AU596966B2

AU596966B2 - Monolithic catalytic convertor mounting arrangement

Info

Publication number: AU596966B2
Application number: AU55610/86A
Authority: AU
Inventors: John D. Ten Eyck
Original assignee: Kennecott Corp
Current assignee: Unifrax 1 LLC
Priority date: 1985-04-16
Filing date: 1986-04-03
Publication date: 1990-05-24
Anticipated expiration: 2006-04-03
Also published as: CA1262438A; ES557421A0; JP2518819B2; KR860007953A; MX168257B; JPS61241413A; ZA862847B; KR930005290B1; AU5561086A; ES553981A0; ES8800395A1; ES8800740A1

Description

FORM 10 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PA7ENTS ACT 1952 596966^ COMPLETE SPECIFICATION A

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Class Int. Class Complete Specification Lodged: Accepted: Published: Prio~rity: Related Art: This docunient contanis the vn]ifldinerts made uiid., ,tion 49 arid is correct £oi printing.

Name of Applicant: Address of Appliuant: S. *S S KENNECOTT CORPORATION The Standard Oil Company Headquarters Building. 200 Public Square. Cleveland, Ohio 44114-2375. United States of America JOHN D4 TEN EYCK Spruson Ferguson, Patent Attorneys.

Level 33 St Martins Tower, 31 Market St' eet. Sydney.

New South Wales, 2000, Autstralia Actual Inventor: Address for Service: Complete Specification for the invention entitled: "MONOLITHIC CATALYTiC CONVERTOR MOUNTING ARRANGEMENT" The following statement is a full description pf this invention, including the best method of performing it known-to us SBR:eah 292T Israre

PATENT

84-P-1463 ABSTRACT OF THE DISCLOSURE 0 .me.

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A device suitable for use as a catalytic ccnverter for purification of the exhaust gases from an internal combustion engine at continuous operating temperatures in excess of 1600 0 F and up to 2500F includes a frangible ceramic monolith catalyst element resiliently mounted in a metallic housing. The monolith is wrapped in a thermally insulating layer of ceramic fibers capable of withstanding continuous exp.sure to temperatures of at least 2000 0 F. A layer of intumescent material disposed between the housing and the ceramic fiber layer resiliently secures the monolith in the housing. A method of manufacture of such a device is also described.

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PATENT

84-P-1463 The present invention relates to a device for treatment of exhaust gases from an internal combustion engine, e.g. a catalytic converter.

More specifically, the present invention relates to such devices which include as their catalytic member a frangible ceramic monolith including a plurality of flow channels on which catalyst material is deposited for eg interaction with said exhaust gases and to an improved mounting for such monolith.

.0 Background Of The Invention Such monoliths may be formed of a brittle fireproof ceramic material O such as aluminum oxide, silicon oxide, magnesium oxide, zircon silicate, cordierite or silicon carbide and the like. These ceramic materials provide a skeleton type of structure with a plurality of tiny flow channels. Small shockloads are sufficient to crack or crush the monolith. Due to this brittleness problem which exists when using this type of catalytic device in connection with motor vehicles in which the ceramic monolith Is located in a housing connected to the exhaust gas system, much effort has teen expended in developing means for support of the monolith in its housing so that the monolith would be substantially free of shockloads. Representative of these efforts are the following: a o U.S. patent 3,798,006 discloses securement of a monolithic type catalyst element in its housing by a differentially hardened fibrous lining. The monolith is supported by a felted layer or sleeve of ceramic fibers which are compressed between the monolith and a shelH, After assembly, a suitable rigidizer, binder and adhesive liquid containing a high temperature-resistant material such as aqueous colloidal silica is applied to the compressed layer of ceramic fiber material, The treated unit is thereafter dried in a manner so as to cause migration of the silica solids to the exposed ends of the sleeve of ceramic fiber.

-2- 84-P-1463 U.S. patent 3,876,384 discloses a monolithic catalyst carrier body which is resiliently mounted in a reactor casing by surrounding the monolith with a protective jacket which includes highly heat-resistant steel reinforcing means embedded in ceramic fiber and binder means, which itself includes a fireproof mortar. The monolith is enveloped by a protective jacket comprising an inner layer and outer layer of ceramic or mineral fibers which are embedded in a heat-resistant mortar. Steel reinforcing strips are e,.bedded between the ceramic fiber layers and grip both of the ceramic fiber layers.

1C U.S. patent 3,891,396 discloses an elastic holder for monolithic catalyst bodies. The holder consists of a metallic corrugated tube whic" simultaneously forms the outer wall of the exhaust conduit. This corrugated tube is provided with a mechanical bias which safely holds the monolithic catalyst body and presses it against an end bearing. The S monolithic body may be surrounded at its outer surface with elastic *i heat-reslstant material in the form of ceramic wadding disposed in the space between the corrugated tube and the catalyst body or its ceramic sleeve. The catalyst body may be cemented-with a heat-resistant cement to a ceramic sleeve which serves to thermally insulate the corrugated tube from hot exhaust gases.

U.S. patent 3,916,057 discloses a process for mounting monolithic catalyst support elements which utilizes an intumescent sheet material S containing vermiculite or other expandable mica. The intumescent sheet material functions as a resilient mounting material by expansion in situ. The thermal stability and resilience of vhe sheet after exfoliation compensate for the difference in thermal expansion of the metal canister and the monolith and absorbs mechanical vibrations transm'tted to the fragile monolith or forces which would otherwise be imposed on the monolith due to irregularities in the metallic or ceramic o surfaces.

U.S, patent 4,048,363 discloses an offset laminated intumescent mounting mat for use in wrapping a ceramic catalytic monolith. After -3r F H.

i i 84-P- 1463 heating, expansion of the intumescent material in the mat secures the monolith in its housing or covering.

U.S. patent 4,142,864 discloses mounting of a catalytic ceramic monolith by positioning a resilient, flexible ceramic fiber mat or blanket in the space between the catalytic monolith and the inner surface of the casing. This blanket is compressed upon installation of annular plug members which are inserted at each end of the ceramic monolith between it and the casing. The plugs may be formed of solid metal, wire mesh or hollow metal.

\o U.S. paterts 4,239,733 and 4,256,700 disclose a catalyst coated ceramic monolith supported in a sheet metal housing by both a wire mesh sleeve and an intumescent sleeve which are positioned adjacent each other In non-overlapping fashion.

U.S. patent 4,269,807 discloses a resilient mounting for a ceramic catalytic monolith in which the monolith is surrounded with a blanket of knitted wire mesh which is partially compressed throughout its length.

Overlying the knitted wire mesh is a band of high-temperature intumescent material containing ceramic fibers as a viscous caulking or'paste within S the matrix of the metal mesh. Among the constructions disclosed is one Q which includes machining the ceramic monolith to remove 1/8 inch from its

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0 diameter and coating it with ceramic fibers of the corresponding thickness followed by surrounding with a blanket of knitted wire mesh.

U.S. patent 4,305,992 discloses flexible intumescent sheet materials suitable for use in mounting autmotive catalytic converter monoliths.

i These materials contain unexpanded ammonium ion-exchanged vermiculite flakes.

U.S. patent 4,328,187 discloses an elastic holder for axlal suspension of a ceramic catalytic monolith within a housing. The monolith is surr(cunded with a layer of heat-resistant mineral fiber material. Overlying this fiber layer is a jacket or sleeve of good Sheat-insulating mineral material. Overlying the sleeve is a layer made fro i a highly-elastic material such as foam, asbestos or glass fiber

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Y- i 84-P-1463 fleece, or from a metallic wire mesh cushion which serves as a damping element which extends within the housing over the entire length of the monolith and elastically suspends the monolith together with its ceramic fiber wrapping and sleeve against the walls of the housing.

U.S. patent 4,335,077 discloses support of a ceramic catalytic monolith by means of elastically deformable damping rings or envelopes.

In one embodiment the monolith is surrounded by a protective jacket of heat-resistant cement or putty reinforced with ceramic fibers. This protective jacket may be reinforced with metal in the form of a wire mesh or the like. The protective jacket is enveloped around its circumference by a soft mineral fiber layer which is compressed between the housing wall and the protective jacket, U.S. patent 4,353,872 discloses support of a ceramic catalytic monolith within its casing by means of a gas seal member formed of heat-resistant and expandable sheet material, for example, vermiculite, quartz or asbestos, which envelopes a portion of the monolith.

Longitudinally displaced therefrom is a separate layer of generally cyllndrically knitted wire or resilient support which Is disposed between the monolith and its casing to dampen external forces applied to the monolith.

U.S. patent 4,425,304 discloses a catalytic converter in which ceramic catalytic monoliths are supported by an elastic pad of expanded metal or steel mesh fabrics or a knitted web of ceramic fibers at their ends and are wrapped with respective cushioning layers of expanded metal or any other known flame-retardant, corrosion-resistant cushioning material.

U.S. patent 4,432,943 discloses an elastic suspension for a monolithic catalyst body in which the annular space between the housing and the catalyst body is filled with heat-resistant mineral fiber J, material which serves to prevent bypass of exhaust gas and as thermal insulation, In another construction the monolith is surrounded by a mineral fiber layer and a rigid sleeve of heat-resistant metal is i; a\ 0: i; F I i 84-P-1463 positioned over the mineral fiber layer. The annular space between the sleeve and the housing may be filled with ceramic fiber.

Many of the aforedescribed means for support of a ceramic catalytic monolith have been adopted commercially for use In connection with gasoline powered passenger automobiles. In this type of service, the maximum converter temperatures are generally under 1600 0 F. When attempts have been made to secure the ceramic monolith utilizing materials such as those disclosed in U.S. patent 3,916,056 and 4,305,992 in vehicles having a higher gross vehicle weight (GVW), failures have occurred which are \b believed due to failure of known Intumescent sheet materials. One mode of failure observed is fragmentation of the ceramic monolith, another mode of failure has been shredding of the Intuiescent sheet material and consequent plugging of the next monolith in sequence. Large passenger automobiles may utilize catalytic converters which include two ceramic monoliths. Vehicles of higher gross vehicle weight, e.g. trucks, may require four serially arranged monoliths. Because of Lheir high GVW, the se e engines of such vehicles operate at a much higher percentage of their maxiumum output, a much greater percentage of their operating time, than do the engines in passenger automobiles. These operating conditions in .a heavier vehicles result in maximum catalytic converter temperatures of S much greater than 1600 0 F. Converter monolith temparatures of 2000°F are not uncommon and temperatures of 2500°F may be encountered.

A typical passenger automobile catalytic converter utilizes a ceramic monolith which is supported by intumescent sheet material 'ike that described in U.S. patents 3,916,057 or 4,305,992, having a nominal thickness of 0.195 inch and a nominal density of 40 pef, This material is compressed during installation of the ceramic monolith Into its metallic shell to a nominal thickness of 0.130 inch and a nominal density of about 60 t: nds per cubic foot (pcf). Such a construction does not ?0 withstand the higher operating temperatures often encountered in the operating cycle of a higher GVW vehtcle such as a truck. To overcome these deficiencies, it has been suggested that the overall nominal 4 I I _M 7 thickness of the compressed Installed Intumescent layer be Increased to about 0.24 Inch and the nominal density be increased to about 65-70 pounds per cubic foot as Installed. While this latter construction does not immediately fail, It has been found after operation for a period of time that the layer of Intumescent sheet material adjacent the catalytic converter was totally degraded, thus giving rise to the possibility of such degraded layer shredding and plugging the next monolith In sequence or the degradation continuing until the pre-compression force is released and the monolith is free to bounce about within the shell and self-destruct due to mechanical shock.

Brief Summary of the Invention The primary purpose of this invention is to provide an improved mounting for a frangible ceramic catalytic monolith which is suitable and very convenient for mass manufacture and for use in the exhaust systems of automotive internal combustion engines, particularly where converter operating temperatures of 2000°F or more are anticipated.

According to the present invention, this purpose is accomplished by 0 provision of a device for treatment of exhaust gases from an internal combustion engine comprising: a) a housing having an inlet at one end and an outlet at its **e opposite end through which exhaust gases flow; G:s: b) a frangible ceramic monolith disposed within said housing, said monolith having ail outer surface and an Inlet end face at one end In communication with said inlet of said housing and an outlet end face at its opposite end in communication with said outlet of said housing; c) a ceramic fiber layer in contact with and covering at leist a portion of said outer surface of said monolith; and all d) an Intumescent layer, as herein defined, disposed between said housing and said ceramic fiber layer resillently supporting said monolith S0 In said housing.

According to another aspect of the present Invention, there is i provided a catalytic converter for purifying exhaust gases of an Internal combustion engine comprising: a) a hollow metallic housing having an inner surface and inlet at one end and an outlet at the other end; b) a frangible gas-pervious ceramic monolith catalyst element disposed within said housi.'g, said catalyst element having an Inlet end 300U NT j/ I ID f *c I_

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8 face in communication with said inlet of said housing and an outlet end face in communication with said outlet end of said housing; c) means thermally insulating and resiliently mounting said catalyst element in spaced relationship from said housing comprising; d) a layer of ceramic fibers capable of resisting continuous exposure to temperatures of at least 2000°F covering and in contact with at least 70 percent of said outer surface of said catalyst element between its end faces; and at least one layer of intumescent sheet material, as herein defined, covering said ceramic fiber layer and contacting said housing and resiliently supporting said monolith in said housing.

According to a further aspect of the present invention, there is provided a method of mounting a gas-pervious ceramic monolith catalyst element having inlet and outlet end faces within a housing comprising the 0 15 steps of: *A S) wrapping a layer of ceramic fiber paper around the monolith between its inlet and outlet end faces; b) wrapping said ceramic fiber paper layer wrapped monolith with intumescent sheet material, said intumescent material being as herein defined, to form an assembly; and c) forming a housing around said assembly in which said ceramic fiber paper and intumescent sheet material are radially compressed between said monolith and said housing.

"Intumescent layer" or "intumescent sheet material" is to be taken to ?5 comprise expandable mica.

The Intumescent sheet material functions as a resilient mounting material by expansion in situ. The intumescent layer compensates for differences in thermal expansion of a metal housing and a ceramic *vj substrate, for vibration transmitted from the metal housing to the ceramic substrate and for the Irregularities in the metallic and ceramic surfaces.

Description of the Drawing Figure 1 is a fragmentary itometric view of a device embodying the invention.

Detailed Description of the Invention Referring to the Figure, there is shown at numeral 10 a catalytic converter generally. Catalytic converter 10 includes a generally tubular JFM/5300U 4 i i aanamp 8A housing 12 formed of two pieces of metal, eg high temperature-resistant steel. Housing 12 Includes an inlet 14 at one end and an outlet 15 (not shown) at its opposite end. The inlet 14 and outlet 15 are suitably formed at their outer ends whereby they may be secured to conduits in the exhaust system of an internal combustion engine. Device 10 contains a 0

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j 3FM/5300U 84-P-1463 frangible ceramic monolith 18 which is supported and restrained within housing 12 by layers 20, 22 and 23 to be further described. Monolith 18 Includes a plurality of gas-pervious passages which extend axially from its inlet end face at one end to its outlet end face at its opposite end. Monolith 18 is constructed of a suitable refractory or ceramic material in known manner and configuration. Monoliths are typically oval or round in cross-sectional configuration.

In accordance with the present inve 1 mtion, the monolith is spaced from its housing at least about 0.2 inch. The outer surface of monolith 18 is tC wrapped with a layer 20 of ceramic fibers. Preferably, for intended monolith operating temperatures of up to 2000 0 F, the ceramic fiber layer 20 has an installed nominal thickness of at least 0.03 inch and an Installed nominal density of at least about 40 pcf. Overlying this layer 20 of ceramic fibers there is provided a layer 22, 23 of intumescent sheet material which is in contact with the ceramic fiber layer 20 and the metal housing 12. Preferably, the Intumescent layer 22, 23 has an Installed (compressed) nominal thickness of at least about 0.2

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inches and an installed nominal density of about 70 pcf, Preferably and conveniently, layer 20 is in the form of ceramic fiber a 6( paper. However, other ceramic fiber forms sucil as blanket, mat or felt may be employed, provided they Impart the necessary thermal insulation and mechanical support as provided by a layer of ceramic fiber paper.

While in Figure 1 the Intumescent material is shown to be provided in the form of layers 22 and 23, which are superposed upon ceramic fiber layer 20, a single layer of Intumescent material may be employed if available In the requisite thickness and density, The ceramic fiber paper may be laminated to the Intumescent layer prior to assembly in a catalytic device.

Ceramic fiber papers suitable for use in the present invention are G preferably free of vermiculite. Small amounts of vermiculite may be present In the ceramic fiber paper layer, e.g, up to about 30 weight percent; however, the presence of such vermiculite Is not recommended and -9i 7CI-I~ i 84-P-1463 may reduce the service temperature and life of monolithic catalytic converters employing such ceramic fiber paper. The presence of vermiculite, including ammonium-ion exchanged types, may reduce the S effectiveness of the ceramic fiber layer, particularly by causing its degradation at temperatures lower than that of the ceramic fibers in the absence of vermiculite.

An eminently suitable material for monolith temperatures up to 2300°F for ceramic fiber layer 20 has been found to be Fiberfraxe 970 paper available from Sohio Engineered Materials Company, Niagara Falls, New York. This product is made from bulk alumlno-sillcate glassy fiber having approximately 50-50 alumina/silica and a 70/30 fiber/shot ratio.

About 93 weight percent of this paper product is ceramic fiber/shot, the remaining 7 percent being in the form of an organic latex binder. For etm even higher monolith temperatures, papers produced from Fibermaxtm polycrystalline mulllte ceramic fibers available from this manufacturer may be employed. Alumina fibers may also be employed where high monolith temperatures are expected.

In a typical assembly intended for use with 2-10 -ton trucks, the ceramic monolith is of round cross-sectional configuration and measures approximately 6 incles in diameter and has a length of about 3 inches.

S For the construction of a converter whose monolith is expected to operate at temperatures up to 2500 0 F, a layer of Fibermaxtm ceramic fiber paper having a nominal uncompressed thickness of about 0,125 inch and a nominal uncompressed density of about 12 pcf is wrapped around each monolith.

Thereafter, two layers of intumescent sheet material like that described in U.S. patents 3,916,057 or 4,305,992, each having a nominal -I uncompressed thickness of about 0,200 inch and a nominal uncompressed density of 40 pnf, are wrapped around the layer of ceramic fiber paper.

This combination of monolith, ceramic fiber paper and intumescent sheet material layers is then Inserted into one of the members corresponding to those which form h6Jsing 12. Thereafter, the assembly is Installed by radially compressing between the members of the housing so that the -lOr 84-P-1463 combined thickness of the ceramic fiber paper and intumescent sheet material layers is reduced to about 1/4 inch and the density of the combined layers is increased to about 70 pounds per cubic foot.

Preferably, the ceramic fiber layer and intumescent layers extend longitudinally at least about 70 percent of the monolith length.

Preferably, the ceramic fiber and intumescent layers do not extend beyond the length of the monolith. The metal housing extends beyond the ends of the monolith. After compression of the members forming the housing, their edges are either folded over as illustrated in Figure 1 or welded O1 longitudinally to form a gas-tight housing.

While not completely understood, there appears to be a direct relationship between the density of the ceramic fiber paper layer and intumescent material layers and the maximum use temperature of the catalytic device, For example, when the maximum intended monolith service temperature is about 1600 0 F, adequate service life is provided when vermlculite-contalning Intumescent material, according to U.S.

patents 3,916,056 and 4,305,992 is alone employed at an Installed density of about 45-60 pcf. When the maximum intended monolith service temperature is elevated to 1825 0 F, adequate service life may be obtained if the installed density of such intumescent material layers is about pcf.

When the maximum intended service temperature of the monolith is elevated to 2000 0 F, such intumescent sheet material, even at an installed depsity of 70 pcf and an installed thickness of 0.240, degrades adjacent the monolith. Laboratory experiments indicate that provision of a 0.035-inch installed thickness and 43 pcf installed density ceramic fiber paper layer reduces the temperature at interface of the ciiramic fiber paper and such intumescent sheet material by 107-114 0 F. Preferably, the ceramic fiber paper layer is of sufficient thickness to l\mit the maximum temperature of the Intumescent layer to less than 1900F and more desirably to 1850°F or less.

5 -I 84-P-1463 Increasing or decreasing the Installed density of the ceramic fiber and intumescent material layers does not significantly change the thermal insulation properties of these layers per unit of thickness, but does significantly affect the restraining force imposed on the monolith. The restraining force at 75 0 F increases directly with an increase in installed density.

While a presently preferred embodiment of the invention has been illustrated and described, it will be apparent to thse skilled in the art that modifications thereof are within the spirit and scope of the O invention. For example, the monolith may be an electrically resistant-heated element. The monolith may serve as a regenerable particulate trap. For example, in assemblies where even higher monolith operating temperatures are anticipated, e.g. 2500 0 F, the ceramic fiber paper layer which is in contact with the monolith should be formed, for example, of Fibermaxtm polycrystalline mullil:e fibers or of alumina fibers to thermally insulate the radially outer layers of vermiculite-contalning intumescent material from exceeding their maximum continuous use temperature. The ceramic monolith may be first wrapped in polycrystalline alumino-silicate fiber, then wrapped with vitreous ,o's alumino-silicate fiber and then wrapped with intumescent material. The outside temperature of the housing of the catalytic converter may be Sreduced by increasing the thickness of the combined ceramic fiber and intumescent material layers. For simplicity of illustration, housing 12 has been shown to be smooth. In most applications, however, it is recommended that the housing be ribbed or otherise reinforced to stiffen it to resist the force exerted by the compressed ceramic fiber paper and intumescent sheet materials.

"Ceramic fibers" as used herein include those formed froi basalt, industrial smelting slags, alumina, alumino-silicates 3j' and chrome, zircon and calcium modified alumino-silicates and the like.

-12- 7 4 12A COMPARATIVE EXAMPLE A catalytic converter device was made by wrapping a six inch diameter by 3.2 inch long catalyzed cordierite ceramic monolith catalyst substrate with two layers of Carborundum XPE 3100 g/m 2 intumescent sheet material (typical chemical analysis: 30wt%-45wt% alumina-silica ceramic fiber, 45wt%-60wt% expanded vermiculite and 6wt%-15wt% organic binder) which assembly was subjected to compression as the assembly was encased in a metal shell. The catalytic converter device was then subjected to continuous vibration of 28 G's at 100 hertz while the entire exhaust gas stream from a 7.5 liter truck engine was forced through it. The exhaust gas temperature as measured at the inlet of the catalytic converter device was adjusted to 1760 0 F 50°F by adjusting the operating conditions of the engine and these conditions were continued for five hours with continuous vibration. The catalytic converter device remained intact with no adverse effect observed. Thereafter, the temperature of the exhaust gas at the inlet of the catalytic device was increased to 1950 0 F 50°F by S adjusting the operating conditions of the engine while continuing S vibration. The assembly lasted one minute at these conditions before failure. Trar down inspection of the catalytic converter device subsequent to the test procedure revealed that failure was caused by migration of the intumescent material from the gap between the monolith catalysts substrate .o o and the metal shell, This migration allowed the substrate to vibrate in the metal shell. Substrate movement of over one-fourth inch was deemed to constitute failure for the device. There was no sign of intumescent sheet material decomposition. It is thought that the intumescent sheet material simply relaxed sufficiently in the high temperature environment to enable 25 the monolith substrate to shake loose.

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EXAMPLE

S A catalytic converter device was assembled whose construction was identical to that descibed in the comparative example except that a one-eighth inch thick (before decompression) layer of Fiberfrax 970 paper (Fiberfrax is a trade mark) was placed between the ceramic monolith and the intumescent sheet material. The catalytic converter device was then subjected to the same testing procedure as used in the comparativa example. After five A,7 12B hours at 1760 0 F 50°F with continuous vibration without failure, the inlet gas temperature was Increased to 1950°F 50°F with continuing vibration and these conditions were maintained for five hours, At the end of the ten hour total cycle no failure was observed. Examination fo the catalytic converter device at the end of the ten hour test disclosed no substrate movement the device retaining full functionality.

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Claims

1. Device for treatment of exhaust gases from an internal combustion engine comprising: a) a housing having an inlet at one end and an outlet at its opposite end through which exhaust gases flow; b) a frangible ceramic monolith disposed within said housing, said monolith having an outer surface and an inlet end face at one end in communication with said inlet of said housing and an outlet end face at Its opposite end in communication with said outlet of said housing; c) a ceramic fiber layer in contact with and covering at least a portion of said outer surface of said monolith; and d) an intumescent layer, as herein defined, disposed between said housing and said ceramic fiber layer resiliently supporting said monolith in said housing.

2. The device of claim 1 wherein said ceramic fiber layer is selected from the group consisting of ceramic fiber mat, ceramic fiber blanket, ceramic fiber felt or ceramic fiber paper. 0at

3. The device of claim 1 or claim 2 in which said ceramic fiber layer is ceramic fiber paper which contains less than 30 percent by weight of vermiculite, which paper Is capable of iesisting continuous exposure to temperatures of at least 2000 0 F.

4. The device of claim 1 in which said ceramic fiber layer is vermiculite-free ceramic fiber paper. The device of claim 3 In which the ceramic fiber paper is of a thickness sufficient to limit the maximum temperature of the intumescent layer to less than 1900°F when the monolith Is at its intended maximum continuous operating temperature.

6. The device of claim 1 in which said ceramic fiber layer Is of a thickness sufficient to limit the maximum temperature of the interface S between the intumescent layer and the ceramic fiber layer to less than 1850°F when the monolith Is at Its intended maximum continuous operating temperature. S 7. The device according to claim 3 wherein the ceramic fiber paper S° has an Installed nominal thickness of at least 0.035 inches and an installed nominal density of at least 40 pounds per cubic feet.

8. The device of claim 4 wherein the intumescent layer contains ion-exchanged vermiculite and the ceramic fiber layer limits the maximum JLH OOU TO l~ ~l ":I'LC C- L- -L I-lr. -Ir- i r ~ii_,l i. r .y~I 14 temperatur, of the intumescent layer to not more than 185 0 °F during continuous treatment of exhaust gases.

9. The device of claim 8 wherein the monolith intended operating temperature Is greater than 1900°F. The device of claim 8 wherein the monolith internded operating temperature is at least 1950 0 F.

11. The device of claim 1 wherein the ceramic fiber layer has an installed nominal thickness of at least 0.03 inch and an installed nominal density of at least 40 pcf.

12. The device of claim 1 wherein the intumescent layer has an installed nominal thickness of at least 0.?2 inches and an installed nominal density of 70 pcf.

13. A catalytic converter for purifying exhaust gases of an internal combustion engine comprising: a) a hollow metallic housing having an inner surface and inlet at one end and an outlet at the other end; b) a frangible gas-pervious ceramic monolith catalyst element disposed within said housing, said catalyst element having an inlet end face in communication with said inlet of said housing and an outlet end face in communication with said outlet end of said housing; c) means thermally Insulating and resiliently mounting said catalyst element in spaced relationship from said housing comprising; "r d) a layer of ceramic fibers capable of resisting continuous exposure to temperatures of at least 2000°F covering and in contact with at least 70 percent of said outer surface of said catalyst element between its 4o. end faces; and e) at least one layer of intumescent sheet material, as herein defined, covering said ceramic fiber layer and contacting said housing and resiliently supporting said monolith in said housing.

14. The catalytic converter of caim 13 wherein said layer of ceramic fibers Is selected from the group consisting of ceramic fiber mat, 0 4 ceramic fiber blanket, ceramic fiber felt or ceramic fiber paper.

15. The catalytic converter of claim 13 wherein said inner layer of ceramic fibers has an uncompressed nominal thickness of at least 1/16 inch and an uncompressed nominal density of at least 12 pcf.

16. The catalytic converter of claim 13 wherein the ceramic fib#Q ~iRi ~FP c AN,'A 4'~ I \I 15 I layer has an Installed nominal thickness of at least 0.030 Inch and an Installed nominal density of at least 40 pounds per cubic foot.

17. The catalytic converter of claim 16 wherein said catalyst monolith element is spaced from said housing at least 0.2 inch.

18. The catalytic converter of claim 16 wherein said intumescent sheet material has an uncompressed nominal thickness of 0.4 inches, an uncompressed nominal density of 40 pcf and the Installed ceramic fiber layer and intumescent sheet material layers have a combined thickness of 1/4 inch and a combined density of

19. The catalytic converter of claim 15 wherein said intumescent sheet material layer has an uncompressed nominal density of 40 pcf. The catalytic converter of claim 19, including two layers of intumescent sheet material, each having an uncompressed nominal thickness of 0.2 inch.

21. The catalytic converter of 0:laim 13 wherein said Intumescent sheet material layer has an installed ncminal thickness of at least 0.2 inches and In installed nominal density of 70 pcf.

22. The cataiytic converter of claim 13 wherein the monolith element is wrapped with a layer of ceramic fiber paper which comprised 93 weight percent ceramic fiber having a 70/30 fiber-to-shot ratio, said ceramic fiber being alumino-silicate glassy fiber having an alumina content of weight percent, said ceramic fiber paper having an installed thickness of 0.035 inches and an installed density of 43 pounds per cubic foot and said intumescent layer includes two layers of a material comprising from 40 to weight percent unexpanded vermiculite flakes which have been treated in 0o4i an aqueous ammonium solution to substantially complete the Ion exchange 444 with NH+ cations, from 25 to 50 weight percent inorganic fibrous 4 material and from 5 to 15 percent of binder, said intumescent layer upon exposure to heat In excess of 350°C undergoing thermal expansion.

23. A method of mounting a gas-pervious ceramic monolith catalyst element having inlet and outlet end faces within a housing comprising the steps of: 2?" ,ce 0 Ps a) wrapping a layer of ceramic fiber paper around the monolith between Its inlet and outlet end faces; b) wrapping said ceramic fiber paper layer wrapped monolith with intumescent sheet material, said intumescent sheet material being as herein defined, to form an assembly; and 16 c) forming a housing around said assembly in which said ceramic fiber paper and intumescent sheet material, are radially compressed between said monolith and said housing.

24. The method of claim 23 wherein the ceramic fiber layer has an installed nominal thickness of at least 0.03 Inch and an installed nominal density of at least 40 pcf. The method of claim 23 or claim 24 wherein the intumescent layer has an installed nominal thickness of at least 0.2 inches and an installed nominal density of about 70 pcf.

26. A catalytic converter for purifying exhaust gases of an internal combustion engine, substantially as herein described with reference to Fig. 1. DATED this TWENTY-THIRD day of FEBRUARY 1990 Kennecott Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON i 46 4o4' 4 4 (O 4 4 1 -L :i i