Biomass Combustion Study: Model Compounds of Lignin Pyrolysis
Literature Review
Sandor Rosta
November 15, 2004
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The goal of my research is to identify
the model compounds associated with
the pyrolysis of the biomass constituent
lignin. This is being done as part of a
larger
study
aimed
at
further
understanding
the
combustion
chemistry of biomass gasification and
how it relates to wild land fires.
Biomass materials like wood and plants
are essentially composite materials of
organic
polymers
comprised
of
cellulose, hemicellulose, lignin, and
extractive compounds like oils, and
waxes. There is evidence that biomass
combustion
behaves
as
the
superposition of the combustion
chemistry of these constituent parts
[6,7,9].
Lignin is the second most abundant
organic substance on earth [16]. Its
primary biological function is to provide
plants with strength and durability.
Lignified tissures are comparable to
fiber-reinforced plastics in which the
lignin represents the plastic binder and
the cellulose the reinforcing fibers [15].
Lignin is a high–molecular-mass
randomly
cross-linked
polymer
consisting of an irregular array of
differently bounded hydroxy- and
methoxy- substituted phenyl-propane
units [7]. The removal of lignin from
wood is a major concern in the
chemical pulping of wood for paper
production, which is one of the ten
largest industrial activities in North
America [15]. About 50 million tons of
chemically separated lignins are
produced annually throughout the
world, of which about 1% is currently
sold [15]. So a further understanding of
the chemistry of lignin is necessary to
be able to use this resource to its fullest
potential.
Biomass pyrolysis involves heating of
raw biomass or organic waste material
in the absence of an oxidizer in order to
extract reaction products for later
application [6]. Though lignin has been
studied extensively, literature related to
the pyrolysis of lignin is scarce [2].
This is unfortunate since a major
component of my work depends on
compiling pyrolysis products from the
existing literature. Since that body of
work isn’t that extensive, I don’t have a
big frame of reference to compare
results with.
The studies I found that do focus
primarily on lignin pyrolysis were done
for a variety of reasons. Investigations
into using lignins for alternative fuels [2]
was considered, also identifying
specific biomass source materials from
sampling
fire
emissions
[11].
Experiments were done to determine
various kinetic parameters like primary
and secondary reactions of lignin
pyrolysis products [14], and primary
pyrolysis of Kraft lignin at high heating
rates [8]. And one experiment was
conducted to validate the use of
pyrolysis-gas
chromatography-mass
spectrometry (Py-GC-MS) [5].
The most significant aspect of these
studies to me, are the tables of
pyrolysis products formed. It is known
that the pyrolysis reaction of lignin is
strongly influenced by temperature,
heating rate, and the nature of the
carrier gas. Also, the nature of lignin,
its composition, and various functional
groups have significant effects on the
lignin, conversion, and product yields
[2]. So, since the conditions under
which these experiments have been
done are different, comparing the
results from each one and drawing
conclusions about the most significant
products is a non-trivial task.
Another important factor in these
pyrolysis experiments is the type of
reactor used, and under what
conditions. A fixed-bed reactor was
used in [2] under and Kraft Lignin was
heated from 298-1073 K. In [5] all
analyses were performed using a CDS
Pyroprobe 1000 heated filament
pyrolyzer at 200 C and 290 C. Another
Pyroprobe 1000 was used in [8] and
heated up to 1000 C.
In [11], the
combustion experiments were carried
out in a traditional brick fireplace in an
older single-family home.
No
temperature was given about the fire,
but the instrument analysis reports a
temperature programming of injecting
sample at 65 C and then heating at 10
C/min for 21 min and then holding at
275 C for 21 minutes. In [13] pyrolysis
was performed with ferromagnetic
wires having a Curie temperature of
510 C, held at 50C for 3 min, and
programmed to 250 C at a rate of 3
C/min. In [14], stainless steel microtube
bomb under heating conditions that are
unclear.
The string of continuity that runs
through most of the experiments in the
literature is the method of species
detection.
Pyrolysis
thermally
degrades
polymers
into
small
fragments which are separated by gas
chromatography and identified with
mass spectrometry [5]. [2,5,8,12,15,17].
Thermogravimetric analysis is also
performed [2].
Since the literature
results were somewhat limited to the
topic directly related to my area, I
broadened my search a little to include
related topics. The methods used in [3]
and [10] are very similar to methods
used to study lignin pyrolysis, but they
are
focused
on
the
cellulose
compound.
The represented data
doesn’t explicitly apply to my study, but
insight can be gained from their
experimental methods. Also included
are general biomass pyrolysis studies
[4,6,7,9,12]. These studies consider all
components of biomass including
lignin. The problem with their reports is
that they don’t account for all the
species that each component breaks
into, the just lump all the effects into
lignin, or hemicellulose.
They are
useful though as precedence for what
results should be obtained when the
time comes to run simulations on the
model compounds that I need to
determine.
1. Brown, AL; Hames, BR; Daily, JW; et al. “Chemical analysis of solids and
pyrolytic vapors from wildland trees” ENERGY & FUELS, 17, 1022-1027 (2003)
2. Ferdous, D; Dalai, AK; Bej, SK; et al. Pyrolysis of lignins: Experimental and
kinetics studies,” ENERGY & FUELS, 16 (6): 1405-1412 (2002)
3. Brown, AL; Dayton, DC; Daily, JW, “A study of cellulose pyrolysis chemistry
and global kinetics at high heating rates,” ENERGY & FUELS, 15 1286-1294
(2001)
4. Zhou, XY; Mahalingam, S, “Evaluation of reduced mechanism for modeling
combustion of pyrolysis gas in wildland fire” COMBUSTION SCIENCE AND
TECHNOLOGY, 171, 39-70 (2001)
5. Bocchini, P; Galletti, GC; Camarero, S; et al. “Absolute quantitation of lignin
pyrolysis
products
using
an
internal
standard,”
JOURNAL
OF
CHROMATOGRAPHY A, 773 (1-2): 227-232 (1997)
6. Miller, RS; Bellan, J, “A generalized biomass pyrolysis model based on
superimposed cellulose, hemicellulose and lignin kinetics,” COMBUSTION
SCIENCE AND TECHNOLOGY, 126 97-137 (1997)
7. Alen, R; Kuoppala, E; Oesch, P, “Formation of the main degradation
compound groups from wood and its components during pyrolysis,” JOURNAL
OF ANALYTICAL AND APPLIED PYROLYSIS, 36, 137-148 (1996)
8. Caballero, JA; Font, R; Marcilla, A, “Study of primary pyrolysis of Kraft lignin
at high heating rates: yields and kinetics,” JOURNAL OF ANALYTICAL AND
APPLIED PYROLYSIS, 36, 159-178 (1996)
9. Raveendran, K; Ganesh, A; Khilar, KC, “Pyrolysis characteristics of biomass
and biomass components,” FUEL, 75, 987-998 (1996)
10. Antal, MJ; Varhegyi, G, “Cellulose Pyrolysis Kinetics - The Current State
Knowledge, “INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 34 703717 (1995)
11. Simoneit, BRT; Rogge, WF; Mazurek, MA; et al. “Lignin Pyrolysis Products,
Lignans, and Resin Acids as Specific Tracers of Plant Classes in Emissions from
Biomass Combustion,” ENVIRONMENTAL SCIENCE & TECHNOLOGY, 27
2533-2541 (1993)
12. Evans, RJ; Milne, TA, “Molecular Characterization of the Pyrolysis of
Biomass .1. Fundamentals,” ENERGY & FUELS, 1 123-137 (1987)
13. Saizjimenez, C; Deleeuw, JW, “Lignin Pyrolysis Products - Their Structures
and Their Significance as Biomarkers,” ORGANIC GEOCHEMISTRY, 10 869876 (1986)
14. Jegers, HE; Klein, MT, “Primary and Secondary Lignin Pyrolysis Reaction
Pathways,” INDUSTRIAL & ENGINEERING CHEMISTRY PROCESS DESIGN
AND DEVELOPMENT, 24 173-183 (1985).
15. B. L. Browning, “The Chemistry of Wood”, Interscience Publishers, London,
(1963).
16. Glasser W. G., Northey, R. A, Schultz, T. P., “Lignin: Historical, Biological,
and Materials Perspectives”, ACS Symposium Series 742, American Chemical
Society, Washington D. C. (2000)