Investigation of performance characteristics of catalyticconverter made from selective transient metals under different

engine operating conditions of four stroke petrol engine

A Synopsis submitted to Gujarat Technological University

In

Mechanical Engineering

By

Charula H. PatelEnrolment No. 129990919002

Under supervision of

Dr Nilesh M BhattProfessor and Head, Mechanical Engineering Department

L. D. College of Engineering, Ahmedabad

Under co-supervision of

Dr. Srinivas PalankiRegional Director and Professor,

College of Engineering, Lamar university

GUJARAT TECHNOLOGICAL UNIVERSITYAHMEDABAD

FEBRUARY 2020

1

Title of thesis: Investigation of performance characteristics of catalytic converter made from

selective transient metals under different engine operating conditions of four stroke petrol engine

1. Abstract:

Vehicle numbers and their variants are on the rise with every passing day because of

increasing population and an affluent lifestyle. These vehicles emit pollutants due to incomplete

combustion of fuel air mixture in the engine and is sharing one third of total air pollution. Carbon

monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx) are the main pollutants

from petrol engines. These pollutants cause adverse effect on air quality which results in damaging

prospects of wellbeing creatures as well as nature. Hence it is required that stick vehicular emission

norms are followed. To meet these standards the most widely used methods is Three Way Catalytic

Converter (TWCC), which contains Platinum group metals (PGM) as catalyst for emission

reduction. Such catalysts, in order to work effectively, are required to reach at temperature of about

350oC for light-off to occur and they require to be working at stoichiometric A: F ratio. Also

because of higher cost of PGM, environmental effect of PGMs and as considerable advancement

has been made in metal oxide preparatory methods, metal oxide catalysts have gained more

attraction recently. Transition metal oxides are less expensive than the noble catalyst. Among

them, manganese oxide (MnOx) has displayed impressive oxidation reduction reactions at lower

temperature, and seems to be as suitable contender of Oxygen Storage Capacity (OSC) and

environment friendly. Cobalt oxide (CoOx) has displayed excellent catalytic activity for HC and

CO oxidation.

This research investigates performance characteristics of catalytic converter made from

cobalt oxide and manganese oxide as catalyst as a substitute to PGM. Experimentation work has

been carried out in two parts, first catalytic converter development and second catalytic converter

engine test. For catalyst preparation cobalt oxide and manganese oxide in the ratio of 5:1 were

taken based on Pt:Rh ratio of 5:1 in PGM based catalyst. Mixed oxide catalysts were prepared by

Co-precipitation method. Cylindrical shaped Ceramic monolith (2MgO.2Al2O3.5SiO2) having 600

CPI with active surface was coated with the Cobalt oxide and Manganese oxide (Co:Mn) catalyst.

16.8 % wt. loading of Co:Mn catalyst was taken for experimentation. Converter coated with PGM

catalyst (commercially available) was prepared for base line data (reference) and to assess the

effect of Ce and Pt doping on catalyst performance, converters coated with catalyst having

proportion of Co:Mn:Ce = 5:1:1 (molar ratio), Co:Mn = 5:1 doped with Pt. 0.12 % wt. Pt.(0.168

2

g/monolith) and Co:Mn:Ce = 5:1:1 doped with Pt. 0.12 % wt. Pt. (0.168 g/monolith) were also

prepared.

A four-stroke petrol engine equipped with transition metal oxide catalytic convertor was

tested for different catalyst converter performance parameters under different engine operating

conditions, including catalyst efficiency, Light-off temperature (LOT), effect of Air: Fuel (A: F)

ratio and OSC. From the engine test results it was found that with Co:Mn catalyst, 50% HC

conversion was achieved at 195°C (LOT) in 120 s and 80% conversion efficiency - lambda

window is 0.294 whereas PGM coated converter gives 50% HC conversion efficiency at 273°C

(LOT) in 179 s and 80% conversion efficiency- lambda window is 0.147. With Co:Mn:Ce coated

catalytic converter, 50% HC conversion was achieved at 195°C (LOT) in 120 s and 80%

conversion efficiency - lambda window is 0.277. With Co:Mn:PGM coated catalytic converter

50% HC conversion was at 190°C (LOT) in 108 s and 80% conversion efficiency -lambda

window is 0.294. With Co:Mn:Ce:PGM coated catalytic converter, 50% HC reduction efficiency

was at 189°C (LOT) in 106 s and 80% conversion efficiency- lambda window is 0.279. Engine

speed and ignition angle effects the engine emission, however under normal running condition

converter is fully warmed up and not affect the conversion efficiency.

2. Brief description on the state of the art of the research topic:

TWCC comprises of noble metals such as Platinum (Pt), Palladium (Pd), Rhodium (Rh) as

a catalyst for emission reduction (Kaspar et al., 2003, Gandhi et al., 2003). These catalysts convert

CO, HC and NOx from vehicle exhaust into the harmless carbon dioxide (CO2), nitrogen (N2), and

water (H2O) (Barefoot, 1997; Palacios et al., 2000; Kielhorn et al., 2002; Morcellia. et al., 2005).

Rhodium is NOx reduction catalyst on which NOx and CO are abolished together by a redox

reaction. NOx oxidizes CO to CO2 and is reduced to harmless nitrogen gas (N2), during the time

CO and HC are oxidized on platinum catalyst (Kaspar et at., 2003; Heck and Farrauto, 2001).

These simultaneous oxidizing and reducing reactions have the highest efficiency in the small

window of A: F ratio of around stoichiometric value. To consider dynamic driving condition A:F

ratio around stoichiometric (operating window) required to widen up for catalyst operation. These

can be accomplished by controlling engine exhaust on catalyst by adsorbing oxygen in the

oxygen-rich (lean) condition and by liberating it in the oxygen-lean (rich) condition (Kaspar et al.,

2003). This could be accomplished by adding an oxygen storage component in a Three-Way

Catalyst (TWC) which shows high OSC. CeO2 has been found as an efficient and an appropriate

oxygen storage component for TWC (Bera and Hedge, 2001). These catalysts are required to reach

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350°C for Light-off to occur and requires working at stoichiometric A: F ratio. A majority of

hydrocarbon emissions (60–80% of the total emitted) are produced in the cold start of the

automobile, i.e. in the first 2 min of operation (Heck and Farrauto, 2001; Shelef and McCabe,

2000). Also, because of the high cost of PGMs, transition metal oxide catalysts have been drawing

more interest in recent years.

Amongst the transition metal oxides (TiO2, MnOx, CoOx, NiO, CuO), MnOx and CoOx are

known as active catalysts for oxidation reduction reaction and are ecofriendly (Krylov, 1970;

Stobbe et al.,1999; Radwan et al., 2004; Aguera et al.,2009). MnOx and CoOx demonstrated their

superiority for CO oxidation (Krylov, 1970) and Volatile Organic Compounds (VOCs) (Aguera et

al., 2009; Garcia et al., 2011) oxidation. Several investigations demonstrated superior activity of

MnOx for CO oxidation among the transition metal oxide catalyst (Krylov, 1970; Cimino et al.,

2002). Catalytic performance for CO oxidation was investigated on unsupported manganese

oxides (MnOx) catalysts (Brook, 1967; Cracium et al., 2003; Han et al., 2003, 2006).

CO oxidation over various manganese oxide catalysts was studied by Yi- Fan et al. (2003)

and observed reaction temperature less than 254°C. MnOx is known to be exhibiting significant

catalytic performance for oxidization of CO by O2 at low temperature (Han et al., 2003; Iablokov

et al., 2010; Zhang et al., 2011; Zaki et al., 1998). Many transition metal oxides have been used to

improve the low-temperature activity. Among them special attention has been gained by

manganese oxides because of their various types of labile oxygen, which is necessary to complete

the catalytic cycle and resulting in a substantial improvement of the low temperature catalytic

activity (Smirniotis et al., 2001; Wallin et al., 2004; Chen et al., 2012; Shen et al., 2013). Chang

and McCarty (1996) proposed the use of MnOx in TWC to enhance their performance for oxidation

of HC or CO. Investigation revealed that manganese oxide supported Al2O3 catalyst was

appropriate to remove VOCs from gas mixture, the temperatures were practically similar to that

of the component which was most hardly oxidized (Aguera et al., 2009). Manganese oxide

catalysts were studied on silica support and found remarkable results in VOC conversion (Reed et

al., 2005). Presence of MnOx in the compound increases the concentration of oxygen vacancies

(Hong et al., 2011), which is helpful to the adsorption of CO (or HC) and the dissociation of NO,

and play important role in NO decomposition activity (Wu et al., 2007; Xiaojiang et al., 2014;

Hong et al., 2011; Liu et al., 2010). Catalyst activity of MnOx was extensively studied for NO

reduction with NH3 and it has reported good catalyst activity at low temperatures. A good activity

at low temperature is attributed to its ability to form various oxidation states of Manganese and

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labile lattice oxygen, which is important to complete the catalyst cycle (Casapu et al., 2009; Wu

et al., 2008). Many researchers have projected the use of MnOx as an agent for OSC for TWCC

(Stobbe et al., 1999; Chang et al., 1996; Shi et al., 2007).

Catalytic combustion of CO is an important reaction in a TWCC. Cobalt oxides showed

excellent catalytic performance for CO oxidation at low temperature (Krylov 1970; Ma 2014),

which attributed to the disparity in the structure of the cobalt oxide. An active form of cobalt oxide

exists in two valence states (+2 and +3), activity value confirms that the cobalt oxide is a highly

active catalyst for CO oxidation. Highest turnover frequencies over noble metals amount to 1-10

s-1 at 523 K, i.e. 22-220 molCO2 s-1 m-2. The Intrinsic activity of cobalt oxide is very close to that

of noble metals (Royer and Duorez, 2011). Many researchers studied VOC oxidation reaction

over CoOx on different support like silica (Todorova et al., 2011), alumina (Papaefthimiou et

al.,1997) and reported remarkable performance. Gomez et al. (2014) prepared CoOx/ La modified

CeO2 catalyst and tested for catalytic VOCs oxidation and found that LOT was around 40°C below

that of Pt.

Synergetic effect of MnOx and CoOx mixed metal oxide catalysts can be a good alternative

of commercially available PGMs catalyst and have the potential of being used as a catalyst in the

TWCC for emission reduction. Further efforts should be to fully elucidate the potential of MnOx -

CoOx catalyst in the TWCC so that we can approach eventual low emission at minimum catalyst

cost.

3. Definition of the problem:

Enormous research has been done on TWCC; research reveals that:

(1) Platinum group metals have the common properties like inert as regards biological

reactions or less chemical reactions; and to be immobile. The Palladium and Platinum ions are

binding to lead within the catalytic converter and the complex is being released as a solid in the

exhaust into the environment. Platinum content of road dusts can be soluble and consequently it

enters the waters, sediments, soil and finally the food chain. PGMs have also been associated with

asthma, nausea, increased hair loss, increased spontaneous abortion, dermatitis and other serious

health problems in humans.

(2) Conventional catalytic converter does not function efficiently until its operating

temperature is sufficiently high, generally 350°C LOT, large portion of HC emission occurs (60-

80%) during cold start period of about first two minutes.

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(3) Because of rareness of Platinum group metals, catalytic converter become most

expensive device in vehicle.

The above mention factors for conventional catalytic converter motivate to develop

catalytic converter from selective transient metals (base metal oxides) and investigate performance

and behavior of catalytic converter made from base metal oxides under different operating

condition of engine to ensure suitable efficiency.

4. Objective and scope of the work:

Aim of the work is to fully exploit the potential of Cobalt oxide and Manganese oxide

(Non-Platinum group metals) in a three-way catalyst to meet the current and future demand of

emission reduction.

Specific objectives of work are as follows:

To investigate performance characteristic of catalytic converter made from cobalt oxide

and manganese oxide as catalyst.

To determine effect of different engine operating condition on conversion efficiency.

To determine Light-off temperature (LOT) and Oxygen Storage Capacity (OSC) of the

catalytic converter.

Scope of the work:

Present work investigates the performance characteristics of catalytic converter made from

selective transient metals under different engine operating conditions. It is plan to investigate

performance parameters of PGM catalytic converter; this will be providing a guideline for the

catalytic converter made from the metal oxides. It is also planned to assess the oxidising and

reducing metal oxides as catalyst for TWCC considering its redox behaviour, conversion

efficiencies, LOT, OSC, catalyst ratio, catalyst preparation method coating methods. This will be

useful to prepare metal oxide catalyst, its preparation method and decide the catalyst ratio. Engine

test setup with five gas analysers, scanner and lambda sensors will be used to investigate metal

oxide catalyst converter.

5. Original contribution by the thesis:

An extensive and comprehensive literature review is undertaken in order to identify the

research gaps and research issues in the field of catalytic converter. The oxidising and reducing

metal oxides as catalyst for TWCC are assessed considering their redox behaviour, conversion

6

efficiencies, LOT and OSC. Different samples of catalyst were prepared in laboratory as per the

stoichiometric calculation of catalyst. Catalyst samples were get tested to fix calcination

temperature during the catalyst preparation (development) phase. Among the commercially

available different shaped ceramic monolith, round shape monolith was selected as it causes less

can deformation and have uniform holding pressure. Monolith size was fixed based on engine

suction capacity. Selected ceramic monoliths were coated with different catalyst and then canned

to fit engine exhaust manifold for testing. Engine test setup is prepared for testing, programmable

ECU is used to test conversion efficiency at different lambda values. Series of experiments are

conducted to determine catalytic convert performance parameters; LOT, OSC, conversion

efficiencies, effect of Lambda value on conversion efficiency.

6. Methodology of Research, Results / Comparisons:

6.1 Methodology of research:

To achieve above stated objectives ceramic monoliths with active surface were coated with

the catalyst Cobalt oxide and Manganese oxide prepared by the co-precipitation method. Cobalt

oxide and manganese oxide with total loading of 16.8 % wt. was chosen based on study, at higher

loading excessive oxide forms cluster on the catalyst surface which reduces the porosity of

structure. Ratio of Cobalt oxide to Manganese oxide catalyst loading was fixed based on 5:1 ratio

of Pt: Rh (oxidation catalyst: reduction catalyst) which is found to be the best in the exhaust

catalytic converter. Converter coated with PGM catalyst (commercially available) was prepared

for base line data (reference) and to assess the effect of Ce and Pt doping on catalyst performance,

converters coated with catalyst having proportion of Co:Mn:Ce = 5:1:1 (molar ratio), Co:Mn = 5:1

doped with Pt. 0.12 % wt. Pt.(0.168 g/monolith) and Co:Mn:Ce = 5:1:1 doped with Pt. 0.12 % wt.

Pt. (0.168 g/monolith) were also prepared.

A four-stroke petrol engine equipped with transition metal oxide catalytic convertor was

tested for different catalyst converter performance parameters under different engine operating

conditions, including catalyst efficiency, LOT, effect of A: F ratio and OSC. Five gas analyzers

were used to get exhaust gas emission like CO, HC, and NOx. To change the A:F ratio in order to

determine the effect of A:F ratio on converter performance, a programmable Engine Control Unit

(ECU) was attached along with OEM (ECU). Engine scanner was used for data acquisition.

Lambda sensors were attached at the inlet and outlet of the catalytic convertor to find Oxygen

Storage Capacity (OSC).

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6.2 Experimentation and results:

Experimentation work was done in two parts. In first part catalyst preparation, its

characterization and converter fabrication work were done. Catalytic converter engine test setup

was prepared and catalytic converter emission tests were carried out in second part. These

subsequent sections present the details of materials, methods, testing, engine test setup and results

of experimental study.

6.2.1 Catalyst preparation:

Material: Cobalt nitrate hexahydrate Co(NO3)2 ·6H2O, Manganese nitrate Mn(NO3)2, Cerium

nitrate hexahydrate Ce(NO3)3 ·6H2O and Platinum nitrate Pt(NO3)2 were used as catalyst materials

(precursors). In addition, Na2O3 (99.5% purity) was used as a suitable solvent in other to prepare

our solution.

Catalysts preparation method: Catalysts were prepared by co-precipitation method as shown in

Figure 1. 32.01 g of Cobalt nitrate Co(NO3)2.6H2O and 2.35 ml of Manganese nitrate Mn(NO3)2

were first dissolved separately in 50 ml and 20 ml of distilled water respectively and then aqueous

solutions were mixed. One molar (1M) Na2CO3 solution was added drop-wise to the precursor

solution under vigorous stirring until pH 10 was reached. The precipitate was allowed to age at

room temperature for 2 hr. The obtained precipitate was filtered and washed with distilled water

several times until a pH of 7 was reached in order to remove the sodium salts. The precipitate was

then dried at 110°C overnight in hot air oven and crushed to a fine powder. Fine powder was

calcined in muffle furnace at 400°C (ramp = 10°C/min) under air atmosphere for 5 h. The flow

diagram and pictorial view of catalyst preparation method are reported in figures 1 and 2

respectively.

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Fig. 1 Flow diagram of catalyst preparation method

Fig. 2 Pictorial view of catalyst preparation method

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Monolith material and configuration: Monolith substrate of Cordierite (2MgO.2Al2O3.5SiO2)

were used for experimentation work which have high mechanical stability and low thermal

expansion coefficient. From the available shapes, round shape monolith was chosen because it

provides radial temperature gradient along the minor axis, less deformation, uniform holding

pressure and higher durability. Substrate volume 1.558 L (97.98% of engine suction capacity)

having 150 mm length, 115 mm diameter was chosen from commercially available substrate

dimensions, considering engine suction capacity and lower substrate diameter and higher length

to supports lower LOT. Monolith of 600 CPI (cells per square inch) cell density were taken for

work as shown in figure 3.

Fig. 3 Ceramic monolith substrate

Coating technique: Smooth aqueous slurry of catalyst was made. The slurry was maintained at3.5-4 pH with the help of the nitric acid. Monoliths were dipped into the slurry and immersed for1 min. Excess slurry was eliminated by vacuum. Coated samples were dried at 120°C for 30 minand weighted to estimate the weight gain. Coating procedure was repeated to obtain the desiredamount of coating. Monoliths were then calcined at 450°C for 2 h. figure 4 shows coated anduncoated ceramic monoliths.

Fig. 4 Ceramic monolith coated with Co:Mn (5:1) and uncoated ceramic monolith

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Mat material: Coated ceramic monolith was wrapped in Intumescent mats which provides

mechanical support to the substrate to keep it in place during operation. It also acts as a thermal

insulator between the substrate and the outer shell and as a seal to prevent exhaust gas flowing

around the substrate. Mat consists of vermiculite, high temperature aluminosilicate fibers and

organic binders. Mat expands at high temperatures, thus compensating for the thermal expansion

of the shell and providing adequate holding force under all operating conditions. Tongue and

groove layout as shown in figure 5 was used in present work and length (A) of the support mat

was calculated using the equation:

A = (Mat thickness + Substrate diameter) ⋅π

Fig. 5 Intumescent mat of Tongue and groove layout

Casing: Cylindrical shell was selected as it depends on monolith shape and cylindrical canning

has uniform pressure distribution. Diffuser cone angle has significant effect on the flow

distribution which eventually effect conversion efficiency. In present case cone angle of 30° was

taken as it is conventionally accepted. Material of casing was ferrite stainless steel 409 which has

low thermal expansion coefficient and excellent creep resistance which is required to maintain the

holding force provided by the mat. Drawing of casing and finished components of casing are as

shown in figures 6 and 7 respectively.

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Fig. 6 Casing drawing

Fig. 7 Casing components

Canning method: Clamshell type canning method was used as it is popular from a tooling cost

and productivity standpoint. The stuffing cone was used to get a smooth compression of the mat

and to reduce high peak pressures during insertion, due to visco-elastic behaviour of the support

mat. Figure. 8 shows canned monolith/catalytic converter. Complete process is summarised in

pictorial form in figure. 9

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Fig. 8 Monolith, coated monolith and catalytic converter

Fig. 9 Pictorial view of converter preparation process

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6.2.2 Engine test setup:

The measurements of engine-catalyst system behavior, including LOT, OSC, overall

conversion efficiencies, effect of A:F ratio, engine speed and ignition angle on conversion

efficiencies were performed on an engine-catalyst setup. Schematic and actual engine catalyst test

setup are shown in figure. 10 and 11 respectively.

Engine: 1.6 L, 4- cylinder inline petrol engine with 4-valves per cylinder and multi point fuel

injection system was used for the experiments. Engine specifications are listed below. Engine was

attached with OEM and programmed ECU. The engine throttle was controlled manually to set

engine speed at desired value.

Engine Specifications:

Engine type: Inline

Cylinders: 4

Displacement Volume: 1590 cm3

Bore: 75 mm

Stroke: 90 mm

Compression ratio: 9:01

Power: 67 kW @ 6000 RPM

Torque: 132 Nm @ 3000 RPM

Fuel supply System: Multipoint Injection

Fuel: Gasoline

Valve configuration: SOHC

Fig. 10 Schematic of Engine catalyst test setup

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Fig. 11 Engine catalyst test setup

Engine control: The engine is essentially controlled by an Maruti Original Equipment

Manufacturer (OEM) engine control unit (ECU). The ECU modulates the A:F ratio around

stoichiometric based on the feedback from an upstream heated exhaust gas oxygen (HEGO)

sensor. The exhaust composition varies with A:F ratio. In order to vary A:F ratio under steady

state operation, a programmable ECU was attached with existing system for the fuel injection.

ECU was got prepared from Race Dynamics Company, Bangalore especially for these

experimentation purpose. Figure 12 shows both OEM and programmable ECU. Controls of the

ECU and its connection with OEM was as shown in diagram.

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Fig. 12 Engine control

Instruments: During the experimentation, multiple instruments were used in measuring exhaust

species concentrations. The concentration of exhaust species HC, CO, NOx was measured by a gas

analyzer (i3sys Model EPM-1601). Lambda sensor Maruti OEM was used to measure A: F. K type

thermocouples were used to measure temperature of catalytic converter, engine exhaust

temperature before and after converter. Engine data was acquired through connecting Launch

engine scanner (X-431 PRO), a wireless OBD reader. The scanner provided following engine

parameters:

• MAP (bar) • A:F ratio (lambda value)

• Intake air temperature (°C) • Throttle position (%)

• Engine coolant temperature (°C) • Spark Ignition advance (°)

• Engine speed (rpm) • Misfiring monitoring

Test conditions of the engine was fixed as per the catalyst test guidelines:

(1) LOT of converter: Tests were carried out with engine running at 2500 rpm from cold start

engine with normal lambda modulation.

(2) A:F ratio and conversion efficiency: Tests were carried out with engine running at 2000 rpm,

0.5 bar MAP after steady state condition.

(3) Effect of ignition angle: Test were carried out at different ignition angle from 20° BTDC to

10° ATDC with 10° interval with normal lambda modulation.

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(4) OSC of converter: Test were carried out at fully warmed up engine with at engine speed 2000

rpm for 2 minutes by monitoring lambda waveform of upstream and downstream lambda sensors.

(5) Engine speed and conversion efficiency: Test were carried out at different engine speed from

1000 rpm to 3500 rpm at interval of 500 rpm.

6.3 Results/Comparison:

6.3.1 LOT of converter: Tests were carried out with engine running at 2500 rpm from cold start

engine with normal lambda modulation. Temperature of engine exhaust and catalytic converter

were monitored with respect to time to get the cold start timing. Simultaneously HC, CO and NOx

emissions before and after catalytic converter were also noted with the help of gas analyzer. To

get baseline data, tests were also performed with PGM catalytic converter.

The experimental results were analyzed and the data are summarized in graphical form.

From the experimental data the effect of catalyst temperature on catalyst efficiency of HC, CO and

NOx respectively was determined and is plotted in figures 13, 14 and 15. Figures 16 and 17 show

comparative results of LOT and time for different converters.

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Fig. 13 HC Conversion efficiency Vs. Time (s) Fig. 14 CO Conversion efficiency Vs. Time (s)

Fig. 15 NOx Conversion efficiency Vs. Time (s)

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Fig. 16 Comparative results of Effect of LOT on Conversion efficiencies for different converters

Fig. 17 Comparative results of effect of time on Conversion efficiencies for different converters

PGM Co:Mn Co:Mn: Ce Co:MnPGM

Co:Mn:Ce:PGM

CO LOT TIME 160 92 92 92 85HC LOT TIME 179 120 120 108 106NOx LOT TIME 127 97 95 120 100

0

20

40

60

80

100

120

140

160

180

200L

ight

off

Tim

e (s

)

Catalyst

Catalyst Light off time

CO LOT TIME HC LOT TIME NOx LOT TIME

PGM Co:Mn Co:Mn: Ce Co:MnPGM

Co:Mn:Ce:PGM

CO LOT 235 163 164 155 160HC LOT 273 195 195 190 189NOx LOT 216 178 167 195 172

0

50

100

150

200

250

300

Cat

alys

t Tem

p (°

C)

Catalyst

Light off Temperature

CO LOT HC LOT NOx LOT

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From the engine test results it was found that with Co:Mn catalyst, 50% HC conversion was

achieved at 195°C (LOT) in 120 s, whereas PGM coated converter gives 50% HC conversion

efficiency at 273°C (LOT) in 179 s. With Co:Mn:Ce coated catalytic converter, 50% HC

conversion was achieved at 195°C (LOT) in 120 s. With Co:Mn:PGM coated catalytic converter

50% HC conversion was at 190°C (LOT) in 108 s. With Co:Mn:Ce:PGM coated catalytic

converter, 50% HC reduction efficiency was at 189°C (LOT) in 106 s.

6.3.2 A:F ratio and conversion efficiency: To determine the effect of A:F ratio on conversion

efficiencies, after preconditions checkup, tests were carried out with engine running at 2000 rpm,

0.5 bar MAP. Test were carried out at seven different lambda values (lambda 1, three values for

rich mixture and three values for lean) i.e. 0.98, 0.99, 0.995, 1, 1.005, 1.01, 1.02. Temperature of

engine exhaust and catalytic converter were monitored with respect to time to get cold start timing.

Simultaneously HC, CO and NOx emissions before and after catalytic converter were also noted

with the help of gas analyzer. To get baseline data, tests were also performed with PGM catalytic

converter. The experimental results were analyzed and the data are summarized in graphical form.

From the experimental data the catalyst efficiency is determined and plotted versus lambda value

as shown in figures 18 and 19. Results are also summarized for all five catalysts for their lambda

window as shown in figure 20.

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Fig. 18 Effect of Lambda value on conversion efficiencies

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.98 0.99 0.995 1 1.005 1.01 1.02

Con

v. E

ff. (

%)

Avg. Lambda Value

Effect of Lambda Value on Conv. Eff. (Co: Mn 5:1)HC CO NOx

21

Fig. 19 80% lambda window and conversion efficiencies

Fig. 20 Lambda window for Catalyst

0.98 0.99 0.995 1 1.005 1.01 1.02HC 0.8 0.9 0.95 0.95 0.95 0.95 0.95CO 0.59 0.83 0.96 0.97 0.98 0.98 0.98NOx 0.97 0.97 0.97 0.95 0.93 0.8 0.4EFF 0.8 0.8 0.8 0.8 0.8 0.8 0.8

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Con

v. E

ff. (

%)

Avg. Lambda Value

Effect of Lambda Value on Conv. Eff. (Co:Mn 5:1)HC CO NOx EFF

PGM Co:Mn Co:Mn:Ce Co:Mn PGMCo:Mn:Ce

PGMSeries1 0.147 0.294 0.277 0.294 0.279

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Lam

bda

win

dow

vla

ue

Catalyst

Lambda window for catalyst

22

From the engine test results it was found that with Co:Mn catalyst 80% conversion efficiency -

lambda window is 0.294 whereas PGM coated converter gives 80% conversion efficiency -lambda

window is 0.147. With Co:Mn:Ce coated catalytic converter, lambda window is 0.277. With

Co:Mn:PGM coated catalytic converter 80% conversion efficiency -lambda window is 0.294. With

Co:Mn:Ce:PGM coated catalytic converter, 80% conversion efficiency- lambda window is 0.279.

6.3.3 OSC of converter: Higher lambda window of the catalytic converter confirms that the

converter has good OSC however OSC was confirmed by upstream and downstream lambda wave

form (O2S B1S1 and O2S B1S2) Test were carried out at fully warmed up engine with at engine

speed 2000 rpm for 2 minutes by monitoring lambda waveform of upstream and downstream

lambda sensors.

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Fig. 21 Upstream and downstream lambda wave form (O2S B1S1 and O2S B1S2)

24

Test were carried out to determine the effect of engine speed and ignition angle on conversion efficiencies,

under normal running condition converter is fully warmed up and not affect the converter conversion

efficiency

7. Achievements with respect to objectives:

Developed catalytic converter made from cobalt oxide and manganese oxide as catalyst and

investigated HC, CO and NOx conversion efficiencies

Determined effect of different A:F ratio on catalytic conversion efficiency and also inferred the

working lambda window of the metal oxide catalyst (80% of conversion efficiencies CO, HC and

NOx)

Determined LOT temperature of catalytic convert

Oxygen storage capacity was confirmed by upstream and downstream lambda wave forms (O2S B1S1

and O2S B1S2)

8. Conclusions:

Cobalt oxide and manganese oxide as catalysts for the three-way catalytic converter were assessed

for redox reactions of CO, HC and NOx and following conclusions are drawn.

Intrinsic activity of the cobalt oxide is very closed to PGMs catalyst, Rh based and Mn based oxides

for NOx reduction for different support and under different reaction condition are compared.

Cobalt oxide as oxidizing catalyst and Manganese oxide as reducing catalyst were selected as catalyst

for three-way catalytic converter.

For catalyst preparation cobalt oxide and manganese oxide in the ratio of 5:1 were taken based on

Pt:Rh ratio of 5:1 in PGM based catalyst.

Among the three methods of Catalyst preparation i.e. Sol gel, Wet impignation and Co-precipitation,

Co-precipitation method of catalyst preparation was used as final product shows characteristics such

as homogeneous distribution, good dispersion of components and high surface.

The catalysts were characterized by various characterization techniques to get confirm that the catalyst

prepared and final coated ceramic monolith are as per design.

• X-ray diffraction (XRD) was use for confirmation of phase analysis and to decide calcination

temperature for phase stability.

• Scanning electron microscopy (SEM) was used to check dispersion of the catalyst on the wash

coating and monolith surface.

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• Energy Dispersive X-ray Analysis (EDAX) was used to investigate the elemental composition of

catalyst on coated ceramic monolith.

With OEM ECU, it was not possible to test catalytic converter under different lambda value and

control parameters. Hence Programmable ECU was developed for the work

Result of Catalytic Converter Engine Test

• From the engine test results it was found that with Co:Mn catalyst, 50% HC conversion was

achieved at 195°C (LOT) in 120 s and 80% conversion efficiency - lambda window is 0.294

whereas PGM coated converter gives 50% HC conversion efficiency at 273°C (LOT) in 179

s and 80% conversion efficiency Lambda window is 0.147. With Co:Mn:Ce coated catalytic

converter, 50% HC conversion was achieved at 195°C (LOT) in 120 s and 80% conversion

efficiency - lambda window is 0.277. With Co:Mn:PGM coated catalytic converter 50% HC

conversion was at 190°C (LOT) in 108 s and 80% conversion efficiency -lambda window is

0.294. With Co:Mn:Ce:PGM coated catalytic converter, 50% HC reduction efficiency was at

189°C (LOT) in 106 s and 80% conversion efficiency- lambda window is 0.279.

• Engie speed and ignition angle effects the engine emission, however under normal running

condition converter is fully warmed up and not affect the converter conversion efficiency

• Oxygen storage capacity was confirmed by upstream and downstream lambda wave form

(O2S B1S1 and O2S B1S2)

9. papers published:

Charula Patel, N M Bhatt, Srinivas Palanki,, Assessment Study of Cobalt Oxide and Manganese Oxide

Catalyst for Three Way Catalytic Converter, Catalysis and Reaction Engineering Division 2015 : Core

Programming Area at the 2015 AIChE Annual Meeting : Salt Lake City, Utah, USA, 8-13 November 2015

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