Partial Oxidation OF Methane
Table of Contents
5.1- Partial Oxidation of Methane to
produce hydrogen under the presence of Co, Ni & Rh catalyst
5.1.2-Monolithic catalyst- Preparation
5.3 Partial oxidation of Methane to
methanol on CeO2 nanoparticles by isolation of Pt catalyst
5.3.1-Understanding
the basics
5.4
Waste of eggshells valorization for partial oxidation of methane onto copper
catalyst
5.4.1-
Understanding the basics
5.5.1-Understanding
the basics
5.6.1-Understanding
the basics
5.7
Oxidation of methane by Microkinetic mechanism over Platinum and Rhodium
5.7.1-
Understanding the basics
5.8-Partial
oxidation of methane to methanol supported by diffusion paired copper dimers
5.8.1-Understanding
the basics
5.8.3-Reaction
Pathway to carryout the Partial oxidation of methane over the copper as active
site
5.9.1-Understanding
the basics
5.10.2-Preparation
of molybdenum methoxide:
References………………………………………………………………………………………………………………………………….55
ABSTRACT
Methane is mainly a
flammable gas and is implemented as fuel all over the world. Methane has a
chemical formula which is CH4. Methane is the gas that is of
the industrial importance, and due to this, it is used as the form of natural
gas in the houses.
In this article,
partial oxidation of Methane has been discussed. Methane is more likely to
undergo partial oxidation, but methanol cannot undergo partial oxidation.
Partial oxidation of Methane is the process which evolves heat. The major
protocol partial oxidation of Methane is of prime importance.
Partial oxidation of
Methane conducted under some catalysts, which results in the production of the
varying products. In one study, the production of hydrogen gas from some
sources includes natural gas which includes Methane commonly by the catalytic
protocol. This is expected to help in the alternation regarding cleaning
different energy systems. Recently in the previous years, the main areas of
research have been the catalyst development. Along with it, Methane and
methanol Partial oxidation on catalysts FeOx-, FeMoOx -SiO2 and MoOx- prepared
by the sol-gel process has also been studied in this article.
Another method developed for the preparation of catalyst such as
CeOer2/Pt can convert the Methane into methanol at 3000 C. Here pt is in a
dispersed form. The catalytic system improves the production of methanol by the
addition of carbon mono oxide as promotor. The double-layered upstream burner
media were having a porous structure where the packed layer has diameter 2.5mm,
and downstream layers are packed with Al2O3 pellets by designing their
diameters by testing the coated products. The molar ratio increases the efficiency
of the upstream. It downloads steam fabricated by the pellet of Al2O3 increased
the diameter 5-7.5mm by decreasing the flow rate of flame by adjusting the
temperature.
1-Introduction
Methane is mainly a chemical compound which is present in
little quantities in the atmosphere. It is the simplest hydrocarbon and is
composed up of one carbon atom and four hydrogen atoms. Being the powerful gas
of greenhouse, it is known widely. Methane is mainly a flammable gas and is
implemented as fuel all over the world. Methane has a chemical formula which
is CH4.
Methane is colorless and non-toxic and is used to make a
large variety of new compounds. In Methane, there is sp3 hybridization among
the individual atoms. Methane constitutes a tetrahedral structure.
2-
Properties of methane
Methane is the gas which is having a lot of industrial
importance. Along with it , is also used in form of natural gas at houses. Here
are some of the mentioned key points of methane regarding its properties
·
It is a colorless and odorless gas
·
Methane is highly flammable
·
It is lighter than air
·
Only soluble in water.
|
Specific gravity |
0.554 |
|
Boiling point |
-162℃ |
|
Melting Point |
-182.5℃ |
Table-2.1 Properties of Methane
3- Sources of Methane
By the anaerobic bacterial decomposition of the vegetable
matter, Methane is usually produced. In the Wetlands, Methane is produced
naturally. Along with these sources, Methane is also available in natural
sources which include termites, volcanoes, vents in some floor of oceans, and
Antarctic ice. In the natural gas, Methane is the paramount constituent having
50-90% methane. The manufacturing and the combustion of natural gas and the
coal are those sources of Methane that are linked to human.
4-Uses of methane
Methane
is the most important source to get hydrogen. Along with hydrogen some major
organic compounds are also synthesized by methane. At the high temperature or
steam methane yields carbon monoxide, and hydrogen gas. The hydrogen produced
is used in the production of ammonia, and fertilizers. Many other important
chemicals obtained from methane include methanol, chloroform and carbon
tetrachloride. In case of incomplete combustion methane produces carbon black
which is of pivotal importance in rubber industry.
5-Partial
Oxidation
It
is a chemical protocol in which limited amount of oxygen as compared to the
oxygen level which is required for complete oxidation. When oxygen level is fed
below the normal level hydrogen and carbon monoxide is formed. Methane is more
likely to undergo partial oxidation but methanol cannot undergo partial
oxidation. Partial oxidation of methane is the process which evolves heat. The
major protocol partial oxidation of methane is of prime importance.
In
case of partial oxidation of methane, it is considered as an energy efficient
process.
When methane undergoes partial oxidation it
gives a number of reaction by changing catalyst and the conditions
5.1- Partial
Oxidation of Methane to produce hydrogen under the presence of Co, Ni & Rh
catalyst
The production of hydrogen gas from some sources includes
natural gas which includes Methane commonly by the catalytic protocol. This is
expected to help in the alternation regarding cleaning different energy
systems. Recently in the previous years, the main areas of research have been
the catalyst development. Along with it, various efforts have been made
regarding determining some ideal operating conditions for fuel processing.
Methane's processing under some specific catalyst is
mainly conducted via steam distillation, partial Oxidation, and dry reforming.
In such protocols, synthesis gas which contains H2 and CO is made due to which
H2 is made. As a result of partial Oxidation of Methane about 2 mol of H2 and
36 mol, energy is produced.
Reaction1 is of the pivotal importance as a result of which CO and H2 are produced. In the reaction, two full combustions of Methane have been carried out. The third reaction, which is mainly a side reaction selectivity of Co, has been enhanced compared to H2.
In the various papers,
partial catalytic Oxidation of Methane has been studied under the different
catalyst action. Nobel metal catalyst usually has high stability and activity.
It is always preferred due to use of a low-cost catalyst in industrial purposes.
Today many other catalysts which contain noble metals. The most widely used
catalyst is Ca, Co, Ce, Pd, Ni, Y, Zr and B. These catalysts are used either in
the powder form or as the monolithic catalyst.
Nickel is mostly used
as a catalyst at present. All those catalysts that contain nickel they have
high activity. These reactions are exothermic a result in deposition of carbon
and the sintering of Ni due to the formation of coke. Various studies on Ni catalyst
in the literature shows up the decrease in the amount of coke production.
Along with this
decrease, there is an increase in activity when Co, Cr, Mg, Ca is made.
Catalyst nickel is also used sometimes with the Cu in many compositions due to
which the protocol of impregnation deposited Al2O3. They were further tested in
CH4 oxidation reactions. When the ratio of CH4 to O2 was 2.0 to 1.0, 5-%
conversion of CH4 occurred with the catalyst Ni(5%)Cu(5%)/Al2O3 at about
300degree Celsius. (Melian, 2019-3-13)
In another work
resulting from Methane's partial Oxidation, which NiO/Al2O3 catalyzes, various
catalysts were impregnated and tested for Methane's partial Oxidation.
5.1.1
Experimentation
Material
All the used reagents are of analytical value. In a
protocol nitrate salts of Co, Ni and Al (Co(NO)32.6H2O whose purity was 99%,
another type of catalyst was impregnated, having honeycomb-like features. It
was mainly referred to as M-0 in the manuscript. As a result of instrumental
analysis with x-ray diffraction and scanning electron microscopy, inductively
coupled plasma optical emission spectroscopy and Burner-Emmett-Teller, various
surface analysis protocols were implemented.
Characterization of the structure of a crystal and the
determination of crystallographic parameters of the catalyst were performed
with the aid of XRD analysis. All the respective samples were ground in an
agate mortar and then settled down in an aluminium sample holder. Then, XRD
analysis was conducted at ambient temperature by using Philips Panalytical
XPert-Pro diffractometer.
Various phases were analyzed by the help of powder
diffraction file database. After these specific structure areas of catalysts
were also characterized by implementing BET protocol under N2 gas and He
carrier at about 77k.
To identify all the metal contents in a sample, ICP-OES measurements
were performed using Perkin Elmer optima 2100DV. Few milligrams of every sample
were ground before carrying out ICP-OES reading. The sample was grounded into
powder by using a mixture of strong acids, including H3PO4, HCL, HNO3, AND HF.
The samples were further tested in a microwave digester. While carrying out
ICP-OES analysis, every sample was subdivided into three portions and by
following up some standard protocol's three specific reading were noted
down.
By field emission gun scanning electron microscopy
microstructure a d surface morphology was observed. Au covered all the
respective samples, and they were made ready for the analysis by making
fixation to the device sample.
Deposition of carbon on the catalyst was analyzed using
thermal gravimetric analysis or by Fourier transform infrared spectroscopy. In
this technique, CO2 concentration is measured up by carrying out the thermal
analysis.
5.1.2-Monolithic catalyst- Preparation
By the aid of sol-gel
impregnation monolithic catalyst having the oxides of Co, Co-Ni, Co-Ru,
Co-Ni-Ru and Ni were prepared. The preparation process as consisting of three
main steps.
The ceramic supports
were made in the cylindrical shape with a diameter of 13mm and 12mm. After the
preparation of ceramic supports, monolithic ceramic supports were coated with
alumina.
Alumina was used for coating because it enables metals to stick
easily. To carry out the coating protocol, 5M aluminium nitrate solution was
made to initiate wash coating.
5.2- Methane and methanol Partial oxidation on catalysts FeOx-, FeMoOx -SiO2 and MoOx- prepared by sol-gel process
Catalytic material such as FeOx-, FeMoOx-SiO2 and MoOx is
prepared by sol-gel method. For partial Oxidation of Methane and methanol, this
method is estimated with catalysts. The chemical nature of catalysts for gel
synthesis is being investigated at a low pH level. As a result of
characterization, the decreasing pH increases the dispersion capacity of
species such as metal oxides present in the matrix of SiO2.
The selectivity of formaldehyde in methanol and methane
partial oxidation improved by dispersing species like FeOx rather than bulk
material of Fe2 O3. Other catalysts such as FeMoOx or SiOx in dispersed form
only favour methane oxidation in formaldehyde selectivity.
Selectivty of
formaldehyde and methanol conversion
Whereas in bimetallic
catalytic process of dispersion for FeMoOx/SiOx never improves the selection of
formaldehyde for Partial Oxidation of Methane. The stimulation temperature of
Methane rises remarkably as compared to methanol. Partial Oxidation of
selective and active catalysts of Methane is the most beneficial products for
partial methanol oxidation.
Two reaction route is
followed by methanol through which processed products are promoted in the form
of a solid catalyst. Frist oxidation reaction undergo the oxygen by the
oxygen-carrying catalyst. The second one is the dehydration process which don
did not require oxygen. Dimethyl ether formation is only carried out by
bi-molecularity of methanol dehydration. Whereas the dimethyl ether formation
process is generally directly related to acidic sites presence, which can carry
out the process of dehydration.
5.2.1 Experimental view
|
|
|
Oxidation
of methanol |
Catalyst
preparation:
In the sol-gel
procedure, catalysts are prepared using iron acetate about 99%, tetraethyl
orthosilicate about 98% and ammonium molybdate tetrahydrate about 98%
precursors of iron, silicates and Molybdenum. As chelating agent oxalic acid,
about 99% is added. From Sigma Aldrich company, all the precursors are
attained. Iron molybdenum and their oxides sustained on silicon oxide, which
1.5% or 0.5% Mo+Fe prepares. The ratio of these used is 1:1. Further catalyst
is named as 1.5 Fe/Si, 0.5 Si/Fe, 1.5 Mo/Si etc. homogenous mixture is formed
by dissolving the oxalic acid in ethyl alcohol by stirring it vigorously.
Whereas on the other side,
precursors of iron and Molybdenum acquire to attain an appropriate quantity of
catalyst ratio (1.5% and 0.5%) which is dissolved in ethyl alcohol. Tetraethyl
orthosilicate is taken in another vessel. All the previous solutions are mixed
homogenously, and finally, oxalic acid, water, TEOS is added into it by the
molar ratio of 1:1:4. The sol-gel method is carried out at 300 rpm by
continuous stirring and 70o C for 7hr. Further material is dried for 12 hr. at
105o C and calcination at about 750oC for 6hr.
By adjusting the pH
level, one more catalyst is prepared by adding nitric acid in sol-gel
synthesis. Samples containing ratios 1.5 FeMo or SipH and 0.5 SipH or Fe. All
material is undergoing through the drying process at various temperatures.
Materials are calcined at 750oCfor 6hr. And dried at 105oC for 12hr. During
this sol-gel synthesis process, the direct gel is formed by adding various
metallic alkoxides such as a salt of iron oxide and TEOS at an accurate pH
medium level. Nucleophilic substitution and hydrolysis reactions take place in
this process, which measures hydrolysis and condensation at various pH levels.
When the medium is basic, collide gel formation, acidic medium polymer gel
formation occurs rapidly.
5.2.2 Tests of catalysts:
Oxidation of
Methane:
Partial Oxidation of
Methane undergoes catalytic experiments at specific atmospheric pressure in a
fixed tubular flow reactor named quartz bed. Using dilute SiC catalyst having
ratio 1:2 and about 0.05 and 0.25 g, temperature 400-650o C and feed contain
molar ratio He/CH4/O2. For the comparison purpose, the feed ratio of He/O2/CH4
is used. When all the material dried at desired requirement, we left it for
equilibrium stability of time about 45 min then further analyses. By using
thermal conductivity detector reactants and product are analyzed on gas
chromatography. Its contain two various types of chromatographic columns for
analysis.
Oxidation of
methanol:
Partial Oxidation of
methanol in catalytic experimentation is performed on quartz bed fixed in the
tubular reactor at specific atmospheric pressure, and temperature ranges are
about 200-550oC. Silicon carbide has a ratio by weight is 1:2, and mass 100mg added
to dilute the silicon carbide catalyst for preventing the ion of hot spots.
Their feed contains
almost O2/MeOH/N2 molar ratio about 81/6/13 respectively. The total flow rate
of these catalysts is 50-100ml per min. When the catalyst approaches the desired
reaction condition, we stabilize 45 min and then analyze it properly.
The analysis approach
is done on gas chromatography which has thermal conductivity detection with two
different chromatographic columns.
5.2.3 Conclusion:
pH level is controlled
in so gel procedure containing catalyst such as iron and Molybdenum, which
highly improve the disperse rate of metals on SiO2 with silica. Formation of
formaldehyde from methane increase the dispersion of metal oxide. Partial
Oxidation of methanol not required dispersion of metal oxide on the matrix of
silica. The largest selection of formaldehyde in methanol process is attained
by acidic treatment of FeOx/SiO2 catalysts. In the sol-gel method, bimetallic
catalysts such as SiOx/FeMoOx is prepared by impregnation. Methanol, as well as
methane oxidation, is achieved by catalytic selectivity and activity of
formaldehyde in different reactions. Formaldehyde stabilization on active sites
at various reactive temperature to activate methanol and Methane.
5.3
Partial oxidation of Methane to methanol on CeO2 nanoparticles by isolation of
Pt catalyst
5.3.1-Understanding the basics
The
most abundant and important component of natural gas is methane CH4. Methane
has a greater impact on the greenhouse for global warming. Carbon dioxide is
converted into common chemical and fuels, which largely increase the major
issue of polluted environment. to secure the environment from pollution, it
will first reduce the excessive greenhouse gases and find an alternate way for
methane oxidation from useful carbon dioxide. Methane is prepared from useful
resources of CO2.various methods are invented to convert methane to methyl
alcohol.
Methane
is completely oxidizing into carbon dioxide under considerable conditions of
oxidation. At the same time, partial oxidation of methane is the remaining
major issue. Methane is formed by bonding od C-H carbon-hydrogen bonding about
50 kJ/mol higher than methanol. When
methanol is produced, it’s a difficult task to recognize the selective
reactions properly.
Methane
CH4 is formed by catalytic transformation into methanol, which is a highly
challenging issue to utilize methane gas. CeO2 and Pt catalyst is used for
conversion of methane to methanol by the highly selective reaction. These
catalysts contain various ionic species like Pt+2 which is supported on
nanoparticle named as CeO2. About 6.27mmol/g yield is produced by using CeO2
catalyst having reaction selectivity 95% at temperature 300oC. Carbon monoxide
and methane are used as a reactant. Here the active efficiency of CH4 is low
without carbon mono oxide, respectively. Active interphase of lattice oxygen is
created on Pt and CeO2, which helps to convert the methane into methanol.
For
the activation of pathways various high tendency angular field scanners are
used such as x-ray microscopy of photoelectrons, transmission microscope of electrons,
x-ray absorption extended fine structures, a study of catalyst and calculation
for functional density are involved in their pathways which activate the active
methane site in the area of Pt+2 species.
5.3.2-
Experiment:
Pt/CeO2
synthesis
|
|
Implementation
of Computational Protocols |
Chemicals:
All chemicals are obtained from supplier commercially.
These chemicals are used without any purification process. All chemicals are
obtained from Sigma Aldrich company which is commercially well known because of
its pure quality. We use various chemicals for partial oxidation methane to
methanol such as pressure chemical 99% pure (K2 PtCl4) no further purification
is needed. CD3SOCD3 99.9% pure obtained from an isotope of Cambridge UK, D2 O
is 99% pure and CDCI3 also 99.9% pure. Further methanol, carbon monoxide and
anhydrous ethanol are 99.9% pure and purchased out from South Korea gas
industry.
Pt/CeO2 synthesis:
Mono dispersion shape of cerium oxide is prepared by a
hydrothermal process which dissolves a double amount of distilled water, and
it’s on the ratio is about 1.736g and 4.0mol. 70ml solution of 6M NaOH is
prepared by stirring it for 30 min. As a result, this solution is placed into a
reactor which is coated with Teflon film of the hydrothermal auto layer at
100oC for almost 24 hr. yellow colour particle appearance ruminated on the
solution which was further separated by centrifugation.
The particles separated from the mixture are washed
with water and placed several times into the oven for proper drying. The
particles placed into the oven are about 800C for 10 hours, then calcined the
particles at temperature 4000C. We measure the diameter of nanoparticle of CeO2
that is 15.2nm. after this we coated the platinum on the nanoparticle of 0.2g
which absorbed the reaming wetness on the material and implemented it with
K2PtCl4 a dilute form of an aqueous solution. The resulting catalyst is
prepared and labelled as Pt/CeO2 1 wt. %.
Catalytic experimental view:
These experiments are examined by the help of
high beam pressure reactors which have 550ml of volume. By this large volume
ratio, the heating process performs easily by controlling the temperature range
normal. Many tests are performed on the various catalyst which is stimulating
in a parr reactor with 20 mg. The gases
such as carbon mono oxide and methane are heated in a heated mantle by applying
pressure through the reactor at the specific desired temperature.
Further,
after heating the gas reactor, it is removed and placed for the cooling process
with ice cubes or ice water. Check the formation of CO2 by placed the
respective gas under the examine of GC. The liquid material is collected after
washing the prepared product with NMR solvent then observed its wavelength 1H
and 13C on spectroscopy. Methanol curves are formed gradually.
Computational methods:
The functional theory's calculations are performed
within the generalized approximation gradient, which is 35,36 GGA using
stimulation package VASP. Its wavelength is 40 and kinetic energy 500ev. The
cerium oxide contains surface modelling 110-p(2*3) which form dimensional
layers 10.920*11.58 Aston vacuum interaction of 15 Aston between periodic
pictures is restricted.
Concluded results:
The
method developed for the preparation of catalyst such as CeO2/Pt can convert
the methane into methanol at 3000 C. Here pt is in a dispersed form. The
catalytic system improves the production of methanol by the addition of carbon
mono oxide as promotor. Methane is directly converted into methanol without CO.
for activation of CH4 strong metals are supported for their interaction which
comes in contact with Pt species to enhance the reactivity of nanoparticles.
Methanol illustrated the selective oxidation of methanol.
5.4 Waste of eggshells valorization for
partial oxidation of methane onto copper catalyst
5.4.1- Understanding the basics
Major
end products are obtained by the physicochemical characterization, which may be
harnessed to equipped the agricultural wastes. Eggshells wastage is used as
precursors for the synthesis of partial oxidation of methane. The surfaces of
eggshells are calcined on copper impregnation, where almost 2% activated copper
is placed in the pathway to improve syngas production.
Hydrocarbons
are loaded 5% and 10% for oxidative methane formation. The desired temperature
6500C is applied with various atmospheric pressure. Temperature and flow rate
influenced the selective and fractional conversion of products in oxygen
concentration. Low rate oxygen affects the flow rate at 6500C. Catalyst is
loaded with Copper about 10% conversion is possible. Deformation of the surface
occurs when the fresh catalyst is stopped for uniform distribution of Cu on
smoothie catalyst. Catalytic activity is long-lasting compared to reactivated
catalyst—waste eggshells used as a catalyst in oxidation reactions.
The
most significant agriculture waste is used as precursors for end-product
synthesis, which have unique and abundant chemical and physical properties
attached to get valuable material. The basic example is the yield of eggs for
food is the most common practice for agriculture source. The worldwide
production of eggs in 2017 reported in the agricultural organization is about
81*109kg. Eggshells have about 11% of total mass available, composed of calcium
carbonate with other products with a semipermeable structural membrane. Eggs
are the most important supplement of protein for human health. eggshells have
absorbent capacity for metals and another heterogeneous catalyst beneficial for
human organs.
Eggshells
are the most important absorbing agent of absorbing heavy metals. These heavy
metals such as chromium, gold, copper and iron used for absorption of waste
products. This helps us for cleaning treatment of waste products.
Transesterification reaction takes place in eggshell production where a base
catalyst is used. Eggshell contain calcium oxide, which allows the application
of catalyst evolving oxidation of methane.
One
of the most interesting challenges for research is the partial oxidation of
methane by using various chemicals. There are many different sources of methane
availability by including digestion of solid for anaerobic liquid waste,
natural gas expanding and landfills etc. on record about 90 billion cube feet
per day methane is produced. Chemically methane is converted into in oxides,
oxygenates through catalysis. Methane has a high range of bond dissociation
energy about 440kJmol-1 connected with a structural formula with a tetrahedral
shape with sp3 hybridization. The dipole moment is absent in methane.
5.4.2-Experimental review:
|
Characterization
of catalyst |
Three concentration are prepared for the synthesis of
eggshell coated with copper as a catalyst like 2%,3% and 10% respectively by weight.
Copper has low weight, high loading and low medium. Copper chloride dehydrates
solution is prepared by the impregnation process. Particles of eggshells have
2-5 mm in size mixed with copper chloride dehydrate solution at 300 room
temperature for 5hr. Heating the mixture at 1050C for about 8hr and activated
the whole mixture at 10000C for 4hr.
Characterization
of catalyst:
Variable pressure scanning electron microscopy (VPSEM)
characterizes the catalyst and secondary time flight of ion spectroscopy. The
catalyst's surface is coated with gold 35nm or 60% and 40% palladium for sample
preparation. The equipped instruments are used for studying the surface of the
sample with the metal gun having angle 450 which normalized the surface area of
the sample by applying pressure on the inside chambers about 5.0*10-9.
Testing of
catalyst:
The
tubular reactor has stainless steel which resists various temperature. The
tubular reactor has a diameter of 2.5-15cm in height. In every experiment, the
reactor is coated with 10g of catalyst—about 99% of the flow rate required for
high oxygen and methane purity. The molar ratio of methane and oxygen is
CH4:O2, respectively. For activation of catalyst in an experiment about 650oC
temperature for 1hr in acquired. Gas samples from the reactor are collected
after 10 and 15 min interval to maintain equilibrium. Gas samples are examined
under the gas chromatography for detection of thermal conductivity with mass
spectrometry.
Life
of catalyst:
Four
types of cycles are obtained from catalytic residue. Conversion of methane
increases rapidly in a third operational cycle through which the gas flow on
the catalytic surface is disrupted. Catalytic bed increases the activation
sites for conversion of methane. Hydrocarbons C2-C6, as well as carbon oxides,
are observed in the operational cycle expect the ethane.
End
results:
For partial oxidation of methane synthesis, calcium
oxide is used as a catalyst by copper coating, and chicken eggshells are
valorized. Syngas is produced on eggshells by low copper concentration. Higher
the hydrocarbon synthesis increases the copper loading, which reduced the
conversion of methane according to required properties.
The surface of eggshells may have a various coating of
metal such as copper. Actives produced oxygenated material such as CaO and CuO,
which have higher hydrocarbon orders. It is mainly originated from the CaO
phase. The temperature did not affect the selectivity and productivity of
methane and oxygen. Only water and methane is not evolved in this process.
There are four
operational cycles of conversion examine for the incensement of active sites
rapidly. Hydrocarbons are evolved in the selective production of methane
oxidation in future research to maximize the selection rate. Eggshell is
impregnated as the catalyst for support of metal.
5.5 Partial oxidation of methane to methanol
by the implementation of Iron and Copper Zeolite Exchange
5.5.1-Understanding the basics
In the form of natural gas, we can obtain a vast
amount of methane. Methane can be
implemented in the case of petroleum fractions. One of the product obtained is
methanol, and it is mainly used as the most important component of the
petroleum industry. In the methane, the C-H bond is broken down by the help of
the partial oxidation. In out to carry out the protocol, those types of
catalyst can help prevent the over oxidation of methane gas into the other
form, which is obtained by converting into carbon dioxide. The high scenario of
selectivity arises due to some reasons regarding the bond energy of C-H.
The conversion of methane into methanol takes place
via the catalyst. This protocol is accompanied into two steps. One of them is
the protocol of high-temperature steam reformation into the synthetic gas.
After this, another subsequent protocol is followed up by the action of
Copper-based catalyst. This type of protocol is implemented to obtain large
scale production of the desired product.
One of the protein monooxygenases is implemented to
convert methane along with oxygen and the other product, which is methanol that
is having high selectivity. Today, all the protocols used for the methane's
partial oxidation have focused on the formation of Iron and Copper- oxygen
species present in those respective biological systems.
The activation of catalyst is one of the most
promising one such as C-H and Fe, and Cu zeolites contain active site keys
which undergo the selective oxidation of methane CH4 to CH3OH. In partial
oxidation of methane oxygen act as an oxidant for Cu exchange zeolites. There
are various systems of implementation, such as Shilov system and Perianal
system.
Zeolites
are based on advanced technologies with multifunctional reactors, numerous
measuring challenges, and high rate of pressure systems that give a large
number of methanol production while inhibiting the excess of oxidation rate.
Here basically describe the isolation sites and strength of ligand field by
sharing the same attributes with various metalloenzymes. Our main focus is on
the present comprehensive review of partial methane oxidation felid.
MMOs is an overview of transporting
mechanism by protecting methanol's oxidation and its selectivity towards the
future. The ability to generate active oxygen by an artificial method is so
critical at active sites of metal. The selective oxidation also undergoes in
this method. In catalytic MMOs, cycle product is soluble rapidly. In MMO method
Q form intermediate with P which complex di-iron peroxo bridge positioned at
cis-1,2 by transferring of the proton through cleavage process of O-O bond. Two
Fe atoms combine to form Fe II when P is transferred, the connection of O2 on
binding sites convert the species. Active site available for Fe and Cu based
zeolites and enzymes show partial oxidation states of methane.
Methanol
is attained in the cyclic processes where partial oxidation of methane occurs
on Fe exchange zeolite ion having specific actives sites at high-temperature
523k by activating NO2 towards OH species. The specie OH reduce the active site
tendency at low temperature or even at room temperature. So that’s why methanol
is obtained from water. Here water is bounded to the surface of methanol which
localized the acidic sites. The mild temperature never demonstrates the
molecular O2 activation with Fe. Zeolite ion within Fe prevents the methanol
oxidation into formic acid. Carbon dioxide properly balances the tendency of
products according to requirement.
O2
is used as an oxidant in experimental precautions where the chemical looping
cycle has a high capacity of selectivity of methanol. The oxidation steps are
introducing by expelling out the O2 oxidant over Cu zeolites.
Over
oxidation creates many problems in the looping process due to the large number
of molecular concentrations such as O2 and CH4. Methane to methanol conversion
at low concentrations forms gaseous O2 under the flow rate of CH4 and H2O. Due
to the extreme concentration of dilute O2 Cu oxidation takes place, which
demonstrates the thermodynamic principles. The formation of CH3OH variates the
rate of O2 concentration. O2 properly oxidises on the active catalytic sites,
reducing the excess presence of oxygen for the combustion reaction.
5.6 Partial oxidation of methane with Al2O3
pellets in two layered burner having porous media of various diameters
5.6.1-Understanding the basics
Combustion of methane takes place in a two-layered
porous burner with different diameters with Al2O3 pellets experimentally for
fuel-rich study. The upper layer of the Al2O3 pellet consists of 2.5nm
diameter, whereas the downside layer contains different types of pellets with
diameter 5, 6.5, 7.5 and 9.5nm. Distribution of temperature, exhausting of
combustion and conversion of energy is analyzed at fixed operational parameters
with the ratio of 1:6 and having velocity about 0.13 m/s. The downward pellet
determines the oxidation of methane having a diameter of 7.5nm with frequent
energy conversion. Finally, methane is converted into CO and H2 with equal
ratio 1:7 and measuring velocity 0.15m/s, respectively.
Natural gases direct-fed into the system for
processing of fuel and reforming natural gas method. It is n endothermic
process which needs a high amount of heat to fulfil the reaction requirements.
While increasing the reforming capacity of the system, the complexity among the
process increases from small scale.
Partial oxidation of methane is an exothermic process that starts simply
and gives fast dynamic response without any external heat and pressure. An
alternative parameter for partial oxidation of methane is fuel-rich combustion
method processed in porous burners media with various diameters.
Fuel rich combustion having porous burner media which
is categorized in two steps;
·
Filtration combustion
·
Stationary combustion
In
filtration combustion the process undergoes within the porous media where
transient zone present. Flame is download located for streaming, gas released
and heat evolved through the flame. Focused on this preheating process until
the partial oxidation of methane take place from single layered porous media.
Almost 62% of methane gas is converted in syngas. Syngas is basically the
formation of heavy fuel oils such as butane, ethanol, methanol, diesel etc.
which is studied in fuel rich combustion method.
In
stationary combustion porous media which is two-layered, it supports the
stationary burner zone area. This is at the interface of the two layers which
are being used. One of the layers is the downstream layer which usually has
high porosity, and it further supports the combustion protocol. The fuel-lean
combustion of the methane is a two-layered. Various researchers have studied
the combustion of methane over a wide of equivalence ratios. Almost 45% of the
methane was converted into the syngas at a ratio of almost 1.85 Production of
syngas from fuels was also studied in further research. Various workers have
utilized a two-layered porous media burner for the partial oxidation of
methane. Further, a porous media burner was made that was having a conical
flask.
In
another study, the partial oxidation of methane was also studied along with the
biogas in a two-layer porous media burner. Subsequently, the porous media was
developed, and it was further used to supply syngas. Both the ceramic and
packed Al2O3 pellets were used in the protocol in the form of porous media. But
current studies mainly focus on high fuel combustion in the packed Al2O3 beds
with a fixed diameter. Various recent
experimental protocols evaluated the outcomes of pellet diameter on the
fuel-rich combustion.
5.6.2-Experimental analysis:
Media
burner in porous form has a two-layered measurement system for gas supply.
Burner chambers regulate the flow of air methane. The flashback system is
attached to control the mass flow of air into the chambers. Sand is filled into
the chamber about 1-2nm in diameter to prevent the fire flashback. Stainless
steel covered on the tube having 54mm diameter and 200mm long. Burner having
porous media which consist of double-layered Al2O3 pellet. This pellet is 2.5
mm filled and 20mm long. The combustion samples are sampling out for
measurement in the GC chromatography and thermal conductivity detector.
S-type
means seven type thermocouples are spaced apart by labelling them T1, T2, T3,
T4, T5, T6, and T7 in both upward and download stream. The temperature changing
measure properly and recorded sampling temperature by connecting to a computer.
The burner exhausted the combustion out through samples by measuring gas
chromatograph.
The
downstream layers have different diameters like 5, 6.5, 7.5 and 9mm and pellet
comprised the long pellet of 60mm at the packed bed of the Al2O3.
5.6.3-Equation parameters:
5.6.4-Protocol
Firstly,
methane/air mixture is taken at equivalent ratio and velocity 0.8 and 0.15m/m
respectively. Burner outlet has a blue colour surface which propagated flame is
used for heating the porous burner media. The flame is double layered where the
temperature is approaching the thermo-layer and the flow of gas regulated in
rich-fuel combustion.
The
equivalent ratio and velocity are 1.6 and 0.15m/s, respectively. The release of
heating occurs through the methane and air mixture, which decreased the equal
ratio of velocity. The flame is moving upward and downloads direction to
determine the increments for stabilization of velocity and equivalent ratio.
The thermocouples varied 10-20k for flame stability.
When
the flame becomes stable, the samples are exhaust out through the burner outlet
measured by GC. Various methods carry out this method.
Concluded result:
The
double-layered upstream burner media were having a porous structure where the
packed layer has diameter 2.5mm, and downstream layers are packed with Al2O3
pellets by designing their diameters by testing the coated products. The molar
ratio increases the efficiency of the upstream. It downloads steam fabricated
by the pellet of Al2O3 increased the diameter 5-7.5mm by decreasing the flow
rate of flame by adjusting the temperature.
The
conversion of energy efficiency decreases the gas mixing by incomplete
conversion of methane. The partial oxidation of methane packed the optimistic
pellet for syngas have a high energy level. The molar fraction increased by
raising the velocity and ratio equivalence of H2 and CO, giving experimental
conditions. The energy efficiency is 11.9%
and 9.9% for optimizing the burner. The fuel-rich methane combustion has
two-layered porous burner media for syngas conversion.
5.7 Oxidation of methane by Microkinetic mechanism over
Platinum and Rhodium
5.7.1- Understanding the basics
Methane is remarkably obtained through natural gas,
which provides a green colour pathway for the synthesis of fuel in alkene and
alcohols. The hydrogen is demanding majorly in this method which helps us
reverse Sabatier reduction, which gives a noble prize in 1912.
The partial catalytic oxidation of the methane gas
proposed alternative reforming steam, which gives many benefits over the steam
reforming. H2 and CO ratio save energy for the synthesis of tropsch-fisher.
Different catalytic material for methane oxidation, including metal catalyst
which gives thermodynamic aspects to ruined the process.
Dry methane reforming used the basic carbon dioxide
instead of hydrogen for partial oxidation of methane. For this purpose, the
microkinetic models approach to successful validity of hydrogen on the platinum
combustion. This work extended on the various pathways such:
·
Rhodium based catalysis to investigate for
CH4/O2/Rh system
·
CPO of methane for O2/CH4/Rh system
·
Accurate density functional theory for
potential inclusion on data based partial updates
5.7.2-Selection of
data
On Methane's combustion, all the recent literature
review over Platinum involves various studies regarding the stagnation, which
focuses on H2 Co-feed, which act as an additive in Hydrogen and oxygen
combustion. All the conducted studies that involve the confirmation of Methane,
Platinum, and oxygen protocols studied all the fuel mixtures' ignition process
by the various calculation in a parabolic and elliptical way. All the recent
experimentation which involve the study of the methane gas got converted under
the catalyst Platinum supported by alumina and zirconic supports. Weng also put
an investigation regarding the activation of the methane gas under the catalyst
palladium and Platinum. All the previous experimentation while dealing with
methane activation showed that this strategy is well suited for creating
heterogeneous catalysts.
In some of the processes, the Rhodium catalyst was
also implemented. It is due to the following reasons:
- Rhodium shows the best
performance and activity in CPO of methane gas
- Rhodium is the element of the
transition metals, and it contains the different number of electrons in
its outermost shell.
- All the experimental techniques
were applicable under the availability of both catalyst Platinum and
rhodium.
All
the literature regarding the use of rhodium based catalyst reforming is
updated, and the vast amount of data is made available. Enger has reviewed all
the previous literature regarding work on the partial oxidation of methane and
all the data regarding dry reforming has been collected by Drift. Partial
oxidation of methane under the implication of hydrogen and oxygen as a catalyst
results in syngas formation. This protocol was designed from the stagnation
flow. It was further confirmed by experimental data sets which made the
catalyst stability sure. All the recent studies today involve studying the
energetics of Carbon monoxide and the various other oxygenated compounds.
All
the experimental datasets that were chosen show confirmation of Platinum's
treatment and rhodium catalyst in a high-pressure chamber. This data set of
Platinum includes almost five cases. Two of them are regarding methane
specifically.
5.7.3-Computational Protocols
Computational
analysis was carried out by the implementation of two dimensional boundary
layer whose route was chosen to be parabolic having followed up all the laws of
conservation of mass, momentum. Any of the specie which is present in the
gaseous form its energy is characterized with the aid of its enthalpy. To carry
out the computational analysis three main domains need to be covered.
Gas phase
Chemistry
To carry out this specific study, a subset of two
gases has been used by Lindstedt and Waldheim's mechanism. Some adjustments
have been made regarding the modification of the Hydrogen and oxygen gas sub
mechanisms and the preselected rates. The recent studies on H2/O2 chemistry
bother The strategy of Burke,
The result of all the updated gas-phase chemical
techniques is checked out while considering the system's sensitivity. In this
protocol, almost forty-four gases have been analyzed along with almost 270
reversible reactions. The computational techniques analyzed all those selected
gases.
Surface
Chemistry of the catalyst Platinum
On the basics of the reaction of Vincent, two of the
surface mechanisms have been used in contrast to VTST- based protocol. The
makeup of the C2 surface species is not as much supported in all the recent
study
Surface Chemistry
of the catalyst Rhodium
Two protocols regarding the rhodium have been devised
in this recent work. First of them is mainly a protocol derived systematically,
which is based on VTST analysis and the heterogeneous mechanism, which was made
by the Pt-based techniques. This strategy is mainly straightforward and depends
on the UBI-QEP protocol to sort out all the energy obstacles.
The rate of activity and speed of this reaction is
analyzed by the formulation of a hybrid where all the obstacles regarding
energy are solved. All the comparison is made on the base of collision theory
which was put forwarded by Vincent. When the catalyst is changed from Platinum
to Rhodium, all the reaction rate parameters are also altered. In general, the
overall protocol is very comprehension, and almost thirty-five adsorbed species
are involved along with 284 reactions that can revert. After following up the
proper strategy, all the thermodynamic parameters were checked out, and the
rate of reaction was also computed again for the catalyst Rhodium.
Parameters to judge the rate of Exponent
By the use of the systematic protocol, the
pre-exponential factors were calculated in the recent study. In this study, the
transition state was localized by Kraus and Lindstedt with the VTST approach's
help. All the data experimentation regarding the vibrations and the moment of
inertia was also calculated.
Activation Energy
By
using the UBI-QEP protocol, all the activation energies were calculated in the
rhodium based mechanism. All the reading the heat of adsorption was also
calculated by understanding the literature data and the sensitivity inspection.
The final bond energies were also calculated for all the gas-phase species.
In
the table, all the recent values have been calculated.
|
Species |
Heat
of Adsorption |
Total
Bond energy |
Mode
of adsorption |
Reviews |
|
H(solid) |
400 |
- |
H |
Made
adjustment form 314kJpermol |
|
H2 (solid) |
152 |
430 |
H-H |
It
was calculated form O2 literature |
|
O
(solid) |
501 |
- |
O |
|
|
C (solid) |
582 |
-C |
|
|
|
CH4 |
25 |
1666 |
- |
Literature |
|
C2 |
70 |
608 |
C=C |
Almost
351kJpermol |
|
CH3OH |
188 |
2038 |
O |
|
|
CH3O |
290 |
1602 |
O-
Very strong |
350Kj/mol |
|
CO2 |
71 |
1607 |
- |
|
|
CO |
165 |
1075 |
C-
medium |
|
When
we plot it in the form of a summary in the form of the potential energies to
carry out the partial oxidation of the methane gas under the catalyst rhodium's
action, various new facts and figures, have been elaborated. Presently, Pilot
put an investigation to convert syngas into ethane or ethanol. To carry out
this conversion on the rhodium surfaces, various hydrogenation reactions were
conducted consecutively.
By
taking into account all the calculations obtained from the hybrid mechanism,
this approach is used to carry out the partial refinement of UBI-QEP based
protocols. As a result of all the conducted studies, it was made clear that the
early transition values were usually very high compared to the breakage of the
oxygen bond.
When
we studied the literature, it was obvious that the adsorption of all the carbon
species on the surface of the rhodium is available for almost those atoms with
six to ten carbon atoms. Still, it was equally applicable to methane too.
The
binding energy of all the side carbon atoms has been reported as about 221Kj/,
mol. The adsorption of carbon monoxide is also being studied. Various
experimentation analysis carried out by Baraldi and Dulaurent showed that there
is desorption of about 140 kJ/mol energy.
Rojo
further studied the adsorption of hydrogen on the experimental way and proposed
about 40kj/mol value. This value is per the advice put forward by Sacardaonkar.
5.7.4-Discussion
Combustion of
methane over the catalyst Platinum
All
the results that were obtained by the combustion of methane gas over the
platinum by the use of VTST protocol of Kraus and Lindstedt is shown in the
figures too.
All the results of the above discussed
protocol has been shown
Partial
Oxidation of methane under the catalyst Platinum
All
the results for the partial oxidation of methane have been calculated based on
the VTST protocol of Kraus and Lindstedt. In the study, all the estimated mole
fraction of methane and oxygen gas are following about two mole % at all the
downstream stations.
All
the results that the Vincent obtained have been elaborated well. All the
fraction of the mole for methane, hydrogen gas, and oxygen follows the VTST
protocol, but carbon monoxide is showing a very poor agreement. This is because
the protocols fail to capture carbon monoxide's makeup at the surface of the
catalyst.
Gas phase
chemistry and its outcome
The
results obtained by the Linstedt and Skevis were different from the Linstendt
and Waldheim. The outcome for methane conversion has been shown
This
all mechanism is followed up in a series of reactions as described by Lindstedt and Waldheim.
Conclusion
Partial
oxidation of methane has been studied under the platinum catalyst. It has been
noted that the application of VTST with an amalgam of UBI-QEP to check out the
determination of all the energy obstacles which can equal or exceed all the
values obtained by various calculations. At present, the VTST technique is the
best way to eliminate all the difficulties linked with the lack of primary
data.
Further,
regarding the gas-phase chemistry, all the major aspects are of the significant
value. To carry out this technique, a sensitivity protocol is implemented due
to a strong mix-up of heterogeneous chemistry. It is also observed that the
increased rate shows a better agreement with all the respective data obtained
by the experimentation.
To
provide easiness, the mechanism for the reaction of rhodium was developed by
implementing a proper strategy along with the varying conditions compared to
platinum catalyst usage. The notes heat of adsorption was noted from the
literature, and it was tested for the sensitivity analysis. It was also checked
out that uncertainties were retained while making calculations in case of some
specific species. Data were also collected for all the observed energy
obstacles to providing the best approach: the hybrid protocol forwarded.
For
all the respective mixtures of the fuels, the VTST analysis was done. Following
up all the terms and conditions which were CPO, the VTST protocol showed a good
agreement lower to 52mm downstream along with the conditions. The only
exceptional case is for carbon monoxide. This framework served as the basics to
deal with all the sensory pathways.
5.8-Partial oxidation of methane to methanol supported by
diffusion paired copper dimers
5.8.1-Understanding
the basics
The
selective oxidation of methane to some specific chemicals is a good challenge
in the industry. Various protocols in the industry are being used to upgrade
methane to various petrochemical precursors that need a specific high
temperature, and they are needed on a large scale. Today the enhancing need for
natural gas in some remote environs focuses on establishing small scale CH4
conversion protocols in the mild conditions. Iron, along with the copper, is
used to convert initial methane methanol directly at some specific conditions.
Like
some biological systems, many metal clusters are also used along with the
single metal atoms like ferric, Copper, Rhodium, and palladium. Copper zeolites
are of the primary importance in all this scenario. Copper zeolites usually
activate the methane by implementing the molecular form of oxygen as the only
available oxidant.
All
the protocols involving copper zeolites are performed in a cyclic,
stoichiometric manner with the mandatory catalyst, which requires
high-temperature requirements. In a recent work gas-phase conversion of methane
to methanol was performed under the appropriate catalyst. Copper zeolites'
usage to make methanol by using just methane, water, and oxygen gas is of
pivotal importance. This protocol has enhanced selectivity within a wide range
of zeolite topology.
It
is quite evident that the catalytic conversions offer significant advantages
along with providing us with the continuous supply of methanol throughout the
reaction. When we look at the nature of the active site, it is not known in
detail still. Many similarities are present in the stoichiometric and catalytic
protocols. It is understood that the active site of some specific
stoichiometric oxidation systems is very closely linked with the active site in
the catalytic protocol.
Some
notable turning points regarding the activity and tolerance of water in the
Copper zeolite exchange's active sites compared with catalytic oxidation
reaction conditions gives an idea that active sites are varying in these two
protocols. So while conducting this study for the first time, various details
regarding kinetics and active sites of Copper zeolites exchange have been
studied.
5.8.2-Composition of
Zeolites
5.8.3-Reaction
Pathway to carryout the Partial oxidation of methane over the copper as active
site
To make sure the
direct conversion of methane into the methanol investigation of the active site
is needed. Various synthetic protocols have been used to make a suit of the
catalyst with different Copper content and the Aluminum speciation.
Catalysts termed as
Copper-CHA is the copper exchanged catalysts. Reaction rates of such catalysts
need to be monitored. All the reaction conditions are also checked out to make
methanol along with the carbon dioxide. In this protocol, about 95% selectivity
to methanol can be obtained by the reaction condition and the respective
catalyst's choice. The staring order deploy was designed by contact-time
kinetic research of the representative cycle. Before the downstream oxidation
of methane to carbon dioxide, it also got converted into methanol by the aid of
partial oxidation.
C-H activation's
total rate was also checked out by the weight of carbon summed up to the total
weight. The partial pressure of water inhibited C-H's total activation rate,
and the partial oxidation of selectivity lowered down by decreasing water
partial pressure. All the noted results regarding the reaction pathway where
the rate analyzing C-H scission were catalyzed with copper and oxygen
catalysts. This process occurs in a variety of ways
- Methanol desorption which is
aided by water
- Secondary oxidation of a C1
precursor to carbon dioxide.
All the previous
literature has shown that water lowers the desorption energy of all those
species attached to the surface of many methoxy species to make methanol as the
desired product. Decrease partial pressure of water lowers the probability of
all the events involved in the desorption of methanol, resulting in carbon
interaction with the oxygen.
5.9-Nickel and
Silicon dioxide preparation for the partial oxidation of methane
5.9.1-Understanding
the basics
Today,
Nickel-based catalysts have been used and have attracted the attention mainly
due to Nickel's vast reserves. Nickel is available all over the market due to
the low cost, and it has a good catalytic performance compared to other
catalysts that are implemented for this purpose. Nickel-based catalyst is
believed to be the most appropriate catalyst that is used in the industrial
protocols. It is also observed that Nickel's catalytic performance is very
closely linked to many other parameters involving the protocol of preparation
and the active phase precursor used.
Today a vast
literature is available to give reasons why Nickel-based catalyst needs to be
used today. Support plays a pivotal role to check out the activity of any
Nickel-based catalysts. In general, a high surface area support is very
mandatory because it is very efficient to enhance the nickel dispersion and
increase its thermal stability. It helps yo enhance the active catalytic sites
and lower the deactivation of the catalyst due to one reason or the other
reason.
Due to the good
thermal stability and the relatively high specific surface area, silicon
dioxide support is mostly used to make any catalyst that is Nickel-based. The
choice of the precursor salt is also very crucial to check out that either the
Nickel-based catalyst can bee prepared easily or not. For an efficient
catalyst, two terms need to be meant.
- Higher solubility
- The ability of decomposition in
calcination
Because of the low
cost along with the enhanced solubility in the water nickel nitrate is used in
the makeup of nickel-based catalyst
5.9.2-Experimentation
Preparation of the catalyst
In this process, the Nickel catalyst supported by
silicon dioxide has been made by IWI by the use of nickel nitrate as a
precursor. Before using silicon dioxide, it was first treated with 5%HNO3 in
the aqueous solution, and it was retained there for about 48h. After this, it
was washed out with the help of deionized water. The size requirement of
silicon dioxide was set to about 60 to 80 mesh. After this, it was impregnated
with nickel nitrate's aqueous solution, and a sample was left to dry overnight.
Catalytic reaction
The reaction was carried out mainly in a fluidized-bed
reactor with a quartz tube under the atmospheric pressure of 700 degrees
Celsius. Before the startup of the reaction 2Ml of the respective catalyst was
reduced at about 700 degrees Celsius for about 1 hour under the flow of
hydrogen gas. Gas steam of the reactants with methane, carbon dioxide and
oxygen was added up in a specific molar ratio. With the help of the mass flow
controllers, the added gas was monitored. With the help of an online gas
chromatograph, the effluent gas was checked out that was added in a specific
column along with the conductivity detector. In all of the cases, the oxygen
gas was being used up totally.
Characterization of the catalyst
- FTIR spectra were measured by
the usage of Nicolet 560 spectrometer that was equipped with an MCT
detector. Thermogravimetric analysis was conducted under the supply of
oxygen gas. UV Raman spectra were also conducted with the Jobin Yvon
LabRam-HR800 equipment.
- The catalyst was also analyzed
by the help of an X-ray powder diffraction pattern of the samples obtained
with an automated device. By the usage of Copper radiation, the analysis
was carried out at about 40Kv AND 300Ma. All the samples reduced
previously at about 700-degree Celcius for almost 60 minutes were cooled
down to the room temperature to carry out further protocol. After cooling
the samples were ground into a fine powder for further measurements.
Characterization
of the catalyst
|
3- |
5.9.3-Discussion:
The performance of NI/SIO2 shows rapid action of
detected the deactivated NiSN, which covert the CH4 during 1.5 hr. reaction of
steaming. It decreased by an average of about 58% to 25%. The basic cause of
deactivation that to 3NiSN used as a catalyst characterized by NMR, XRD,
UV-Raman, IR and, DTA etc.
Thermal
Analysis
To conduct the study
of the formation of NIO from the precursor, thermal analysis is carried out
before calcination. The additional water was removed by holding the precursor
under O2 at about 110 degree Celsius. Thermal degradation of 3NiSN was dried
for the oxidation of partial methane which consists of two steps.
- Frist in TG region weight is losses about 9.1% at
110-2400C temperature by showing the curves and peak around 2240C due to
dehydration of 3SiN.
·
Secondly the large loss of weight region 11.1% at 240-3800C in
TG by appearing the small endothermic peaks in DTA at 2930C for their oxidative
degradation of nickel nitrate.
This
type of degradation shows various peaks by variation in temperature, such as
above 3800C the curve behavior never shows its appearance. Whereas water and
nitrate, curves show their absolute validity and the production of nickel
oxides over a coated catalyst at 380-degree temperature. The calcination method
on this temperature shows the strong interaction of SiO2 and NiO.
UV-Raman
Studies:
The spectral behaviour appears in the UV-Raman study.
The catalyst 3SiN give crystalline structure which has Sharpe peeks around
22-degree in silica-supported media. Other samples show various peak
appearances like III,200and 220 planes have angles 37, 43 and 63 degrees. After
the reduction of hydrogen gas, the metallic NiO transformation is detected.
TEM-
investigation:
The Ni particles aggregate over the catalyst 3NiS show
TEM analysis. Deactivation and reduction process is exhibited in their images.
Both catalysts collaborate with Ni to form spherical shapes of particles. The
dispersion of Ni particles properly detected NiSiO2 after reduction method.
Distribution of particle size obtained by TEM for reduction and deactivation,
respectively. The catalyst reduced their values from the average range of 16.1-84nm
with a size range of 37.5nm. By the NiSO2 deactivation, the size of the
particle increases 50.4nm.
Particle size effect the Ni:
The size variation matters a lot for
the formation of any chemical process. It critically affects the nature of the
molecule by adjusting the average range parameter. Ni's metallic size plays an
important role in the catalytic reaction formation because of the variation of
size; the activity of Ni reflects negative behaviour on the reaction. The size
of the particle directly links with the activation of the active catalytic
sites. In catalytic reaction, the particle size depends upon the 3NiSiO.
For all of the 3NiSN, only nickel and the
amorphous form of silicon dioxide phase was detected by XRD. There was a lack
of any NiO phase, which showed no significant alternation in the Ni phase even
after the deactivation process. As the reaction time increases the intensity of
diffraction of crystalline nickel also increased. The crystalline size of
nickel was also noted down. The changing trend of Ni size was in conformance
with the catalytic activity of 3NiSN catalyst.
By the analysis of the characterization of
all the results, all important information has been conducted. On one side, the
graphic carbon was not analyzed in the spent all the 3NiSN catalyst with XRD
and TEM aid, which suggested that there was no accumulation of carbon. While on
the other side except for the characterization of XRD peaks of metallic nickel,
no other nickel species were noted.
5.9.4-Conclusion
In this study, Ni/SiO2 catalysts were analyzed with
nickel nitrate that acted as a precursor with IWI protocol and was
characterized by FTIR, TG-DTA and some others. As a result of calcination at
about 380 degree Celsius water and the nitrate was volatilized absolutely to
make NiO which can also be reduced in the form of the metallic nickel after the
treatment H2 700-degree Celcius. All the active nickel particles of 3NiSN
catalyst were scattered and had a weak interaction with SiO2 support. Further, this weak linkage was dispersed
after the repetition of oxidation-reduction-oxidation in the respective
fluidized bed reactor.
5.10- Partial oxidation of methane
gas by the nitrous oxide supported with molybdenum over silica
Understanding the
basics
The partial oxidation of methane gas is the
most challenging problem in case of the heterogonous catalysis. When the
molybdenum is supported on silica, it is a very effective catalyst for
converting methanol to methanol and then methanol into formaldehyde. In the EPR
spectroscopy case, we have checked out that dinitrogen oxide acts with the
surface of molybdenum ions, and in the end, oxide ions are made. As a result of
the reaction, the hydrogen ions are removed from methane, and CH3 Radicals are
formed. The methyl radicals then react with molybdenum oxide, and methoxide
ions are formed. Formaldehyde can be made by the accumulation of methoxide and
as the desired product of methanol oxidation.
In
this study, the kinetic data has been provided to elaborate on how selective is
the oxidation of methane. Further, regarding the support of selective
mechanism, spectroscopic evidence has been put forward too.
5.10.1-Experimentation:
Experiment
with catalysis:
In
this study, methane N2O, CO have been used to show the purity level no
additional protocol should be applied to check out the purification. The
molybdenum oxide catalyst was made by adding 16g of Cab-O-Sil which was having
0.51g of ammonium hepta-molybdate. Before the addition of cab-O.Sil the ph od
solution retained to 11 by the addition of NH4OH. This slurry was mixed up in
the Rota vapour for 120 min. The catalytic experiments were conducted in a
fixed bed reactor working on the total pressure of about 1 atm. The reactor had
fused quartz tube which was the link with the capillary quartz tubing so that
methanol and formaldehyde can be discharged from the heating sector. In this
experiment, the reaction consisted of 1g of a catalyst having a typical volume
of 4ml. The bed of quartz chip that was 50mm deep was also localized on the top
of catalyst to prevent the initial heating of reactants.
All
the catalyst was then pretreated in the reactor for about 60min by reducing the
pressure by keeping the temperature that was 50 degrees. After this step, the
temperature was reduced to 400-degree. By the end of this experiment, all the
gases were analyzed to expect formaldehyde examined by the gas chromatography
protocol—formaldehyde further checkout by iodometric titration. By the use of satisfactory precipitation,
about 90% carbon mass was noted.
Spectroscopic
protocol:
Alternation in molybdenum concentration concerning NO2
andCH4 partial pressure was analyzed by 150 degrees by the aid of EPR
spectroscopy. In this experiment, the reactor was having a fused quartz U-tube
along with the sidearm. Activation of catalytic samples was made sure. After a
specific period, the gases were evacuated at room temperature, and the catalyst
was transferred in the sidearm for the analysis named as EPR. On the Cab-O-Sil
silica, experiments were conducted to
check out the surface methoxide ion.
The catalyst after drawing the solid was calcined at
about 60 degrees for about 24 hrs. In all the EPR powdered samples' experiment,
and then converted in the quartz sidearm to record the spectrum. The spectrum
of EPR was recorded at -1 degree. The G values, along with the concentration of
spin, were analyzed by using phosphorus-doped silicon standard.
5.10.2-Preparation of
molybdenum methoxide:
The
reaction of modelling compound is studied with water by the addition of
molybdenum methoxide to form MoOCl4. The synthesis of this lattice compound was
described by the refluxing action of MoO3 and SOCL2. 0.58G OG Na metal is added
in the nitrous atmosphere to slow down the anhydrous methanol for 10 min. Sodium
reacted to make a soluble methoxide by adding crystal MoOCl4, which was added
slowly into the solution in a concentration of about 1.60 grams. Then we'll
filter out all the NaCl sediments, which was having orange colour filtrate
placed into the oven for dryness. In the end, the orange colour solid obtained.
Through the elemental analysis the ratio of solid Mo:C: H was 8.9:3.8:1.0 It
was comparatively having a theoretical yield from MoO(OCH3)4 8.0: 4.0: 1.0
The
reasonable size obtained by x-ray diffraction was unsuccessful so that why
under the vacuum condition the compound is decomposed before it undergoes
sublimation.
5.10.3- Results:
Kinetic
Experiment
Methane
is converted into various products in a specific contact time W/F. W is the
catalyst's mass, and F repr4sent the flow rate of catalyst at room temperature.
The mass of catalyst is changed by the experimental value of W/F, which hold
the flow rate constant. The methane is converted properly 1% under the
examination of catalyst MoSiO2. The partial oxidation of methane has various
selectivity amounts such as CH3OH, HCHO in a short ti,e interval. This time
duration enhances by the addition of secondary products like carbon dioxide and
carbon monoxide. Carbon dioxide is strongly Favourable product for the partial
oxidation of methane as compared to carbon monoxide. Carbon monoxide appears as
the most practical problem of selectivity fo the remaining gases used as a
fuel. The reaction rate is determined by understanding the activity and
mechanism of the products by applying the partial pressure on the gases such as
CH4, N20. H2O respectively. The equation rate is described as
A
similar variation in selectivity is apparent. The selectivity of combine gases
approaches to 100% that was above the critical pressure. For the formation of
methanol, vapour pressure is essential, which inhibit the rate of CH4
conversion Ion.
Methyl
format by the partial oxidation of formaldehyde and methanol study was taken
into consideration.
5.10.4-Conclusion:
Methane
is used for selective methanol oxidation where formaldehyde occurs over the
support of molybdenum. To form oxygen O- show the most reactive state in the
catalytic cycle. The reaction sequence initiates the ions that formed the
methyl radicals that further develop methoxide ion with their proper protocols.
The direct decomposition of methoxide or formaldehyde reacts with water to form
methyl alcohol.
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