Ionic Liquids for Biomass Fractionation

Prof. Tom Welton Imperial College Sustainable Chemistry

• Sustainable development: – To meet the needs of the present generation without compromising the ability of future generations to meet their own needs. • Sustainable Chemistry: – The implementation of sustainability in the production and use of chemicals and the application of chemistry and chemical products to enable sustainable development. The Petrochemical Refinery

• Both fuels and chemicals products are made in petrochemical refineries • High value added (HVA) chemicals are 4% of the mass produced, but 30% of the value The Integrated Biorefinery

• The integrated biorefinery can contribute to carbon efficient fuels and chemicals manufacture Synthetic Challenge

• To make currently available materials from renewable sources • To make new materials that can match the properties of currently available materials • To make new materials that have new properties that currently available materials don’t • New processes must be sustainable.

Synthetic Approaches

• Target-directed synthesis – Design synthetic routes to yield a required product. – Pharmaceuticals • Ease of synthesis – Select materials made available by simple processing. – ‘Click’ chemistry • Many of today’s products came from a combination of these.

New Processes

• It is only by commercial application that a process can have any effect, for good or ill, on the environment. • Problem: – Less than10% of consumers have shown that they will pay a premium price for ‘green’ products.

• New products and processes must deliver cost competitive consumer products to the market. New Processes

• New processes must be both economically and environmentally sustainable. – The cost of capital equipment change is a major block to implementation of sustainable processes. – New process based on new raw materials can be sustainable from the outset. – New industries can be sustainable from the outset. • Productivity not pollution: – Efficient use of raw materials – Low waste – Reuse/recycle – Low energy use/energy recovery Waste (E-factor)

Annual product Industry Sector tonnage E-factor

Oil Refining 106 - 108 <0.1

Bulk chemicals 104 - 106 1 - 5

Fine chemicals 102 - 104 5 - 50

Pharmaceuticals 10 - 103 25 - 100

The amount of waste per kg of product (“kilos in/kilos out”) varies greatly across the chemical industry 9 Waste (E-factor)

Synthesis Industry Sector E-factor steps

Oil Refining <0.1 1

Bulk chemicals 1 - 5 1 - 3

Fine chemicals 5 - 50 3-5

Pharmaceuticals 25 - 100 >10

The E-factor (and cost) is dominated by the number of steps in the synthesis. 10 Lignocellulose Biomass

• Agricultural and forest wastes • Dedicated biofuel crops

• Billion-ton scale • Higher yields • Large range of plants to suit the climate and soil Lignocellulose types

Grass Hardwood Softwood Structure and composition of lignocellulose • Cell walls consist of fibres, hemicelluloses and a network • Middle lamella consists of lignin and hemicelluloses: Structure and composition of lignocellulose

Hemicellulose

Lignin Cellulose Lignocellulose recalcitrance

• High sugar content (35-50% cellulose, 20- 30% hemicellose) • But: lignocellulose evolved to be resistant

What does a pretreatment do?

• Separate biomass components • Increase availability of carbohydrates for subsequent processing. • Provide ligning in a useful(?) form. Biomass Pretreatment options with Ionic Liquids Dissolved cellulose Re-precipitated cellulose swollen wood

Fuels [cat]X Anti-solvent

biological processing of wood

Dissolved lignin Separated Cellulose Pine Willow [cat][HSO4] Fuels Miscanthus Filter / Wash Lignin solution to chemicals Biomass Pretreatment options with Ionic Liquids Dissolved cellulose Re-precipitated cellulose swollen wood

Fuels [cat]X Anti-solvent

biological processing of wood

Pine Willow Miscanthus Kamlet-Taft solvent polarity

responds to changes in responds to changes responds General polarisability/ dipolarity in H-bond acceptance to changes in H-bond donation

N O- NH2

N+

NO2 NO2

• by comparing measurements made with each dye can calculate ,  and * • experimentally many dye sets are used, but the principle is the same Kamlet-Taft solvent polarity

• Use probes that can sense a change of environment • Probes are dye molecules whose absorption peak maxima shift

• Three parameters: •  – ability to donate hydrogen bonds •  – ability to accept hydrogen bonds •  * – polarizability Kamlet Taft parameters

Ionic liquid anion α ß π

[OTf]- 0.63 0.49 0.97

[N(CN)2]- 0.54 0.60 1.05

[MeSO4]- 0.55 0.67 1.05

[Cl]- (75°C) 0.49 0.83 1.03

[Me2PO4]- 0.45 1.12 0.97

[MeCO2]- 0.47 1.20 0.97

 Correlation with  and ability to dissolve (ligno)cellulose Ionic liquids pretreatment is moisture sensitive • Water reduces pretreatment efficiency (Doherty et al., , 2010) • Biomass contains moisture (7-20%) • Ionic liquids that dissolve cellulose when dry are most hygroscopic

4,0

3,5 3,0 2,5 2,0 1,5 1,0 pair ion per molecules 0,5

ater 0,0 W 0,4 0,9 Hydrogen-bond basicity of anion

Ionic Liquids Biomass Dissolution Process

Biofuel 8 process steps Production Hemicellulose Biomass Isolation - H O Pre-drying 2 Washing

Biomass Cellulose Lignin + IL Filtration Dissolution Precipitation Isolation

+ H2O

Chemicals Synthesis IL Recovery and Drying

- H2O Biomass Pretreatment with Ionic Liquids

Dissolved lignin Separated Cellulose Pine Willow [cat][HSO4] Fuels Miscanthus Filter / Wash Lignin solution to chemicals [C4C1][HSO4] (80% in water) ionic liquid pretreatment

Ionic liquid without Ionic Liquid + added water 20% Water [C4C1][HSO4] (80% in water) ionic liquid pretreatment

Composition after Composition before pretreatment with [C C im][HSO ] pretreatment 4 1 4 Other sugar 4.4% Residue Protein, 19% extractives, ash 9,0%

Glucose 39,5% Xylose 11% Lignin 25,0%

Glucose 70% Xylose 19,0% Ionic Liquids Biomass Ionosolv Process

Biofuel 6 process steps Production Hemicellulose Isolation Washing

+ IL/H2O Biomass Lignin Filtration + H O Deconstruction Isolation 2

Chemicals Synthesis IL Recovery and Partial drying

- H2O [cat][HSO4] ionic liquid pretreatment 26.5 % Lignin 2. Solubilised lignin in IL & 80% IL-20% H2O H O 1. 2 43.6% Mischantus Cellulose (1 g)

3. Carbohydrate-rich material (CRM) 24.3% • Cellulose Hemicellulose • Hemicellulose • Undisolved lignin

Enzymatic Saccharification

5a. Cellulose  Glucose

5. Hydrolysed CRM 5b. Hemicellulose  Xylose 6. Unhydrolysed CRM Sugar recovery (5)

80 74,3 Glucose

70 Xylose

60

50

39,1 40

30 27,4 27,1 24,9

20 assay of recovered (%) CRM of recovered assay 16,6 13,8 13,7 10,0 10

Sugars released via enzymatic saccharification saccharification enzymatic via released Sugars 2,2 0 [EtNH3][HSO4] [Et2NH2][HSO4] [Et3NH][HSO4] [HC4im][HSO4] [C1C4im][MeOSO2]

Glucose recovery as % of cellulose in original biomass (5a). Xylose recovery as % of hemicellulose in original biomass (5b). Sugar recovery (5)

100 96 Glucose 90 Xylose 80 74,9

70

60 (%) 50

40

30 Sugarsreleased via enzymatic

20 saccharification assay of recovered CRM

10 2,25 2,9 0 Typical procedure Continuous washing (3 times washing) (Soxhlet extractor) Ionic Liquid on Cellulose

(a) EDX elemental mapping image of sulphur on the commercial cellulose treated in [HC4im][HSO4]80% at 120oC & washed.

(b)

(c)

Red spots represent sulphur on the surface of treated CRM (black). White spots are caused by a surface charging effect.

EDX spectra of commercial cellulose (a) untreated (b) wetted with [HC4im][HSO4] (c) 31 o treated in [HC4im][HSO4] at 120 C and washed using typical procedure. Ionic Liquid on Biomass

(a)

(b)

(c)

SEM images and EDX elemental analysis spectra of (a) untreated miscanthus (b) CRM washed using typical procedure and (c) CRM continuously washed using soxhlet extractor. Effect of Washing CRM on Sugar Production

Treated CRM washed using typical washing Treated CRM continuously washed using soxhlet extractor.

Red spots show sulphur on the surface of recovered CRM (black). White spots caused by charging effect. Effect of Ionic Liquid on Enzymatic

100 Saccharrification Cellulose 92,3 90

80

70

60

50

40 37,6 cellulose (%) cellulose

30 25,6

20 15,5

Glucose released sigma of g 1 from released Glucose 10 0,0 0 Absence 0.1% 1% 5% 10% Conc. [HC4im][HSO4] (%) Ionic Liquid on Cellulose

Description EDX analysis % N S

Sigma cellulose - -

1.Cellulose mixed with [HC4im][HSO4]80%-H2O20%. - 0.27 2.Immediately filtered/washed with EtOH 3 times.

1.Cellulose mixed with [HC4im][HSO4]80%-H2O20%. - 0.27 2.The mixture was left at room temperature for 22 h. 3.The mixture was filtered/washed with EtOH 3 times

1.Cellulose mixed with [HC4im][HSO4]80%-H2O20%. - 0.67 2.The mixture was heated at 120oC for 22 h. 3.The mixture was filtered/washed with EtOH 3 times Suggests chemisorption of anion Ionic Liquid on Cellulose

- [HSO4] can react with alcohol groups on cellulose to give sulfate esters

Excess water during washing drives the reaction to reverse Ionosolv Process – next steps

Biofuel 4/5 process steps Production

To be optimised Washing

+ IL/H2O Biomass Hemicellulose Filtration Deconstruction Isolation ? ?

Use IL lignin solution directly Chemicals Synthesis

IL Recovery Acknowledgements

• Dr Agi Brandt • Dr Jason Hallett • Mr Shikh Mohd Shahrul Nizan Shikh Zahari

• Porter Institute, Imperial College

• JBEI, US (Blake Simmons, Anthe George)