1CHAPTER -1INTRODUCTION

1.1 CATALYST:Automotive catalyst technology to meet ultra-low emission vehicle (ULEV)

emission levels for conventional gasoline fueled vehicles requires majorimprovements in catalytic activity and reactor engineering. A major challenge is inreducing vehicle cold-start emissions. ULEV emission levels can be exceeded inthe first minute of the Federal Test Procedure (FTP) cold-start if the catalyst doesnot achieve its light-off temperature. To achieve these cold-start emissionreductions, several approaches are actively being evaluated including electricallyheated catalysts 1-3, fuel burners 4, 5 and hydrocarbon adsorbers 6. Some of thesetechniques have demonstrated the ability to substantially reduce cold-startemissions; however, they also add substantial complexity and cost to the emissioncontrol system. Additional work has concentrated on the development of advancedcatalyst technology based on high loading of palladium 7, 8. These palladiumcatalysts have demonstrated improved warmed-up hydrocarbon activity and lowerlight off temperatures compared to conventional platinum/rhodium catalysts. Itmust be recognized; however, that automotive catalyst light-off during vehiclecold-start is a dynamic process dependent not only on catalyst activity but thetransfer of exhaust gas heat to the catalyst surface and the thermal mass of thecatalyst/substrate combination. A major limitation of conventional ceramic ormetal monolithic automotive catalyst technology is the large thermal mass

associated with the catalyst substrate 9. This result in a major delay in cold-startcatalyst light-off times due to the large amount of exhaust energy required to heatthe catalyst to reaction temperatures. The development of alternatecatalyst/substrate technology with reduced thermal mass, high heat transfer rates

2and high catalyst activity could result in significant advancements in achievingemission levels at and below the ULEV standard.

The reduction of Automobile pollution using catalytic converter in the latestvehicle speaks in high volume towards its successes. The uses of catalyticconverter are becoming compulsory for all the heavy vehicles in order to preventglobal warming. The modeling of catalytic converter as well as its simulation ofsurface reaction is very important to determine the conversion rate or the amountof pollutants reduction in the core of catalytic converter of the flue gasses from theengines. The catalytic converter model is simulating for the implementation of newcatalytic converter technology. For this aspect, the role of exhaust gas after

treatment method for the catalytic converter components is playing a very vitalacross the world.

`

FIG 1.1: CATALYTIC CONVERTER

31.2 MAIN POLLUTANTS IN THE EXHAUST OFGASOLINE ENGINES

Ideally, the emissions of an internal combustion engine only consist ofcarbon dioxide (CO2), water (H2O), and nitrogen (N2), when it is operated atstoichiometry. Under lean operation, i. e., with excess air, additional oxygen (O2)is emitted. Under rich operation, i. e., with excess fuel, mainly additional carbonmonoxide (CO) and hydrogen (H2) arise. In reality, the combustion is nevercomplete, since the air-to-fuel mixture is not entirely homogenous. Thus, the

gasoline is not entirely burned, resulting in carbon monoxide (CO), hydrogen (H2),and hydrocarbon (HC)2 emissions. The correct chemical expression for unburnedhydrocarbons is CxHy. For simplicity, the term HC will be applied throughout thethesis. Notice that here, only the compounds containing hydrogen and carbon areconsidered. In reality, other carbon-containing compounds are emitted, as well.However, they are not considered in this thesis. The term HC refers both to thesingular and plural form.

Since the combustion in the cylinder occurs at high temperatures, oxides ofnitrogen (NO, NO2 and very little N2O) are generated, as well. Their formation ishighly dependent on the operating condition of the engine. In the following, theywill be collected in the term NOx. All the emissions mentioned occursimultaneously, at any operable air-to-fuel ratio.

41.2.1 CARBON MONOXIDE (CO) AND HYDROCARBONS (HC)

Carbon monoxide is an odourless and colourless gas. Since it exhibits ahigher affinity to haemoglobin than oxygen, it is very toxic. It blocks the supply ofoxygen to the body tissue, thus leading to suffocation. A concentration of a fewthousand ppm is already fatal. Carbon monoxide is generated when the combustionoccurs under oxygen-deficient conditions. Thus, CO is mainly generated when richair-to-fuel mixtures are burned. However, even under lean conditions, CO occursbecause of incomplete combustion. The group of unburned hydrocarbons (HC)contains many compounds consisting of carbon and hydrogen. Themost importantgroups are alkanes, alkenes, alkynes, and aromatics. Molecules which only containsingle hydrogen-carbon bonds, i. e., the alkanes, are called saturated. Alkenesand alkynes are unsaturated. Hydrocarbons consist mainly of partially oxidisedfuel molecules.

However, few molecules arise from unburned fuel, such as benzene (C6H6).In addition to the hydrocarbons, oxygenates occur also, i. e., organic compoundscontaining oxygen, such as formaldehyde (HCHO). Usually their fraction is low ascompared to the HC concentration. Like CO, HC occur under rich operatingconditions, i. e., when excess fuel is present. Additionally, they occur when thecombustion is locally disturbed or hindered. This can for example be caused by thecylinder geometry, by quenching of the flame or by absorption of fuel in the oil.Alkenes and alkynes are slightly sweet smelling, whereas alkanes are odourless.Many HC cause coughing, drowsiness or even have a narcotic effect. Benzene istoxic and carcinogenic. It is believed that internal combustion engines in cars arethe cause of about 80% of the benzene in the atmosphere. Apart from the directimpact on the human health, some HC such as alkenes react with NOx in the

5atmosphere to form secondary pollutants such as tropospheric ozone andphotochemical smog. Ozone in turn has again a significant impact on the humanhealth, affecting the respiratory tract.

1.2.2 HYDROGEN (H2)

Hydrogen is not a real pollutant. It is not toxic and has no significantlymalign effect on the atmosphere. Therefore, it is not regulated by legislation. Itsvery high agility as compared to other species and its considerable chemicalactivity are the causes of these sensor signal distortions.

1.2.3 NITROGEN OXIDES (NOX)

Nitrogen Oxides mainly occur in the form of nitric oxide (NO) and nitrogendioxide (NO2). Nitrous oxide (N2O) only occurs in small amounts in the rawemissions of an internal combustion engine. However, the concentration mayincrease in a three-way catalytic converter under certain circumstances. Nitrogendioxide is reddish-brown with a pungent smell and toxic, damaging the lung tissue.Already small concentrations of around 1 ppm are harmful. Nitric oxide isodourless and colourless and relatively harmless, as compared to NO2. Both NOand NO2 play an important role in the formation of acid rain, photochemical smogand the depletion of the ozone layer. Nitrous oxide is an important greenhouse gas.Usually, the fraction of NO in the NOx emissions of a gasoline engine is wellabove 98%. Therefore, only NO will be considered, the other nitrogen oxides willbe neglected in this thesis.

61.3 CATALYTIC CONVERTER:

Catalytic converters, fitted in series with the exhaust pipe of gasoline fueledvehicles, convert over 90 percent of hydrocarbons (HC), carbon monoxide (CO)and nitrogen oxides (NOx) from the engine into less harmful carbon dioxide(CO2), nitrogen and water vapour. Since catalytic converters were first fitted tocars in 1974, more than 12 billion tons of harmful exhaust gases have beenprevented from entering the earths atmosphere. More than 96 percent of cars

manufactured today are equipped with catalysts. A catalytic converter(colloquially, "cat" or "catcon") is a device used to reduce the toxicity of emissionsfrom an internal combustion engine. Catalytic converters are also used ongenerator sets, forklifts, mining equipment, trucks, buses, trains, and other engine-equipped machines. A catalytic converter provides an environment for a chemicalreaction wherein toxic combustion by-products are converted to less-toxicsubstances.

1.4 ZEOLITE (ZSM-5):ZSM-5, Zeolite Socony Mobil5, (framework type MFI from ZSM-5 (five))

is an aluminosilicate zeolite belonging to the pentasil family of zeolites.Its chemical formula is NanAlnSi96nO19216H2O (0

7FIG 1.2 : A typical zeolite structure

1.4.1 POTENTIAL APPLICATIONS:

GENERAL APPLICATIONS:Zeolites have a wide range of commercial uses (InterSun 2007), including:

AQUACULTURE: Ammonia filtration in fish hatcheries

Biofilter media

AGRICULTURE: Odor control

Confined animal environmental control

Livestock feed additives

8HORTICULTURE: Nurseries, greenhouses

Floriculture

Vegetables/herbs

Foliage

Tree and shrub transplanting

Turf grass soil amendment Reclamation, revegetation, and landscaping

Silviculture (forestry, tree plantations)

Medium for hydroponic growing

HOUSEHOLD PRODUCTS: Household odor control

Pet odor control

INDUSTRIAL PRODUCTS: Absorbents for oil and spills

Gas separations

ENVIRONMENTAL APPLICATIONS:Although environmental applications of zeolites are small compared with

applications of their catalytic properties, considerable research and someimplementations have taken place including:

RADIOACTIVE WASTE: Site remediation/decontamination

9WATER TREATMENT: Water filtration

Heavy metal removal

Swimming pools

WASTEWATER TREATMENT: Ammonia removal in municipal sludge/wastewater

Heavy metal removal

Septic leach fields

SYNTHESIS:

ZSM-5 is a synthetic zeolite, closely related to ZSM-11. There are manyways to synthesize ZSM-5, a common method is as follows:

SiO2 + NaAlO2 +NaOH +N(CH2CH2CH3)4Br +H2O ZSM-5 + analcime+ alpha-quartz

ZSM-5 is typically prepared at high temperature and high pressure ina Teflon-coated autoclave and can be prepared using varying ratios of SiO2 and Alcontaining compounds.

ZSM-5 SPECIAL PROPERTIES

Zeolite ZSM-5 is a special type of zeolite. It is a "high-silica"- zeolite, whichgives it most of its special properties. Zeolite ZSM-5 is moderately hydrophilic tohighly hydrophobic (depending on the Si/Al ratio), whereas zeolites like the typesA, X and Y are very hydrophilic. The number and type of cations compensatingthe lattice charge are an important factor as to this property. Zeolite ZSM-5 has a

10

very high temperature (>1000C) and acid stability (down to pH=3). The lastproperty makes it possible to obtain the hydrogen form directly by exchanging thezeolite in a dilute hydrochloric acid solution without large Al-losses. To convertthe "low-silica"-zeolites to the hydrogen form they have to be exchanged with anammonium salt solution and then calcined to decompose the ammonium ions.

The ZSM-5 structure allows the introduction of alternative T-atoms (B, Ga,Fe etc.) during synthesis. The structural properties of the zeolite remainunchanged, just the unit cell dimensions change slightly. Passage of highersubstituted aromatics (when formed at an intersection) is even more limited, sothese will probably be converted before leaving the zeollte. Therefore, alkylatipnof toluene with methanol and disproportionate of toluene will yield a xylenesmixture with a higher p-xylene content than the thermodynamic equilibrium. Thecatalytic dewaxing of heavy oil fractions is a (hydro-) cracking process in whichonly the linear ("waxy") hydrocarbons are involved. Branched hydrocarbons aretoo large to enter the zeolite's pores. The products of a dewaxing unit are a fractionwith a boiling range comparable to that of the feed fraction 'and a gasoline fraction.The pour point of the gas-, fuel- or lubricating oil will be lowered (e.g. for alubricating oil from 7C to -12C and for a middle distillate ' from 32C to -18C),which drastically improves the properties of these oils at low temperatures.Dewaxing of gas oil (diesel fuel) lowers the temperature at which "fogging"occurs. This phenomenon is encountered during the winter when the linearparaffins form clouds and plug the fuel lines of the car. In this thesis the uniquecatalytic properties of ZSM-5 type zeolites will be demonstrated in two.

New gas phase reactions, namely the conversion of ethanol and ammonia topyridines and the ammoxidation of toluene to benzonitrile.Further chaptersdescribe the detection and analysis of ZSM-5 zeolites using infrared spectroscopy

11

and experiments on the synthesis of zeolite ZSM-5 using a range of templates anda range of substituting T-atoms introduced during synthesis. Some data will begiven on experiments with molecular ..' sieves from the SAPO- and MeAPO group,as these systems might offer the possibility of synthesizing materials with anionexchange properties (here the lattice has to carry a surplus of positive charge). Itwill be shown that the SAPC type materials can be effectively used in thecatalytic ammoxidation of toluene

RADIONUCLIDE APPLICATIONS:

As a potential remedial measure, the zeolite clinoptilolite was tested in agreenhouse pot experiment for its effectiveness in selectively taking up cesium

from two British soils: a lowland loam and an upland peat. Rye-grass grown on10% clinoptilolite-treated soils resulted in grass leaf tissue cesium concentrationsbelow 30 mg Cs kg-1 grass in all cases. Where no clinoptilolite had been added,cesium in grass leaf-tissue reached 1,860 mg kg-1 in rye grown on peat and 150mg kg-1 in rye grown on loam. In contrast, the addition of calcium carbonate to theCs treated, clinoptilolite-free peat soil enhanced the grass concentration of Cs byapproximately five times, but this effect was not observed with the concentrationof Cs in grass grown from loam soils with the same treatments. However, despitethis apparent beneficial result of adding the zeolite, adverse side effects wereobserved. Since the zeolite is in the sodium form, sodium ions are released and therisk of sodium toxicity to plants increases as cation exchange proceeds. Further,since clinoptilolite binds heavy metals in general, essential heavy metals (such aszinc) would be markedly decreased by the application of zeolite, which in turncould result in deficiency problems in animals. It was also noted that since grazinganimals consume a 62 considerable amount of soil in their diet, the consumption of

12

radionuclide-laden zeolites could itself bring risks. In general, it has been notedthat the main research behind the use of natural zeolites as a remediation tool forcontaminated soil has been conducted largely through laboratory and greenhousetrials. There is very little evidence in the literature to support the long-term use ofnatural zeolites in real remediation projects (Stead et al. 2000). It was also notedthat the future potential of using zeolites has not been fully appreciated, and thatthere is an urgent need to undertake field trials and evaluate the in-situ efficiencyfor these remediation purposes. Since zeolites are natural materials and are mainlyused in industrial processes, little research is focused on their fate and transport,though an extensive volume of work exists on their geological origin and behavior.Extensive data exists on operation and maintenance parameters. As would beexpected, specific details are highly dependent on waste streams involved. Threereferences (IAEA 1967, IAEA 1984, IAEA 2002) discussed below provide anexcellent overview of the issues involved.

IMPACTS, HAZARDS, EFFICACY AND LIMITATIONS:

Zeolites are a bulk commodity. World production is on the order of 4 milliontons per year, with China producing and using about 2.5 million tons (primarily asa low-grade additive to pozzolan cement); U.S. consumption is about 0.5 milliontons. The primary industrial use is as a petrochemical catalyst and the secondlargest use is as a detergent builder. Thus, the use of zeolites in radionuclideremediation would be expected to have little impact. Most zeolites, particularlythose with current widespread uses, are regarded as a safe material; they arecurrently being marketed as a health food and references to their medicinal usedate back thousands of years. Zeolites are also used as a feed additive for cattle,

13

pigs, chicken, and fish. It should be noted, however, that one zeolite, erionite, isregarded as a carcinogen due to its fibrous nature and high iron content. Regardingefficacy, though zeolites have had limited uses in environmental remediationoutside of their use in the nuclear industry as an ion exchanger for liquidradioactive waste management, they are seen as having significant potential. Eventhe drawbacks mentioned in the work of Campbell and Davies (Campbell andDavies 1997) should be surmountable. To eliminate the sodium toxicity risk tosoil, the zeolite could be preconditioned into the ammonium form, which wouldlikely lead to plant growth improvements. Overcoming the concern of nutritionallyimportant soil nutrients binding together would require that the zeolite used(possibly synthetic) would be designed to have a very high specificity for the targetradionuclide and little else. Alternatively, soil quality could easily be monitoredand appropriate amendments made.

14

CHAPTER-2

LITERATURE REVIEW

Zeolites are one of the few nanotechnologies that have been investigated forenvironmental remediation purposes. Because of their ion exchange properties, andthe fact that they are a seemingly benign natural product that can bring certainimprovements (such as increasing the soil cation-exchange capacity and soilmoisture, improving hydraulic conductivity, increasing yields in acidified soils,and reducing plant uptake of metal contaminants) to soil properties (Allen andMing 1995), zeolites have been examined for their ability to remediate heavymetals in soil (Weber etal. 1984).

The origin of this work was the observation that radioactive cesium (137Cs)from the Chernobyl accident of 1986 has unexpectedly remained in a bioavailableform in upland, sheep-grazing soils of Great Britain.

Based on this work, Campbell and Davies (Campbell and Davies 1997)performed an experimental investigation of plant uptake of cesium from soilsamended with clinoptilolite and calcium carbonate.

In 1994, Francois et al. used star and rod-coil polymers to obtain the honeycombfilm by the BF method. At the beginning, the work in this field mainly focused onchanging polymers, solvents and substrates to achieve all kinds of honeycombstructure films.

15

CHAPTER -3

3.1. COMPONENTS USED:

3.1.1. TEST VEHICLE:

The test vehicle chosen for this project was a 2011 Maruti Suzuki EECOcertified to the low emission vehicle (LEV) standards. Specifications for the engineare listed below:

Engine Type Overhead-cam in-line 4 cylinder with OBD II

Displacement 2.0 liter

Valves 16

Horsepower (SAE net) 110 @ 5,000 rpmTorque (SAE net lb.ft.) 125 @ 3,750 rpm

Fuel system Sequential electronic fuel injectionEngine control EEC-V computer

FIG 3.1: TEST VEHICLE

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3.1.2. CATALYTIC CONVERTER:

Selection of catalytic converter also plays a key role in our project. Catalyticconverter which we selected for our project is petrol engine catalytic converter.Reason behind this is that only petrol engine shows the exact composition ofexhaust impure gases during emission testing.

3.1.3. ZEOLITE ZSM-5:

FIG 3.2: ZEOLITE ZSM -5 SAMPLE

Zeolites are crystalline aluminosilicates, compositionally similar to clay

minerals, but differing in their well-defined three-dimensional nano- and micro-porous structure. Aluminum, silicon, and oxygen are arranged in a regular structureof [SiO4]- and [AlO4]- tetrahedral units that form a framework with small pores(also called tunnels, channels, or Cavities) of about 0.1-2 nm diameter runningthrough the material.

17

3.1.4. MULTIGAS ANALYSER:

TECHNICAL SPECIFICATIONSMEASURED GAS

HC HydrocarbonsCO Carbon MonoxideCO2 Carbon DioxideO2 Oxygen

CO(%) CO2(%) HC(ppm) O2(%)RANGES 0 to 10 0 to 20 0 to 10000 0 to 25

ACCURACY /PERFORMANCE

0.02 0.30 8 0.10

RESOLUTION 0.01 0-1 1 0.01RPM 0 - 10,000 rpm with DIS/Wankel and 4 stroke selection

OIL TEMPERATURE 0 120 C

TABLE 3.1: MULTIGAS ANALYSER SPECIFICAITON

LAMBDACalculated using Brett Schneider formula.Resolution 0.001Fuel type selection: Unleaded Petrol, L.P.G. or C.N.G.

ENVIRONMENTALOperating temp. +5 to +40 CStorage temp. -20 to +55 C

18

WARM-UP TIME

19

CHAPTER -4

4.1 METHODOLOGY:

CATALYST

PROBLEM IDENTIFICATION AREA

CATALYTICCONVERTER

COATINGTECHNIQUE

PETROLENGINE

CATALYTICCONVERTER

ZEOLITE(ZSM-5)

DIPCOATING

TECHNIQUE

COATINGPROCESS

RESULTS ANDDISCUSSSIONS

CONCLUSIONS

EMISSIONTESTING

20

STAGE I :

4.1.1 CUTTING PROCESS:

FIG 4.1 CUTTED SHIELD

Cutting processes work by causing fracture of the material that is processed.Usually, the portion that is fractured away is in small sized pieces, called chips.Common cutting processes include sawing, shaping (or planing), broaching,drilling, grinding, turning and milling. Although the actual machines, tools andprocesses for cutting look very different from each other, the basic mechanism forcausing the fracture can be understood by just a simple model called fororthogonal cutting.

A hand cutter is used to cut the catalytic converter shield. After cutting it,honey comb structure (ceramic monolith) is taken out for coating purpose.

21

HONEYCOMB STRUCTURE (CERAMIC MONOLITH):

FIG 4.2 : HONEYCOMB STRUCTURE

Honeycomb structures are natural or man-made structures that have thegeometry of a honeycomb to allow the minimization of the amount of usedmaterial to reach minimal weight and minimal material cost. The geometry ofhoneycomb structures can vary widely but the common feature of all suchstructures is an array of hollow cells formed between thin vertical walls. The cellsare often columnar and hexagonal in shape. A honeycomb shaped structureprovides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties.

Man-made honeycomb structural materials are commonly made by layering ahoneycomb material between two thin layers that provide strength in tension. Thisforms a plate-like assembly. Honeycomb materials are widely used where flat orslightly curved surfaces are needed and their high Specific strength is valuable.They are widely used in the aerospace industry for this reason, and honeycombmaterials in aluminum, fibre glass and advanced composite materials have beenfeatured in aircraft and rockets since the 1950s.

22

STAGE II:

4.1.2 COATING REMOVAL PROCESS:

SODIUM HYDROXIDE:

FIG 4.3: SODIUM HYDROXIDE

Concentrated sodium hydroxide solution is used to remove the PGM. Thecomposition ratio of NaOH solution and water are 2:1. The ceramic is made toimmerse in mixture for the time period of 30 minutes. Then it is washed in waterand then heated in the oven at a temperature of c0200 for the time period of 1 hour.

23

STAGE III:

4.1.3 COATING PROCESS :( ZSM-5)

FIG 4.4: COATING METHOD

Catalytic converters are used in automobile and industries for pollutionabatement. They usually consist of cordierite ceramic extruded to form a structureof honeycomb-like cells that extend as channels along the catalytic converterlength. A paint-like liquid containing the precious metal catalyst is coated on thechannel walls. During operation, exhaust gases are conveyed with low pressuredrop through the catalytic converter. The pollutant gases are removed by catalyticactivity in the catalyst coating. Monolithic catalytic converter substrates are shownin the picture above.

Coating processes for catalytic converters present several challenges thathave been tackled in the visual analysis lab. Catalytic converter manufacturers

24

complained that quality control of catalyst coat thicknesses is difficult. In additionthe coating liquid often clogs several of the catalytic converter channels. Usually,the monoliths are sprayed with a non-viscous solution containing dissolvedcatalyst. Sometimes the monoliths are coated by dipping into a catalyst enrichedslurry and then blowing out the slurry with air. The air clears the channels leavinga layer of deposited slurry solids on the channel walls. A solid coat of catalyst,called the washcoat, is left after the liquid components dries out. A third method isto suck the slurry through the monoliths by lowering one end of the monolith into acatalyst slurry and applying a vacuum at the other end of the monolith. Thisvacuum coating method has been the focus of our research and is illustrated below.

DIP COATING:The ceramic monolith was then coated with the metal catalyst via dipping

technique. In this process ceramic monolith was immersed into prepared catalystslurry for the duration of 50 minutes. Then the coated ceramic was removed fromcatalyst slurry to be blowered using air at the speed of 10 l/min until the unwantedresidual catalyst was evaded from the surface of the stainless steel wire mesh.After blowered process, coated honeycomb structure was dried in an oven attemperature 120C for 120 h before being calcined in a muffle furnace.Calcination is a process in which a material is heated to a high temperature withoutfusing, so that hydrates, carbonates, or other compounds are decomposed and thevolatile material is expelled. Calcinations take 60 hours at a temperature of 550Cwith temperature ramping upon 100C/min and holding time of a 300 minutes.After the calcinations process the ceramic monolith were arranged into straight barto become a substrate for use as a catalytic converter.

25

FIG 4.5 COATED HONEYCOMB STRUCTURE

COATING:The coating of a catalytic converter can be considered as a chemical plant inminiature, where toxic gases are converted into non toxic ones There are twodistinct parts to the coating. The first of these is known as the washcoat, the

purpose of which is to provide the maximum possible surface area for reactions totake place. To extend the analogy of the chemical plant, the washcoat would be thefactory floor. If examined under a very powerful microscope, a good washcoat

26

appears extremely rough, a bit like sandpaper. The surface area of a washcoat is agood indicator of how effective a catalytic converter will be, and a high qualitymodern washcoat can provide amounts of surface area which are difficult tocomprehend for a non-chemist. For example, a washcoat providing less than 100square metres of surface area per gram of weight would not meet the grade formost OEM catalytic converters. Most washcoats consist primarily of alumina,however ceria is also a common addition as are various chemicals known as rareearths. Although, as mentioned above, the primary purpose of the washcoat is to

provide a large surface area, the ingredients of the washcoat also play an importantpart in the chemical reactions which take place on its surface.

The second stage of the coating is the application of precious metals to thewashcoat, usually from the platinum group. These metals play a critical role in the

oxidation and reduction reactions which the catalytic converter is designed topromote. Oxidation reactions are normally promoted by platinum, palladium or amixture of the two, whilst rhodium is used to promote reduction reactions.

27

STAGE IV:

4.1.4 GAS WELDING PROCESS:

FIG 4.6: GAS WELDED CATALYTIC CONVERTER

It is a fusion welding in which strong gas flame is used to generate heat and raisetemperature of metal pieces localized at the place where joint is to be made. In thiswelding metal pieces to be joined are heated. The metal thus melted starts flowingalong the edges where joint is to be made. A filler metal may also be added to theflowing molten metal to fill up the cavity at the edges. Different combinations ofgases can be used to obtain a heating flame. The popular gas combinations are oxy-hydrogen mixture, oxygen-acetylene, and etc. different mixing proportion of twogases in a mixture can generate different types of flames with differentcharacteristics.

After coating process, coated honeycomb structure is placed inside thecasing. Then the casing is welded with the help of gas welding process.

28

CHAPTER -5

5.1 RESULTS AND DISCUSSIONS:

5.1.1 RESULTS REGARDING PGM COATED CATALYTICCONVERTER:

CO(%BYVOL.)

HC (PPM) 2CO (% BYVOL.)

2O (% BYVOL.)

TRIAL 1 1.13 121 13.5 26.04

TRIAL 2 1.15 230 13.6 26.95

TRIAL 3 1.50 280 14 29.05

TRIAL 4 1.89 130 13.8 28.20

TRIAL 5 2.28 143 14.89 28.56

Table 5.1 Results for PGM Catalyst

29

FIG 5.1: GRAPH FOR PGM CATALYST

Before coating, vehicle is initially tested with PGM coated catalyticconverter. The results are shown in above table and graph. The optimal level forCO is 3% by volume. It remains under the optimal level. But it keep on increasingfrom lower to higher level. HC also under optimal level. But CO2 and O2 increasesabruptly.

5.1.2 RESULTS REGARDING ZSM -5 COATED CATALYTICCONVERTER:

CO(% BYVOL.)

HC (PPM) 2CO (% BYVOL.)

2O (% BYVOL.)

TRIAL 1 0.16 148 0 20.98

TRIAL 2 0.36 232 14 30.01

TRIAL 3 0.25 280 0.9 28.65

TRIAL 4 0.51 214 0.5 23.03

TRIAL 5 0.82 275 0.8 22.98TABLE 5.2: RESULTS FOR ZSM -5 CATALYST

050

100150200250300

TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5

COHCCO2O2

30

FIG 5.2 : GRAPH FOR ZSM -5 CATALYST

After coated with zeolite ZSM -5, once again catalyticconverter is tested for emission and its results are listed above in the form of tableand graph. In the above result, CO decreases abruptly. But HC cannot be able toreduced. On the other hand, CO2 and O2 decreased in volume.

0

50

100

150

200

250

300

TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5

COHCCO2O2

31

CHAPTER -6

6.1 CONCLUSIONS:

The following conclusions may be drawn from the present study.

Zeolite ZSM -5 catalyst based catalytic converter has beensuccessfullydeveloped.

The CO conversion efciency of catalytic converters are 25% than currentcoated catalytic converter.

The HC conversion efciency of OEM and wire mesh catalytic convertersare increased by 27%.

The CO2 conversion efficiency is 25% more than current catalyst coatedcatalytic converter.

The O2 conversion efficiency is increased by 90%.

32

CHAPTER -7

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