Biodiesel Synthesis from Rubber Seed Oil via Esterification using

H-Zeolit and Zro

/ZAK Catalysts

Rahayu, Tiamina Nasution, Yunita Sari Lubis, Anggi Al Ridha Lubis, Agus Kembaren,

Rini Selly and Ahmad Nasir Pulungan

Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Negeri Medan, Medan, Indonesia

Keywords: Biodiesel, Rubber Seed Oil, Zeolite, Heterogenous Catalysts

Abstract: Rubber seed oil is a non-edible oil that is very potential as a biodiesel feedstock. The synthesis of biodiesel

from rubber seed oil was done by reaction of esterification free fatty acid (FFAs) and transesterification of

Triglycerides (TGs) in a single step, which used heterogeneous catalysts. Zeolite is one type of catalyst that

has been developed for this process. In this study the catalyst was prepared using Indonesian natural zeolite

(ZAK). To increase catalytic activity, zeolite catalyst was loaded with zirconium (Zr) by wet impregnation

method, followed by the process of calcination and oxidation at a temperature of 400

C for 1 hours with gas

flow of O

and N

. ZAK and ZrO

/ZAK catalysts were characterized by XRD and SEM-EDS. The catalyst

produced has good crystallinity as seen from sharp peaks with high intensity and high levels of Si. The

catalyst activity test was done in the process of converting rubber seed oil into biodiesel. The reaction

process was carried out at a temperature of 100

C with a variety of catalyst concentrations: oil1: 2, 1: 4, and

1: 6 and the reaction time varied by 30, 60, and 90 minutes. The most optimum process of biodiesel

produced at the ratio of catalyst 1 : 2 with reaction time of 30 minutes showed the biodiesel yield of

67,95%. Biodiesel products were tested for water content, FFA, and density of each is 0,09%, 2,15%, dan

0,89 g/cm

. GC analysis shows that the main composition of biodiesel consists of diesel fraction (C

-C

)

with the most components being methyl linoleic 38,82% and methyl oleat 22,33%.

1 INTRODUCTION

Biodiesel is a renewable alternative fuel produced

from vegetable oils or animal fats. Vegetable and

animal oils are alternative energy sources that are

new, renewable and environmentally friendly in

addition to the fuels produced are also

biodegradeable and almost contain no sulfur and are

environmentally friendly (Jaya et al., 2011).

Vegetable oils developed in Indonesia are

sourced from palm oil, and jatropha oil, the current

research has reached the utilization of palm oil and

castor oil to substitute diesel fuel, but these materials

have limitations, palm oil is edible oils with high

selling value. According to Fukuda et al. (2001) and

Tyson (2004), edible oils as biodiesel feedstock

affect 60% -70% of biodiesel prices. Therefore, it is

open to find alternative energy sources from

vegetable oils with non-edible oil with abundant

availability and lower prices.

One source of vegetable oil that can be

developed is oil from rubber seeds. So far rubber

seeds have not been widely used and disposed of as

plantation waste. Meanwhile rubber seeds contain

about 40-50% of vegetable oil which is very

potential to be developed as raw material for

biodiesel synthesis (Setyawardhani et al, 2010). The

synthesis of biodiesel from rubber seed oil can be

done by an esterification reaction, where fatty acids

in rubber seeds will be reacted with short chain

alcohols resulting in fatty acid methyl esters. This

reaction is slow, so a catalyst is needed to reduce

activation energy and accelerate the reaction. This

reaction generally uses alkaline catalysts NaOH and

KOH.

However, rubber seed oil has a high content of

Free Fatty Acid (> 5%), the uses of alkaline catalysts

can cause saponification side reactions which can

reduce the rate of formation of biodiesel products.

Because it is currently being developed for this

process by using heterogeneous catalysts.

Rahayu, ., Nasution, T., Sari Lubis, Y., Al Ridha Lubis, A., Kembaren, A., Selly, R. and Pulungan, A.

Biodiesel Synthesis from Rubber Seed Oil Via Esteriﬁcation using H-Zeolit and ZrO2/ZAK Catalysts.

DOI: 10.5220/0009873600002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 5-10

ISBN: 978-989-758-556-2

The advantages of heterogeneous acid catalysts

are because they are less corrosive, do not need

expensive separation processes, and can reduce the

impact of environmental pollution (Leung et al.,

2009). One type of heterogeneous acidic material is

zeolite. The ability of zeolite as a catalyst is related

to the availability of active centers of Bronsted acid

sites and Lewis acid sites found in the channels

between zeolite (Sihombing et al., 2018; Sriningsih

et al., 2014; Pulungan, 2010). Modification of

zeolite has been carried out by impregnating metals

in carrier materials with the aim of prolonging the

life of the catalyst, having good thermal stability and

large surface area.

According to Sriatun and Suhartana (2002) the

metal which is applied to zeolite solids through

impregnation will make the metal in the zeolite as a

bifunctional catalyst. Heterogeneous catalysts that

are currently being developed for the production of

biodiesel are zeolite which is combined with metal

oxides such as ZrO2, SnO2. In addition, PbO and

ZnO metal oxides were also developed as catalysts

that are applied to zeolite. Singh et al., 2014 reported

that PbO / zeolite showed better activity than

ZnO/zeolite catalyst in the process of converting

sunflower oil with high free fatty acid content (>

10%). Meanwhile, Sukmawati (2016) has made

biodiesel from used cooking oil using sulfated

zirconia zeolite catalyst through a transesterification

reaction. From the results of this study, the

conversion of triglycerides was 71.63% at the

optimum condition of the reaction time for 120

minutes.

Therefore, in this study biodiesel synthesis from

rubber seed oil was carried out using active natural

zeolite catalyst which was treated with metal

Zirconium oxide (ZrO2 / ZAK). The uses of ZrO2 /

ZAK catalysts are expected to increase biodiesel

products and produce a cheaper and environmentally

friendly conversion process. In this study will be

studied the effect of catalyst concentration and

reaction time to obtain optimum catalyst activity.

2 MATERIALS AND METHOD

2.1 Tools

The tools used were a set of glass tools, reflux tools,

sokhlet tools, analytic balance, rotary evaporator,

buchner funnel, hotplate, thermometer, furnace,

magnetic stirrer, 100 mesh filter, porcelain cup,

oven, XRD, SEM-EDS, and GC.

The materials used were aquades, aquabides,

rubber seeds oil, commercial natural zeolites

(Bratachem), HCl (Merck pa), ZrCl

(Merck pa),

nitrogen gas, NaOH (Merck pa), H2SO4 (Merck pa),

PP indicators, AgNO

( Merck pa), H

(Merck

pa), n-Hexane (technical), and CH

OH (Merck pa).

2.2 Preparation of Rubber Seed Oil

The rubber seeds were separated from the shell, then

the rubber seeds dried under the sun for 2-3 days

after that mashed using a blender. The refined rubber

seeds then extracted to obtain the oil with n-hexane

solvents at 60°C for 2 hours (5 cycles) continued

with separated the solvent using a rotary evaporator

to produce pure rubber seed oil, then analyzed to

determine the levels of free fatty acids (FFA ),

density and water content.

2.3 Preparation of Natural Zeolite

Natural zeolite was smoothed and filtered with a 100

mesh filter. Then washed with distilled water for 24

hours at room temperature. Zeolite filltered and the

precipitate dried at 100°C. The natural zeolite

sample was dehumuminated with 3M HCl and then

refluxed at 90°C for 30 minutes. The reflux solution

was filtered and the resulting sediment was washed

with distilled water until the pH of the washing

water was neutral. The precipitate was then dried at

120° C for 3 hours, then calcined at 400°C for 1

hour with gas nitrogen flow (± 20 mL / minute) to

obtain acid-activated natural zeolite (H-Zeolite)

(Sihombing et al. , 2018).

2.4 Preparation of ZrO2/ZAK Catalyst

An amount of 1% ZrCl

(% w Zr) was dissolved

with aquabides in a round bottom flask and then

added to ZAK, the mixture stirred for 3 hours at 80°

C after that zeolite was dried. Zeolite was then

oxidized with O2 gas at 400°C for 1 hour. The ZrO2

/ ZAK catalyst produced was characterized by FTIR

spectrometers Shimadzhu type 8201-FC, X-ray

difractometer Shimadzu 6100 using Cu Kα radiation

at 40 Kv and 30 mA with scanning rate of 2o min-1

in range 2θ 7

– 70

, SEM and SEM-EDS used Zeis

type EPOMH 10 Zss.

2.5 Synthesis of Biodiesel

Biodiesel made by mixing 99% methanol and zeolite

as a catalyst in a base flask with a ratio of zeolite: oil

that is 1: 2, 1: 4, and 1: 6 (v/v). The mixture then

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

added to rubber seed oil with a ratio of oil: methanol

1: 6 (v/v) and stirred at a speed of 600 rpm for 30,

60, and 90 minutes at 65°C at a pressure of 1 atm.

The mixture continued by filtered with a Buchner

funnel. Then decanted for 2 days. The biodiesel

produced was analyzed for FFA content, water

content, density, and GC characterization.

3 RESULTS AND DISCUSSION

3.1 Characterization of Natural

Zeolites

FTIR analysis was used to determine the functional

groups of zeolite samples. Based on the ZAK spectra

in figure 1 it can be seen that the TO

group

absorption characteristic of zeolite observed at

1089.98 cm-1. The absorption band of Si-O / Al-O

group at 723.92 cm

-1

and 794.95 cm

-1

. Hamdan

(1999) reported that in the 900-1250 cm

-1

band was

an asymmetrical range of the TO4 group, internal Si-

O / Al-O (TO) bending appeared in the 420-500 cm-

1 region while for the external would appear at 700-

780 cm

-1

(Hamdan, 1992). Sihombing et al (2018)

reported that asymmetrical range vibrations of the

TO4 zeolite group were in the range of1000-1100

-1

. Asymmetric vibration absorption of the TO4

group from Sarulla zeolite was at 1042.16 cm

-1

(Nasution et al., 2019).

Figure 1: FTIR spectrum of commercial natural zeolite

Measurements with X-ray diffraction were

carried out to identify the crystallinity of the initial

natural zeolite, natural zeolite after acid activation

and after ZrO

was introduced. The results of XRD

analysis of each sample are presented in Figure 2.

Sharp peaks with high intensity show good

crystallinity. Figure 2 shows that the treatment of

HCl 3M (H-zeolite) activation provides an increase

in intensity on some of the main zeolite peaks at 20-

30 2 theta degrees. This is due to the loss of

amorphous and crystalline impurities that cover the

zeolite pores (Waluto et al., 2017; Sihombing et al.,

2018). In this figure ZrO

/ZAK also shows the

increasing intensity of the main zeolite peak. This

shows that the impregnation of ZrO

metal is

distributed evenly on the surface and pore of zeolite.

While the oxidation process at a high temperature of

500

C results in the loss of organic and inorganic

impurities in zeolite pores.

Based on table 1 Typical peaks of zeolite are seen

in H-Zeolite and ZrO

/ZAK at position 2 theta

degrees which are almost the same although with

slightly different intensities. This shows that acid

treatment is dealumination with 3M HCl in H-Zeolite

and thermal treatment ie oxidation on ZrO

/ ZAK

does not damage the structure of zeolite even though

there is a decrease in peak intensity of ZrO

ZAK. The decrease in peak intensity in metal-borne

natural zeolites proves that metals have been on the

surface of natural zeolites (Rianto et al., 2012).

Figure 2: Diffactogram comparison of ZAK, H-Zeolite

and ZrO

/ZAK

Table 1: The main peak intensity of ZAK, H-Zeolite and

ZrO

/ZAK

Catalyst 2𝜃

(°)

Intensity

(counts)

ZAK

9.87 364.90

22.54 548.03

35.74 142.15

H-Zeolite

10.04 304.2

21.99 623.52

35.87 142.01

ZrO

/ ZAK

9.03 302.21

27.7 527.17

35.53 256.24

Biodiesel Synthesis from Rubber Seed Oil Via Esteriﬁcation using H-Zeolit and ZrO2/ZAK Catalysts

The SEM data showed information on surface

topology and metal dispersion that is applied to

zeolite, while from EDS data of chemical

composition is obtained on the surface of the

sample. Figure 3a and 3b describe surface topologies

of H-zeolite and ZrO2 / ZAK with a magnification

of 1000 times. In figure 3a the surface micrograph of

H-zeolite shows a surface structure consisting of

lamellar with a small size that is uneven and there

are still lumps. While ZrO2 / ZAK in figure 3b

shows a smooth and more homogeneous surface

structure. This data supports XRD data which shows

the metal dispersing process does not occur

sintering. Metal oxides are distributed evenly in

zeolite pores.

Figure 3: Surface topology enlarged 1000×. (a) natural

zeolite, (b) ZrO

/ZAK

Figure 4: Graph of chemical composition in (a) H-Zeolite,

(b) ZrO

/ZAK

3.2 Synthesis of Biodiesel from Rubber

Seed Oil

Rubber seed oil is obtained by soxhlet extraction

method using technical n-hexane solvents. The yield

of rubber seed oil obtained was 43.79%.

Characteristics of rubber seed oil based on practice

and standards are presented in table 2. Rubber seed

oil is obtained by soxhlet extraction method using

technical n-hexane solvents. The yield of rubber

seed oil obtained was 43.79%. Characteristics of

rubber seed oil based on practice and standards are

presented in Table 2.

Table 2: Characteristics of rubber seed oil (RSO) and

biodiesel

Characteristics

ASTM

D6751

(

biodiesel

)

RSO

Bio

Diesel

Water content

(

)

0.05 1.101 0.09

FFA (%) < 2 10.401 2.15

Density (g/cm

) 0.860-0.900 0.9097 0.89

The process of converting rubber seed oil with

ZAK and ZrO2 / ZAK catalysts is carried out by a

one-step process. In this reaction, esterification of

free fatty acids and transesterification of

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

triglycerides occur the same process. The results of

the conversion of biodiesel products obtained are

presented in table 2. The optimum process

conditions were obtained at a catalyst ratio: 1: 2 and

a temperature of 30

C with a 67.95% biodiesel yield

value. To see the effect of variations in the catalyst

ratio: oil and process temperature, data made in

graphical form as shown in Figures 5 and 6. The

ratio of the catalyst: oil and reaction time affects the

conversion value of the biodiesel.

Figure 5: Graph of the relationship of reaction time to

biodiesel yield

In Figure 5, it can be seen that the most optimum

of reaction time which produces the highest yield is

30 minutes. In general, the longer the esterification

reaction time, the greater the conversion of oil to

biodiesel because of the greater the chance of

collisions between molecules occur. But at the

reaction time for 60 minutes and 90 minutes there

was a decrease in the yield of biodiesel produced,

this is because the reaction temperature used is close

to the boiling point of methanol (65

C) causing

some of the methanol to evaporate as the reaction

time increases. This resulted in a reduced molar ratio

of methanol to esterification oil. Tiamina et al.

(2019) reported that evaporation of methanol

resulted in a reduced molar ratio of methanol to

biodiesel production so that the yield of biodiesel

produced decreased.

Figure 6 shows that biodiesel yield increases

with increasing of catalyst:oil ratio. The increasing

of the concentration of the catalyst will reduce the

activation energy for the esterification reaction

thereby increasing the number of molecules

activated and reacting to form the fatty acid methyl

ester. At a reaction time of 30 minutes, a larger

catalyst: oil ratio shows a sharp increase in the

conversion of biodiesel products. Different trends

are shown at reaction times 60 and 90 minutes,

where the catalyst ratio increases: oil shows a

decrease in the conversion of biodiesel products and

shows an increase in a larger ratio. It can be

understood that at ratio: catalyst 1: 2 it is possible to

meet the active side of the catalyst with reactants

greater compared with the ratio of 1: 6. So that the

chance for contact between the reactants and the

catalyst to be greater so that it will produce a

catalyzed reaction that is also getting bigger. This is

indicated by the increasing conversion of biodiesel

products produced.

Figure 6: Graph of the relationship of ratio of rubber seed

oil to zeolite with the biodiesel yield

Figure 7: GC chromatogram of biodiesel product at

optimum condition.

Table 3: Chemical component of biodiesel

No. Component Methyl ester

Composition

(%)

1. C16 Methylpalmitate 9.80

2. C18 Methylstearate 8.85

3. C18 : 1 Methyloleate 22.33

4. C18 : 2 Methyllinoleic 38.82

5. C18 : 3 Methyllinolenic 18.22

6. C20 Methylarachidat 0.33

Figure 6 shows the chromatogram of biodiesel

products obtained at optimum conditions, with the

main content are methyl linoleic and methyl oleate

with a percentage of 38.82% and 22.33%

respectively.

Biodiesel Synthesis from Rubber Seed Oil Via Esteriﬁcation using H-Zeolit and ZrO2/ZAK Catalysts

4 CONCLUSION

The acid activation process increases zeolite

crystallinity. The impregnated of zirconium oxide

(ZrO2) causes a shift and decreases the ripple

intensity of zeolite, but does not damage the zeolite

crystal structure. In the process of converting

biodiesel from rubber seed oil the optimum yield

was 67.95% at a catalyst ratio of 1: 2 with a reaction

time of 30 minutes. The main composition of

biodiesel consists of C16-C20 diesel fraction with

the most components, namely methyl linoleic (C18:

2) as much as 38.82% and methyl oleate (C18: 1) as

much as 22.33%.

ACKNOWLEDGEMENT

We would like to thanks Agency of the Ministry of

Research, Technology and Higher Education of the

Republic of Indonesia (KEMENRISTEKDIKTI)

which has funded our research via the Student

Creativity Program-Research (PKM-P) 2019.

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IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)