Technical Field
The present invention relates to a catalyst system for for treatment of exhaust gas
of an automobile. Specifically, the present invention relates to the catalyst system used
to abatement of hydrocarbons, carbon monoxide and nitrogen oxides in the motorcycle
exhaust gas. Further, the present invention relates to a process for preparing the catalyst.
10 The exhaust gas needs to meet various norms, before letting out into the atmosphere.
The present invention also relates to an exhaust gas treatment system incorporating the
catalyst unit. The present invention also relates to an exhaust gas treatment process for
treating the exhaust gas of the motorcycle.
15 Background
Automobiles, which incorporates internal combustion engines, are widely used
throughout the world, for transportation. The product or exhaust gas from an internal
combustion engine has a number of different components. The product may contain
partially converted feed (hydrocarbons), carbon di oxide, carbon monoxide, nitrogen
20 oxides etc. The wider usage of the automobiles leads to wider product of these products.
Exhaust gas from an automobile engine often contains emissions such as
hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). Such emissions
are relatively harmful and need to be pretreated before letting out to the atmosphere.
25 Furthermore, the emission treatment norms are becoming stricter year on year. Recently,
stricter emission criteria are already required or will be required in many countries to
improve the environmental conditions by further limiting emissions such HC, CO, NOx.
A vehicle such as a motorcycle or scooter is generally provided with an exhaust
30 emission gas purifying device such as a catalyst which purifies exhaust gas discharged
3
from an engine. The purified exhaust gas from the exhaust gas purifying device is then
discharged into the atmosphere in a harmless state. In an example, a catalyst unit is used
as the exhaust gas purifying device. The catalyst unit is disposed either inside the
muffler or in the middle of an exhaust pipe having one end thereof connected to an
5 engine and having the other end thereof connected to a muffler. The catalyst unit is used
to reduce tailpipe emission levels. Generally, the catalyst unit is built in a honeycomb
or pellet geometry to expose the exhaust gases to a large surface made of one or more
noble metals such as platinum group metals including platinum, palladium rhodium.
The catalyst unit is composed of mainly a substrate, a wash coat and one or more layers
10 of noble metals such as platinum, palladium and rhodium.
It is well known in the art that various catalysts and exhaust gas purification
systems have been developed and used in the automobile, to resolve the challenging
emission control problems. However, there is always a room for improvement and
15 advancement of the catalyst system.
Reference is made to the CN patent application CN105664939A, which discloses
a catalytic converter for treating motorcycle exhaust gas composed of a carrier and a
washcoat layer. The said washcoat layer is composed of alumina or an oxygen storage
20 material and precious metals comprising platinum, palladium and rhodium. First of all,
as precious metals are extremely expensive, the high cost of such catalysts is still a
critical factor for application of such catalysts. Further, it is essential for the catalyst to
treat the exhaust gas in a maximum possible way, for example, a three-way conversion
(TWC) catalyst. Hence, it is desired to develop a catalyst system with limited precious
25 metals used, while could meet the increasingly stringent regulations simultaneously.
Further reference is made to US patent application US20120128558 A1, which
discloses a TWC catalyst of at least two front layers and two rear layers in conjunction
with a substrate. This document discloses that all layers comprise a platinum group
30 metal component, and the rear bottom layer is substantially free of a ceria-containing
4
oxygen storage component. Even though this catalyst system could meet the emission
norms there is still a need to reduce the hydrocarbons from the exhaust gas. Furthermore,
there is a requirement to develop a catalyst having improved conversion of the reactant
exhaust gas.
5
Although the prior arts disclose various catalyst system to treat the exhaust gas stream,
the systems know are either not satisfactory or very costly. Thus, there is still a need for
cost effective, well designed catalyst system for aftertreatment of motorcycles exhaust
gas.
10
In view of this, the inventors of the present disclosure felt a need to develop a catalyst
system which overcomes all the problems of the prior arts and is cost effective.
Particularly there is a need to improve the efficiency of the catalyst i.e. the conversion
of the hydrocarbons. The present invention provides a improves catalyst system and
15 exhaust treatment process for converting the harmful components of the exhaust gas to
less harm full components that can be let out in the atmosphere. This improved catalyst
effectively reduces emission, specifically the hydrocarbons present in the exhaust gas.
The catalyst system not only gives economic benefit but also addresses the
environmental aspect and meeting the emission norms.
20
An object of the present invention is to provide a catalyst effective to catalyze the
abatement of HC, CO and NOx from motorcycles exhaust gas.
Another object of the present invention is to effectively reduce the emission in the
25 exhaust gas from motorcycles.
Yet another object of the present invention is to involve a catalyst system which is cost
effective.
30 Yet another object of the present invention is to provide an exhaust gas treatment system
5
for effectively treating the automobile exhaust.
Summary of the Invention
The present invention relates to a catalyst system for aftertreatment of automobile
5 exhaust gas. Specifically, the present invention relates to the catalyst system used to
abatement of hydrocarbons, carbon monoxide and nitrogen oxides in the motorcycle
exhaust gas. The exhaust gas needs to meet various norms, before letting out into the
atmosphere. The present invention also relates to an exhaust gas treatment system
incorporating the catalyst unit. The present invention also relates to an exhaust gas
10 treatment process for treating the exhaust gas of the motorcycle.
In one aspect of the disclosure, the present invention relates to a catalyst system which
effectively catalyze the abatement of HC, CO and NOx from motorcycles exhaust gas.
The catalyst system for aftertreatment of motorcycle exhaust gas comprising two bricks
15 1 and 2 in sequence. The brick-1 is located upstream comprising washcoat-1 and
washcoat-2 coated on substrate-1. The brick-2 located downstream comprising of
washcoat-3 coated on substrate-2. All wash coats 1, 2 and 3 comprising noble metal Pt,
Pd and Rh. The substrate-1 and/or substrate-2 having metal substrate (including
longitudinal structure) comprising oxygen storage component and refractory metal
20 oxide. The thickness ratio for wash coat of brick-1 and brick-2 is from 1.25 to 1.35. The
total average noble metal of the catalyst system is from 35 to 40 g/ft3
. The PGM loading
in brick-1 is 45 to 50 g/ft3
, and in brick-2 is 25 to 30 g/ft3
.
The inventors of the present invention have surprisingly found that by providing the
25 catalyst including various features along with the thickness ratio for wash coat of brick1 and brick-2, a cost effective catalyst system which effectively reduces the emission
in the exhaust gas can be obtained.
In another aspect of the disclosure, the present invention relates to an exhaust gas
30 treatment system involving the catalyst system or unit of the invention. The exhaust gas
6
treatment system may have the catalyst unit along with other units for effective
treatment.
In another aspect of the disclosure, the present invention relates to a process for treating
5 the exhaust gas with a catalyst system.
Brief Description of the Drawings:
The invention itself, together with further features and attended advantages, will
10 become apparent from consideration of the following detailed description, taken in
conjunction with the accompanying drawings. One or more embodiments of the present
invention are now described, by way of example only wherein like reference numerals
represent like elements and in which:
Figure 1 illustrates a schematic representation of catalyst, according to an embodiment
15 of the present invention;
Figure 2 illustrates a schematic representation of catalyst, according to an embodiment
of the present invention;
Figure 3 illustrates a schematic representation of catalyst, according to an embodiment
of the present invention;
20 Figure 4 illustrates a schematic representation of catalyst, according to an embodiment
of the present invention;
Figure 5 shows the total HC (THC) emissions on GVS of Example 1-4;
Figure 6 shows the accumulated THC emission of Example 2 and 3;
Figure 7 shows the accumulated NOx emission of Example 2 and 3;
25 Figure 8 shows the accumulated THC emission of Example 5 and 6;
Figure 9 shows the cumulative hydrocarbon emission of Example 7 and 8;
The drawings referred to in this description are not to be understood as being drawn to
scale except if specifically noted, and such drawings are only exemplary in nature.
30
7
Detailed Description of the Invention
While the invention is susceptible to various modifications and alternative forms,
an embodiment thereof has been shown by way of example in the drawings and will be
described here below. It should be understood, however that it is not intended to limit
5 the invention to the particular forms disclosed, but on the contrary, the invention is to
cover all modifications, equivalents, and alternative falling within the spirit and the
scope of the invention.
The terms “comprises”, “comprising”, or any other variations thereof, are intended
to cover a non-exclusive inclusion, such that a setup, structure or method that comprises
10 a list of components or steps does not include only those components or steps but may
include other components or steps not expressly listed or inherent to such setup or
structure or method. In other words, one or more elements in a system or apparatus
proceeded by “comprises… a” does not, without more constraints, preclude the
existence of other elements or additional elements in the system or apparatus.
15 For the better understanding of this invention, reference would now be made to the
embodiment illustrated in the accompanying Figures and description here below, further,
in the following Figures, the same reference numerals are used to identify the same
components in various views.
While the present invention is illustrated in the context of a vehicle, however,
20 exhaust system and aspects and features thereof can be used with other type of vehicles
as well. The terms “vehicle”, “two wheeled vehicle” and “motorcycle” have been
interchangeably used throughout the description. The term “vehicle” comprises
vehicles such as motorcycles, scooters, bicycles, mopeds, scooter type vehicle, allterrain vehicles (ATV) and the like.
25
Furthermore, it is to be understood that the invention is not limited to the details of
construction or process steps set forth in the following description. The invention is
capable of other embodiments and of being practiced or being carried out in various
ways.
8
The following terms, used in the present description and the appended claims, have the
following definitions:
Expressions “a”, “an”, “the”, when used to define a term, include both the plural and
singular forms of the term.
5 All percentages and ratios are mentioned by weight unless otherwise indicated.
In one aspect of the invention, provides a catalyst system for treatment exhaust gas of
an automobile comprising, one or more substrate and two or more wash coat layers on
the substrate forming one or more bricks, wherein
10 the first brick located in the upstream, comprises first wash coat layer and second
wash coat layer, coated on the first substrate,
the second brick located in the downstream comprising of third wash coat layer,
coated on second substrate,
wherein the wash coat layers comprising noble metal selected from Pt, Pd and Rh,
15 the first substrate and/or the second substrate having a metal substrate comprising
oxygen storage component and refractory metal oxide,
characterized in that the thickness ratio of first brick and second brick is from 1.25
to 1.35.
20 In an embodiment of the invention a catalyst system is disclosed, wherein noble metal
has a total average loading of the from 35 to 40 g/ft3
in the catalyst system.
In another embodiment of the invention a catalyst system is disclosed, wherein the
noble metal loading in first brick is 45 to 50 g/ft3
, and in second brick is 25 to 30 g/ft3
.
25
Yet another embodiment of the invention involves the catalyst system, wherein Pd/Rh
weight ratio in the first brick is from 2.5 to 2.8; and Pd/Rh weight ratio in the second
brick is from 1/5 to 1/3.
9
Yet another embodiment of the invention involves a catalyst system, wherein the two
bricks system are together with 50 mm away from the engine pipe in motorcycle BSVI applications.
5 Yet another embodiment of the invention involves a catalyst system, wherein the metal
substrate is a longitudinal structure of monoliths.
Yet another embodiment of the invention involves a catalyst system, wherein the wash
coat layers are applied on a single substrate.
10
Yet another embodiment of the invention involves a catalyst system, wherein the
substrate having the oxygen storage component of Ceria and refractory metal oxide
components is one or more of Niobium, Molybdenum, Tantalum, Tungsten and
Rhenium.
15
In an embodiment of the invention a process for preparing the catalyst system for
aftertreatment of automobile exhaust gas comprising steps of
preparing and coating of one or more wash coat layers on one or more substrate
forming two or more bricks, comprising
20 a. diluting the soluble noble metal solution with water to reach incipient
wetness.
b. Impregnating the alumina, cerium and zirconium oxide particles on the
Noble metal solution.
c. Addition of the water and another soluble noble metal solution to form
25 a slurry.
d. The slurry is applied on a metal substrate.
e. Drying and calcination at a temperature of 500oC -600°C for at least 2
hours.
wherein the slurry for the first and second wash coat region has at least 40 % solid
30 content, the slurry for the third wash coat region has at least 30 % solid content,
10
the first brick located in the upstream, comprises first wash coat layer and second
wash coat layer,
the second brick located in the downstream comprises the third wash coat layer,
characterized in that the thickness ratio of first brick and second brick is from 1.25
5 to 1.35.
In another embodiment of the invention a process for preparing the catalyst system,
wherein the noble metal loading in first brick is 45 to 50 g/ft3
, and in second brick
is 25 to 30 g/ft3
.
10 Yet another embodiment of the invention a process for preparing the catalyst system,
wherein Pd/Rh weight ratio in the first brick is from 2.5 to 2.8; and Pd/Rh weight ratio
in the second brick is from 1/5 to 1/3.
Yet another embodiment of the invention a process for preparing the catalyst system,
15 wherein the two bricks system are together with 50 mm away from the engine pipe in
motorcycle BS-VI applications.
Yet another embodiment of the invention a process for preparing the catalyst system,
wherein the metal substrate is a longitudinal structure of monoliths.
20 In an embodiment of the invention an exhaust gas treatment system for treating the
exhaust gas of an automobile comprising one or more catalyst system
the catalyst system comprising one or more substrate and one or more wash coat layers
on the substrate forming two or more bricks, wherein
the first brick located in the upstream, comprises first wash coat layer and second wash
25 coat layer, coated on the first substrate,
the second brick located in the downstream comprising of third wash coat layer, coated
on second substrate,
wherein the wash coat layers comprising noble metal selected from Pt, Pd and Rh,
the first substrate and/or the second substrate having a metal substrate comprising
30 oxygen storage component and refractory metal oxide,
11
characterized in that the thickness ratio of first brick and second brick is from 1.25 to
1.35.
In an embodiment of the invention an exhaust gas treatment process for treating the
5 exhaust gas of an automobile comprising steps of
sending the exhaust gas from the automobile engine to an exhaust gas treatment system
to convert the harmful hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides
(NOx) into less harmful components to meet the emission norms,
wherein the exhaust gas treatment system is the system as claimed in claims 14.
10
In an embodiment of the invention use of the catalyst system as claimed in claim 1 for
aftertreatment of automobile exhaust gas.
In an embodiment of the invention use of the catalyst system as claimed in claim 16
15 having reduced back pressure and optimum usage of the noble metals.
The catalyst system for purifying an exhaust gas of an internal combustion engine,
comprises at least one substrate; a first washcoat region disposed on upstream side of
20 the at least one substrate, wherein the first washcoat region comprises a first platinum
group metal (PGM); a second washcoat region disposed on the substrate adjacent/in
sequence to the first washcoat region, wherein the second washcoat region comprises a
second platinum group metal (PGM); a third washcoat region disposed over the first
washcoat region in the upstream side of the substrate, wherein the third washcoat region
25 comprises a third platinum group metal (PGM); wherein the first PGM, the second
PGM and third PGM is selected from the group consisting of platinum, palladium and
rhodium. The total loading/density of the second PGM is greater than the total
loading/density of the first PGM, and the total loading/density of the first and third
PGM together is greater than the total loading/density of the second PGM. Furthermore,
12
the ratio of the thickness first wash coat layer to the second wash coat layer is from 1.25
to 1.35.
The terms “rear / rearward / back / backward”, “up / upper / top”, “down / lower / lower
ward / downward, bottom”, “left / leftward”, “right / rightward” used therein represents
5 the directions as seen from a vehicle driver sitting astride and these directions are
referred by arrows Fr, Rr, U, Lr, L, R in the drawing Figures.
Figure 1 illustrates a schematic representation of catalyst, according to an embodiment
of the present invention.
The catalyst (100) of the invention comprises a first substrate (101), a second substrate
10 (102), a first washcoat region (201), a second washcoat region (202), a third washcoat
region (203). The second substrate (102) is disposed on adjacent to the first substrate
(101) along the downstream of the first substrate (101).
In another embodiment, as shown in figure 4, the second substrate (102) is disposed
adjacent to the first substrate (101) along the downstream of the first substrate (101)
15 with a predetermined space gap ‘x’ therebetween. The first washcoat region (201) is
disposed on the first substrate (101). The second washcoat region (202). The first
washcoat region (201) is disposed on the first substrate (101). The first washcoat region
(201) comprises a first platinum group of metals (PGM) selected from the group
consisting of platinum, palladium and rhodium. In an embodiment, the
20 Palladium/Rhodium weight ratio in the first substrate is from 2.5 to 2.8. Further, the
second washcoat region (202) is disposed on the second substrate (102) adjacent to the
first substrate (101) and along a direction downstream of the first substrate (101).
In an embodiment of the invention, the Palladium/Rhodium weight ratio in the second
substrate is from 1/5 to 1/3. The second washcoat region (202) comprises a second
25 platinum group of metals selected from the group consisting of platinum, palladium and
rhodium. Furthermore, the third washcoat region (203) is disposed on the first washcoat
region (201) on the first substrate (101). The third washcoat region (203) comprises a
first platinum group of metals selected from the group consisting of platinum, palladium
13
and rhodium. In an embodiment, the thickness ratio of first and third washcoat region
together in the first substrate and of the second washcoat region in the second substrate
is from 1.25 to 1.35. In an embodiment, the total loading of first and the third PGM is
45 to 50 g/ft3. In an embodiment, the loading of the third PGM is 25 to 30 g/ft3. In an
5 embodiment, the length of the first substrate (101) and the second substrate (102) are
equal.
In another embodiment, as shown in figure 3, the first substrate (101) and the second
substrate (102) is an integral substrate (103). In an embodiment, as shown in figure 04,
there is a space gap of ‘x’ provided between the first substrate (101) and (102). This
10 space gap ‘x’ between the first substrate (101) and second substrate (102) is provided
to improve uniformity index of flow and maintain turbulent flow in second substrate
(102) leading to better purification efficiency of the catalyst system (100). In an
embodiment, the space gap is in the range of 10 mm to 20mm.
In another aspect of the invention, the substrate is a metal substrate (including
15 longitudinal structure) comprising oxygen storage component and refractory metal
oxide. The commonly used oxygen storage component is cerium oxide or a mixed oxide
containing cerium, e.g. ceria-zirconia mixed oxide. The refractory metal oxide is
selected from alumina, silica, zirconia, titania, ceria and mixtures thereof.
In preferable embodiments, the catalyst system comprising different Pd/Rh ratio in
20 different bricks of the catalyst. Preferably, the Pd/Rh weight ratio in brick-1 is from 2.5
to 2.8; and Pd/Rh weight ratio in brick-2 is from 1/5 to 1/3.
Another aspect of the invention provides a catalyst system applied on a two bricks
system together with 50 mm away from the engine pipe in motorcycle BS-VI
25 applications.
The invention itself, together with further features and attended advantages, will
become apparent from consideration of the following detailed description, taken in
conjunction with the accompanying drawings. One or more embodiments of the present
14
invention are now described, by way of example only wherein like reference numerals
represent like elements and in which:
EXAMPLES
5 There are many variations and combinations that can be made based on this disclosure
to make catalyst systems for aftertreatment of motorcycle exhaust gas without departure
from the spirit of this disclosure. The following examples and embodiments are given
as illustration purposes only that should not be used as limit to the invention.
10 The coating of noble metals on the substrate and the arrangement on the substrate plays
an important part in the overall performance of the engine. If the coating of noble metal
on the substrate is very thick then it may increase the back pressure in the exhaust
system affecting performance of the engine. Further, the coating of noble metal
increases the cost. Therefore, the coatings of noble metal on the substrate has to be done
15 in optimize way such as it does not affect the engine performance and also meets the
emission norms for the vehicle. At the same time, the coating of noble metal should be
cost effective for the catalyst.
The preparation method as described below, are used to prepare the catalyst system of
the invention in example 1 to 8:
20 Step 1: preparation and coating of wash coat 1:
Soluble rhodium solution was diluted with water to reach incipient wetness for the
impregnation of alumina, cerium and zirconium oxide particles. The impregnated
sample was then mixed with water, soluble platinum solution to form a slurry with ~40
wt % solid content. The above mixture was applied to a metal substrate (40x60 mm
25 DxL, cell density is 200 cpsi), and was dried and calcined at 550°C for 2 hours.
Step 2: preparation and coating of wash coat 2:
Soluble palladium and rhodium solutions were diluted with water to enable
incipient wetness impregnation of alumina and cerium and zirconium oxide. The
15
impregnated sample was then mixed with water to form a slurry with ~30 wt % solid
content. The mixture was applied onto washcoat-1 and was dried and calcined at 550°C
for 2 hours
5 Step 3: preparation and coating of wash coat 3:
Soluble palladium and rhodium solutions were diluted with water to allow
incipient wetness impregnation of alumina and cerium and zirconium oxide particles.
The impregnated sample was then mixed with water and soluble platinum solution to
form a slurry with ~40 wt % solid content. The above mixture was applied to a metal
10 substrate (40x 60 mm DxL, cell density is 200 cpsi), and was dried and calcined at
550°C for 2 hours.
Example 1:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with washcoat loading 1.4 g/in3
in washcoat 1, washcoat loading 1.0 g/in3
15 in
washcoat 2 and washcoat loading 3 g/in3
in washcoat 3. The ratio of the thickness of
the brick 1 to brick 2 is 1.26.
Example 2:
20 Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with washcoat loading 2.0 g/in3
in washcoat 1, washcoat loading 1.0 g/in3
in
washcoat 2 and washcoat loading 3 g/in3
in washcoat 3. The ratio of the thickness of
the brick 1 to brick 2 is from 1.25 to 1.35.
25 Example 3:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with washcoat loading 2.0 g/in3
in washcoat 1, washcoat loading 1.0 g/in3
in
washcoat 2 and washcoat loading 2.4 g/in3
in washcoat 3. The ratio of the thickness of
the brick 1 to brick 2 is from 1.25 to 1.35.
30
16
Example 4:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system, the resulted catalyst with washcoat loading 2.0 g/in3
in washcoat 1, washcoat
loading 1.0 g/in3
in washcoat 2 and washcoat loading 2.0 g/in3
in washcoat 3. The ratio
5 of the thickness of the brick 1 to brick 2 is from 1.25 to 1.35.
Example 5:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with Pd/Rh ratio 2.7 in brick 1, and Pd/Rh ratio 0.4 in brick 2. The ratio of the
10 thickness of the brick 1 to brick 2 is from 1.25 to 1.35.
Example 6:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with Pd/Rh ratio 1.7 in brick 1, and Pd/Rh ratio 0.4 in brick 2. The ratio of the
15 thickness of the brick 1 to brick 2 is from 1.25 to 1.35.
Example 7:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
system with Pd/Rh ratio 2.7 in brick 1, and Pd/Rh ratio 0.25 in brick 2. The ratio of the
20 thickness of the brick 1 to brick 2 is from 1.25 to 1.35.
Example 8:
Above preparation method was used to prepare the catalyst system, the resulted catalyst
25 system with Pd/Rh ratio 2.7 in brick 1, and Pd/Rh ratio 4.0 in brick 2. The ratio of the
thickness of the brick 1 to brick 2 is from 1.25 to 1.35.
Comparative example 1:
30 The catalyst of the comparative example 1 is same as that of the inventive example 1,
17
except that the ratio of thickness in brick 1 to brick 2 is 0.8.
Comparative example 2:
The catalyst of the comparative example 1 is same as that of the inventive example 1,
5 except that the ratio of thickness in brick 1 to brick 2 is 1.
Comparative example 3:
The catalyst of the comparative example 1 is same as that of the inventive example 1,
except that the ratio of thickness in brick 1 to brick 2 is 1.5.
10
Test of THC (Total Hydrocarbon) performance of Example 1 and Comparative
examples 1, 2 and 3:
The catalysts were aged for 24 hours at 550°C in air and were coated on core substrate
(1-inch D * 1-inch L *2). Testing was performed at GVS (gasoline vehicle simulator)
and the space velocity was dynamic which reached to max 85,000 h-1
15 and lambda swing
at 0.80 to 1.20; HC is from 0-20,000 ppm, CO is from 0-35,000 ppm and NOx (NO/NO2)
is from 0-8,000 ppm, H2O = 10%, CO/NOx/O2 varies base on lambda. The amount
THC/CO/NOx are determined by TCD, FID and FTIR infrared spectroscopy. Results
are shown in Figure 5.
20 As show in figure 5, the THC (Total Hydrocarbon) is effectively reduced when the ratio
of the thickness of the brick 1 to brick 2 is between the claimed range (example 1). On
the other hand, if the ratio of the thickness of the brick 1 to brick 2 outside the claimed
range (comparative examples 1 to 3), the desired reduction in the THC is not obtained.
Hence, the rest of example 1 and comparative examples 1 to 3 clearly shows the
25 enhanced performance of the catalyst system of the invention.
Test of THC and NOx performance of Example 2 and 3:
The catalysts of inventive examples 2 and 3, are used for further studies of the NOx
30 performance. The test was carried on an automobile with World Motorcycle Test Cycle
18
(WMTC) cycle. The WMTC cycle is a standard cycle wherein the catalyst is tested by
varying the speed, time. The Catalyst were coated on full size substrate (40 mm D * 60
mm L *2) and assembled on an automobile muffler. The amount THC/CO/NOx are
determined by TCD, FID and FTIR infrared spectroscopy. Results are shown in Figure
5 6 and 7. The gray color denotes the actual speed of the engine. The P8 (yellow color)
denotes the example 3 and P8OH (blue color) denotes the example 2. It can be seen that
the example 3 wash coat loading provides better emission control (THC and NOx
reduction) than the example 2 wash coat loading.
10 Test of THC performance of Example 5 and 6:
The catalysts of inventive examples 5 and 6, are used for further studies of the THC
performance. The test was carried on an automobile with World Motorcycle Test Cycle
(WMTC) cycle. The WMTC cycle is a standard cycle wherein the catalyst is tested by
varying the speed, time
15 The catalysts were aged for 24 hours at 550°C in air and were coated on core substrate
(1-inch D * 1-inch L *2). Testing was performed at GVS (gasoline vehicle simulator),
and the space velocity was dynamic which reached to max 85,000 h-1
and lambda swing
at 0.80 to 1.20; HC is from 0-20,000 ppm, CO is from 0-35,000 ppm and NOx (NO/NO2)
is from 0-8,000 ppm, H2O = 10%, CO/NOx/O2 varies base on lambda. The amount
20 THC/CO/NOx are determined by TCD, FID and FTIR infrared spectroscopy. Results
are shown in figure 8. The 2.7 (red color) denotes the example 5 and 1.7 (blue color)
denotes the example 6. It can be seen that the example 5 wash coat loading provides
better emission control (THC reduction) than the example 6 wash coat loading.
25
Test of THC performance of Example 7 and 8:
The catalysts of inventive examples 7 and 8, are used for further studies of the THC
performance.
The test was carried on motorcycle with WMTC cycle. Catalyst were coated on full
30 size substrate (40 mm D * 90 mm L *2) and assembled on motorcycle muffler. The
19
amount THC/CO/NOx are determined by TCD, FID and FTIR infrared spectroscopy.
Results are shown in figure 9. The gray color denotes the actual speed of the engine.
The 4 (green color) denotes the example 8 and 0.25 (magenta color) denotes the
example 7. It can be seen that the example 7 wash coat loading provides better emission
5 control (Cumulative hydrocarbon) than the example 8 wash coat loading.
Although the invention herein has been described with reference to particular
embodiments, it is to be understood that these embodiments are merely illustrative of
the principles and applications of the present invention. It will be apparent to those
10 skilled in the art that various modifications and variations can be made to the method
and apparatus of the present invention without departing from the spirit and scope of
the invention. Thus, it is intended that the present invention include modifications and
variations that are within the scope of the appended claims and their equivalents.
15 Advantages:
The catalyst unit and the emission treatment system of the invention has the following
advantages:
• Economical and efficient.
• Effective reduction of hydrocarbons (HC), carbon monoxide (CO) and nitrogen
20 oxides (NOx) from the exhaust gas of automobiles.
• Reduced back pressure and at the same time meeting the emission norms.
• Optimal usage of the noble metals in the catalyst resulting in the cost reduction.
25
20
We Claim:
1. A catalyst system for treatment of exhaust gases of an automobile comprising, one
or more substrate and one or more wash coat layers on the substrate forming two or
5 more bricks, wherein
the first brick located in the upstream, comprises first wash coat layer and second
wash coat layer, coated on the first substrate,
the second brick located in the downstream comprising of third wash coat layer,
coated on second substrate,
10 wherein the wash coat layers comprising noble metal selected from Pt, Pd and Rh,
the first substrate and/or the second substrate having a metal substrate comprising
oxygen storage component and refractory metal oxide,
characterized in that, the thickness ratio for wash coat layer of the first brick and
the second brick is from 1.25 to 1.35.
15
2. The catalyst system as claimed in claim 1, wherein noble metal in the catalyst
system has a total average loading in a range of 35 to 40 g/ft3
.
3. The catalyst system as claimed in claims 1 or 2, wherein the noble metal loading in
the first brick is 45 to 50 g/ft3
, and in the second brick is 25 to 30 g/ft3
20 .
4. The catalyst system as claimed in claim 1, wherein Pd/Rh weight ratio in the first
brick is in a range of 2.5 to 2.8; and Pd/Rh weight ratio in the second brick is in a
range of 1/5 to 1/3.
25
5. The catalyst system as claimed in any one of claims 1 to 4, wherein the two bricks
system are together in an exhaust pipe with 50 mm away from an exhaust port of an
engine of the automobile.
21
6. The catalyst system as claimed in claims 1, wherein the metal substrate is a
longitudinal structure of monoliths.
7. The catalyst system as claimed in claim 1 or 6, wherein the wash coat layers are
5 applied on a single substrate.
8. The catalyst system as claimed in claims 1 or 6, wherein the substrate having the
oxygen storage component of Ceria and refractory metal oxide components is one
or more of Niobium, Molybdenum, Tantalum, Tungsten and Rhenium.
10
9. A process for preparing the catalyst for aftertreatment of automobile exhaust gas
comprising steps of
preparing and coating of one or more wash coat layers on one or more substrate
15 forming two or more bricks, comprising
a. diluting the soluble noble metal solution with water to reach incipient
wetness.
b. Impregnating the alumina, cerium and zirconium oxide particles on the
Noble metal solution.
20 c. Addition of the water and another soluble noble metal solution to form
a slurry.
d. The slurry is applied on a metal substrate.
e. Drying and calcination at a temperature of 500oC -600°C for at least 2
hours.
25 wherein the slurry for the first and second wash coat region has at least 40 % solid
content, the slurry for the third wash coat region has at least 30 % solid content,
the first brick located in the upstream, comprises first wash coat layer and second
wash coat layer,
the second brick located in the downstream comprises the third wash coat layer,
22
characterized in that the thickness ratio for wash coat layer of the first brick and
second brick is from 1.25 to 1.35.
10. The process as claimed in claims 9, wherein the noble metal loading in first brick is
45 to 50 g/ft3
, and in second brick is 25 to 30 g/ft3
.
5
11. The process as claimed in claim 9 or 10, wherein Pd/Rh weight ratio in the first
brick is in a range of 2.5 to 2.8; and Pd/Rh weight ratio in the second brick is in a
range of 1/5 to 1/3.
10 12. The process as claimed in any one of claims 9 to 11, wherein the two bricks system
are together with 50 mm away from the engine pipe in motorcycle.
13. The process as claimed in claim 9, wherein the metal substrate is a longitudinal
structure of monoliths.
15
14. An exhaust gas treatment system for treating the exhaust gas of an automobile
comprising a one or more catalyst system comprising one or more substrate and one
or more wash coat layers on the substrate forming two or more bricks, wherein
the first brick located in the upstream, comprises first wash coat layer and second
20 wash coat layer, coated on the first substrate,
the second brick located in the downstream comprising of third wash coat layer,
coated on second substrate,
wherein the wash coat layers comprising noble metal selected from Pt, Pd and Rh,
the first substrate and/or the second substrate having a metal substrate comprising
25 oxygen storage component and refractory metal oxide,
characterized in that the thickness ratio for wash coat layer of the first brick and the
second brick is from 1.25 to 1.35.
15. An exhaust gas treatment process for treating the exhaust gas of an automobile
30 comprising steps of
23
sending the exhaust gas from the automobile engine to an exhaust gas treatment
system to convert the harmful hydrocarbons (HC), carbon monoxide (CO) and
nitrogen oxides (NOx) into less harmful components to meet the emission norms,
wherein the exhaust gas treatment system is the system as claimed in claims 14.
5
16. Use of the catalyst system as claimed in claim 1 for aftertreatment of automobile
exhaust gas.
17. Use of the catalyst system as claimed in claim 16 having reduced back pressure and
10 optimum usage of the noble metals.