Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 2, pp. 258−265.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © E.I. Evstigneev, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 2, pp. 278−285.
AND POLYMERIC MATERIALS
Oxidation of Hydrolysis Lignin
with Hydrogen Peroxide in Acid Solutions
E. I. Evstigneev
St. Petersburg State University of Forestry Engineering, St. Petersburg, Russia
Received October 23, 2012
Abstract—Optimal conditions were determined for oxidation of hydrolysis lignin and other insoluble lignin
samples with hydrogen peroxide in acid solutions, ensuring solubility of lignin in dilute alkali. The correlation
was found between the functionalization and solubility of hydrolysis lignin and its oxidation products. A procedure
was suggested for determining carboxy groups in lignin.
The problem of utilization of hydrolysis lignin was
and remains urgent. In accordance with the data published
in 1988, about 3.5 × 10
t of hydrolysis lignin is formed
annually as waste at enterprises of hydrolysis industry.
Numerous papers, including patents and monographs [1,
2], deal with solution of this problem, but the suggested
methods for utilization of hydrolysis lignin, with a few
exceptions , have not gone beyond laboratory and
industrial trials. The main factors preventing the develop-
ment of economically feasible and environmentally safe
technology for processing and use of hydrolysis lignin
are its inhomogeneous composition, irregular structure,
and insolubility in common solvents.
Hydrolysis lignin can be transferred into solution
under the conditions of so-called alkaline activation,
i.e., treatment with alkali at high temperature . The
use of such solutions is restricted to reactions in alkaline
medium. Otherwise, it is necessary to recover lignin by
acidiﬁ cation with a mineral acid in the form of a difﬁ cultly
ﬁ lterable precipitate, to thoroughly wash it to remove the
salts formed, and to dry it. In this respect, it seems more
promising to perform oxidation of hydrolysis lignin with
hydrogen peroxide, because the oxidation yields a solid
product soluble in dilute alkali .
Previously we studied the correlation between the
functionalization and solubility of natural (in wood) [5, 6]
and hydrolysis  lignins under the conditions of alkaline
activation. In this study we examined such relationships
in oxidation of hydrolysis lignin in acid solution.
We studied oxidation of hydrolysis lignin (HL) re-
covered from softwood at Bobruisk Hydrolysis Plant
(Belarus). The hydrolysis lignin was washed with water
to pH 7, dried in air, and fractionated on laboratory sieve.
The fraction of size 0.2–0.4 mm was collected; it was
extracted with ethanol in a Soxhlet apparatus for 15 h.
A temperature-controlled cell with a magnetic stirrer
was charged with 20 cm
of an oxidant solution (mixture
of hydrogen peroxide and sulfuric acid of preset compo-
sition), the solution was heated to a preset temperature,
and a weighed portion of HL (1 g, counting on absolutely
dry weight) was added. The oxidation was performed
for different times. After the experiment completion, the
contents were transferred onto a glass frit and washed
with water to neutral reaction with respect to Methyl
Orange. The solubility of the oxidized HL, S
, in a NaOH
solution (40 cm
, 0.2 M) at 70°С was determined by the
procedure described in .
To determine carboxy groups, we modiﬁ ed the Wil-
son’s method traditionally used for analysis of technical-
grade celluloses and oxycelluloses [9, 10]. Preliminary
studies showed that the oxidized lignin is partially soluble