Title of Invention	A METHOD FOR THE PREPARATION OF A HIGHLY STABLE WASHCOAT USEFUL AS A SUPPORT FOR NOBLE METAL CATALYSTS.
Abstract	A method for the preparation of a highly stable washcoat useful as a support for noble metal catalysts by boiling the codierite monolith in a diluted acid such as nitric acid, drying and calcining at a temperature in the range of 300°C-600°C for a time period of 2 hours, dipping the above said treated monolith in a solution of aluminium salt at a temperature in the range of 60°C-80°C for a time period of 1-10 min to form a green coating on the said monolith, heat treating the green coated monolith to obtain the first washcoat monolith, contacting the above said first wash coated monolith with a slurry of aluminium oxide yielding species rare earth oxide loaded gamma alumina and nitric acid in an aqueous medium, separating the above monolith from the slurry and heat treating to form a highly stable second waschoat.

Title of Invention

A METHOD FOR THE PREPARATION OF A HIGHLY STABLE WASHCOAT USEFUL AS A SUPPORT FOR NOBLE METAL CATALYSTS.

Abstract

A method for the preparation of a highly stable washcoat useful as a support for noble metal catalysts by boiling the codierite monolith in a diluted acid such as nitric acid, drying and calcining at a temperature in the range of 300°C-600°C for a time period of 2 hours, dipping the above said treated monolith in a solution of aluminium salt at a temperature in the range of 60°C-80°C for a time period of 1-10 min to form a green coating on the said monolith, heat treating the green coated monolith to obtain the first washcoat monolith, contacting the above said first wash coated monolith with a slurry of aluminium oxide yielding species rare earth oxide loaded gamma alumina and nitric acid in an aqueous medium, separating the above monolith from the slurry and heat treating to form a highly stable second waschoat.

Full Text	The present invention relates to a method for the preparation of a Light stable washcoat useful as a support for noble metal catalysts. More particularly the invention relates to the preparation of a washcoated substrate having strong adherence of washcoat with the substrate suitable for use as support for catalysts employed for the reduction of carbon monoxide, hydrocarbons and nitrogen 6xides from exhaust gas of internal combustion engines. In order to meet the stringent emission standards for carbon monoxide, unburnt hydrocarbons and nitrogen oxides contaminants in automotive exhaust gas of petrol driven vehicles, catalytic converters are fitted in the exhaust gas line of the vehicle. The catalyst in the converter simultaneously converts the noxious carbon monoxide, hydrocarbons and nitrogen oxides to harmless carbon dioxide, water vapour and nitrogen. This type of catalyst is generally referred to as "three way conversion" or TWC catalyst. The three way conversion catalyst essentially consists of a washcoated substrate impregnated with catalytically active component. The washcoats. are made essentially of aluminium oxide and aluminium oxide yielding species. Noble metals are commonly used as the catalytically active component. The washcoated substrate provides support for a wide variety of catalysts including a TWC catalyst. The washcoat can be impregnated with catalyst precursors which on calcination form highly dispersed catalytic material. The high surface area provided by the washcoat enhances the activity of the catalyst. A TWC catalyst is constantly exposed to varying conditions during operation e.g. temperature increase from ambient at the beginning of the vehicle operation, fluctuation of exhaust flow rate and composition due to change in driving speed and style. The exhaust gas temperature can reach 80Q°C or above, arid such elevated temperatures cause the alumina of the washcoat to undergo thermal degradation caused by phase transformation. This results in a substantial reduction in the surface area of the alumina with a consequent loss of the surface area of the catalyst and a corresponding decrease in the activity of the catalyst. Alumina of the washcoat can be stabilized against such thermal degradation by contacting it with salts of zirconium, titanium, alkaline earth metals, rare earth metals followed by firing to form a homogeneous dispersion of the metal oxides on alumina. TWC noble metal catalysts, typically use gamma-alumina and sometimes ceria stabilized and / or lanthana stabilized gamma-alumina as support material. It is known that the addition of ceria to alumina also promotes the performance of the catalyst by working as an oxygen storage under transient conditions, catalytic promoter of precious metals for reactions like water gas shift and structural promoter for the stabilization of noble metals and alumina against sintering. A TWC catalyst is also subjected to severe mechanical and thermal shocks during operation. The temperature can abruptly rise from ambient to above 800°C and fall back sharply. Such shocks can cause a part of the washcoat material to chip off from the substrate with a subsequent loss in the activity of the catalyst. Such catalysts are bound to have a poor durability. It is therefore essential to apply the washcoat on the substrate in a manner that under severe thermal and mechanical shock conditions as encountered in the operation of the TWC, the washcoat is not even partially removed from the substrate. More specifically the washcoat should be applied in a manner that it adheres strongly with the substrate. The washcoat when applied to the substrate in accordance with the present invention, has strong adherence with the substrate, has a high surface area and it serves as an excellent support for the catalytically active components as will be seen from the description that follows. Application of a washcoat layer on to a ceramic monolith substrate for preparing support for catalyst used in automotive catalytic converter is however known to this art. Reference may be made to US patent no. 4231900 in which a method is claimed for forming a high surface area coating on the surface of a monolith catalyst carrier. In US patent no. 4564608 is claimed a method for producing a monolith catalyst for use in automotive exhaust system. The method of producing alumina slurry liquid uses water, aluminium-nitrate powder instead of acid alkali to prevent the alumina coat layer on the monolith from coming off in the high temperature. Reference can also be made to US patent no. 5212130 in which a high surface area washcoated substrate was produced by coating the substrate with a slurry consisting of ionizable compound, an aluminium oxide and a medium. The ionizable compound has been used to increase the stability of the washcoat. Reference may be made to US patent no. 3928239 in which is claimed a method for production of a catalyst for purification of exhaust gases of internal combustion engines. The slurry is formed from an alumina sol solution and finely powdered alumina containing at least 50% by weight of rho-alumina. However the conventional supports prepared in the forgoing manner can perform satisfactorily only under relatively mild conditons, but when used under very severe conditions of frequent tremperature fluctuations from ambient to above 800°C with severe mechanical shocks as is encountered in the service for automobiles, the support will gradually deteriorate and the catalyst thereupon will not maintain sufficient activity over a period of use. Moreover none of the referred literature describe a method for the preparation of washcoat which simultaneously has a high stability, strong adherence with the substrate and which functions as an excellent support for noble metal catalysts. On the contrary the present invention describes a unique method for the preparation of a washcoat which assures that washcoat is highly stable, has strong adherence with the monolith substrate and which functions as an excellent support for noble metal catalysts. The main object of the present invention is to provides a method for the preparation of a novel washcoat useful as a support for noble metal catalysts, which obviates the drawbacks as detailed above. The main object of the present invention is to provide a method for the preparation of washcoated substrate which has thermal stability to withstand thermal stock. Yet another object of the present invention is to provide a washcoat having high surface area. Still another object of the present invention is to provide a washcoat which can be used a suitable support for catalytically active component. Accordingly the present invention provides a method for the preparation of a Light - washcoat useful as a support for noble metal catalysts which comprises, (i) boiling Ac cordierite monolith in a dilated acid such as nitric acid, drying and calcinated at a temperature in die range of 300°C - 600°C for a time period of abant-2 hr,(ii) copping the above said treated monolith in a solution of ahiminium salt at a temperature in the range of 60°C - 80°C for a time period of 1 min -10 mm to form a green coating,(iii) heat treating the green coated monolith to obtain the first washcoatmenolith( iv)contacting the above said first wash coated monolith with a slurry of aluminium oxide yielding species such as herien described (v) with drawing the above monolith from me slurry and heat treating to form a highly stable second waschoat In an embodiment of the present invention the aluminium salt used is selected from the group consisting of nitrate, carbonate, acetate and sulphate most preferably nitrate. In yet another embodiment of the present invention the rare earth oxides used are ceria and lanthana In yet another embodiment of the present invention the aluminium oxide yielding species is selected from bayerite, boehmite and aluminium isoproponide most preferably boehmite. In yet another embodiment of the present invention the aluminium oxide yielding species such as boehmite is also used as a binder and a theological modifier. In yet another embodiment of the present invention the rare earth oxides load gamma alumina used contains 5 wt%-12 wt% of ceria, 0.5 wt%-2.0 wt% of lanthana and the balance substantially gamma alumina. In still another embodiment of the present invention the washcoat prepared is useful as a support for noble metal catalyst precursors such as platinum & rhodium to yield a highly active catalyst for the conversion of carbon monooxide, hydrocarbons and nitrogen oxides. As indicated above this invention relates to a method for the preparation of a washcoated substrate of high surface area. The washcoat after cyclic exposures to high temperature environment adheres strongly with the substrate. The noble metal catalytic components on the washcoated substrate has a high performance to convert pollutants carbon monoxide, hydrocarbons and nitrogen oxides in the exhaust gas of gasoline vehicles simultaneoulsy to harmless carbon dioxide, water vapour and nitrogen. The washcoated substrate comprises of two distinct coats. A first washcoat and a second washcoat. The first washcoat of the present invention can be formed by a technique in which a concentrated aqueous solution of an aluminium salt is applied to an acid treated substrate followed by firing of the green coated substrate to convert the aluminium salt into aluminium oxide. The aluminium salt can be nitrate, carbonate, acetate, sulphate. The most performed one is the nitrate. According to the present invention the aluminium salt is aluminium nitrate which can yield aluminium oxide on heat treatment. A hot aqueous solution of aluminium nitrate is first prepared. The acid treated substrate is dip coated in the hot concentrated solution of aluminium nitrate. The substrate is removed from the hot solution after 2 to 5 nits drained of the solution and recoated in the solution in the reverse direction. The substrate is finally withdrawn from the solution, drained and striped of the excess solution by blowing hot compressed air over its surface. The green coated substrate is heat treated to remove the solution medium and to decompose the aluminium nitrate. In general heat treating conditions are 100-150°C for 10 to 15 hrs followed by firing at 400 to 450°C for 4 to 10 hours. The green coating according to the present invention is meant the coating prior to heat treatment. Acid treatment of the substrate according to the present invention means the boiling of the substrate in dilute mineral acids for sufficient time followed by heat treatment. Any mineral acid can be used but nitric acid is the preferred one. The substrate can be boiled in dilute nitric acid for 20 to 90 minutes. Generally it is 30 minutes, after which it is heat treated at 350 to 450°C for 2 to 4 hours. The acid treatment dissolves a pan: of alumina and magnesia of the cordierite substrate which helps in the development of pores of radius less than 1000 A. These additional pores help in the subsequent washcoating. The substrate of the present invention can be of any type than can hold the washcoat. It is desirably made of any material that can withstand high temperatures. Some preferred materials are those which have a predominant phase of ceramics, glass ceramics, metal, alumina. The substrate material especially suited for the present invention is cordierite. The substrate can be of any size and shape. The size and shape is generally governed by the engine size and the space available for mounting. Monolith substrates having fine parallel gas flow channels extending from the inlet to outlet are generally preferred. The wall of the channels are washcoated. The washcoat, holds the catalytic material. The gases come in contact with the catalytic material during its passage through the monolith. The channels of the monolith substrate can be any cross sectional shape and size such as trapezoidal, rectangular, square, hexagonal, circular. Such structures may contain 80 to 500 or more channels per square inch of the cross section. The monolith of the present invention contains 400 squarecells per square inch of the cross sectional area. The second washcoat of the present invention is applied over the first washcoated substrate. The washcoat can be formed by a technique in which slurry is made of an alumina yielding species, rare earth oxide loaded alumina, an effective amount of rheological modifiers, binders, surface area stabilizers and a medium. The slurry is applied directly to the first washcoated substrate followed by heat treatment to convert the washcoat material to oxides. According to the present invention the aluminium oxide yielding species is alumina or an alumina precursor which can yield aluminium oxide on heat treatment. The aluminium oxide yielding species can be aluminium hydroxides such as bayerite, aluminium hydroxylated oxides such as boehmite aluminium alkoxide such as aluminium isopropoxide or a combination thereof. Some typical aluminium oxides are gamma, delta, theta, alpha, kappa alumina. Preferred aluminium oxide yielding species are gamma alumina, boehmite, aluminium alkoxide or combination thereof. The alumina utilized in the invention can be gamma, delta, theta or alpha alumina. The most preferred one is gamma alumina. The rare earths used to load the alumina are cerium and lanthanum. The slurry may contain other components which render the slurry suitable for application to a substrate. Such components can be rheological modifiers, binders, surface area stabilizers. Rheological modifiers are compounds which when present in the slurry modify the rheological properties of the slurry to make it suitable for application on the substrate uniformly. It also prevents unsatisfactory coating properties like flaking, chipping and cracking which would subsequently reduce the performance of the catalyst. Rheological modifiers can be rare earth oxides, stearic acid, oxalic acid etc. Boehmite can also function as a rheological modifier and the present invention utilizes boehmite as a rheological modifier. The binders when present in the slurry promote adhension of the washcoat material with the first washcoated substrate. Alumina sols, collidal alumina are examples of binders. The present invention utilizes boehmite as a binder. The binding capacity of boehmite is activated by lowering the pH of the slurry to well below 6. This also helps in lowering the slurry viscosity. The slurry viscosity can be lowered by addition of any mineral acid preferably nitric acid. The lowering of the slurry viscosity also helps in coating the first washcoated substrate with ease. The slurry media can be any media aqueous or non-aqueous in which the slurry components can be easily dispersed the most preferred medium is water. The present invention uses water as a dispersing medium for the slurry components. The second washcoat of the present invention is prepared by first forming a slurry consisting essentially of the aluminium oxide yielding species and aluminium oxide. The aluminium oxide yielding species of the present invention is boehrnite. The boehmite acts as a Theological modifier, a binder and yields aluminium oxide on heat treatment. The aluminium oxide of the present invention is essentially gamma alumina. Prior to forming the slurry the aluminium oxide is impregnated with rare earth compounds and heat treated to convert them into oxides. The rare earth compounds utilized in the present invention are cerium nitrate and lanthanum nitrate. The aluminium oxide will typically contain in wt% of about 5 to 15 ceria and 0.5 to 2 of lanthana and the balance substantially gamma alumina. The slurry of the present invention is formed by adding together sufficient amounts of aluminium oxide yielding species, cerium and lanthanum oxide loaded aluminium oxide and slurry medium to have the desired levels of the washcoat. The amount of slurry medium water is sufficient to disperse the components evenly and to leave a desired level of washcoat material after heat treatment. Sufficient dilute nitric acide is added to the slurry components to reduce the pH of the slurry well below 6 preferably between 3.6 to 3.7. The mixture of the slurry components is ball milled for a sufficient time to reduce particle size and to yield a slurry in which the slurry components are well dispersed and the viscosity of the slurry is adequate to washcoat the first washcoated substrate with ease. Generally the viscosity is between 15 to 30 centipose. The first washcoated substrate is dip coated in the slurry by dipping it in the slurry for sufficient time generally between 2 to 5 minutes, with drawing from the slurry draining the slurry and dipping in the reverse direction. After 2 to 5 minutes the substrate is withdrawn from the slurry, drained, blown with compressed air to strip it of the excess slurry and dried. The coating and drying process is repeated until the desired amount of slurry components are applied on the substrate. The green coated substrate is then heat treated at a sufficient temperature for a sufficient time. The heat treating conditions are about 100 to 150°C for 10 to 20 hours followed by 500 to 850°C for 4 to 8 hours. The heat treatment removes the slurry medium, forms alumina from the alumina yielding species and binds the paniculate of the washcoat to the first over the substrate and to each other. Application of a washcoat on the substrate as described in the present invention affords a high surface area generally between 100m2/gm to 200m2/gm as measured by N2 BET method. The high surface area is fairly well maintained even on heating at temperatures up to 800°C. The high surface area helps is obtaining high dispersion of the catalytic material. The washcoat as applied by the method described in the invention adheres strongly with the substrate and is not removed from the substrate even after subjecting it to thermal cycles. The washcoat of the present invention also functions as an excellent support for catalytically active component and the catalyst has a high efficiency to convert carbon monoxide, hydrocarbons and nitrogen oxides present in petrol vehicle exhaust to harmless components. The catalyst of the present invention are noble metals. The noble metal components are platinum, palladium, rhodium, ruthenium or iridium particularly platinum, palladium and rhodium either alone or in combination. Generally the catalyst will be platinum - rhodium mixtures. The noble metals are applied to the alumina support over the substrate by decomposing a noble metal compound which has been deposited on the support. Preferred compounds would be chloroplantinic rhodium chloride, rhodium nitrate, palladium chloride palladium nitrate. The noble metals may be applied either separately or in combination. The present invention utilizes aqueous solution of platinum and rhodium salts in combination. The mixed solution is used to impregnate the support. The deposited metal precursors on the washcoat are decomposed by heat treatment to yield a highly dispersed catalytically active metal component on the washcoat. The catalyst contains 1.2 to 2.4 gms/lt of Ft and Rh in the ratio of 5to 1. Impregnation of the washcoated monolith with noble metal affords more control on the amount of noble metals loaded on the washcoat, the metal are more efficiently utilized with very little loss of the precious noble metal. The novelty of the present invention live in the preparation of second vvashcoating of slurry containing ceria and lanthana loaded gamma alumina and alumina yielding species over the first wash coat of alumina to give highly thermally stable washcoat to increase the activity of the catalyst in wide range of conditions. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example 1 A. Acid leaching of cordirite monolith Two cordierite monoliths of diameter 92 mm length 125 mm each and having 400 cells per square inch (cpsi) were boiled in 4N nitric acid for 30 mts, dried and calcined at 500°C for 2 hours. B. Preparation of first washcoating 2 Kg of Al(NOj)3 9H2O was mixed with deionized water and boiled to a volume of 1600 cc. The acid treated monoliths of example 1 were 1st washcoated by dipping in the solution of aluminium nitrate at 70 to 80°C for 2 to 5 mts, with drawing from the solution and stripping of the excess solution by blowing hot air over the surface. The green coated monoliths were dried overnight at 100UC followed by firing at 500°C for 2 hours. C. Loading of Alumina with ceria and lanthana 1.5 Kg of gamma alumina was contacted with 1.5 litre solution of cerium and lanthanum nitrate containing 167 gms of CeO2 and 17.5 gins of La2O. The alumina was allowed to soak for 20 mts at room temperature, dried slowly upto 65°C for 2 hours followed by drying overnight at 110°C before firing in air at 500°c for 4 hours. D. Preparation of slurry 126 gms of ceria and lanthanum loaded gamma alumina, 108 gms of boehmite 5.0 cc of concentrated nitric acid and 540 gms of deionized water enough to decrease the solid content in the slurry to about 30-32 percent by weight were placed in a ball mill and run for 60 ints. The resulting slurry had a pH of 3.8 and viscosity of 20 centipoise. E. Preparation of second washcoating For 2nd washcoating the 1st washcoated monoliths were dipped in the slurry prepared as above for 5 to 7mts with drawn from the slurry and dip coated in the reverse direction. After 5 to 7 mts monoliths were drained and the channels were cleared of the excess slurry by jetting air over the surface. The green coated monoliths were dried. The washcoating and drying was repealed till the desired amount of washcoat was obtained on the monolith. The washcoated monoliths were finally dried at 100°c for 15 hours followed by calcination at 80()°C for 4 hours. Example 2 Application of washcoat as support for noble metal catalyst For noble metal impregnation the washcoated monoliths of example 1 were dipped in a mixed aqueous solution of chloroplatinic acid and rhodium nitrate having Pt and Rh in a ratio of 5 to 1 and yielding about 1.8 gms/litre of metals on the washocated monolith. The impregnated monolith were dried overnight at 110°C prior to calcination in a flow of air at 550°C for 4 hours. Example 3 Performance of washcoat material Table 1 below shows the effect of ceria and lanthana addition on surface area preservation of the second washcoat material after heat treating at 550°C and 800°C. The second washcoat material containing ceria and lanthana loaded gamma alumina and boehmite was prepared as given in example 4. The obtained slurry was dried at 100°C for 15 hours followed by calcination at 550°C and 800°C for durations as indicated in the table. Another sample was prepared using similar procedure as given above with the difference that the gamma alumina contained in the sample was not loaded with ceria and lanthana. The N2 BET surface areas of the samples are given in table 1. Table 1 N2 BET surface area m2/gm Calcination Second vvashcoat material Second washocat material Conditions containing ceria and lanthana without ceria and lanthana 550°C for 4 hours 192 235 800°C for 4 hours 120 130 800°C for 8 hours 107 120 800"C For 16 hours 106 100 The results indicate that more surface area is retained in the sample containing ceria and lanthana than for alumina not containing ceria and lanthana. Test 1 Washcoated monolith prepared according to the present invention was subjected to a thermal cycling test for testing the adherence of the washcoat with the monolith. The sample was subjected to three thermal cycles of 60 mts. each (30 mts. heating to about 700°C and 30 mts. cooling to about 100°C ). The results are given below : 1 Weight of washcoated monolith 369 gms before thermal cycling test 2 Weight of washcoated monolith 369 gms after thermal cycling test 3 Loss of washcoat in thermal cycling nil Test 2 The catalyst prepared according to the present invention was tested for its efficiency to convert carbon monoxide, hydrocarbons and nitrogen oxides contained in the exhaust gas of petrol driven vehicle, The catalyst was suitably canned and fitted to the exhaust pipe of a 1500 cc, closed loop fuel injected commercial passenger car. The catalyst fitted car was mounted on a chasis dynamometer and run as per Indian Gasoline vehicle emission test procedure. The exhaust gas was collected and analysed for carbon monoxide, hydrocarbons and nitrogen oxides by Constant Volume Sampler (CVS) system and diluted exhaust gas analyser as per approved procedure. The mass emissions of carbon monoxide, hydrocarbons and nitrogen oxides were measured and converted to gms/km to calculate the conversion efficiency of the catalyst for CO, HC and NOX. The test was repeated on the vehicle without the catalyst. The results of mass emission are given below: Mass emission results CO HC NOX gms/Km gms/Km gms/Km Without catalyst 8.04 0.85 1.21 With catalyst 1.62 0.12 0.09 Conversion0/. 79.8 85.9 92.6 The above results show that the washcoat made according to the present invention functions as an excellent support for holding the catalytically active noble metal component. The catalyst prepared has a very high efficiency to convert CO, HC and NOX present in exhaust gas of petrol driven vehicle. It should be however understood that the present invention has been described in detail with respect to the specific embodiments thereof several variations can be made to the embodiment without departing from the spirit of the invention and the scope of the appended claims. The main advantages of the present invention are that the washcoat when applied on a ceramic monolith substrate by the method of the present invention is highly stable, has strong adherence with the substrate and also functions as an excellent support for noble metal catalysts. The noble metal catalyst prepared on the washcoated monolith has a very high activity for conversion of pollutants in petrol vehicle exhaust gas to inoxious components. We claim : 1. A method for the preparation of a highly stable washcoat useful as a support for noble metal catalysts which comprises: i) boiling the codierite monolith in a diluted acid such as nitric acid, drying and calcinating at a temperature in the range of 300°C-600°C for a time period of 2 hours, ii) dipping the above said treated monolith in a solution of aluminium salt such as herein described at a temperature in the range of 60°C-80°C for a time period of 1-10 min to form a green coating on the said monolith, iii) heat treating the green coated monolith to obtain the first washcoat monolith, iv) contacting the above said first wash coated monolith with a slurry of aluminium oxide yielding species such as herein described, rare earth oxide loaded gamma alumina and nitric acid in an aqueous medium, v) withdrawing the above monolith from the slurry and heat treating to form a highly stable second waschoat. 2. A method as claimed in claim 1 wherein the aluminium salt used is selected from the group consisting of nitrate, carbonate, acetate and sulphate most preferably nitrate. 3. A method as claimed in claims 1-2 wherein the rare earth oxides used are ceria and lanthana. 4. A method as claimed in claims 1-3 wherein aluminium oxide yielding species is selected from the group consisting of bayerite, boehmite and aluminium isoproponide most preferably boehmite. 5. A method as claimed in claims 1-4 wherein the rare earth oxides loaded gamma alumina used is comprising 5 wt%-12 wt% of ceria, 0.5 wt%-2.0 wt% of lanthana and the balance of gamma alumina. 6. A method as claimed in claims 1 -5 wherein the washcoat prepared is useful as a support for noble metal catalyst precursors such as platinum and rhodium or a mixture thereof to yield a highly active catalyst for the conversion of carbon monoxide, hydrocarbons and nitrogen oxides. 7. A method for the preparation of a highly stable washcoat useful as a support for noble metal catalysts substantially as herein described with reference to the examples.

Full Text

The present invention relates to a method for the preparation of a Light stable washcoat useful as

a support for noble metal catalysts.
More particularly the invention relates to the preparation of a washcoated substrate having strong adherence of washcoat with the substrate suitable for use as support for catalysts employed for the reduction of carbon monoxide, hydrocarbons and nitrogen 6xides from exhaust gas of internal combustion engines.
In order to meet the stringent emission standards for carbon monoxide, unburnt hydrocarbons and nitrogen oxides contaminants in automotive exhaust gas of petrol driven vehicles, catalytic converters are fitted in the exhaust gas line of the vehicle. The catalyst in the converter simultaneously converts the noxious carbon monoxide, hydrocarbons and nitrogen oxides to harmless carbon dioxide, water vapour and nitrogen. This type of catalyst is generally referred to as "three way conversion" or TWC catalyst. The three way conversion catalyst essentially consists of a washcoated substrate impregnated with catalytically active component. The washcoats. are made essentially of aluminium oxide and aluminium oxide yielding species. Noble metals are commonly used as the catalytically active component. The washcoated substrate provides support for a wide variety of catalysts including a TWC catalyst. The washcoat can be impregnated with

catalyst precursors which on calcination form highly dispersed catalytic material. The high surface area provided by the washcoat enhances the activity of the catalyst.
A TWC catalyst is constantly exposed to varying conditions during operation e.g. temperature increase from ambient at the beginning of the vehicle operation, fluctuation of exhaust flow rate and composition due to change in driving speed and style. The exhaust gas temperature can reach 80Q°C or above, arid such elevated temperatures cause the alumina of the washcoat to undergo thermal degradation caused by phase transformation. This results in a substantial reduction in the surface area of the alumina with a consequent loss of the surface area of the catalyst and a corresponding decrease in the activity of the catalyst. Alumina of the washcoat can be stabilized against such thermal degradation by contacting it with salts of zirconium, titanium, alkaline earth metals, rare earth metals followed by firing to form a homogeneous dispersion of the metal oxides on alumina.
TWC noble metal catalysts, typically use gamma-alumina and sometimes ceria stabilized and / or lanthana stabilized gamma-alumina as support material. It is known that the addition of ceria to alumina also promotes the performance of the catalyst by working as an oxygen storage under transient conditions, catalytic promoter of precious metals for reactions like water gas shift and structural promoter for the stabilization of noble metals and alumina against sintering.

A TWC catalyst is also subjected to severe mechanical and thermal shocks during operation. The temperature can abruptly rise from ambient to above 800°C and fall back sharply. Such shocks can cause a part of the washcoat material to chip off from the substrate with a subsequent loss in the activity of the catalyst. Such catalysts are bound to have a poor durability. It is therefore essential to apply the washcoat on the substrate in a manner that under severe thermal and mechanical shock conditions as encountered in the operation of the TWC, the washcoat is not even partially removed from the substrate. More specifically the washcoat should be applied in a manner that it adheres strongly with the substrate.
The washcoat when applied to the substrate in accordance with the present invention, has strong adherence with the substrate, has a high surface area and it serves as an excellent support for the catalytically active components as will be seen from the description that follows.
Application of a washcoat layer on to a ceramic monolith substrate for preparing support for catalyst used in automotive catalytic converter is however known to this art.
Reference may be made to US patent no. 4231900 in which a method is claimed for forming a high surface area coating on the surface of a monolith catalyst carrier.

In US patent no. 4564608 is claimed a method for producing a monolith catalyst for use in automotive exhaust system. The method of producing alumina slurry liquid uses water, aluminium-nitrate powder instead of acid alkali to prevent the alumina coat layer on the monolith from coming off in the high temperature.
Reference can also be made to US patent no. 5212130 in which a high surface area washcoated substrate was produced by coating the substrate with a slurry consisting of ionizable compound, an aluminium oxide and a medium. The ionizable compound has been used to increase the stability of the washcoat.
Reference may be made to US patent no. 3928239 in which is claimed a method for production of a catalyst for purification of exhaust gases of internal combustion engines. The slurry is formed from an alumina sol solution and finely powdered alumina containing at least 50% by weight of rho-alumina.
However the conventional supports prepared in the forgoing manner can perform satisfactorily only under relatively mild conditons, but when used under very severe conditions of frequent tremperature fluctuations from ambient to above 800°C with severe mechanical shocks as is encountered in the service for automobiles, the support will gradually deteriorate and the catalyst thereupon will not maintain sufficient activity over a period of use.

Moreover none of the referred literature describe a method for the preparation of washcoat which simultaneously has a high stability, strong adherence with the substrate and which functions as an excellent support for noble metal catalysts.
On the contrary the present invention describes a unique method for the preparation of a washcoat which assures that washcoat is highly stable, has strong adherence with the monolith substrate and which functions as an excellent support for noble metal catalysts.

The main object of the present invention is to provides a method for the preparation of a novel washcoat useful as a support for noble metal catalysts, which obviates the drawbacks as detailed above.
The main object of the present invention is to provide a method for the preparation of washcoated substrate which has thermal stability to withstand thermal stock.
Yet another object of the present invention is to provide a washcoat having high surface area.
Still another object of the present invention is to provide a washcoat which can be used a
suitable support for catalytically active component.

Accordingly the present invention provides a method for the preparation of a Light
- washcoat useful as a support for noble metal catalysts which comprises,
(i) boiling Ac cordierite monolith in a dilated acid such as nitric acid, drying and calcinated at a
temperature in die range of 300°C - 600°C for a time period of abant-2 hr,(ii) copping the above
said treated monolith in a solution of ahiminium salt at a temperature in the range of 60°C -
80°C for a time period of 1 min -10 mm to form a green coating,(iii) heat treating the green coated
monolith to obtain the first washcoatmenolith( iv)contacting the above said first wash coated monolith

with a slurry of aluminium oxide yielding species such as herien described
(v) with drawing the above monolith from

me slurry and heat treating to form a highly stable second waschoat
In an embodiment of the present invention the aluminium salt used is selected from the group consisting of nitrate, carbonate, acetate and sulphate most preferably nitrate.
In yet another embodiment of the present invention the rare earth oxides used are ceria and
lanthana
In yet another embodiment of the present invention the aluminium oxide yielding species is selected from bayerite, boehmite and aluminium isoproponide most preferably boehmite.
In yet another embodiment of the present invention the aluminium oxide yielding species such as boehmite is also used as a binder and a theological modifier.

In yet another embodiment of the present invention the rare earth oxides load gamma alumina used contains 5 wt%-12 wt% of ceria, 0.5 wt%-2.0 wt% of lanthana and the balance substantially gamma alumina.
In still another embodiment of the present invention the washcoat prepared is useful as a support for noble metal catalyst precursors such as platinum & rhodium to yield a highly active catalyst for the conversion of carbon monooxide, hydrocarbons and nitrogen oxides.
As indicated above this invention relates to a method for the preparation of a washcoated substrate of high surface area. The washcoat after cyclic exposures to high temperature environment adheres strongly with the substrate. The noble metal catalytic components on the washcoated substrate has a high performance to convert pollutants carbon monoxide, hydrocarbons and nitrogen oxides in the exhaust gas of gasoline vehicles simultaneoulsy to harmless carbon dioxide, water vapour and nitrogen. The washcoated substrate comprises of two distinct coats. A first washcoat and a second washcoat.
The first washcoat of the present invention can be formed by a technique in which a concentrated aqueous solution of an aluminium salt is applied to an acid treated substrate followed by firing of the green coated substrate to convert the aluminium salt into aluminium oxide. The aluminium salt can be nitrate, carbonate, acetate, sulphate. The most performed one is the nitrate.
According to the present invention the aluminium salt is aluminium nitrate which can yield aluminium oxide on heat treatment. A hot aqueous solution of aluminium nitrate is first prepared.

The acid treated substrate is dip coated in the hot concentrated solution of aluminium nitrate. The substrate is removed from the hot solution after 2 to 5 nits drained of the solution and recoated in the solution in the reverse direction. The substrate is finally withdrawn from the solution, drained and striped of the excess solution by blowing hot compressed air over its surface. The green coated substrate is heat treated to remove the solution medium and to decompose the aluminium nitrate. In general heat treating conditions are 100-150°C for 10 to 15 hrs followed by firing at 400 to 450°C for 4 to 10 hours.
The green coating according to the present invention is meant the coating prior to heat treatment. Acid treatment of the substrate according to the present invention means the boiling of the substrate in dilute mineral acids for sufficient time followed by heat treatment. Any mineral acid can be used but nitric acid is the preferred one. The substrate can be boiled in dilute nitric acid for 20 to 90 minutes. Generally it is 30 minutes, after which it is heat treated at 350 to 450°C for 2 to 4 hours. The acid treatment dissolves a pan: of alumina and magnesia of the cordierite substrate which helps in the development of pores of radius less than 1000 A. These additional pores help in the subsequent washcoating.
The substrate of the present invention can be of any type than can hold the washcoat. It is desirably made of any material that can withstand high temperatures. Some preferred materials are those which have a predominant phase of ceramics, glass ceramics, metal, alumina. The substrate material especially suited for the present invention is cordierite. The substrate can be of any size and shape. The size and shape is generally governed by the engine size and the space

available for mounting. Monolith substrates having fine parallel gas flow channels extending from the inlet to outlet are generally preferred. The wall of the channels are washcoated. The washcoat, holds the catalytic material. The gases come in contact with the catalytic material during its passage through the monolith. The channels of the monolith substrate can be any cross sectional shape and size such as trapezoidal, rectangular, square, hexagonal, circular. Such structures may contain 80 to 500 or more channels per square inch of the cross section. The monolith of the present invention contains 400 squarecells per square inch of the cross sectional area.
The second washcoat of the present invention is applied over the first washcoated substrate. The washcoat can be formed by a technique in which slurry is made of an alumina yielding species, rare earth oxide loaded alumina, an effective amount of rheological modifiers, binders, surface area stabilizers and a medium. The slurry is applied directly to the first washcoated substrate followed by heat treatment to convert the washcoat material to oxides.
According to the present invention the aluminium oxide yielding species is alumina or an alumina precursor which can yield aluminium oxide on heat treatment. The aluminium oxide yielding species can be aluminium hydroxides such as bayerite, aluminium hydroxylated oxides such as boehmite aluminium alkoxide such as aluminium isopropoxide or a combination thereof. Some typical aluminium oxides are gamma, delta, theta, alpha, kappa alumina. Preferred aluminium oxide yielding species are gamma alumina, boehmite, aluminium alkoxide or combination thereof.

The alumina utilized in the invention can be gamma, delta, theta or alpha alumina. The most preferred one is gamma alumina. The rare earths used to load the alumina are cerium and lanthanum.
The slurry may contain other components which render the slurry suitable for application to a substrate. Such components can be rheological modifiers, binders, surface area stabilizers.
Rheological modifiers are compounds which when present in the slurry modify the rheological properties of the slurry to make it suitable for application on the substrate uniformly. It also prevents unsatisfactory coating properties like flaking, chipping and cracking which would subsequently reduce the performance of the catalyst. Rheological modifiers can be rare earth oxides, stearic acid, oxalic acid etc. Boehmite can also function as a rheological modifier and the present invention utilizes boehmite as a rheological modifier.
The binders when present in the slurry promote adhension of the washcoat material with the first washcoated substrate. Alumina sols, collidal alumina are examples of binders. The present invention utilizes boehmite as a binder. The binding capacity of boehmite is activated by lowering the pH of the slurry to well below 6. This also helps in lowering the slurry viscosity. The slurry viscosity can be lowered by addition of any mineral acid preferably nitric acid. The lowering of the slurry viscosity also helps in coating the first washcoated substrate with ease.

The slurry media can be any media aqueous or non-aqueous in which the slurry components can be easily dispersed the most preferred medium is water. The present invention uses water as a dispersing medium for the slurry components.
The second washcoat of the present invention is prepared by first forming a slurry consisting essentially of the aluminium oxide yielding species and aluminium oxide. The aluminium oxide yielding species of the present invention is boehrnite. The boehmite acts as a Theological modifier, a binder and yields aluminium oxide on heat treatment. The aluminium oxide of the present invention is essentially gamma alumina. Prior to forming the slurry the aluminium oxide is impregnated with rare earth compounds and heat treated to convert them into oxides. The rare earth compounds utilized in the present invention are cerium nitrate and lanthanum nitrate. The aluminium oxide will typically contain in wt% of about 5 to 15 ceria and 0.5 to 2 of lanthana and the balance substantially gamma alumina.
The slurry of the present invention is formed by adding together sufficient amounts of aluminium oxide yielding species, cerium and lanthanum oxide loaded aluminium oxide and slurry medium to have the desired levels of the washcoat. The amount of slurry medium water is sufficient to disperse the components evenly and to leave a desired level of washcoat material after heat treatment. Sufficient dilute nitric acide is added to the slurry components to reduce the pH of the slurry well below 6 preferably between 3.6 to 3.7. The mixture of the slurry components is ball milled for a sufficient time to reduce particle size and to yield a slurry in which the slurry components are well dispersed and the viscosity of the slurry is adequate to washcoat the first washcoated substrate with ease. Generally the viscosity is between 15 to 30 centipose.

The first washcoated substrate is dip coated in the slurry by dipping it in the slurry for sufficient time generally between 2 to 5 minutes, with drawing from the slurry draining the slurry and dipping in the reverse direction. After 2 to 5 minutes the substrate is withdrawn from the slurry, drained, blown with compressed air to strip it of the excess slurry and dried. The coating and drying process is repeated until the desired amount of slurry components are applied on the substrate. The green coated substrate is then heat treated at a sufficient temperature for a sufficient time. The heat treating conditions are about 100 to 150°C for 10 to 20 hours followed by 500 to 850°C for 4 to 8 hours. The heat treatment removes the slurry medium, forms alumina from the alumina yielding species and binds the paniculate of the washcoat to the first over the substrate and to each other.
Application of a washcoat on the substrate as described in the present invention affords a high surface area generally between 100m2/gm to 200m2/gm as measured by N2 BET method. The high surface area is fairly well maintained even on heating at temperatures up to 800°C. The high surface area helps is obtaining high dispersion of the catalytic material. The washcoat as applied by the method described in the invention adheres strongly with the substrate and is not removed from the substrate even after subjecting it to thermal cycles.
The washcoat of the present invention also functions as an excellent support for catalytically active component and the catalyst has a high efficiency to convert carbon monoxide, hydrocarbons and nitrogen oxides present in petrol vehicle exhaust to harmless components.

The catalyst of the present invention are noble metals. The noble metal components are platinum, palladium, rhodium, ruthenium or iridium particularly platinum, palladium and rhodium either alone or in combination. Generally the catalyst will be platinum - rhodium mixtures.
The noble metals are applied to the alumina support over the substrate by decomposing a noble metal compound which has been deposited on the support. Preferred compounds would be chloroplantinic rhodium chloride, rhodium nitrate, palladium chloride palladium nitrate.
The noble metals may be applied either separately or in combination. The present invention utilizes aqueous solution of platinum and rhodium salts in combination. The mixed solution is used to impregnate the support. The deposited metal precursors on the washcoat are decomposed by heat treatment to yield a highly dispersed catalytically active metal component on the washcoat. The catalyst contains 1.2 to 2.4 gms/lt of Ft and Rh in the ratio of 5to 1.
Impregnation of the washcoated monolith with noble metal affords more control on the amount of noble metals loaded on the washcoat, the metal are more efficiently utilized with very little loss of the precious noble metal.
The novelty of the present invention live in the preparation of second vvashcoating of slurry containing ceria and lanthana loaded gamma alumina and alumina yielding species over the first wash coat of alumina to give highly thermally stable washcoat to increase the activity of the catalyst in wide range of conditions.

The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example 1
A. Acid leaching of cordirite monolith
Two cordierite monoliths of diameter 92 mm length 125 mm each and having 400 cells per square inch (cpsi) were boiled in 4N nitric acid for 30 mts, dried and calcined at 500°C for 2 hours.
B. Preparation of first washcoating
2 Kg of Al(NOj)3 9H2O was mixed with deionized water and boiled to a volume of 1600 cc. The acid treated monoliths of example 1 were 1st washcoated by dipping in the solution of aluminium nitrate at 70 to 80°C for 2 to 5 mts, with drawing from the solution and stripping of the excess solution by blowing hot air over the surface. The green coated monoliths were dried overnight at 100UC followed by firing at 500°C for 2 hours.
C. Loading of Alumina with ceria and lanthana
1.5 Kg of gamma alumina was contacted with 1.5 litre solution of cerium and lanthanum nitrate containing 167 gms of CeO2 and 17.5 gins of La2O. The alumina was allowed to soak for 20 mts at room temperature, dried slowly upto 65°C for 2 hours followed by drying overnight at 110°C before firing in air at 500°c for 4 hours.

D. Preparation of slurry
126 gms of ceria and lanthanum loaded gamma alumina, 108 gms of boehmite 5.0 cc of concentrated nitric acid and 540 gms of deionized water enough to decrease the solid content in the slurry to about 30-32 percent by weight were placed in a ball mill and run for 60 ints. The resulting slurry had a pH of 3.8 and viscosity of 20 centipoise.
E. Preparation of second washcoating
For 2nd washcoating the 1st washcoated monoliths were dipped in the slurry prepared as above for 5 to 7mts with drawn from the slurry and dip coated in the reverse direction. After 5 to 7 mts monoliths were drained and the channels were cleared of the excess slurry by jetting air over the surface. The green coated monoliths were dried. The washcoating and drying was repealed till the desired amount of washcoat was obtained on the monolith. The washcoated monoliths were finally dried at 100°c for 15 hours followed by calcination at 80()°C for 4 hours.
Example 2 Application of washcoat as support for noble metal catalyst
For noble metal impregnation the washcoated monoliths of example 1 were dipped in a mixed aqueous solution of chloroplatinic acid and rhodium nitrate having Pt and Rh in a ratio of 5 to 1 and yielding about 1.8 gms/litre of metals on the washocated monolith. The impregnated monolith were dried overnight at 110°C prior to calcination in a flow of air at 550°C for 4 hours.
Example 3 Performance of washcoat material
Table 1 below shows the effect of ceria and lanthana addition on surface area preservation of the second washcoat material after heat treating at 550°C and 800°C. The second washcoat material containing ceria and lanthana loaded gamma alumina and boehmite was prepared as given in example 4. The obtained slurry was dried at 100°C for 15 hours followed by calcination at 550°C and 800°C for durations as indicated in the table.
Another sample was prepared using similar procedure as given above with the difference that the gamma alumina contained in the sample was not loaded with ceria and lanthana. The N2 BET surface areas of the samples are given in table 1.
Table 1 N2 BET surface area m2/gm
Calcination Second vvashcoat material Second washocat material
Conditions containing ceria and lanthana without ceria and lanthana
550°C for 4 hours 192 235
800°C for 4 hours 120 130
800°C for 8 hours 107 120
800"C For 16 hours 106 100
The results indicate that more surface area is retained in the sample containing ceria and lanthana than for alumina not containing ceria and lanthana.

Test 1
Washcoated monolith prepared according to the present invention was subjected to a thermal cycling test for testing the adherence of the washcoat with the monolith. The sample was subjected to three thermal cycles of 60 mts. each (30 mts. heating to about 700°C and 30 mts. cooling to about 100°C ). The results are given below :
1 Weight of washcoated monolith 369 gms
before thermal cycling test
2 Weight of washcoated monolith 369 gms
after thermal cycling test
3 Loss of washcoat in thermal cycling nil
Test 2
The catalyst prepared according to the present invention was tested for its efficiency to convert carbon monoxide, hydrocarbons and nitrogen oxides contained in the exhaust gas of petrol driven vehicle, The catalyst was suitably canned and fitted to the exhaust pipe of a 1500 cc, closed loop fuel injected commercial passenger car. The catalyst fitted car was mounted on a chasis dynamometer and run as per Indian Gasoline vehicle emission test

procedure. The exhaust gas was collected and analysed for carbon monoxide, hydrocarbons and nitrogen oxides by Constant Volume Sampler (CVS) system and diluted exhaust gas analyser as per approved procedure. The mass emissions of carbon monoxide, hydrocarbons and nitrogen oxides were measured and converted to gms/km to calculate the conversion efficiency of the catalyst for CO, HC and NOX. The test was repeated on the vehicle without the catalyst. The results of mass emission are given below:
Mass emission results
CO HC NOX
gms/Km gms/Km gms/Km
Without catalyst 8.04 0.85 1.21
With catalyst 1.62 0.12 0.09
Conversion0/. 79.8 85.9 92.6
The above results show that the washcoat made according to the present invention functions as an excellent support for holding the catalytically active noble metal component. The catalyst prepared has a very high efficiency to convert CO, HC and NOX present in exhaust gas of petrol driven vehicle.
It should be however understood that the present invention has been described in detail with respect to the specific embodiments thereof several variations can be made to the

embodiment without departing from the spirit of the invention and the scope of the appended claims.
The main advantages of the present invention are that the washcoat when applied on a ceramic monolith substrate by the method of the present invention is highly stable, has strong adherence with the substrate and also functions as an excellent support for noble
metal catalysts.
The noble metal catalyst prepared on the washcoated monolith has a very high activity for conversion of pollutants in petrol vehicle exhaust gas to inoxious components.

We claim :
1. A method for the preparation of a highly stable washcoat useful as a support for
noble metal catalysts which comprises:
i) boiling the codierite monolith in a diluted acid such as nitric acid, drying and
calcinating at a temperature in the range of 300°C-600°C for a time period of 2 hours,
ii) dipping the above said treated monolith in a solution of aluminium salt such as herein described at a temperature in the range of 60°C-80°C for a time period of 1-10 min to form a green coating on the said monolith,
iii) heat treating the green coated monolith to obtain the first washcoat monolith,
iv) contacting the above said first wash coated monolith with a slurry of aluminium oxide yielding species such as herein described, rare earth oxide loaded gamma alumina and nitric acid in an aqueous medium,
v) withdrawing the above monolith from the slurry and heat treating to form a highly stable second waschoat.
2. A method as claimed in claim 1 wherein the aluminium salt used is selected from
the group consisting of nitrate, carbonate, acetate and sulphate most preferably
nitrate.

3. A method as claimed in claims 1-2 wherein the rare earth oxides used are ceria
and lanthana.
4. A method as claimed in claims 1-3 wherein aluminium oxide yielding species is
selected from the group consisting of bayerite, boehmite and aluminium
isoproponide most preferably boehmite.
5. A method as claimed in claims 1-4 wherein the rare earth oxides loaded gamma
alumina used is comprising 5 wt%-12 wt% of ceria, 0.5 wt%-2.0 wt% of
lanthana and the balance of gamma alumina.
6. A method as claimed in claims 1 -5 wherein the washcoat prepared is useful as a
support for noble metal catalyst precursors such as platinum and rhodium or a
mixture thereof to yield a highly active catalyst for the conversion of carbon
monoxide, hydrocarbons and nitrogen oxides.
7. A method for the preparation of a highly stable washcoat useful as a support for
noble metal catalysts substantially as herein described with reference to the
examples.

Documents:

390-del-2001-abstract.pdf

390-del-2001-claims.pdf

390-del-2001-correspondence-others.pdf

390-del-2001-correspondence-po.pdf

390-del-2001-description (complete).pdf

390-del-2001-form-1.pdf

390-del-2001-form-18.pdf

390-del-2001-form-2.pdf

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Patent Number

231569

Indian Patent Application Number

390/DEL/2001

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

06-Mar-2009

Date of Filing

29-Mar-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DAYAL SINGH RAWAT	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
2	VIJAY SINGH DANGWAL	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
3	RAGHUNATH PRASAD MEHROTRA	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
4	LAXMI NARAIN	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
5	AMAR KUMAR JAIN	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
6	BUDH PRAKASH PUNDIR	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
7	MANOJ KUMAR	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
8	ANAND SINGH	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
9	PREM PAL	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
10	LAKSHMI DATT SHARMA	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
11	RAJESH KUMAR	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
12	MANOJ KUMAR RUNDA	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
13	VIRENDRA KUMAR KAPOOR	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
14	KANCHAN KUMAR GANDHI	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
15	TURUGA SUNDRA RAMA PRASADA RAO	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.

PCT International Classification Number

B01J 21/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA