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1. INTRODUCTION

It is well-known that sulphur compounds are undesirable in the fuels.

Elemental sulphur is not toxic, but many simple sulphur derivates are very

toxic, such as sulphur dioxide (SO2) and hydrogen sulphide. Combustion of

sulphur-containing compounds in fossil fuels emits sulphur oxides, which can

cause adverse effects on health, environment and economy.

Globally sulphuric substances can have the following effects on human

health: Disturbance of blood circulation, Heart damage, Effects on eyes and

eyesight, Reproductive failure, Damage to immune systems, Stomach and

gastrointestinal disorder, Damage to liver and kidney functions, Hearing

defects, Disturbance of the hormonal metabolism, Dermatological effects,

Suffocation and lung embolism and, Neurological effects and behavioural

changes

Need for Desulfurization:

Presence of sulphur in crudes is a menace because it causes many difficulties

like-corrosion of metals, in processing of oils, and also environmental pollution

as a result of burning of high sulphur fuels that are processed from crudes

having high sulphur content. In brief, presence of sulphur in crudes causes [1]:

1. Problems of corrosion and odour

2. Pollution problems

3. Cost of waste treatment is a punitive for all refiners with high- sulphur

crudes

4. Sulphur containing residums when cracked leaves cross-linked structures

that resemble the phenomenon of vulcanization of rubber and offer

perennial problems

5. It desists the effects of additives

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6. Its presence in different fractions complicates the refining and treatment

methods

Types of sulphur compounds in various fuels

Table 1.1 below gives us an idea of the type of sulphur compounds that are

present in various fuels. Although sulphur concentrations in gasoline and diesel

fuel are moving to progressively lower levels, additional steps to remove the

remaining sulphur are still required.

Table 1.1 Type of sulphur compound

BOILING RANGE SULPHUR

COMPOUNDS

GASOLINE 25 – 225 *C Mercaptans, sulphides,

disulphides, thiophene

and its alkylated

derivatives,

Benzothiophene

JET FUEL/ KEROSENE 130-300 *C Mercaptans,

benzothiophene,

alkylated Benzothiophene

DIESEL 160-380*C Alkylated

benzothiophene, di-

benzothiophene,

alkylated

dibenzothiophene

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2. LITERATURE REVIEW

Li et al[1] in 2008 had worked on desulphurization of fuel using CuNaY

zeolites that were prepared by microwave irradiation and also studied about the

influence of aromatics on thiophene adsorption. The zeolites are prepared by

Solid phase ion exchange (SPIE) or liquid phase ion exchange (LPIE). LPIE is

quite common. In contrast to the usual process of heating the exchange

suspension through an oil or water bath, microwave irradiation is used. On

analysing the X-Ray powder Diffraction patterns of Na-Y and Cu-ion

exchanged zeolite samples, recorded at 2θ values between 5ᵒ and 60ᵒ, Li showed

that the irradiation technique is a better option because the characteristic peaks

for Cu ion-exchanged zeolite samples are similar to those of Na-Y and no shift

in the peak positions and no significant diffraction lines assigned to any new

phase were observed. They observed the effects of the microwave irradiating

power, duration time and the copper ion concentration in aqueous solutions on

the ion exchange level and the structure of copper ion-exchanged zeolite

samples with the help of atomic absorption spectrophotometer, X-ray powder

diffraction, N2 adsorption and scanning electron microscope and X-ray

photoelectron spectroscopy and showed that microwave irradiation was a more

attractive zeolite preparation method.

Xiao et al [2] in 2008 worked on the adsorption of benzo-thiophene (BT)

and di-benzo-thiophene (DBT) on transition metal ion impregnated activated

carbons and ion exchanged Y- zeolites. A total of 10 samples were prepared

where 5 of them were transition-metal ions (Ag+, Ni

2+, Cu

2+, Zn

2+, and Fe

3+)

separately loaded on the ACs by the impregnation method and the other five

included Y-type zeolites separately containing Ag+, Ni

2+, Cu

2+, Zn

2+, and Fe

3+,

prepared by the liquid ion-exchange method. They compared the Isotherms of

BT and DBT on original activated carbon, with, the effects of different ions on

isotherms of BT and DBT, and concluded that the adsorbing capacity depended

on the concentration of BT, where, at high concentration of BT, activated

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carbon was a better sorbent and at low concentration, Y-zeolite was a good

adsorbent. It was observed that the pore surfaces of the ACs have stronger

interactions with adsorbate DBT compared to BT because the size of DBT is

larger than that of BT. This was the reason why, there was no adsorption of

DBT on Na(I)/Y zeolites. They showed that (1) the adsorption of BT by

Ag(I)/Y was the highest, while that by Na/Y was the lowest and (2) the Ag

(I)/AC was the highest, while that on Fe (III)/AC was the lowest.

David L. King et al [3], worked on removal of sulfur components from

low sulfur gasoline using copper exchanged zeolite Y at ambient temperature.

Copper-exchanged zeolite Y has been shown to be an effective material for

removal of a variety of sulfur species from hydrocarbon streams, and both

monovalent (Cu(I)) and divalent (Cu(II)Y) materials have been claimed to be

effective. In their work, they discussed about experiments aimed at providing a

direct performance comparison between the two copper-containing materials.

Cu(I)Y zeolite is somewhat more effective than Cu(II)Y in removing thiophene

from various fuel blends. Capacity of both materials for thiophene diminishes

markedly when aromatics and/or olefins are present, and Cu(I)Y immediately

turns dark on exposure to such feeds. Both materials demonstrate ability to

convert thiols to disulfides at ambient temperature.

AnkurSrivastav et al [4], there study shows that the alumina could be

used as adsorbent for the desulfurization of liquid fuels. There studies were

performed to understand the mechanism of DBT adsorption onto alumina.

Presence of DBT on the surface of alumina was confirmed by comparing EDX

of DBT loaded alumina. Equilibrium between the DBT in the solution and on

the alumina surface was practically achieved in 24 h. The adsorption processes

was well described by his amulti-stage diffusion model. The DBT up take was

found to be controlled by external mass transfer at earlier stages and by intra-

particle diffusion at later stages The adsorption of DBT onto alumina was found

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to be endothermic in nature with the heat of adsorption being 19.5 kJ/mol. His

experiments best represents the equilibrium adsorption data at all temperatures.

Babich et al [5] ,they discussed about the technologies of sulfur removal

from refinery streams leads to a better research topic. There several topics have

the character of demonstration better removal of sulfur. Some of the integrated

approachs are catalyst selection, reactor design, process configuration will lead

to efficient desulfurization processes that will produce fuels with zero sulfur

emission. There other approaches to sulfur removal, such as extractive

desulfurization, look less attractive since the involvement of an additional phase

leads to large plants and limited efficiency. The same applies for oxidative

extraction, in which in addition to the solvent an oxidant is required in addition

to the solvent, although recycling might reduce the amounts consumed.

Blanco-Brieva et al [6],worked to improve the adsorption capacity and

sorbent regeneration in areas such as increasing specific desulfurization activity,

hydrocarbon phase tolerance, sulfur removal at higher temperature, and

development of new porous substrates for desulfurization of a broader range of

sulphur compounds. There work comprehensively describes the adsorption of

organo-sulfur compounds present in liquid fuels on metal-organic framework

(MOF) compounds. They has been demonstrated that the extent of

dibenzothiophene (DBT) adsorption at temperatures close to ambient (304 K) is

much higher on MOF systems than on the benchmarked Y-type zeolite and

activated carbons. In addition, the DBT adsorption capacity depends strongly on

the MOF type as they illustrated by the much higher extent of adsorption

observed on the Cu-(C300) and Al-containing (A100) MOF systems than on the

Fe-containing (F300) MOF.

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Chetan Borkar et al [7], worked on several experiments on adsorption of

VOC, namely, dichloromethane,on activated carbon by a flow-through

gravimetric technique using a thermo-gravimetric analyser. They took the

measurements which were performed at three different temperatures, namely,

(303.15, 318.15, and 353.15) K. They compared the results to already available

data for the adsorption of dicholoro-methane on activated carbon.Although

higher partial pressures can readily be obtained, he measured the isothermsup to

partial pressures of about 1 kPa; higher partial pressureswould be rarely

encountered in industry. The isotherms werefit using virial and Langmuir

models. It was observed that thebest description of experimental data is

obtained using a virialisotherm across all of the temperatures. The limiting

enthalpyof adsorption obtained using the virial model was -41 kJ ·mol-1.

I.HilalGübbük et al [8],conducted several experiments on synthesis,

characterization, and sorption properties of silica gel-immobilized Schiff base

derivative. Theyderivatized the Silica gel from benzophenone 4-

aminobenzoylhydrazone (BAH), a Schiff base derivative, after silanization of

silica by 3-chloropropyltrimethoxysilane (CPTS) by using a reported method.

The mean sorption energy (E) of benzophenone 4-aminobenzoylhydrazone

(BAH) immobilization onto silica gel was calculated from D–R isotherms,

indicating a chemical sorption mode for four cations. He also calculated the

thermodynamic parameters, like _G, _S, and _H for the system. They observed

_H values were found to be endothermic: 27.0, 22.7, 32.6, and 34.6 kJmol−1 for

Cu(II), Ni(II), Co(II), and Zn(II) metal ions, respectively and _S values were

calculated to be positive for thesorption of the same sequence of divalent

cations onto sorbent. They observed negativeG-values, which indicate that the

sorption process for these three metal ions onto immobilized silica gel is

spontaneous.This study indicated that the immobilized silica gel surface using

BAH after CPTS, as precursor silylating agent, could be used as effective

adsorbent material for the purification of water. The sorption of four metal ions,

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from aqueous solution onto an immobilized silica gel, was studied in his work.

The order of sorption capacities order was “Zn >Cu >Co >Ni”. Immobilized

silica gel may be used as an inexpensive, effective, and alternative sorbent for

removal of four metal ions from aqueous solutions.

Chunshan Song et al [9], worked on deep desulfurization for ultra-clean

gasoline, diesel fuel and jet fuel. It was clear that deep reduction of gasoline

sulfur (from 330 to 30 ppm) must be made without decreasing octane number or

losing gasoline yield. The problem is complicated by the high olefins contents

of FCC naphtha which contributes to octane number enhancement but can be

saturated under HDS conditions. Deep reduction of diesel sulfur (from 500 to

<15 ppm sulfur) is dictated largely by 4,6-dimethyldibenzothiophene, which

represents the least reactive sulfur compounds that have substitutions on both 4-

and 6-positions. The deep HDS problem of diesel streams is exacerbated by the

inhibiting effects of co-existing polyaromatics and nitrogen compounds in the

feed as well as H2S in the product. The approaches to deep desulfurization

include catalysts and process developments for hydro-desulfurization (HDS),

and adsorbents or reagents and methods for non-HDS-type processing schemes.

His research on Desulfurization should also take into consideration of the fuel-

cell fuel processing needs, which will have a more stringent requirement on

desulfurization (e.g., <1 ppm sulfur) than IC engines.

Kyu-Sung Kim et al [10], have worked on removal of sulphur

compounds in FCC raw C4 using activated carbon impregnated with

CuCl and PdCl2 . They studied on several activated carbon(AC) based

adsorbents were to develop a more efficient adsorbent for

removal of mercaptans and sulfides during the FCC refinery

process. The adsorbents were prepared by impregnating AC with

CuCl and PdCl2 .Kyu-Sung Kim evaluate the degree of metal halide

impregnation into the activated carbon support, and each adsorbent

was characterized by N2 adsorption, elemental analysis (EA) and XRF.

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After repeating the experminent several times he stated the sulfur

adsorption capacities of adsorbents decreased in the following order :

AC impregnated PdCl2, AC impregnated CuCl and non-impregnated

AC (NIAC). The saturated adsorbents were regenerated by toluene

treatmentand reactivated at 130 °C under a vacuum.

Hisham S. Bamuflehet al [11], conducted several experiments on single

and binary sulfur removal components from model diesel fuel using granular

activated carbon. Sulfur compounds in diesel comprise mainly of alkylated

benzothiophene (BT), dibenzothiophene (DBT) and its derivatives. They

conducted several studies to desulfurize diesel fuel and opted

Hydrodesulfurization process (HDS) at high temperature (320–380 8C) and

high pressure (3–7 MPa) over CoMo or NiMo catalysts is which is currently a

major process in petroleum refineries to reduce the sulfur in diesel fuel.

Activated carbon surface structure and properties can be controllable to propose

better adsorbents. They chose activated carbon was for refractory compounds

desulfurization of liquid fuels such as fuel oil straight run gas oil and it showed

high adsorptive capacity and selected the refractory sulfur compounds such as

4,6-DMDBT. Selective adsorption of 4,6-DMDBT using activated

carbonactivated prepared by ZnCl2 activator and prepared at differentconditions

from dates’ stone is feasible, promising and worthfurther studying. The studies

of dynamics desulfurizationby adsorption of DBT and 4,6-DMDBT from model

andcommercial diesel in fixed bed adsorbers of activated carbon.

Rosaset al [12], have done several experiments on desulfurization of

low sulfur diesel by adsorption using activated carbon by adsorption isotherms

.Diesel fuels with ultralow sulfur content (15 ppmw) can be contaminated when

they are transported. Experiment conducted desulfurization of diesel fuel with

72 ppmw of sulfur in a batch system using four activated carbons at 303.15 K,

atmospheric pressure, and magnetic stirring during 18 h was performed.

Theycorrelates better the experimental behavior of this adsorbent. For sulfur

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removal of diesel from a total sulfur concentration of 72-15 ppmw, and

recommended to process less than 4.2 g-D/g-A with the used activated carbons.

Also, Celia Marin-Rosas recommended to make additional test to study the

selectivity and competitively between the sulfur compounds and the rest of the

organic compounds present into diesel fuel, such asaromatics, paraffins,

isoparaffins, naphthenes, and olefins.

Yang et al [13], have worked on Desulfurization of Liquid Fuels by

Adsorption via ð Complexation with Cu(I)-Y and Ag-Y Zeolites. Fixed-bed

adsorption using different ð-complexation adsorbents for desulfurization of

liquid fuels was investigated. Cu(I)-Y (autoreduced Cu(II)-Y), Ag-Y, H-Y, and

Na-Y zeolites were used to separate low-concentration thiophene from mixtures

including benzene and/or n-octane, all at room temperature and atmospheric

pressure. Sulfur-free (i.e., below the detection limit of 4 ppmw sulfur) fuels

were obtained with Cu(I)-Y, Ag-Y, and H-Y but not Na-Y. Breakthrough and

saturation adsorption capacities obtained for an influent concentration of 760

ppmw sulphur (or 2000 ppmwthiophene) in n-octane follow the order Cu(I)-Y >

Ag-Y > H-Y > Na-Y and Cu(I)-Y > H-Y > Na-Y > Ag-Y, respectively.

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3. THEORY

3.1 Adsorption and types of adsorption:

Adsorption is a process that occurs when a gas or liquid solute

accumulates on the surface of a solid or a liquid (adsorbent), forming a

molecular or atomic film (the adsorbate). It is different from absorption, in

which a substance diffuses into a liquid or solid to form a solution. The term

sorption encompasses both processes, while desorption is the reverse process.

Adsorption is operative in most natural physical, biological, and chemical

systems, and is widely used in industrial applications such as activated charcoal,

synthetic resins and water purification. Similar to surface tension, adsorption is

a consequence of surface energy. In a bulk material, all the bonding

requirements (be they ionic, covalent or metallic) of the constituent atoms of the

material are filled. But atoms on the (clean) surface experience a bond

deficiency, because they are not wholly surrounded by other atoms. Thus it is

energetically favourable for them to bond with whatever happens to be

available. The exact nature of the bonding depends on the details of the species

involved, but the adsorbed material is generally classified as exhibiting

physisorption or chemisorption.

Physisorption or physical adsorption is a type of adsorption in which the

adsorbate adheres to the surface only through Vander Waals (weak

intermolecular) interactions, which are also responsible for the non-ideal

behaviour of real gases.

Chemisorption is a type of adsorption whereby a molecule adheres to a

surface through the formation of a chemical bond, as opposed to the Van der

Waals forces which cause physisorption.

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Adsorption is usually described through isotherms, that is, functions

which connect the amount of adsorbate on the adsorbent, with its pressure (if

gas) or concentration (if liquid). One can find in literature several models

describing process of adsorption, namely: Freundlich isotherm, Langmuir

isotherm, BET isotherm, etc.

Table 3.1 Comparison between Physisorption and Chemisorption

Physisorption Chemisorption

Low heat of adsorption usually in the

range of 20-40 kJ mol-1

High heat of adsorption in the range

of 40-400 kJ mol-1

Force of attraction are Van der Waal's

forces

Forces of attraction are chemical

bond forces

It usually takes place at low temperature

and decreases with increasing

temperature

It takes place at high temperature

It is reversible It is irreversible

It is related to the ease of liquefaction of

the gas

The extent of adsorption is generally

not related to liquefaction of the gas

It is not very specific It is highly specific

It forms multi-molecular layers It forms monomolecular layers

It does not require any activation energy It requires activation energy

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Factors affecting adsorption: The extent of adsorption depends upon the

following factors:

• Nature of adsorbate and adsorbent.

• The surface area of adsorbent.

• Activation of adsorbent.

• Experimental conditions. E.g., temperature, pressure, etc.

3.2 Applications of adsorption:

The principle of adsorption is employed,

1. In heterogeneous catalysis.

2. In gas masks where activated charcoal adsorbs poisonous gases.

3. In the refining of petroleum and decolouring cane juice.

4. In creating vacuum by adsorbing gases on activated charcoal.

5. In chromatography to separate the constituents' of a mixture.

6. To control humidity by the adsorption of moisture on silica gel.

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Important Adsorbents and their Uses:

� Silica Gel:

• Drying of gases, refrigerants, organic solvents, transformer oils

• Desiccant in packings and double glazing

• Dew point control of natural gas

� Activated Alumina:

• Drying of gases, organic solvents, transformer oils

• Removal of HCl from hydrogen

• Removal of fluorine in alkylation process

� Carbons:

• Nitrogen from air

• Hydrogen from syngas

• Ethene from methane and hydrogen

• Clean-up of nuclear off-gases

• Water purification

� Zeolites:

• Oxygen from air

• Drying of gasses

• Removing water from azeotropes

• Sweetening sour gases and liquids

• Purification of hydrogen

• Separation of xylenes and ethyl benzene

� Polymers and Resins:

• Water purification

• Recovery and purification of steroids, amino acids

• Separation of fatty acids from water and toluene

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3. 3. Methods for Desulfurization

Hydrodesulphurization process (HDS) at high temperature (320–380 8C)

and high pressure (3–7 MPa) over CoMo or NiMo catalysts was a major process

in petroleum refineries to reduce the sulphur in diesel fuel. The major sulphur

compounds existing in current commercial diesel are the alkyl di-

benzothiophenes (DBTs) with one or more alkyl groups at 4 or/and 6 positions

which have been considered to be refractory sulphur compounds in the fuel due

to the steric hindrance of the alkyl groups in HDS. This process is highly

efficient for the removal of thiols, sulfides, and disulfides.However, it is

difficult to reduce sulphur levels to an ultra low level using the HDS process

because of the very low reactivity of the HDS catalysts towards sulphur

compounds and also towards refractory sulphur-containing compounds such as

dibenzothiophene and its derivatives especially 4,6-dimethydibenzothiophene

(4,6-DMDBT). An increase in the reactor size and hydrogen consumption is

required to achieve high levels of desulphurization.

Other methods, such as oxidative desulphurization and bio-

desulphurization, have shown good potential for removing refractory sulphur

under mild conditions. This process is based on the well known propensity of

organic sulphur compounds to be oxidized; it consists of an oxidation followed

by the extraction of the oxidized products. The greatest advantage of oxidative

desulphurization and bio-desulphurization, compared with the conventional

HDS technology, is that they can be carried out in the liquid phase under very

mild conditions near room temperature and under atmospheric pressure.

The advantage of BDS is that it can be operated in conditions that require

less energy and hydrogen. BDS operates at ambient temperature and pressure

with high selectivity, resulting in decreased energy costs, low emission, and no

generation of undesirable side products. Over the last two decades several

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research groups have attempted to isolate bacteria capable of efficient

desulphurization of oil fractions.

ODS offers several advantages compared with HDS. For example, the

refractory-substituted dibenzothiophenes (DBTs) are easily oxidized under low

temp and pressure conditions so expensive hydrogen is not required and,

therefore, the capital requirement for an ODS unit is significantly less than that

for a deep HDS unit.Currently, the main obstacles to the industrial application

of ODS are (1) their low-oxidation activity and their low selectivity for the

sulfides present in fuel oils, (2) the difficulties in separation and recovery of the

catalysts after the reactions, (3) the low utilization efficiency of H2O2, and (4)

the introduction of other components to the oxidation systems.

Desulphurization of commercial fuels by selective adsorption has been

reported as an alternative technology for the current HDS method. Yang and co-

workers reported using zeolites for selective adsorption under ambient

conditions for the desulphurization of commercial fuels [6-10]. Metal ion-

exchange Y zeolites have also been shown to effectively remove sulphur

compounds under ambient conditions. However, the sulphur adsorption capacity

depends on the composition of the fuel. Adsorptive removal of sulphur

compounds from liquid commercial fuels has been widely investigated using

various different adsorbents. Ag-Y and Cu-Y zeolites have been shown to have

a particularly high adsorption capacity and selectivity for thiophene and its

derivatives. The advantages of using absorbents, such as the low-energy

demands of the process, potential to regenerate the spent adsorbent, and broad

availability of adsorbents, have made adsorption processes an attractive area of

research.

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Figure 3.1 Methods for Desulfurization

3.4 Gas Chromatograph

Gas chromatography is used to identify and quantitate individual components in

a mixture. Quantitation uses chromatographic data to determine the amount of a

given component in a mixture and the data can be in the form of either peak

height or peak area which is obtained from an integrated chromatogram.

Methods available for De-

decompostion of sulphur compounds

with hydrocarbon

return

•conventional HDS

•HDS with octane recovery

•selective oxidation

•reactive adsorption

•bio-desulfurization

.1 Methods for Desulfurization

Gas Chromatography:

Gas chromatography is used to identify and quantitate individual components in

a mixture. Quantitation uses chromatographic data to determine the amount of a

given component in a mixture and the data can be in the form of either peak

which is obtained from an integrated chromatogram.

Methods available for -sulfurization

seperation of S-compounds without S

elimination

•alkylation

•extraction

•oxidation to sulfones

•precipitation

•adsorption

combinationseperation

+decomposition

• catalytic distillation

Gas chromatography is used to identify and quantitate individual components in

a mixture. Quantitation uses chromatographic data to determine the amount of a

given component in a mixture and the data can be in the form of either peak

which is obtained from an integrated chromatogram.

Methods available for

combination-seperation

+decomposition

catalytic distillation

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Figure 3.2 Schematic Layout of GC

Quantitative Methods

The most common methods used are Area percent, Single point external

standard,Multiplepoint external standard, Single point internal standard and

multiple point internal standards. Among those:

Area Percent Method: This method provides a rough estimate of the amounts

of analytes present and for calculating area percent take the area of an analyte

and divide it by the sum of areas for all peaks. This value represents the

percentage of an analyte in the sample.

Single Point External Standard: Analyze a sample containing a known

amount of analyte or analytes and record the peak area.

Then calculate a response factor.

Response factor = (Peak area / sample amount)

after getting the response factor we can calculate the amount of unknown

analyte of the sample

Amount of analyte=(Peak area / response factor)

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Procedure:

When a sample is injected into the correct column, a carrier gas sweeps the

sample through the column. If necessary, an oven heats the system to vapourize

the sample and speed its passage through the column. The different components

of the sample will be separated by the column because each of the components

sticks to the liquid coating that on the column packing differently. The greater

the stickiness the longer it takes for a substance to pass through the column.

When a substance leaves the column, it is sensed by a detector. The detector

generates a voltage that is proportional to the amount of the substance. The

signal from the detector is then displayed by a chart recorder and/or fed into a

computer.

Modern gas chromatograph’s are connected to a computer which displays the

peaks of all the substances in the sample. This is called the chromatogram.

The time that it takes a substance topass through the instruments from injection

to detection is called retention time. The retention time is measured from the

injection point topeak height. The amount of substance in a sample is

proportional to the area under the peak of that substance and that proportionality

constant is different for each substance and detector.

Chromatography(GC) is a method of separating “volatile” compounds so that

they may detected individually in complex mixtures. Compounds are separated

based on differences in their vapour pressures and their attraction to solid

materials inside the instruments. Because the vapour pressure of a given

compound is a function of intermolecular forces between molecules, GC takes

advantages in differences in at least one of the properties of matter

In GC, the sample is injected into the instrument using a small syringe. The

sample is swept into the instrument using a carrier gas where the sample is

separated into its individual chemical components, called analytes. Separation is

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achieved by both attraction to the stationary phase and differences in vapour

pressure. Because vapour pressure varies with temperature, the temperature of

the instrument is often adjusted during the chromotoraphic run. A detector,

which is designed to sense analyte molecules as they exit the GC, is at the exit

of the column.

Because the analyte molecules bind differently to the stationary phase, they

travel through the GC column at different rates. That is, they have different

retention times on the column. As an analyte appears in the detector, its

presence is signaled by a peak. Thus, a gas chromatogram consists of a series of

peaks,one for each of the components of the sample. The chromatogram is

displayed on a chart recorder or computer screen.

Gas chromatography is an instrumental method for the separation and

identification of chemical compounds. Chromatography involves a sample

being dissolved in a mobile phase. The mobile phase is then forced through an

immobile, immiscible stationary phase. The phases are chosen such that

components of the sample have differing solubilites in each phase. A

component that is quite solute in the stationary phase will take longer to travel

through it than a component that is not very soluble in the stationary phase but

very soluble in the mobile phase. As a result of these differences in mobilities,

sample components will become separated from each other as they travel

through the stationary phase. After the separation of the compounds, Flame

Ionization Detector(FID) is used to identify each of them and determine their

mass.

The effluent from the column is mixed with hydrogen and air, and ignited.

Organic compounds burning in the flame produce ions and electrons that can

conduct electricity through the flame. A large electrical potential is applied at

the burner tip, and a collector electrode is located above the flame. The current

resulting from the pyrolysis of any organic compounds is measured. FID s are

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mass sensitive rather than concentration sensitive; this gives the advantage that

changes in mobile phase flow rate do not affect the detectors response. The FID

is a useful general detector for the analysis of organic compounds; it has high

sensitivity, a large linear response range, and low noise. It is also robust and

easy to use, but it destroys the injected sample.

After detection, a signal is sent to the recording device. Each analyte in a

sample will have different retention time. The time taken for the mobile phase

to pass through the column is called tM.

A GC can separate the compounds, but cannot identify them itself. By

calibrating GC you can find out at what time various organic compounds are

being detected. The area under the curve may be expressed in terms of

concentration of the pollutant, by running some calibration standards at known

concentration.

Calculating the Area: The area of a peak is proportional to the amount of the

compound that is present. The area can be approximated by treating the peak as

a triangle. The area of a triangle is calculated by multiplying the height of peak

times its width at half height.

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4. EXPERIMENTAL PROCEDURE

Adsorbent properties:

1. cbv-3020 (H-ZSM-5)

Si/Al = 33

Pore size = 0.54 mm

Pore Volume = 0.19 ml/gm

2. cbv 20A: (Hmodermite-c)

Si/Al =20

Surface Area =420 m2/gm

Nominal Cation form = H2

Ag-Y Zeolite Adsorbent Preparation:

As Na in Na-Y zeolite is less active towards sulphur, it is better to replace

the Na with Cu or Ag(which are more active towards sulphur). To prepare 0.2M

Ag-Y Zeolite adsorbent , take 60ml distilled water in a 250ml conical flask and

add 2gms of Na-Y zeolite and 2gms of AgNO3(Silver Nitrate). Keep this

solution away from sunlight by keeping in a dark room for 48 hours. After 48

hours filtrate the solution by using filter papers and dry it. Later wash the dried

filtrate with distilled water. Again filter the solution and dry it. The required

Ag-Y Zeolite is prepared[9].

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Procedure:

Take 3 conical flasks of 50 ml volume. Fill these conical flasks with 10

ml toluene in each with the help of burette. To make a 500 ppm of sulphur

content, add 5 milligrams of Thiophene in each flask. Measure the Thiophene

peaks of each flask with the help of Gas Chromatography Equipment for one of

the adsorbent. And then add available adsorbents like zeolites, activated carbon

etc. Before adding the adsorbents, they have to be activated at 110 °C in heater.

After activating the adsorbents, add 1gm of each adsorbent in each

conical flask. After adding adsorbents, keep these flasks in shaker for 24hours.

After 24 hours of shaking, filtrate the solutions and measure the sulphur content

in each flask with the help of Gas Chromatography Equipment. The percentage

of suphur removal and the amount of sulfur adsorbed onto the adsorbent were

measured using the expressions

Percentage sulfur removal = 100*(C0−Cf)/C0

Amount of adsorbed sulfur per gram of solid =(C0−Cf)/m

where,

C0 is the initial sulfur concentration (mg/l),

Cf is final sulfur concentration (mg/l) and

mis the adsorbent dose in grams per litre of solution

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Table 4.1 Gas Chromatography Operating Conditions:

COLUMN USED ZB WAX PLUS

INJECTION TEMPERATURE 250°C

COLUMN TEMPERATURE 120°C

FID TEMPERATURE 250°C

SPLIT RATIO 100

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5. RESULTS AND DISCUSSION

Table 5.1: Percentage of sulphur removal

Adsorbent INITIAL CONC FINAL CONC % REMOVED

cbv-3020 500 97 80

cbv-720 500 337.2 33.56

Hβ-zeolite 500 207.3 58.5

Ag-Y 500 148.5 70.3

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Figure 5.1: The amount of sulphur adsorbed in mmol/gm on different

adsorbents

Figure 5.2: The percentage of sulphur removal on four adsorbents.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Cbv 3020 zeolite Hbeta zeolite Cbv 720 zeolite Ag-y zeolite

Amount of sulfur

adsorbed mmol/gm

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Cbv 3020 zeolite Hbeta zeolite Cbv 720 zeolite Ag-y zeolite

% sulfur removed

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Table 5.1shows the initial and final concentrations of the thiophene-toluene

solutions onto the different zeolites. Figure 5.1 shows the amount of sulphur

adsorbed in mmol by the various adsorbents for 1gm of sample solution

taken.While Figure 5.2 shows the percentage of sulfur removed by various

adsorbents and all the experiments were carried out at normal atmospheric

conditions ie., room temperature. The amount of thiophene adsorbed onto the

cbv-3020 is 4.78 mmol/gm and it can be seen that the cbv-3020 zeolite is a very

efficient zeolite for desulfurization. Whereas Xiao et al suggested that Ag-Y

zeolite interaction towards thiophene is more compared to Na-Y zeolite. So in

our laboratory we attempted to synthesize the modified Zeolite ie.,replacing the

Na+ metal ion in Na-Y zeolite with Ag+ metal, and we observed the amount of

thiophene adsorption is higher than the Na-Y zeolite.

On interpreting the results we find that the cbv-3020 zeolite is having higher

adsorption, due to its large surface area and pore size. The pore size of cbv-3020

zeolite adsorbent is 0.54mm which is higher than the other adsorbents and

allowing more thiophene molecules to accommodate in its pores. Whereas Hβ

zeolite, due to its low surface area and pore size cannot adsorb sulphur

efficiently.

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6. CONCLUSION

Conventional HDS process is highly efficient for the removal of thiols, sulfides,

and disulfides. However, it is difficult to reduce sulphur levels to an ultra- low

level because of the very low reactivity of the HDS catalysts towards sulphur

compounds and also towards refractory sulphur-containing compounds such as

di-benzothiophene and its derivatives. Adsorption is also another method

available for the removal of sulfur at ambient temperature and pressure and this

process can be worked out without using hydrogen. The reactivity order of

sulfur components is Thiophene > Benzothiophene > Dibenzothiophene.

Initially our experiments carried out on thiophene removal on different zeolites

at room temperature in order to understand the interaction of thiophene

molecule with different metal ions in zeolites. The adsorption capacity increases

in the order of cbv 3020>AgY>Hβ zeolite>cbv 720. The larger adsorption is

due to stronger interaction towards metal ion. The adsorbent cbv-3020 was very

effective in removal of sulphur and we also observed that Ag-Y zeolite was

effective in removing sulphur from toluene-thiophene solution, however, due to

the presence of unavoidable impurities and experimental errors, resulted in

significantlycompromised adsorption performance in our tests.

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7. REFERENCES

[1] David L. King *, Liyu Li “Removal of sulfur components from low sulfur gasoline

usingcopper exchanged zeolite Y at ambient temperature”Catalysis Today 116 (2006) 526–529

[2] Jing Xiao, Zhong Li,* Bing Liu, Qibin Xia, and Moxin Yu “Adsorption of

Benzothiophene and Dibenzothiophene on Ion-Impregnated Activated Carbons and Ion-

Exchanged Y Zeolites”

Energy & Fuels 2008, 22, 3858–3863

[3]David L. King *, Liyu Li “Removal of sulfur components from low sulfur gasoline using

copper exchanged zeolite Y at ambient temperature”Catalysis Today 116 (2006) 526–529

[4] AnkurSrivastav, Vimal Chandra Srivastava “Adsorptive desulfurization by activated

alumina”Journal of Hazardous Materials 170 (2009) 1133–1140

[5]I.V. Babich*, J.A. Moulijn “Science and technology of novel processes for deep

desulfurization of oil refinery streams: a review”Fuel 82 (2003) 607–631

[6] G.Blanco-Brieva, J.M.Campos-Martin, S.M.Al-Zahrani† “REMOVAL OF

REFRACTORY ORGANIC SULFUR COMPOUNDS IN FOSSIL FUELS USING MOF

SORBENTS” Global NEST Journal, Vol 12, No 3, pp 296-304, 2010

[7] ChetanBorkar, DheerajTomar, and Sasidhar Gumma* “Adsorption of Dichloromethane

on Activated Carbon”J. Chem. Eng. Data 2010, 55, 1640–1644

[8] I.HilalGübbük, RamazanGüp, Mustafa Ersöz† “Synthesis, characterization, and sorption

properties of silica gel-immobilizedSchiff base derivative”Journal of Colloid and Interface Science 320

(2008) 376–382

[9] ChunshanSong“An overview of new approaches to deep desulfurization forultra-clean

gasoline, diesel fuel and jet fuel”Catalysis Today 86 (2003) 211–263

[10] Kyu-Sung Kim, Sun Hee Park, Ki Tae Park, Byung-Hee Chun, and Sung Hyun Kim†

“Removal of sulfur compounds in FCC raw C4 using activated carbon impregnated with

CuCl and PdCl2”Korean J. Chem. Eng., 27(2), 624-631 (2010)

[11] Hisham S. Bamufleh” Single and binary sulfur removal components from model diesel

fuel using granular activated carbon from dates’ stones activated by ZnCl2”Applied Catalysis A:

General 365 (2009) 153–158

[12] CeliaMarı´n-Rosas,*,† Luis F. Ramı´rez-Verduzco,† Florentino R. Murrieta-Guevara,†

Gonzalo Herna´ndez-Tapia,† and Luis M. Rodrı´guez-Otal‡ “Desulfurization of Low Sulfur

Diesel by Adsorption Using Activated Carbon:Adsorption Isotherms”Ind. Eng. Chem. Res. 2010, 49,

4372–4376

[13] Arturo J. Herna´ndez-Maldonado and Ralph T. Yang “Desulfurization of Liquid Fuels

by Adsorption via ð Complexationwith Cu(I)-Y and Ag-Y Zeolites”Ind. Eng. Chem. Res. 2003, 42, 123-

129

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8. APPENDIX

SAMPLE1

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SAMPLE 1 (AFTER ADDING ADSORBENT :CBV-3020)

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SAMPLE: 2

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SAMPLE 2( AFTER ADDING ADSORBENT:CBV 720)

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SAMPLE 3

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SAMPLE3 (AFTER ADDING ADSORBENT :Hβ ZEOLITE)

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SAMPLE 4:

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SAMPLE 4(AFTER ADDING ADSORBENT: AG-Y ZEOLITE)