Controlling Benzene Emissions Using Catalytic Oxidation.pdf

7/25/2019 Controlling Benzene Emissions Using Catalytic Oxidation.pdf

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Chemical Engineering Department

CHE470 project

Controlling Benzene Emissions by using Catalytic OxidationStudents Name ID

Bbbbb Abdulrahman Omar 201174730

bMohammed AL-Ahmari 201128390

bBarakat AL-Hamed 201139030

bbAbdulkarem Farsi 200917890

Prepared for: Dr. Mohammed Ba-ShammakhSubmission Date: 15/12/2015


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ABSTRACT:

In order to control benzene emissions, there are many different techniques, among these

techniques, catalytic oxidation were studied. In this technique, both controlling benzene using

zeolite-supported metal oxide nanoparticles and nanoscale HZSM-5 supported Pt bimetallic

catalyst. By using zeolite-supported metal oxide nanoparticles, we found that the removal

efficiency of benzene is the highest for MnO2followed by CoO, while CeO2 showed the lowest

efficiency. MnO2/ZSM-5 also showed the highest activity toward catalytic ozonation of benzene.

For the second case study, nanoscale HZSM-5 supported Pt bimetallic catalyst was discussed. In

this technique, we found that using nanoscale HZSM-5 will improve the surface area and the

adsorption capacity comparing to the conventional microscale HZSM-5. Using three different

catalysts, PtAg/HZ-S, PtAg/HZ-M, and PtAg/HZ-L, we found that PtAg/HZ-S is the best catalyst

in term of highest conversion of formaldehyde at lowest temperature and also for the benzene

capacity and oxidation. The highest removal efficiency that can be obtained is 99% using Thermal

Oxidation or Membrane Separation, while the lowest removal efficiency is 60% using Bio-

filtration. Membrane Separation has the best efficiency per cost value.


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OUTLINE:

1. INTRODUCTION 1

2. BACKGROUND 1

3. BENZENE PROPERTIES ...2

3.1 PHYSICAL PROPERTIES ...2

3.2 CHEMICAL PROPERTIES .2

3.2.1 ELECTROPHILIC SUBSTITUTIONAL REACTIONS ......4

3.2.2 ADDITIONS REACTIONS ..6

3.2.3 OXIDATION OF BENZENE ...7

4. BENZENE TOXICITY . ..8

4.1 HEALTH EFFECTS ..8

3.2.1 SHORT-TERM EXPOSURE ..8

3.2.2 LONG TERM EXPOSURE .8

4.2 EXPOSURE LEVELS ...9

4.3 EPA REGULATIONS .10

5. SOURCES OF BENZENE EMISSIONS .11

5.1 INDOOR SOURCES ...11

5.2 INDUSTRIAL SOURCES ..11

5.3 OTHER SOURCES .11

6.

CONTROLLING METHODS OF BENZENE ...12

6.1 DESTRUCTION ..12

6.1.1 THERMAL OXIDATION .12

6.1.2 CATALYTIC OXIDATION ..13

6.1.2.1 CASE STUDY I: REMOVAL OF FORMALDEHYDE AND

BENZENE USING NANOSCALE PTAG/HZSM-5 CATALYST 14

6.1.2.2 CASE STUDY II: CATALYTIC OXIDATION OF BENZENE

WITH OZONE USING ZEOLITE SUPPORTED METAL OXIDES

NANOPARTICLES 16

6.2 RECOVERY .21

6.2.1 ADSORPTION OF BENZENE BY USING ORDERED MESOPOROUS

CARBON 21

CONCLUSION AND RECOMMENDATION..22


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1. Introduction:

With the world becoming more and more dependent on industrial processes, air pollution became

a huge concern. Volatile organic compounds (VOC) is considered as one of the major pollutants.

BTEX, which stands for Benzene, Toluene, Ethylbenzene, and Xylene, were selected as the major

components of VOC. Among these four major pollutants, Benzene is the most emitted pollutant.

Benzene, with a molecular structure of C6H6, is considered as the basis of aromatics. Benzene, also

called cyclohexa-1,3, is colorless and clear chemical compound, it has a sweat odor and it is

both flammable and volatile. What makes Benzene a public concern matter is its ability to react

with body tissues, which make it a carcinogenic pollutant. Benzene is most often used as a

feedstock to create other chemicals, also as a solvent to extract or dissolve other materials. The

major two sources of Benzene emission are the industrial processes and the indoor residential air.

2. Background

In 1865, Kekule found that all the aromatics compounds have at least six carbons. Kekule proved

that Benzene, with its six carbons, is the simplest aromatic and with a structure of a cyclic planner

six carbons unit where each two atoms is attached to each other by covalent bond. In the past,

Benzene was commonly produced in the refinery depending on the gasoline production. These

processes includes: tire manufacture, painting, adhesives, gas, petroleum, cleaning products and

as a by-product the cracking of naphtha. However, these common ways for producing benzene

have changed. Nowadays, increasing in the demand of PET production from Para-xylene in Asia

lead to the production of benzene as a by-product and the great expansion in the processing of

heavy oil in the refinery and the cracking for the production of lighter olefins have led to more

benzene production.


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3. Benzene Properties:

Benzene is considered as the simplest aromatic compound. In Benzenes hexagonal ring, there

are three alternating PI bonds. The length of carbon-carbon single bond is about 154 pm, and

for the double bond 134 pm. Due to resonance in molecule, the carbon-carbon bond length is

intermediate to these two values and it is equal to 139 pm. In order to understand how to control

the emission of benzene, it is important first to understand its physical and chemical properties.

3.1 Physical properties:

In general, aromatics have a unique odor and they are colorless. In nature, Benzene is carcinogenicand toxic and it is a highly flammable, non-polar liquid. Benzene is less denser than water and

burns with a dusty flame, due to the high percentage of carbons comparing to alkenes. The freezing

point of benzene is 278.8 K and the boiling point is 353.3 K. The density of benzene is 0.8765

g/cm3. A complete table of benzenes physical properties is shown in Appendix.1 (Table.1).

3.2 Chemical Properties:

Since a large percentage of Benzene emissions is due to a chemical processes, it is important to

understand the different chemical properties of benzene and most importantly, its reactions. Due

to the high degree of unsaturation, Benzene will undergoes substitution reactions, which is a

behavior called aromatic character of aromaticity. Benzene will lose its aromaticity when it is

undergoes additional reactions, hence, benzene preferred to undergoes substitution reactions

instead of additional. As mentioned before, benzene has three alternating pi bonds. These bonds

make the molecule stable. The carbons atoms are sp2hybridized with each carbon having one

unhybridized p-orbital. The delocalization of theses six p-orbitals can be shown in the following

figure.


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Figure.1: The delocalization of p-orbitals

Over the whole ring, the six pi-electrons are delocalized. This results in a circle representation of

the conjugated double bonds with carbon-carbon bond length becomes equal. Benzene usually

represented by a structure called resonance hybrid of benzene, which is shown below in the

figure.

Figure.2: Resonance hybrid of benzene

The high density of electrons and the resonance makes benzene undergoes electrophilic

substitution reaction. In the presence of a strong reagents, benzene can undergoes additional and

oxidation reactions. The common chemical properties of benzene are shown below:


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3.2.1. Electrophilic substitution reaction

This considered as the common substitution of benzene. The reaction is a multi-step reaction

with an initial step containing a generation of a strong electrophilic species using catalysts and

co-reagents. The electrophile interacts with benzene, forming a cyclohexadienyl cation (known

as Wheland complex or s complex or Arenium ion). In the second step, a base is introduced in

the reaction and react with s complex forming substituted product through deprotonation. This

steps are shown in the following figure:

Figure.3: Steps of electrophilic substitution reaction of benzene

This Arenium ion is a stable intermediate. This is due to the delocalization of the positive charge

on the ring.

Figure.4: The stability and delocalization of Arenium ion


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The table below will show different electrophilic substitution reactions with its corresponding

electrophile, catalyst and product.

Table.2: Different electrophilic substitution reactions of benzene

The intermediate of the substitution reaction is not aromatic in nature. As a result, the reaction

will continue happing until the aromaticity regained. The energy versus reaction coordinate is

shown in the following figure:

Figure.5: Reaction mechanism diagram of electrophilic substitution reactions of benzene


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3.2.2. Addition reaction of benzene

Under more drastic conditions, Benzene shows some of addition reactions such as alkyne and

alkene.. The products formed behaved as saturated hydrocarbons and they are more stable.

Halogenation and hydrogenation are the most common addition reactions of benzene and results

from the formation of benzene hexachloride and Cyclohexane, respectively. In the presence of

catalyst like nickel or palladium with a reaction temperature of 475-500K, benzene will

undergoes hydrogenation to form cyclohexane.

Figure.6: Hydrogenation of benzene

Halogenation of benzene can occur in the presence of sunlight without the need of a catalyst. Theaddition of chlorine with benzene under these conditions will produce benzene hexachloride

(also Known as BHC). The reaction follows free radical mechanism:

Figure.7: Halogenation of benzene


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3.2.3. Oxidation of benzene

Benzene combustion, like any other hydrocarbons, will produce water and carbon dioxide. Asmentioned before, benzene burns with dusty flame due to the high carbon ration compares to

hydrocarbons.

2C6H6+15O2 2CO2+ 6H2O + HEAT

Further research was obtained to control the oxidation by using catalyst such as vanadium

pentaoxide (V2O5) at a temperature of 725 K. This will results in producing maleic anhydride.

Figure.8: Controlled oxidation by using V2O5

Furthermore, glyoxal can be produce from the ozonolysis of benzene through the formation of an

intermediate known as benzene triozonide:

Figure.9: The oxidation of benzene to produce glyoxal


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4. BENZENE TOXICITY

4.1Health Effects:

4.1.2 Short-term Exposure:

Short Exposure to benzene emissions (not lasting more than a day) may cause loss of

consciousness, confusion, drowsiness, tremors, headaches, narcosis and dizziness. Benzene is

also known to cause skin and eye irritation.

4.1.2 Long-term Exposure

Long exposure to Benzene emissions (usually from 7 to 70 years) is very dangerous for several

reasons:

1) Benzene is well known for its ability to cause cancer. The International Agency for

Research on Cancer has classified benzene as carcinogenic to humans. Exposure to

benzene can cause leukemia, which is a group of cancers that usually begin in the bone

marrow and result in high numbers of abnormal white blood cells that are not fully

developed.

Table.3: Individuals chance of developing cancer due to Chronic exposure of Benzene (USEPA)


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2) The reduction in the production of white and red blood cells from the marrow in humans.

3) Benzene emissions can decrease the host resistance to infection by reducing the

proliferation of both the B-cell and T-cell as reported by several laboratory when the

animals were exposed to benzene.

4.2Benzene exposure levels:

The following tables shows the population-weighted personal exposure to benzene outweigh the

outdoor air concentration. It was found that the total mean personal exposure is 15 !g/m3compared

with only 6 !g/m3 of total mean outdoor concentration, which means that the contribution of

personal activities or in home sources exceeds outdoor sources for benzene exposure. Tables

showing the population exposure level to benzene in different U.S. cities is shown in Appendix.1.

It was also noticed that smoking has great impact on the concentration of benzene that is being

breathed by the people. It was found that the concentration of benzene in the home of smokers was

50% higher than in the homes of non-smokers:

Figure.9: Geometric mean benzene concentrations in the breath ofSmokers exceeded breath

concentrations of nonsmokers.


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4.3EPA REGULATIONS:

The environmental protection agency (EPA) has developed the Tier 3 program which aims to

protect the public health and air quality by reducing motor vehicles impacts. The following table

shows an estimated emission reduction from Tier 3 standards.

Table.4: estimated emission reduction from Tier 3 standards.

As we can see from the above table it is expected that by 2030 the benzene emission will

increase to reach 26% on road.

! The Tier 3 program by 2030 will annually prevent the following:

1. 1.4 million lost school and working days.

2. 2200 hospital entrance and emergency room visits for asthma ill situations.

3. 19000 asthma worsening.

4. 770-2000 early deaths.

5. 30,000 lower and upper respiratory symptoms in children.


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5. SOURCES OF BENZENE EMISSIONS

5.1 Indoor sources:

Most of the Benzene emissions indoor comes from smoking in both homes and public areas.

Some of the emissions also come from building materials like adhesives and paints. Houses with

attached garages show a higher benzene concentration in the air than those with detached

garages. It is also known that when unflued oil is heated it emits benzene and the closer the

house to a petrol filling station the higher the levels of benzene are.

5.2 Industrial Sources:

Generally, the processing of petroleum products, coking of coal and the production of aromatics

(Toluene and Xylene) are the main sources for benzene emissions in the industry. Usually

workers in in industries like oil refineries, rubber industry, shoe manufacturers and chemicalplants are exposed to high levels of benzene.

5.3 Other Sources:

Other sources include:

1-

Vehicle exhausts.

2- Automobile service stations.

3- Paints and Glues.

4- Waste sites and leakage from storage tanks.

5- Waterborne and foodborne benzene.


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6. CONTROLLING METHODS OF BENZENE:

6.1 DESTRUCTION

6.1.1 THERMAL OXIDATION:

The heart of any thermal incinerator is a nozzle-stabilized flame maintained by a combination of

auxiliary fuel. Polluted gas is passed through the flame then it is heated from its inlet temperature

to its ignition temperature. Ignition temperature varies for widely for different VOCs and is

usually determined empirically. Units should be operated at temperatures higher than ignition

temperature to ensure auto ignition. For Polluted gas with typical temperatures of 1,200 to

2,000oF, most thermal units are designed to provide no more than 1 second of residence time.

The selected temperature must be maintained for the full, selected residence time for combustion

to be complete. The most common Incinerators are:

Direct Flame Incinerators

By raising the VOC containing stream to the desired reaction temperature and then holding it

there for the given reaction time to achieve the required destruction efficiency

Recuperative Incinerators

Improving energy efficiency by placing heat-exchangers in the gas downstream

Figure.10: Typical thermal incinerators


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6.1.2 CATALYTIC OXIDATION:

Catalytic incinerators uses catalyst that effectively increase the overall combustion reactiongiven in. To enable conversion at lower reaction temperatures than normal temperatures, the

catalyst increase the reaction rate by lowering the activation energy. The polluted stream is

preheated either directly in a preheater combustion chamber or indirectly by heat exchange. After

that, gas stream is passed over the catalyst bed. The combustion reaction takes place at the

catalyst surface between the oxygen in the gas stream and the gaseous pollutants.

Figure.11: Typical catalytic incinerators

Back in history, organic compounds containing only carbon, hydrogen, and oxygen is oxidized

by catalytic oxidation for control of gaseous pollutants and has only been restricted to them.

Gases containing compounds with chlorine, sulfur, and other atoms that may deactivate the

supported noble metal catalysts often used for VOC control were not suitably controlled by

catalytic oxidation systems. However, recently catalytic combustion has been intensively studied

to be able to use it in industrial application. However, it can only proceed at high temperature,

therefor, needs heating equipment and energy consumption with the risk of explosion. The

catalysts could be easily deactivated due to sintering at high temperature. Thus, it is highly

desirable to catalytic oxidation of VOCs at low temperature, preferentially at room temperature.

Catalytic oxidation has been successfully achieved under the help of ozone since it greatly

decreases the apparent activation energy. Main concerns with catalytic ozonation that it is not


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suitable for high concentration VOCs and with catalyst issues such as catalytic deactivation and

poor capacity for the complete mineralization of VOCs

Deactivation of catalyst could be overcome by the modification of catalyst, supports and

operating parameters; however, CO2selectivity was still not satisfactory. These issues greatlyprevent the industrial application of catalytic ozonation.

Case study I: Removal of formaldehyde and Benzene Using Nanoscale PtAg/HZSM-5

Catalyst (By Catalyst Today):

In some cases, benzene will be emitted along with formaldehyde, especially from materials used

in construction and from decorative materials. It is important to remove both formaldehyde

(HCHO) and benzene (C6H6) simultaneously in indoor air because of their effects on humanhealth. The removal of HCHO and benzene simultaneously remains challenging. Using physical

adsorption seems to be promising, but the problem with the adsorbing material (usually zeolites or

carbon activated) that it cannot adsorb HCHO and benzene effectively in the presence of water

(which is inevitably present). A new approach for the removal of HCHO and benzene

simultaneously is proposed. The process combines both the benzene storage-oxidation and

formaldehyde oxidation processes. The catalyst proposed is work under room temperature and

elevated temperature. At room temperature, formaldehyde is oxidized to water and carbon dioxide,

while benzene is stored on the catalyst. The catalyst is regenerated by heating when the saturation

point of benzene storage is reached. During the regeneration phase, the catalyst activity will

increase with increasing the temperature and the stored benzene will completely oxidized to waterand carbon dioxide. The regenerated catalyst can then be used for a new cycle. In other word, the

catalyst for this process should not be only good for the oxidation of formaldehyde and storing of

benzene, but also the ability to oxidize the benzene at elevated temperature without release.

Nanoscale HZSM-5 zeolites is a promising catalytic and adsorbing material for this process with

reduced diffusion path lengths and higher surface area comparing to the conventional microscale

HZSM-5 zeolite. The overall adsorption capacity of HZSM-5 (15 nm) is about 50% higher than

HZSM-5 (>60 nm). Other studies was devoted to study PtM bimetallic catalyst (where M stands

for Fe,Pd,Ni, and Au) with enhanced catalytic performance. Furthermore, Ag shows a goodformaldehyde oxidation and benzene storing properties. A series of HZSM-5 with different crystal

size supported PtAg bimetallic catalysts were investigated at room temperature.


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Figure: Complete oxidation of HCHO to CO2over the PtAg/HZ-S , -M & -L

As the figure shows, PtAg/HZ with different surface adsorption site. Results showed at room

temperature PtAg/HZ-S had the highest formaldehyde conversion to CO2 then comes PtAg/HZ-M

& PtAg/HZ-L, respectively. With increasing temperature HCHO conversion increased rapidly.

The addition Pt and Ag has great influence on benzene adsorption on the zeolite .For temperature

higher than 100 Co, the catalyst start to generate and benzene start to oxidize. Complete oxidation

happen at 150 Cofor PtAg/HZ-S while higher temperature are required for complete oxidation for

both PtAg/HZ-M & PtAg/HZ-L, 165 Co & 190 Co respectively.

Figure: Complete oxidation of C6H6to CO2over the PtAg/HZ-S, -M & -L


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Adsorption capacity of PtAg/HZ-S is the highest among all of the catalyst studied. Also the results

showed that for non-supported HZ-S the capacity is 0.055 mmol/g.cat and increased by 70% in

the case of supported PtAg/HZ-S. The increase of storage capacity on PtAg/HZ can be attributed

to adsorption via "-complexation of Ag with benzene.

Figure: Comparison of C6H6storage capacity over the PtAg/HZ-S, -M & -L

Case study II: Catalytic oxidation of Benzene with ozone using zeolite supported metal oxides

nanoparticles (By Catalytic Today):

The following metal oxide (Co, Mn, Cu, Ce, Zn and Ni) were supported on H-ZSM-5 zeolite. At

ambient temperature (25 1#C), catalytic ozonation of benzene was carried out in a PBR.

Concentration of benzene and ozone, together with the humidity level, can be obtained at the

desired concentration. Some of the macro-pores of ZSM-5 were filled by metal oxides on the

supported ZSM-5, leading to the increased amount of mesoporous.


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Figure.12: Diagram showing Benzene OZCO system

Diffraction lines patterns to those of unsupported ZSM-5 and metal oxide showed quite similar

patterns, indicating that framework structure was reasonably remained even after ncorporation of

metal oxides. However, no significant diffraction peaks of metal oxides can be found in the

patterns of all the samples, indicating that metal oxides are highly and uniformly dispersed on the

support, as con-firmed by TEM. The time course for catalytic performance over various ZSM-5-

supported metal oxide catalysts.


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Figure.13: Time course for benzene oxidation over ZSM-5 supported metal oxide

In the absence of O3, benzene quickly appeared at the outlet after reaction for70 min due to the

gradual saturation of the sorption sites and no CO and CO2was generated. It is interesting to find

that the introduction of metal oxides on ZSM-5 can greatly promote benzene oxidation. The

metal oxides exhibited great difference in catalytic ozonation of benzene. Benzene removal

efficiency over them followed the order: MnO2> CoO > CuO > NiO > ZnO > CeO2. Benzene

appeared at the outlet of reactor after reaction for about 100 min and benzene removal efficiency

was dropped to nearly 0 after reaction for about 300 min. Benzene removal was attributed to notonly catalytic oxidation, but also the adsorption. The initial CO2concentration is only 120 ppm,

indicating that not all of the removed benzene was oxidized and some of them was adsorbed on

the surface of MnO2/ZSM-5. Besides the highest benzene removal efficiency, MnO2/ZSM-5 also

achieved the best CO2selectivity of 84.7%, followed by 63.8% over CoO, 52.5% over NiO and

36.6% over CuO.


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Figure.14: Benzene catalytic ozonation over ZSM-5 supported metal oxide

In this study, the CO2selectivity over MnO2/ZSM-5reached as high as 84.7% and no CO was

generated, indicating that most of the benzene was completely oxidized into CO2and few

intermediates was formed. This is important for its catalytic stability and industrial application

since the intermediates would bring new pollutants as well as block active catalytic sites for

benzene oxidation. It is considered that the key step of VOCs catalytic ozonation is the formation

of active oxygen species. Active oxygen species are necessary for benzene oxidation.


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Figure.15: Ozone decomposition rate over ZSM-5 supported metal oxide

It is clear that highly dispersed MnO2nanoparticles acted as the active centers for ozone

decomposition and benzene catalytic ozonation. ZSM-5 played a key role in ozone

decomposition. The active metal oxide and support synergistically work, which leads to the high

catalytic activity toward benzene catalytic ozonation. Benzene removal efficiency was not

always proportional to ozone decomposition efficiency over a specific metal oxide since the

adsorption also contributed to benzene removal besides catalytic ozonation in the initial stage. In

the case of MnO2, ozone decomposition efficiency was slowly decreased to 90% at 300 min,

while benzene removal efficiency could be kept the same (!100%).


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6.2 RECOVERY:

6.2.1 Adsorption of benzene by using ordered mesoporous carbon

(OMC):

Adsorption is a separation process where adsorbate will be attached on the surface of solid material

adsorbent (catalyst). After the reactant that we want to be reacted quickly is being attached on the

surface of the catalyst, then the activation energy will be lowered which will allow the reaction to

take place faster than if there was no catalyst. Desorption will take place after the end of the

reaction and the desired product will be collected. There are different factors that will affect the

rate at which the reaction will take place such as: catalyst surface area, pours size and the

adsorption amount. Carbon catalyst is made out many component including: coal, wood and peat.

This process is used for the disposal of VOC's, where benzene was used as the adsorbate and

ordered mesoporous carbon (OMC) as the adsorbent. Static adsorption measurement were

obtained at 298, 308 and 318 K, where the VOC's emissions were controlled by using turbo

molecular pump. OMC weight loss was obtained in temperatures greater than 373K. OMS was

used because of its excellent potential in the adsorption of VOC's. The reason why OMC had

excellent potential in the adsorption of VOC's is due to its large pour size, high surface area,

different available sizes, large volume of the porous and great recovery regime because of its fast

diffusion process. The proper OMC pour size was found to be (5-1.8) nm.

Table.5: The adsorption amount of benzene for different adsorbate temperature.


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7. CONCLUSION AND RECOMMENDATION:

In conclusion, benzene is major industrial compound and a health concern for the world.

Benzene can cause cancer and other major health effects. In order to control the benzene

emission, a number of controlling techniques were developed in order to keep the benzene

emission within the limits given by the countries regulations. In this report, we mainly

discussed controlling the benzene emission using catalytic oxidation. In this technique, we

explained two different case studies. In the first case study, controlling the benzene and

formaldehyde emission was discussed using PtAg/HZSM-5 catalyst. In this technique, we

found that using nanoscale HZSM-5 will improve the surface area and the adsorption

capacity comparing to the conventional microscale HZSM-5. Using three different

catalysts, PtAg/HZ-S, PtAg/HZ-M, and PtAg/HZ-L, we found that PtAg/HZ-S is the best

catalyst in term of highest conversion of formaldehyde at lowest temperature and also for

the benzene capacity and oxidation. In the second case study, we discussed about different

metal oxides supported on H-ZSM-5 zeolite for the controlling of benzene. We showed

that at room temperature, MnO2/ZSM-5 has the highest activity toward catalytic ozonation

of benzene and can remove the benzene completely at room temperature. This catalyst

shows high selectivity for CO2 of 85%. In order to compare these techniques with other

techniques of removing the benzene, we generate a figure showing the efficiency of these

techniques with the operating cost. The figure is shown below:


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,-./

The highest removal efficiency that can be obtained is 99% using Thermal Oxidation

or Membrane Separation, while the lowest removal efficiency is 60% using Bio-

filtration. Membrane Separation has the best efficiency per cost value. For Membrane

Separation,"#$%%&'&()'*+

"#',-.+= 0.6 .Thermal Oxidation has the lowest efficiency per cost

value. For Membrane Separation,"#$%%&'&()'*+

"#',-.+= 0.053. The highest cost of 120 $/cfm

came from Condensation and Absorption, but for the same price absorption gave better

efficiency (98%). The lowest cost of 10 $/cfm came from Activated Carbon.

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APPENDIX.1

Table.1: Physical properties of Benzene


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Table.4: Population-weighted personal exposure to benzene in five U.S. cities

Table.5: Outdoor concentration of benzene in three U.S. cities


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.

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.

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.

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.

5.

"Benzene Reactions.", Hydrogenation, Nitration, Sulfonation, Toxicokinetics. Web.

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6. "Benzene Safety Data Sheet." Total, 2012. Web. 3 Dec. 2015.

.

7. "EPA Sets Tier 3 Motor Vehicle."EPA Sets Tier 3 Motor Vehicle. EPA. Web. 12

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Khan, Faisal, and Aloke Kr. Ghoshal. "Removal of Volatile Organic Compounds

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15."Nanoscale HZSM-5 Supported PtAg Bimetallic Catalysts for Simultaneous

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