Arabian Journal for Science and Engineering
https://doi.org/10.1007/s13369-018-3245-8
RESEARCH ARTICLE - CHEMICAL ENGINEERING
Biodiesel Production in Tubular Microreactor: Optimization
by Response Surface Methodology
Preena Shrimal
1
· Himanshu Sanklecha
1
· Pritam Patil
2
· Arun Mujumdar
3
· Jitendra Naik
1
Received: 17 October 2017 / Accepted: 1 April 2018
© King Fahd University of Petroleum & Minerals 2018
Abstract
Transesterification of crude cottonseed oil with methanol in the presence of catalyst (NaOH) in tubular microreactor has
been investigated experimentally. The transesterification reaction was performed in a silicon tube of 0.8 mm inner diameter,
mounted in serpentine manner configuration on an acrylic sheet. Influence of process variables such as reaction temperature
(35−45
◦
C), NaOH concentration (0.5–1.5 wt%) and oil/methanol molar ratio (1:7–1:9) on fatty acid methyl ester (FAME)
was studied. In order to further improve biodiesel yield, an experimental design was employed using the Box–Behnken method
and analysis of variance. The %FAME was calculated by gas chromatography using methyl arachidate as an internal standard.
Fourier transform infrared spectroscopy was used to investigate the functional groups present in biodiesel. Thermal stability
of biodiesel was evaluated using a thermogravimetric analyser. The optimal condition found was oil/methanol molar ratio
(1:8), catalyst concentration (1wt%) and reaction temperature (45
◦
C) while %FAME yield of about 94.1% at a residence
time of 90 s.
Keywords Tubular microreactor · Crude cottonseed oil · FAME · Response surface methodology
1 Introduction
Depletion of fossil fuel resources and several environmen-
tal issues have attracted the attention of many researchers
in developing renewable and clean alternative fuels [1]. Due
to this, more consideration has been paid to produce bio-
fuels such as biodiesel which are renewable, biodegradable
and non-toxic, with high flash point and good greenhouse
emission profile [2,3]. Biodiesel is the free fatty acid methyl
ester (FAME) derived from vegetable oils and animal fats
[4]. When vegetable oil and animal fats reacts with alco-
hol (methanol/ethanol) in the presence of a catalyst (acid,
B
Jitendra Naik
jbnaik@nmu.ac.in
1
Department of Chemical Engineering, University Institute of
Chemical Technology, North Maharashtra University,
Umavi Nagar, Jalgaon, Maharashtra 425001, India
2
SVMIT, College of Engineering, Bharuch, Gujarat 392001,
India
3
Department of Chemical and Biochemical Engineering,
Western University, London, ON, Canada
base, and enzymatic catalyst) alkyl ester that is biodiesel and
glycerol as a spin-off are produced. Generally, selection of
catalyst depends upon the free fatty acid (FFA) content of
oil. Usually, a homogenous alkali catalyst, NaOH or KOH
is preferred due to their operational simplicity, high cat-
alytic activity and greater yield. NaOH is economically more
favourable over KOH which is its key advantage. Further-
more, NaOH has low molecular weight compared to KOH
it will have higher molar concentration even though weight
concentration is equal and hence less amount of catalyst will
be required. Widely preferred alcohol for the transesterifica-
tion reaction is methanol owing to its low cost, physical and
chemical advantages and its ability to quickly dissolve the
alkali catalyst [5].
Although, numerous literature has revealed the impor-
tance of biodiesel, especially with respect to future energy
needs and environmental issues, implementation of biodiesel
still poses some problems [6,7]. Unavailability of suffi-
cient cost-effective feedstock and large production time has
increased the cost of biodiesel, which is a major obstacle to
its commercialization.
Generally, biodiesel is prepared by various methods in
batch reactors such as transesterification, pyrolysis and
microemulsification [8]. However, these methods are very
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