Pretreatment of different materials an international perspective
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Pretreatment of different materials: An international perspective . Mohammad J. Taherzadeh School of Engineering University of Borås. A variety of lignocelluloses are attractive in different reagions!. Complex plants cell walls. A challenge by lignin and hemicellulose!. Hemicellulose.

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Pretreatment of different materials: An international perspective

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Pretreatment of different materials an international perspective

Pretreatment of different materials: An international perspective

Mohammad J. Taherzadeh

School of Engineering

University of Borås

A variety of lignocelluloses are attractive in different reagions

A variety of lignocelluloses are attractive in different reagions!

Complex plants cell walls

Complex plants cell walls

A challenge by lignin and hemicellulose

A challenge by lignin and hemicellulose!



Cellulose chains

Challenge of crystallinity

Challenge of crystallinity!

Alternative patterns of aggregation

Alternative patterns of aggregation

Helical form of a 6 by 6 nm nanofibrils is compared with that of nine 2 by 2 helical nanofibrils packed as close as possible, with the same period.

The fibrils were twisted individually and then the assembly also twisted.

The individual fibrils were twisted of 90°over 300 nm and then packed as closely as possible

The fibrils were collectively subjected to twist.

Alternative patterns of aggregation1

Alternative patterns of aggregation

Cellulose is deposited alone

The most efficient load-bearing structure

Would not be mechanically stable

Changes during isolation

Changes during Isolation

  • Twostages in isolation willinfluence the final pattern of aggregation:

  • Elevation of temperature

  • Effect of drying

Effects of elevated temperature

Effects of elevated temperature

  • Cellulose is hydrated in its native state at the level of elementary nanofibril

Temperature elevation changes the state of aggregation of native cellulose.



Drying results in distortion of nanofibrils by:

Removing too much of the water needed to lubricate the motion of the nanofibrils relative to each other.

Changes during isolation1

Changes during Isolation

  • Linear parallel segments, which are artifacts of isolation processes are easily mistaken for naturally accuring crystalline domains.

Pretreatment in order to

Pretreatment in order to:

  • Release cellulose from the structure:

    • Remove or hydrolyze hemicelluloses

    • Remove lignin

  • Reduce cellulose crystallinity

  • Provide enough accessible surface area to absorb the enzymes

  • Adsorption/desorption rates of the enzymes

  • Remove inhibitory compounds following the substrate

Pretreatment methods various efficiency on different factors

Pretreatment methods (various efficiency on different factors)

Cellulose solvents effective for crystallinity

Cellulose solvents effective for crystallinity

Possible non aqueuous cellulose solvents

Possible non-aqueuous cellulose solvents

Low temperature ionic liquids 80 130 c

Low-temperature Ionic Liquids (80-130 C)

Imidazole salts

Milling usually part of the process

Milling: Usually part of the process!

  • Milling:

    • Ball milling

    • Two-roll milling

    • Hammer milling

    • Colloid milling

    • Vibro energy milling

  • Functions:

    • Size reduction

    • Degree of crystallinity

  • High energy costs!



  • irradiation:

    • Gamma-ray irradiation

    • Electron-beam irradiation

    • Microwave irradiation

  • Usuallygoodresults

  • Expensive!

  • Ultrasound mighthave a good a chance for commercialization(already in the market)

Hydrothermal process

Hydrothermal process

  • Cooking in liquid hot water generally at 150-210 °C

  • Water under high pressure can:

    • Penetrate into the biomass,

    • Hydrate cellulose,

    • Remove hemicellulose (a major function),

    • Remove part of lignin (but not so effective),

  • Autohydrolysis occur due to releasing some carboxylic acids such as acetic acid,

  • Advantages:

    • No addition of chemicals,

    • No neutralization afterward,

    • No corrosion-resistant materials for reactor,

    • Could be combined with e.g. a delignification process

  • Industrial application such as by Danish Inbicon

High pressure steaming explosion

High-pressure steaming (+explosion)

  • Cooking with steam generally at 150-220 °C & 0.5-20 min

  • If followed by explosive releasing of the pressure = Steam explosion

  • Steam explosion is one of the most popular pretreatments

  • Explosion has important function

  • pH reduces due to autohydrolysis

  • Industrtial applications by e.g.

    • Cambi (Norway)

    • Chemtex (Italy)

    • Greenfield (Canada)

Dilute acid processes

Dilute-acid processes!

  • Similar methods in pulp industries

  • Similar temperature/Pressure as steam explosion!

  • Improvement by addition of:

    • Dilute-acid (0.1-1% acids: H2SO4, HCl, etc.)

    • Carboxylic acids (e.g. acetic acid)

    • 1-4% SO2

    • CO2

  • Functions:

    • Open up the polymers

    • Hydrolysis of hemicellulose

  • Potential commercialization by e.g :

    • POET (USA)

    • SEKAB (Sweden)


Alkaline cooking

Alkaline cooking!

  • Treatment with alkaline solutions:

    • NaOH,

    • Ca(OH)2 (lime) or

    • Ammonia (AFEX)

  • Popular in pulp industries (kraft process)

  • To remove lignin effectively (+ sometimes a part of the hemicellulose)

  • To reduce crystallinity of cellulose

  • Generally at about 90-130 C for a few minutes to hours

  • High pH (e.g. 11-12) or alkali concentrations 1-20%

  • High amount of NH3 is needed (e.g. 1:1 kg/kg NH3/biomass)

  • Can also be used with explosion

Oxygen treatments wet oxidation

Oxygen treatments (wet oxidation)!

  • Wet oxidation = treatment with water and air or O2 at 140-200 C for e.g. 30 min.

  • It is exothermic process (because of oxidations)

  • It is a combination of solubilization and degradation reactions

  • Hydrolytic reactions  organic acids

  • The hemicelluloses are extensively cleaved to monomeric sugars;

  • The lignins undergo both cleavage and oxidation;

  • Cellulose is partly degraded.

Organosolves ionic liquids

Organosolves/Ionic liquids!

  • Lignocelluloses are mixed with organic liquid (and water?) and heated to dissolve:

    • Ligning

    • And/or cellulose

  • Temperatures of 80-200 °C can be used:

    • Depends on the solvent used!

  • Simple solvents such as ethanol or acetone can be used!

  • Low Temperature Ionic Liquids are hot research topic today!

Our latest results for high crystalline cellulose

Our latest results for high crystalline cellulose!

  • N-Methylmorpholine-N-oxide (NMO or NMMO)

  • No toxicity

  • Solvent of cellulose

  • Industrial solvent

  • 80-130 C



  • Lignocelluloses are diffent:

    • Type,

    • Age,

    • Crystallinity

    • Dryness,

    • Type of the cell wall

    • ….

  • Pretreatments have different effectivities on various lignocelluloses,

  • Great developments in pretreatments, but still long way to go…

Thank you

Thank you!


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