/32 NS Lenz 5.2503.04  Part of soxhlet extractor
Extractor Soxhlet 40mL borosilicate glass 29/32 socket 24/29 cone Quickfit EX5/43  Part of soxhlet extractor
Stirrer/hot plate Radleys RR98072 Part of soxhlet extractor
Temperature controller Radleys RR98073 Part of soxhlet extractor
Recirculator Grant LTC1 Part of soxhlet extractor
Cellulose extraction thimble Whatman 2280-228
Tweezers Excelta 20A-S-SE
Vacuum drying oven:
Vacuum drying oven Binder VD 23 Part of vacuum oven
Dewar vessel 2L 100x290mm with handle KGW-Isotherm 10613 Part of vacuum oven
Vacuum Trap GPE CG-4532-01  Part of vacuum oven
Other equipment:
Analytical balance A&D GH-252 accuracy to ± 0.1 mg
Volumetric Karl Fischer titrator Mettler Toledo V20
10 mL disposable pipette Corning Inc Costar 4101 10 mL Stripette
Eppendorf Research plus pipette, variable volume, volume 100-1000 μL Eppendorf 3120000062
Desiccator Jencons JENC250-028BOM
Ace pressure tube bushing type, Front seal, volume 15 mL  Ace Glass 8648-04 
Ace O-rings, silicone, 2.6 mm, I.D. 9.2 mm  Ace Glass 7855216 O-ring for pressure tube
Vortex shaker VWR International 444-1378 (UK)
Fan-assisted convection oven ThermoScientific HeraTherm OMH60
Oven glove (Crusader Flex) Ansel Edmont 42-325
250 mL Round bottom flask single neck ground joint 24/29 (Pyrex) Quickfit  FR250/3S
Rotaflo stopcock adapter with cone 24/29 Rotaflo England MF11/2/SC
50 mL Falcon  tube Heraeus/Kendro HERA 76002844
Centrifuge (Mega Star 3.0) VWR  521-1751
Reagents:
Ethanol absolute VWR 20820.464
Triethylamine Sigma-Aldrich T0886
Sulfuric acid 5 mol/l (10N) AVS TITRINORM volumetric solution Safe-break bottle 2,5L VWR 191665V
Purified water (15 MΩ ressitance) Elga CENTRA R200
Lignocellulosic biomass:
Miscanthus X gigantheus
Pinus sylvestris

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