Title of Invention	"A CERAMIC SUBSTRATE FOR CATALYTIC CONVERTER AND METHOD OF MANUFACTURE OF THE SAME"
Abstract	This invention relates to a novel ceramic substrate for catalytic converter comprising the said ceramic substrate having tubular cross section with corrugated inner surfaces characterized in that the said tubular substrate is made with adjustable geometric surface area per unit volume as herein defined to achieve the required conversion efficiency.

Full Text

The invention relates to a ceramic substrate for catalytic converter and method of manufacture of the same. This ceramic substrate can be used as a catalytic converter in a motor vehicle or other equipment with combustion with combustion engine for the exhaust pollution control, after the ceramic substrate is suitably coated with catalysts or catalytic material. Presently ceramic or metallic honeycomb monoliths or metallic hot tubes are used for catalytic converter application. There are disadvantages associated with the present catalytic converters. One of the main disadvantages associated with the present system is that manufacture of a honeycomb monolith either from ceramic substrate or metallic is complicated and expensive. Other disadvantage with honeycomb substrate is that it offers back pressure hence reduction in engine power which is more significantly effects fuel economy as well as drivability and engine performance especially in smaller engines like motor cycles. Another disadvantage is that the present catalytic converters with ceramic or metallic honeycomb monoliths or metallic tubes are not stable for higher temperature use particularly very near to the engine manifold. As the pollution control norms are becoming more strict these ceramic or metallic monolithic substrates or metallic tube substrates are required to be fitted near the engine manifold in order to obtain good conversion efficiency during starting the engine known as cold start emission control. Therefore the main object of the present invention is to propose a novel ceramic monolithic substrate for catalytic converter which gives adequate conversion efficiency with low engine back pressure, robust design for extra-high vibration, cheaper cost and easy replacement. This novel concept is realized through a ceramic based tubular insertion and inside of corrugated shape. Another object of the present invention is to construct a high temperature stable ceramic monolithic substrate which overcome the difficulty of positioning the present ceramic or metallic honeycomb monoliths or metallic tubular substrates near the engine manifold. Another object of the present invention is to propose a catalytic converter, which has no objectionable engine back pressure. Yet another object of the present invention is to propose a catalytic converter which is robust in construction for use in extra-high vibration particularly to withstand very high vibration and mechanical impact while use in 2 and 3-4 wheelers, diesel engines and other automobilies running in rough road and engine used for stationary application. Still another object of the present invention is to propose a catalytic converter which is cheaper and easy to replace. A further object of the present invention is to propose a catalytic converter which is a tubular ceramic substrate design and can be used widely and economically for petrol or diesel driven automobile vehicles, stationary generators and other engines and appliances utilising internal combustion engines. -4- Yet another object of the present invention is to propose a catalytic converter comprising of the ceramic tubular substrates disclosed in this patent application, which can be positioned upstream near the engine manifold and the existing ceramic or metallic honeycomb substrates or metallic tubular substrates may be positioned downstream away from the engine manifold. By this type of composite construction of the catalytic converter proposed in this patent application, the cold start emission conversion efficiency of the catalytic converter an be improved substantially without risking the stability of the catalytic converter substrate fitted near the engine manifold. Therefore, a novel concept of catalytic converter is invented by optimum design of configuration and materials of substrates. According to the present invention there is provided a novel ceramic substrate for catalytic converter comprising the said ceramic substrate having tubular cross section with corrugated inner surfaces characterized in that the said corrugated inner surface of the said ceramic substrate have profiles selected from the types offering varying degree of surface area so that the geometric area is in the range of 0.1 to 0.6mm^ mm3 preferably 0.2 to 0.4mm2 to achieve the required conversion efficiency, the said ceramic substrate is made of required geometric surface area with diameter in the range of 5 to 200mm and having a controlled porosity of 10 to 60% and low thermal expansion below IxlO^/deg.C in the range of 30-1000 deg.C required geometric surface area with a diameter 5 to 100mm in order to fulfill the necessary exhaust gas conversion efficiency. According to the present invention there is provided a method manufacturing a ceramic substrate comprising the following step: a) Ceramic Raw Materials batch is intensely mixed in a batch mixer; b) -and mixed with suitable binders, plasticizers, lubricants etc. and water or ethanol or acetone or any other suitable medium in a shear mixer preferably closed gap sigma blade mixer for duration required to get good paste; c) the well-kneaded batch is then processed in a pug mill to obtain the de-aired blanks and d) the paste thus prepared by mixing with various binders and water or other medium to get good extrudability is put in hydraulic extruder or pug mill or other extrusion machine or presses for extrusion through a die; e) the extrusion die is fabricated to get the desired extrudate cross-section disclosed in this patent appli¬ cation. f) the extruded paste is cut to the required length and is dried; g) the dried product is then fired in a furnace at a temperature depending on the mechanical strength and porosity; h) the finished substrate is then wash coated followed by catalysts coating and then canned using steel pipe. The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with a non-limiting exemplary embodiments as shown in the accompanying drawings of the invention represented for use but not limited to in a 2,3 or 4 wheeler both 2-stroke and 4-stroke catalytic converter. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 - a typical cross-section of a substrate; Figure 2 - another typical cross-section of a substrate. Description of the product and method of making; In accordance with the present invention the ceramic substrates is having a tubular cross section with corrugated inner surfaces. The inner surfaces of the tubular product can have numerous types of profiles offering varying degree of surface area. The outer surface of the invented ceramic substrate can have suitable circular/ oval, rectangular, polygonal or any other surfaces with ribs or without ribs for better gripping with the canning material to make a very robust catalytic converter. The tubular substrate is designed such that geometric surface area per unit volume can be adjusted so that the required conversion efficiency is achieved. Design parameters such as inside and outside diameter, length and more importantly curvature and profile of inside surface is tailored so that Geometric Surface Area in the range of 0.1 to 0.6 mm /mm , 2 3 preferably 0.2 to 0.4 mm /mm is obtained. The diameter in the range of 5 to 200 mm, preferably 30 to 80 mm and length 10 mm to 300mm, preferably 30 mm to 200mm, more preferably 80 to 150mm length are designed to get total surface area in the range of 2 0.02 to 0.25m when used a single or multiple substrate/s for any given application. Material of the substrate is ceramic, more specifically but not restricted to cordierite which has controlled porosity 10 to 60%, preferably 20 to 45%, more preferably 30 to 40%, high temperature strength and low thermal expansion in the range of ( 30-1000 deg.C) below 1x10 /degC and thus gives high thermal shock resistance and can withstand a temperature of 1300 deg.C during use as catalytic converter. The pore volume is 0.05 to 0.50 CC/gm, preferably 0.15 to 0.25 cc/gm, so that wash coating and catalyst coating suitable for CO, HC and NOx conversion can be done very efficiently. It is also possible to produce a dense cordierite substrate having higher thermal expansion of more than 1x1~ /deg.C.Other ceramics like mullite, alumina and catalyst materials like zeolite, gamma-alumina, oxides of Titanium, Vanadium, Tungsten etc. are also can be fabricated in a tubular substrates, the thermal expansion of which are more than 1x10~ deg,C. Description of Manufacturing of the invented new ceramic substrate is given in the following example. A suitable ceramic batch composition is prepared and formed into paste by mixing with various binders and water to get good extrudability is put in extruder machine for extrusion through a specially designed die. The specially designed die has the outer pipe and a mandrel having configuration to obtain the desired cross-section as well as to have easy flow and the required compaction of the ceramic paste while extruding the product. The final exist cross section of the die is so designed to obtain the optimum profile and surface area of the novel ceramic substrates. Two typical non limiting cross section of the substrates are shown in Fig. 1 and Fig. 2 respectively. Maximizing the inner surface area without any abnormal restriction of exhaust gas flow is the key to design these novel ceramic substrates invented here for catalytic converter applications. Depending on the profile of the die parts, conventional machining; CNC machining, electro discharging, wire cutting etc. can be used to fabricate the die. The paste is extruded through this die and required length is cut and dried. The dried products are fired in a furnace till maturing temperature depending on the mechanical strength and porosity requirements. EXAMPLE A single phase cordierite material is obtained by mixing the cordierite forming batch containing 39% Indian Talc, a total of 46% of different types of Indian clays and 15% Alumina. above a) The a-bere batch is intensely mixed in a batch mixer; b) and mixed with 2% methyl cellulose, 0.5% of glycerin,5% wheat powder and 21% of water in a closed gap sigma blade mixer for 45 minutes; c) the well-kneaded batch is then procesed in a pug mill to obtain the de-aired blanks; d) the blank is then put in hydraulic extruder or pug mill for extrushion through a die; e) the extrusion die is fabricated to get the extrudate cross-section shown in Fig. 2. The die is designed similar as the known extrusion die has the outer pipe and a mandrel of suitable configuration to produce the above said cross-section; f) the extrudate is cut to required length and is dried; g) the dried product is then fired in a furnace at a temperature between 1380 to 1400 deg.C. h) the finished substrates is then wash coated followed by catalysts coating and then canned using steel pipe. The method of making the cordierite substate is such that 2 the product is having axial compressive strength 300 kg/Cm and does not decrease at high temperature upto 900 deg.C. Hence the product can be placed very near to the engine but have better high temperature resistance than metallic hot tube or metallic tubular substrates or thin walled metallic or ceramic honeycomb substrates. The properties of the novel ceramic substrate as described in the above example is given in Table 1 at page 11 as non-limiting typical characteristics. This substrate has the required porosity for wash coating and catalysts coating. The wash coated and catalyst coated substrate is canned using steel pipes appropriate for 2/3 wheelers. Coated catalytic converter is fitted to a 2-wheeler motor cycle for evaluation of conversion efficiency, back pressure and engine performance. The method of canning comprises using metal pipe with appropriate packing and insulation mateial so that the converter can be fitted to various automobile or equipment's exhaust pipe. After the suitable wash coating and catalyst coating the novel ceramic substrate is canned before fitting to the engine exhaust of an 4-stroke S.I. engined motor cycle. The novel ceamic substrate as described in this example have 34mm ID, 44mm OD and 100mm long. The results obtained after testing this novel ceramic substrate based catalytic converter fitted in 4-stroke motorcycle is presented in Table-2, 3 and 4 as shown in page 12. Table - 2 shows only a very marginal increase in back pressure and pressure drop acoss this novel converter when tested with the Motorcycle. The back pressure and the pressure drop obtained after employing this novel converter is very less when compared to equivalent conventional ceramic or metallic honeycomb based catalytic converter. Table - 3 presents the power loss data, which is nil when tested for the loss of Engine Power for the same 4-stroke, 2-wheeler vehicle fitted with this novel converter. Table 4 presents the mass emission results for the same 4-stroke Motor cycle with an objective to meet one targeted emission norms. The results shows that by using this novel converter CO level from 2.2 gm/km to 1.5 gm/km.hence it makes vehicle to meet the emission norms of EuroI/India 2000. The invention described herein above is in relation to a non-limiting embodiment and as defined by the accompanying claims. TABLE 1 - Properties of Novel Ceramic Substrate (Table Removed) Table 2: Exhaust Back Pressure Results of 4-stioke Motorcycle Under Wide Open Throttle Condition with and without the developed converter (Table Removed) Table 3: Engine Power Results of 4-stroke Motorcycle Under Wide Open Throttle Condition (Table Removed) Table 4: Mass Emission Results of 4-stroke Motorcycle under Indian Driving Cycle ( 4 Cycle Warm - up) WE CLAIM; 1. A novel ceramic substrate for catalytic converter comprising the said ceramic substrate having tubular cross section with corrugated inner surfaces characterized in that the said corrugated inner surface of the said ceramic substrate have profiles selected from the types offering varying degree of surface area so that the geometric area is in the range of 0.1 to 0.6mm2- mm3 preferably 0.2 to 0.4mma to achieve the required conversion efficiency, the said ceramic substrate is made of required geometric surface area with diameter in the range of 5 to 200mm and having a controlled porosity of 10 to 60% and low thermal expansion below 1x10- 6/deg.C in the range of 30-1000 deg.C required geometric surface area with a diameter 5 to 100mm in order to fulfill the necessary exhaust gas conversion efficiency. 2. A ceramic substrate for catalytic converter as claimed in claim 1 wherein the said tubular cross-section of the ceramic substrate is selected out of suitable circular, oval, rectangular and polygonal. 3. A ceramic substrate for catalytic converter as claimed in claims 1 through 2 wherein the said ceramic substrate is made of required geometric surface area with a diameter preferably 30 to 80mm and length 2 to 300mm, preferably 80 to 150mm length. 4. A ceramic substrate for catalytic converter as claimed in claim 1 wherein the said ceramic substrate is made of ceramic which is a cordierite having a controlled porosity preferably 20 to 45%, more preferably 30 to 40% and required geometric surface area with a diameter 5 to 100mm in order to fulfill the necessary exhaust gas conversion efficiency. 5. A ceramic substrate for catalytic converter as claimed in claims 1 through 4 wherein the said ceramic is made from cordierite- mullite, alumino-silicates, magnesium alumino-silicates, mullite, alumina and catalyst materials like zeolite, gamma-alumina, the thermal expansion of which are more than lxl0-6/deg.C. 6. A method of manufacturing of a ceramic substrate for catalytic converter as claimed in claims 1 through 5 comprising the following steps: a) Ceramic Raw Materials batch is intensely mixed in a batch mixer. b) and mixed with suitable binders, plasticizers, lubricants etc. and water or ethanol or acetone or any other suitable medium in a shear mixer preferably closed gap sigma blade mixer for duration required to get good paste; c) the well-kneaded batch is then processed in a pug mill to obtain the de-aired blacks and d) the paste thus prepared by mixing the various binders and water or other medium to get good extrudability is put in hydraulic extruder or pug mill or other extrusion machine or process for extrusion through a die; e) the extrusion die is fabricated to get the desired extrudate cross-section disclosed in this patent application f) the extruded paste is cut to the required length and is dried g) the dried product is then fired in a furnace at a temperature depending on the mechanical strength and porosity requirement; h) the finished substrate is then washed coated followed by catalysts coating and then canned using steel pipe. 7. A method of manufacturing of a ceramic substrate for catalytic converter as claimed in claim 8. 8. A ceramic substrate for catalytic converter as herein described and illustrated with the accompanying drawings.

Documents:

2585-del-1998-abstract.pdf

2585-del-1998-claims.pdf

2585-del-1998-correspondence-others.pdf

2585-del-1998-correspondence-po.pdf

2585-del-1998-description (complete).pdf

2585-del-1998-form-1.pdf

2585-del-1998-form-19.pdf

2585-del-1998-form-2.pdf

2585-del-1998-form-3.pdf

2585-del-1998-form-4.pdf

2585-del-1998-form-5.pdf

2585-del-1998-gpa.pdf