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Characterisation of black liquor constituents

Klaus Niemelä, Tarja Tamminen, Taina Ohra-aho

FP0901 Workshop, Wien, Austria

February 4-5, 2010

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Main topics

• Current pulp production and by-products

• Where is potential for new by-products?

• Characterisation of the fractions; analytical methods

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Non-wood (soda, sulfate)

Semichemical

Sulfite

Kraft (sulfate)

Mechanical

20%

10%3%4%

63%

Global pulp production – 190 million tons

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By-product potential from kraft pulping

Chips240 million tons

Kraft pulp (wood)120 million tons

Black liquor organics120 million tons

Current by-products<2 million tons

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Distribution of black liquor organics

Softwood Hardwood

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Tall oil and turpentine

• Production by kraft cooking

Tall oil: 1.5 million tons

Turpentine: 200,000 tons

• Production by pine tapping

Rosin: 700,000 tons

Turpentine: 100,000 tons

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Kraft and soda lignin

• "Production" >60-70 million tons

• <100,000 tons isolated for chemical applications

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Other products

Past:

Methanol, acetone, butanone

Oils (incl. diesel oil)

Ammonia

Prehydrolysis products

Present:

DMS, DMSO, DMSO2

Pulp mill methanol distillation column, Finland, 1910s

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Distribution of black liquor organics

Softwood Hardwood

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Polysaccharide-derived products

• Hydroxy monocarboxylic acids

• Dicarboxylic acids

• Acetic and formic acids

• Polysaccharides

• Oligosaccharides

• Miscellaneous (minor) products

Kraft lignin

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Isolation and characterization of lignin and hemicelluloses from pine kraft black liquor

Three series of kraft cooks conducted: normal (reference, R), slow (low-sulfidity, LS), and fast (high-alkalinity, HA)

Cook H factor Yield, % Kappa

R 30 74.0 -R 1000 50.9 50.6R 2500 45.0 21.8

LS 3000 49.0 49.8HA 350 45.4 45.2

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Applied fractionation of black liquor

Precipitation

Acidification

1. 1,4-dioxane2. Glacial acetic acid

Black liquor

Hemicelluloses

Kraft lignin

pH 2,5

N. Engström et al.,ISWPC 1995, Vol. III, p. 195.

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Total carbohydrates in black liquors

Concentration, g/l 1.7 4.3 3.2 3.1 9.6Isolation yield, % 59 93 34 10 93

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Isolated hemicelluloses

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Distribution of aromatic pyrolysis products

LigninHemi

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

Guaiacyltypestructures

Otheraromatics

0 %

20 %

40 %

60 %

80 %

100 %

0 %

20 %

40 %

60 %

80 %

100 %

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Guaiacyl-type pyrolysis products

0 %

20 %

40 %

60 %

80 %

100 % Coniferaldehydetrans-Coniferyl alcoholcis-Coniferyl alcoholDihydroconiferyl alcohol4-(1-hydroxy-prop-2-enyl)guaiacolGuaiacylacetoneHomovanillin4-(oxy-allyl)guaiacolAcetoguaiaconeVanillintrans-Isoeugenolcis-IsoeugenolEugenol4-Vinylguaiacol4-Ethylguaiacol

4-MethylguaiacolGuaiacol

Hemi Lignin

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

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Non-guaiacyl type pyrolysis products

HydroquinoneCatecholHydroxybenzaldehyde4-Methylphenol2-MethylphenolPhenol

0 %10 %20 %30 %40 %50 %60 %70 %80 %90 %

100 %Hemicellulose Lignin

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

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Carbohydrates in the isolated kraft lignins

Amount, % 1.0 4.0 2.5 9.2 2.7

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Sulfur in the isolated kraft lignins

0,0

0,5

1,0

1,5

2,0

2,5

3,0 Sulphur, %

R160H30

LS160H3000

HA180H350

R160H1000

R160H2500

Is the nature of black liquor sulfur known?

• Some evidence for the presence of methylthio groups

• S-bearing lignin monomers identified by GC/MS from black liquors

Ar-S-Me type compounds

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Analysis of hydroxy carboxylic acids

• GC and GC/MS

- TMS derivatives after converting the

acids into their ammonium salts

- TMS derivatives of free acids + lactones

• Capillary electrophoresis

- limited availability of standards

- not suitable for polyhydroxy acids

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Main hydroxy monocarboxylic acids

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GC analysis of the main hydroxy acids

4 = 2-hydroxybutanoic acid18 = 2,4-dihydroxybutanoic acid27 = xyloisosaccharinic acid

min

Lignin-carbohydrate acids

Fatty acids

Resin acids

Dilignols

Main carbohydrate-derived acids

GC/MS analysis of black liquors

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Dimeric acids from galactoglucomannans

Stable link

Labile links

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Dimeric acids from galactoglucomannans

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Condensed conclusions

There is still a lot of by-product potential in black liquors