1. LIQUEFACTION OF CORN STOVERS AND ACID-CATALYZED HYDROLYSIS
OF RICE STRAWS FOR THE PRODUCTION OF BIO-BASED CHEMICALS
Authors:
Antonino, King Neil A.
Gamet, Arnold A.
Mission, Elaine. G.
Chemical Engineering Department, College of Engineering and Technology
The authors acknowledge the following members of our research team: Krislyn
Laurenciano, Elline Lizette San Juan, Anna Dominique Cheng, Gerald Lim, Michiko Ong
and Bianca Jamila Ludovice; and our panellists: Engr. Clydelle Rondaris, Engr. Milagros
Cabangon, Engr. Denvert Pangayao and Engr. Annalyn Laconsay-Cruz.

2. ABSTRACT
Agricultural wastes such as corn stovers and rice straws that contain lignocellulosic
materials can be used as feedstock for bio-based chemical production. Utilization of
agricultural waste in bio-based chemical production will avoid the unnecessary emission of
greenhouse gases in the atmosphere and will help to address decreasing supply in fossil
fuels. This study explored the utilization of corn stovers and rice straws for the production of
bio-based chemicals such as unsaturated polyester resin (UPR) and furfuryl alcohol,
respectively.
Both corn stovers and rice straws underwent a series of extraction-conversion
processes. Corn stovers, consisting of cellulose, hemicellulose, and lignin, underwent
liquefaction and polyesterification to yield 71.96% of UPR. FTIR analysis confirmed the
presence of ester group at 1719.53 cm-1. On the other hand, rice straws which contain
pentosan, were hydrolyzed and hydrogenized to yield 78.93% of furfuryl alcohol. FTIR
analysis has confirmed the presence of alcohol group at 3338 cm-1.
Keywords: Corn Stovers, Rice Straws, Liquefaction, Acid-Catalyzed Hydrolysis, Unsaturated
Polyester Resin, Furfuryl Alcohol
I. INTRODUCTION
Due to the depletion of coal and petroleum reserves, petroleum-derived chemical
production is largely affected. Hence, there is a need to explore potential alternative
feedstock for the production of industrial chemicals. Biomass is an attractive potential
alternative due to its abundance and lignocellulosic contents that can be extracted and
converted to precursor chemicals. Biomass sources include agricultural crop residues such as
corn stovers and rice straws.

3. In the Philippines, corn stovers and rice straws are generally left in the field after crop
harvesting. Farmers usually burn these in the open field, causing emission of greenhouse
gases such as carbon dioxide (CO2), sulphur dioxide, nitrous oxide (N2O) and particulate
matter (Gadde et al., 2009). They were utilized as feedstock to combustion boilers for
electricity production, however, this results to fouling, slagging, and corrosion of the boiler
due to alkaline and chlorine components in the ash (Zafar, 2013). There had been attempts to
feed them to cattles and sheeps but was not advisable due to its low digestibility and low
protein content (K. S. Gould, 2011). But corn stovers and rice straws were found to contain
high content of lignocellulose. Thus, corn stovers and rice straws are presently underutilized.
Concerning these issues, this study was undertaken to utilized corn stovers and rice straws in
the production of bio-based chemicals by subjecting them to a series of extraction-conversion
process. This study will benefit the agricultural sector by providing them a potential source of
income while protecting the atmosphere from unnecessary greenhouse gas emissions.
Corn stovers were analysed at the Fiber Processing & Utilization Laboratory of the
FIDA, and were found to contain 34.04% cellulose, 37.14% hemicellulose, and 16.80%
lignin on a dry basis (FTUD Report No. 023-14). These components can be subjected to
liquefaction process under acidic conditions using ethylene glycol to produce polyhydric
alcohol or polyol products (Yu et al., 2006). Polyols are chemical compounds containing
multiple hydroxyl groups and these could possibly be used for biopolymer production, such
as unsaturated polyester resins (UPR) through the process of polyesterification (Johnson
Matthey Group, 2003). Unreinforced UPRs are most commonly used for clear casting resins,
coatings, and polyester concrete (for applications such as road drainage). UPRs are also used
for structural parts (e.g. replacement of concrete clad steel), cladding panels, sheeting (e.g.
for pre-fabricated buildings), roofing tiles, pipes and also for applications such as bathroom
furniture (e.g. baths and shower trays).

4. On the other hand, rice straws are known to contain about 16.48% pentosan (Cheng et
al., 2013). This component when subjected to acid hydrolysis and subsequent dehydration
reaction to form furfuraldehyde. Furfuraldehyde is reduced into furfuryl alcohol using
complex sodium borohydrides through the process of hydrogenation (Lecher, Carl S., 2006).
Furfuryl alcohol is an organic compound that is made up of a hydroxymethyl group and a
furan ring. It is utilized as a solvent but is primarily used as an ingredient in the manufacture
of various chemical products such as synthetic resins, adhesives and wetting agent. Other
uses of furfuryl alcohol include its use in rocket fuel, and for wood treatment.
II. METHODS
The experimental procedure was divided into two cases: (1) Production of
Unsaturated Polyester Resin (UPR), and (2) Production of Furfuryl Alcohol. Each case
comprised of three major parts: (1) preparation and conditioning of raw materials, and (2)
extraction of major component, and (3) conversion into main product.
Case 1: Production of Unsaturated Polyester Resin (UPR)
Figure 1 shows the flow of extraction-conversion process in producing UPR
Figure 1. Process Flow Diagram in Producing UPR

5. Corn stovers were gathered through grab sampling from a corn plantation in Brgy.
Laput, Mexico, Pampanga. The reagents were purchased from Chemodities and Patagonian
chemical suppliers located at Bambang, Manila.
1A. Preparation and Conditioning of Raw Materials
Corn stover is a collective term for corn stalks and corn leaves. The weight ratio of
corn leaves and stalks in a corn stover was determined as 3 parts leaves: 7 parts stalks. Corn
leaves were washed using tap water to remove adhering dirt while the stalks were size-
reduced to approximately 1 cm for easier handling. The corn leaves and stalks were dried in a
conventional oven at 105°C to a constant weight (The Royal Society of Chemistry, 2014) for
30 and 60 minutes, respectively. The dried samples were further size-reduced to
approximately 2 mm using a blender to increase the effective surface area of the cellulose and
reduce cellulose crystallinity (Mani et al., 2004; Galbe and Zacchi, 2007). The ground
samples were sieved using a no. 10 USA standard test sieve (with ASTM E-11 Specification)
made of brass frame stainless cloth having an aperture of 2 mm or 0.0787 inch.
1B. Liquefaction of Pre-treated Corn Stover
The undersize from the Tyler sieve, ethylene glycol (liquefying agent) and 18M
sulfuric acid (catalyst) having a ratio of 3:10:100 were placed in an erlenmeyer flask and
were reacted at 160°C for about 60 minutes under atmospheric pressure following the method
by Liang et al., 2006. Under the catalysis of sulfuric acid, the corn stover experienced a
partial chemical degradation and reacts with ethylene glycol to form a series of glucosides as
can be seen in Figure 2 (Liu et al., 2005).
Figure 2. Liquefaction
Reaction of the Corn Stover
Source: Yamada and Ono
(1990), Liu et al. (2005)

6. After the reaction, it was immediately quenched to prevent further degradation,
cleavage, or any unwanted reaction. Then, the liquefied product (polyol) was separated from
the residue through filtration.
1C. Polyesterification of Polyol
Polyol and phthalic acid, having a ratio of 5:1 based from Kunaver et al, 2011, were
placed in an erlenmeyer flask and heated at atmospheric pressure to produce unsaturated
polyester resin. As the process proceeds, the by-product (i.e. water) was continuously
removed to obtain higher conversion and to drive the reaction (see Figure 3) to completion
(Landsverk et. al., 2014).
Polyesterification was executed for about 160 to 180 minutes under 160 to 220ºC
(Simpson et al, 2010). When the reaction proceeded to completion, the mixture was quenched
until it cooled down. It was found out that the best combination of time and temperature for
the process was 170 minutes and 190ºC, respectively.
1D. Cross-linking via Addition of Styrene Monomer
Unsaturated polyester resin was cross-linked with styrene monomer to enhance its
thermosetting properties. The cross-linking reaction of unsaturated polyester resin and
styrene monomer is shown in Figure 4.
Figure 3. Polyesterification
Reaction
Source: Dodiuk, H. and Goodman,
S. (2014). Handbook of Thermoset
Plastics. 3rd
Edition. San Diego,
CA: Elsevier
Figure 4. Cross-linking Reaction of
Unsaturated Polyester Resin and
Styrene Monomer
Source: Dodiuk, H. and
Goodman, S. (2014). Handbook of
Thermoset Plastics, Third Edition.
San Diego, CA: Elsevier Inc.

7. MEKP was used as initiator in the reaction. Unsaturated polyester resin to styrene
ratio was 6:4 by weight. MEKP was added having a concentration of 1% by volume of 100
mL unsaturated polyester resin and was mixed manually for 3 minutes (Osman E. A. et. al.,
2012).
1E. Testing of the Final Product
UPR synthesized was identified using spectroscopic technique of Fourier Transform
Infra-red (FTIR). Testing was done in Adamson University’s FTIR analyzer. Results were
compared to the existing peak value for UPR which is ranging 1700 to 1727 cm-1
. FTIR
analysis falling under this range will indicate the presence of ester group in the product.
Case 2: Production of Furfuryl Alcohol
Figure 5 shows the flow of extraction-conversion process in producing furfuryl alcohol.
Figure 5. Process Flow Diagram in Producing Furfryl Alcohol
2A. Preparation and Conditioning of Raw Materials
50g of rice straws were submerged into water to remove adhering dirt. After washing,
the straws were dried at a temperature of 105°C to constant weight in an air dry oven. Then,
the size of the straws was reduced using a blender to achieve a particle size of 40-80 mesh
size and passed through 40 and 80 mesh sieve trays to collect the undersized rice straws.

8. 2B. Acid-Catalyzed Hydrolysis of Rice Straws
A ratio of 10mL of sulfuric acid for every 1 g of rice straw (10:1) was used in this part
of experimentation. The rice straws and dilute sulfuric acid of 0.24M (1.29%w/w) were
mixed in a 500-mL beaker and heated at 100°C for 30 minutes to break down the pentosan
into pentoses. Then another 30 minutes at 110°C to convert these monomers into
furfuraldehyde as shown in Fig.6. The heated mixture was quenched at room temperature
then subjected in filtration. The filtrate was then introduced to distillation to separate the
furfuraldehyde from the acid catalyst.
Figure 6: Conversion of Pentose to
Furfuraldehyde
2C. Distillation of Filtrate
After extracting the filtrate from the slurry, it was then subjected to distillation to
separate the sulfuric acid and water content from the furfuraldehyde solution. The filtrate was
first heated to 100°C (boiling point of water) for 60 minutes then the water content was
collected. After separating the water, the temperature was raised to 162°C (boiling point of
furfuraldehyde) for 30 minutes to accumulate the furfuraldehyde content. The remaining
content or the bottoms is sulfuric acid since its boiling point is at 337°C.
2D. Hydrogenation of Furfuraldehyde
Figure 7. Conversion of
furfuraldehyde to furfuryl
alcohol

9. From the stoichiometry, every one mole of furfuraldehyde obtained from distillation was
reacted with 0.25 moles of sodium borohydride and 0.75 moles of water as shown in Fig. 7.
The resulting solution was continuously stirred for 10 minutes while maintaining a
temperature of 25°C. The precipitate formed (sodium borate) was separated from the
supernate layer by centrifugation.
2E. Testing of the Final Product
Furfuryl Alcohol synthesized was identified using spectroscopic technique of Fourier
Transform Infra-red (FTIR). Testing was done in Adamson University’s FTIR analyzer.
Results were compared to the existing peak value for furfuryl alcohol which is ranging from
3200 cm-1
to 3640cm-1
. FTIR analysis falling under this range will indicate the presence of
alcohol group in the product.
III. RESULTS AND DISCUSSION
Case 1:
1A. Liquefaction of Corn Stover
The percent conversions for all the trials are shown in Table 1. Based on the
experiment, the average percent conversion of all the trials has minimal differences indicating
that repeatability of the process.
Table 1. Liquefaction of Corn Stover
Parameter Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average
Amount of Corn Stover (g) 23.4 23.7 23.7 24.1 23.4 23.7
Mass of Ethylene Glycol (g) 78.0 79.0 79.0 80.3 78.0 78.9
Mass of 18M Sulfuric Acid (g) 0.702 0.711 0.711 0.723 0.702 0.710
Mass of Slurry (g) 98.87 99.17 100.68 97.51 98.74 99.00
Mass of Cake (g) 17.85 19.66 22.43 17.83 17.09 18.97
Mass of Dried Cake (g) 12.56 13.11 12.69 12.97 12.76 12.82
Mass of Polyol (g) 76.43 74.63 73.66 75.66 77.54 75.58
Conversion (%) 53.24 50.79 52.80 52.50 52.28 52.32
The liquefied corn stover consisted of degraded stover fragments (oligosaccharides),
glucosides, and residual and decomposed liquefying reagents, all of which contained two or

10. more hydroxyl groups. The extracted product’s FTIR spectra were nearly the same as with
the standard spectra of polyol as shown in Figure 5.
Figure 9. Comparison between Extracted Polyol and FTIR Spectra of Standard Polyol:
(a) FTIR Spectra of Polyol Extracted tested by Fourier Transform Infrared Spectroscopy
Testing, Adamson University, 2014, and (b) FTIR spectra of the liquefied biomass-based
polyols of wood under conventional bath heating (Zheng et al., 2011)
1B. Polyesterification of Polyol
Using Design of Experiments (DOE) with two-factorial optimization having no
replication, combinations of optimal temperature and time for polyesterification were
randomly selected to avoid biases. Table 2 shows the variations suggested by DOE in
optimizing time and temperature. The combination of third trial gave the highest percent
yield amounting 71.96% wherein the time and temperature were equal to 170 minutes and
190ºC, respectively.
Table 2. Polyesterification of Polyol
Parameter Trial 1 Trial 2 Trial 3 Trial 4 Trial 5
Weight of Polyol (g) 76.43 74.63 73.66 75.66 77.54
Weight of Phthalic Acid (g) 15.29 14.93 14.73 15.13 15.51
Weight of By-product (g) 8.97 9.13 9.83 10.43 10.56
Weight of UPR (g) 56.67 58.75 63.61 65.39 67.03
Yield (%) 61.79 65.60 71.96 72.02 72.03
Copolymerization with an unsaturated monomer such as styrene forms the three-
dimensionally cross-linked polymer (i.e. unsaturated polyester resin). The unsaturated
polyester resin refers to the liquid resin made by the solution of unsaturated polyester alkyd
in styrene monomer.

11. 1C. Cross-linking with Styrene Monomer
Cross-linking of unsaturated polyester resin with styrene monomer resulted to a
homogeneous solution because both are non-polar liquids. The unsaturated polyester resin
that was mixed with styrene monomer and MEKP gave a less viscous resin. A total yield of
92.22% of unsaturated polyester resin was produced.
1D. Testing of the Final Product
The final product’s FTIR spectra conformed to the standard spectra of unsaturated
polyester resin as presented in Figure 10.
Figure 10. FTIR Spectra of Standard and Extracted Unsaturated Polyester Resin
Source: Fourier Transform Infrared Spectroscopy Testing, Adamson University, 2014
Case 2:
Based from the analysis conducted by FIDA, rice straw sample contains 34.32%
hemicellulose in which 90% represents the pentosan. The experiment aims to produce
furfuryl alcohol from the acid catalyzed rice straw through hydrogenation. The percent yield
was computed to determine the amount of furfuryl alcohol recovered after conducting the
process.
2A. Acid Hydrolysis of Rice Straw
The parameters used in the acid-catalyzed hydrolysis produced furfuraldehyde are
shown in Table 3. However, the concentration of the sulfuric acid used (0.24M) is not fitted
for the process because it obtained a small amount of furfuraldehyde from the solution.

12. Further increasing the concentration may yield a higher conversion of pentosan to
Furfuraldehyde.
Table 3. Acid hydrolysis of Rice Straw
2B. Distillation of Furfuraldehyde
The parameters used in the distillation of furfuraldehyde solution are suitable for the
process as shown in Table 4. The average amount of furfuraldehyde recovered is 2.63g.
Table 4. Distillation of Pentose
2C. Hydrogenation of Furfuraldehyde
For the three replicates of hydrogenation subjected to the same parameters, the final
amount of furfuryl alcohol solution are close to one another as shown in Table 6. The
average value of Furfuryl alcohol obtained from the three replicates has a yield of 78.93%
from the process. The Furfuryl alcohol obtained from centrifugation was then subjected to
distillation and tested through Fourier Transform Infra-red (FTIR) Analysis.
Table 6. Hydrogenation of Furfuraldehyde
Trial 1 2 3 Mean
Ratio of RS to H2SO4 sol’n (g:mL) 1:10 1:10 1:10 1:10
Ground Rice Straw (g) 30.76 30.69 30.01 30.49
H2SO4 sol’n (mL) 307.60 306.90 300.10 304.87
Amount of Filtrate (g) 298.94 299.91 299.11 299.32
Amount of Cake (g) 42.69 41.65 41.77 42.04
Trial 1 2 3 Mean
Amount of Feed (g) 298.94 299.91 299.11 299.32
Time of 1st
Distillation (min) 60 60 60 60
Amount of 1st
Distillate (g) 282.43 283.36 282.60 282.80
Time of 2nd
Distillation (min) 10 10 10 10
Amount of 2nd
Distillate (g) 2.63 2.64 2.63 2.63
Amount of Bottoms (g) 4.01 4.01 4.01 4.01
Trial 1 2 3 Mean

13. 2D. Testing of the Final Product
Furfuryl Alcohol synthesized was identified using spectroscopic technique of Fourier
Transform Infra-red (FTIR). Testing was done in Adamson University’s FTIR analyzer. The
standard furfuryl alcohol has the range peak value of 3200-3640 cm-1
. The alcohol obtained
satisfied the properties required by standard especially the FTIR peak value in which it shows
to be 3338.16 cm-1
as shown in Fig.11.
Figure 11. FTIR spectra of produced furfuryl alcohol
A. CONCLUSION
This study confirms that corn stover and rice straw were potential to be a raw material
for the production of unsaturated polyester resin and furfuryl alcohol respectively.
Unsaturated Polyester Resin can be produced from corn stover via liquefaction to obtain
polyol and then by polyesterification of polyol. Also, Furfuryl Alcohol can be produced from
rice straw thru acid catalyzed hydrolysis of rice straw to obtain the furfuraldehyde content
and then by hydrogenation of furfuraldehyde. The results of FTIR analysis confirmed that the
bio-based chemicals could be produced from agricultural biomass.
REFERENCES:
Furfuraldehyde (g) 2.63 2.64 2.63 2.63
Sodium Borohydride (g) 0.26 0.26 0.26 0.26
Water (g) 0.37 0.37 0.37 0.37
Residue (g) 0.57 0.57 0.57 0.57
Furfuryl Alcohol (g) 2.69 2.70 2.69 2.69

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