CA1165247A

CA1165247A - Exhaust gas purification

Info

Publication number: CA1165247A
Application number: CA000355115A
Authority: CA
Inventors: Stephen L. Cutmore; Edward R. Middleton; Bernard E. Enga
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 1979-06-29
Filing date: 1980-06-30
Publication date: 1984-04-10
Also published as: GB2054402A; FR2460388B1; DK155541B; GB2054402B; LU82550A1; NL8003699A; FR2460388A1; IT8012584A0; SE8004632L; IT1136188B; IE49846B1; DK155541C; IE801344L; DK279280A; DE3024491A1

Abstract

ABSTRACT
This invention relates to the reduction of smoke and other noxious components contained in gases and in particular exhaust gases.
In more detail the invention provides an internal combustion engine including apparatus for reducing pollutants contained in exhaust gases emitted from the engine having at least one exhaust port, the apparatus comprising a casing defining a chamber containing a catalyst, the catalyst including a substrate made from filamentary metallic material in knitted, woven or crushed form, a first layer of a refractory metal oxide applied to the substrate and a second layer of a catalytic material applied to the first layer, the chamber having an inlet in communication with the said exhaust port via which exhaust gas emitted from the engine is lead into the chamber and passed through the catalyst prior to passage through an exhaust system to atmosphere.

Description

1~6SZ47 This invention relates to the reduction of smoke and other noxious components contained in gases and in particular exhaust gases.
Gases from boilers and internal combustion engines often contain finely divided particles of hydrocarbons and/or carbon or other solid matter which emerge in the form of smoke. The smoke from a diesel engine is composed of solid/
liquid particles (i.e., solid particles having a liquid outer covering ~ayer), solid chain aggregates in which spherical particles of between 100-800~ diameter link up together, liquid sulphates, l.iquid hydrocarbons and gaseous hydrocar-bons. The solid/liquid particles generally comprise carbon particles with adsorbed liquid hydrocarbons and the solid chain aggregates are generally composed of high molecular weight organic compounds and/or inorganis sulphates.
White smoke i5 produced when the engine first starts up and results from the condensation of water vapour on to particulates contained in the exhaust gas so that a fine mist is formed. Black smokes produced by diesel engines are formed when the engine has warmed up and contains a relatively ~165Z~7 high proportion of carbon particles. In blue smoXe there is some carbon but also a relatively high proportion of gaseous organic compounds such as aldehydes. About 90~
of these smoke forming particles have maximum dimensions of less than one micron which is within the respirable particle size and the maximum dimension of the remaining 10~ of these smoke forming particles are less than four microns.
One object of the present invention is at least to reduce the quantity of smoke contained in waste gases by effecting the catalytic oxidation of smoke forming parti-cles in the~e gases.
A second object of the present invention is to reduce the quantity of noxious gases and particulates present in exhaust gas of an internal combustion engine.
A further object of the present invention is to pro-vide a modified diesel or petrol driven internal combus-tion engine such that a considerable reduced quantity of noxious gases and particulates is produced.
In this specification the term "pollutants" should be taken to include hydrocarbons, carbon monoxide and oxides of nitrogen formed by the internal combustion engine as well smoke forming particles described above.

1165~47 According to a first aspect of the present invention internal combustion engine includes apparatus for reducing pollutants contained in exhaust gases emitted from the engine having at least on exhaust port, the apparatus com-prising a casing defining a chamber containing a catalyst, the catalyst including a substrate made from filamentary metallic material in knitted, woven or crushed form, a Eirst layer of a refractory metal oxide applied to the substrate and a second layer of a catalytic material applied to the first layer, the chamber having an inlet in communication with the said exhaust port via which exhaust gas emitted from the engine is lead into the chamber and passed through the catalyst prior to passage through an exhaust system to atmosphere.
lS Usually, the catalytic oxidation of carbon particulates takes place at about 400C whereas the normal temperatures of combustion of such particulates is 700-800C. For hydro-carbon particles catalytic oxidation will take place at temperatures about 200C. The effect of a catalyst on the temperature at which catalytic oxidation of particulates entrained in the exhaust gas stream of a diesel engine took place were studied. ~ number of sample catalysts were prepared. The catalysts comprised a substrate fabricated 116524~

from 310 stainless steel wire of diameter 0.010 inch, rolled down to ribbon 0.004 inch thick, a layer of alumina and a layer of one or more platinum group metal(s) at a loading of

2.46 mg/g of alumina. A portion of coated wire was cut from a catalyst and heated gradually raising the temperature together with particulate matter, collected from the exhaust gas stream of a diesel engine, in the sample pan of a differ-ential scanning colorimeter (a DSC) in an atmosphere of 1~
oxygen in argon. Samples of the atmosphere above the sample pan were taken via a heated capillary tube to a mass spec-trometer. Four mass numbers were traced: carbond monoxide (44), doubly charged argon (20), oxygen (32) and water (18) or nitrogen and carbon monoxide (28). The temperature at which the differential plot of the DSC peaked was taken to be the temperature at which combu~tion of the particulates took place. This temperature can be referred to as the "light-off" temperature. The results are given below:

Alumina Loading Light-off (g/g of wire)Catalytic metal(s)temperature (C) 0.33 5.7% Rh 94.3% Pt 235 0.28 67& Pt 33~ Pd 207 0.30 Pd 265 0.28 Pt 220 1~65Z47 The light-off temperature of particulates from the exhaust gas stream of a diesel engine, 207-265C, is considerably lower than the temperature for combustion to take place when no catalyst is present.
~ 5 Since the presence of a catalyst enables oxidation of - the smoke forming particles in a gas to take place at a lower temperature than the normal temperature at which com-bustion takes place, when it is desired to effect the cata-lytic oxidation of any smoke forming particles in the ex-haust gas from an internal combustion engine little or no heating is, consequently required. This is due to the fact that when a diesel engine is operated at medium to full power the temperature thereof i8 about 400C so that no preheating of the exhaust gas issuing from the engine is required before passing the said exhaust gas over a cata-lyst.
The filamentary metallic substrate may be in the form of wire and is disposed 80 as to provide maximum contact of the catalytic metal with the said exhaust gases. Preferably the wire is in a flattened form, usually obtained by rolling down prior to the deposition of washcoat and catalytic metal. In - the operation of a diesel or similar engine in which an excess of air or oxygen is present in the combustion chamber .

11~5247 such contact ensures that a substantial proportion of the pollutants as above described undergo catalytic oxidation.
A preferred disposition of the metallic wire substrate within the said chamber is such that turbulence is induced in the exiting gases.
According to a second aspect of the present invention a process for the reduction of pollution by exhaust gas from internal combustion engines comprises passing the said exhaust gas from the cylinders of the said engine into a chamber containing a catalyst on a support of design such that turbulence is produced and the pollutants present in the exhaust gas come into contact with the said catalyst and at least part of the said noxious components and parti-culates undergo catalytic oxidation. Preferably the said engine i8 a diesel engine.
Features of an internal combustion engine according -to the present invention include:
i) a chamber having an outerwall with a plural-ity of entry ports adjacent to the exhaust valves of the said enbing and an exit port adjacent to the exhaust pipe; and ii) a supported catalyst so positioned that the 1~L65247 exhaust gas flowing into the said chamber from the exhaust ports has to pass through the said catalyst which is so disposed such that the exhaust gas flow is turhulent at least while the said gas is in contact with the said catalyst.
Preferably the catalyst used in the said internal com-bustion engines comprise:
a) a divided substrate which is positioned in the path of the gas flow so as to create turbulence in the exhaust gas stream;
b) an adherent refractory metal oxide washcoat layer disposed upon the surface of the sub-strate; and c) a catalytic metal selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Fe, Co, Ni, V, Cr, Mo, W, Y, Ce, alloys thereof and intermetallic compounds containing at least 20% by weight of one or more of the said metals disposed upon the surface or through-out the refractory metal oxide washcoat layer.
The reEractory metal oxide washcoat layer preferably contains in the form of their oxides one or more members oE

'; ' ~65247 the group consisting of Mg, Ca, Sr, Ba, Sc, Y, the lanthan-ides, Ti, Zr, Hf, Th, Ta, V, Cr, Mn, Co, Ni, B, Al, Si and Sn.
A preferred washcoat material as A1203 and alumina hy-drates but stabilizing oxides such as BaO and oxides promoting catalytic activity such as Tio2, ZrO2, HfO2, ThO2, Cr2O3and NiO may also be present.
One preferred form of catalytic substrate comprises a structure made up from woven or knitted wire and an even more preferred form is woven or knitted wire which has been rolled down before fabrication into woven or knitted form. Suitable alloys which may be used in the manufacture of the wire are corrosion resistant and particularly oxidation resistant base metal alloys.
Examples of such base metal alloys are nickel and chrom-ium alloys having an aggregate Ni plus Cr content greater than 20% by weight and alloys of iron including at least one of the elements chromium (3-40) wt %, aluminum (1-10) wt %, cobalt (trace-5) wt ~, nickel (trace-72) wt ~ and carbon (trace-0.5) wt ~. Such substrates are described in German DOS 2450664.
Other example~ of base metal alloy~ capable o~ with-standing the rigorous conditions required are iron-aluminum-chromium alloys which may also contain yttrium. The latter ~165247 alloys may contain 0.5-12 wt % Al, 0.1-3.0 wt % Y, 0-20 wt % Cr and balance Fe. These are described in United States Patent No. 3298826. Another range of Fe-Cr-Al-Y alloys contain - 0.5-4 wt ~ Al, 0.5-3.0 wt % Y, 20.0-95 wt % Cr and balance Fe and these are described in United States Patent No. 3027252.
Alternatively the base metal alloys may have less - corrosion resistance, e.g. mild steel, but with a protective coating composition covering the surface of the substrate as described in Canadian Patent No. 1,128,031.

Where wire is used as a substrate its thickness is preferably between 0.001 and 0.02 inches thick and more preferably between 0.001 and 0.012 inches thick.
The invention is urther illustrated by the following specific embodiments described with reference to Figures 1 to 4 Of the drawings and by the following Examples, results from which are shown as graphs by the Figures 5 to 14 of the drawings.
In the drawings, Figure 1 shows a section through an apparatus suitable for use in combination with a diesel engine according to the invention, Figure 2 shows a section through an alternative apparatus, Figure 2a shows on a larger scale a section through a further alternative apparatus, Figure 3 shows in perspective an assembly of supporting bars suitable for acting as a central support in the apparatus, Figure 4 shows in perspective an alternative central support for the apparatus, Figures 5 to 9 show graphs of the composition of pollutants in exhaust gas discharging from a diesel engine ~ 9 _ 1 -~, ~' ,1 , ' ' , ' ' ., .
' 6S;~47 operated on an LA4 cold start cycle versus miles notionally travelled, Figures 10 to 14 show similar graphs to those of Figures 5 to 9 but obtained from a diesel engine operated on S an LA4 hot start cycle.
In one embodiment of the present invention the catalyst is contained in a reaction tube which is positioned substantially centrally in the exhaust chamber. The embodiment will be described with reference to Figure 1. The outer wall, 1, of the exhaust chamber has openings 7, 8, 9 and 10 which are adjacent to and continuous with the exhaust ports of the cylinders and one exit, 12, adjacent to exhaust pipe, 11. The reaction tube, 2, which is supported in the chamber by .

:~ ww.s . - 9a -, P~ r,~-' .

'. ' ~ . .. .. . .

struts 5 and 6 contains the supported catalyst 3. The reaction tube is so positioned that the exhaust gas on entering the exhaust chamber has to pass through the reaction - tube and so come into close and continuous contact with the catalyst before leaving the exhaust chamber and entering the exhaust pipe. Tile exhaust gas flow through the exhaust chamber is generally indicated by the labelled arrows Fl, l F2, F3, F4, F5 and F6. Combusted gas flows in frt~m the cylinder ports throllgh the openings 7, 8. 9 and 10 and flows along the reaction tube, 2, and out into the exhaust pipe, 11. A retaining bar, 4, is placed across the exit of the reaction tube to ensure that the catalyst remains in position.
~ he catalyst support is preferably oi knitted wire mesh. This may be ~abricated into a single monolith or it may be made up in annular sections.
'l~ne layer of washcoat and the catalytic layer may be applied to e;~ch section separately or after the sections have been linked together. Alternatively the support, in sections or linked together, may have the wa~hcoat and 1 catalytic leyer applied after it has beén pla~ed in the reaction tube.
A further embodiment will be described with reference to Figure 2. T~le outer wall, 21, o the catalyst chamber has , '' . . ' .

' ~:165Z47 openings 27, 28, 29 and 30, adjacent and continuous with the exhaust ports of the cylinders and one exit, 32, adjacent to the exhaust pipe, 31. The catalyst, 23, comprising a support, a washcoat layer and a catalytic metal is sc disposcd so that the exhaust gas on entering the catalyst chamber is compelled to pass through the interstices of the sald sacalyst before leaving the chamber and entering the exhaust pipe. The exhaust gas flows through the catalyst chamber as indicated by the labelled arrows, F41, F42, F43, F44 45 flows i~ from the exhaust ports as shown by F41, F42, F43 and F44 and then through the catalyst and out into the exit tube 22 as silown by F4s.
In this embodiment the support for the catalyst is preferabLy of knitted wire which may be made up into sections or as one unit but if it is in sections, e.g., of do4ghnut configuration, these are normaily lir.ked together before the support is placed in the chamber. One end of the support is closed off by joining, e.g., by -~7e1ding, a disc, 26, to it and an ann~lar disc, 25, at the other end holds the su~port in position. The supported catalyst is ~lisposed in the catalyst chamber as shown in Figure 2 by attaching the ends covered by the discs, 25 and 26, to the outer walls of the chamber.
.,j .
,. :

1~65Z47 To ensure that the support does not collapse inwards a cylindrical and perforated exit tube, 22, positioned in the catalyst chamber allows gas to pass through it and continue to the exhaust pipe, 31. The tube, 22, may be constructed of wire mesh or it may be a perforated metal tube having holes or slots.
Figure 3 depicts ~m alternative embodiment in which in place G~ a pérforated exit tube in the catalyst chamber a series of S rigid bars, 100-500, running the length of the chamber are used. These are mainta;ned in fixed spatial relationship to one another, thus holding the supported catalys~: rigidly in place within the chamber, by the use of spacing p~ates, 600. The spacing plates in pairs connect three of the five bars and are usually at right angles to each other thus being disposed along a diameter oE the central cylindrical exit tube. Two or ~ore pairs of spacing pla~es may be used and they are usually positioned at regùlar intervals in the lengtiL of the chamber. Alterna-tively the spacing plates may be used instead of rods where they would be continuous throughout th~ length of ~he chamber as shown in Figure 4. Rods and spacing plates need to be constructed of a material resistant to oxidation up to at least 800C.
, .

:. ....

- 1~65Z47 .

A further embodiment will be described with reference to Figure 2A in which, for convenience, only two exhaust ports are shown. The outer wall 100 of the catalyst chamber has openings, 101 and 102 adjacent to and continuous with the exhaust ports of the cylinders and one exit, 103, adja-cent to the exhaust pipe. The catalyst, 104, comprising a support, a washcoat layer and a catalytic metal is so dis-posed that the exhaust gas has to pass through the catalyst before leaving the chamber. The cataly~t is disposed in the chamber using spacing plates, 105, as described above. One end of the spacing plates, 109, is fixed to the chamber wall, 100, and a disc or metal plate, 108, is attached to the other end of the spacing plates to ensure that no exhaust gas can leave the chamber without passing through the cataly~t. The exhaust gas flows into the chamber through the openings, 101 and 102, and down through sleeves, 106 and 107, into the inner space 110 provided by the spac-"
ing plates, 105. The exhaust gas then flows through thecatalyst outwards and then through the exit, 103. The ~low of the exhaust gas i9 indicated by the labelled arrows Fg -Flo9-The support for the catalyst is preferably of knitted wire which may be made up into four sections or three units.

: .

:

. .

. .

1~65Z47 .., If the support is in sections, e.g., of doughnut configura-tion, these are normally linked together before the support is placed in the chamber.
le 1 ' .
The (2000 cc capacity) multicylinder engine of a com-mercially available diesel engine-powered automobile was modified to demonstrate the results obtained in operation of the pre~ent invention.
A catalyst chamber as outlined in the ~irst embodiment (Figure 1) of the invention, as described above, was itted to the engine. A knitted mesh catalyst support was made from , wire having the following composition:
% wt -Cr - 15 Al 4 Y 0.3 Fe ~alance Deposited on this support W&S a washcoat consisting of gamma alumina stabilized with 5% by weight BaO and a catalytic metal layer composed of platinum and palladium. The Pt/Pd loading was 2.5 g total (Pt:Pd ratio 1:1) on a total catalyst volume of 84 cubic inches. The results were obtained by , .

"

. .. , ,,, .. . ... ., . , .. , . . , ~ ., . . , 652~7 driving the automobile through the LA4 diesel cycle. Thehydrocarbons, carbon monoxide, nitrogen oxides and parti-culates present in the exhaust gas emissions were measured in g/mile. ~ase line measurements were first taken without a catalyst in the chamber but with back pressure adjusted to the same value as with the catalyst present. Results are given in Table 1:

Particulates ~IC g/mile ~ ~ /mile~mile Baseline figures 1.54 1.93 1.53 0.85 Modified engin2 0.214 1.892 0.9790.44 The back pressure was f~und to be high.
"
Example lA
Further experiment~ were carried out using the same catalyst as in Example 1 above. Baseline particulates eInissio~s using the same vehicle were determined in four tests as g/mile figur~s. These were expanded to includc thermogr~vimetric ~eterminations of the percentage carbon and volatiles contair.;d within the par~iculates and the g/mile sulphate contained wi.thin the particulatcs. The results obta~ned are shown as follows:
. . , . _. , --` 1165Z47 Baseline fi~ures Test No... Particulates % Carbon V/o Volatiles ~E~
~/mile . ~/mile 1 - 0.582 62.5 37.S ~.015 ' 2 0.512 58.0 42.0 0.011

3 0.509 , 59.6 40~4 0.012 ' 4 0.482 61.8 38.2 0.012 N _ : All above measurements cornpleted on a hot LA4 driving , cycle.
The full baseline emissions determined for '~C, CO ~nd ''~i NOx were also determined, the results being as follows:
, . . .
. Test No. ~ CO ~/mile NOx g/mile , 1 0.350 1.564 1.775 2 '0.339 1.529 1.803 :,, 3 0.354 1.5~1 1.786 ~ , A catalyst c~amber was des.gned wit,hin she constraints : available in the vehicle without any n.odification being m&de to the engine compartment layout. This resulted in a catalyst volume of 0.9 litres which was anticipated to be inadequate ¦ but upon which full tests were completed. The results of these are as follows:
' ~ .
..

~j .

.
.. . , ., ,,. . , . .. ., , . .. , , . ~ .. . . . .. .,,.. ~.. ..... .... .

Test No. Particulates % Car~ons % Volatiles Sulphate ~/mile /mile 1 0.494 79.4 20.60.036 2 0.441 76.4 23.60.037 3 0.444 75.3 24.70.Q35

4 0.515 67.3 32.70.055 ~ 0.466 63.4 3~.60.06 6 0.492 76.1 23.90 051 NOTE: The vehicle had completed 500 road miles prior to the first test and the entire period of testing was completed under simulated CitY driving conditions using the LA4 cycle.
Test results obtain-d for the HC, CO and NOx emissions were as follows:
i Test No. HC ~/mile CO g/mile NOx ~jmile 1 0.22~ 0.979 1.892 2 0.238 1.073 1.874 3 0.215 0.981 2.014 Example 2 ¦ A second catalyst chc~ ber as described in the second embodimel;t (Figure 2) was fitted onto the eng'le. A knitted mesh support made of the same wire as used in Example 1 again with a washcoat of gamma aiumina. The catalytic metal layer -` 1165247 :

comprises rhodium 7~ wt % and plàtinum 92~ wt %. The total catalyst volume was 110 cubic inches. The weight of support used was approximately 1.6 kg, 5 g of washcoat, alumina, and 2.9g of the catalytic metals Rh ~nd Pt in the above ratio wer~ applied to the support. Baseline measurements were taken with no ca~a_yst present in the chamber attached to the engine. The results are given below ir. Table 2 with the car being driven through the LA4 cycle with a hot start.

Particulates H~ ~/mile C0 g/mile NOx ~/mile ~/mile Baseline figures0 35 1.55 1.8 0.57 1 Modified engine 0.2 0.5 2.1 0.31 ¦ The back pressure without a catalyst present in the chamber was 2.4 inches of mercury and 3.5 inches of mercury with ,,.,~
catal~Jst pr~seLIt ~n the chamber. The C/H atomic ratio of the particulates present in the exh.~ust gas before and after passage through the catalyst chamber was measured an~ i.'3 given below in Table 3 with a hot st~rt for ~he engine.

- 1~65Z47 TAB-~ 3 C/H ratio of particulates present in the exhaust gas ~efore catal~st After catal~st i C 63 80 .. j - , .l This is a measure of the reduction in the crganic compound content of the e`xhaust gases. The concentration of sulphate ¦ present in the exhaust gases before and after the catalyst "~ was measured and found to be unchanged.
Further results obtained are given below in Table 4 ;¦ with a cold start for the e~lgine.

T~BLE 4 Particulates HC R/mile Ç0 ~/mile NOx~ile ~m.tle Basline figures 0.41 1.3 1.9 0.62 .Modifi~d engine 0.242 0.274 1.86 0.42 . Modified englne 0.218 0.252 1.86 0.4 The com?osition of the particulates present in the exhaust gas is given below in Tabie S with a cold st~rt for the engine.

; ,'.
~' ~'" ' ' ' ' ' ~ ~

"

.

Carbon Adsorbed HC's Sulphates g/mile g/mile g/mile Baseline figures 0.11 0.34 0.165 Modified engine 0.11 0.28 0.025 ; 5 The results in Table 2, 3, 4 and 5 were obtained using a commercially available diesel engine-powered automobile. The engine had been modified with a catalyst chamber in place as previously described. The automobile had completed 500 miles round a test circuit before being driven through the taxi cycle with a maximum speed of 25 mph.
Further tests were conducted using a commercially avail-able diesel engine powered automobile. A catalyst chamber as described in the second embodiment, as shown in Figure 2, was fitted into the engine. A support was made of 310 stainless steel wire of diameter 0.01 inch which wa~ flattened to 0.004 inch acro~s before being knitted. The support was coated with a washcoat of gamma alumina. The catalytic metal layer comprises rhodium 5.7~ and platinum 94.3~ with a loading o~
25 g/f~ . The weight of wire used was 3,200 g with 1,200 g of washcoat. The total volume of catalyst used was 217 cubic inches.
The weight of particulates present in the exhaust gas was measured by passing a known volume of exhaust through a -21~

`:
dilution tunnel where it was diluted with a set volume of air to prevent the solids settling before passing the gases through a filter pad. The weight of particulates enables a value for the particulates in g/hr to be calculated. The particulates present in the exhaust gas were analysed further " ~:
to give thermogravimetric weight, and the weight of volatile components, hydrocarbons, carbon and sulphate. Using the above ~ethod a number of filter pads were obtained for analysis.
The weight of sulphate in the particulates was measured by wet chemical analysis of the particulates. Another sample was placed in a thermogravimetric balance where the sample was heated in an inert atmosphere to a temperature of 780~
until the wei~ht was constant. The weight loss between the~
initial weight and the new gives the weight of volatile components present. Air was introduced and heating continued ~ntil the weight w~ again constant. The difference in this weight and the value for the previous constant weight gives the weight o.f carbon components present. The remainder was ash and non-combustible materials such as iron.
Baseline measurements weré taken with a ma.lifold connected to the engine in place of the chamber containing the catalyst.
Measurements were taken with the automobile driven through the ' ' . . .

... .

1~5247 .

LA4 cold start diesel cycle are given in Table 6 below, - LA4 hot start diesel cycle results are given in Table 7 below, and the Highway driving test results are given in Table 8 below. The Highway test used was the standard test cycle used in the US for fuel consumption trials.
The results given in Tables 6 and 7 are shown in graphical form in Figures 5-9, LA4 cycle cold start, and in Figures 10-14 for the LA4 cycle hot start. ~Baseline figures dotted line and modified engine continuous line.3 The reduction in particulate concentration (measured in g/mile) in an I C engine according to the present invention is shown in column 3. Reduction in adsorbed hydrocarbon~ and carbond present in the particulates are shown in columns 7 and 9 respectively. Sulphate figures show an increase in some ca~es but the absolute level of the emis~ion remains low.
Back pressure measurements were made. This is the difference in the pressure of the gases on leaving the exhaust ports and on leaving the chamber. The results are given in Table 9 for the automobile being driven through the LA4 cycle and in Table 10 for the Highway driving test.

1~5'~4~
.~ _ _ _ . ~
r ~~ ~ ~ ~ J ~ ~
~3~ LC
.N~ ld ~;t ~ u~ J ~J ~ ~ u~
,` ,~ ~ ~ ~ . ' I
~ ~ ~ u~ D ~ ~ O 1 .. , ~ IUI/~ oo ~ ~ ~ r~ ~ O ~ ~ O ~ ~ c~
1. ~ ~ c~ ~ ~ ~ ~ ~ c~ ;~ c~l NO~ ) . . . . . . . . . . . . . . .
o o o o o o o o o o o o o o o .
-.,~ , oo U~ ~ . I
~3N I`d~ I ~ ~ . ~ ~ u~
~19~.1N~ 1 oo ~ ~ oo 1 i~
~ , . I
~ ~ ~ O ~ oo ~ ~, SNOa~ 0~ ~ C`! ~ O ;l 1~ ~ O ;1--O~a~iH C~l O O O O O ~ O O C~l O O O C~ O
~j a~osa~ O O O O O O O O O O O O O O O .
~' . .
--'~ ~ C~ 1 a~
~/~1 ~ )N~ Ia ~ u~ ~ o u~ i ~ ~ _i ~ .
~' ~ a ' ~ $ + + + + + + ~ + ~
o,'' .
~ol . ~ ~ ~ ~ ' ~
~L11 CS~ l u~ tY~ l ~ C~
80 8 o o g ` o o o o ~o o o ~ ~o ~o vHa~ms O O O O O O O O O O O O O O O
, I
o u~ l a~
~a~ ~ o ~ D
~19~.1N~ I ~ u~ ~ ~ ~ ~ u~

~'~lW~ ~D ~ ~ O ~ ' c~l ~ ~ ~D ~ ~
. ~ oo ~ C5~ ~D ~ O ~ O
n~ 1 ~ ~ ~ ~ ~ ~ ~ ~
~,10.1.o o o o o o o o o o o o o o o ~ .~ rl ~ ~ . ~ ~ .~
. :~ 1 t~ ~ G 0 . ' . , . O 'O
S ~ I O o ~g ~1 ~ ~ ;t ~ O O g o O o l -Z- -.

, ._ ` _ _ ~ _ _ _ . .
~ I~ a~ ~ ~ ~ I~ I~ O ~ ~D
'~N~ Ia ~ oo ~i ~ u~ ~i o ;i ~D~ O
~ N~ a ~ ~ ~ ~ ~
:;, .
;~ C~l U~ .
`;t J ~ ~ ~ ~ ~ ~ o~ ~ r~ ~ ~9 ~o aTIw /~ ~ ~ 1 ~ ~ o . / ~ ~ ~ l NO~ ) o o o o o o o o o o o o o o o . '~
, . . .
~: ~ ~ ~ ~ u~ r~ I~
., ~?N~ I a ~ ;
~3~a 00 co 00 ,, . .
.
c~ u~ ~J ~ O~ .
. ' O ~ ~D ~ C`l O O 1~ 0 u~ O `D cr~
SNoa~
o aAH ~ o o o o o ~ o o ~ o o o ~ o ¢l a~osa~ o o- o o o o o o o o o o o o o ~! ~1 , ~ o i~ ~
, ~ )N:I~ldd~Ia ~ ~ o ,~
' ~ )YLN'd:)~Ida ~ + + + + ~ ~ ~ U~ , ~j .
;~, c~
1 O ~ D ~ _l ~ u~
I co ~g 1~ 1~ ~ u~ ~ C~l ~ cr o~ I~
~, O O O O O ~ ~ ~ ,~ ~ ~ ~ ~_, _, ~, ~ O O O O O O O O O O O O O O O
~a~n~ o O O O O O O O O O O O O O O

oo ~ O ~ _l d~ dI a ~, ~, 00 ~ Ln ~O O ~ ~ ~ Ln ll ~ J,Nd~ ad Ln ~ Ln ~o ~ ~ Ln u~ ~ n ~ ;~

~ ~ ~ ~ oo n _I ~t ~ ~ a~ ~ ~ oo ~l ~
~O _I ~ O _I O 00 ~ ~ C~J ~O 1~C~l 00 n~ a L~~ ~ Ln C~ ~ ~

~d~O~ o o' o o o o o o o o o o o o o , ~ ~ .~ ~ ~ a ~d ~ ~ ~
~ ~ ~ ~ o o o o o o o o o o o o o o o o o o o o o o o o o Ln n S~ I o c~ o~ o ~D ~ cs~ _I n ~ Ln O O ~D ~ ~ ~ ~ ;~ ~ n n ~ _I _ .. __ ___ _~z _ .

1~6S29t7 _ . ~ __ , ~ ~ _ _ _ ~

'~9N~ I Cl oo ~ u~ ~D
~ N~13~I~la l ~ ~ ~
. . , ~ ~ .' ,.
a~ _~
allw /~ ~ c~l o ~ ~D ~ ~D ~
NO~ ) o o o o o o o o ~ .
. o ~ U~ ~
, ,,.~ ~3N~ ... a . . . . .
'-'' ~ N~ a ~D ~O u~ u~ ,~
f~' ~D C~ ~ 1_ ~ ~ O 0~
~, sNoa~ 2 o ~ ~o ~ o ~ o ,~, -o~a~H o o o o o o o o ~i a~a~os~ ~
~;j ~D O. ~ L'~ ~ j ~I~)N~ I(1 ~ ~ ~
~9~N~3~ [ + $ + -t .
Sl C~ I~ ~D ~ _l .

~! i 3 ~ ~U1/~3O O O r~l O O O
i5~ ~ lRmS~O I 11 1l 1l ~NOI~ la ~ ~ O O
~19~N~13~1a.~ $ . _1 . ~ '.
I
~ ~ u~ ~ ~ ~O ~ c~J ~
oo ~9 u~
T~OI, o o o o o o o o _1 ~a _1 .1 ~ ,/j q~ ,Cj j ~

: ~ ~ ~ ~ ~ ~ ~ X ~ ~ ~ ~ .
o o S~ o~ o o~ 1n u~
o _l ~ ~ 00 0~ _1 ~

_5Z _ Back pressure in inches of mercury Miles covered Baseline After catalyst chamber ~ex. Avera~e Max. Average Hot Start 0 3.12 0.63 2.88 0.75 1,800 3.42 1.0 4,200 3.8 0.98 4,900 3.67 0.91

5,500 5.35 l.9

6,100 2.42 0.65 4.58 1.43 8,500 3.31 0.96 12,5~0 2.38 0.85 Cold Start 0 2.64 0.48 3.54 0.86 1,8~0 3.15 1.15 4,200 4.6 0.96 4,900 4.5 0.95 5,500 4.86 1.65 6,100 4.84* 0.61 ~.62 1.38 8,500 3.28 0.96 12,500 2.5 0.83 HiL figure probab1y ue to build up of soot deposits . . .. , . .. .., , ., .. .. , ... . , . .. . . . ., , ., --. .

TABLE 10 `
,~, ~ Back pressure in inches of mercury Miles covered Baseline After catalyst chamber Max. Avera~e Max. Average 1,800 3.34 1.98 - 6,100 2.0 1.1 4.05 2.9 8,S00 3.12 2.0 Back pressure in inches of mercury Miles covered Baseline After catalYst chamber Max. hvera~e Max. Avera~e 0 2.88 0.56 3.20 0.80 . , ,.
8,500 ~.48 0.61 '~.62 1.38 ' , ,, .
' .
, ' ' , 1 , , '~ ' .~' .

;SZ47 In the foregoing description the following abbreviationshave 4een used and their meanings are indicated.

CVS - constant volume sampling.

LA4 - Los Angeles Cycle as laid down by the Environmental Protection Agency (EPA) and the United States and is a standard test cycle devised to simulate a drive to work in Los Angeles traffic conditions. It is furthermore a test to which all new vehicles are subjected.

Taxi Cycle - A test cycle of about SO miles l~ng approved by EPA and carried out at low speeds up to 25 m.~.h. and includes periods when the cal is stationary and the engine is idling.

'

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A diesel engine comprising one or more cylinders which can generate exhaust gas containing carbon parti-cles when the engine is in operation, each cylinder having an exhaust port for discharging the exhaust gas, and an exhaust pipe for venting the exhaust gas to atmosphere and in combination with the engine an apparatus suitable for oxidising the carbon particles without the aid of electrical heating or the addition of air to the discharged exhaust gases wherein (a) the apparatus comprises a casing defining a chamber having at least one entry port in communi-cation with at least one of the cylinder exhaust ports and an exit port in communication with the exhaust pipe so that the exhaust gas can pass from the exhaust port through the chamber and into the exhaust pipe,.
(b) the chamber contains an interstitial catalyst system comprising a catalyst, a layer of refractory metal oxide and a support made from filamentary metallic material in a knitted or woven form, the catalyst being disposed on or throughout the layer of refractory metal oxide which in turn is disposed on the surface of the support, (c) the support is mounted with the chamber spaced from the casing so as to create an outer passageway, and is shaped so as to define a central passageway within the support (d) one of the passageways communicates with the entry port or ports and the other communicates with the exit port and the support is positioned so that all the exhaust gas discharged from the cylinder or cylinders is caused to pass through one passageway then through the interstitial catalyst system and then through the other passageway, (e) the outer and central passageways and the support are aligned relative to the entry port or ports such that exhaust gas passing through the chamber is caused to flow in a direction transverse of the entry port or ports during a portion of its passage through the chamber thereby increasing turbulence within the intersti tial catalyst system.

2. A combination according to claim 1 wherein the outer and central passageways and the support extend in a direction transverse of the entry port or ports whereby exhaust gas passing through the passageways flows in a direction transverse of the entry port or ports.

3. A combination according to claim 1 or claim 2 wherein the apparatus is disposed adjacent the cylinder exhaust port or ports.

4. A method for the reduction of pollution by carbon particles m exhaust gas discharging at a temperature of from 200°C to 400°C from a diesel engine wherein the method comprises passing the discharged exhaust gas through an apparatus as defined in claim 1 or claim 2.