Polymer Journal, Vol7: No. 4, pp 431-437 (1975)

Curie-Point Pyrolysis of Cellulose*
Akio OHNISHI, Kunio KATO, and Eriko TAKAGICentral Research Institute, The Japan Tobacco & Salt Public Corporation
6-2, Umegaoka, Midori-ku, Yokohama 227, Japan.
(Received October 4, 1974)
Abstract: Microcrystalline cellulose was pyrolysed using a Curie-point pyrolyser,
directly attached to a GLC apparatus, at 460'C for 5 sec under a neat condition without any additives. Although the total yield of organic volatile fraction was not sohigh, 2-furaldehyde and levoglucosenone were observed as the major components in thisfraction. Another volatile product, 1,6-anhydr0-3-deoxy-p-D-glucopyranosen, was also
identified as the intermediate between levoglucosan and levoglucosenone. Levoglucosan
could not be directly detected by the pyrolysis-GLC technique because of its low volatility, but it was thought to be one of the major components of the tar produced.
Only slight amounts of these anhydro sugar homologues were observed in the Curiepoint pyrolysis with D-glucose, cellobiose, cellotriose, cellotetraose, cellopentaose, andcellohexaose, though furans were abundantly observed in the volatile fractions. These
results suggest the following two paths for the thermal decomposition reaction ofcellulose at the initial stage:
Cellulose - Levoglucosan, 1,6-anhydro-3deoxy-β-D-glucopyranosen, andlevoglucosenone
Cellulose - 5-Hydroxymethyl-2-furaldehyde, 2-furaldehyde, and otherfuran compounds
KEY WORDS Cellulose / Cello-Oligosaccharide / Pyrolysis / Thermal
Decomposition / Curie-Point Pyrolyser / Levoglucosan / I ,6-Anhydro3-Deoxy-p-D-Glucopyranosen / Levoglucosenone / 2-Furaldehyde / 5Hydroxymethyl-2-Furaldehyde /Thermal decomposition of cellulose has been
widely investigated by many workers.1 among
the chemical approaches used to elucidate themechanisms of the thermal decomposition reaction of cellulose, the isolation and the analysis
of certain intermediate products may give themost valuable clues.
As early as in 1918, levoglucosan (1 ,6-anhydroβ-D-glucopyranose) (1) was reported as an important product in the pyrolysis of cellulose byPictet and Sarasin.2 This compound has also
been recognised in the pyrolysis of starch2 andD-glucose,3,4 and has been believed for a longtime to be a major intermediate product of thethermal decomposition of these carbohydrates.
Recently, Tsuchiya and Sumi5 isolated a liquidcompound, C6H6O3, as a main component of thevolatile fraction in the acid-catalysed pyrolysis
PPPPPP

B

B

B

B

B

B

PPof cellulose, and Halpern, et al.,6 identified thiscompound as levoglucosenone (1,6-anhydro-3,4dideoxy-β-D-glucopyranosen-2-one) (Ⅲ). It thus
becomes very interesting to discuss the thermal
decomposition mechanism of cellulose, althoughthese experiments were not carried out in a neatcondition, because Ⅲ can be formed by theelimination of two molecules of water from I.
On the other hand, Kato and Komorita7 suggested 3-deoxyglycosulose (IV), as one of thesignificant decomposition intermediates which
would lead to the formation of furan compounds,
such as 5-hydroxymethyl-2-furaldehyde, furfuryl
alcohol, and 2-furaldehyde.
However, most of these suggestions were basedon the results obtained through a relatively longtime exposure of the decomposition products ina hot furnace, which would bring about successive reactions of the primary products: such as
dehydration, decarboxylation, depolymerization,condensation, and fragmentation. Accordingly,PPPP

the GLC patterns finally observed would beconsiderably different from those of the primary
product only.
To obtain the real primary decomposition
products of cellulose and related compounds,
the authors have applied a Curie-point pyrolysisGLC (CPP-GLC) which was developed bySimon, et al.,8 in 1967. In this procedure, samples are momentarily heated to a fixed temperature and kept at the temperature for a few
seconds in an inert carrier gas atmosphere which
is maintained at a relatively low temperature,so successive reactions of the primary products
due to excess heating are almost totally avoided.
In this paper, 111, II, 2-furaldehyde, and 5hydroxymethyl-2-furaldehyde have been identified
in the volatile fraction of the primary decomposition products in the Curie-point pyrolysis ofcellulose, and the mechanism of the thermal
decomposition reaction is discussed. Also theconventional methods for the preparation of IIand Ⅲ are described.
PPEXPERIMENTAL
SamplesCommercial microcrystalline cellulose powder(Avicel, for column chromatography, Asahi
Chemical Industry Co., Ltd., Tokyo) was usedas the standard cellulose sample after being
treated with 1-N HCl at 85℃ for 30 min, washedwith water repeatedly, and dried over phosphorus pentoxide.
Levoglucosan (Ⅰ) was prepared and purified by
the usual method.9
Cello-oligosaccharides (cellobiose, cellotriose,cellotetraose, cellopentaose, and cellohexaose)
were prepared as follows: The cellulose sample
was acetolysed10 at 40℃ for 24 hr. The resultant
acetolysate was saponified with 0.2-N NaOCH3
in methanol, and the white precipitate was collected, dissolved in water, and deionised withDowex 50W. A portion ofthe aqueous solution
was charged on a Sephadex G 25 (fine) column(15x 1450mm) and the column was eluted withwater. The fractions containing the individualoligosaccharide were combined, and each wasevaporated to dryness. The individual residues
were crystallised from methanol or watermethanol, respectively.
PPPPBB

Instrumentation
The CPP-GLC was carried out by a Shimadzu
model PYR-10 Curie-point pyrolyser directly
combined with a Hitachi model 063 gas chromatograph, equipped with a fiame ionisation detector
using a 5-% Carbowax 20M on Chromosorb G
AW (60/80 mesh) column (stainless steel, 3 mmx
3 m). A typical CPP-GLC was carried out
under the following conditions:
Sample weight, 0.2-0.4 mg; pyrolysis temperature, 460℃; heating period (oscillation period),
5 sec; atmosphere, He (containing 02 less than2 ppm); flow rate, 40 ml/min; column oven temperature, 80-230℃ (7.5℃/min).
A Shimadzu model PYR-2A furnace-type
pyrolyser was also used as a reference for theCurie-point pyrolyser; in this procedure a 0.2mg sample fixed on a sample holder was quickly
inserted into the furnace kept at a fixed temperature, and as soon as the temperature of thesample reached 460'C the holder was taken out
from the furnace.
For the preparative-GLC operation, a Hitachi
model K 23 gas chromatograph equipped witha thermal conductivity detector was used underisothermal conditions; a 10-% Carbowax 20 M
on Chromosorb W AW (60/80mesh) column(stainless steel, 3 mmx2m) was used.
The NMR, mass, IR, and UV spectra were
measured using a JEOL model JNM-PS-100, aHitachi model RMU-7, a JASCO model IR-G,
and a Hitachi model 124, respectively. .' The
optical rotations were measured on a Yanaco
model OR-50D, and the elementary analyses
were carried out on a Yanaco model MT-2.
Preparation of 1,6-Anhydro-3-Deoxy-β-D-Glucopyranosen (Ⅱ)
The cellulose sample was pyrolysed in a Pyrex
glass tube at 300-300'C for about I hr under
reduced pressure (1 mmHg). The resultant dark
reddish syruppy distillate was extracted with
ethyl acetate repeatedly.. The extract was concentrated and fractionated with a silicic acidcolumn (15xl50mm) using ethyl acetate as
eluant. The fraction corresponding to this compound was collected and treated with activatedcharcoal. After filtration the clear filtrate wasconcentrated to an yellowish crude material,
which was purified by recrystallization from ethyl

acetate. The pure compound was obtained aswater-soluble fine white crystals: mp 130-131℃,

〔α〕20D=+86℃(C2H5OH, c=0.6).
Preoaration of Levoglucosenone (III)The cellulose sample was treated with a l-%(v/v) solution of 85-% H3PO4, as described by
Tsuchiya and Sumi,5 and pyrolysed by the above
method. The resultant liquid pyrolysate wasdistilled with a microdistillation apparatus under
reduced pressure and the fraction of bp 110120℃ (20 mm) was collected. The greenyellowish liquor obtained was almost pure levoglucosenone. For further purification, a preparative. GLC was conducted using a 10-% Carbowax
20 M column. The pure compound was obtained
as water-insoluble green-yellowish liquor: [α] 20D =-524°(C2H5OH, c=1.0) [lit.6 –460°(CHCl3,c= 1.0)].
P

PB

B

B

B

B

B

B

P

B

B

B

P

P

B

B

B

B

B

PB

B

RESULTS AND DISCUSSIONSCPP_GLC with Cellulose
Some typical results of CPP-GLC and furnacetype pyrolysis-GLC (FTP-GLC) with cellulose
are shown in Figures I and 2, respectively. It
i$ obvious that the chromatogram obtained fromtbe use of a Curie-point pyrolyser (Figure 1) iseJttremely simple relative to that of the furnacet)'pc pyrolyser (Figure 2). The peaks whichappear within 5 min of the retention time correspond to the light gases derived from theprimary decomposition products by their furtherfragmentations. As seen from the figures, boththe members and contents of the light gases in
the CPP-GLC are much less : than those in theFTP-GLC. Moreover, it is very interesting to
notice that in the case of CPP-GLC, only twocomponents, peaks A and B, are particularlyBdominant in the volatile fraction. These twocomponents seem to be the primary products ofthe thermal decomposition of cellulose detectableby the GLC technique. In the case of FTPGLC, many components other than peaks A andB are observed: these seem to be derived fromsuccessive heat reactions of the primary decomposition products.
This indicates that in the Curie-point pyrolysis
of cellulose, the primary decomposition products,
such as the components corresponding to peaks
A and B, were detectable without any further
successive reactions.
ldentifications of Peak Compounds
The compounds corresponding to peaks A, C,
and E in Figure I were identified as 2-furaldehyde, Ievulinic acid, and 5-hydroxymethyl-2furaldehyde, respectively, from their retention
times and mass spectrum data.
The peak B compound was identified as levoglucosenone (III) after patient preparation using
a preparative CPP-GLC instrument equippedwith a thermal conductivity detector.

The compound Ⅲ had a smoky odor and madea purple chelate complex with ferric chloride
through keto-enol tautomerization. The melting
point of the 2,4-dinitrophenylhydrazone (reddish
needles from CHCl3) was 214℃ (decomp).
The peak D compound was identified as 1,6anhydro-3-deoxy-β-D-glucopyranosen (II) after thepurification mentioned above.
B

These data precisely agreed with those of thecompound prepared from the method mentioned
in the experimental section, and seem to be
essentially the same as those presented byHalpern, et al.6
It should be noted that 111 was the dominant
yield, together with 2-furaldehyde, in the caseof CPP-GLC under the neat condition without
any additives, as in the acid-catalysed pyrolysis
of cellulose.5,6
PPPPB

thermal decomposition of cellulose were furans (2furaldehyde and 5-hydroxymethyl-2-furaldehyde)
and volatile anhydro sugar homologues (Ⅱ andIII). The result of CPP-GLC with D-glucose
is shown in Figure 7. As seen in the figure,the primary decomposition products of D-glucose
were mostly furans, and volatile anhydro sugar
homologues were rarely observed. The next

prepared from the method in the experimental
section. These assignments satisfied formula
II and all other configurations were found to
be unconstructable by the use of molecularmodels.
The CPP-GLC of 11 showed the formationof Ⅲ, and on the other hand Ⅱ was formed
from Ⅲ by storage for several month in air.
Accordingly, the compound 11 seems to be theintermediate between I and Ⅲ.
The compound 111 has never been directlyobserved as the pyrolysis product of cellulose
using other pyrolysis-GLC techniques than theCPP-GLC one. The reason for this may bethat in the case of CPP-GLC the successive
decomposition reactions of Ⅲ which must occur
very rapidly in the other cases were almost
avoided by momentarily heating in the relatively
low temperature inert atmosphere. Therefore
the Curie-point pyrolysis system seems to bevery superior to the other usual ones for studying the mechanisms of thermal de. composition
reactions.
CPP-GLC with D-Glucose and Cello-Oligosaccharides
As shown in Figure 1 , the primary products ofproblem presented was how many β-1 ,4-glucosidebonds in a molecule are, at the least, required
for the formation of Ⅱ or Ⅲ as the primarypyrolysis products. To investigate this problem,
cellobiose, cellotriose, cellotetraose, cellopentaose,and cellohexaose were prepared and their pyrolitic
behaviors were examined.
The results of CPP-GLC with these cellooligosaccharides are shown in Figure 8, in whichthe products were mostly furans, and Ⅱ and Ⅲ
were rarely observed as in the case of D-glucose(Figure 7). Thus a higher degree of polymerization, above seven or more, and probably somewhat higher order conformations will be requiredfor presenting the same decomposition profiles
as in the case of cellulose.
Decomposition Mechanism
As shown in Figure 1 , the primary productsof thermal decomposition of cellulose were bothfurans and anhydro sugar homologues, whereas
those of D-glucose and cello-oligosaccharides
were almost exclusively furans, as shown inFigures 7 and 8. Although it has been rePorted3,4 that I is produced from pyrolysis ofD-glucose in a heated vessel or a glass tube, inmost of those experiments D-glucose might firstbe polycondensated and certain polysaccharides
thus formed subsequently decompose into theseanhydro sugar homologues.
The result of CPP-GLC with I is shown inFigure 9. The main products were Ⅲ and II,
and no furans were observed. This indicatesthat I does not play an important role as aniutermediate for the formation of furans during
the thermal decomposition of cellulose. It isalso assumed that whenever I is formed duringPP

the decomposition reaction, its homologous compounds Ⅱ and Ⅲ would be also produced. Accordingly, when Ⅱ or Ⅲ is observed in thevolatile fraction of pyrolysates of cellulose, I
should be also produced simultaneously although
I can not be detected directly by the CPP-GLC
method because of its lower volatility.
The pyrolysis yields of Ⅲ and 2-furaldehyde
were measured as approximately 3 and 2 wt%
respectively, under the conditions of this CPPGLC technique. The yield of tar condensed onthe inside wali of the instrument was approximately 55-75 wt% in which the major components were thought to be I and such a precursorof 2-furaldehyde as IV. Those of water andthe residual char were approximately 5-15 and15-35 wt% respectively.
Thus the total yield of organic volatile fraction
was not so great, but volatile compounds otherthan Ⅲ and 2-fualdehyde were hardly observedat all as seen in Figure I .
From the above observations the following
reaction scheme was suggested for the formationof anhydro sugar homologues as the primarydecomposition products of cellulose.

The compounds I, II, and Ⅲ may be produced
not only through the straight paths (1), (2), or(3), but also through the formation of a certain
anhydro. and/or deoxy-saccharide moiety in apolymer chain such as the paths (4), (5), or (6).
However, no direct evidence for the latter reaction process has been obtained yet.
On the other hand, the following mechanism
has been suggested for the formation of furancompounds from cellulose.７PP

The intermediate compound 3-deoxyglycosulose(IV) was identified by Kato and Komorita.7
The result of CPP-GLC with I (Figure 9), in
which furans were only slightly observed, supports strongly the above reaction scheme.
Acknowledgment. The authors wish to thankProf. Hiroshi Sugisawa of The Kagawa University
for his valuable comments in measuring themass spectroscopy of carbohydrates. They also
thank Dr. Masao Noguchi of this institute forreading this manuscript and giving much kindadvice .