ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY &
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AZOJETE December 2020. Vol. 16(4):717-724
Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria.

Print ISSN: 1596-2490, Electronic ISSN: 2545-5818
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Corresponding author’s e-mail address: slmnyunus@gmail.com 717

ORIGINAL RESEARCH ARTICLE

CHARACTERIZATION OF SYNTHESIZED ZEOLITE SOCONY MOBILE 5
(ZSM-5) FROM BULARAFA DIATOMITE

S. Yunusa*, A. S. Ahmed, M. Yusuf, M. Abubakar and S. G. Bawa
Department of Chemical Engineering, Ahmadu Bello University, Zaria, 810261, Nigeria

*Corresponding author’s email address: slmnyunus@gmail.com

1.0 Introduction
Diatomite rock is a loose, earthy or loosely cemented porous and lightweight rock of
sedimentary origin, mainly formed by fragments of armor (skeletons) of diatom algae:
(diatomea and radiolaria). Diatomite is a microscopic diatom alga whose size ranges from 0.75
to 1500 m; sometimes this rock is called infusorial earth, kieselguhr, or mountain meal (Arik,
2003). The important properties of diatomite are related to physical structures and an
aggregate of fine particles perforated by a regular pattern of very small holes (Aliev et al., 2011).
Diatomite’s highly porous structure, low density and high surface area resulted in a number of
industrial applications as filtration media for various beverages and inorganic and organic
chemicals as well as an adsorbent for oil spills (Bakr, 2010). It can be used as an alternative
source of amorphous silica for the production of silicon-based materials with industrial and
technological interests. Diatomite is another interesting material because of its low cost and its
advantage over other materials such as clays, iron oxides, molecular sieves, activated carbon
and rice husk due to the highly reactive amorphous state of its silica skeletons, which makes it
unnecessary to carry out thermal activation to transform an unreactive state into a reactive
state (Chaisena and Rangsriwatananon, 2005). It has been shown that kaolin clay and
diatomaceous earth are two suitable and inexpensive sources of silica materials. Some studies
reported that rice husk ash contains high amount of silica that is amorphous or crystalline
depending on the combustion temperature (Shen et al., 2011, 2018; Habeeb and Mahmud,
2010). Other studies were conducted on the synthesis of zeolites from rice husk ash, namely
MCM zeolite and ZSM-5 (Chiarakorn et al., 2007; Fernandes et al., 2005; Mohammed et al.,
2008) for possible use in catalytic refinery and petrochemical processes. However, preparation
of zeolites with higher SiO2/Al2O3 molar ratios such as ZSM-5 requires either an increase of
the amount of silica or partial removal of aluminium. The first alternative implies using an
additional source of silica with high solubility, e.g. sodium silicate or silica sol as reported in the
research works of Khatamian and Irani 2009, Kovo et al., 2009. However, in the work of Li et
al., 2015, ZSM-5 zeolite was synthesized directly from diatomite after calcination, but the
synthesized zeolite has low quality which could be due to the presence of impurities such as

ARTICLE
INFORMATION

ABSTRACT
In this study, a highly siliceous ZSM-5 zeolite with elemental silicon to
aluminium ratio of 250 was synthesized using Bularafa diatomite as silica
source. The diatomite was used to produce silica sol which was used with
alumina in the presence of organic template (tetrapropyl ammonium bromide,
TPABr) to form ZSM-5 under hydrothermal reaction at low temperature and
atmospheric pressure in alkaline medium. The synthesized ZSM-5 was
characterized using X-ray diffraction (XRD), Fourier transformation infrared
spectroscopy (FT-IR), scanning electron microscopy (SEM), N2 adsorption and
X-ray fluorescence (XRF). The Brunauer, Emmet and Teller (BET) method
revealed that the ZSM-5 produced from Bularafa diatomite have very high
specific surface area of 619 m2 g–1.

© 2020 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved.

Submitted 20 Sept., 2019
Revised 3 July, 2020
Accepted 18 July, 2020.

Keywords:
Diatomite
ZSM-5 zeolite
Synthesis
low temperature
siliceous.

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Yunusa et al.: Characterization of Synthesized Zeolite Socony Mobile 5 (ZSM-5) from Bularafa Diatomite. AZOJETE,16(4):717-724. ISSN
1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: slmnyunus@gmail.com 718

iron oxide, potassium etc. Also, in the previous works ZSM-5 took longer synthesis times up to
seven days and above at elevated temperature.

In this study, we synthesized a highly siliceous ZSM-5 by using silica sol prepared from Bularafa
diatomite for the first time.

2.0 Materials and methods
2.1 Materials
Bularafa diatomite as a silica source was collected in lump from Bularafa village in Gubja Local
Government area of Yobe State. Activated alumina (fused 99%, Sigma, USA), pellets of sodium
hydroxide (98 wt.%, Sigma, USA), tetrapropyl ammonium bromide (TPABr) (Sigma, USA),
Sulphuric acid (98 wt.%, Sigma, USA) and distilled water were used as the starting materials in
the initial mixture for the synthesis of ZSM-5.

2.2 Methods
The Bularafa diatomite was characterized using Empyreal PANalytic Diffractometer X‟pert 3
with Cu Kα radiation (PHILIPS BW 1710, Netherlands) for XRD and Munipal 4 Energy
Dispersed- X ray fluorescence (ED-XRF, USA) machines and gas adsorption measurement with
N2 (BET isothermal).

The diatomite was treated with 1M hydrochloric acid (Merck) to remove impurities such as
iron and calcium before sodium silicate extraction. Sodium silicate was extracted from acid
treated diatomite following the methods of Panda et al., (2004), Mandal and Benergee, (2004)
and Anjum et al., (2010). Sodium silicate obtained was used in silica sol production via
neutralization of alkaline sodium silicate solution with sulfuric acid (Malewski et al., 2006; De
sousa1 et al., 2009) and Kalaphaty et al., (2000).

2.2.1 Synthesis of ZSM-5 from silica sol
ZSM-5 was prepared according to hydrothermal procedure as reported previously (Lisensky et
al., 2008). 1.2g of sodium hydroxide in 7.5ml of de-ionized water, 0.09g of an activated alumina
was added with additional 0.1g of NaOH pellets and mixture was stirred. Then 1.2g tetrapropyl
ammonium bormide was added to 0.51 ml of 96 wt. % of 1 M H2SO4 and mixture stirred. The
mixtures were simultaneously added to 25ml of silica sol prepared from kaolin in a
polypropylene bottle and the mixture shaken vigorously for 5 minutes, and then the mixture
was stirred vigorously for 30 minutes and then tightly closed. It was then aged in an oven at
95°C for 4 days. After 4 days, the polypropylene bottle was removed and the cap was opened
and the liquid was carefully decanted manually. The solution was filtered using a filter paper,
and the white solid was washed with de-ionized water several times until the pH is about 8.
The solid product was dried in an oven at 100°C for 12hrs. The dried sample was calcined at
500°C for 2 hours using a Gallen kamp 6B77A tube furnace in the presence of nitrogen.

2.3 Zeolite Characterization
The calcined sample was analyzed using the following equipment, Empyreal PANalytic
Diffractometer (XRD), using Cu Kα radiation, X-ray fluorescence (XRF) by a Munipal 4 Energy
Dispersed- X ray fluorescence (ED-XRF), Phenom ProX desktop (34250) SEM, USA, and
Shimadzu 8400S spectrometer (FTIR), Japan. In addition, the specific surface areas of sample
were measured by the Brunauer, Emmet and Teller (BET) method using nitrogen adsorption–
adsorption data were recorded with a Quantachrome (Novawin-Data Acquisition and
Reduction Version 11.03) 2013 equipment, USA.

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Arid Zone Journal of Engineering, Technology and Environment, December, 2020; Vol. 16(4):717-724. ISSN 1596-2490; e-ISSN 2545-
5818; www.azojete.com.ng

Corresponding author’s e-mail address: slmnyunus@gmail.com 719

3.0 Results and Discussion
3.1 XRD Analysis of zeolite
The XRD patterns of Buralafa diatomite, diatomite based ZSM-5 and referenced ZSM-5 are
shown in (Figure 1) as illustrated in Figure 1a, the XRD pattern of diatomite has a diffraction
peak at 2ϴ of 26.7 with small amount of quartz and broad band of 2ϴ = 22-30° corresponding
to amorphous silica as reported by Li et al., 2015 and Yi et al., 2006 respectively. This confirms
that diatomite was amorphous originally. When Figure 1(a) was compared to the XRD pattern
of the synthesized ZSM-5 in Figure 1(b) a distinct peak at 2ϴ of 7.88, 23.23, 8.8, 23.63, 23.85
and 24.33˚ ascribing to ZSM-5 were observed. It can be seen that Figure 1 (b) compared well
with XRD pattern reported by Treacy and Higgins, 2001 in Figure 1 (c), since all the
characteristic peaks of ZSM-5 were observed in Figure 1 (b) and no other unknown phase in
the XRD patterns, this indicated that the synthesized powders were pure ZSM-5 zeolite
crystals.

Figure 1: XRD pattern of (a) Diatomite (b) diatomite based ZSM-5 and (c) Reference ZSM-5

3.2 Fourier Transform Infra- Red (FTIR) Analysis
FTIR could help us understand the active sites and subsequently the mechanisms involved in
zeolite catalysis. We know that the lattice vibrations characteristic to H-ZSM-5 zeolite usually
appear in the range of 400–1200 cm−1, while the bands corresponding to OH bond vibrations
appear at wave numbers higher than 3200 cm−1 (Shaik et al., 2015). Figure 2 presents the FT-IR
spectra recorded in the 4000–400 cm-1 range for diatomite based synthesized ZSM-5. The IR
spectra of ZSM-5 zeolite showed general spectral features at 1221, 1092, 795, 548 and 448cm-1

which were assigned to different vibrations of tetrahedral and framework atoms in ZSM-5
zeolite (Ibraheem et al., 2012). The bands at about 1090 and 456 cm-1 are due to internal
vibrations of (Si, Al)O4 tetrahedra of ZSM-5, which are insensitive to framework structure. The
other bands at about 1234, 800 and 557 cm-1 are due to vibrations related to external linkages
between tetrahedra and hence sensitive to framework structure. The presence of infrared band
around 557.45cm-1 for diatomite based ZSM-5 indicated the characteristic vibrational modes of
the ZSM-5 zeolite framework. According to (Shaik et al., 2015) the spectral bands appearing at
3450 and 3700 cm−1 in Figure 2 may be attributed to the presence of hydroxyl groups in this
ZSM-5 (Lercher et al., 1999), which may be responsible for catalyzing cracking (Bhan et al.,
2008; Kotrel et al., 2000). The evidence for the formation of ZSM-5 zeolite could be seen in
Figure 2 from the appearance of the bands at 557.45 and 1234.40 cm-1.

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Yunusa et al.: Characterization of Synthesized Zeolite Socony Mobile 5 (ZSM-5) from Bularafa Diatomite. AZOJETE,16(4):717-724. ISSN
1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: slmnyunus@gmail.com 720

Figure 2: FTIR spectra for Bularafa diatomite based ZSM-5

3.3 Scanning Electron Micrograph (SEM) Analysis
The SEM technique was used to observe the crystals as shown in Figures 3 (a), (b) and (c). It
was observed that the sample was ellipsoidal in shape. The sizes of these samples were
uniformly distributed and did not contain amorphous substances or other crystalline impurities
as can be seen in the SEM image of raw diatomite in Figure 3a; (Chaisena and Rangsriwatananon,
2005). The uniformity in morphology of the synthesized ZSM-5 suggested that good
crystallization was obtained, as shown in the XRD pattern 1b. From the high-resolution SEM
micrographs (Figure 3c), it was observed that the surface of the large particle was composed of
many small crystals. These small primary crystals appeared to be tightly packed together to
form the polycrystalline particles.

Figure 3: SEM images for (a) raw diatomite, (b) ZSM-5 from diatomite at low magnification (c)
ZSM-5 from diatomite at high magnification.

3.4 X-Ray Fluorescence (XRF) Analysis
Chemical compositions of raw Buralafa diatomite and diatomite based synthesized ZSM-5 were
determined using XRF technique as shown in Table 1. It could be observed that ZSM-5
synthesized from diatomite contained small impurities, this may be due to the acid treatment of
the raw diatomite and preparation silica sol from the diatomite used, which greatly minimized

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Arid Zone Journal of Engineering, Technology and Environment, December, 2020; Vol. 16(4):717-724. ISSN 1596-2490; e-ISSN 2545-
5818; www.azojete.com.ng

Corresponding author’s e-mail address: slmnyunus@gmail.com 721

metal oxides contents such as Fe2O3, CaO, MgO and CuO. These oxides could also cause a
decrease in BET surface area as observed in Li et al., 2015 who recorded a low BET surface
area of 223 m2 g-1 as compared to 619 m2 g-1 obtained in this work. The impurities reduce the
surface area of the synthesized zeolite by filling up some of its pores. Si to Al ratio was another
very important parameter that could be used to measure the catalytic activity of the zeolite and
it was determined by the XRF analysis as shown in Table 1. It could be seen that Si to Al ratio
of diatomite based ZSM-5 was 250. Generally, Si to Al ratio of a zeolite determine its chemical
and thermal stability, the literature value of Si to Al ratio of ZSM-5 zeolite is from 10 to 500
(Al-Bogami, 2013).

Table 1: Chemical analysis (XRF) of Raw Diatomite and ZSM-5 from Diatomite
Oxides Raw Diatomite (wt.%) ZSM-5 from Diatomite (wt.%)
SiO2 89.30 99.20
Al2O3 0.62 0.35
CaO 0.53 0.261
TiO2 0.86 0.010
MnO 0.007 0.006
Fe2O3 5.73 0.095
CuO 0.063 0.023
K2O 0.46 -
LOI 1.03 -
Si/Al 250

3.5 Surface Analysis of ZSM-5
Nitrogen adsorption-desorption data were recorded with a Quantachrome (Novawin-Data
Acquisition and Reduction Version 11.03) 2013 equipment to determine the BET specific
surface area (SSA), micro pore size and micro-pore volume of the synthesized ZSM-5. The N2

adsorption isotherm of ZSM-5 synthesized from Buralafa diatomite is shown in Figure 4. It was
type I based on IUPAC’s classification with a large nitrogen uptake at low pressure and the
desorption matched with the adsorption isotherms. Also, the knee portion of the isotherm was
higher indicating its higher surface area, as shown in Table 2.

The specific surface area (SSA) of the synthesized ZSM-5 was determined using the BET
techniques, while the micro-pore volume and pore diameter were determined using Horvath-
Kawazoe (H-K) and Sato Foley (SF) methods. The BET SSA obtained in this work for the
sample prepared from Bularafa diatomite was 619 m2/g which is two times more than that
obtained in the study by Aguilar -mamani et al., 2014 (298 m2/g), who employed leached
diatomaceous earth directly as silica source. Also, Li et al synthesized ZSM-5 using purified
diatomite and sodium aluminate as silica and alumina sources respectively, where BET surface
area of 223 m2/g was obtained as shown in Table 2. Both micro-volume and pore sizes of the
synthesized ZSM-5 were quite comparable with the ones got in the previous works of Aguilar -
mamani et al. (2014), Li et al. (2015) and Al-bogami (2013) as indicated in Table 2.

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Yunusa et al.: Characterization of Synthesized Zeolite Socony Mobile 5 (ZSM-5) from Bularafa Diatomite. AZOJETE,16(4):717-724. ISSN
1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: slmnyunus@gmail.com 722

Table 2: Texture properties of synthesized ZSM-5 from Diatomite using different methods

a Data are determined by applying the Saito-Foley method
b Data are determined by applying the Horvath-Kawazoe method
c Data are determined by applying the t-plot method

Figure. 4: N2 Adsorption‐desorption Isotherms of the Synthesized ZSM-5 from Buralafa
Diatomite

4.0 Conclusions
The ZSM-5 was successfully synthesized from Bularafa diatomite via the hydrothermal process.
The utilization of diatomite as inexpensive raw material for ZSM-5 zeolite synthesis is
remarkable. From the XRD result, it was observed that well crystalline ZSM-5 was successfully
synthesized from diatomite without using additional silica source. SEM images of the ZSM-5
also confirmed uniform particles distribution. In addition, FTIR analysis showed that the ZSM-5
were pentacyclic with typical absorption band at about 550 cm-1. The BET method revealed
that the ZSM-5 produced from Bularafa diatomite have very high specific surface area that is
suitable for zeolite application. Also, the ZSM-5 had least metal oxide impurities due to the acid
treatment carried out on the Buralafa diatomite which has greatly reduced the metal oxides.

Samples BET Surface area Median pore Micro pore Reference
(m2g-1) Diameter (nm) volume (cm3g-1)

As- synthesized
ZSM-5 from Bularafa
Diatomite 619 0.45a 0.013a This work

As- synthesized
H- ZSM-5
from Kaolin 411 0.61b 0.12c Al-bogami, 2013

As- synthesized
ZSM-5 from Diatomite 223 0.54 0.06 Li et al., 2015

As- synthesized
ZSM-5 from Bolivian
Diatomite 298 - 0.15 Aguilar-Mamani et al., 2014

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Arid Zone Journal of Engineering, Technology and Environment, December, 2020; Vol. 16(4):717-724. ISSN 1596-2490; e-ISSN 2545-
5818; www.azojete.com.ng

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Acknowledgments
The authors gratefully acknowledge the Petroleum Technology Development Fund (PTDF),
Abuja-Nigeria, for supporting this research work.

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Yunusa et al.: Characterization of Synthesized Zeolite Socony Mobile 5 (ZSM-5) from Bularafa Diatomite. AZOJETE,16(4):717-724. ISSN
1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

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