FR2460388A1 - APPARATUS AND DEVICE FOR PURIFYING EXHAUST GASES - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS AN APPARATUS AND DEVICE FOR PURIFYING EXHAUST GASES. THIS APPLIANCE IS SUITABLE FOR A COMBUSTION ENGINE AND INCLUDES AN ENCLOSURE 1 DEFINING A CHAMBER CONTAINING A CATALYST 3 WHICH CATALYZER 3 INCLUDES A SUBSTRATE MADE OF A METALLIC MATERIAL IN THE FORM OF MESH FILAMENTS, WOVEN OR GRINDED OF A FIRST REFRACTORY METAL OXIDE BEING APPLIED TO THIS SUBSTRATE AND A SECOND LAYER OF CATALYTIC MATERIAL BEING APPLIED TO THIS FIRST LAYER, THIS CHAMBER INCLUDING AN INPUT 7, 8, 9, 10 IN COMMUNICATION WITH THE ENGINE EXHAUST PORT.

Description

The present invention relates to the reduction of smoke and other

  harmful constituents in gases and in particular exhaust gases or flue gases. and

  Gases from boilers / combustion engines

  They often contain finely divided particles of hydrocarbons and / or carbon or other solid matter that come out as smoke. Diesel engine smoke consists of solid / liquid particles (i.e., solid particles having an outer liquid coating layer), solid-chain aggregates, or spherical particles having a diameter between 100 and 8002. together are liquid sulphates, liquid hydrocarbons and gaseous hydrocarbons. The solid / liquid particles generally comprise carbon particles on which liquid hydrocarbons are adsorbed and the solid-chain aggregates are generally composed of high molecular weight organic compounds and

inorganic sulphates.

  White smoke is obtained when the engine first starts and results from the condensation of water vapor on the particles in the black exhaust

  so that a light fog is formed. The fumes / products

  Diesel engines are formed when the engine has warmed up and contains a relatively high proportion of carbon particles. In the blue fumes there

  has a little carbon but also a relative

  gaseous organic compounds such as aldehydes. About 90% of these smoke-forming particles have dimensions less than 1 micron, ie, one dimension of respirable parthules, and the maximum dimension of the remaining 10% of this smoke forms particles of

dimension less than 4 microns.

  An object of the invention is to at least reduce the amount of

  smoke gas in waste gases by catalytic oxidation of smoke particles

in these gases.

  A second object of the present invention is to reduce the amount of harmful gases and particles present in the

  exhaust gas from a combustion engine.

  Another object of the invention is to provide a diesel engine or gasoline engine modified so that a considerably smaller quantity is produced.

of gases and harmful particles.

  In this description, the expression "subject matter" is

  pollutant "should be considered as including hydrocarbons

  carbon monoxide and oxides of nitrogen formed by a combustion engine as well as particles

  forming the smoke described above.

  According to a first aspect of the invention, the combustion engine comprises an apparatus for reducing the pollutants found in the exhaust gas emitted by the engine comprising at least one discharge orifice, which apparatus comprises an enclosure defining a chamber containing a catalyst, the catalyst comprising a substrate made of filamentary wire mesh, woven or milled, a first layer of a refractory metal oxide applied to the substrate and a second layer of a catalyst applied to the first layer, the chamber having an inlet in communication with this exhaust port through which the exhaust gas emitted by the engine is brought into the chamber and passes through the catiaiseur before passing through the evacuation system

to the atmosphere.

  Usually the catalytic oxidation of the carbon particles occurs at 4000C while the normal combustion temperatures of such particles are at 700-8000C. For hydrocarbon particles, catalytic oxidation occurs at 2000C temperatures. The effect of a catalyst on the temperature at which oxidation

  of the particles entrained in the exhaust gas

  diesel engine occurs has been studied. Some

  number of catalyst samples were prepared.

  The catalysts included a substrate made from 0.25 mm stainless steel wire 310 laminated to a 0.10 mm thick ribbon, a layer of alumina and a layer of one or more metals of the group. platinum under a load of 2.46 m / g of alumina. Part of the coated wire 3- was cut from a catalyst and gradually heated by increasing the temperature together with the granular material, collected from the exhaust gas stream of a diesel engine in a sampling pan of a

  differential scanning colorimeter (DSC) in an atmosphere

  at 1% argon. Samples of the atmosphere

  above the sample cuvette were collected via a heated capillary tube in a mass spectrometer. Four mass numbers were found: carbon monoxide (44), doubly charged argon (20), oxygen

  (32) and water (18) or nitrogen and carbon monoxide (28).

  The temperature at which the differential point of the DSC indicated a maximum was taken as the temperature at which

  the combustion of particles occurred.

  erature may be referred to as the "ignition" temperature. The results are given below:

  Alumina load Catalytic metals Temperature dal-

  (g / g wire) lumage (OC) 0.33 5.7% Rh 94.3% Pt 235 0.28 67% Pt 33% Pd 207 0.30 Pd 265 0.28 Pt 220 The ignition temperature parthules of the exhaust gas stream of a diesel engine, 207-2650C, is considerably lower than the combustion temperature

  which occurs when no catalyst is present.

  Since the presence of a catalyst allows the oxidation of the particles forming the smoke of a gas to occur at a temperature lower than the normal temperature at which the combustion has Ibu, when it is desired to perform the oxidation catalytic of smoke-forming particles in the exhaust gas from a combustion engine, little or no heating is therefore required. This is because, when a diesel engine is running at medium power or full power, the temperature thereof is about 400 ° C so that no preheating of the exhaust gas leaving the

  engine is necessary for the passage of this exhaust gas.

on a catalyst.

  The filamentary metal substrate may be in the form of a wire and is arranged to form a contact

  maximum of the catalytic metal with these exhaust gases.

  Preferably, the wire is in flat form, usually obtained by rolling before deposition of the primer and catalytic metal. During operation of a diesel engine or similar engine or an excess of air or oxygen is present in the combustion chamber, such contact ensures that a substantial proportion of the pollutants described above

undergoes catalytic oxidation.

  A preferred arrangement of the wire substrate is

  that in this room is such that a turbulence is

  induced in the exhaust.

  According to a second aspect of the invention, a method for reducing the pollutants of the exhaust gases of a combustion engine consists in passing this exhaust gas from the scoops of this engine into a chamber containing a catalyst on a support of a model such that turbulence is produced and pollutants present in the exhaust gas coxlact with this catalyst and at least a portion of the constituents

  and harmful particles undergo catalytic oxidation.

  Preferably said engine is a diesel type engine.

  The characteristics of a combustion engine according to the present invention are: i) a chamber comprising an outer wall provided with a plurality of inlet ports adjacent to evacuation valves of these engines and a

  exhaust port adjacent to the outlet duct.

  and ii) a supported catalyst disposed such that exhaust gas passing into this chamber from the exhaust ports must pass through this catalyst which is arranged such that the exhaust stream be turbulent at least when this gas is contact

with this catalyst.

  Preferably, the catalyst used in this combustion engine comprises: a) a divided substrate which is disposed in the path of the gas stream so as to create turbulence in the exhaust gas stream. b) an adherent refractory metal oxide bottom layer disposed on the surface of the substrate, and

  (c) a catalytic metal selected from the group consisting

  Ru, Rh, Pd, Ir, Pt, Fe, Co, Ni, V, Cr, Mo, W, Y, -Ce, alloys thereof and intermetallic compounds comprising at least 20% by weight of a or more of these metals disposed on the surface or through the oxide base layer

refractory metal.

  The refractory metal oxide base layer preferably contains, in the form of their oxides, one or more elements of the group comprising Mg, Ca, Sr, Ba, Sc, Y, lanthanides, Ti, Zr, Hf, Th, Ta, V , Cr, Mn, Co, Ni,

B, Al, Si and Sn.

  A preferred basecoat material is Al 2 O 3 and alumina hydrates but stabilizing oxides such as BaO and oxides promoting catalytic activity such that TiO 2, ZrO 2, HfO 2, ThO 2, Cr 2 O 3 and NiO may be present.

to be present.

  A preferred embodiment of the catalyst substrate comprises a structure made from woven or mesh-like yarn and still more preferred is a woven or mesh-like yarn which has been rolled prior to manufacture into a woven or mesh form. . Suitable alloys which can be used for the manufacture of the wire are nonmetallic alloys

  valuable resistant to oxidation and corrosion.

  Examples of such alloys of non-precious metals are nickel and chromium alloys having an overall Ni plus Cr content greater than 20% by weight and iron alloys comprising at least one of the chromium elements (30 to 40% by weight ), aluminum (1 to 10% by weight), cobalt (trace at 5% by weight), nickel (trace at 72% by weight) and carbon (trace at 0.5% by weight). Such substrates are described in the publication of West Germany -6-

DOS 2450664.

  Other examples of non-precious metal alloys capable of withstanding the rigorous conditions required are feraluminium-chromium alloys which may also contain yttrium. These latter alloys can contain 0.5 to 12% by weight Al, 0.1 to 3% by weight Y, 0 to 20% by weight Cr and the complement Fe. These metals are described in US Patent No. 3298826. Another domain of Fe-CrAl-Y alloys contains 0.5 to 4% by weight Al, 0.5 to 3% by weightY, 20.0 to 95% by weight Cr and the balance is Fe and these alloys are described in the patent US number

3027252.

  Alternatively, alloys of non-precious metals may be less resistant to corrosion, for example mild steels, but they include

  protective coating composition covering the surface

  this of the substrate as it is described in the publication

of the United Kingdom number 2012317A.

  When wire is used as a substrate, it is preferred that its thickness is between 0.025 mm and 0.50 mm

  and still more preferably between 0.025 mm and 0.30 mm.

  According to one embodiment of the invention, the catalyst is in a reaction tube which is

  disposed substantially centrally in the evacuation chamber

  tion. The embodiment will be described with reference to FIG. 1. The outer wall 1 of the evacuator chamber comprises apertures 7, 8, 9 and 10 which are adjacent and continuous with the discharge ports of the cylinders.

  at an outlet 12 adjacent to the exhaust duct 11.

  The reaction tube 2 which is carried in the chamber by

  supports 5 and 6 contain the supported catalyst 3.

  The reaction tube is arranged in such a way that the exhaust gas entering the evacuation chamber must pass through the reaction tube and thus come into

  close and continuous contact with the catalyst before leaving

  remove the exhaust chamber and enter the exhaust pipe. The exhaust gas stream passing through

  through the evacuation chamber is usually

  sent by arrows F1, F2, F3, F4, F5 and F6. The flue gas stream from the cylinder outlets through the openings 7, 8, 9 and 10 passes along the reaction tube 2 and exits through the exhaust pipe 11. A retention line is located across the exhaust pipe 11. from the outlet of the reaction tube to ensure that the catalyst remains

in place.

  The support of the catalyst is preferably a metallized wire mesh structure. It can be manufactured in a single monolith or can be made in a sunscreen. The basecoat layer and the catalyst layer can be applied separately to each

  section or after the sections have been brought together

  corn. Alternatively, the support, in sections or assembb, may comprise a primer and a catalyst layer applied after it has been arranged.

in the reaction tube.

  Another embodiment is shown in FIG. 2. The outer wall 21 of the catalyst chamber has holes 27, 28, 29 and 30 adjacent and continuous with the cylinder discharge orifices and an outlet 32 adjacent to the exhaust pipe. 31. Catalyst 23 comprising a support, a base layer and a metal

  catalytic converter is arranged in such a way that the exhaust gas

  penetrating into the catalyst chamber is obliged to pass through the interstices of this catalyst before

  to leave the room and enter the escape pipe.

  ment. The exhaust gas passes through the catalyst chamber as shown by arrows F41, F42, F43, F44 and F45. The gas enters through the outlet openings F41, F42, F43 and F44 and then through the catalyst and exits as it enters the outlet tube 22.

shown in F45.

  In this mode of réalsation the support for the catalytic-

  it is preferably in the form of a section or a single unit, but if it is in section, for example a pet-of-nonne structure, it is normally connected to each other before the support is arranged in the room. One end of the support is closed for example by welding a disc -8 - 26 and an annular disc 25 at the other end maintint

  the support in place. The supported catalyst is available

  in the catalyst chamber, as can be seen in Figure 2 by fixing the ends covered by the discs 25 and 26 auKparois external chamber. To ensure that the support does not collapse inside, a cylindrical and perforated outlet tube 22 disposed in the catalyst chamber allows the gas to pass therethrough and extends to the exhaust pipe 31 The tube 22 may be made of a wire mesh or it may be a perforated metal tube comprising

openings or slits.

  Figure 3 describes yet another way of realizing

  o, instead of a perforated outlet tube in the catalyst chamber, a series of 5 rigid bars 100-500

  extending over the length of the chamber is used.

  These banes are maintained in relative relative spatial position with respect to each other, hence maintaining

  the supported catalyst rigidly in place in the chamber

  The spacer plates in the form of pairs connect three of the five baxes and are usually at right angles to one another, thus being disposed along a diameter of the tube. central cylindrical outlet. Two or more pairs of spacer plates may be used and are usually arranged at regular intervals along the length of the chamber. According to another

  Spacer plates can be used

  instead of the stems in such a way that they would be continuous through the length of the chamber as can be seen in Figure 4. Stems and plates

  spacing shall be made of

  aunt to oxidation at temperatures up to at least

800OC.

  Another embodiment is depicted in Figure 2A, where for practical reasons only two exhaust ports are shown. The outer wall of the catalytic chamber comprises apertures 101 with and adjacent 102 and extending the discharge ports of the cylinders and an outlet 103 adjacent to the exhaust pipe. The catalyst 104 comprising a support, a primer and a catalytic metal is arranged in such a way that the exhaust gas has to pass

  through the catalyst before leaving the room.

  The catalyst is disposed in the chamber using

  spacer plates 105 as described above.

  One end of the spacer plates 109 is attached to the wall of the chamber 100 and a disk or metal plate 108 is attached to the other end of the spacer plates to ensure that no exhaust can discharge the chamber without pass through the catalyst. The exhaust gas passes into the chamber through the openings 101 and 102 and then through the sleeves 106 and 107

  in the interior space 110 made by the plates of

  105. The exhaust gas then passes through

  catalyst outward and then through the outlet 103.

  The exhaust stream is indicated by the arrows

F90- F109.

  The support for the catalyst is preferably wire mesh which can be made in four sections or three units. If the support is in

  sections, for example a structure in farts-of-nuns, those

  ci are normally linked together before the support

is arranged in the room.

Example 1

  A 2000cc multicylinder engine of a commercially available diesel type was modified to demonstrate the results obtained by implementing

the present invention.

  A catalyst chamber teMeque that described

  in the first embodiment (Figure 1) of the invention

  described above has been adapted to the engine. A lattice catalyst support was made from a yarn having the following composition:% by weight Cr 15 Al 4 y 0, 3

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  % by weight Fe complement A base layer consisting of gamma-alumina stabilized with 5% by weight of BaO and a catalytic metal layer composed of platinum and palladium was deposited on this support. The Pt / Pd loading was 2.5 g total (Pt: Pd equals 1: 1) in a total catalyst volume of 1377 cm3. The results were obtained driving the automobile following the LA4 Diesel cycle. Hydrocarbons, carbon monoxide, nitrogen oxides and particulates in exhaust emissions are measured in g / km. Non-catalyst basic measurements were first made in the chamber but with a pressure adjusted to the same value as with the catalyst present. The results are given in the

table 1:

  Table 1 Particu HC g / km CO g / km NOx g / km g / km Base value 0.957 1, 199 0,950 0,528 Modified engine 0,133 1,175 0,608 0,273

  Secondary pressure was found to be high.

Example lA

  Other experiments have been implemented

  using the same catalyst as in Example 1 hereinafter

  above. Base particle emissions using the same vehicle were determined in four tests and values are given in g / km. These values have

  have been adjusted to include the thermo-

  gravimetrically the percentage of carbon and volatile matter in the particles and g / km of sulfate in the particles. The results obtained are as follows: Basic values Test No. Particles g / km% carbon% of material SulJ

4

  0.361 0.318 0.316 0.299 62.5 58.0 59.6 61.8 Eates volatile g / km

37.5 0.009

42.0 0.006

, 0.07

38.2 0.07

- 11 -

  Note: All the above measures completed according to a

LA4 hot cycle.

  The base emissions determined for hydrocarbons, CO and NOx were also determined and the results are as follows: Test NO. HC g / km CO g / km NOx g / km

1 0.217 0.972 1.103

2 0.210 0.950 1.120

3 0.220 0.970 1.109

  A catalytic chamber was made in accordance with the constraints imposed by the vehicles

  without further modifications to the engine compartments.

  This resulted in a catalyst volume of 0.9 liter

  what was expected to be insufficient, but we have

  dant makes complete tests. The results are as follows: Test No. Partbules% carbon% of material Sulfate g / km volatile g / km

1 0.307 79.4 20.6 0.0223

2 0.274 76.4 23.6 0.0229

3 0.275 75.3 24.7 0.0217

4 0.320 67.3 32.7 0.0341

0.289 63.4 36.6 0.039

6 0.305 76.1 23.9 0.031

  Note: The vehicle had completed 805 km before the first test and the entire test period was

  been completed under simul-

  in the city using the LA4 cycle.

  The results obtained for the hydrocarbon, CO and NOx emissions were as follows: Test No. HC g / km CO g / km NOx g / km

1 0.139 0.608 1.175

2 0.147 0.666 1.164

3 0,133 0,609 1,251

Example 2

  A second catalyst chamber as described in the second embodiment (Figure 2) was fitted to the engine. A bottom layer of gamma alumina was applied to a lattice support made

- 12 -

  with the same wire as used in Example 1. The catalytic metal layer comprises 7.5% by weight of rhodium and 92.5% by weight of platinum. The total catalyst volume was 1803 cm3. The pots of the support used were about 1.6 kg, 5 g of alumina layer and 2.9 g of metal catalyst Rh and Pt in the proportions

  above have been applied to the media.

  Basic measurements were taken with no catalyst

  present in the fixed chamber adapted to the engine. The results

  States are given below in Table 2, the vehicle

  being driven following the LA4 cycle with warm start.

  Table 2 Particles HC g / km CO g / km NOx g / km g / km Basis values 0.217 0, 963 1.118 0.354 Modified engine 0.124 0.310 1.305 0.192 The pressure without catalyst present in the chamber was 60.95 mm Hg and 88, 9 mmHg when the catalyst was in the chamber. The C / H atomic ratio of the particles present in the exhaust gas before and after passage through the catalyst chamber has been measured and is given below in FIG.

  Table 3 with a warm start of the engine.

Table 3

  C / H ratio of the particles present in the exhaust Before the catalyst After the catalyst

C 63 80

H 37 20

  This is a measure of the decrease in

  The concentration of sulphate present in the exhaust gases before and after the catalyst was measured and it was found that

she had not changed.

  Other results obtained are given below

  in table 4 with a cold engine start.

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TABLE 4

  HC g / km Values of 0.254 base Engine modi- 0.150 fie Engine modi- 0.135 fie CO g / km 0.807 0.170 0.156 Particles NOx g / km g / km

1,180 0,385

  1,155 1,155 0,261 0,248 The composition of the particles present in the exit gases is given below in

  with a cold start of the engine.

TABLE 5

  Sulphates g / km Carbon g / km Base value 0.068 0.211 Modified engine 0, 068 0.174 The results in the tables were obtained using a car

Table 5

  Hydrocarbons adsorbed g / km 0,102 0,015 2,3,4, and 5 with diesel engine available commercially. The engine had been modified by adapting a catalyst chamber such as that previously described. The car had traveled 805 km on a test circuit before being driven according to the said cycle

  It has a maximum speed of 40 kg / hour.

  Other tests have been implemented using a commercially available diesel engine autombile. A catalyst chamber as described

  in the second embodiment shown in FIG.

  re 2, has been adapted to the engine. A support was made of 310 stainless steel wire having a diameter of 0.2 mm and which had been applied up to 0.10 mm before making the mesh. A bottom layer of gamma alumina was applied to the support. The metal catalyst layer comprised 5.7% rhodium and 94.3% platinum with a feed of 892g / m3. The weight of the yarn used was 3200 g with 1200 g of primer. Total volume

of catalyst was 3646 cm3.

  The weight of the particles in the exhaust gas was measured by passing a known volume of exhaust gas through a dilution tunnel where it was diluted by a given volume of air to prevent the solids from settle before doing

- 14 -

  pass the gases through the filter. The weight of the particles makes it possible to calculate a value of these particles expressed in g / hr. Particles present in the exhaust gas were analyzed for heat-gravimetric weight and the weight of the volatile components hydrocarbons, carbon, and sulfate. Using the above method, a number of filter buffers were obtained for analysis. The sulfate weight in the particles was measured by wet chemical analysis of the particles. Another sample was

  placed in a thermogravimetric scale where the sample

  It was heated under an inert atmosphere to a temperature of 7800C until the weight remained constant. Weight loss between initial weight and

  new weight gives the weight of constituentsvolati] ..

  Air was introduced and continued to heat until the weight was again constant. The difference between this weight and the value of the previous constant weight gives the weight of the carbon components present. The rest was ash and non-combustible materials teh qie iron. Basic measurements have been made by connecting a manifold to an engine instead of the chamber containing

  the catalyst. Measurements were made with an automobile

  bile driving following the LA4 Diesel cycle with start-up

  cold and the values are given in Table 6 below.

  under, following the LA4 cycle with warm start and the values are given in Table 7 above and the results for tests on the highways are given in Table 8 below. The tests on highways

  performed were the standard tests used in the United States.

  United States for fuel consumption testing. The results given in Tables 6 and 7 are graphically represented in Figures -9, LA4 cycle with cold start and in Figures 14 for LA4 cycle with warm start. (Interrupted features for basic and continuous lines for the modified engine.)

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  The reduction of the concentration of the particles (expressed in g / km) by means of a combustion engine according to the invention is shown in column 3. The reduction of adsorbed hydrocarbons and carbon present in the

  particles is shown in columns 7 and 9 respectively.

  tively. The values for sulphate show an increase

  in some cases, but the absolute level of emissions

stay low.

  Pressure measurements have been made. They constitute

  kill the difference between the gas pressure in

  both the outlets and leaving the room. The results are given in Table 9 for a car driven according to the LA4 cycle and in Table 10 for

  driving test on the highway.

  TABLE 6 (LA4, cold start) Is st a H> a | t IÈ = g st l _.

0 0.395 0.0055 0.1492 0.2411

  Modified Oster 0.177 -55.0 0.0058 +44 0.0267 -82.1 0.1454 -39.7

  965 0.175 -55.5 0.0109 +95.6 0.0333 -77.6 0.11315 -45.4

  1930 0.211 -46.5 0.0075 +34.5 0.0448 -69.9 0.1589 -34.1

  2896 0.137 -65.3 0.0061 +10.4 0.0196 -86.6 0.1155 -53.7

  4827 0.195 -50.6 0.0144 +158.9 0.040 -72.8 0.1401 -41.9

  5792 0.259 -34.3 0.0410 +633.3 0.0822 -44.9 0.1364 -43.3

  6757 0.226 -42.8 0.0123 +121.1 0.0236 -84.2 0.1902 -21.1

  7884 0.173 -56.1 0.0062 +11.1 0.0324 -78.3 0.1377 -44.1

  8205 Values of 0.430 0.0160 0.1266 0.2873 basis 8849 Modified Motor 0.164 61.9 0.0086 -46.3 0.0302 -76; 1 0.11251 -56.4 Relative

  9815 0.196 -54.3 0.0233 +44.8 0.0420 -66.8 0.1310 -54.4

* 1367 0.190 -55.8 0.0094 -41.3 0.0272 -78.5 0.1535 -46.6

  20112 Value of 0,403 0,0143 0,1249 0,2635 base 20112 Engine 0,192 -52,4 0,0119 -16,9 0,0305 -75,6 0,1497 -43,2 modified

  L_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

  TABLE 7 (LA4 warm start) base. 0-4 Engine 0, 164 -53.8 0.0041 -17.7 0.0267 -81.3 0.133 -35.9 Relative

  965 0.133 -62.4 0.0046 -6.5 0.0224 -84, .3 0.1065 -48.7

  1930 0.147 -58.4 0.0045 -9.1 0.0226 -84.1 0.1206 -41.9

  2896 0.127 -64.2 0.0586 +17.7 0.0203 -85.7 0.1011 -51

  4827 0.193 -45.6 0.0217 +336.4 0.0377 -73.6 0.1377 -35.6

  5792 0.188 -46.9 0.0254 +411.2 0.0438 -69.3 0.1797 -42.3

  6757 0.175 -50.5 0.0142 +185.5 0.0169 -88.2 0.1488 -30.2

  7884 0.163 -54.0 0.0090 +82.0 0.0188 -86.8 0.1344 -34.7

  8205 Values of 0.340 0.0119 0.1215 0.2070 base 8849 Engine 0.141 -58.6 0, 0118 -1.0 0.0188 -84.5 0.101 -46.7 9815 modified 0.165 -51.5 0 , 0229 +91.7 0.016 -86.7 0.11261 -39.0

  13676 0.172 -49.3 0.0113 -5.7 0.018 -84.7 0.1499 -30.9

  20112 Values of 0.323 0.0102 0.129 0.1839 basis 20112 Modified 0.177 -45.1 0s0080 -21.2 0.0216 -83.3 0.1479 -19.6 0%> o o0

TABLE 8

  0 Values of 0.330 0.0105 0.1280 0.1920 base 2896 Engine mod-0.220 -33.3 0.0346 +229.6 0.0486 -62.0 0.1373 -28.5 relied 9815 Valeus 0.306 0 , 0109 0, 1052 0.190 base 9815 Motor mo- 0.558 + 82.1 0.080 +633.0 0.0141 -86.6 0, 4636 +143.8 1 dified H Co 13676 Valeuis 0.382 0.0177 0.1385 0, 2262 base 113676 Engine mo- 0.344 -10.1 0.0218 +23.2 0.0618 -55.5 0.260 +15.1 dif- fered 20112 Valeuis 0.388 0.0192 0.1430 0.2261 basis 20112 Engine modulated 0.231 -40.3 0.0261 +35.5 0.0609 -57.4 0.1441 -36.3 identi fi ed N) 0% as. co oe C4 (A Co

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TABLE 9

  Pressure in mm Hg km covered Basic values Max. Average after lysis Max.

the chamber of

Average warm start

79.24 16.00

61.46 16.51

Cold start

0 67.05 12.19

9815 122.9 * 15.49

* High value probably due

89.91 21.84

, 01 29.21

116.84 24.38

114.3 24.13

123.44 41.91

117.34 35.05

83.312 24.38

63.5 21.08

to a build up of soot.

o0 73.15 86.86 96.52 93.21, 89

116.33

  84.07, 45 19.05, 4 24.89 23.11 48.26 36.32 24.38 21.59

- 20 -

TABLE 10

  Pressure in mm Hg km covered Values of After catalytic chamber base Max. Average Max. Average

2896 84.83 50.29

9815 50.8 27.94 102.87 73.66

13676 79.24 50.8

TABLE 11

  Pressure in mm Hg km covered Values of After catalysis chamber base _ Max. Average Max. Average

73.15 14.22 81.28 20.32

13676 113.7 15.49 117.34 35.05

  In the foregoing description, the abbreviations

  The following statements have been used and their meanings are given below: CVS - constant volume LA4 sample - Los Angeles cycle filed by Environmnental Protection Agency (EPA) and the United States and is a standard test cycle designed to simulate driving in traffic conditions in Los Angeles. It is also a test that all

new vehicles are submitted.

  Taxi Cycle: - A test cycle of about 80 km accepted by the EPA and performed at a low speed of 40 km / h and includes periods when the vehicle is stopped

and that the engine runs idle.

  Naturally various modifications can be made by those skilled in the art to the engine and method which have just been described solely as examples.

  non-limiting without departing from the scope of the invention.

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Claims (18)

claims:   A combustion engine comprising an apparatus for reducing the pollutants in the exhaust gas emitted by the engine comprising at least one discharge orifice, characterized in that this apparatus comprises an enclosure defining a chamber containing a catalyst, the catalyst comprising a substrate made of a filamentary metallic material and made of woven or ground mesh, a first layer of refractory metal oxide applied to the substrate and a second layer of a catalyst applied to the first layer, this chamber comprising an inlet in communication with the discharge orifice through which the   exhaust gas emitted by the engine is brought into the chamber.   and pass through the catalyst before proceeding to   through the evacuation system to the atmosphere.   2. Motor according to claim 1, characterized in that this enclosure comprises a number of inputs   corresponding to the number of exhaust ports of the engine.   3. Motor according to any one of the claims   1 or 2, characterized in that this apparatus is arranged   adjacent to the exhaust vents of the engine.   4. Motor according to any one of the claims   1 to 3, characterized in that the metal substrate is arranged so as to establish a maximum contact between the   catalyst material and the exhaust gas.   5. Motor according to any one of the claims   1 to 4, characterized in that the catalyst material is a metal or a metal alloy or a composition   containing two or more metals and / or their oxides.   6. Engine according to claim 1, characterized in that the metal substrate is in the form of a ribbon with   at least two substantially flat opposed surfaces.   7. Motor according to claim 1, characterized in that the filamentary metallic material is in the form of of a thread.   8. Motor according to any one of the claims   1 to 7, characterized in that the metal substrate induces turbulence in the exhaust gases leaving the chamber - 22 -   9. Motor according to any one of the claims   1 to 8, characterized in that the refractory metal oxide layer is selected from the group consisting of: Mg, Ca, Sr, Ba, Sc, Y, lanthanides, Ti, Zr, Hf, Th, Ta, V, Cr, Mn, Co, Ni, B, Al, Si and Sn.   10. Engine according to claim 9, characterized in that the first layer is Al 2 O 3, alumina hydrates, BaO, TID 2, ZrO 2, HfO 2, ThO 2 or Cr 2 O 3.   11. Motor according to claim 1, characterized in that   the substrate is made of an alloy resistant to corro- containing a non-noble metal.   12. Motor according to claim 11, characterized in that the substrate is made of an alloy containing nickel and chromium having an overall nickel plus chromium content. greater than 20% by weight.   13. Motor according to claim 12, characterized in that the substrate is made of an iron alloy containing mokhs one of the elements: chromium (30 to 40% by weight), aluminum (1 to 10% by weight), cobalt (trace 5% by weight), nickel (trace at 72% by weight) and carbon (trace at 0.5% by weight). 14. Motor according to claim 13, characterized in that the non-noble metal alloy comprises yttrium in one amount of 0.1 to 3.0%.   15. Motor according to claim 1, characterized in that the substrate is made of a metallic material having   a thickness falling in the range of 0.02 to 0.05 cm.   16. Motor according to any one of claims 1 to 15,   characterized in that the catalyst material is a metal selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Fe, Co, Ni, V, Cr, Mo, W, Y, Ce, alloys containing at least one these metals and intermetallic compounds containing   at least 20% by weight of one or more of these metals.   17. Motor according to any one of claims 1 to 16,   characterized in that it functions> Wycle diesel combustion.   18. Process for reducing pollution by gas evacuation   combustion engines, characterized in that it consists of   to pass these exhaust gases from the cylinder - 23 -   of this engine in a chamber containing a catalyst on a support of a model such that a turbulence is obtained and pollutants in the exhaust gas come into contact with this catalyst and at least part of these harmful constituents and these harmful particles are undergoing catalytic oxidation.