US3197287A - Catalytic converter - Google Patents

Description

July 27, 1965 w. B. INNES ETAL 3,197,287

CATALYTIC CONVERTER Filed April 5. 1961 ATTORNEY 2 Sheets-Sheet lv July 27, 1965 w. B. INNEs ETAL 3,197,287

CATALYTIC CONVERTER Filed April 5. 1961 2 Sheets-Sheet 2 Fly. 2

IN V EN TORS A W/Z L /AM B. INA/ES y BY R/CHED DUFFY ATTORNEY United States Patent() "i 3,197,287 CATALYTIC CGN VERTER William B. Innes, Stamford, Conn., and Richard Duffy, Mount Vernon, N.Y., assignors to American Cyanamid Company, New York, NX., a corporation of Maine Filed Apr. 3, 196i, Ser. No. 100,18) 1 Claim. (Cl. 23-288) This invention relates to an apparatus of the type employa-hle with an internal combustion engine 'for oxidizing the toxic and obnoxious gases 'of hydrocarbon combustion exhaust gases.

More particularly, the present invent-ion relatos to a catalytic converter which also serves as a muffler and is capable of being readily inserted into the exhaust system of an internal combustion engine.

The exhaust gases from the combustion of hydrocarbon fuels such as gasoline, diesel fuel and the like in internal combustion engines contain mixtures of carbon monoxide, various saturated and unsaturated hydrocarbons, nitrogen :oxides and other constituents. These mixtures are both poisonous and obnoxious. In addition to the known hazardsresulting from inhalation of combustion exhaust gases of hydrocarbon fuels, such gases have of comparatively recent times lbeen identified with smog formation.

Thus, itis known that exhaust gases from automobiles, particularly the unsaturated hydrocarbon and nitrogen oxide components, are precursors of photochemical smog -in heavily populated metropolitan centers of this country, such as Los Angeles, California. Smog, as the term is generally employed, is broadly understood Ito refer to a variety of phenomena which are related to the interaction of nitrogen oxides, hydrocarbons and sunlight. These include a fog-like haze, high oxidant concentration in the atmosphere (mostly ozone), eye irritation, plant damage and the like.

The hazards and nuisance created by hydrocarbon exhaust gases from internal combustion engines have over the years resulted in the development of a number of processes and device whereby the reduction or elimination of the harmful components of these exhaust gases has been the primary object.

A relatively common device employed for this purpose has been what is sometimes referred to as a catalytic muffler which normally refers to a device which is to be substituted into the exhaust line of an internal cornbustion engine in lieu of a mufiier. Such devices are inserted into the exhaust line of an internal combustion engine and by the action of catalysts contained therein combustible engine exhaust components are oxidized, resulting in reduced amounts of the harmful and obnoxious constitutents passing into the atmosphere.

For the successful operation of such catalytic muiers, it is ordinarily necessary that oxygen be supplied lto the exhaust gases in order that there be full combustion of the exhaust products. Depending upon operating condition, the amount of oxygen or air necessary to effect complete `combustion varies. Thus, as much as 30% additional oxygen or air might have to be supplied to the exhaust line in order .to effect complete combustion of the exhaust products during startup or decelerating conditions. While the engine is idling, from 20-40% added oxygen or air must normally be supplied to the exhaust line. During cruising conditions, approximately -l0% must be admixed. It will thus lbe seen that if complete combustion of the exhaust products is to be effected and thus avoid the discharge of harmful and obnoxious hydrocarbon exhaust components into the atmosphere, additional quantities of oxygen or air must ordinarily be inducted .into the exhaust line during all conditions of Patented July 27, 1965 operation, particularly `during startup or idling. The successful operation of any catalytic muiiler thus depends upon the addition or supply of an additional quantity of oxygen or air .to the unit in order to accomplish maximum efficiency rfrom the catalytic unit. However, the induction of oxygen or air presents numerous problems, the fore-most of which is a frequently uncontrollable rise in the temperature of the catalyst bed of the catalytic muier unit and attendant damage to 4the catalyst whereby the eiiiciency of the unit is diminished over a period of extended operation. Moreover, such high temperatures frequently cause damage to the container. If the air to exhaust gas ratio is maintained at about l to 7 or higher as is required for proper conversion at low engine speeds, it will be readily appreciated that at high speeds when the temperatures of inlet gas to the muffler -is high and when the amount of combustibles leaving the engine is the equivalent in caloriiic content of over 5% carbon monoxide (e.g., during acceleration), then t-he temperature of the catalyst beads, granules, pellets and the like will rise excessively and the container will be damaged. An additional .problem previously faced has been that very frequently when other air induction apparatuses were used a high pressure drop in the system was encountered. This drop caused power -loss at high speeds as 'well as excessive valve, wear thereby reducing the etiiciency of the engine.

It is therefore an object of this invention to provide a catalytic converter whereby a near constant amount of air will be inducted and thus to maintain the temperature of the catalyst bed at an optimum level.

It is a further object of this invention to provide a catalytic converter whereby the exhaust gas is selectively cooled at high engine speeds and thereby to obtain more effective control of the temperature in the catalytic unit. It is a Afurther object of this invention to provide a catalytic converter for maintaining the temperature of the catalytic unit at a desirable level without the necessity of costly automatic temperature controls.

It is a still further object of this invention to provide a catalytic converter for eliminating power loss at high speed resulting'from high presure drop in an exhaust gas system.

lt is a ,still further object of this invention to provide a low cost catalytic converter for supplying a near constant amount of air into an exhaust system which obviates the necessity of induction systems having high energy requirements. These and other objects, advantages and features of the present invention will become more apparent in the description set forth, which description is particularly in reference to the accompanying drawings of which FIGURE 1 is a longitudinal cross-sectional view of a catalytic converter contemplated by this invention, and FIGURE 2 is a longitudinal cross-sectional view of a further embodiment of a catalytic converter contemplated by this invention.

In accordance with the present invention a catalyticV converter is provided comprising a generally cylindrical chamber having an inlet and outlet for the passage therethrough of a hydrocarbon combustion exhaust gas stream. Venturi means connected to said inlet are provided within said chamber for inducting airinto said exhaust gas stream by means of an air inlet port. Conduit means communicate with said inlet 0f the chamber and are positioned before the venturi and subsequently terminate at the outlet of the chamber. Within the conduit are means for permitting the flow therethrough of at least a portion of the exhaust gas stream and through the outlet but not through the venturi. Communicating with the outlet of the chamber is a catalytic unit or housing containing oxidation catalyst therein, the'inlet of which unit or housing is connected to the outlet end of the chamber. A

principal feature of this invention is the conduit means whereby at higher speeds a portion or fraction of the exhaust gases may by-pass the venturi induction means and thus the exhaust gases are selectively cooled and better control of temperature in the catalytic unit is achieved. The means within the conduit for permitting the flow of at least a portion of the exhaust gas stream through the conduit but not through the venturi are either a pressure responsive or thermally responsive valve which opens at various high speeds and thus allows a near constant amount of air to be inducted into the exhaust system without a high pressure drop. This induction of a near constant amount of air enables the temperature of the catalyst bed to be maintained at an optimum and desirable level since the by-pass stream because of its being permitted to ilow through a conduit external of the venturi means is cooled to a large extent and at the time of its entrance into the catalytic unit, its temperature is markedly reduced. Because the amount of oxygen added is limited, the temperature of the catalyst bed will thus be maintained at an optimum level.

Referring to FIGURE 1 of the drawings, in which a specic illustrative embodiment of this invention is shown, it will be seen that 11 designates an exhaust pipe carrying engine hydrocarbon combustion exhaust gases from the engine exhaust manifold to a catalytic unit indicated generally by reference numeral 12. Before exhaust gases flow into catalytic unit 12, they pass through venturi type inspirator comprising a converging nozzle 13 and an,

element generally designated by numeral 14 comprising a portion 15 converging in the direction of gas flow and a portion 16 diverging in the direction of gas flow which are connected to form a throat 17. The converging portion forms a chamber 13 around the nozzle 13 which communicates with the atmosphere by means of air inlet 19 provided with an air lter (not shown). Alternatively, however, the air inlet may be connected to the cranlccase. In operation, the exhaust gases ilow through the nozzle 13, creating a reduced pressure at throat 17, thereby causing the inspiration of air through air inlet 19, the air-exhaust gas mixture thereupon owing into zone 2t) and thence into catalytic unit 12 which contains oxidation catalyst therein to the atmosphere through outlet tube 21. Interpositioned between the venturi type inspirator and the exhaust manifold on the exhaust pipe 11 are two openings 22 and 22A, the iirst of which leads into and communicates with conduit 39 which terminates at the portion of the chamber generally designated as 2l). The first of said openings carries a shoulder or seat 23 whereupon is positioned a thermally responsive or pressure responsive valve 24 with guidepins 25 carried on valve stem 26 which is tted for transverse movement through opening 22A. To insure proper damping action the valve stem 26 is positioned in a low friction type bearing 27, e.g., one fabricated from polyamide or polyuorohydrocarbon resin. To prevent undue vibration and excessive wear during period of changing gas flow through opening 22 a coil spring 2S of a heat resistant steel alloy contained within housing 29 and anchored to the bottom portion thereof is provided.

FIG. 2 shows a further embodiment of the catalytic converter of this invention wherein the conduit is positioned about the venturi internally of and co-extensive with the chamber whereby the exhaust gases selectively by-pass the venturi unit at high engine speeds and enter the catalytic unit at a point whereat the gases emanating from the venturi also enter the catalytic unit which is made integral with the chamber or conduit and venturi means.

Referring to FIGURE 2, it will be observed that 31 designates an exhaust pipe carrying engine exhaust gases from the engine exhaust manifold to a catalytic unit indicated generally by reference numeral 32. Before exhaust gases flow into catalytic unit 32 they pass through a venturi type inspirator comprising a converging nozzle 33 and an element generally designated by numeral 34 CTL comprising a portion 35 converging in the direction of gas iiow and a portion 36 diverging in the direction of gas iiow which are connected to form a throat 37. The converging portion forms a chamber 38 around the nozzle 33 which communicates with the atmosphere or the cranlrcase through air inlet 39. In operation, the exhaust gases flow through the nozzle 33 creating a reduced pressure` at throat 37, thereby causing the inspiration of air through air inlet 39, the air-exhaust gas mixture thereupon ilowing into zone 4@ and then into catalytic unit 32 to the atmosphere through outlet tube 41. Interpositioned between the venturi type inspirator and exhaust pipe inlet to chamber 42 which is made integral with the catalytic unit 32 is an opening carrying a shoulder or seat 43. Positioned on the shoulder or seat is a thermally responsive or pressure responsive valve 44 with guidepins 45. Resilient means such as a high temperature resistant steel alloy spring 46 is welded or otherwise fixed to the valve 4tand to a plate 47 held by set screw 48 which is threaded through retaining nut 49. Periodic adjustment of the set screw so as to regulate the tension on the spring affords an easy method of auxiliary control of the amount of air admitted during varying levels of engine operation and performance. The air inlet 39 also may be positioned so as to allow the incoming air to pass over and around spring .46 thus avoiding failure of the spring at high temperatures. It will be noted that the chamber 42 itself serves as the conduit for the air-exhaust gas mixture to the catalytic unit when the valve 44 is opened. Catalytic unit 32 comprises a longitudinally extending perforated cylindrical tube 5t) held in place by ring like plates 51 and 52. A longitudinally extending perforated heat resistant sleeve 53 having a cross section greater than said tube 50 is positioned about said tube 50. Sleeve 53 may be welded to the inside surface of plates 51 and 52 or otherwise supported therein by suitably positioned lugs or the like. Plate 52 is secured by rods or arms 54 extending perpendicularly therefrom to end plate 55'. A bed of suitable oxidation catalyst is disposed within the volume defined by the youter surface of tube Sil, the inner surface of sleeve 53, third ring-likeV plate 56 having a centrally disposed opening for tube 50 and plate 52. A plurality of coil springs S7 are provided for maintaining a uniform density within the catalyst bed. Exhaust gases to be oxidized enter perforated tube 50 pass through the catalyst bed and thence through perforated sleeve 53 through the channellike area shown as 53 between the inside surface of the housing and the outside surface of the sleeve to outlet tube 41. Cap 59 made of a low melting alloy is disposed at one end of tube 50 for the purpose of insuring that the catalyst bed will not be prematurely deactivated and the device overheated. Direct exit of the raw exit gases through outlet 41 whereby little or no oxidation is et'- fected is accomplished upon the fusion of cap 59. The catalytic unit designated as 32 and shown in FIG. 2 is more fully described and claimed in copending application, Serial No. 44,674, filed July 22, 1960, now U.S. yPatent No. 3,094,394, issued June 18, 1963.

During startup and idling operation, the pressure responsive or thermally responsive valve ordinarily remains closed. However, during normal or cruising operation, because of the increase in pressure or temperature in the exhaust gas stream resulting from increase in the rate of flow of the exhaust gas stream, the valve will open whereby a portion of the exhaust gas stream will by-pass the venturi inspirator and will be selectively cooled by the time the gases reach the portion of the chamber leading into .the catalytic unit. During deceleration and return to idling conditions, the valve will close and be seated with decreasing pressure or temperature of the gas resulting from diminished rate of flow of the exhaust gas stream.

The catalyst employed in the oxidation catalytic unit should be one of high surface area and one which is characterized by good activity even after repeated exposure to the high temperature of exhaust gases. Typical catalysts which may be employed are those having an instance to the catalytic unit of course was noted to cause 1an excessive rise in the temperature of the catalystV bed; i.e., the temperature was greater than 700 C. and a desirable optimum isabout 600 C.

Reproduced hereinafter in Tables V-VIII are data showing the eiect of engine speed on the performance of the catalytic converter of this invention.

EFFECT 0F ENGINE SPEED ON PERFORMANCE OF CATALYTIC CONVERTER Stationary Engine Speed Table V Table VI Table VII Table VIII Miles per f Inlet HC, Exit HC, Inlet CO, Exit C0, Inlet O2, Exit O2, Inlet Gas Average Hot Hour Rpm. percent percent percent percent percent percent Temp., C. Spot Bed Temp., C.

550 60 09 3. 6 1. 4 3. 6 1. 0 160 520 1, 160 52 04 l. 0 0. 2 4. 0 2. 6 280 460 2, 000 56 02 1.4 0. 2 l 4. 4 2. 4 320 500 2, 860 60 12 2. 2 1. 8 2. 2 0. 2 400 580 75--- 3, 500 1. 70 3S 1. 4 0. 4 460 540 of catalyst which will occupy about 80% by volume of the catalytic unit.

For the purpose of comparison of a catalytic converter of the type embodied by the present invention with a converter having venturi means for inducting air but having no conduit means for permitting the ow of at least a portion of the exhaust gas stream to by-pass the venturi, tests were conducted at varying stationary engine speeds (test automobile jacked up) employing both devices. The results of these tests are summarized in the tables hereinbelow:

The data in Tables V and VI indicate that use of the converter achieves desirable levels of reduction of the hydrocarbon and carbon monoxide components of exhaust gases. The data in Tables V and VI is supplemented by that in Table VII showing that the oxygen admitted is being effectively utilized for the combustion of the hydrocarbon and carbon monoxide components. Finally, the results appearing in Table VIII show that While the temperature of the exhaust gas stream increases rapidly with increase in speed, nevertheless the temperature of the catalyst bed remains within an optimum and desirable range, i.e., from about 450 C. to about 600 C.

COMPARISON OF PERFORMANCE OF CATALYTIC CONVERTERS WITH AND WITHOUT BYPASS CONDUIT Table I Table II Table III Table IV Percent Inducted Cim. Air Total Pressure I l Stationary Engine Speed Air on Exhaust Inducted Drop in in. H2O Igeerlicilt (Miles Per Hour) Catalytic Unit With Without With Without With Without With Without Inspection of the data in Table I shows that when a catalytic converter of the present invention is employed, the percentage air inducted into the exhaust gas stream drops from a maximum at low speeds to minimum at high speeds, Whereas a converter Without the bypass conduit means causes increased amount of air to be inducted with increase in speed. Further, the results appearing in Table II demonstrate that the air inducted, expressed in cubic feet per minute, varies from 2 to 5 if a converter ,-of the present invention is employed while the amount of air inducted if a converter without bypass conduit means is employed markedly increases from a low of 3 c.f.m. to a high of 16 c.f.m. Moreover, the values for the total pressure drop shown in Table III indicate that the converter of the present invention is superior in allowing only a nominal range of variation in pressure drop to a converter without bypass conduit means. Finally, the data tabulated in Table IV readily indicates that the percentage oxygen admitted to the catalytic unit of a converter of the present invention is at all speeds below a level of 4.5%, while levels of as high as 7.0% are achieved with a converter without bypass conduit means. The admittance of high percentage oxygen in the latter It will be evident from the present description that the use of the catalytic converter of this invention results in -a near constant amount of air induction whereby the ternperature of the catalytic unit is -maintained at an optimum level without the necessity of providing automatic temperature control. Moreover, it will be apparent that a near constant amount of air induction whereby the temsystem without a definite high pressure drop whereby a portion of the exhaust gas stream is selectively cooled and the result is better temperature control in the catalytic unit. It will be further noted that because of the novel arrangement of the component parts, the converter is lower in cost and energy requirements than that of other air induction system, for example, an apparatus supplying air by means of a battery driven pump. While the catalyst unit set forth in the preferred embodiment of FIG. 2 has been that described and claimed in copending application Serial No. 44,674, tiled July 22, 1960, now U.S. Patent 3,094,394, it is to be understood that other catalytic units similar in purpose to the -unit so disclosed therein may also be employed. It will also be apparent that other numerous modifications and advantages of this in- 7 vention will be obvious and, therefore, no limitations should be set therein except insofar as they appear in the appended claim.

Ve claim:

An apparatus for oxidizing toxic and obnoxious components of hydrocarbon combustion exhaust gases comprising:

a chamber having an inlet, a restricted throat portion adjacent to said inlet and an outlet for the passage therethrough of said gases and an inlet for admitting air into said throat portion; bypass conduit means communicating with said rst inlet and terminating at said outlet, said chamber being positioned internally of, coextensive with and integral with said conduit means; control means positioned within said conduit means for permitting the ow of at least a `portion of said exhaust gases through said conduit but not through said throat portion, said control means opening in response to an increase in pressure of said exhaust gases; and

a housing having an inlet and an outlet and adapted to contain oxidation catalyst therein, the inlet of said housing connected to the outlet of said chamber.

References Cited bythe Examiner l UNITED STATES PATENTS MORRIS O. WOLK, Primary Examiner.

20 GEORGE D. MITCHELL, MAURICE A. BRINDISI,

Examiners.

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