Formation of furans upon electron-beam heating of cellulose

Article abstract of DOI:10.1134/S0018143911010085

Similarity between cotton cellulose and sulfate and sulfite pine celluloses in degradation during electron-beam distillation has been shown. The yield of the distillate liquid slightly depends on the type of cellulose and makes up ~60 wt %. The product liquid contains organic compounds with molecular masses of 32 to 128, of which furfural and its derivatives prevail. Electron-beam distillation can be used as an effective method for the manufacturing of furfural and other furan derivatives from cellulose (along with the traditional pentosan conversion processes). It has been shown that grinding and preheating of cellulose lead to an increase in the proportion of furfural and other furans in the condensates. Pleiades Publishing, Inc., 2011.

Full text of DOI:10.1134/S0018143911010085

ISSN 0018ꢀ1439, High Energy Chemistry, 2011, Vol. 45, No. 1, pp. 18–24. © Pleiades Publishing, Inc., 2011.
Original Russian Text © E.M. Kholodkova, A.V. Ponomarev, 2011, published in Khimiya Vysokikh Energii, 2011, Vol. 45, No. 1, pp. 21–27.
RADIATION CHEMISTRY
Formation of Furans upon ElectronꢀBeam Heating of Cellulose
E. M. Kholodkova and A. V. Ponomarev
Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
eꢀmail: ponomarev@ipc.rssi.ru
Received June 30, 2010
Abstract—Similarity between cotton cellulose and sulfate and sulfite pine celluloses in degradation during
electronꢀbeam distillation has been shown. The yield of the distillate liquid slightly depends on the type of
cellulose and makes up ~60 wt %. The product liquid contains organic compounds with molecular masses of
32 to 128, of which furfural and its derivatives prevail. Electronꢀbeam distillation can be used as an effective
method for the manufacturing of furfural and other furan derivatives from cellulose (along with the traditional
pentosan conversion processes). It has been shown that grinding and preheating of cellulose lead to an
increase in the proportion of furfural and other furans in the condensates.
DOI: 10.1134/S0018143911010085
INTRODUCTION
sweep width 245 mm, scanning frequency of 1 Hz).
Irradiation was carried out at atmospheric pressure
without air in 100ꢀml cylindrical quartz vessels. The
reaction vessels were filled to 60% of their volume at an
average packing density of 0.15 g/ml. The electron
beam was scanned along the vertical axis of the vessel.
The vapors were condensed in the air and waterꢀ
Destructive distillation initiated by radiation heatꢀ
ing with a fastꢀelectron beam (electron beam distillaꢀ
tion) is of interest as an efficient means of conversion
of lignocellulose raw materials into furans, phenols,
and acyclic carbonyl compounds demanded by a variꢀ
ety of chemical and fuel industries [1]. Concerning the
problem of deep processing of renewable raw materiꢀ
als, it is of primary importance to reveal of the basis
features of degradation of cellulose, which is the key
structural component of cell walls in all plants [2]. In
this work, we investigated the efficiency of electronꢀ
beam conversion of cellulose into liquid organic comꢀ
pounds, depending on temperature, degree of commiꢀ
nution, and the type of feedstock.
cooled condensers (at 16 2
°С
and 15 2 С, respecꢀ
°
tively) outside of the irradiation zone. To study the
temperature dependence, the O2 samples were preꢀ
liminary thermostated in a muffle furnace over 30 min.
To avoid the initiation of pyrogenetic dry distillation of
the samples, the preheating temperature was mainꢀ
tained not higher than 250
С.In this case, the preheatꢀ
°
ing step was immediately followed by electronꢀbeam
heating. Dosimetry was performed with the use of a
copolymer containing a phenazine dye SO PD(F)Rꢀ
5/50 (GSO (State Standard Sample) 7865ꢀ2000). The
EXPERIMENTAL
average dose rate
Р was 2.1 kGy/s. Distillation prodꢀ
Cotton cellulose (O1) according to GOST (State
Standard) 5556ꢀ81; pine unbleached sulfate pulp
(O2), GOST 12765ꢀ88; and pine bleached sulfite pulp
(O3) according to GOST 3914ꢀ89 were studied. Celluꢀ
ucts were determined chromatographically on a “Perꢀ
kin Elmer AutoSystem XL” instrument (the carrier gas
helium, glass capillary column of 60 m length and an
internal diameter of 0.25
µ
m, mass spectrometer and
lose samples were dried at 107
С and deaerated. To
°
thermal conductivity detectors).
study the dependence of electronꢀbeam distillation on
the degree of grinding of raw materials, O2 samples
with a specific surface area of 49–104 cm2/g (shredꢀ
ding by cutting sheets of EKBꢀ1 cardboard) were used.
The effect of the type and the initial temperature of
RESULTS AND DISCUSSION
According to telemetric observation data, the O1,
cellulose was studied using samples with a specific surꢀ O2, and O3 samples do not significantly differ in the
face area of 104 4 cm2/g. Distillation was initiated by dynamics of electronꢀbeam distillation. Heavy vapor
the radiation heating of samples with fast electrons begins to flow from the reaction vessel to the conꢀ
generated by a UELVꢀ10ꢀ10T linear accelerator denser and the receiving container at a dose of
(energy 8 MeV, pulse duration 6
µ
s, pulse repetition ~250 kGy. Its color varies from the original white to
frequency of 300 Hz, average beam current
≤800
µ
A, bright yellow. The formation of vapor and the rise of
18

FORMATION OF FURANS UPON ELECTRONꢀBEAM HEATING OF CELLULOSE
19
Yield G (wt %, on a dry cellulose basis) and properties of conꢀ
the condensate level in the receiver cease at a dose of
~500 kGy. The condensate is formed with a yield of
~60 wt % (see table). It is a homogeneous brown liquid
with high density, viscosity, and refractive index values,
a fact that is not typical of pyrolytic aqueous–organic
solutions [2]. The distillation residue is a dry black
powder (charcoal) with a volume smaller than that of
the original sample. The yield of the charcoal is about
20% of the mass of dry cellulose. The elemental compoꢀ
sition of the charcoal is characterized by a predominance
of carbon (89.1 mol %) and oxygen (10.6 mol %). Minꢀ
eral impurities are Ca (0.07 mol %), Cu (0.10 mol %),
and Zn (0.13 mol %) compounds.
18
18
densates (refractive index nD , density ρ , viscosity η0) and
average content of their major components
Sample
(S
= 104 g/cm3
)
O1
63
O2
58
O3
60
G, wt %
n1D8
1.4479 1.4449 1.4455
1.1639 1.1560 1.1594
The composition of the condensates is of the same
type (see table) and includes more than 40 organic
compounds with a molecular mass in the range of 32
to 128. The amount of water in the condensates varies
from 8 to 10 wt %. The main liquid products are
furans, such as 2ꢀfuraldehyde (furfural), 2ꢀfuranmetꢀ
anol, 5ꢀmethylꢀ2ꢀfuraldehyde, and 3ꢀfuraldehyde.
Some differences in yield and composition between
the condensates distilled from pine cellulose O2 and
O3, apparently stem from differences between the
processes of the chemical treatment of wood used for
the extraction of cellulose. A similar condensate comꢀ
position has been observed previously [3] in the study
of distillation of cotton cellulose and kraft pulp in a
stream of gaseous alkanes.
ρ
,
kg/dm3
η
,
mPa s
5.96
5.67
5.79
0
Amount of major components in condensate (wt %)
Methyl formate
Acetone
0.9
4.9
5.0
1.6
3.4
7.3
7.3
1.8
40.4
2.1
2.0
9.4
0.8
2.7
1.3
3.4
3.6
1.7
Formic acid
5.2
The shredding of O2 results leaves the condensate
yield almost unchanged, 58 2 wt %. There is a tenꢀ
dency toward a fall in the yield of the solid residue and
a rise in that of volatile fragmentation products (about
2–3 wt %). The condensate composition changes in
this case, the smaller the particle size of the raw mateꢀ
rial, the higher the density, viscosity, average molar mass,
refractive index, and optical absorption values of the conꢀ
densate (see Figs. 1, 2). As the degree of comminution
increases, the fraction of heavy furan derivatives,
which are the products of relatively slight fragmentaꢀ
tion of cellulose (such as furaldehydes, furanmethaꢀ
nols, and furanones) increases. At the same time the
proportion of products of deeper (secondary) fragꢀ
mentation of cellulose (such as 1ꢀhydroxyꢀ2ꢀproꢀ
panone and acetic and formic acids) is reduced, as well
as the relative amount of heavy products (such as
furanmethanol acetates) resulting from secondary
processes of interaction between the prevalent primary
products.
2,3ꢀButanedione
2ꢀOxopropanal
Acetic acid
3.5
0.6
0.8
3.1
6.0
1ꢀHydroxyꢀ2ꢀpropanone
1ꢀMethylpropyl acetate
2ꢀFuraldehyde
3ꢀFuraldehyde
Furanmethanols
Methylfuraldehydes
10.7
0.9
1.5
2.0
48.2
2.8
4.7
17.3
42.4
1.9
2.8
The products of radiolytic fragmentation of celluꢀ
lose are probably formed both on the surface and in the
bulk of solid particles. The migration of fragment molꢀ
ecules from the bulk of a solid particle to the surface
(in the moving vapor phase) takes time, thereby allowꢀ
ing for the secondary radiolytic and thermal degradaꢀ
tion of the primary fragmentation products or their
13.3
Total furans
62.5
64.4
79.0
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011

20
KHOLODKOVA, PONOMAREV
1.446
1.444
1.442
1.440
1.438
1.436
1.434
1.432
1.430
1.428
1.426
1.424
1.6
1.4
1
1.2
3
1.0
1.03
1.02
1.01
1.00
2
50
60
70
80
, cm /g
90
100
110
2
S
Fig. 1. Influence of the specific surface area of O2 samples on the (
1) viscosity
η
, (2
) the density , and (3) the refractive index
ρ
0
n1D6 of the condensate.
reaction with other products yielding the 'hybrid' comꢀ the initial temperature T0 increases, a rise in its density,
pounds. It is effects of this kind that seem to be responꢀ
sible for the influence of the degree of comminution
on the composition of the distillates condensed.
viscosity, and refractive index is observed. The molar
mass of the condensate smoothly increases from ~87
to ~94 g/mol. The absorbance at the band with λmax
=
275 nm characteristic of all furans increases (see
Fig. 2). The total amount of furan derivatives in the
condensate increases from 60 to 72 wt % with the
increasing initial temperature. In this case, furaldeꢀ
hydes remain the dominant furan species (of which
about 3/4 is made up by furfural). It is likely that preꢀ
heating promotes more rapid migration and distillaꢀ
tion of light fragmentation products on one hand and
the degradation of thermally unstable fragments at the
initial stages of radiolysis on the other hand. Being disꢀ
tilled off, the primary products are eliminated from the
subsequent stages of radiolysis and do not participate
in secondary reactions. The results of experiments
with preheating indicate the predominant role of radiꢀ
olytic processes in the formation of the final products.
The violent chain formation and vaporization of a
large mass of radiolytic products prevents the excess
heating of the cellulose feedstock, thereby precluding
the development of degradation and distillation via the
To preclude the pyrolytic decomposition of celluꢀ
lose before irradiation [2, 3], the dependence of elecꢀ
tronꢀbeam distillation on the severity of preheating
was investigated at a temperature T0 no higher than
250
time decreased somewhat, but the time of its compleꢀ
tion was not dependent on the initial temperature T0
°С. In the preheated samples, the distillation onset
.
This implies that the radiolysis and radiation heating
determine the dynamics of electronꢀbeam distillation
to a greater extent than does the feedstock temperaꢀ
ture. The yield of condensate was 58.0 1.5 wt % in
the examined temperature range of
Most liquid products of radiolytic degradation have a
boiling point in the range of 100–250 . Their heat of
T
0 = 16–250 С.
°
°С
vaporization is 30–46 kJ/mol [4, 5]. The consumption
of energy for evaporation is several times greater than
the amount of heat received by cellulose during preꢀ
heating (about 3.1 kJ/mol per glucopyranose cycle).
At the same time, preheating facilitates the formaꢀ
tion of a heavier condensate (see Figs. 2, 3); namely, as unfavorable “pyrogenetic” mechanism.
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011

FORMATION OF FURANS UPON ELECTRONꢀBEAM HEATING OF CELLULOSE
21
The main gaseous degradation products are СО2, Н2
,
and some of its derivatives. It was shown [6] that furꢀ
and CO. Carbon dioxide and hydrogen are formed in fural rapidly degrades in an acidic medium, yielding
about equimolar amounts, whereas the yield of CO is an formic acid and humic substances (100 g of furfural
order of magnitude lower. The stoichiometrically deterꢀ gives 50 g of formic acid and 41.5 g of humic subꢀ
stances). The formation of macromolecular products
due to furfural interaction with intermediate comꢀ
pounds can play a significant role as well [6].
mined mass fraction of the –O–C–O– fragments (probꢀ
able precursors of СО2) in the С6Н10О5 cycle is about
27 wt %. However, the experimental total yield of СО2
and CO is approximately 1/5 of the dry cellulose mass.
The formation of charcoal and the low gas yield suggest
the existence of competitive cellulose degradation proꢀ
cesses. In particular, the decrease in the yield of gases can
be due to the processes of formation of carboxyl and carꢀ
bonyl compounds, which do not involve the elimination
of СО2 or CO. A part of the charcoal may result from
chemical condensation of degradation products when
highꢀboilingꢀpoint compounds, which are difficult to
distill from the reaction zone, are formed. As shown in
Fig. 4, the dry residue of samples O1–O3 was composed
of two factions, the soft fibrous matter (resembling the
In practice, furfural is produced by acid hydrolysis
of pentosans, which are components of the composiꢀ
tion of easily hydrolysable plant hemicelluloses [2, 6]
С5Н10О5 – 3Н2О
→
С5Н4О2.
(2)
Both the hydrolysis and pyrolysis of cellulose, in conꢀ
trast to hemicellulose, is characterized by a low furꢀ
fural formation probability, ~10 wt % [1, 2, 6]. In this
study, we used hemicelluloseꢀdepleted samples. Conꢀ
sequently, the high yield of furfural is due to the degraꢀ
dation of the cellulose itself.
original cellulose in structure; C/O atomic ratio
see Fig. 4a) and solid inclusions (in the form of beads and
plates, the C/O atomic ratio 6.4, see Fig. 4b) with a
≈
8.4,
The primary radicals of cellulose (generated
mainly via the abstraction of H atom in the 1ꢀ or
4ꢀposition of the glucopyranose cycle [7]) are unstable
and, as a result of significant strain caused by the misꢀ
match of electron configurations of the radical center
produced (sp2 hybridization) and the initial fragment
≈
porous structure. The second fraction occurs on the charꢀ
coal surface and seems to be produced via condensation
and secondary transformations of heavy vaporous prodꢀ
ucts. In particular, condensation processes under dry disꢀ
tillation conditions are characteristic of furfural
(
sp3 hybridization) decompose even at room temperaꢀ
2С5Н4О2
→
С10Н6О3 +Н2О
(1)
ture with a cleavage of the glycosidic bond [7, 8]:
CH2OH
CH2OH
CH2OH
CH2OH
O
OH
O
OH
O
OH
O
•
•
(3)
OH
+
•
O
O
O
•
O
OH
O
,
OH
OH
OH
OH
CH2OH
CH2OH
O
CH2OH
O
CH2OH
O
O
OH
•
(4)
(5)
OH
OH
+
• OH
O
O
O
O
•
•
HO
O
.
OH
OH
OH
OH
Apparently, the intermediate products of reactions
(3) and (4) are thermally unstable and decompose via
a chain mechanism, releasing prevalently СО2, Н2О
and an organic fragment R (average formula С5Н6О2).
The stage of decomposition of glucopyranose cycles
can be written in the form of balance equation:
С6Н10О5
→
СО2 + Н2О + Н2 + С5Н6О2.
In particular, the formation of furfuryl alcohol
and furfural can be due to the thermally stimulated
ꢀcleavage of skeletal bonds typical of radicals
,
β
[9, 10]:
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011

22
KHOLODKOVA, PONOMAREV
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
4
3
2
1
200
250
300
, nm
350
400
λ
Fig. 2. Electronic absorption spectra of the condensates distilled off O2 at initial temperatures of 16°C (S = (1) 49, (2) 70, and (3)
2
2
104 cm /g) and 230°С ((4) S = 104 cm /g).
CH OH
CH OH
•
CH OH
2
2
2
CHO
CH OH
2
•
•O
O
OH •
•
O
–
H
–
H O
2
,
–2H
–CO
2
2
O
O
(6)
H
OH
OH
O
HO
CH OH
CH OH
CH OH
2
2
2
CH OH
CHO
2
•
O
O
•
O
–H
–H O
2
–CO , –H
2
2
.
O
•
•
O
(7)
H
OH
OH
O
O
HO
The organic fragment R released from the glucopyꢀ dehydrogenation of the radical, the excess energy and
ranose cycle in reactions of type (6) and (7) can have temperature, the presence and structure of the hydroꢀ
several configurations determined by a number of facꢀ gen bond system, steric factors controlling the detachꢀ
tors: the site of the primary C–H bond rupture, the ment of the fragmentation products from their formaꢀ
place of localization of the unpaired electron during tion place, and some others. The possibility of existꢀ
the transformation of the organic radical, the position ence of a few forms for the released fragment
of the double bond formed as a result of dehydration or determines the likelihood of different ways of its stabiꢀ
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011

FORMATION OF FURANS UPON ELECTRONꢀBEAM HEATING OF CELLULOSE
23
1.18
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.00
0.98
1.446
1.444
1.442
1.440
1.438
1.436
1.434
3
1
1.08
1.07
1.06
1.05
1.04
1.03
1.02
1.01
1.00
0.99
2
0
50
100
150
200
250
t
, °C
2
Fig. 3. Influence of the initial temperature of O2 samples (
S
= 104 cm /g) on (
1
) the viscosity
η , (
0
2
) the density , and (3) the
ρ
refractive index n1D6 of the condensate.
lization or transformation into final lowꢀmolecularꢀ Obviously, the close packing of molecules in cellulose
mass products. The chain mode of cellulose degradaꢀ fibrils [2, 7] can impede the removal of the fragmentaꢀ
tion is apparently due to both the release of H atoms tion products. This increases the probability of conꢀ
and the thermal instability of shorter radicals resulting version of allyl radicals into more stable polyene radiꢀ
from the decay of the primary radical intermediates. cals [11]
CH2OH
CH2OH
HC
HC
2
CH
HC
CH
C
O
CH
2
O
C
H
2
H
C
H
C
H
•
C
•
•
C
–H O
2
–CO , –H O
2 2
C
(8)
O
CH
HC
O
C
H
C
OH
C
C
CH HC
C
HC
C
.
C
H
OH
OH
H
OH
OH
HO
OH
which precede the formation of the coalꢀlike residue.
A part of the organic fragments, such as furfural,
being effective of radical scavengers and acceptors of
excess energy [6, 10], are involved in rapid reactions
with other products of the fragmentation or decay,
thereby extending the range of end products.
In summary, the electronꢀbeam distillation of celꢀ
lulose of different origin gives about 60 wt % of liquid
condensate. The liquid products are dominated by furꢀ
fural and its derivatives. Their proportion in the conꢀ
densate distilled off is facilitated by shredding and preꢀ
heating of the feedstock. The electronꢀbeam dry distilꢀ
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011

24
KHOLODKOVA, PONOMAREV
ventional methods based on the extraction and conꢀ
version of hemicelluloses, this process can make use of
the most widespread celluloseꢀrich plant materials
(including waste) as feedstock.
ACKNOWLEDGMENTS
The work was supported by the Russian Foundation
for Basic Research, project no. 09ꢀ03ꢀ12081ꢀofi_m.
REFERENCES
1. Ponomarev, A.V. and Tsivadze, A.Yu., Dokl. Akad.
Nauk, 2009, vol. 424, no. 1, p. 57.
2. Fengel, D. and Wegener, G., Wood: Chemistry, Ultraꢀ
structure, Reactions, Berlin: Walter de Gruyter, 1984.
(а)
30 µm
3. Ponomarev, A.V., Bludenko, A.V., Chulkov, V.N.,
Tananaev, I.G., Myasoedov, B.F., and Tsivadze, A.Yu.,
Khim. Vys. Energ., 2009, vol. 43, no. 5, p. 404 [High
Energy Chem., 2009, vol. 43, no. 5, p. 350].
4. Svoistva organicheskikh soedinenii. Spravochnik (Properties
of Organic Compounds: A Handbook) Potekhin, A.A.,
Ed., Leningrad: Khimiya, 1984.
5. Kratkii spravochnik fizikoꢀkhimicheskikh velichin (Conꢀ
cise Handbook of Physicochemical Quantities),
Ravdel’, A.A. and Ponomareva, A.M., Eds., Leningrad:
Khimiya, 1983.
6. Shcherbakov, A.A., Furfurol (Furaldehyde), Kiev: Gos.
Izd. Tekhn. Liter., 1962.
7. Ershov, B.G., Usp. Khim., 1998, vol. 67, no. 4, p. 353.
(b)
30 µm
8. Ershov, B.G. and Klimentov, A.S., Usp. Khim., 1984,
vol. 53, p. 2056.
9. Pryor, W.A., Free Radicals, New York: McGrawꢀHill,
Fig. 4. Structure of the (a) bulk and (b) surface charcoal
fractions (105 80 m).
×
µ
1966.
10. Woods, R.J. and Pikaev, A.K., Applied Radiation Chemꢀ
istry: Radiation Processing, New York: Wiley, 1994.
11. Kuzina, S.I. and Mikhailov, A.I., Zh. Fiz. Khim., 2006,
lation mode holds promise as a method for obtaining
furfural and other furan derivatives. Unlike the conꢀ
vol. 80, no. 10, p. 1874.
HIGH ENERGY CHEMISTRY
Vol. 45
No. 1
2011