ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 1, pp. 148!152. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + S.V. Frolova, V.A. Demin, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 1, pp. 152!156.
AND POLYMERIC MATERIALS
Degradation of Wood Cellulose with Lewis Acids with the Aim
to Prepare Powder Cellulose
S. V. Frolova and V. A. Demin
Institute of Chemistry, Komi Scientific Center, Ural Division, Russian Academy of Sciences, Syktyvkar,
Komi Republic, Russia
Received May 2, 2007
Abstract-The influence of various factors on degradation of wood cellulose with Lewis acids was studied.
The physicochemical characteristics of the resulting products were analyzed.
Reactions of monosaccharides catalyzed by Lewis
) are well studied and widely used .
In chemistry of polysaccharides, Lewis acids are used
less extensively. They are mainly used as highly ef-
fective catalysts for cellulose degradation. Previously
[2, 3] conversion of cotton cellulose in the presence
of Lewis acids was studied and possible application
fields for the synthesized powder celluloses were out-
lined. The use of water-free procedures is a promis-
ing pathway for production of powder celluloses.
The use of organic solvents in the course of the reac-
tion and their subsequent regeneration allows a de-
crease in the expenditure of pure water and in the
volume of wastewaters.
Wood cellulose differs from cotton cellulose by the
presence of residual hemicelluloses and lignin. It is
used for production of powder cellulose for technical
purpose. For this purpose, it is degraded in an aqueous
medium at a high liquid-to-solid ratio and an excess
of sodium hypochlorite. The use of Lewis acids and
anhydrous media for production of powder celluloses
can essentially improve the product purity. The use of
wood raw materials for this purpose can significantly
reduce the cost of the process and impart new proper-
ties to the cellulose material.
Here we studied the influence of various factors on
degradation of wood cellulose with the use of Lewis
acids and analyzed physicochemical characteristics of
the resulting products.
The object of the study was deciduous kraft
bleached cellulose produced by the Syktyvkar Timber
Industry Association, Joint-Stock Company. Before
treatment, the cellulose was separated into single
fibers to provide the highest homogeneity in size. Alu-
minum chloride, aluminum bromide, and titanium
tetrachloride were used as Lewis acids (MX
were synthesized by the standard procedure
. Before use, the sample stored for more than one
year was purified by sublimation at atmospheric pres-
sure. The sample stored for more than two years was
purified by simple distillation. To prepare TiCl
used commercial titanium tetrachloride of pure grade,
which was purified by simple distillation at atmos-
pheric pressure . The reaction was performed in
anhydrous organic solvents (carbon tetrachloride, hex-
ane, and ethanol) at their boiling points. A weighed
portion of cellulose dried at 105oC was placed into
a conical flask and poured over with a solution of
freshly prepared Lewis acid for a certain period of
time. Aluminum chloride: a 1.99-g weighed portion of
cellulose was treated with 50 ml of 0.13 0.005% solu-
tion in CCl
. Titanium chloride: a 1.65-g weighed
portion of cellulose was treated with 100 ml of 1.0 3
0.005% solution in CCl
. Depending on the concen-
tration of Lewis acid in the solution, the weight ratio
: cellulose was from 1 : 2.5 to 1 : 500 (Table 1).
After a lapse of time, cellulose was transferred onto
a glass frit, the solution was filtered, and the residual
catalyst was washed out with the same solvent, in-
cluded with ethanol, and dried in an oven. The degree
of degradation was judged from variation of the aver-
age degree of polymerization (DP) of the samples
determined from their viscosity in aqueous solutions
of Cadoxen .
In the experiments we varied the concentration
of Lewis acids, treatment duration, weight ratio