Effect of Anode Depth in Synthesis of Biodiesel using the Anodic Plasma Electrolysis Method
Corresponding email: nelsonsaksono@gmail.com
Published at : 24 May 2019
Volume : IJtech
Vol 10, No 3 (2019)
DOI : https://doi.org/10.14716/ijtech.v10i3.2919
Saksono, N., Junior, A.B., Anditashafardiani, R., Muharam, Y., 2019. Effect of Anode Depth in Synthesis of Biodiesel using the Anodic Plasma Electrolysis Method. International Journal of Technology. Volume 10(3), pp. 491-501
| Nelson Saksono | Department of Chemical Engineering, University of Indonesia, Kampus Baru UI Depok, West Java, 16424, Indonesia |
| Adream Bais Junior | Department of Chemical Engineering, University of Indonesia, Kampus Baru UI Depok, West Java, 16424, Indonesia |
| Ratih Anditashafardiani | Department of Chemical Engineering, University of Indonesia, Kampus Baru UI Depok, West Java, 16424, Indonesia |
| Yuswan Muharam | Department of Chemical Engineering, University of Indonesia, Kampus Baru UI Depok, West Java, 16424, Indonesia |
Plasma electrolysis is a process of
electrolysis that uses a DC current to excite electrons in the electrolyzed
solution. The method is very prolific in producing hydroxyl radical (OH•),
which is then used to react with methanol and form a methoxyl radical (CH3O•).
Methoxyl radical is used to break the bond of triglycerides to form methyl
ester (biodiesel) and glycerol. The purpose of this study is to obtain a good
quality and quantity of biodiesel by examining the effect of anode depth with a
constant contact area where the anode is the spot of plasma formed. The solution
used contains Refined,
Bleached, and Deodorized Palm Oil and methanol with a molar ratio of 1:24 and a concentration of KOH
1%-wt. The variations of anode depth are 0.5 cm, 1.5 cm, and 3.5 cm below the
surface of the solution, with 5 mm as the constant contact area. The results of
this research show an improvement in efficiency, as indicated by yield, and the
energy consumption of biodiesel synthesis with increasing depth of the anode.
The maximum yield was reached at an anode depth of 3.5 cm, which produced
96.09% as a biodiesel yield with 0.039%-vol water content, 0.138 as the acid
number, and a specific energy requirement of 0.909 kJ/ml.
Anode depth; Anodic plasma; Biodiesel; Plasma electrolysis
The application of
plasma electrolysis has proven to be effective in the production of valuable
products, such as hydrogen, with a low consumption of energy (Saksono et al.,
2016). The method has also been proven to degrade complex organic waste, such
as phenol (Saksono et al., 2015). The application of the technology to
biodiesel production is an interesting topic to explore due to the fact that
biodiesel is attracting global attraction as an alternative fuel type owing to
its biodegradability and environmental friendliness (Haron et al., 2017). The
synthesis of biodiesel using the plasma electrolysis method offers a
breakthrough because it can accelerate the rate of synthesis and reduce
specific energy consumption, compared to the conventional methods (Saksono et
al., 2018).
Conventional
biodiesel synthesis using Crude Palm Oil (CPO) generally employs the
transesterification, or alcoholysis, reaction method of triglycerides using a
homogeneous catalyst in the form of an acid catalyst (H2SO4,
HCl) and alkaline (NaOH, KOH). It is most common for alkaline catalysts to be
used in the production process of biodiesel plants due to the speed and ease of
the process. However, the process also has the disadvantage of forming
significant volumes of water and soap from a sapling reaction, which results in
a decrease in the quality of the catalyst used. In addition, the method is
characterized by its slow reaction rate and a tendency
Plasma, on the
other hand, produces a large amount of methoxyl radical (CH3O•)
(Zong et al., 2009) that will react with triglycerides to form biodiesel.
Plasma can be either cathodic or anodic, depending on the electrode where the
plasma is formed. In general, plasma is more stable and easily formed in the
cathode than the anode because the cathode emits more secondary electrons
(Bruggeman & Leys, 2009). Plasma electrolysis is a process of electrolysis
that uses a DC current to form electric sparks as a result of the electrons
undergoing plasma excitation in the electrolyzed solution (Saito et al., 2015).
Initially, methanol is mixed with potassium hydroxide to produce the species shown in Equation 1 (Lotero et al., 2005). In the plasma electrode, the high-energy electrons produced by the plasma will break apart water molecule into radicals and transform methoxyl ions into methoxyl radicals (Zong et al., 2009). Meanwhile, on the other electrode, where there is no plasma, a conventional electrolysis reaction will take place that produces ions (Kozáková, 2011). Using anodic plasma, the reactions denoted in Equations 2 and 3 occur in the anode, while the reaction in Equation 4 takes place in the cathode.
The methoxyl radicals produced by those reactions will attack the triglycerides in palm oil and produce methyl esters (Lotero et al., 2005). In general, the mechanism consists of three stages as shown in Figure 1 (Lee et al., 2009). The first stage is a nucleophilic alkoxide attack producing a tetrahedral intermediate. The second stage is the formation of alkyl ester and anion diglyceride. The third stage is the regeneration of the active species that will react with the second molecule of the other alcohol, followed by the recovery of the base catalyst.
Figure 1
Hypothesis of reaction mechanisms (Lee et al., 2009)
In previous research (Saksono et al.,
2018), the synthesis of biodiesel using plasma electrolysis has been proven to
produce biodiesel products. This research aims to increase the effectivity of
the plasma electrolysis method to produce biodiesel. The main objective of this
study was to observe the effect of the depth of the anode (which is partially
coated by quartz glass) in the solution, where the plasma formation takes place
in the anode. The contact area between the anode and solution will remain
constant, even when the anode depth is increased; this is done by using a
quartz glass coating, which will be explained further in the next section. The
effect of anodic plasma depth with a constant anode contact area is crucial
because a deeper anode position will affect the amount of energy consumed
(Bismo et al., 2013).
This
research has observed the effect of anode depth on biodiesel synthesis
effectivity, with the results relating to the yield and specific energy
requirement of biodiesel. It was found that the greater the depth of the anode,
the higher the yield achieved, with the highest yield of 96.09% achieved at an
anode depth of 3.5 cm. At the same time, the specific energy requirement of
biodiesel also increases in line with anode depth, with the lowest specific
energy requirement for biodiesel synthesis of 0.809 kJ/mL recorded at a depth
of 0.5 cm. Based on the quantity of methyl ester content, kinematic viscosity,
density, and acid number, this biodiesel research is qualified according to SNI
7182:2015. The water content conforming with SNI 7182:2015 occurs only with
biodiesel produced at an anode depth of 3.5 cm.
This research was partially funded by Hibah Penelitian Dasar
Kemenristekdikti
with
Contract No. NKB-1654/UN2.R3.1/HKP.05.00/2019. The authors declare no competing interests or
any conflicts of financial interests.
Alacón, R., Malagón-Romero, D.,
Ladino, A., 2017. Biodiesel Production from Waste Frying Oil and Palm Oil
Mixtures. Chemical Engineering
Transactions, Volume 57, pp. 571–576
Bismo, S., Irawan, K., Karamah, E.F., Saksono, N., 2013. On the Production
of OH Radical through Plasma Electrolysis Mechanism for the Processing of
Ammonia Waste Water. Journal of Chemistry
and Chemical Engineering, Volume 7(1), pp. 6–12
Boocock, D.G., Konar,
S.K., Mao, V., Lee, C., Buligan, S., 1998. Fast Formation of High Purity Methyl
Ester from Vegetable Oils. Journal of the
American Oil Chemists’ Society, Volume 75(9), pp. 1167–1172
Bruggeman, P.,
Leys, C., 2009. Non-thermal Plasmas In and In Contact with Liquids. Journal of
Physics D: Applied Physics, Volume 42(5), 53001
Devitria, R.N.,
Anita, S., 2013. Sintesis Biodiesel dengan
Katalis Heterogen Lempung Cengar yang Diaktivasi dengan NaOH: Pengaruh Waktu
Reaksi dan Rasio Molar Minyak: Metanol (Synthesis of Biodiesel with
Heterogeneous Catalysts of Cengar Clay Activated with NaOH: Effect of Oil
Reaction Time and Molar Ratio: Methanol). Indonesian
Chemia Acta, Volume 3(2), pp. 39–44
Gao, J., Wang,
X., Hu, Z., Hou, J., Lu, X., Kang, J., 2003. Plasma Degradation of Dyes in
Water with Contact Glow Discharge Electrolysis. Water Research, Volume
37(2), pp. 267–272
Gupta, S.K.,
2015. Contact Glow Discharge Electrolysis: Its Origin, Plasma Diagnostics and
Non-faradaic Chemical Effects. Plasma
Sources Science and Technology, Volume 24(6), pp. 1–24
Haron, R., Yun,
H.A.H., Mat, R., Mohammed, M, 2017. Overview of Biodiesel Wastes Utilization
for Hydrogen Production. Chemical
Engineering Transactions, Volume 56, pp. 391–396
Istadi, I., Yudhistira,
A.D., Anggoro, D.D., Buchori, L., 2014. Electro-Catalysis System for Biodiesel
Synthesis from Palm Oil over Dielectric–Barrier Discharge Plasma Reactor. Bulletin of Chemical Reaction Engineering and Catalysis, Volume 9(2), pp. 111–120
Jin, X., Wang,
X., Yue, J., Cai, Y., Zhang, H., 2010. The Effect of Electrolyte Constituents
on Contact Glow Discharge Electrolysis. Electrochimica Acta, Volume
56(2), pp. 925–928
Kozáková, Z.,
2011. Electric Discharges in Water
Solutions. Brno, Czech Republic: Brno University of Technology, 12
Lee, D.W., Park,
Y.M., Lee, K.Y., 2009. Heterogeneous Base Catalysts for Transesterification in
Biodiesel Synthesis. Catalysis Surveys
from Asia, Volume 13(2), pp. 63–77
Lotero, E., Liu,
Y., Lopez, D.E., Suwannakarn, K., Bruce, D.A., Goodwin, J.G., 2005. Synthesis
of Biodiesel via Acid Catalysis. Industrial
& Engineering Chemistry Research, Volume 44(14), pp. 5353–5363
Saito, G., Nakasugi, Y., Akiyama, T., 2015. Generation of Solution Plasma
Over a Large Electrode Surface Area. Journal of Applied Physics, Volume
118(2), 023303
Saksono. N, Siswosoebrotho, D.A., Pranata. J, Bismo, S., 2018. Synthesis
of Biodiesel from Crude Palm Oil by using Contact Glow Discharge Electrolysis. IOP Conf. Series: Materials Science and
Engineering, Volume 316, 012024
Saksono, N., Kartohardjono, S., Yuniawati, T., 2016. High Performance
Plasma Electrolysis Reactor for Hydrogen Generation using a NaOH-Methanol
Solution. International Journal of
Technology, Volume 7(8), pp. 952–960
Saksono,
N., Seratri, T.R., Muthia, R., Bismo, S., 2015. Phenol Degradation in
Wastewater with a Contact Glow Discharge Electrolysis Reactor using a Sodium
Sulfate. International Journal of
Technology, Volume 6(7), pp. 1153–1163
Sengupta,
S., Srivastava, K.A.K., Singh, R., 1997. Contact Glow Discharge Electrolysis: A
Study on its Origin in the Light of the Theory of Hydrodynamic Instabilities in
Local Solvent Vaporization by Joule Heating During Electrolysis. Journal of Electroanalytical Chemistry,
Volume 427(1), pp. 23–27
Zong, C.Y., Chen,
L., Wang, H.L., 2009. Hydrogen Generation by Glow Discharge Plasma Electrolysis
of Methanol Solutions. International
Journal of Hydrogen Energy, Volume 34(1), pp. 48-55