Characteristics of fast pyrolysis of corncob using ZnCl2 for the production of
furfural and acetic acid
Seung-Jin Oh, Gyung-Goo Choi, Su-Hwa Jung and Joo-Sik Kim*
Faculty of Energy and Environmental System Engineering, University of Seoul, 90 Jeonnong-Dorhng,
Donggaemun-Gu, Seoul 130-743, Republic of Korea
e-mail: pysoo80@gmail.com; +82 2 6490 2868

Abstract
Corncob was pyrolyzed using ZnCl2 in a pyrolysis plant equipped with a fluidized bed reactor to produce furfural andacetic acid. The effects of reaction temperature and the ZnCl2 content on the yields of furfural and acetic acid wereinvestigated. The pyrolysis was performed within the temperature range between 310-410 °C, and the bio-oil yield were30-58 wt% of the product. The furfural and acetic acid yields were 2 wt% and 13.1 wt%, respectively, when a corncob
mechanically mixed with 20 wt% ZnCl2 was pyrolyzed. Except water, these two compounds were the main compounds inthe bio-oils. The high selectivity for furfural and acetic acid in the bio-oil obtained with ZnCl2 would make the fast pyrolysis
very economically attractive, because a high recovery efficiency of the two compounds from bio-oil can be expected.

Keywords: Acetic acid, Furfural, Corncob, Pyrolysis, Fluidized bed, Bio-oil

1. Introduction
Recently, the demand of fine chemicals has been
increasing due to the rapid development of chemicalindustry. One of these fine chemicals is furfural which aplatform chemical with a growing market. It has been
widely used as a solvent, food additive and fungicide andalso in the manufacture of pharmaceutical products,
resins, and etc [1]. In contrast to most conventional finechemicals which are generally petroleum-based, furfuralis exclusively produced from renewable biomass
resources. Industrial furfural production is presentlyconducted by acid catalytic dehydration of pentosancontaining lignocellulosic materials in a batch orcontinuous reactor [2]. Since this type of production
method brings about tons of acid waste water, ecofriendly production methods have been passionately
being researched. A promising alternative to the aciddehydration for the production of furfural is the pyrolysis
of lignocellulosic biomasses consisting of cellulose,
hemicelluloses, and lignin. For the furfural production bypyrolysis, corn residues such as corn stover and corncob,
have been usually used. In particular, corncob is thewidely used feedstock due to its rich contents ofpentosans and cellulose among the common biomass
materials. Meanwhile, acetic acid is an importantchemical reagent and industrial chemical, mainly used in
the production of cellulose acetate and polyvinyl acetate,
as well as synthetic fibres and fabrics. Recently, about
75% of acetic acid made for use in the chemical industry
is made by the carbonylation of methanol. Main aim of
this study is to find the effects of reaction conditions, theZnCl2 content on the yields of furfural and acetic acid.

The quantification of furfural and acetic acid in the bio-oil
was performed with the GC external standard method.

2. Materials and Methods
Material. The feed material, corncob, was obtained froma farm in Korea. It was first ground using a grinder, andthen sieved to obtain material with a diameter 0.425-1
mm. The material was then dried in an oven at 105 °C for
72 hr and was then used in each operation.
Pyrolysis plant and procedure. The fast pyrolysis plant
was composed of a feeding system, fluidized bed reactor,
char separation system, quenching system and productgas circulation system. A diagram of the plant is shown inFig. 1.
Fluidized Bed
Reactor

PIR

TIR
PIR

Electrostatic
FilterSilo
TIR

Vibrator

TIR

CyclonePIR

Hot filter

Water
Steel
Condenser

EtOH

EtOH

M
Container(Liquids)

TIR

Screw

Container(Liquids)

HeaterContainer(Liquids)

Glass Condenser

M
Screw

Container(Liquids)

TIR

Water Jaket
PIR

HeaterPre Heater

Flare

Compressor
PIR

TIR

Gas meter

Check ValveGas sampling

NFig. 1 Pyrolysis plant
The key part of the plant is the fluidized bed with a heightof 390 mm and an inner diameter of 110 mm, which ismade of a 316 SS tube. To monitor the reaction
temperature and fluidization behavior during pyrolysis,
three thermocouples are installed inside the reactor. The
pyrolysis reaction temperature is determined by theaverage value of the three thermocouples. The fluidized

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

bed reactor is heated indirectly in an electric heater. Thefeeding system is comprised of two screw feeders which
help load material uniformly and directly into sand in thefluidized bed. To avoid a reflow of pyrolysis vapor into thefeed system, part of the product gas is introduced into
the silo and feeder during experiment. The char
separation system is composed of a cyclone and ceramic
hot filter designed to capture particle bigger than 10 and
2 µm, respectively. The quenching system consists of
one water-cooled steel condenser and two ethanolcooled glass condensers, which operate at 20 and -25 °C,
respectively. To capture aerosols, an electrostatic
precipitator behind the condensers is used. Part of theproduct gas is either burned in a stack to regulate thepressure in the plant or is used for gas sampling. Much of
the product gas is circulated into the fluidized bed reactor
through a pre-heater using a compressor for fluidization.
Reaction condition. In each experiment, the input of
the feed material was 100 g, and 2.6 kg quartz sand witha mean diameter of 0.4 mm was used as the fluidized
bed material. The feed rate was about 2 g/min, and theproduct gas was used for the fluidizing medium. To
maintain a constant residence time of pyrolysis vapor in
the reactor, the flow rate of product gas was correctedwith respect to the reaction temperature. Main reaction
conditions are shown in Table 1.

Reaction
temperature (°C)
Feed rate (g/min)
Flow rate (NL/min)

12Run
345311357411356

358

3636

102023836

Feed size (mm)ZnCl2 content (wt%)

33
0.425-1

0Table 2. Mass balance
Oil(water)Gas

148.2(57)17.7

252.7(57)21.5

Run358.3(56.9)
24.34
46.3
(62.4)
16.8

5
29.8(68.1)
14.9

Char

34.1

25.8

17.5

36.9

55.3

Products (wt%)

Effects of reaction parameters on the furfural andacetic acid yields. Table 3 shows the influences ofreaction temperature and the ZnCl2 content on the
furfural and acetic acid yields. In the absence ZnCl2, thefurfural yield increased, then maximized and finallydecreased with increasing reaction temperature from 311
to 411 °C; whereas the acetic acid concentration wasgradually increased. With increasing the ZnCl2 content,
the furfural and acetic acid yields gradually wasincreased.
Table 3. Yields of furfural and acetic aicd
Yield (wt%)
FurfuralAcetic acid

10.2
4.6

2
0.8
6.2

Run
30.6
9.9

4
1.4
10.4

52
13.1

4. Conclusions

Table 1. Reaction conditions
Parameterswith the water content of about 57 wt%. With increasing
the amount of ZnCl2, the bio-oil yield strongly wasreduced.

Main reaction parameter was reaction temperature(Effects of other parameters will also be presented inconference). Also, the effect of the ZnCl2 content on theyields of furfural and acetic acid were investigated. To
see the influence of reaction temperature on the productspectrum, Runs 1 to 3 were conducted; to find theinfluence of the ZnCl2 content in the mechanical mixing,
Runs 4 and 5 were carried out for comparison with Run 2.
Analysis of products. Pyrolysis products were divided
into three fractions: bio-oil, gas and char. The watercontent of each bio-oil was measured using a Karl
Fischer titrator. Bio-oil was qualitatively and quantitativelyanalyzed by comparing the peaks obtained by a GC-FID
and a GC-MS. For the quantification of furfural and aceticacid in bio-oil, a calibration curve for each compound wasestablished using standard solutions. The concentrationof each compound in a bio-oil sample could begraphically determined. The pyrolysis gases wereanalyzed offline using GC-TCD and GC-FID, with argon
as the carrier gas

In this study, a bench scale fast pyrolysis of corncob wasconducted to co-produce furfural and acetic acid, and theeffects of reaction temperature and the ZnCl2 content on
the yields of furfural and acetic acid were investigated.
The pyrolysis was performed within the temperaturerange between 310-410 °C. The bio-oil yield was 30-58
wt% of product. The main compounds of bio-oil obtained
were acetic acid, hydroxyacetic acid, furfural andhydroxyacetone. The furfural yield was positively
influenced by the increasing ZnCl2 content, and its
maximum yield was 2 wt% of the product. Under thesame conditions, the maximum acetic acid yield (13.1wt% of the product) was achieved

References[1] Chang-qing Dong and Qiang Lu. Selective fastpyrolysis of biomass impregnated with ZnCl2 to produce
furfural: Analytical Py-GC/MS study. J. Anal. Appl. Pyrol.
(2011) 90, 204-212.
[2] C. Branca and C. Di Blasi. Biomass screening for theproduction of furfural via thermal decomposition. Ind. Eng.
Chem. Res (2010) 49, 2658–2671.

3. Results and Discussion
Product distribution. In all experiments, mass balanceswere established. Table 2 shows product mass balancesof the experiments. In the case of the bio-oils obtained
without ZnCl2, the bio-oil yield was between 48-58 wt%
7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013