Kinetics and mechanism of autohydrolysis of hardwoods

• Autohydrolysis using water is a promising method to extract hemicelluloses from wood prior to pulping in order to make co-products such as ethanol and acetic acid besides pulp. Many studies have been carried out on the kinetics and mechanism of autohydrolysis using batch reactors. The present study was performed in a continuous mixed flow reactor where the wood chips are retained in a basket inside the reactor. This reactor is well suited to determine intrinsic kinetics of hemicellulose dissolution because the dissolved products are rapidly removed from the reactor, thus minimizing further hydrolysis and degradation of the hemicelluloses in solution. The xylan removal rate follows an S-shaped behavior. GPC analysis of the continuously removed extract shows that the dissolved xylan oligomers have a DP smaller than about 25. Lignin-free xylan oligomers and cellulose oligomers are the major components dissolved in the initial stage of autohydrolysis, while xylan covalently bound to lignin (i.e. an LCC) is the major component removed during the later stage of autohydrolysis. The molecular weight of the dissolved components decreases with time in the second stage. The kinetics of xylan removal are explained in terms of a mechanism based on recent knowledge of the ultrastructure of the cell fibre wall.

Nyckelord

Autohydrolysis

Biorefinery

Continuous mixed batch reactor

Kinetics

Mechanism

Biorefineries

Cellulose oligomers

Co-products

Covalently bound

GPC analysis

Initial stages

Intrinsic kinetics

Kinetics and mechanism

Mixed-flow reactors

Removal rate

S-shaped behavior

Wood chip

Cellulose

Dissolution

Ethanol

Hydrolysis

Lignin

Oligomers

Wood products

Batch reactors

hemicellulose

xylan

acetic acid

bioreactor

degradation

pulp and paper industry

reaction kinetics

ultrastructure

article

batch reactor

hardwood

priority journal

wood

Dissolving

Hemicelluloses

Lignins

Prehydrolysis

Pulps

Reaction Mechanisms

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)