2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P24 DETERMINATION OF VOLATILE
COMPOuNDS AND SACChARIDES AT ALDER
wOOD hyDROLySIS
FRAnTIŠEK KAČíK a , MARTA LAUROVá a and
DAnICA KAČíKOVá b
a Department of Chemistry and Chemical Technologies,
b Department of Fire Protection,
Faculty of Wood Sciences and Technology, Technical University
in Zvolen, T. G. Masaryka 24, 960 53 Zvolen, Slovak
Republic,
kacik@vsld.tuzvo.sk
Introduction
A pretreatment of lignocellulosic biomass at the production
of pulp, ethanol and other technically important chemicals,
is a subject of research for a long time. The pretreatment
main goal is to remove lignin and hemicelluloses, to decrease
celullose crystallinity and to increase porosity of the lignocellulosic
material. The various physical, physico-chemical an
biological processes of pretreatment are used for this purpose
at present 1,2 .
One method is a high-pressure water prehydrolysis. It is
realized at a wide range of temperatures (160–260 °C), but in
the short time intervals (0.42–7 min) in dependence on wood
species 3 .
The hydrothermal pretreatments of lignocellulosic materials
have got a different effect on their main components.
Extractives, hemicelluloses and watersoluble lignin are released
from wood in the temperature range 150–230 °C. The
cellulose fraction depolymerises at the higher temperatures
(210–280 °C) 3,4 .
At wood hydrolysis also other compounds arise except
saccharides. They can be processed (methanol, acetic acid,
propionic acid, 2-furaldehyde), resp. their negative environmental
influence must be solved 5 . Their concentration in the
hydrolysates depends on wood species and the hydrolysis
conditions, mainly on the temperature and the time of the
treatment.
The water prehydrolysis of biomass (by saturated water
steam and hot high-pressure water) can be considered as a
environmentally friendly technology, where it is not necessary
to add any chemicals 6 .
This paper aim was to research the release of saccharidic
part and volatile compounds from alder wood (Alnus glutinosa
(L.) GAERTn.) during the water hydrolysis.
Experimental
M a t e r i a l
wood samples preparation
The samples from the trunk wood of 59 years old alder
(Alnus glutinosa (L.) GAERTn.) were chipped to the dimensions
2 × 2 × 10 mm.
s383
wood analyses
The amount of extractives soluble in the mixture toluene-ethanol
(1 : 2) was determined in accordance with ASTM
Standard D 1107-96 7 , the amount of cellulose by Seifert
method 8 and the amount of holocelluse by Wise method 9 .
Lignin amount was determined in accordance with ASTM
Standard D 1106-96 10 .
H y d r o l y s i s
Wood chips (2 g) were put into the stainless autoclaves
with internal volume 12 cm 3 and they were refilled by distilled
water. The solid/liquor ratio was 1 : 4.
The prehydrolysis was performed in the thermostate at
the temperatures 160, 180 and 200 °C. The time of treatment
was 30, 60, 120 and 240 min. Then the autoclave was cooled
into the temperature 20 °C and the hydrolysate was filtrated.
H y d r o l y s a t e s A n a l y s e s
ph value
Hydrolysates pH values were determined by the potenciometric
method with pH meter inoLab pH 720 (WTW
GmbH).
Saccharides
Saccharides amount in the hydrolysates was determined
in the form of aldonitrilacetates by GC method 11 at the
following conditions: column – 5 % PEGA Chromaton n-
AW-DMCS (0.16–0.2 mm) 240 cm × 0.35 cm, column temperature
– 200 °C, injector temperature – 260 °C, detector
temperature – 250 °C, detector – FID, carrier gas – n 2 .
Volatile compounds
The volatile compounds in the hydrolysates (methanol,
acetic acid, propionic acid, 2-furaldehyde) were determined
by the method of GC 12 at the following conditions: column
– Chromosorb 102 (80–100 mesh) 120 cm × 0.35 cm, column
temperature – 195 °C, injector temperature – 250 °C, detector
temperature – 250 °C, detector – FID, carrier gas – n 2 .
Results
During the hydrothermal treatment of wood, various
acid compounds are released. It is confirmed by the measured
values of pH (Table I). The increase of the hydrolysates
acidity causes next degradation of wood matter and the glycosidic
bonds in the polysaccharides are cleavaged.
The hydrolysates acidity is due to the formation of socalled
nascent organic acids (formic, acetic, propionic e.g.),
which are formed by the cleavage of some functional groups
from the polysaccharides and also by the decomposition of
arised monosaccharides. These acids have got an important
influence on the next course of the hydrolysis, therefore they
catalyse the glycosidic bond cleavage in the polysaccharides
13,14 .
The used alder wood contained 84.06 % of holocellulose,
41.26 % of cellulose, 21.45 % of lignin and 4.97 % of
extractives.