Autohydrolysis Of Hardwoods

Running head: AUTOHYDROLYSIS OF HARDWOODS 1

Autohydrolysis of Hardwoods

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AUTOHYDROLYSIS OF HARDWOODS 2

Autohydrolysis of Hardwoods

This article from Elsevier explores the kinetics as well as mechanisms involved in the

autohydrolysis of the hardwoods. The process of autohydrolysis uses water and is a promising technology

especially in the extraction of hemicellulose from the hardwoods before production of pulp (pulping). The

autohydrolysis process produces pulp alongside other vital co-products such as acetic acid and ethanol.

This article explains the process used in performing kinetic and mechanism analysis for autohydrolysis

using the continuous mix flow reactor. The article contrasts its analysis with the previous work by other

researchers who have been using the batch reactors in the analysis of the kinetics and mechanisms in

autohydrolysis. In the study by (Lawoko & Heiningen, 2010) the hardwood chips are reserved in the

basket secured in the reactor. The study used a well-modeled reactor that was efficient in determining the

intrinsic kinetics of the hemicellulose dissolution. The reactor allowed a quick elimination of the

dissolved products. Therefore, there are minimal chances of the degradation as well as further

hemicellulose hydrolysis inside the solution. The rate of xylan removal assumes an S-shaped pattern. The

GPC analysis for the constant extract elimination shows that dissolved xylan oligomers (Lawoko &

Heiningen, 2010) indicates a lesser DP than nearly 25. The lignin withouth xylan oligomers, as well as

the oligomers of cellulose, constitute the main composition in the dissolved materials at the initial

autohydrolysis stage. However, the xylan-lignin (covalently bonded) makes the major compound

eliminated during the later autohydrolysis stage. The molecular weight of the dissolved compounds

reduces with time during the 2nd autohydrolysis stage.

There has been an increase in the price of the fuel all over the world. The biofuels have been

perceived as one of the most promising solutions to the fuel and energy crisis. However, the conversion of

woody biomass into usable biofuel has been regarded as one of the most challenging issues. Mainly, the

conversion of the structural polysaccharides into fermentable simple sugars (monosaccharides) has been

quoted as the major challenge. The autohydrolysis technique gives a glimpse to the promising technology

for cheaper, safe and efficient production of biofuel as well as the pulp. In the process, the only solvent

AUTOHYDROLYSIS OF HARDWOODS 3

used is steam water. Therefore, the process is cheap and environmentally friendly. Moreover, the acetic

acid is formed as a co-product of the pulp. The ethanoic acid is created from the O-acetyl groups found in

the polysaccharides (Lawoko & Heiningen, 2010) such as cellulose, and it is significant in lowering the

pH of the dissolved extract.

The authors outline a simple and precise experiment for analyzing kinetics and mechanism for the

autohydrolysis of the hardwoods. The raw materials used in the experiment is a combination of southern

hardwood chips obtained from 15% maple, , 35% oak, 3% southern magnolia ,12% sycamore and poplar,

and 35% sweet & black gum. After air-drying the chips, the continuous mixed batch system was used

extraction of the products. The lignin extraction followed a zero order reaction while the xylan removal

followed an S-shaped behavior. The xylan and lignin removal is much higher in the CMBR (Continuous

Mixed Batch Reactor) system than in other initial methods. Therefore, this article illustrates a more

efficient production of biofuel from hardwoods as opposed to the previous studies.

The article is characterized with two significances; first, it solves the challenge of extracting the

biofuel from the structurally complex hardwood components. Secondly, the author illustrates the process

of autohydrolysis which uses the cheap, and environmentally friendly raw materials. For instance,

steamed water is used as the major solvent; the rate of pollution is reduced. A future experiment derived

from this experiment may target the reduction of the extraction time or methods of increasing the

percentage yield of the biofuel products in the CMBR system. The article is significant to the class of

‘Chemical Reactor Engineering’ since it illustrates the function and components of the CMBR system.

Moreover, the article involves several analysis of the chemical composition of the products after

autohydrolysis of the hardwoods. Therefore, it gives an idea of the efficiency of the CMBR system in

extraction of biofuel from the hardwoods.

AUTOHYDROLYSIS OF HARDWOODS 4

References

Lawoko, M., & Heiningen, A. v. (2010). Kinetics and Mechanisms of autohydrolysis of hardwoods.

Elsevier, 7812–7819.

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