WO2019171401A1

WO2019171401A1 - A catalyst substrate

Info

Publication number: WO2019171401A1
Application number: PCT/IN2019/050194
Authority: WO
Inventors: Alok TRIGUNAYAT; Jaipal SINGH; Ritesh Mathur; Amit GULVANI; Rajan Bosco; Sushil MISHRA; Sumit KUKRETI
Original assignee: Ecocat India Pvt. Ltd.
Priority date: 2018-03-09
Filing date: 2019-03-08
Publication date: 2019-09-12

Abstract

A catalyst substrate (100) that includes a first foil layer (102) and a second foil layer (104). At least one of the first foil layer and the second foil layer is structured with a pattern (106) of deformations, and at least one of the first foil layer and the second foil layer includes micro-corrugations (108) protruding in perpendicular direction to its surface. The first foil layer and the second foil layer are wound together to create a three dimensional honeycomb structure (110) having passages (112) extending through the length of the honeycomb structure to allow flow of a gas (113) through the honeycomb structure in a longitudinal direction, and the first foil layer and the second foil layer have a plurality of apertures (114) to allow mixing of the gas flowing through the passages in the honeycomb structure.

Description

A CATALYST SUBSTRATE

FIELD OF INVENTION

The present invention relates to a catalyst substrate. More particularly, the present invention relates to a catalyst substrate that has complex flow paths to increase conversion rates.

BACKGROUND OF THE INVENTION

Many conventional catalyst substrates are made of two thin layers of metallic foil, one flat and one corrugated, which are wound together in spiral form to create a honeycomb structure which is placed inside a metal shell. Major drawback in conventional catalyst substrate is that after 15-20 mm axial distance, flow becomes laminar in laminar flow the catalytic process is diffusion governed and that the diffusion process is very slow, which leads to lower mass transfer and conversion rates also in conventional catalyst most of the gases passes through passages without interacting with coated surface because of fluid boundary layer formation.

In uses cases such as exhaust after treatment systems, the performance of a catalyst in a catalyst substrate depends greatly on the diverse chemical reactions between the exhaust gasses and the catalyst coated substrate surface. Mass transfer rate, heat transfer coefficient and heat capacity are few of the major factors which govern the conversion rate of exhaust gasses. For example, mass transfer refers to transportation of the gaseous emission from the gas phase core to catalytically active walls of passages in catalyst. The heat transfer coefficient and heat capacity affects a change in gas and structure temperature differences which leads to heating-up of catalyst. A study of the prior-art in this field of exhaust after treatment systems reveals instances of catalyst substrates with a honeycomb structure with parallel passages from entry surface to exit surface. In these instances, the flow of gasses is mainly laminar and reactions are mainly governed by diffusion process, thereby having a mass transfer rate, heat transfer coefficient and heat capacity which results in sub-optimal performance of the catalyst.

Therefore, there is need of substrate with high mass transfer rate, high heat transfer rate and low heat capacity to get max benefit of available space and precise material in catalyst substrate.

OBJECTIVES OF THE INVENTION

A main objective of this invention is to provide a catalyst substrate that disturbs the laminar flow of gas passing through its passages, and results in improvements in mass & heat transfer and catalyst performance. Another objective of the invention is to provide a catalyst substrate that enhances mixing & equalization of flow of gas through the substrate by providing complex paths for gas flow using a combination of apertures and passages, which also results in improvements in mass & heat transfer and catalyst performance.

Another objective of the invention is to provide a light weight substrate, resulting from the formation of apertures in the foils. The reduced weight of the substrate lowers the thermal mass and heat capacity of the substrate and helps in improving cold start emission results.

Another objective of the invention is to optimized size, shape, pitches of micro-corrugation to improve the performance of the catalyst. Another objective of the invention is to enhanced turbulence in the catalyst substrate to break fluid boundary layer in the catalyst substrate.

Another objective of the invention is to provide for flow equalization in the catalyst substrate.

SUMMARY OF THE INVENTION The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

Aspects of the present invention relate to a catalyst substrate. The substrate includes a first foil layer and a second foil layer. At least one of the first foil layer and the second foil layer is structured with a pattern of deformations, and at least one of the first foil layer and the second foil layer includes micro-corrugations protruding in perpendicular direction to its surface. The first foil layer and the second foil layer are wound together to create a three dimensional honeycomb structure having passages extending through the length of the honeycomb structure to allow flow of a gas through the honeycomb structure in a longitudinal direction, and the first foil layer and the second foil layer have a plurality of apertures to allow mixing of the gas flowing through the passages in the honeycomb structure.

According to some aspects, at least one of the first foil layer and the second foil layer is made up of a metal or metal alloy. According to some aspects, the pattern of deformations includes at least one of a sinusoidal, a triangular, a trapezoidal, a square and a rectangular wave pattern. According to some aspects, the honeycomb structure is enclosed in a metallic shell. According to some aspects, the apertures are distributed throughout the honeycomb structure in all the three dimensions.

According to some aspects, the percentage of area of at least one of the first foil layer and the second foil layer covered by the apertures ranges between 10% and 80%. According to some aspects, the percentage of area of at least one of the first foil layer and the second foil layer covered by the apertures ranges between 15% and 40%. According to some aspects, the percentage of area of at least one of the first foil layer and the second foil layer covered by the apertures ranges between 20% and 30%.

According to some aspects, the apertures do not overlap in the honeycomb structure. According to some other aspects, at least two apertures overlap at least partially with each other in the honeycomb structure. According to some aspects, each aperture has at least one of a polygonal, circular, elliptical, oval, triangular, banana-like and racetrack-like shape. According to some aspects, each aperture has an area equal to or larger than the cross-sectional area of each of the passages extending through the length of the honeycomb structure. According to some aspects, the honeycomb structure is coated with a catalyst material.

According to some aspects, a plurality of vanes are located along the periphery of each aperture. According to some aspects, the vanes are oriented in at least one of a direction along the flow of gas and a direction perpendicular to the flow of gas. According to some aspects, apertures and passages form intricate radial and circumferential flow paths for the gas in the honeycomb structure.

According to some aspects, the micro-corrugations have a predefined pitch along the length and width of at least one of the first foil layer and the second foil layer. According to some aspects, the pitch of the micro-corrugations ranges between 10% and 300% of the height of the structured wave pattern. According to some aspects, the pitch of the micro-corrugations ranges between 50% and 250% of the height of the structured wave pattern. According to some aspects, the pitch of the micro-corrugations ranges between 100% and 200% of the height of the structured wave pattern. According to some aspects, the micro-corrugations extend towards at least one side of the at least one of the first foil layer and the second foil layer. According to some aspects, the height of the micro-corrugations ranges between 1 and 30 times the thickness of at least one of the first foil layer and the second foil layer. According to some aspects, the height of the micro-corrugations ranges between 2 and 10 times the thickness of at least one of the first foil layer and the second foil layer.

According to some aspects, each of the micro-corrugations has one of a hemispherical, semi-ellipsoidal, tetrahedral and pyramidal shape. According to some aspects, flat surfaces extend between adjacent micro-corrugations. According to some aspects, the area of flat surfaces between said micro corrugations, is such that the area of flat surfaces includes between 5% and 40% of the total area of the at least one of the first foil layer and the second foil layer. According to some aspects, the area of flat surfaces between said micro- corrugations, is such that the area of flat surfaces includes between 20% and 30% of the total area of the at least one of the first foil layer and the second foil layer. According to some aspects, the micro-corrugations increase the surface area of the at least one of the first foil layer and the second foil layer by 2 to 15%. According to some aspects, micro-corrugations increase the surface area of the at least one of the first foil layer and the second foil layer by 3 to 10%.

Aspects of the present invention also relate to a method making said catalyst substrate, wherein the method includes providing a first sheet of a metal or a metal alloy having a flat surface, providing a second sheet of a metal or a metal alloy having the pattern of deformations, processing at least one of the first sheet and the second sheet to form the micro-corrugations, processing at least one of the first sheet and the second sheet to form the apertures, and placing the first sheet adjacent to the second sheet and winding the sheets together to form the honeycomb structure. According to some aspects, the method includes coating at least one of the first sheet and the second sheet with a catalyst. According to some aspects, the processing of at least one of the first sheet and the second sheet to form the micro-corrugations includes stamping at least one of the first sheet and the second sheet with a roller stamp. According to some aspects, the processing of at least one of the first sheet and the second sheet to form the apertures includes die cutting at least one of the first sheet and the second sheet. Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

Some of the objects of the invention have been set forth above. These and other objects, features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where:

Figures 1A and 1B depict a catalyst substrate, where Figure 1A is a schematic depicting an exploded view of the catalyst substrate, and Figure 1B is a schematic perspective view of the catalyst substrate.

Figures 2A-2C depict various embodiments of pattern of deformations, wherein Figure 2A depicts a sinusoidal pattern, Figure 2B depicts a triangular pattern, and Figure 2C depicts a rectangular pattern.

Figures 3A-3C depict various embodiments of the micro-corrugations. Figure 3A depicts a pattern of micro-corrugations, Figure 3B depicts the micro corrugations on various surfaces of the foils, and Figure 3C depicts various shapes for the micro-corrugations.

Figures 4A-4C depict various embodiments of apertures. Figure 4A depicts various possible shapes of the apertures, Figure 4B depicts a schematic of a section of the honeycomb structure to depict the three-dimensional arrangement of the apertures, and Figure 4C depicts a section of a foil having apertures with vanes.

Figure 5 is a flow-chart depicting a method of manufacturing the catalyst substrate. DETAILED DESCRIPTION

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized.

Overview

The present invention has been developed with an objective of providing a catalyst substrate with improved flow characteristic with respect to heat and mass transfer and flow mixing between passages of the catalyst substrate. Accordingly, the catalyst substrate of the present invention can be used in an exemplary use case of enhancing the efficiency of an exhaust gas after treatment system for purifying exhaust gas discharged from an engine.

The catalyst substrate of the present invention has been developed to continually break smooth fluid boundary layer flow of gases through the passages of the catalyst substrate and create turbulence with optimum back pressure. The catalyst substrate of the present invention is made of two thin layers of foil, one flat and one corrugated, which are wound together in spiral form to create a honeycomb structure.

The catalyst substrate contains optimized array of micro-corrugation on one or both layers of foil to disturb the laminar flow and create turbulence which improves the mass and heat transfer and catalyst performance. In the proximity of the micro-corrugations the flow is diverted and velocity of gas increases. The resulting turbulence causes mixing of gas layer near the wall & improves heat transfer. In some embodiments, the micro-corrugation is done in the transverse direction of flow of gasses through the catalyst substrate. In some embodiments, the micro-corrugated array on the catalyst substrates can have a density ranging between 50 and 1500 cpsi (cells per square inch), a micro corrugation height that can vary between 1 micron and 500 microns, and the pitch of the microcorrugation can vary from 10 microns to 600 microns. In some embodiments, the micro-corrugation will be on both side of flat and corrugated/patterned sheet so that 100 % channels can be covered.

Another embodiment of the invention also includes a catalyst substrate having apertures in the foils, which creates complex pathways for flow of gasses within the catalyst substrate enhancing the mixing and flow equalisation inside catalyst substrate. Apertures also results in lower thermal mass and heat capacity of the substrate. Both these factor further leads to faster heating-up of catalyst and improvement in cold start emission performance of catalyst. In some embodiments, the foils can have elliptical apertures patterns optimized for maximum cross and equalize flow of gasses from the catalyst substrate. These foils with apertures are wound together in spiral form to create a honeycomb structure. Also, micro-corrugation is done on the foils in the transverse direction of flow of gasses. In some embodiments, the apertures can be circular in shape having a diameter ranging between 2 mm to 12 mm. In some other embodiments, the apertures can be elliptical in shape with a major diameter ranging between 3 mm to 12mm and a minor diameter ranging between 2 mm to 10 mm with axial pattern and a pitch ranging between 5 mm to 20 mm.

Another embodiment of the invention further includes vanes provided on the periphery of the apertures to enhance the cross flow in the complex pathways formed within the catalyst substrate. The vanes deflect the flow of gasses and enhance mixing. The cross flow caused by vanes also leads to increases in turbulence level and heat transfer coefficient between gas and catalyst surface.

Further, there are many benefits of combining the above mentioned features, for example, mass transfer in the catalyst substrate is no longer governed by diffusion process and the convection current due to mixing of flow in the pathways greatly improves the mass transfer coefficient. Combined effect of micro corrugations, apertures, and vanes greatly improves conversion efficiency of catalyst.

The catalyst substrate according to various embodiments of the present invention is described below with reference to the drawings:

Description

Figures 1A and 1B depict a catalyst substrate 100, where Figure 1A is a schematic depicting an exploded view of the catalyst substrate 100, and Figure IB is a schematic perspective view of the catalyst substrate 100. The catalyst substrate 100 includes a first foil layer 102 and a second foil layer 104. At least one of the first foil layer 102 and the second foil layer 104 is structured with a pattern 106 of deformations. At least one of the first foil layer 102 and the second foil layer 104 includes micro-corrugations 108 protruding in perpendicular direction to its surface. The first foil layer 102 and the second foil layer 104 are wound together to create a three dimensional honeycomb structure 110 having passages 112 extending through the length of the honeycomb structure to allow flow of a gas 113 through the honeycomb structure in a longitudinal direction. The first foil layer 102 and the second foil layer 104 have a plurality of apertures 114 to allow mixing of the gas flowing through the passages 112 in the honeycomb structure 110. In some embodiments, a metallic shell 1 16 encloses the honeycomb structure 110.

In some embodiments, the honeycomb structure 110 is chemically coated where chemical coating comprises of support/carrier materials, zeolites/ zeolite- type materials, oxygen storage materials and catalytically active metals. The support/carrier material includes, but not limited to oxides and/or sulfates and/or nitrates and/or hydroxides of Ammonia, Aluminum, Silicon, Titanium, Vanadium, Tungsten, Zirconium, Molybdenum, Hafnium, Barium, Strontium, Cesium, Lanthanum, Yttrium, Magnesium and combinations thereof. The zeolites/zeolite- type materials include those belonging to Chabazite, MFI, Beta & Faujasite families and combinations thereof. The oxygen storage materials include to oxides and/or sulfates and/or nitrates and/or hydroxides of Cerium, Zirconium, Hafnium, Lanthanum, Neodymium, Praseodymium, Ytterbium and other Rare Earth Metals and combinations thereof. The catalytically active metals include compounds or complexes of Platinum, Palladium, Rhodium, Ruthenium, Silver, Gold, Indium, Iron, Osmium, Iridium, Magnesium, Manganese, Copper, Cobalt and in their combinations thereof, preferably Platinum, Palladium, Rhodium and in their combinations thereof,

In some embodiments, the first foil layer 102 and the second foil layer 104, each have a length ranging between 10 and 1800 cm; a width ranging between 2 cm and 50 cm; and a thickness ranging between 0.01 and 0.5 mm.

In some embodiments, the metallic shell 1 16 has a length ranging between 2 cm and 52 cm; a diameter ranging between 1.5 cm and 400 cm; and a thickness ranging between 0.5 mm and 4 mm. ln some embodiments, the pattern 106 has a height from the surface ranging between 0.5 m and 10 mm, and a width ranging between 1 and 8 mm.

In some embodiments, the first foil layer 102 and the second foil layer 104 is mainly made up of ferritic stainless steel alloy Aluchrom YHf (W1 .4767), Aluchrom 418 YHf. Other alloy that can be used for foil is Iron-Chromium- Aluminium Alloy FeCrAl 125, FeCrAl 135, FeCrAl 135.

In some embodiments, the shell 116 made up of stainless steel grade AISI 409, AISI 436, AISI 441.

In some embodiments, the pattern 106 of deformations includes at least one of a sinusoidal, a triangular, a trapezoidal, a square and a rectangular wave pattern. For example, figures 2A-2C depict various embodiments of pattern of deformations, wherein Figure 2A depicts a sinusoidal pattern, Figure 2B depicts a triangular pattern, and Figure 2C depicts a rectangular pattern. Figures 3A-3C depict various embodiments of the micro-corrugations. Figure 3A depicts a pattern of micro-corrugations, Figure 3B depicts the microcorrugations on various surfaces of the foils, and Figure 3C depicts various shapes for the micro-corrugations.

In some embodiments, as shown in Figures 3A-3C, the micro-corrugations 108 have a predefined pitch along the length and width of at least one of the first foil layer 102 and the second foil layer 104. In some embodiments, the pitch of the micro-corrugations 108 ranges between 10% and 300% of the height of the structured wave pattern 106. In some embodiments, the pitch of the micro corrugations 108 ranges between 50% and 250% of the height of the structured wave pattern 106. In some embodiments, the pitch of the micro-corrugations 108 ranges between 100% and 200% of the height of the structured wave pattern 106. In some embodiments, the micro-corrugations 108 extend towards at least one side of the at least one of the first foil layer 102 and the second foil layer 104. In some embodiments, the height of the micro-corrugations 108 ranges between 1 and 30 times the thickness of at least one of the first foil layer 102 and the second foil layer 104. In some embodiments, the height of the micro-corrugations 108 ranges between 2 and 10 times the thickness of at least one of the first foil layer 102 and the second foil layer 104.

In some embodiments, as shown in Figures 3A-3C, flat surfaces 109 extend between adjacent micro-corrugations 108. In some embodiments, the area of flat surfaces 109 between said micro-corrugations 108, is such that the area of flat surfaces 109 includes between 5% and 40% of the total area of the at least one of the first foil layer 102 and the second foil layer 104. In some embodiments, the area of flat surfaces 109 between said micro-corrugations 108, is such that the area of flat surfaces 109 includes between 20% and 30% of the total area of the at least one of the first foil layer 102 and the second foil layer 104. In some embodiments, the micro-corrugations 108 increase the surface area of the at least one of the first foil layer 102 and the second foil layer 104 by 2 to 15%, In some embodiments, the micro-corrugations 108 increase the surface area of the at least one of the first foil layer 102 and the second foil layer 104 by 3 to 10%.

In some embodiments, as shown in Figure 3C, each of the microcorrugations 108 has one of a hemispherical, semi-ellipsoidal, tetrahedral and pyramidal shape.

In some embodiments, the micro-corrugation on at least one of the first foil layer 102 and the second foil layer 104 has a density ranging between 100 cpsi (cells per square inch) to 1200 cpsi. In some embodiments, each microcorrugation has a height ranging between 5 microns and 500 microns, and a pitch ranging between 10 microns and 600 microns.

Figures 4A-4C depict various embodiments of apertures 114. Figure 4A depicts various possible shapes of the apertures 114, Figure 4B depicts a schematic of a section of the honeycomb structure 110 to depict the three- dimensional arrangement of the apertures 114, and Figure 4C depicts a section of a foil having apertures 114 with vanes 1 15.

In some embodiments, as shown in Figure 4A, each aperture 114 has at least one of a polygonal, circular, elliptical, oval, triangular, banana-like and racetrack like shape. In some embodiments, the apertures 1 14 are distributed throughout the honeycomb structure 110 in all the three dimensions to create complex pathways within the honeycomb structure 110. In some embodiments, the percentage of area of at least one of the first foil layer 102 and the second foil layer 104 covered by the apertures 1 14 ranges between 10% and 80%. In some embodiments, the percentage of area of at least one of the first foil layer 102 and the second foil layer 104 covered by the apertures 114 ranges between 15% and 40%. in some embodiments, the percentage of area of at least one of the first foil layer 102 and the second foil layer 104 covered by the apertures 114 ranges between 20% and 30%. In some embodiments, as shown in Figure 4B, each aperture 1 14 has an area equal to or larger than the cross-sectional area of each of the passages 1 12 extending through the length of the honeycomb structure 1 10. In some embodiments, the apertures 114 do not overlap in the honeycomb structure 110. In some other embodiments, at least two apertures 1 14 overlap at least partially with each other in the honeycomb structure 1 10. In some embodiments, the apertures

114 and passages 112 form intricate radial and circumferential flow paths for the gas 113 in the honeycomb structure 1 10. In some embodiments, the apertures 1 14 can be circular in shape having a diameter ranging between 3 mm to 10 mm. In some other embodiments, the apertures 1 14 can be elliptical in shape with a major diameter ranging between 3 mm to 10mm and a minor diameter ranging between 2 mm to 7mm with axial pattern and a pitch ranging between 5 mm to 20 mm.

In some embodiments, as shown in Figure 4C, a plurality of vanes 1 15 are located along the periphery of each aperture 1 14. In some embodiments, the vanes

1 15 are oriented in at least one of a direction along the flow of gas 1 13 and a direction perpendicular to the flow of gas 1 13. The vanes 115 serve the purpose of further promoting cross flow. The vanes 115 aid in additional turbulence by creating swirls in the flowing exhaust gas when it moves along the complex paths formed by overlapping flow apertures 1 14 of several layers.

In some embodiments, each vane 1 15 is broader at the base where it is connected with the periphery of the aperture 1 14, and gets gradually narrower towards its apex. The vanes 1 15 can be of any shape. In some embodiments, the vanes 115 are triangular in shape, where the portion at the periphery of the flow aperture is the widest. In some embodiments, the vanes 115 are oriented such that the tips of alternate vanes 1 15 are displaced in a direction perpendicular to the surface containing the aperture by a distance of about 5 to 50% of the passage height. In some embodiments, the vanes 1 15 are oriented such that the exhaust gases flow along a path connecting the base of a vane 115 to its tip, a turbulent flow is created in the gases which are deflected due to the presence of micro-corrugations 108 and tip displacements. In some embodiments, the vanes 1 15 are oriented such that the exhaust gases are flowing in a direction perpendicular to the direction connecting the base of the vane 115 to its tip, a turbulent flow is created in the gases which are deflected due to presence of micro-corrugations 108 and tip displacements. The vanes 115 come in direct contact with the gases flowing through the center of the passage 112, further enhancing the conversion efficiency.

In some embodiments, the vanes 1 15 can be provided in either one or both apertures 1 14 in the foil layers 102 and 104. In some embodiments, the vanes 115 can be located on the sides of apertures 1 15 parallel to direction of flow of the gas 1 13 or on the side perpendicular to direction of flow of the gas 1 13 or on both the side of apertures 1 14. In some embodiments, the vanes 1 15 on apertures in flat and structured foil can be aligned in same or perpendicular direction. In some embodiments, the pitch and height of the vanes 1 15 can be varied and can be 1% to 25% of width of apertures 114. Different combinations of vane shapes, pitch, height and locations can be thought of to create a large number of variations of the honeycomb structure 110. In some embodiments, apertures 114 with the vanes 1 15 are patterned such that in the honeycomb structure 1 10, they overlap to form internal complex flow paths between the passages 1 12 with the vanes 1 15 deflecting the flow within these passages 1 12 to further enhance turbulence and flow mixing between channels.

Figure 5 is a flow-chart depicting a method of manufacturing the catalyst substrate. In some embodiments, a method making a catalyst substrate 100 includes a step 502 of providing a first sheet of a metal or a metal alloy having a flat surface and providing a second sheet of a metal or a metal alloy having the pattern of deformations (for example, a corrugated pattern), a step 504 of processing at least one of the first sheet and the second sheet to form the apertures 1 14, a step 506 of processing at least one of the first sheet and the second sheet to form the micro-corrugations 108, and a step 508 of placing the first sheet adjacent to the second sheet and winding the sheets together to form the honeycomb structure 110. In some embodiments, the method includes coating at least one of the first sheet and the second sheet with a catalyst. In some embodiments, the processing of at least one of the first sheet and the second sheet to form the micro- corrugations 108 includes stamping at least one of the first sheet and the second sheet with a roller stamp. In some embodiments, the processing of at least one of the first sheet and the second sheet to form the apertures 114 includes die cutting at least one of the first sheet and the second sheet. In some embodiments, the apertures 1 14 are die cut in a shape to form the vanes 115. Other methods of cutting such as laser cutting, water jets, etc. can also be used. In some embodiments, the catalyst substrate 100 is catalysed by chemically coating the sheets of metal with a catalyst material.

Various other modifications, adaptations, and alternative designs are of course possible in light of the above teachings. Therefore, it should be understood at this time that within the scope of the appended claims the invention might be practiced otherwise than as specifically described herein.

ADVANTAGES OF THE INVENTION

A main advantage of the present invention is that it provides a catalyst substrate that disturbs the laminar flow of gas passing through its passages, and results in improvements in mass & heat transfer and catalyst performance.

Another advantage of this invention is that it provides a catalyst substrate that enhances mixing & equalization of flow of gas through the substrate by providing complex paths for gas flow using a combination of apertures and passages, which also results in improvements in mass & heat transfer and catalyst performance.

Another advantage of this invention is that it provides a light weight substrate, resulting from the formation of apertures in the foils. The reduced weight of the substrate lowers the thermal mass and heat capacity of the substrate and helps in improving cold start emission results. Another advantage of this invention is that it optimizes size, shape, pitches of micro-corrugation to improve the performance of the catalyst.

Another advantage of this invention is that it enhances turbulence in the catalyst substrate to break fluid boundary layer in the catalyst substrate. Another advantage of this invention is that it provides for flow equalization in the catalyst substrate.

Claims

We Claim:

1. A catalyst substrate (100) comprising: a first foil layer (102); and a second foil layer (104); wherein at least one of the first foil layer and the second foil layer is structured with a pattern (106) of deformations, wherein at least one of the first foil layer and the second foil layer includes micro-corrugations (108) protruding in perpendicular direction to its surface, wherein the first foil layer and the second foil layer are wound together to create a three dimensional honeycomb structure (1 10) having passages (112) extending through the length of the honeycomb structure to allow flow of a gas (113) through the honeycomb structure in a longitudinal direction, and wherein the first foil layer and the second foil layer have a plurality of apertures (114) to allow mixing of the gas flowing through the passages in the honeycomb structure.

2. The catalyst substrate (100) as claimed in Claim 1, wherein at least one of the first foil layer (102) and the second foil layer (104) is made up of a metal or metal alloy.

3. The catalyst substrate (100) as claimed in Claim 1, wherein the pattern (106) of deformations includes at least one of a sinusoidal, a triangular, a trapezoidal, a square and a rectangular wave pattern.

4. The catalyst substrate (100) as claimed in Claim 1, wherein the honeycomb structure (110) is enclosed in a metallic shell (116).

5. The catalyst substrate (100) as claimed in Claim 1, wherein the apertures (114) are distributed throughout the honeycomb structure (110) in all the three dimensions.

6 The catalyst substrate (100) as claimed in Claim 1, wherein the percentage of area of at least one of the first foil layer (102) and the second foil layer (104) covered by the apertures (114) ranges between 10% and 80%.

7. The catalyst substrate (100) as claimed in Claim 1, wherein the percentage of area of at least one of the first foil layer (102) and the second foil layer (104) covered by the apertures (114) ranges between 15% and 40%.

8. The catalyst substrate (100) as claimed in Claim 1, wherein the percentage of area of at least one of the first foil layer (102) and the second foil layer (104) covered by the apertures (114) ranges between 20% and 30%.

9. The catalyst substrate (100) as claimed in Claim 1, wherein the apertures (114) do not overlap in the honeycomb structure (110).

10. The catalyst substrate (100) as claimed in Claim 1, wherein at least two apertures (114) overlap at least partially with each other in the honeycomb structure (110).

1 1. The catalyst substrate (100) as claimed in Claim 1 , wherein each aperture (114) has at least one of a polygonal, circular, elliptical, oval, triangular, banana-like and racetrack- like shape.

12. The catalyst substrate (100) as claimed in Claim 1 , wherein the honeycomb structure (1 10) is coated with a catalyst material.

13. The catalyst substrate (100) as claimed in Claim 1 , wherein each aperture (1 14) has an area equal to or larger than the cross-sectional area of each of the passages (112) extending through the length of the honeycomb structure (1 10).

14. The catalyst substrate (100) as claimed in Claim 1, wherein a plurality of vanes (115) are located along the periphery of each aperture (1 14).

15. The catalyst substrate (100) as claimed in Claim 14, wherein the vanes (1 15) are oriented in at least one of a direction along the flow of gas (113) and a direction perpendicular to the flow of gas (113).

16. The catalyst substrate (100) as claimed in Claim 1, wherein the apertures (1 14) and passages (112) form intricate radial and circumferential flow paths for the gas (113) in the honeycomb structure (1 10).

17. The catalyst substrate (100) as claimed in Claim 1, wherein the micro-corrugations (108) have a predefined pitch along the length and width of at least one of the first foil layer (102) and the second foil layer (104).

18. The catalyst substrate (100) as claimed in Claim 3, wherein the pitch of the micro-corrugations (108) ranges between 10% and 300% of the height of the structured wave pattern (106).

19. The catalyst substrate (100) as claimed in Claim 3, wherein the pitch of the micro-corrugations (108) ranges between 50% and 250% of the height of the structured wave pattern (106).

20. The catalyst substrate (100) as claimed in Claim 3, wherein the pitch of the micro-corrugations (108) ranges between 100% and 200% of the height of the structured wave pattern (106).

21. The catalyst substrate (100) as claimed in Claim 1 , wherein the micro-corrugations (108) extend towards at least one side of the at least one of the first foil layer (102) and the second foil layer (104).

22. The catalyst substrate (100) as claimed in Claim 1, wherein the height of the micro-corrugations (108) ranges between 1 and 30 times the thickness of at least one of the first foil layer (102) and the second foil layer (104).

23. The catalyst substrate (100) as claimed in Claim 1, wherein the height of the micro-corrugations (108) ranges between 2 and 10 times the thickness of at least one of the first foil layer (102) and the second foil layer (104).

24. The catalyst substrate (100) as claimed in Claim 1 , wherein each of the micro-corrugations (108) has one of a hemispherical, semi-ellipsoidal, tetrahedral and pyramidal shape.

25. The catalyst substrate (100) as claimed in Claim 1 , wherein flat surfaces (109) extend between adjacent micro-corrugations (108).

26. The catalyst substrate (100) as claimed in Claim 25, wherein the area of flat surfaces (109) between said micro-corrugations, is such that the area of flat surfaces (109) includes between 5% and 40% of the total area of the at least one of the first foil layer (102) and the second foil layer (104).

27. The catalyst substrate (100) as claimed in Claim 25, wherein the area of flat surfaces (109) between said micro-corrugations, is such that the area of flat surfaces (109) includes between 20% and 30% of the total area of the at least one of the first foil layer (102) and the second foil layer (104).

28. The catalyst substrate (100) as claimed in Claim 1, wherein the micro-corrugations (108) increase the surface area of the at least one of the first foil layer (102) and the second foil layer (104) by 2 to 15%.

29. The catalyst substrate (100) as claimed in Claim 1, wherein the micro-corrugations (108) increase the surface area of the at least one of the first foil layer (102) and the second foil layer (104) by 3 to 10%.

30. A method making a catalyst substrate (100) as claimed in Claim 1, wherein the method includes: providing a first sheet of a metal or a metal alloy having a flat surface; providing a second sheet of a metal or a metal alloy having the pattern of deformations; processing at least one of the first sheet and the second sheet to form the micro-corrugations (108); processing at least one of the first sheet and the second sheet to form the apertures (114); and placing the first sheet adjacent to the second sheet and winding the sheets together to form the honeycomb structure (1 10).

31. The method as claimed in claim 30, wherein the method includes coating at least one of the first sheet and the second sheet with a catalyst.

32. The method as claimed in claim 30, wherein the processing of at least one of the first sheet and the second sheet to form the micro-corrugations (108) includes stamping at least one of the first sheet and the second sheet with a roller stamp.

33. The method as claimed in claim 30, wherein the processing of at least one of the first sheet and the second sheet to form the apertures (114) includes die cutting at least one of the first sheet and the second sheet.