Rapid screening of catalytic pyrolysis reactions of Organosolv lignins with the vTI-mini fast pyrolyzer, Sci ...
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Rapid Screening of Catalytic Pyrolysis Reactions of
Organosolv Lignins with the vTI-Mini Fast Pyrolyzer
Hang Seok Choi,
a
Dietrich Meier,
b
and Michael Windt
b
a
Department of Environmental Engineering, Yonsei University, 1 Yonseidae-gil, Wonju,
Gangwon-do, 220-710, South Korea; hs.choi@yonsei.ac.kr (for correspondence)
b
vTI-Institute of Wood Technology and Wood Biology, Leuschnerstrasse 91, D-21031, Hamburg, Germany
Published online 27 March 2012 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.11625
On the other hand, the use of catalysts in biomass pyrolysis
is currently in the focus of interest [3–5]. For the pyrolysis of
lignin, experimental studies have been carried out with and
without catalyst [6–13]. Jackson et al. [7] carried out the
thermo-chemical conversion of pure lignin (ASIAN lignin) with
five different catalysts. Using analytical pyrolysis-GC/MS, they
showed that HZSM-5 catalyst was the best one for producing
deoxygenated liquid fraction and Co/Mo/Al
2
O
3
produced a
hydrogen-rich gas phase. Further studies [9] were carried out
for the catalytic pyrolysis-GC/MS of various lignins with
HZSM-5 and Co/Mo/Al
2
O
3
catalyst. They found out similar pat-
terns with Jackson’s results however, they showed that the
H:G:S ratio of the lignin starting material and catalyst could
change the ratios of individual aromatic compounds. In partic-
ular, Meier et al. [13] carried out catalytic hydropyrolysis of
three different lignins and showed that the main components
of monomeric compounds were phenol and cresols. Most of
the studies have been used analytical pyrolysis techniques or
bench-scale pyrolyzers. Analytical pyrolysis could not give
enough comprehensive information on product yields includ-
ing liquid and solid phases because (1) the solid residue can-
not be recollected after the experiment and (2) the quantitation
of volatiles is extremely difficult due to the lack of internal
standard addition. Furthermore, it is very difficult for bench-
scale pyrolyzers to have rapid and homogeneous temperature
distribution over the entire lignin sample during the pyrolysis
process, which is essential for ideal fast pyrolysis condition.
Therefore, the scope of this work was to apply the vTI-mini
fast pyrolyzer [6] for the pyrolysis experiments of Organosolv
lignins to overcome the disadvantages of other laboratory scale
pyrolysis techniques. In addition, the system allows for rapid
screening due to its modular system and ease of operation.
The vTI-mini fast pyrolyzer was applied for screening fast
pyrolysis reactions of different Organosolv lignins, such as
Alcell (Repap Technologies) and lignin from a German
biorefinery project. To investigate the catalytic effects on the
pyrolysis of the technical lignins, three catalysts such as
zeolite HZSM-5, FCC, and Olivine were used. The catalytic
pyrolysis characteristics and decomposition products of the
Organosolv lignins were scrutinized by varying pyrolysis tem-
perature and catalyst type. From the pyrolysis experiments,
obtained pyrolyzed products were generally categorized into
three parts such as coke, noncondensable gas, and biocrude
oil. To evaluate the yield of biocrude oil, mass balances of
products and reactants were established and the collected
biocrude oil was analyzed by GC/MS. From the results, the
increase or decrease patterns of certain chemical compounds
were found according to the different pyrolysis temperatures
as well as various catalysts. In particular, size exclusion
chromatography (SEC) was performed for extracts of the solid
residue to get information on the catalytic effect and severity
of lignin degradation.
2012 American Institute of Chemical
Engineers Environ Prog, 31: 240–244, 2012
Keywords: biocrude oil, catalyst, pyrolysis, organosolv lignin
INTRODUCTION
To overcome environmental problems such as CO
2
dis-
charge caused by combustion of fossil fuels as well as natural
resource depletion, biomass is highlighted as one of the
promising renewable energy resources. There are many
kinds of biomass which can be applied to renewable energy:
wood, shrub, municipal waste, sewage, etc. In particular,
lignin is one of the most abundant biomass components and
could be utilized for renewable energy or renewable aro-
matic resource. Recently, the use of lignin is becoming
increasingly interesting due to biorefinery concepts which
are being developed in many countries [1]. In many cases,
lignin is obtained as by-product of pulping processes (Kraft,
Organosolv) and hydrolysis/fermentation processes. The
degradation of the aromatic polymer by pyrolysis has been
studied over decades and an overview of the literature is
beyond the scope of this work. Recently, fast pyrolysis of
various lignins was published in the framework of IEA round
robin testing [2]. Different reactor systems were used
but the overall yields and composition of the pyrolyzate
showed no significant differences compared to other litera-
ture data.
MATERIALS AND METHODS
Before pyrolysis all lignin samples were dried in an evac-
uated desiccator over phosphoric anhydride at 40
8
C. Figure 1
shows the schematic diagram of the vTI-mini fast pyrolyzer
system. It mainly consists of a quartz pyrolysis tube, moving
heater, and rapid quenching tube for complete condensation
of volatiles. Totally, 40 mg of lignin was placed in the middle
of the reactor tube. The moving oven was preheated to 500
or 600
8
C and automatically moved over the lignin sample to
ensure rapid uniform heating. Three thermocouples moni-
tored the temperature over the whole lignin sample at a very
short sampling frequency of 0.02 s. The temperature of the
lignin sample was reached to the pyrolysis temperature dur-
ing heat-up time of 40 s. Then, the pyrolysis temperature
was held constant for 80 s. In the vTI-mini fast pyrolysis sys-
2012 American Institute of Chemical Engineers
240
July 2012
Environmental Progress & Sustainable Energy (Vol.31, No.2) DOI 10.1002/ep
Figure 1. The schematic diagram of the vTI-mini fast pyrolyzer system.
tem, a catalyst bed, containing 40 mg, is located after the lig-
nin sample and placed between the quartz wool. Initially,
the fast pyrolysis of Organosolv lignin occurs and then the
pyrolyzed volatiles and non-condensable gases are entrained
into the catalyst layer by nitrogen flow of 50 mL/min. The
resulting volatiles are condensed in the rapid quenching
tube. After the experiment, the system was dismantled and
all parts weighed for overall mass balance. The rapid
quenching tube and micro filter were washed out using
acetone containing a known concentration of fluoranthene as
internal standard so that the liquid phase (biocrude oil) could
be directly injected and analyzed by GC/MS/FID. In a typical
case, this type of experiment could be carried out four
to five times per day considering general working time
(8 h/day). The GC separation was on a Varian (f4 1701)
fused-silica column with the dimensions of 60 m
Table 1. Experimental conditions.
Lignin
type
Catalyst
type
Pyrolysis
temperature (
Run No.
8
C)
1
Alcell
—
470
2
Alcell
HZSM-5
470
3
Alcell
FCC
470
4
Alcell
Olivine
470
5
Alcell
—
560
6
Alcell
HZSM-5
560
7
Alcell
FCC
560
8
Alcell
Olivine
560
9
Organosolv
—
470
10
Organosolv
HZSM-5
470
3
0.25 mm
11
Organosolv
FCC
470
and 0.25
m film thickness. Oven temperature was held at
45
8
C for 4 min and heated up to 280
8
C(4
8
C/min) and held
at 280
8
C for 20 min with Helium carrier gas (2 mL/min). Elec-
tron impact mass spectra were obtained by HP 5972MS at
70 eV ionization energy. For size exclusion chromatography
(SEC), the solid residue which remained in the quartz pyroly-
sis tube was extracted and dissolved by DMSO (dimethyl
sulfoxide). GPC method was adopted from Ringena et al.
[14], except the column set which had an exclusion limit of
30.000 Da. For reference, the experimental conditions
applied in the present study are described in Table 1.
l
12
Organosolv
Olivine
470
13
Organosolv
—
560
14
Organosolv
HZSM-5
560
15
Organosolv
FCC
560
16
Organosolv
Olivine
560
coke, noncondensable gas and biocrude oil. Figure 2 shows
the weight base percentage of product yields from dry lignin.
The noncondensable gas yield is indirectly calculated as the
lignin weight minus the sum of biocrude oil and coke
weights. For Alcell lignin at pyrolysis temperature 470
8
C
(run1-run4), the yield of biocrude oil is increased from 49.6%
(run1) to 56.4% (run2) and 56.3% (run4) when the catalysts
are used except
RESULTS AND DISCUSSION
The obtained products from the pyrolysis of Organosolv
lignins are generally categorized into three parts such as
for
run3 (45.6%). The coke yield is
Figure 2. The yields of liquid, solid and gaseous products (wt % based on dry lignin). [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
Environmental Progress & Sustainable Energy (Vol.31, No.2) DOI 10.1002/ep
July 2012
241
Table 2. GC detectable components in biocrude oil (wt.% based on dry lignin).
(wt %, dry basis)
Components
Run1
Run3
Run7
Acids
1.76
1.85
1.73
Acetic acid
1.76
1.85
1.73
Nonaromatic Ketones
0.07
0.08
0.08
Acetol (Hydroxypropanone)
0.07
0.08
0.08
Furans
0.75
0.28
0.44
Furaldehyde, 22
0.75
0.28
0.44
Sugars
1.00
1.11
1.18
Anhydro-b-
D
-glucopyranose, 1,6-(Levoglucosan)
1.00
1.11
1.18
Benzenes
0.06
0.15
0.14
Indene, 6-hydroxy-5,7-dimethoxy-1H-
0.06
0.15
0.14
Catechols
1.60
1.04
1.88
Catechol, 3-methoxy
1.60
1.04
1.88
Lignin-derived phenols
0.64
0.59
1.52
Phenol
0.13
0.15
0.32
Cresol, o-
0.05
0.09
0.18
Cresol, p-
0.07
0.09
0.15
Cresol, m-
0.02
0.07
0.13
Phenol, 2,5-dimethyl-
0.02
0.03
0.05
Phenol, 2,4-dimethyl-
0.03
0.04
0.08
Phenol, 4-ethyl-
0.02
0.02
0.02
Phenol, 2,4- or 2,5-dimethoxy
0.30
0.11
0.59
Guaiacols (methoxy phenols)
5.66
5.88
7.98
Guaiacol
1.42
1.72
2.13
Guaiacol, 3-methyl
0.11
0.13
0.20
Guaiacol, 4-methyl
1.62
1.63
2.26
Guaiacol, 3-ethyl
0.10
0.12
0.17
Guaiacol, 4-ethyl
0.45
0.58
0.76
Guaiacol, 4-allyl- ; (Eugenol)
0.12
0.11
0.17
Guaiacol, 4-propyl-
0.13
0.15
0.23
Guaiacol, 4-propenyl-; (Isoeugenol) cis
0.13
0.16
0.22
Guaiacol, 4-propenyl-; (Isoeugenol) trans
0.55
0.43
0.65
Vanillin
0.45
0.37
0.53
Dihydroconiferyl alcohol
0.08
0.06
0.00
Phenylethanone, 4-hydroxy-3-methoxy; (Acetoguaiacone)
0.32
0.27
0.45
Guaiacyl acetone
0.17
0.15
0.23
Syringols (dimethoxy phenols)
16.22
15.38
21.52
Syringol
4.33
4.40
5.90
Syringol, 4-methyl
4.28
4.12
5.83
Syringol, 4-ethyl-
0.97
1.01
1.34
Syringol, 4-vinyl
1.05
0.81
1.20
Syringol, 4-propyl-
0.68
0.70
1.00
Syringol, 4-(1-propenyl)- cis
0.31
0.36
2.30
Syringol, 4-(1-propenyl)- trans
1.29
1.19
0.33
Syringaldehyde
1.32
1.02
1.57
Homosyringaldehyde
0.09
0.09
0.00
Dihydrosinapyl alcohol
0.17
0.13
0.17
Sinapyl alcohol, Isomer of
0.16
0.15
0.00
Acetosyringone
0.57
0.58
0.79
Propiosyringone
0.48
0.42
0.51
Syringyl acetone
0.52
0.40
0.58
Total
27.77
26.34
36.49
minimized for run2 (14.4%) and the coke yield is increased
for run3 (42.6%) and run4 (38.0%) compared with that of
run1 (29.4%). When the pyrolysis temperature is increased
from 470
8
C to 560
8
C, the yield of biocrude oil is slightly
decreased for all runs and the coke yield is noticeably
decreased for run7 (15.2%) compared with run5 (30.9%). For
Organosolv lignin at pyrolysis temperature 470
8
C, except for
FCC, the biocrude oil yields are decreased from 50.3% (run9)
to 49.2% and 47.8% and coke yields are decreased from
34.0% (run9) to 25.9% and 26.8% for
biocrude oil yields are increased to 56.8% and 55.5%, and
the coke yields are decreased to 19.7% and 26.4% for run10
and run12, respectively compared with the blank run without
catalyst (52.1% for oil and 28.3% for coke). It is noted that
the catalytic effect of FCC on the coke yield is noticeably
changed both for Alcell and Organosolv lignins with increas-
ing pyrolysis temperature.
Table 2 represents the GC detectable components of bio-
crude oil from the lignin pyrolysis for three runs. The identi-
fied chemical components for three runs are very similar
however the yields of chemical components are different.
run10 and run12,
respectively. With increasing pyrolysis
temperature the
242
July 2012
Environmental Progress & Sustainable Energy (Vol.31, No.2) DOI 10.1002/ep
Figure 3. The quantification of biocrude oil components from GC/MS/FID analysis. [Color figure can be viewed in the online
issue, which is available at wileyonlinelibrary.com.]
Figure 4. The molar mass distribution curves of solid residue obtained from lignin pyrolysis. [Color figure can be viewed in
the online issue, which is available at wileyonlinelibrary.com.]
Environmental Progress & Sustainable Energy (Vol.31, No.2) DOI 10.1002/ep
July 2012
243
Using the GC/MS chromatograms, the quantification of the
chemical compounds in the obtained biocrude oil is carried
out and for simplicity the identified chemical compounds are
classified into their chemical groups. For example, chemical
compounds (alcohols, aldehydes, ketones, furans, catechols,
etc.) representing minor fractions are grouped as ‘‘others’’ in
Figure 3. In the figure, the height of each bar represents the
weight percentage of total GC detectable amounts based on
the collected biocrude oil. For Alcell lignin at pyrolysis temper-
ature 470
8
C (run1-run4), total GC detectable amounts are
slightly decreased especially for syringols when catalysts are
applied. With increasing pyrolysis temperature, total GC
detectable amounts are increased both for run7 and run8
except run6 which is decreased. For Alcell lignin, FCC catalyst
shows the dramatic increase of chemical groups for syringols
and guaiacols with increasing pyrolysis temperature. For Orga-
nosolv lignin, compared with the uncatalyzed runs with the
same pyrolysis temperature, the weight percentage of guaia-
cols is increased at pyrolysis temperature 470
molar mass products to lower ones and this effect was more
pronounced for Alcell lignin than for Organosolv lignin. In
this experiment, deactivation of catalysts and coke formation
occur and their severity may change depending to the start-
ing lignin materials, catalyst type, reaction temperature, etc.
Moreover, the onset of catalytic reaction (e.g., after pyrolysis
or during pyrolysis) may affect
the products. These topics
may be discussed in future work.
ACKNOWLEDGMENTS
This work was financially supported by Alexander von
Humboldt foundation and the authors thank all the collabo-
rative members of Alexander von Humboldt foundation.
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C and those of
guaiacols and syringols are increased at 560
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catalytic pyrolysis with FCC and Olivine. It is noteworthy
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visible for Alcell lignin compared with Organosolv lignin.
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SUMMARY AND CONCLUSIONS
The vTI-mini pyrolyzer was applied to screen the fast
pyrolysis reactions of Alcell and Organosolv lignins involving
catalysts such as HZSM-5, FCC, and Olivine under varying
experimental conditions. The vTI-mini pyrolyzer has two dis-
tinct and fascinating features: First, its rapid screening possi-
bility for pyrolysis reactions, e.g., four to five experiments
can be carried out per day. Second, the biocrude oil can eas-
ily be obtained, and is ready for GC analysis without any fur-
ther treatment by rinsing the quenching tube and micro filter
with a known volume of internal standard solution. The cata-
lytic effect of FCC catalyst on the overall mass balance of
products and reactants was noticeably changed especially
causing the decrease of the coke yield with increasing pyrol-
ysis temperature. As to the quantification of biocrude oil
components, syringols and guaiacols showed distinct
increase or decrease patterns under catalytic pyrolysis condi-
tions. In case of Alcell lignin, FCC catalyst showed dramatic
increase for syringols and guaiacols with increasing pyrolysis
temperature. For Organosolv lignin, it was noted that Olivine
showed the largest total GC detectable amounts. For HZSM-5
catalyst, the GC detectable amounts were the lowest among
the three catalyst runs. From the SEC analysis, it was found
that FCC showed the best performance to convert the higher
244
July 2012
Environmental Progress & Sustainable Energy (Vol.31, No.2) DOI 10.1002/ep
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