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INTEGRATED POSSIBILITIES OF PRODUCING CHEMICALS AND BIOFUELS
IN CHEMICAL PULPING
International Forest Biorefining Conference (IFBC) May 9-11, 2017, Thunder Bay, ON, Canada
Raimo Alén
University of Jyväskylä, Finland Laboratory of Applied Chemistry
OUTLINE
GENERAL ASPECTS
PRETREATMENT OF WOOD CHIPS – Acidic and
alkaline conditions
BY-PRODUCTS OF KRAFT PULPING – Lignin,
aliphatic carboxylic acids, and extractives
BY-PRODUCTS OF OTHER PULPING METHODS
CONCLUSIONS
GENERAL ASPECTS
”RAW MATERIAL AGES”
(Mabee & Saddler, 2008)
BIOREFINERY CONVERSION
METHODS
PHYSICAL UPGRADING METHODS (drying,
pulverisation, briquetting, and pelletizing)
CHEMICAL AND BIOCHEMICAL METHODS
(hydrolysis followed by fermentation or chemical
conversion)
THERMOCHEMICAL METHODS (torrefaction,
pyrolysis, gasification, liquefaction, and combustion)
OTHER METHODS (e.g., production of composites or
fractionation followed by chemical conversion - cellulose
derivatives)
PROCESS SCHEME FOR THE CONVERSION OF
BIOMASS-DERIVED CARBOHYDRATES
PRODUCT GROUPS FROM THERMAL
CONVERSION OF CELLULOSIC BIOMASS
PRINCIPAL CONVERSION ROUTES FOR
CELLULOSIC BIOMASS TO PRODUCE
VARIOUS ENERGY SOURCES
INTEGRATED BIOREFINERY
CONCEPT
The first industrial bio-
refineries were operated in the pulp
and paper industry already about
160 years ago
From forest to paper
BIOREFINERY CONCEPTS
BIOMASS
•Wood
•Non-wood crops
(agricultural residues)
•Natural-growing
plants
Chemical and thermochemical conversion techniques
Energy •Electricity
•Heat
•Biodiesel
Chemicals •Ethanol •Other chemicals
Pulping (alkaline process)
Pretreatment (acidic or alkaline)
•Carbohydrates
•Other materials
By-product recovery Extractives
Black liquor • Energy • Chemicals
FIBER
PRINCIPLES FOR THE INTEGRATED PRETREATMENT PROCESS
• FIBER IS THE MAIN PRODUCT
• EFFICIENT RECOVERY OF COOKING CHEMICALS AND EXTRACTIVES
• SULFUR-FREE NOVEL BY-PRODUCTS
• SUITABLE BALANCE BETWEEN THE CARBOHYDRATE AND LIGNIN DEGRADATION PRODUCTS
• STRAIGHTFORWARD SEPARATION TECHNIQUES
• VERSATILE MODIFICATION POSSIBILITIES
COMMERCIAL PULPING
METHODS ____________________________________________________________________________________
Method Yield (% of wood)
____________________________________________________________________________________
Chemical pulping 35-60
Kraft, polysulfide kraft, prehydrolysis kraft
Soda-anthraquinone (AQ)
Acid sulfite, bisulfite, AQ alkali sulfite
Multistage sulfite
Semichemical pulping 65-85
Neutral sulfite semichemical (NSSC)
Soda
Chemimechanical pulping 80-90
Chemithermomechanical (CTMP)
Chemigroundwood (CGWP)
Mechanical pulping 91-98
Thermomechanical (TMP)
Refiner mechanical (RMP)
Stone groundwood (SGWP)
Pressure groundwood (PGWP)
____________________________________________________________________________________
KRAFT PULPING
Chemical pulping accounts for 70 % of the total
worldwide production
Currently about 90 % of chemical pulps (about
130 million tons) are produced by the kraft
(sulfate) process
White liquor – containing mainly the active
cooking chemicals NaOH and Na2S – is used for
cooking the chips
BASIC PRINCIPLES OF TYPICAL PRETREATMENT
STAGES IN KRAFT PULP MILL
Typical pre-treatment phases in the alkaline
delignification
PRETREATMENT OF WOOD
CHIPS
Acidic conditions
ACIDIC PRETREATMENTS
AUTOHYDROLYSIS
(only with H2O)
HYDROLYSIS WITH AQUEOUS
MINERAL ACIDS
(mainly with H2SO4)
CHEMICAL COMPOSITION OF BIRCH- AND
PINE-BASED HYDROLYSATES
(% of the initial dry matter)
___________________________________________________________
Component Birch Pine
___________________________________________________________
Carbohydrates 12.7 9.6
Monosaccharides 1.4 1.8
Oligo- and polysaccharides 11.3 7.8
Uronic acids 0.4 0.6
Furans 0.1 0.1
Volatile acids 1.6 0.5
Acetic acid 1.5 0.4
Formic acid 0.1 0.1
Lignin 2.1 1.1
Total 16.9 11.9
___________________________________________________________The chips are treated at 150 oC for 90 min (liquor-to-wood ratio 5 L/kg)
PRETREATMENT OF WOOD
CHIPS
Alkaline conditions
THE FIRST PHASE OF ALKALINE (KRAFT) PULPING
• A RATHER LOW SELECTIVITY
→ AN INTENSE ALIPHATIC ACID FORMATION COMPARED TO THE LIGNIN DISSOLUTION
• MOST OF THE EXTRACTIVES ARE REMOVED
→ TURPENTINE
→ SAPONIFICATION OF ESTERS
( → FATTY AND RESIN ACIDS)
→ NEUTRAL SUBSTANCES
(”NONSAPONIFIABLES”)
Behavior of the major wood components during kraft pulping of pine
(Aurell, R. & Hartler, N., Svensk Papperstidn. 68(3)(1965)59-68)
MAIN REACTIONS OF POLYSACCHARIDES IN ALKALINE PULPING - 1
MAIN REACTIONS OF POLYSACCHARIDES IN ALKALINE PULPING -2
THE SOLUBLE DRY MATTER FORMED DURING
THE ALKALINE PRETREATMENT OF BIRCH
(% of the initial dry matter) (Lehto, J. & Alén, R., J. Wood Chem. Technol. 33(2)(2012)77-91)
____________________________________________________________________
Component 6(b) 8(b)
____________________________________________________________________
Aliphatic carboxylic acids 7.4 9.1
Volatile acids(c) 5.3 6.0
Hydroxy acids(d) 2.1 3.1
Lignin 2.5 3.5
Other organics(e) 2.4 3.5
Total 12.3 16.1
____________________________________________________________________
(a) - The chips are treated at 150 oC for 90 min (liquor-to-wood ratio 5 L/kg); (b) - alkali charge
(% of NaOH on o.d. feedstock); (c) - acetic and formic acids; (d) - mainly glycolic, lactic, 2-
hydroxybutanoic, 3,4-dideoxy-pentonic, 3-deoxy-pentonic, xyloisosaccharinic, and glucoiso-
saccharinic acids; and (e) - mainly extractives and carbohydrates
Alkali charge,
% of NaOH on wood
8 10
Pine Birch Pine Birch
Mass ratio 2.2 2.2 2.3 1.8
aliphatic acids/lignin
Residual alkali,
g/L 1.8 0.4 2.8 2.0
pH (after treatment) 11.0 10.0 11.9 11.0
SOME PARAMETERS OF THE ALKALINE PRETREATMENTS
(30 min, 150 oC (pine) or 160 oC (birch))
Fraction Pine Birch
Aliphatic acids 88,100 83,700
Volatile acids 37,000 45,200
Hydroxy acids 51,100 38,500
Lignin 40,200 38,200
Extractives 39,100 24,000
Total 167,400 145,900
aCalculated for an annual production of 500,000 o.d. tons of
unbleached pulp.
Estimated production (tons/year) of the organic fractions formed during the alkaline pretreatments
(8 % NaOH on wood/30min/150 oC)a
TREE 100
PRETREATMENT (acid or alkali)
Energy Chemicals (e.g., ethanol)
Energy (elecric power,
steam)
HARVESTING RESIDUES
and BARK
47
CONVERSION
i) BURNING ii) GASIFICATION iii) CHEMICAL
TREATMENT
SYNTHESIS GAS
FT-PROCESS Liquid fuel Chemicals
SPENT LIQUOR
RECOVERY PROCESSES
15 - 20 % Energy (diesel fuels)
Organic fractions
Cooking chemicals
Cooking chemicals
30 - 35 %
FIBER 25
DELIGNIFICATION
i) KRAFT ii) SODA-AQ iii) O2/alkali
BLACK LIQUOR
RECOVERY FURNACE
Energy
50 %
BY-PRODUCTS OF KRAFT
PULPING
Black liquor - general
WOOD
(100)
%
Cellulose 40 - 45
Hemicelluloses 25 - 35
Lignin 20 - 30
Extractives < 5
%
Cellulose 60 - 75
Hemicelluloses 20 - 30
Lignin < 5
BLACK LIQUOR
(40 - 50)
%
Aliphatic acids 40 - 45
Lignin 35 - 45
Other organics 10 - 15
OXYGEN-DELIGNIFIED
and BLEACHED PULP
(40-50)
ORGANICS
(5)
%
Cellulose 80 - 85
Hemicelluloses 15 - 20
Lignin -
EXTRACTIVES
(< 5)
UNBLEACHED PULP
(45 - 55)
COMPOSITION OF THE DRY MATTER OF
BIRCH AND PINE KRAFT BLACK LIQUORS
(% of the total dry matter) ______________________________________________________________________
Component Birch Pine
______________________________________________________________________
Lignin 25 31
Aliphatic carboxylic acids 33 29
Volatile acids(a) 12 10
Hydroxy acids(b) 21 19
Other organics 9 7
Extractives 3 4
Carbohydrates(c) 5 2
Miscellaneous 1 1
Inorganics(d) 33 33
______________________________________________________________________
(a) - Acetic and formic acids; (b) - mainly glycolic, lactic, 2-hydroxybutanoic, 3,4-dideoxy-
pentonic, 3-deoxy-pentonic, xyloisosaccharinic, and glucoisosaccharinic acids; (c) - mainly
hemicellulose-derived fragments; and (d) - including the sodium bound chemically to organics
COMPOSITION OF THE DRY MATTER OF PINE AND BIRCH KRAFT
BLACK LIQUORS AND ALKALINE BIRCH HYDROLYSATE
(% of the total dry matter) _______________________________________________________________
Component Pine(a) Birch(a) Birch(b)
_______________________________________________________________
Lignin 31 25 16
Aliphatic carboxylic acids 29 33 43
Formic acid 6 4 3
Acetic acid 4 8 26
Glycolic acid 2 2 1
Lactic acid 3 3 2
2-Hydroxybutanoic acid 1 5 3
3,4-Dideoxy-pentonic acid 2 2 1
3-Deoxy-pentonic acid 1 1 <1
Xyloisosaccharinic acid <1 4 2
Glucoisosaccharinic acid 7 3 2
Others 2 1 3
Other organics 7 9 16
Inorganics 33 33 25
_______________________________________________________________
(a) - Black liquor and (b) - alkaline pretreatment hydrolysate (8 % NaOH, 150 oC, 90 min)
MAIN UTILIZATION POSSIBILITIES
COMBUSTION IN THE RECOVERY FURNACE (for
recovering energy and cooking chemicals)
GASIFICATION (for recovering energy and cooking
chemicals as well as for producing chemicals)
RECOVERY OF ORGANIC FRACTIONS (for making
fuels and chemicals)
BY-PRODUCTS OF KRAFT
PULPING
Black liquor - lignin
RECOVERY OF LIGNIN
IN PRACTICAL APPLICATIONS, IT IS
ADVANTAGEOUS TO USE CO2 FROM FLUE GAS
(pH → 9.5, yield ≈35 %) FOLLOWED BY THE USE OF
PURE CO2 UNDER PRESSURE (pH → ≈ 8) (at 80 oC,
<20 atm, total yield ≈75 %)
THE LIBERATION OF PHENOLIC HYDROXYL
GROUPS (pKa 9-11) TAKES PLACE → LIGNIN
PRECIPITATES
pKa VALUES OF CARBOXYLIC ACIDS ARE 3-5
SOME PRACTICAL DATA (Alén, R., Patja, P. & Sjöström, E., Tappi 62(11)(1979)108-109; Alén, R.,
Sjöström, E. & Vaskikari, P., Cellulose Chem. Technol. 19(1985)537-541)
TAPPI
SOME PRACTICAL DATA (Alén, R., Patja, P. & Sjöström, E., Tappi 62(11)(1979)108-109; Alén, R.,
Sjöström, E. & Vaskikari, P., Cellulose Chem. Technol. 19(1985)537-541)
INFLUENCE ON THE HEATING VALUE
OF BLACK LIQUOR
HEATING VALUES: Black liquor (15-35 % water and
25-40 % inorganics, and about 45 % organics) 12-15
MJ/kg d.s.; lignin 22-27 MJ/kg; aliphatic carboxylic acids
5-18 MJ/kg; and extractives about 35 MJ/kg
DECREASES IN HEATING VALUE (MJ/kg d.s.): 5-10
% (precipitated lignin yield 35 %) and 15-25 %
(precipitated lignin yield 75 %)
BEHAVIOR OF COMBUSTION PROPERTIES:
Carbonated black liquors swell clearly less than untreated
black liquors
SOME UTILIZATION POSSIBILITIES OF THE PRECIPITATED LIGNIN
•PHENOLIC RESINS
•POLYURETHANES
•PHENOLS (AND CARBON FIBER)
•FUEL PURPOSES
BY-PRODUCTS OF KRAFT
PULPING
Black liquor – aliphatic
carboxylic acids
Schematic representation of a possible black liquor
fractionation process
One of the process alternatives (Alén and Kumar 2016)
THE MAIN ALIPHATIC CARBOXYLIC
ACIDS OF BLACK LIQUOR
UTILIZATION POSSIBLITIES OF
ALIPHATIC CARBOXYLIC ACIDS
ONLY A MINOR PROPORTION OF ALIPHATIC
CARBOXYLIC ACIDS CAN BE UTILIZED AS SUCH
IN THE FORM OF THEIR SODIUM SALTS (→ their
liberation, pKa values 3-5)
REALISTIC FRACTIONS:
– ”VOLATILE ACIDS” including formic and acetic acids
– ”LOW-MOLAR-MASS HYDROXY ACIDS” (with 2-4 carbon
atoms) including glycolic, lactic, and 2-hydroxy-butanoic
acids
– ”HIGH-MOLAR-MASS HYDROXY ACIDS” (with 5 and 6
carbon atoms) including 3,4-dideoxy-pentonic, 3-deoxy-
pentonic, and xylo- and glucoisosaccharinic acids
UTILIZATION POSSIBLITIES OF
ALIPHATIC CARBOXYLIC ACIDS
LIBERATION WITH MINERAL ACIDS
(mainly with H2SO4) OR ELECTRODIALYSIS
FRACTIONATION AND PURIFICATION BY
VACUUM DISTILLATION (0.067-0.173 kPa)
OR ION-EXCLUSION CHROMATOGRAPHY
UTILIZATION POSSIBLITIES OF
ALIPHATIC CARBOXYLIC ACIDS
FORMIC, ACETIC, GLYCOLIC, AND LACTIC ACIDS
ARE COMMERCIALLY IMPOPRTANT CHEMICALS
BY REDUCTION (i.e., the production of polyalcohols)
BY OXIDATION (i.e., the production of polycarboxylic
acids)
BY ESTERIFICATION (i.e., the production of emulsi-
fying agents)
BY OTHER METHODS (e.g., the production of various
polyesters or a wide range of derivatives)
CONDENSATION OF ”LOW-MOLAR-MASS” ACIDS (Alén, R. & Sjöström, E., Acta Chem. Scand. B 34(1980)633-636)
BY-PRODUCTS OF KRAFT
PULPING
Black liquor - extractives
CRUDE TALL OIL (CTO)
TALL OIL SOAP → the removal from the evaporated
black liquor by skimming → the liberation of carboxylic
acids (resin and fatty acids) with H2SO4 → CTO (the
average yield 30-50 kg/ton of pulp, corresponding to 50-
70 % of the initial amount)
PURIFICATION AND FRACTIONATION BY
VACUUM DISTILLATION (3-30 mBar, 170-290 oC):
– LIGHT OIL 10-15 %
– FATTY ACIDS 20-40 %
– ROSIN 25-35 %
– PITCH RESIDUE 20-30 %
UTILIZATION OF CRUDE TALL OIL
SOAP – AN INTERESTING NEW
APPROACH
PRODUCTION OF BIODIESEL BY PYROLYSIS
PRODUCTION OF Na2CO3 (no external H2SO4 is
needed)
NOTE ALSO VOLATILE TURPENTINE (5-10 kg/ton
of pulp)
PYROGRAM OF TALL OIL SOAP (at 750 oC for 20 s) (Lappi, H. & Alén, R., BioResources 6(2011)5121-5138)
The main products formed in the pyrolysis experiments (700 oC and 20 s)
with hot-water-extracted birch sawdust (left) and with soda-AQ-
delignified pulp from hot-water-extracted birch sawdust (right). Letters
indicate compound groups to which identified products belong: A
(anhydrosugar derivatives), B (benzene derivatives), C (cyclopentenone
derivatives), E (catechol and benzenediol derivatives), F (furan
derivatives), G (guaiacol derivatives), I (indene derivatives), L (lactone
derivatives), N (naphthalene derivatives), P (phenol derivatives), S
(syringol derivatives), X (fatty acids derivatives), and Y (pyrone
derivatives). Ghalibaf et al. 2017
”Liquefaction” of black liquor McKeough, Alén, Oasmaa & Johansson, Holzforschung 44(1990)445-448
BY-PRODUCTS OF OTHER
PULPING METHODS
THE MAIN METHODS
ACID SULFITE PULPING
VARIOUS ORGANOSOLV METHODS
COMPOSITION OF BIRCH AND SPRUCE
ACID SULFITE SPENT LIQUORS (kg/ton pulp)
_____________________________________________________________
Component Birch Spruce
____________________________________________________________
Lignosulfonates 435 510
Carbohydrates 380 270
Monosaccharides 305 215
Oligo- and polysaccharides 75 55
Aliphatic carboxylic acids 130 70
Acetic acid 75 30
Aldonic acids 55 40
Extractives 40 40
Others 55 30
_____________________________________________________________
ORGANOSOLV PULPING
Pulping in the presence of organic solvents (”organosolv
methods”) dates back to the beginning of the 1930s (T.N.
Kleinert)
Was not considered seriously for practical use until in the
1980s
For both woods and non-woods
The most important solvents include alcohols (e.g.,
methanol and ethanol), aliphatic carboxylic acids (e.g.,
formic and acetic acids), phenols (e.g., phenol and cresol)
and many other systems also in the presence of alkaline or
acidic catalysts
SIMPLIFIED FLOWCHART OF ORGANOSOLV
PROCESSES
CONCLUSIONS
• PRETREATMENT OF WOOD CHIPS UNDER VARYING CONDITIONS OFFERS AN INTERESTING APPROACH FOR MAKING BIOPRODUCTS
• BLACK LIQUOR ORGANICS REPRESENT A HUGE
AMOUNT OF RENEWABLE RAW MATERIAL AND THE PARTIAL RECOVERY OF THESE FRAGMENTS
SEEMS ATTRACTIVE (AND TECHNICALLY POSSIBLE)
• THERE ARE SOME POTENTIAL UTILIZATION POSSIBILITIES FOR ALL THESE BY-PRODUCTS
(CAN THESE PRODUCTS BE MARKETED?)
