Influence of aqueous alkali concentration on extraction of lignin

from spruce wood

Ekaterina KorotkovaÅbo Akademi University

Laboratory of Wood and Paper Chemistry

COST ACTION FP0901 Final meeting, September 17th-18th, 2013

RefineryConversion of raw material intoproducts of value (e.g. oil refineryproduces multiple fuels and productsfrom crude oil)

What are Refinery and Biorefinery?

BiorefineryConversion of biomass to produce fuels,power, and chemicals

http://en.wikipedia.org/wiki/Oil_refinery Biorefinery Ireland Ltd  http://www.biorefinery.ie

Why wood?

• No direct competition with food and feed production

• Relatively cheap

• Highly available

• Sustainable, natural, and renewable

• Carbon neutral

Hot‐water pre‐extraction

Dilute alkaliextractionGrinding

Hemicelluloses Lignin

Residue (Cellulose for 

dissolving pulp etc.)

Acetone pre‐extraction

Lipophilicextractives

•Papermaking•Cosmetics•Health care•Textiles•etc.

•Emulsifiers•Binders•Soaps •Lubricants•etc.

•Adhesives•Composites•Polymer additives•Cement and concrete additive•Base material for chemicals (vanillin…)•Fertilizers•Energy•etc.

Our biorefinery concept

Due to its phenolic structure, lignin has great potential in different areas. Extractionfrom wood using pressurised hot water with addition of alkali is a promising way toobtain new, more reactive types of lignin for future applications.

http://www.innventia.com/en/Our-Expertise/Chemical-Pulping-and-bleaching/Carbon-fibreshttp://www.tecnaro.de/english/willkommen.htm?section=we

Sample preparation

0.5-1 mm

Accelerated Solvent Extraction (ASE)

*Dionex ASE 350 Accelerated Solvent Extractor Operator's Manual

Acetone pre-extraction

Air drying

Lignin extraction

Lignin precipitation

Lignin filtration, washing

Lignin freeze-drying

• 170°C

• 4 hours extraction

• 1% and 2% NaOH

Choosing of lignin extraction mode

1×240 minutes

Extraction mode

4×60 minutes

6×40 minutes

12×20 minutes

2×120 minutes

0

20

40

60

80

100

120

140

160

180

200

220

240

0 20 40 60 80 100 120 140 160 180 200 220 240

240 min

2x120 min

4×60 min

6×40 min

12×20 min

Extraction mode

Lignin, mg/g of dry wood

Time, min

Influence of extraction mode on amount of isolated lignin (2% NaOH)

0

20

40

60

80

100

120

140

160

180

200

220

240

0 20 40 60 80 100 120 140 160 180 200 220 240

240min

2x120 min

4x60min

6x40min

12x20 min

Lignin, mg/g of dry wood

Time, min

Extraction mode

Influence of extraction mode on amount of isolated lignin (1% NaOH)

0

10

20

30

40

50

60

40 min 80 min 120 min 160 min 200 min 240 min

2% NaOH

1% NaOH

Lignin, mg/g dry wood

Extraction time

Amount of isolated lignin (6x40 min mode)

Sugar composition in isolated lignins (2% NaOH, 6x40 min mode)

0

5

10

15

20

25

30

35

40

0 50 100 150 200 250

AraRhaXylManGalGlcGlcA4-O-MeGlcAGalA

mg/g of lignin

Time, min

Acetone pre-extraction

Air drying

Lignin extraction

Lignin precipitation

Lignin filtration, washing

Lignin freeze-drying

Hot water pre-extraction

0

2

4

6

8

10

12

14

16

no pre-extraction 20 min pre-extraction 45 min pre-extraction 60 min pre-extraction

% of dry wood

Amount of isolated lignin from hot-water pre-extracted wood

0

10

20

30

40

50

60

70

no pre-extracton 20 min pre-extraction 45 min pre-extraction 60 min pre-extraction

mg/g of isolated lignin

Sugar content in isolated lignin before and after hot-water pre-extraction

*Xyl and Gal were the most abundant sugar units in isolated lignins

Conclusions

• Obtained lignin has no unpleasant odour

• Within 4 hours of total extraction time:

o Shorter runs are more effective for yield of isolated lignin;however more solvent is used

o Higher alkali concentration allows extracting more lignin fromspruce wood

• Pre-extraction with hot water decrease the amount of sugars inthe isolated lignins

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The International Doctoral Programme in Bioproducts Technology PaPSaT is gratefully acknowledged for financial support