Claims:1. A nanoporous three-way catalyst composition for the effective removal of carbon
monoxide, hydrocarbons and nitrogen oxide gases comprising active ingredients in the
ratios specified as follows: 24 – 37% ceria; 30 – 47% zirconia; 3 – 22% alumina; 3 –
5% lanthana; 0 – 2% neodymia; 3 – 5% yttria; 0 – 5% zeolite and precious metals such
as 0 – 0.3% palladium; 0 – 0.15% rhodium and 0 – 0.1% platinum
2. A nanoporous three-way catalyst composition for the effective removal of carbon
monoxide, hydrocarbons and nitrogen oxide gases further comprising thermal
stabilizers in the ratios specified as follows: 1– 3% barium; 0 – 2.2% calcium; 0 – 1%
ruthenium; 0 – 1% iron; 0 – 0.25% tin; 0 – 2% nickel; 0 – 2% molybdenum, 0 – 1%
samarium;
3. The nanoporous three-way catalyst composition as claimed in claims 1 and 2 wherein
the alumina is a lanthana modified alumina, comprising 2.5 – 5% of lanthana.
4. The nanoporous three-way catalyst composition as claimed in claims 1 and 2 wherein
the alumina is a ceria modified alumina comprising 6 – 30% of ceria.
5. The nanoporous three-way catalyst composition as claimed in claims 1 and 2 wherein
the zeolite employed is selected from a group of commercially available zeolites which
includes Ultra StableY, ZSM-5, Beta-zeolites, Faujasite, X zeolite, Type Y zeolite,
Ferrierite and KL zeolite or mixtures thereof, with or without alkali metals, wherein the
alkali metal content will be in the range of 2-20 wt% of the said zeolite.
6. The nanoporous three-way catalyst composition as claimed in claims 1 and 2, wherein
the ceria and zirconia is a nanocomposite ceria stabilized zirconia.
7. The nanoporous three-way catalyst composition as claimed in claims 1 and 2, wherein
the ceria stabilized zirconia has a composition of 30 - 50% by weight of ceria, 0 – 2%
by weight of neodymia, 3 – 5% by weight of lanthana, 3 – 5% by weight of yttria, 50 -
90% by weight of zirconia
8. The nanoporous three-way catalyst composition as claimed in claim 5 wherein the ceria
stabilized zirconia is an oxide or hydroxide , Description:Field of the invention
The subject invention relates to a three-way catalyst composition comprising small amounts of
precious and active materials in its nanoporous three-way catalyst composition for the effective
removal of carbon monoxide, hydrocarbons and nitrogen oxide gases from motorcycles and three
wheeled vehicles fueled with CNG, LPG, gasoline or ethanol blended gasoline operating in
stoichiometry or lean conditions. The subject invention is prepared with the mixture of
nanocomposite materials, thermal stabilizers and precious group metals which are coated onto a
honeycomb substrate to produce a three way catalyst. The wash coat composition constituting the
subject invention broadly comprises the following active materials:
1. 24 – 37% Ceria;
2. 30 – 47% Zirconia;
3. 3 – 22% Alumina
4. 3 – 5% Lanthana;
5. 0 – 2% Neodymia;
6. 3 – 5% Yttria;
7. 0 – 5% Zeolite
The wash coat composition of this invention also comprises the following thermal stabilizers:
1. 1 – 3% Barium;
2. 0 – 2.2% Calcium
3. 0 – 1% Ruthenium;
4. 0 – 1% Iron;
5. 0 – 0.25% Tin;
6. 0 – 2% Nickel;
7. 0 – 2% Molybdenum,
8. 0 – 1% Samarium;
The wash coat composition of this invention also comprises the following precious metals
1. 0 – 0.3% Palladium;
2. 0 – 0.15% Rhodium;
3. 0 – 0.1% Platinum
Background of the invention
The subject invention relates to the preparation of a catalyst composition consisting of active
materials, thermal stabilizers and precious metals. The catalyst composition prepared is used for
the removal of exhaust gases such as carbon monoxide, hydrocarbons and nitrogen oxide emitted
from motorcycles and three wheeled vehicles. The hydrocarbons present in the exhaust gases are
partially oxidized as a result of their internal combustion. The carbon monoxide and the
hydrocarbons present in the exhaust gases react in the presence of oxygen according to the
following equations:
CO + 0.5O2 ? CO2
CxHy + (x+y/2)O2 ? xCO2 + y/2H2O
The nitrogen oxide present in the exhaust gas react with the carbon monoxide according to the
following equation:
NO + CO ? 0.5N2 + CO2
Additionally, the catalyst composition employed must also be capable of performing at a
temperature of about 200 degree Celsius as well as at high temperatures of up to 900 degree Celsius
and it must be hydrothermally stable.
The use of active materials, thermal stabilizers and precious metals in the treatment of exhaust
gases generated by motorcycles and three wheeled vehicles is known to exhibit satisfactory
performance for oxidizing carbon monoxides, hydrocarbons and reducing nitrogen oxide gases
when the engine is operated in stoichiometry or lean conditions. Conventional catalysts also
employ a substantial amount of precious metals to satisfactorily remove toxic exhaust gases
generated by motorcycles.
The subject invention mainly aims at preparing a three-way catalyst composition comprising active
materials, thermal stabilizers and small amount of precious metals. The advanced wash coat
composition is developed to effectively convert CO, HC and NOx with lower amount of precious
metals.
Catalytic activity is a function of several factors which includes the following:
(i) Rate of diffusion of the gases from exhaust
(ii) Mass transfer limitations
(iii) Heat resistance of the catalyst
If there is a fluctuation in any of the aforementioned factors, it can lead to an inactivation of the
catalyst during over heating or ageing of the engine. It is found that among the aforementioned
factors, conventional catalysts exhibit insufficient thermal stability which can inactivate the
performance of the catalyst. The subject invention also aims at improving the thermal stability of
the catalyst composition thereby improving the activity of the catalyst for the effective removal of
toxic gases emitted by vehicles, more specifically motor cycles and three wheeled vehicles.
US Patent 3990998 relates to a high surface area multilayered oxide support coated with ruthenium
of the type Ru-MgO-MgAl2 O4 -MgAl2 O4 +Mg2 SiO4 constituting the core. The system
comprises ruthenium coupled along with free MgO, on pre-reacted alumina which is thereafter
applied onto a monolithic substrate. The core of the prior art constitutes ruthenium coupled with
magnesium, alumina and silica, whereas the wash coat composition in the subject invention
comprises active materials such as 24 – 37% Ceria, 30 – 47% Zirconia, 3 – 22% Alumina, 3 – 5%
Lanthana, 0 – 2% Neodymia, 3 – 5% Yttria, thermal stabilizers such as 1 – 3% Barium, 0 – 1%
Ruthenium, 0 – 1% Iron, 0 – 0.25% tin, 0 – 2% Nickel, 0 – 2% Molybdenum, 0 – 1% Samarium
and precious metals such as 0 – 0.3% Palladium, 0 – 0.15% Rhodium, 0 – 0.1% Platinum,
rendering the subject invention different from the prior art and more effective in comparison to the
prior art.
US Patent 5116800 relates generally to catalysts used to reduce the amount of hydrocarbons,
carbon monoxide, and nitrogen oxides in automotive exhaust gas, and in particular to promoted
delta-alumina supported catalysts which have high durability although they do not contain cerium
oxide and which, in addition, minimize the amount of hydrogen sulfide in the exhaust gas without
the use of nickel oxide teaches the use of over layer which comprises 15 – 30% alumina, 0.3 – 6%
barium, 0 – 8% lanthana, 0-6% ZrO2, 0.01 – 0.9% palladium; 0.005 – 0.3% rhodium based on the
total weight of the catalyst
US Patent 7399728 relates to a catalyst formulation which includes a poison adsorbing material
and a catalyst material. The poison adsorbing material comprises large particles having an average
major diameter of greater than or equal to about 2.0 micrometers. The catalyst material comprises
a precious metal support comprising small particles having an average diameter of less than or
equal to about 1.0 micrometers. The prior art uses large amounts of precious metals in the catalyst
composition, which is between the range of 2 to 24 % in comparison to the miniscule amounts of
precious metals used in the subject invention. The use of the very low amounts of precious metals
renders the subject invention economically more viable than the prior art.
Summary of the invention
This invention relates to a three-way catalyst composition for the effective removal of carbon
monoxides, hydrocarbons and nitrogen oxide gases in the exhaust gases emitted from motorcycles
or three wheeled vehicles fueled with CNG, LPG, gasoline, or ethanol blended gasoline operating
in stoichiometry or lean conditions. The subject invention is prepared by blending nanocomposite
active materials, thermal stabilizers and precious group metals which are in turn coated onto a
honeycomb substrate to produce a catalyst sample. The nanoporous wash coat composition in the
aforementioned catalyst is found to be active at high temperatures greater than 900 degree Celsius
and is found to be highly heat resistant as it functions effectively in the event the engine undergoes
overheating.
Brief description of the figures
The present disclosure can be better understood by referring to the following figures.
Fig. 1 is the transmission electron microscope images obtained for the fresh three-way catalyst
working embodiment examples 1 – 4
Fig. 2 is a graph of pore size distribution for fresh three-way catalyst samples obtained by plotting
pore volume in cubic centimeter per gram in vertical axis and pore size in nanometer for the
working embodiment examples 1 – 4 in the horizontal axis
Fig. 3 is a graph of BET-surface area for fresh and aged three-way catalyst samples obtained by
plotting BET-surface area values obtained in square meter per gram of catalyst in vertical axis and
working embodiment examples 1 – 4 in the horizontal axis
Fig. 4 is a graph of oxygen storage capacity for fresh and aged three-way catalyst samples obtained
by plotting the values obtained in micromoles of oxygen per gram of catalyst in vertical axis and
working embodiment examples 1 – 4 in the horizontal axis
Fig. 5 is a graph of conversion of CO, HC and NOx measured at 450 deg C for fresh catalysts
obtained by plotting conversion values measured in volume% in vertical axis and working
embodiment examples 1 – 4 in the horizontal axis
Detailed description of the invention:
The subject invention of wash coat composition is prepared by blending nanocomposite active
materials, thermal stabilizers and precious group metals, which is in turn coated onto a honeycomb
substrate to produce a catalyst sample. The wash coat composition constituting the subject
invention broadly comprises the following active materials:
1. 24 – 37% Ceria;
2. 30 – 47% Zirconia;
3. 3 – 22% Alumina
4. 3 – 5% Lanthana;
5. 0 – 2% Neodymia;
6. 3 – 5% Yttria;
7. 0 – 5% Zeolite
The wash coat composition of this invention also comprises the following thermal stabilizers:
1. 1 – 3% Barium;
2. 0 – 2.2% Calcium
3. 0 – 1% Ruthenium;
4. 0 – 1% Iron;
5. 0 – 0.25% tin;
6. 0 – 2% Nickel;
7. 0 – 2% Molybdenum,
8. 0 – 1% Samarium;
The wash coat composition of this invention also comprises the following precious metals:
1. 0 – 0.3% Palladium;
2. 0 – 0.15% Rhodium;
3. 0 – 0.1% Platinum
The three-way catalyst is comprising the aforementioned wash coat composition is intended for
use for the effective removal of CO, HC and NOx present in the exhaust gas emitted by
motorcycles and three wheeled vehicles operating in stoichiometry or lean conditions.
The wash coat composition prepared is thereafter coated onto a honeycomb substrate, preferably
a metallic substrate specially designed for motorcycles and three wheeled vehicles due to its easy
canning and mechanical durability. The aforementioned metallic substrate should be a heat
resistant metal alloy in which iron is a major component.
Alumina comprises a major portion of the wash coat composition for exhaust gas removal. While
gamma alumina is the preferred support, other forms of alumina such as delta, eta and theta may
also be used. The alumina used in this invention is preferably ceria modified alumina and / or
lanthana modified alumina. The ceria modified alumina comprises about 4 - 26 wt% of ceria,
whereas the lanthana modified alumina comprises 2.5 – 5 wt% of lanthana.
Further, the alumina used in this invention is preferably modified with barium, magnesium, cobalt,
copper, manganese, copper, tellurium, iron, molybdenum, tungsten, strontium or tin which act as
thermal stabilizers. Thermal stabilizers, stabilize the structure of the alumina employed. These
stabilizers are known for stabilizing the specific surface area of the alumina as they inhibit the
phase transformation of alumina at high temperatures. Thus preventing the phase transformation
of alumina when the catalyst is exposed to high temperatures.
The wash coated metallic honeycomb substrate acts as a three-way catalyst for improving the
conversion of nitrogen oxides, carbon monoxide and hydrocarbons under stoichiometry and lean
conditions. Precious metals such as platinum, palladium, rhodium and ruthenium are loaded in
ceria-zirconia or alumina or lanthana modified alumina or zeolites or partially on all the four
materials. The precious metals (Pt, Pd, Rh, Ru) incorporated are dispersed throughout the porous
support and consequently create a high metal surface area thereby rendering the entire precious
metals incorporated in wash coated honeycomb substrate available for reduction of nitrogen oxide
and oxidation of carbon monoxide and hydrocarbons.
The combination of ceria and zirconia forms part of the active material support in the wash coat
composition of the subject invention. The ceria-zirconia composite oxide is often referred to as an
oxygen storage component because it is considered to have the capability to release oxygen when
the catalyst is exposed to reducing conditions and store when exposed to oxidizing conditions.
Ceria-zirconia tetragonal phase hydroxide or oxide when incorporated with dopants is stable even
after exposed to high temperatures. It is known to also stabilize and promote the activity of
precious metals in addition to stabilizing the active material support. The dopants include La, Y,
Nd, Sm, Pr, Ba, Sr, Ca, Na, K, Bi, Fe, Ni, Mo, Co, Mn, Sn, Ru, Te and Ir. Ceria stabilized zirconia
used in this invention preferably comprises 30-50% ceria, 0-2% neodymia, 3-5% lanthana, 3-5%
yttria and 50-90% zirconia.
Zeolites exhibit a combination of micropores and high surface area which forms an important part
of the wash coat composition and are found to be useful for adsorbing hydrocarbon and nitrogen
oxide emissions during the cold start. Suitable zeolites are aluminosilicates having silica to
alumina ratio of less than 40. Zeolites for the present invention have been selected from a
commercial list of zeolites such as:
a) Ultra Stable Y,
b) Zeolite Socony Mobil-5,
c) Beta-zeolites,
d) Faujasite,
e) X zeolite,
f) Ferrierite.
g) KL zeolite
Preferably, the KL zeolite exhibiting silica-to-alumina ratio of greater than or equal to 4 and having
incorporated therein about 19% of potassium or sodium or lithium by weight is used. The wash
coat typically contains at least about 0 – 5 wt% of zeolite incorporated with metal oxides,
preferably 0 – 20%. Examples of metal oxides used are as follows:
a) sodium oxide,
b) lithium oxide,
c) potassium oxide,
d) barium oxide,
e) lanthanum oxide,
f) magnesium oxide,
g) manganese oxide
Mass emission performance:
The mass emission performance of the catalyst sample should be measured in order to assess the
emission limit of the exhaust gases emitted pursuant to the use of the catalyst sample produced
using the subject invention.
The catalyst sample is fitted in the vehicle exhaust pipe and then preconditioned by running the
vehicle at “widely open throttle” for about 30 - 120 minutes. The term “widely open throttle” refers
to the maximum intake capacity of air and fuel in an internal combustion engine when the throttles
inside the vehicle are kept widely open. The catalyst sample once pre-conditioned is thereafter
kept for soaking for 6 to 30 hours and tested in accordance with the requisites prescribed by the
World Motorcycle Test Cycle (WMTC). The exhaust gases such as carbon monoxide, nitrogen
oxide and hydrocarbon emissions generated by the vehicle used for testing are collected in a
sampling bag during the test cycle and is analyzed on an equipment commercially known as the
Horiba CVS 7400D to understand the exhaust gas flow rate and the exhaust gas concentration,
while the distance that the vehicle has run is calculated using a chassis dynamometer. The mass
emission performance of the vehicle is thereafter calculated in gram per kilometer by measuring
the exhaust gas flow rate, exhaust concentration and distance run.
Light-off characteristics and conversion efficiency:
The light-off temperature (LOT) of the catalyst sample is characteristic of the wash coat
composition and amount of precious group metals loaded in the catalyst. This needs to be measured
as it indicates the temperature at which 50% conversion of carbon monoxide, hydrocarbons and
nitrogen oxide is achieved for the given catalyst sample. The wash coated metallic honeycomb
catalyst sample is introduced into a modal gas tester. The metallic honeycomb substrate used in
the catalyst sample should have dimensions of 20 (diameter) X 30 millimeter in length with a cells
per square inch (“CPSI”) of 200. The simulated exhaust gas composition used for catalyst testing
is given below:
a) 14 % carbon dioxide
b) 0.9% carbon monoxide
c) 0.05% nitrogen oxide
d) 0.089% propylene
e) 0.95% oxygen
f) 10% water
g) 0.303% hydrogen
h) balance nitrogen
The catalyst sample is introduced into a quartz reactor (modal gas reactor). The simulated exhaust
gas mixture as aforementioned is thereafter passed through a quartz reactor at a gas hourly space
velocity of 100,000 per hour. The air to fuel ratio (A/F) of the exhaust gas is maintained at 1.004
lambda. The temperature of inlet of the catalyst increased from 100 to 450 deg C with a rate of 10
deg C/min for determining the light-off temperatures of CO, HC and NOx. The conversion of
reactants (CO, HC, NOx) was measured at 450 deg C using Horiba Mexa-584L portable gas
analyzer or FT-IR.
Working embodiments:
Example-1: The nanoporous three-way catalyst wash coat composition is prepared by dissolving
mixture of palladium nitrate, rhodium nitrate, ruthenium chloride, samarium nitrate, stannous
chloride, iron nitrate, neodymium nitrate and barium acetate in water to make a solution. The
solution obtained is thereafter impregnated onto the wash coat support of ceria-zirconia oxide. The
precious metals and other materials used in the wash coat composition are in the range of 0.053%
palladium, 0.026% rhodium, 0.1% iron, 0.01% ruthenium, 0.025% tin, 0.1% samarium, 1% nickel,
2% neodymia, 2% calcium and 3% barium. The wash coat support of ceria-zirconia impregnated
with the above solution was then dried at 100 degree Celsius for 1 hour and then calcined at 500
degree Celsius for 3 hours. The calcined wash coat sample was then mixed with water, tetramethyl
ammonium hydroxide, ammonium hydroxide, nitric acid, alumina, KL-zeolite, acetic acid and
then wet-milled to particles having mean particle size of less than 5 microns. The wash coat slurry
prepared by this method is characterized to have nanoparticles with a size of 6 – 10 nm (Fig. 1),
nanoporous properties with a pore size range of 5 – 100 nm (Fig. 2), BET-surface area of 109 m2/g
(Fig. 3) and OSC of 157 micromoles oxygen per gram of wash coat (Fig. 4). A metallic honeycomb
substrate with dimensions of 40 (diameter) X 150 (length), mm; 100 cpsi was coated with the wash
coat by dipping and vacuum knifing method. The wash coated substrate was then dried at 100
degree Celsius for 3 hours and then calcined at 500 degree Celsius for 2 hours and then tested for
mass emission on chassis dynamometer (CD). In addition small size catalysts, 20 (diameter) X 30
(length), mm; 200 cpsi are prepared and tested on modal gas tester showed a conversion of 96%
CO, 94% HC and 99% NOx at 450 deg C (Fig. 5).
Comparative example:
The procedure employed in Example 1 was repeated for preparing comparative sample, except
that iron, ruthenium, tin, samarium, nickel and zeolite were not used. The wash coat slurry prepared
by this method is characterized to have BET-surface area of 107 m2/g and OSC of 121 micromoles
oxygen per gram of wash coat. A small size catalyst, 20 (diameter) X 30 (length), mm; 200 cpsi
was prepared and tested on modal gas tester showed a conversion of 89% CO, 88% HC and 89%
NOx at 450 deg C.
Example-2: The nanoporous three-way catalyst wash coat composition is prepared by dissolving
and mixing 0.13% equivalent of palladium nitrate, 0.07% equivalent of rhodium nitrate, 0.05%
iron, 0.1% nickel, 4.2% lanthana, 3.5% yttria; 3% calcium hydroxide and 2.5% barium acetate in
water to make a solution. The solution obtained is thereafter added onto the mixture of
nanocomposite materials of ceria-zirconia and alumina and then mixed for about 2 hours. This
mixture is mixed with acetic acid, ammonia, tetraethylammonium hydroxide and binders to
produce a wash coat sample and then mixed for about 10 hours for functionalization and
compatibilization. The wash coat mixture is then optionally mixed with ZSM-5, acetic acid and
then wet-milled to particles having mean particle size of less than 5 microns. The wash coat slurry
prepared by this method is characterized to have nanoparticles with a size of 4 – 10 nm, nanoporous
properties with a pore size range of 1 – 100 nm, BET-surface area of 97 m2/g and OSC of 153
micromoles oxygen per gram of wash coat. A metallic honeycomb substrate with dimensions of
40 (diameter) X 150 (length), mm; 100 cpsi was coated with the wash coat by dipping method.
The wash coated substrate was then dried at 100 degree Celsius for 4 hours and then calcined at
500 degree Celsius for 2 hours and then tested for mass emission on chassis dynamometer (CD).
In addition small size catalysts, 20 (diameter) X 30 (length), mm; 200 cpsi are prepared and tested
on modal gas tester showed a conversion of 96% CO, 94% HC and 99% NOx at 450 deg C.
Example-3: Nanoporous wash coat composition for two wheelers and three wheelers fueled with
gasoline is prepared by dissolving and mixing 0.025% equivalent of platinum sulphite acid, 0.21%
equivalent of palladium nitrate, 0.08% equivalent of rhodium nitrate, 0.01% manganese, 0.2%
nickel, 0.2% neodymia, 4.6% lanthana, 4.5% yttria; 0.1% molybdenum, and 2% barium sulphate
in water to make a solution. The solution obtained is thereafter added onto the mixture of materials
of ceria-zirconia and alumina and then mixed for about 2 hours. This mixture is mixed with acetic
acid, ammonia, tetrapropyl ammonium hydroxide and binders to produce a wash coat and then
mixed for about 10 hours for homogenization. The wash coat mixture is then mixed with 1.6%
KL-zeolite, acetic acid and then wet-milled to particles having mean particle size of less than 5
microns. The wash coat slurry prepared by this method is characterized to have nanoparticles with
a size of 5 – 9 nm, nanoporous properties with a pore size range of 5 – 100 nm, BET-surface area
of 93 m2/g and OSC of 154 micromoles oxygen per gram of wash coat. A metallic honeycomb
substrate with dimensions of 40 (diameter) X 150 (length), mm; 100 cpsi was coated with the wash
coat by dipping method. The wash coated substrate was then dried at 100 degree Celsius for 3
hours and then calcined at 550 degree Celsius for 3 hours and then tested for mass emission on
chassis dynamometer (CD). In addition small size catalysts, 20 (diameter) X 30 (length), mm; 200
cpsi are prepared and tested on modal gas tester showed a conversion of 95% CO, 96% HC and
98% NOx at 450 deg C.
Example-4: Nanoporous wash coat composition for two wheelers and three wheelers fueled with
gasoline is prepared by dissolving and mixing 0.015% Pt equivalent of platinum sulphite acid,
0.15% Pd equivalent of palladium nitrate, 0.15% Rh equivalent of rhodium nitrate, 0.2% nickel,
3% lanthana, 4% yttria; 2.2% calcium sulphate and 1% barium in water to make a solution. The
solution obtained is thereafter added onto the mixture of materials of ceria-zirconia and alumina
and then mixed for about 2 hours. This mixture is mixed with acetic acid, ammonia and colloidal
alumina to produce a wash coat and then mixed for about 10 hours for homogenization. The wash
coat mixture is then mixed with 5% beta-zeolite, tetrabutyl ammonium hydroxide, acetic acid and
then wet-milled to particles having mean particle size of less than 5 microns. The wash coat slurry
prepared by this method is characterized to have nanoparticles with a size of 4 – 9 nm, nanoporous
properties with a pore size range of 5 – 100 nm, BET-surface area of 95 m2/g and OSC of 156
micromoles oxygen per gram of wash coat. A metallic honeycomb substrate with dimensions of
20 (diameter) X 30 (length), mm; 200 cpsi was coated with the wash coat by dipping method. The
wash coated substrate was then dried at 100 degree Celsius for 2 hours and then calcined at 540
degree Celsius for 2 hours and then tested on modal gas tester showed a conversion of 97% CO,
97% HC and 99% NOx at 450 deg C.