Dry Reforming of Methane: Its Catalytic Problems and a New Suggested Study
Prepared by: 191142401 – Mohamad Samer KANSOU
To: Assoc. Prof. Dr. Hüseyin ARBAĞ
A project report submitted in fulfilment of the requirements for the course of
CHE491 – Graduation Project
Gazi University
Faculty of Engineering
Department of Chemical Engineering
Submission Date:
6th Jan 2023
Abstract
A research study that will suggest a new catalyst to synthesize for dry reforming of methane
reaction (a chemical process that involves the transformation of methane and carbon dioxide
into synthesis gas, a combination of hydrogen and carbon monoxide) in fulfilment of
graduation project requirements have been performed. This reaction has gained interest due
to its potential for creating hydrogen for use in fuel cells and as a raw material for the
manufacture of chemicals and materials. One of the main issues with dry reforming is the
high temperature necessary for the reaction to occur, the coke deposition on the catalyst, and
catalyst sintering which can damage catalysts and lead to catalyst deactivation. In order to
have an encapsulated study, this project first discusses what are porous materials and their
classification, the characterization techniques that can mainly used in methane dry reforming,
and a literature survey covering the recent progresses in dry reforming of methane catalysis.
Finally, a new study was suggested to design a plasma decomposed nickel-based catalyst on
three different supports and promotors using microemulsion, one-pot facile strategy, and coimpregnation methods.
i
Table of Contents
1.
Introduction ...................................................................................................................... 1
2.
Porous Materials ............................................................................................................... 2
2.1.
What are Porous Materials? ........................................................................................ 2
2.2.
General Classification of Porous Materials ................................................................. 2
2.2.1.
Classification Based on Pores Size ...................................................................... 3
2.2.2.
Classification Based on Building Framework ..................................................... 4
2.2.3.
Artificial Porous Materials ................................................................................... 4
2.2.4.
Classification Based on Their Accessibility to Surroundings.............................. 5
2.2.5.
Classification Based on Their Pore Geometry and Shape ................................... 5
2.3.
3.
4.
Preparation of Porous Materials .................................................................................. 6
Characterization Techniques......................................................................................... 12
3.1.
XRD .......................................................................................................................... 12
3.2.
XPS............................................................................................................................ 13
3.3.
Adsorption-desorption of Gas ................................................................................... 13
3.4.
TPR............................................................................................................................ 15
3.5.
TGA........................................................................................................................... 16
3.6.
DTA........................................................................................................................... 16
3.7.
SEM........................................................................................................................... 17
3.8.
TEM .......................................................................................................................... 18
3.9.
FITR .......................................................................................................................... 18
Literature Survey ........................................................................................................... 19
4.1.
Low-Temperature
Catalytic
CO2 Dry
Reforming
of
Methane
on
Ni-
Si/ZrO2 Catalyst [28] ........................................................................................................... 19
4.2.
Synthesis of high sintering-resistant Ni-modified halloysite based catalysts
containing La, Ce, and Co for dry reforming of methane [29] ............................................ 20
4.3.
Design of Ni-ZrO2@SiO2 catalyst with ultra-high sintering and coking resistance
for dry reforming of methane to prepare syngas [30] .......................................................... 20
ii
4.4.
Catalytic performance of Samaria-promoted Ni and Co/SBA-15 catalysts for dry
reforming of methane [31] ................................................................................................... 21
4.5.
Understanding the differences in catalytic performance for hydrogen production of
Ni and Co supported on mesoporous SBA-15 [32] ............................................................. 21
4.6.
Highly efficient and stable Ni/CeO2-SiO2 catalyst for dry reforming of methane:
Effect of interfacial structure of Ni/CeO2 on SiO2 [33] ...................................................... 22
4.7.
Silica–Ceria sandwiched Ni core–shell catalyst for low temperature dry reforming of
biogas: Coke resistance and mechanistic insights [34] ........................................................ 22
4.8.
Dry reforming of methane on Ni-Fe-MgO catalysts: Influence of Fe on carbon-
resistant property and kinetics [35] ...................................................................................... 23
4.9.
Properties-activity correlation of Nickel supported on fibrous Zeolite-Y for dry
reforming of methane [36] ................................................................................................... 23
4.10.
Enhancing the dry reforming of methane over Ni-Co-Y/WC-AC catalyst:
Influence of the different Ni/Co ratio on the catalytic performance [37] ............................ 23
5.
Suggested Research Study ............................................................................................. 25
6.
References........................................................................................................................ 26
iii
List of Figures
Figure 1 – Schematic representation of open and closed pores. ................................................ 5
Figure 2 - Pores geometry classification [7] . ............................................................................ 6
Figure 3 – Supersaturation dependence on concentration, T and pH [2]................................... 6
Figure 4 – Supersaturation dependence on concentration, T and pH. ....................................... 6
Figure 5 – Principal methods for synthesizing mesoporous materials. ................................... 11
Figure 6 – Physisorption Isotherms ......................................................................................... 14
Figure 7 – TPR profile [16] ..................................................................................................... 16
Figure 8 – DTA curve; graph (a) displays the change in temperature over time for the
furnace, reference material, and sample. Graph (b) shows how the temperature difference
(ΔT) between the sample and reference changes over time, as measured by a differential
thermocouple [22]. ................................................................................................................... 17
iv
List of Tables
Table 1 – Classification of Nanoporous Materials [1]. .............................................................. 6
Table 2 – Summary of Literature Survey ................................................................................ 24
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1. Introduction
With the daily increase in human population, the demand on the food and energy also
increases resulting in more greenhouse gas emissions which are a major problem as they
contribute to climate change. Greenhouse gases such as carbon dioxide methane trap heat in
the Earth's atmosphere, causing the planet's temperature to rise. In accordance to this
problem, dry reforming of methane (DRM), a process that involves the conversion of
methane and carbon dioxide into a mixture of hydrogen and carbon monoxide, have a great
attention from researches as it allows for the utilization of methane, a potent greenhouse gas,
and the simultaneous capture and utilization of carbon dioxide, which is a major contributor
to climate change and convert them into a feedstock for the production of various chemicals
and fuels. Therefore, DRM has the potential to play a significant role in addressing some of
the major energy and environmental challenges that we face today. However, methane dry
reforming has several problems to encounter. The main problems can be listed as follows:

Operating temperature: DRM requires high temperatures of 600-850°C due its
endothermic nature. Such high temperatures can also lead to deactivation of the
catalyst over time due to sintering and coking.

A suitable catalyst: noble metal catalysts turn be very effective in DRM; however,
they are very expensive. Nonnoble can be used in DRM but most of them are prone to
deactivation over time due to sintering and coking. The catalysts to used must also
have high selectivity.

Side reactions: DRM have several side reactions such as formation of carbon deposits
and production of unwanted by-products such as water. The side reactions affect the
H2/CO product ratio.
In this graduation project, we are interested to further explore of dry reforming of methane
and present a new possible catalyst that with help to overcome the problems and limitations
of DRM. In order to effectively suggest a new study, we will firstly discuss what are porous
materials, porous materials preparation methods, discuss about the most important
characterisation techniques used in DRM, a make a literature survey to discover the types of
catalysts, promotors, and supports used in DRM.
1
2. Porous Materials
2.1. What are Porous Materials?
Due to its great importance in industries, the development of porous materials in the last
decades was exponential. In simple terms, any solid material that contains channels, holes,
voids, or pores is a porous material. This type of material has always attracted a lot of
attention as the presence of pores means that the material possesses an internal surface area of
interest for all type of applications. Porous materials play a critical role nowadays in many
sensitive fields such as energy and optics, chemical and biochemical, environmental,
electronics, biotechnological, and medical applications. That is all due there promising
characteristics like low density, large specific area, and others physical, thermal, and
mechanical properties which all primarily rely on the volumes, shape, and size distribution of
voids in the porous material. The uniformity of the shape, volume, and size distribution of
voids in the porous materials determines the application of the porous material – applications
such as adsorption, selection, sensing, removal, storage, release, chemical separation, and
catalysis.
In simple terms, porous solids are of two types, natural and artificial porous solids. We
encounter naturally occurring solids every day. Egg shells, sea sponges, honeycomb, hollow
bamboo, rocks, butterfly wings, and human bones are famous examples of ingenious porous
structures. The artificial porous materials can be divided as porous metals, porous ceramics,
and polymer foams with examples as concrete road, paper, fabric of clothes, chalk, ceramics,
cake, and bread [4].
In in the scope of this report, we will focus the industrial pores materials such as metal
oxides, mesoporous silica, zeolites, activated carbon, absorbents and adsorbents, and
catalysts. This report will continue to discuss how to classify porous materials and general
preparations to the industrial porous materials.
2.2.General Classification of Porous Materials
The porous materials are classified into different types, depending upon their pores size
(porosity), their materials constituents (such as organic or inorganic; ceramic or metal),
building framework, pore shapes, physical properties( pore size, accessibility to surroundings,
pore shape and geometry), etc. In this section, we will mention some of these classifications.
2
Before that, it is better to define some main terminologies such as porosity and surface are are
used to characterize porous solids [6]:

Porosity: is the ratio of the total pore volume to the apparent volume of the particle or
powder.

Pore size: also called as pore width or pore diameter, is the distance of the two
opposite walls or a pore.

Pore volume: is simply the volume (capacity) of the pore.

Pore geometry: is the shape of the pore.

True density: is the density of the material excluding pores and interparticle voids (the
density of the solid network)

Apparent density: is the density of the material including closed and inaccessible
pores.

Bulk density: is the density of the material including pores and interparticle voids
(mass per total volume where the total volume includes the volume of the solid
please, closed pores, and open pores).

Surface area: is the accessible or detectable area of the solid surface per unit mass of
the material.
2.2.1. Classification Based on Pores Size
IUPAC, The International Union of Pure and Applied Chemistry, has classified porous
materials into main three types according to the porosity of the porous material:

Macropores: porous materials with pore widths exceeding about 50 nm.
Macroporous have the greatest porosity in the porous materials family [3]. The most
popularly fabricating method is the colloidal templating route.

Mesopores: porous materials with pore widths between 2 nm and 50 nm.
Mesoporous materials are arranged as ordered array. The common examples of mesoporous
materials are MgO, ZnO, SiO2, TiO2, etc. There are lots of benefits are found for
3
mesoporous materials such as high surface area, tuneable pore size, periodically arranged
mesopore space, large open active sites. Hence, these materials are widely considering in
catalysis, drug delivery, adsorption, etc [3].

Micropores: porous materials with pore widths not exceeding about 2 nm.
Microporous have large surface area of about 300–2000 m2/g. The common microporous
crystalline compounds are metal organic frameworks (MOFs), AlPO4, and Zeolites.
2.2.2. Classification Based on Building Framework
Based on their building framework, porous materials are classified as [3]:

Porous organic materials: these are porous organic polymers (POPs).

Porous inorganic materials: these are derivatives of porous carbon and porous metal
oxides.

Hybrid materials: these are the combination of organic porous and inorganic porous
materials where they mostly consist of silica-based materials.
2.2.3. Artificial Porous Materials
These are classified as [3]:

Porous metals: consist of a solid metal/alloy matrix with empty or fluid-filled voids or
pores.
What makes porous metals of high importance is their high specific surface area, low bulk
density, low thermal conductivity, penetrability, and mechanical damping electromagnetic
shielding.

Porous ceramics: a class of highly reticulated ceramic material.
The porosity of porous ceramics mostly spans from 20 to 95%. They have good chemical
stability, strength, rigidity, and thermal stability.

Polymer foams: are porous plastics composed of bubble-like pores which contain
several
gaseous pores.
4
2.2.4. Classification Based on Their Accessibility to Surroundings
Figure 1 – Schematic representation
of open and closed pores.
Porous materials have two kinds of pores: open pores and closed pores. Figure 1 illustrates
these two kinds. Open pores can be interconnected open pores, passing open pores where the
pore(s) is open at two ends, or dead-end open pores where the pores are open only at one end
[3].
As it can be seen from Figure 1, closed pores are isolated from the outer layer of the porous
material, while on the other open pores are connected in the outer layer or the surface of the
porous material. Open pores are pores communicating with the external surface. They are
accessible for molecules or ions in the surroundings [3,5].
In short, open pores are accessible pores while closed pores are inaccessible.
2.2.5. Classification Based on Their Pore Geometry and Shape
Porous materials can be also classified according to their pore’s geometrical shapes. Kaneko
classified pores geometrical shapes as cylinder, slit-shape, cone-shape and ink-bottle which
are all shown in Figure 2 [7].
5
Figure 2 - Pores geometry classification [7] .
Table 1 summarizes the available nanoporous materials according to their chemical
compositions and their technical characteristics [1].
Table 1 – Classification of Nanoporous Materials [1].
2.3.Preparation of Porous Materials
There is no fixed direct standard preparation of porous materials.
The preparation process depends on the types of porous material
(catalyst, sorbent, absorbent) and its material (metal, carbon,
ceramic). However, there
are common preparations and
Figure 3 – Supersaturation
dependence on concentration, T and
pH [2].
6
preparation techniques such as preparation and mixing of solutions or suspensions,
crystallization, filtration, washing, mixing and kneading of powders, shaping drying,
impregnation and, calcination which are generally applied to get the desired porous material.
Regardless of the type of the catalyst, absorbent, or sorbent to be synthesized several unit
operations are common. There unit operations include chemical and physical transformations
to be applied, transformations based on fundamental inorganic chemistry, operation variables
such as temperature, pressure, pH, time, concentration, general characteristics of the products
of the operation, and the type of the required apparatus. The most common unit operations in
the preparation of a catalyst, absorbent, or a sorbent are [2]:
1. Precipitation: The aim of this step is to precipitate a solid from a liquid solution. In an
aqueous solution of a metallic salt, a precipitating agent is added in order to form a
crystal or gel of hydrated oxides, carbonates, or gels. Precipitation occurs in three
steps: supersaturation, nucleation, and growth. Figure explains the precipitate
formation based on solubility showing how solubility curves are functions of
temperatures and pH.
2. Gelation: Hydrophilic colloidal solutions are formed of micelles that remain separated
because of electrical charges
on their surfaces and in the
surrounding solution. These
charges create repelling
forces which prohibit
coagulation of the micelles.
The reticulation of these
micelles gives rise to a
hydrogel, a threedimensional network that
imprisons molecules of
Figure 4 – Formation of gels and flocculates.
water.; this is also known as
sol-gel process. The flocculation of a sol can be obtained through the neutralization of
the micelle charges (Fig. 3). The micelles thus coagulate into flocculates that more or
less precipitate well.
7
Sol-gel methods have several promising advantages over precipitation as they offer better
control over surface area, pore volume, and pore size distribution. Flocculates are denser than
hydrogels; the service area of the final full site depends on the size of the original micelle and
on the ripening and drying conditions.
3. Hydrothermal transformation: are transformations which are induced by temperature.
After precipitation, gelation, or flocculation, modifications on the product in hand is
done. These modifications are done in the presence of the mother liquor which is
usually water. Such modifications and transformations are carried out at temperatures
around 100 and 300 degrees Celsius resulting in textural or structural modifications
such as:

small crystals to large crystals.

small amorphous particles to large amorphous particles

amorphous solid to crystalline solid

crystal 1 to crystal 2

high porous gel to low porous gel (Aging or syneresis of a gel)
Besides temperature, pH, pressure, and concentration affect the results of the
modifications. How do thermal transformations can be done separately or during other
unit operations such as precipitation washing drying and extrusion.
4. Decantation, filtration, and centrifuging: separation of the solid from the mother
liquor is done. The separation method depends on the size of the solid and its type.
5. Washing: remove stain remaining mother liquor completely and eliminates any
impurities
6. Drying: eliminates the solvent from the powers of a solid
7. Calcination: a further he treatment beyond drying. Calcination usually takes place in
air at temperatures higher than those in the catalytic reaction and catalytic generation.
That is because physical and chemical properties of the solid might change at high
temperatures; therefore, temperatures higher than those in the catalytic reaction and
8
catalytic generation must be applied to prevent such properties changes from taking
place during reactions.
8. Forming operation: applied to obtain suitably sized particles of catalyst to be used in
the reactor. This step is important as it promote catalytic activity, strengths the
particle resistance to crushing, and minimize pressure drop.
9. Impregnation: The carrier is immersed in a solution containing active components.
After reaching equilibrium, the remaining liquid is removed (or the solution is
immersed in solid), and the catalyst is obtained after drying, calcining and activation
10. Crushing and grinding centrifugation
11. Mixing
12. 12. Activation
13. Ionic exchange
Most catalyst formulations involve a combination of some or even all these operations.
However, even though the preparation procedures differ considerably from one catalyst to
another, three broad categories can be introduced to classify the catalysts with respect to the
preparation procedure [2]:
1. Bulk catalysts and supports: they are mainly comprised of active substances.
Important examples include silica alumina for hydrocarbon cracking. The supports are
prepared by similar procedures (e.g. aluminas, silicas, silica aluminas).
The main unit operation for a bulk catalyst are precipitation, gelation and flocculation,
hydrothermal transformation, decantation, drying, calcination, and forming operations.
2. Impregnated catalysts: usually obtained from preformed supports by impregnation
with the active phase. Quite several hydrogenation catalysts are prepared in this way .
3. Mixed-agglomerated catalysts: obtained by mixing the active substances with a
powdered support or a support precursor and then agglomerating the mixture. As far
as the techniques are concerned, such catalysts can be considered bulk catalysts. But
as the mixing operation often consists of impregnating a powder with a solution of the
9
active substance precursors, the catalysts so obtained may be regarded as impregnated
catalysts.
The main unit operations for supported catalyst are

Support selection: alumina and silica are good examples for catalyst support as
they are inert, have desirable mechanical properties, stable under reaction
conditions, have high surface area, needed porosity, and low in cost.

Incorporating active metals on the support either with precipitation or
impregnation.
There are also common preparation methods depending on the pore size of the material. Let
us take the preparation of mesoporous materials as an example. The preparation of
mesoporous materials is classified into template-assisted (soft-templating and hardtemplating) and template-free syntheses [3]. The two methods are summarized in Figure 4.
10
Figure 5 – Principal methods for synthesizing mesoporous materials.
11
3. Characterization Techniques
Characterization Techniques are used to analyse the surface composition and chemistry of a
material. These techniques are important because they allow scientists and researchers to
understand the fundamental properties of materials and how they may be used in various
applications. For example, researchers use techniques like XRD is used to identify the
crystalline structure of a material, TEM and SEM to observe the microstructure of materials
at high magnifications, TPR to study the reduction behaviour of materials, and the list goes
on.
In this section, we will explain some the most important characterization techniques used in
dry reforming of methane.
3.1.XRD
XRD is a continuously developing method that uses X-rays – high energy light – to
determine and identify the material structure of a sample at the atomic scale. This method is
based on the principle that each crystal, due to the unique atomic arrangement of the phase,
diffracts X-rays in a characteristic pattern. These unique diffractions for each crystal can be
identified as a fingerprint for the crystal [8].
Detection of materials using XRD kindly relies on interference. Interference occurs when Xrays interact with each other. If the waves are in alignment, the signal is amplified. This is
called "constructive interference". If the waves are out of alignment, the signal is destroyed.
This is called "destructive interference". X-rays are beamed using X-ray tube moving in a
synchronized motion with a detector. The energy that the X-rays possess are absorbed by the
electrons in the crystals. As the absorbed energy is not enough to excite electrons out of their
energy level, the absorbed energy must be re-emitted as a new X-ray with the same energy as
the absorbed to bring stability to the electrons. This is also known as elastic scattering. Strong
amplification of the emitted signal occurs at very specific angles where the scattered waves
constructively interfere. This effect is called "diffraction" [9].
XDR plays a vital role in characterizing porous materials. XRD is used to assess
the crystallinity, lattice parameters, crystalline grain size, and structure of solid samples. The
X-ray diffraction analysis method does not damage the sample during analysis. The samples
are in the powder form. Qualitative and quantitative examinations of ceramics, catalysts, thin
films, and polymers can be made with an X-ray diffraction diffractometer. X-ray diffraction
12
diffractometers give us results of the elements in its compound form. XRD are not suitable
for amorphous materials and for low atomic number elements [8,9].
3.2.XPS
XPS is one of the most powerful quantitative analytical techniques which operates under
ultra-high vacuum conditions to elucidate the electronic structure, elemental composition,
oxidation states, and ligand bindings of porous materials [10].
X-ray photoelectron spectroscopy (XPS) is known for its excellent sensitivity to elements as
well as their valence states, which is extensively employed to characterize the structure of
modifying molecules and their interactions with metal centres. Notably, most modifying
molecules are composed of elements such as C, N, O, P, S, which can be precisely
distinguished by XPS [11].
X-ray photoelectron spectroscopy uses different light sources to learn about the interactions
and positions of atoms and their electrons this is done using photo electron spectrometer
which use a high-energy light source to energize the sample. This light source is usually
invisible light in the form of x-rays. Electrons within a sample absorb photons of a particular
energy and then emerge from the solid. The kinetic energy analysis of electrons emitted from
the surface yields information on the electronic states of atoms in the surface region [12].
3.3.Adsorption-desorption of Gas
The absorption-desorption of gas is one of the most of not the most used method for surface
area and pore size characterization of porous materials. The absorption-desorption of gas
method measures the physical properties of porous materials [13].
The most popular method for surface and pore size characterization is the physisorption and
adsorption of gas as this technique allows the characterization of mesopores ranging from 2
up to 50 nanometres. Adsorption is the enrichment of one of one or more components on a
layer. Desorption is simply the opposite of adsorption. Physisorption is a general
phenomenon which occurs whenever an adsorbable gas is brought into contact with a surface
of a solid (known as the adsorbent).
13
Figure 6 – Physisorption Isotherms
There are several physisorption isotherms. They can be grouped into six types as shown in
Figure 1. Each isotherms gives information about the analysed material, whether it is
mesoporous, microporous, or macroporous as an example [13,14].
Based on the adsorption/desorption isotherms, a method known as BET (Brunauer-EmmettTeller) can be used to calculate pore volume filling and pore size distribution. In this method,
as the relative pressure (atmospheric pressure corrected to sea-level conditions) is increased
more and more molecules absorb on the surface. Thin layer will eventually cover the interior
surface in a single or monolayer. The number of gas molecules in the monolayer is recorded
from the volume absorbed. Nitrogen gas is the most common used gas for this technique.
Since the cross-sectional area of the absorbate is known, the area of the accessible surface
may be calculated; however, gas absorption is a function of pressure which does not follow a
simple linear relationship [15]. Therefore, BET equation uses an appropriate mathematical
model to calculate the surface area. BET equation is valid in a range of partial pressure
ranging from 0.05 up to 0.3.
BET is most accurate measurement for surface area, pore size distribution, and volume-pore
distribution. In the BET device, samples are put inside sample holders, The samples are
inserted inside a vacuum chamber for sample preparation before measurement. The sample
holders are then taken to the measurement chamber to analyse the samples [14] .
The BET equation is written as follows:
14
𝑆=
𝑁𝑋 𝜎
𝑀
Xm: the mass of the gas adsorbed as monolayer at a relative pressure P/P0
P0: the saturated vapour pressure
C: BET constant
S: total surface area
NA: Avogadro’s number
M: molecular weight of adsorbate
𝜎: cross sectional area of adsorbate
3.4.TPR
Temperature programmed reduction, also known as TPR, is a characterization technique used
to analyse the reduction of metal oxide catalysts with hydrogen, a reducing agent, at different
thermal conditions [16]. TPR can be used for both quantitative and qualitative analysis
especially if it was enabled with mass spectroscopy equipment. while performing at TPR
experiment the catalyst to be investigated is it placed on a fixed bed reactor where a gas
mixture flows of 10% hydrogen and 90% inert gas (argon and nitrogen are the most common)
over the catalyst. The heat in the reactor is increased linearly and the reduction of the catalyst
is plotted against time [17,18]. As hydrogen has a high electrical conductivity, the amount of
reduction can be detected as the concentration of hydrogen in the gas mixture decreases. To
measure the conductivity, a thermal conductivity detector is used [18].
Temperature programmed reduction is useful for measuring the temperature necessary for the
complete reduction of a catalyst. It is mostly commonly used to investigate the interaction of
a metal catalyst with its support or the effect of promoter on metal catalyst [16].
Each TPR profile is a fingerprint for the material investigated as shown in the figure below.
15
Figure 7 – TPR profile [16]
3.5.TGA
Thermogravimetric Analysis (TGA) is an analytic technique where changes in weight of a
sample is continuously recorded as a function of temperature or time. TGA provides a
comprehensive view of the changes in the mass of a material during the test process [20].
Generally, during the analysis, inert gas such as nitrogen passes over the sample to take the
formed gas due to decomposition of the solid upon heating. Only solid samples can be
analysed using TGA. TGA provide both quantitative and qualitative analysis.
The plot of a TGA is called a thermogram. TGA used in various sectors to analyse
pharmaceuticals, foods, ceramics, catalysts, and more. TGA measures the composition,
purity, decomposition reactions, decomposition temperature and absorbed moisture content
of your products. In a TGA experiment, the temperature maybe constant or changed linearly,
A series of increasing temperatures can also be applied [19]. TGA can also help in the
determination of the stability of a drug and the purity of inorganic and organic compounds. It
can also help in analysing reactions involving air, oxygen, and other reactive gases.
3.6.DTA
Differential Thermal Analysis (DTA) is a thermoanalytical technique where the temperature
difference between a sample and a reference material is measured as the sample is heated or
16
cooled under controlled conditions in a specified atmosphere. The sample and reference
materials are placed in separate pans within a DTA instrument, and the temperature
difference between the two is measured using a thermocouple [21]. The reference material is
typically made of a non-reactive substance like alumina, and the temperature difference is
plotted as a function of time or temperature. As the sample and reference are heated or cooled
under controlled conditions, the temperature difference is plotted as a function of temperature
or time. This plot, called a DTA curve, can be used to identify thermal events occurring
within the sample, such as phase transitions, chemical reactions, and melting or boiling
points. This curve can be used to identify endothermic and exothermic reactions within the
sample; moreover, the area and height of the peaks in the DTA curve can also be used for
quantitative analysis. DTA is often used to study the thermal stability of materials and to
characterize their thermal behaviour [22].
Figure 8 – DTA Curve; graph (a) displays the change in temperature over time for the furnace, reference material, and
sample. Graph (b) shows how the temperature difference (ΔT) between the sample and reference changes over time, as
measured by a differential thermocouple [22].
3.7.SEM
Electron technology is way beyond transferring electrical current. Electron microscopy can
give 1,000 times higher resolution visualization than the normal classical light microscopy
which as typically used in biology labs. That is due to the fact that electron microscopy does
not use light but electron beams. As electron beams have shorter wavelength compared to
light, electron microscopes can visualize a specimen at 1,000,000 times their original size
[23].
17
Scanning electron microscopy, or SEM, one of the most well-known electron microscopes
used to obtain high resolution pictures of material surfaces at nanoscale. With SEM,
specimens are coated with vaporized gold or palladium ions, because when electrons come
into contact with this coating, they cause atoms on the surface of the specimen to emit
electrons. These emitted electrons are called secondary electrons, and these are what SEMs
use to visualize their specimen [23,24].
SEM captures the secondary electrons that are emitted from the surface of samples and
analyse them using detectors to give a 3D image of the sample. SEM is used to analyses
activate carbon, catalysts, porous materials, and other nanoscale 2D materials such as mxenes
[24].
3.8.TEM
Transmission Electron Microscopy, or TEM, captures the different energy that electrons have
after passing through a heavy metal-stained object to examine minute, detailed structures.
Because it gives not only direct pictures of the sample but also the most exact assessment of
nanoparticle homogeneity, TEM is the most often used technology for analysing data particle
size and shape. But even with the unmatched resolution and magnification abilities of TEM,
it still does have its limitations. Some of these include the fact that you cannot study living
specimens or image 3D structures because the specimens must be dehydrated and cut into
ultra-thin slices before imaging [24].
For porous materials, HRTEM, High-Resolution TEM, is commonly used to characterise the
internal structure of porous materials. HRTEM uses phase-contrast imaging where both
transmitted and scattered electrons are combined to produce a high-resolution image.
3.9.FITR
FTIR spectroscopy is a technique that uses infrared light to measure the vibrational
frequencies of bonds in a molecule and the absorption of infrared radiation by a sample. It
involves shining infrared light through a sample and measuring the absorption at different
wavelengths, which allows researchers to identify the functional groups present in the
sample. The resulting spectrum shows the vibrational modes of the bonds in the molecule
[25].
18
FTIR spectroscopy is commonly used in catalysis research because it enables researchers to
identify the functional groups present on catalysts, study their activity under different
conditions, and understand their interactions with reactants and products. This technique can
be used to analyse the chemical composition of catalysts, determine their surface structure
and composition, and study changes in their surface chemistry during a reaction [26]. It can
also be used to monitor the progress of a reaction and identify intermediate species formed. In
summary, FTIR spectroscopy is useful for understanding the behaviour of catalysts and
improving their performance in chemical reactions.
4. Literature Survey
In this section, catalysts mentioned in 10 different papers are summarized and discussed. The type of
catalyst used, the promotor type, the used support, the characterization techniques used, and results of
the studies are the main concern this section. The aim is have knowledge about the catalysis used in
dry reforming of methane and to suggest a new study to undergo with in the following semester.
The name of the article and its reference will be mentioned before each article’s summary. The
observed studies will be also tabulated at the end of this section.
4.1.Low-Temperature Catalytic CO2 Dry Reforming of Methane on Ni-Si/ZrO2 Catalyst
[28]
Ye Wang et al. compared nickel catalyst promoted by silica (Ni-Si/ZrO2) on a ZrO2 support to nickel
catalyst promoted by Zr (Ni-Si/ZrO2) on a SiO2 support from their older studies for low-temperature
DRM reaction at 400 °C and 450 °C. The main goal is to be the differences in carbon deposition, the
stability of the nickel metal, and the activity of both catalysts at the mentioned temperatures. The tests
were conducted using 0.25 grams of catalysts in a fixed-bed tubular quartz microreactor under
atmospheric pressure. The effluent stream was then analysed used an online gas chromatograph. H2TPR, XRD, TEM, TG-MS, Raman, XPS, and in situ XPS, and DRIFTS characterizations were used
to conduct data regarding particle size, coke amounts, reduction of Ni, etc. They found that NiSi/ZrO2 deposited more carbon than Ni-Zr/SiO2. The majority of NiO species were easily reduced on
Ni-Si/ZrO2 catalyst compared to Ni-Zr/SiO2 and that is due to the amount of silica (the lower the less
the interaction of nickel with silica the more reduction of NiO). Ni-Si/ZrO2 catalyst showed higher
initial conversions for both greenhouse gases (CH4 (4.3%) and CO2 (3.8%)) compared to Ni-Zr/SiO2
catalyst at 400 °C. Moreover, the Ni-Si/ZrO2 catalyst showed higher stability and had a 3.2% CH4
and 2.3% CO2 conversions after 15 hours of reaction while at the same time period Ni-Zr/SiO2
catalyst was completely deactivated. It is worth to mention that the Ni-Zr/SiO2 catalyst formed a
small size of 6-9 nm active nickel particles. Under 400 °C, the formed coke was C1 coke which can
19
be easily removed; however, at 450 °C, the coke formed was mainly C2 coke which it different to
remove.
4.2.Synthesis of high sintering-resistant Ni-modified halloysite based catalysts containing
La, Ce, and Co for dry reforming of methane [29]
As sintering of the catalyst is one of the biggest problems in DRM, K. Bakhtiari et al
synthesised Ni-
modified based catalysts with different metal promoters. As halloysites (small, tube-like clay
minerals that are composed of aluminum, silicon, and oxygen) have high thermal conductivity,
chemical stability, and high surface area due to its porous structure, they help in having a longer
catalyst lifetime by lowering the coke deposition and sintering. They modified halloysite nanotubes by
alkaline molten method which results in defected nanosheets by etching the outer silica layer; this leads to
CO2 adsorption. Alongside nickel, they used Co, Ce and La as a second metal promoters to see how
this will affect selectivity, activity, catalyst deactivation, and activity. The catalysts were prepared by
etching the outer silica layer using alkaline molten treatment followed impregnation method resulting
in (Co, Ce and La)-Ni/halloysite catalysts. TPR, SEM, BET, XRD, and TPO characterisations were
performed for the prepared samples. The formation of halloysite nanosheets was confirmed from the
XRD and TEM results. All of the prepared samples showed strong interactions between the metals
and the support due to their good confinement throughout the halloysite structure; this resulted in
amazing sintering-resistance under reaction conditions. All of the added second metal promoters
showed an increase in the stability and activity of the nickel halloysite supported catalysts. Co–
Ni/halloysite catalyst has the best performance and activity with 89% and 91% initial conversions and
CH4 and CO2 respectively at 850 °C. Moreover, in 600 min time-on-stream tests, the Co–Ni/halloysite
catalyst had the best stability as it resisted carbon formation due to its enhanced oxygen capacity were
the stability test.
4.3.Design of Ni-ZrO2@SiO2 catalyst with ultra-high sintering and coking resistance for
dry reforming of methane to prepare syngas [30]
W. Lie et al. designed a novel core-shell catalysts where the shell is microporous silica and the core is zirconiamodified nickel nanoparticles (Ni-ZrO2@SiO2) using one-pot facile strategy. To test the performance of the
catalyst, reaction conditions ranging from 550 to 800 °C under atmospheric pressure were conducted. The Ni-
ZrO2@SiO2 catalyst showed excellent stability for 20 h continuous reaction under 800 °C with
methane and carbon dioxide conversions being 92.1% and 94.8% respectively. During the 20-hour
stability test, there was no drop in the methane and carbon dioxide conversions. Moreover, a 240 h
durability test was conducted at 800 °C where the Ni-ZrO2@SiO2 catalyst showed no deactivation
20
with the CH4 and CO2 conversions being were 90.5% and 93.2% respectively with a H2/CO ratio
close to one. TEM, XDR, Raman, HAADF-STEM, BET, and TPD analyses were performed. The
resulted showed that the ZrO2 and the Ni active sites are evenly distributed. As, nickel nanoparticles
were used, Ni-ZrO2@SiO2 catalyst had many active sites. Furthermore, the addition modified ZrO2
resulted in the nickel active sites have great interaction with the silica shell resulting in no carbon
formation and sintering resistance.
4.4.Catalytic performance of Samaria-promoted Ni and Co/SBA-15 catalysts for dry
reforming of methane [31]
M. Yousefpour et al. investigated the usage of samarium (Sm) metal as a promoter for cobalt (Co) and
nickel (Ni) SBA-15 catalysts with the main goal being to produce a stable catalyst with high metal
surface area and surface oxygen concentration. The catalysts were 10% by weight cobalt or nickel
with 0.5, 1, and 1.5% by weight samarium. The catalysts were prepared using two-solvent
impregnation method as this method helps in filling the porous of the support with metals and
promoters which leads in increasing the active surface area of the catalyst. by N2 adsorptiondesorption, XRD, SEM, HRTEM, TPR, and TGA analysis were performed. TEM and XRD results
showed that one percent by weight Sm promoted catalysts had the smallest particle sizes for and the
best metal dispersion. For the 1% wt Sm catalysts, at 700 °C, the nickel SBA-15 supported catalyst
had a conversion of around 58% while the cobalt supported catalyst has a conversion of 25% only.
Comparing the promoted catalysts to unpromoted catalysts on the same support, the samarium
increased in the activity of the nickel catalyst but caused deactivation in the cobalt catalyst. The
addition of Sm as a promoter to Ni/SBA-15 resulted in smaller nickel oxide particles and higher
dispersion resulting in lower carbon deposition which was confirmed with characterization results.
4.5.Understanding
the
differences
in
catalytic
performance
for
hydrogen
production of Ni and Co supported on mesoporous SBA-15 [32]
A. Caballero et al. studied the activities of three different catalyst of nickel and cobalt using SBA-15
as a support were the interaction between the metal (or metal-mixture) and the support in the main
consideration. The catalysts were synthesized using the deposition-precipitation method where the
catalysts had a 10% metallic content; the first catalyst is totally nickel, the second is totally cobalt, and
the third is an equal mixture of both. The catalysts had different behaviours. The catalysts were
characterized by BET, XRD, TEM, TPR, XAS and XPS. The Ni/SBA-15 catalyst was the most stable
having the highest activity with a metal particle size of 5 nm; the nickel particle size remained
constant throughout 48-hour DRM reaction analysis. The cobalt catalyst had bigger particles after
reduction and turned to be inactive under reaction conditions. The NiCo/SBA-15 catalyst had an
initial activity similar to that of Ni/SBA-15 then a sudden inactivation was the particle size increased
from 6nm to 8nm. The performed characterization analyses explain that the major factor behind the
21
activity of the nickel and the inactivity of the cobalt catalysts is the interaction between the metals and
the mesoporous SBA-15 support. The cobalt and the bimetallic catalyst had a weak interaction with
the support leading to particles enlargement under DRM reaction, coke deposition, and sintering.
4.6.Highly efficient and stable Ni/CeO2-SiO2 catalyst for dry reforming of methane:
Effect of interfacial structure of Ni/CeO2 on SiO2 [33]
Seeking to produce a catalyst with a higher metal-support interaction, X. Yan et al. fabricated two Ni
and CeO2 catalysts on a SiO2 support aiming also to achieve a stable highly selective catalyst. Both
catalysts had 5% Ni and 5% CeO2 by weight where one catalyst and synthesised using wet
impregnation method which afterwards one of the was thermally decomposed and the later was
decomposed by plasma. DRIFTs, TG-MS, STEM-EDX, TEM, XPS, H2-TPR, and XRD
characterizations were made. The plasma decomposed catalysts (Ni/CeO2-SiO2-P) showed to have
fewer defective sites, smaller particles, and a stronger interaction between the Ni and the support
compared to the thermally decomposed catalyst (Ni/CeO2-SiO2-C). Moreover, the Ni/CeO2-SiO2-P
catalyst had CeO2 with more reactive oxygen species. One hour conversion tests at 600, 700, and 800
°C were conducted and it was found that Ni/CeO2-SiO2-P have a marvellous activity at low
temperatures and conversions compared to Ni/CeO2-SiO2-C. Ni/CeO2-SiO2-P had an 87.3%
conversion CO2 and a 78.5% CH4 conversion with a 0.89 H2/CO ratio compared to 80.5% and
67.8% CO2 and CH4 conversions with a H2/CO ratio of 0.85. The conversion of CO2 is higher that
that of CH4 due to the reverse water gas shift reaction; in addition, as higher H2/CO ratio means that
the reverse water gas shift reaction is less favoured. Therefore, Ni/CeO2-SiO2-P has better reaction
selectivity with H2/CO ratio being 0.89 and 0.94 at 700 and 800°C respectively. Stability test showed
that, on the long term, Ni/CeO2-SiO2-P was stable after 10 hours of reaction where on the other hand
the Ni/CeO2-SiO2-C showed poor stability with the activity to severely drop after 10 hours.
4.7.Silica–Ceria sandwiched Ni core–shell catalyst for low temperature dry reforming of
biogas: Coke resistance and mechanistic insights [34]
S. Das et al. designed a silica-ceria nickel core and shell catalyst where the with nickel metallic
nanoparticles being at the core surrounded by a spherical silica core and a thin cerium oxide shell. To
have a highly dispersed nickel on silica, Ni-phyllosilicate was used as Ni precursor. The catalyst was
analysed by TEM, XRD, BET, DRIFTS, TEM, XRD, H2-TPR, and XPS. The tests illustrate that the
core shell Ni-SiO2@CeO2 catalysts has a great interaction between the metal and the support. The
catalyst was tested under a 1.5 CH4 to CO2 molar ratio stream at 600 °C for a reaction time exceeding
3 days with negligible coke formation taking take with the methane conversion activity being 0.12 mol
CH4 min-1 g metal-1. The dual confinement effect of the strong interaction between Ni and the silica
core and ceria shell helps prevent metal sintering and inhibits the growth of carbon whiskers, which
can cause Ni to detach from the support material.
22
4.8.Dry reforming of methane on Ni-Fe-MgO catalysts: Influence of Fe on carbonresistant property and kinetics [35]
K. Zhu et al. explored the effect of adding iron as a promotor to nickel catalysts on a MgO support.
Several catalysts with Fe/(Ni+Fe) ratios ranging 0 to 0.17 were produced using solvothermal synthetic
method producing FexNiyMg1-x-yO catalysts were x and y are between 0 and 0.07 each. The catalysts
were characterised using XRD, SEM, TEM, HAADF-HRTEM, H2-TPR, CO2 (O2)-TGA and CO2TPO techniques. The results show that the Ni-Fe alloy successfully decreased coke formation on the
surface catalyst. Moreover, the presence of iron increased the surface of oxygen converge and
converted the type of coke deposed to type that can be easily removed in the presence of CO2.
Although the iron increased the stability of the catalyst and prevented sintering, it was found that with
increasing the amount of iron in the catalysts the activity of the nickel decreased leading to lower
methane and carbon dioxide conversions with the CO2 conversions being higher than those of CH4
due to the influence of the reverse water-gas shift reaction. the Ni0.07Mg0.93O-R catalyst showed the
highest activity; the conversion of CH4 initially increases quickly from 52% to 73% over the first 17
hours at 760°C, and then remains stable with no significant decrease in activity with a H2/CO ratio
near 0.8. Kinetic wise, at low iron loadings, it was found that iron slowed the coke deposition rates
and accelerated a surface coke gasification rate without affecting the mechanism of nickel.
4.9.Properties-activity correlation of Nickel supported on fibrous Zeolite-Y for dry
reforming of methane [36]
Using zeolite-Y (HY) as a seed and using microemulsion technique as the synthesis method, Miskan
SN et al. synthesized a nickel catalyst supported on a fibrous zeolite-Y (Ni/FHY). BET, FTIR, TPO,
FESEM, EDX, H2-TPR, TEM, and XRD experiments were made. The findings conclude that, thanks
to the fibrous structure of FHY, Ni/FHY possessed good NiO distribution, improved metal-support
interface compared to Ni/HY, and had strong basicity. Moreover, this unique morphology resulted in
enriching the accessibility to the Ni active sites resulting in spectacular conversions of CH4 and CO2
(95.1% and 91.1% respectively with H2/CO = 0.89 at 800 °C). The decrease in the syngas ratio is due
RWGS.
4.10.
Enhancing the dry reforming of methane over Ni-Co-Y/WC-AC catalyst:
Influence of the different Ni/Co ratio on the catalytic performance [37]
J. Liu et al. studied the significance of using Yttrium (Y) as a promotor for different Ni/Co ratios on a
tungsten carbide (WC) activated carbon (AC) compound support. The catalysts were prepared using
the co-impregnation method. The physical and chemical properties of the catalysts were analysed
23
using a variety of techniques, including H2-TPR, TEM, XRD, FTIR, TG, BET, Raman, and XPS. The
addition of Y decreases the particle size of the nickel metal grains, reduced the total basicity of the
catalyst, increased catalyst’s activity, and enhanced stability. The effects of the different Ni/Co ratios
on the activity, stability, and texture properties of the catalysts were investigated for the Ni-Co/WCAC where the results showed that the introduction of a certain amount of Co improved the catalytic
activity and stability of the catalysts, likely due to the synergistic interaction between Ni and Co and
the formation of oxygen vacancies. The 10Ni-8Co-10Y/WC-AC catalyst showed high activity with
conversions of CO2 and CH4 of 95% and 88% at 800°C and atmospheric pressure, respectively.
Table 2 – Summary of Literature Survey
Authors
Characterisation Techniques
Results
H2-TPR, XRD, TEM, TG-MS, Raman, XPS, and in situ
XPS and DRIFTS
The Ni Si/ZrO2 catalyst exhibited
higher catalytic activity and stability
than the Ni-Zr/SiO2 catalyst in low
temperature DRM reactions.
TPR, SEM, BET, XRD, and TPO
With 89% and 91% CH4 and CO2
initial conversions, Co promoted
halloysite-supported Ni catalyst has the
best stability, activity, and the least
deactivation.
550–800 °C at 1 atm
TEM, XDR, Raman, HAADF-STEM, BET, TPR, and TPD
The addition of modified ZrO2
alongside nickel nanoparticles reduce
the coke deposition and results in a
high sintering resistance.
M. Yousefpour et al., 2017 Samaria-promoted Ni and Two-solvent incorporation
[31]
Co/SBA-15 catalysts
method
100-700 °C at 1 atm
N2 adsorption-desorption, XRD, SEM, HRTEM, TPR, and
TGA
A. Caballero et al, 2017 [32]
Ni and Co SBA-15
supported catalyst.
Deposition-precipitation
method
-
X. Yan et al., 2019 [33]
Ni/CeO2-SiO2
Wet impregnation method
with either thermal or
plasma decomposition
600, 700, and 800 °C at
1 atm
S. Das et al., 2018 [34]
Silica-ceria nickel core
and shell catalyst
Precipitation method
600 °C at 1 atm
Negligible coke deposition at 600°C
TEM, XRD, BET, DRIFTS, TEM, XRD, H2-TPR, and XPS with methane conversion activity being
-1
-1
0.12 mol CH4 min g metal
K. Zhu et al., 2019 [35]
Ni-Fe alloy on a MgO
support
Solvothermal synthetic
method
760 and 800 °C at 1 atm
Iron helps in preventing sintering and
XRD, SEM, TEM, HAADF-HRTEM, H2-TPR, CO2 (O2)enhance coke formation resistance, but
TGA and CO2-TPO
passivates the activity of nickel.
800 °C at 1 atm
Ni/FHY had good sintering and coke
formation resistance with 95.1% and
91.1% CH4 and CO2 conversions at
BET, FTIR, TPO, FESEM, EDX, H2-TPR, TEM, and XRD 800 °C. The unique fibrous structure
resulted in improved metal-support
interface and the accessibility to the Ni
active sites.
800 °C at 1 atm
The 10Ni-8Co-10Y/WC-AC catalyst
showed high activity with conversions
of CO2 and CH4 of 95% and 88% at
800°C and atmospheric pressure,
respectively where the Y decreases the
particle size of the nickel metal grains,
reduced the total basicity of the
catalyst, increased catalyst’s activity,
and enhanced stability.
Ye Wang et al., 2018 [28]
Catalysts
Nickel catalyst promoted
by silica (Ni-Si/ZrO2) on
a ZrO2 support
M-Ni/halloysite catalysts
K. Bakhtiari et al., 2022 [29]
(M = Co, Ce and La)
W. Lie et al, 2018 [30]
Miskan SN et al., 2022 [36]
J. Liu et al.,2022 [37]
A novel core-shell
catalyst with zirconiamodified nickel
nanoparticles (NPs, NiZrO2) as the cores and
microporous silica as the
shell (denoted as NiZrO2@SiO2)
Nickel catalyst supported
on a fibrous zeolite-Y
Ni-Co-Y/WC-AC
Synthesis Method
Impregnation method
Impregnation method after
etching the silica from the
outer layer by the alkaline
molten treatment
One-pot facile strategy
Microemulsion technique
Co-impregnation method
Reaction Conditions
400 and 450 °C at 1 atm
700–850 °C at 1 atm
Ni/SBA-15 promoted by 1% wt Sm
had a 58% conversion at 700 °C
compared to 25% for Co/SBA-15
promoted by 1% wt Sm
Ni has a good interaction with SBA-15
support while Co does not. Weak
BET, XRD, TEM, TPR, XAS and XPS
interaction leads to particle size
enlargement and sintering.
Plasma decomposition result in small,
stable nanoparticle nickel particles on
DRIFTs, TG-MS, STEM-EDX, TEM, XPS, H2-TPR, and SiO2 support. 87.3% conversion CO2
XRD
and a 78.5% CH4 conversion with a
0.89 H2/CO ratio were achieved at 700
°C.
H2-TPR, TEM, XRD, FTIR, TG, BET, Raman, and XPS.
24
5. Suggested Research Study
Under the light of the results obtained from the literature survey, a plasma decomposed
nickel-based catalyst on a KIT-6, SBA-15 supports, and fibrous zeolite-Y with Y, Zr, and Ce
as promotors will be synthesised by microemulsion, one-pot facile strategy, and coimpregnation methods. This decision came considering the effectiveness of the selected
promotors and their effect in producing small nanoparticle size nickel particles and enhancing
sintering resistance. Moreover, the selected supports have good to high thermal conductivity,
chemical stability, high surface area, and excellent interaction with the metals. I would like to
investigate the activity and performance difference that the KIT-6 and SBA-15 supports will
give using the selected promotors and synthesis methods, and how would the promotors
affect the fibrous zeolite-Y activity and the accessibility to the Ni active sites. Such catalysis
has not been studied before which open space for new findings.
25
6. References
[1] Lu, G., & Zhao, X. (2006). Nanoporous materials. London: Imperial College Press.
[2] Perego, C., & Villa, P. (1997). Catalyst preparation methods. Catalysis Today, 34(3-4),
281-305. doi: 10.1016/s0920-5861(96)00055-7
[3] Uthaman, A., Thomas, S., Li, T., & Maria, H. (2022). Advanced Functional Porous
Materials. Cham: Springer International Publishing.
[4] Voort, P., Leus, K., & Canck, E. (2019). Introduction to porous materials. Wiley.
[5] Zdravkov, B., Čermák, J., Šefara, M., & Janků, J. (2007). Pore classification in the
characterization of porous materials: A perspective. Open Chemistry, 5(4), 1158. doi:
10.2478/s11532-007-0039-3
[6] Schubert, U., & Hüsing, N. Synthesis of inorganic materials.
[7] Kaneko, K. (1994). Determination of pore size and pore size distribution. Journal Of
Membrane Science, 96(1-2), 59-89. doi: 10.1016/0376-7388(94)00126-x
[8] Tekade, R. K. (2019). Basic Fundamentals of Drug Delivery. London: Academic Press,
an imprint of Elsevier.
[9]
Biomedical
Sciences.
(n.d.).
Retrieved
October
15,
2022,
from
https://www.sciencedirect.com/referencework/9780128012383/biomedical-sciences
[10] S. Feliu Jr. et al 2007 J. Electrochem. Soc. 154 C241
[11] X-ray photoelectron spectroscopy. (n.d.). Retrieved October 16, 2022, from
https://www.sciencedirect.com/topics/chemistry/x-ray-photoelectron-spectroscopy
[12] X-ray photoelectron spectroscopy (XPS) basic. (2019, July 19). Retrieved October 16,
2022,
from
https://www.youtube.com/watch?v=Ol3y8lhlHT0&ab_channel=TheMatSciGirlPhD
[13] Characterization methods - adsorption-desorption of gas: The bet method (Lidia
Castoldi).
(2020,
November
13).
Retrieved
October
16,
2022,
from
26
https://www.youtube.com/watch?v=3QzhBpfxLE&ab_channel=PolimiOpenKnowledge
[14] Bet theory: Anton Paar Wiki. (n.d.). Retrieved October 16, 2022, from
https://wiki.anton-paar.com/en/bettheory/#:~:text=The%20BET%20equation%20strictly%20describes,range%20of%200.
05%20to%200.35.
[15] Kajama, M. N. (2015). Hydrogen permeation using nanostructured silica membranes.
WIT Transactions on Ecology and the Environment. doi:10.2495/sdp150381
[16] Presentation29 temperature programmed reduction TPR. (2021, May 03). Retrieved
October 23, 2022, from
https://www.youtube.com/watch?v=YujRsHFWCAI&ab_channel=AyeshaAshfaq
[17] AzoHAaccnt. (2021, June 23). Temperature programmed reduction: TPR: Applications.
Retrieved October 23, 2022, from https://www.hidenanalytical.com/blog/what-istpr/#:~:text=What%20is%20TPR%3F&text=Temperature%20programmed%20reducti
on%20(TPR)%20is,oxides%20under%20varying%20thermal%20conditions.
[18] Micromeritics. (2021, April 21). AutoChem II - temperature programmed reduction with
silver oxide. Retrieved October 23, 2022, from
https://www.youtube.com/watch?v=DmWdB5cGkXw&ab_channel=Micromeritics
[19] Thermogravimetric analysis (TGA) - types, methods, materials, labs, faqs:
Aurigaresearch. (2023, October 23). Retrieved January 6, 2023, from
https://aurigaresearch.com/pharmaceutical-testing/thermogravimetric-analysis-tga/
[20] Naitchemtech1. (2016, May 20). Thermogravimetric analysis. Retrieved October 23,
2022, from
https://www.youtube.com/watch?v=itLVkpaB84Y&ab_channel=NAITChemicalTechn
ology
[21] Explain the principle or theory of differential thermal analysis (DTA) | analytical
chemistry. (2018, December 02). Retrieved October 23, 2022, from
https://www.youtube.com/watch?v=TocRAMuk7sw&ab_channel=Edmerls
27
[22] Principle of differential thermal analysis (DTA). (n.d.). Retrieved October 23, 2022,
from https://www.hitachihightech.com/global/products/science/tech/ana/thermal/descriptions/dta.html#:~:text=D
efinitions%20of%20Differential%20Thermal%20Analysis,a%20specified%20atmosph
ere%2C%20is%20programmed.&text=This%20is%20definition%20of%20DTA%20by
%20ICTAC.
[23] MaterialsScience2000. (2014, March 01). The Scanning Electron Microscope. Retrieved
October 30, 2022, from https://www.youtube.com/watch?v=GY9lfOtVfE&t=241s&ab_channel=MaterialsScience2000
[24] Professor Dave Explains. (2021, February 3). Electron Microscopy (TEM and SEM).
YouTube. Retrieved October 22, 30 C.E., from
https://www.youtube.com/watch?v=a0G7iyz4McM
[25] Fourier transform infrared spectroscopy. Fourier Transform Infrared Spectroscopy - an
overview | ScienceDirect Topics. (n.d.). Retrieved October 30, 2022, from
https://www.sciencedirect.com/topics/engineering/fourier-transform-infraredspectroscopy
[26] Mohamed, M. A., Jaafar, J., Ismail, A. F., Othman, M. H. D., & Rahman, M. A. (2017).
Fourier transform infrared (FTIR) spectroscopy. Membrane Characterization, 3–29.
https://doi.org/10.1016/b978-0-444-63776-5.00001-2
[27] Concepción, P. (2018). Application of Infrared Spectroscopy in Catalysis: Impacts on
Catalysts’ Selectivity. In
(Ed.), Infrared Spectroscopy - Principles, Advances, and
Applications. IntechOpen. https://doi.org/10.5772/intechopen.80524
[28] Wang, Y., Yao, L., Wang, Y., Wang, S., Zhao, Q., Mao, D., & Hu, C. (2018). Lowtemperature catalytic CO2 dry reforming of methane on Ni-Si/ZRO2 Catalyst. ACS
Catalysis, 8(7), 6495–6506. https://doi.org/10.1021/acscatal.8b00584
[29] Bakhtiari, K., Shahbazi Kootenaei, A., Maghsoodi, S., Azizi, S., & Tabatabaei
Ghomsheh, S. M. (2022). Synthesis of high sintering-resistant ni-modified Halloysite
based catalysts containing LA, CE, and co for dry reforming of methane. Ceramics
International, 48(24), 37394-37402. doi:10.1016/j.ceramint.2022.09.062
28
[30] Liu, W., Li, L., Zhang, X., Wang, Z., Wang, X., & Peng, H. (2018). Design of nizro2@sio2 catalyst with ultra-high sintering and coking resistance for dry reforming of
methane to prepare syngas. Journal of CO2 Utilization, 27, 297-307.
doi:10.1016/j.jcou.2018.08.003
[31] Taherian, Z., Yousefpour, M., Tajally, M., & Khoshandam, B. (2017). Catalytic
performance of samaria-promoted ni and co/SBA-15 catalysts for dry reforming of
methane. International Journal of Hydrogen Energy, 42(39), 24811-24822.
doi:10.1016/j.ijhydene.2017.08.080
[32] Rodriguez-Gomez, A., Pereñiguez, R., & Caballero, A. (2018). Understanding the
differences in catalytic performance for hydrogen production of Ni and Co supported
on mesoporous SBA-15. Catalysis Today, 307, 224-230.
doi:10.1016/j.cattod.2017.02.020
[33] Yan, X., Hu, T., Liu, P., Li, S., Zhao, B., Zhang, Q., Pan, Y. (2019). Highly efficient and
stable ni/CEO2-sio2 catalyst for dry reforming of methane: Effect of interfacial
structure of ni/CEO2 on sio2. Applied Catalysis B: Environmental, 246, 221-231.
doi:10.1016/j.apcatb.2019.01.070
[34] Das, S., Ashok, J., Bian, Z., Dewangan, N., Wai, M., Du, Y., Kawi, S. (2018). Silica–
ceria sandwiched ni core–shell catalyst for low temperature dry reforming of biogas:
Coke resistance and mechanistic insights. Applied Catalysis B: Environmental, 230,
220-236. doi:10.1016/j.apcatb.2018.02.041
[35] Rodriguez-Gomez, A., Pereñiguez, R., & Caballero, A. (2018). Understanding the
differences in catalytic performance for hydrogen production of Ni and Co supported
on mesoporous SBA-15. Catalysis Today, 307, 224-230.
doi:10.1016/j.cattod.2017.02.020
[36] Miskan, S., Setiabudi, H., Bahari, M., Vo, D. N., Abdullah, B., Jalil, A., Ismail, S.
(2023). Properties-activity correlation of nickel supported on fibrous zeolite-y for dry
reforming of methane. International Journal of Hydrogen Energy.
doi:10.1016/j.ijhydene.2022.12.201
29
[37] Liu, J., Zhang, Y., Liang, Z., Zhang, G., Wang, Y., Zhao, Y., Lv, Y. (2023). Enhancing
the dry reforming of methane over ni-co-Y/WC-AC catalyst: Influence of the different
Ni/Co ratio on the catalytic performance. Fuel, 335, 127082.
doi:10.1016/j.fuel.2022.127082
30