Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 2, pp. 320−327.
Pleiades Publishing, Ltd., 2010.
Original Russian Text
I.V. Sumerskii, S.M. Krutov, M.Ya. Zarubin, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 2, pp. 321−328.
AND POLYMERIC MATERIALS
Humin-Like Substances Formed under the Conditions
of Industrial Hydrolysis of Wood
I. V. Sumerskii, S. M. Krutov, and M. Ya. Zarubin
Kirov St. Petersburg State Academy of Forestry Engineering, St. Petersburg, Russia
Abstract—Pathways of formation of humin-like substances from carbohydrates and furan compounds under the
conditions of acid hydrolysis of wood were studied.
Processing of vegetable raw materials with the aim
to obtain various organic substances is an important
direction of applied chemistry. Acid hydrolysis is
one of the main processes in treatment of renewable
raw materials. Hydrolysis production is based on
decomposition of vegetable raw materials (ﬁ nely
divided wood) in the presence of a catalyst, dilute
sulfuric acid (0.4–0.7%), at 170–190°С, followed
by processing of the resulting hydrolyzate to obtain
valuable products (ethanol, furfural, forage yeast,
etc.). The monosaccharides formed by hydrolysis can
undergo further multistep transformations under the
above conditions to form furan compounds, which can
undergo further condensation with the formation of
so-called humin-like substances (HLSs) [1–3]. Lignin
can also participate in HLS formation reactions, with
the formation of so-called lignohumic substances. The
furan compounds and lignohumic substances formed
in further reprocessing of the hydrolyzate exert a fatal
effect on the yeast metabolism [4, 5]. Today there are no
technologies for preparing hydrolyzate free of furfural
or lignohumic substances. At some enterprises, furfural
is only partially removed by repeated evaporation of the
hydrolyzate, and the content of lignohumic substances
is decreased by dilution of the wort with water [4, 5].
HLS formation takes place also in furfural production.
Because of side reactions of pentoses and secondary
transformations of furfural, the maximal yield of the
target product, furfural, does not exceed 55%.
Because HLSs negatively affect the quality of
substrates and yeasts, the results of this study can be
used for optimizing the conditions of hydrolysis of
wood raw materials.
In this study we examined the nature and possible
pathways of HLS formation from monosaccharides,
disaccharides, and furan compounds under the conditions
of industrial hydrolysis of wood.
To study the HLSs formed, we performed acid
cookings of individual monosaccharides, disaccharides,
and furan compounds under the conditions similar to
those of an industrial process of acid hydrolysis of wood
, 2 h, 175–180°С). The purity and structure
of all the examined compounds were conﬁ rmed by
gas chromatography–mass spectrometry (GC–MS)
and nuclear magnetic resonance (NMR) [6–8]. Acid
cookings were performed in ~20-ml steel autoclaves
at a solid-to-liquid ratio of 1 : 20 (~5% solution). After
cooling to 20°С, the contents were transferred onto
a paper ﬁ lter. The separated ﬁ ltrate was neutralized with
a 20% NaOH solution, and the precipitate on the ﬁ lter
(mixture of HLSs) was washed with water and dried at
room temperature in a vacuum desiccator to constant
weight. The dried precipitate was weighed and washed
with acetone (~30 ml) until the brown coloration of the
ﬁ ltrate disappeared, to separate a mixture of HLSs into
acetone-soluble and acetone-insoluble fractions. The
acetone-soluble fraction of HLSs was evaporated on
a rotary evaporator at a temperature below 50°C and dried
at room temperature in a vacuum desiccator to constant