FR2472604A1 - Leaded fuels for use in engines with catalytic converter - contg. reduced amt. of 1,2-di:chloroethane to suppress catalyst deactivation - Google Patents

Abstract

Petroleum (esp. gasoline) fuels for use in Ic engines equipped with a catalytic converter for exhaust gas purificn. contain a Pb cpd. and 0.1-0.8 (pref. 0.4-0.6) "theories" of 1,2-dichloroethane (DCE), where 1 "theory" is the amt. theoretically required to react with all of the Pb present to form a cpd. easily removed from the engine in the exhaust gas stream. Compared with the additive normally used (1 "theory" of DCE + 0.5 "theory" of 1,2-dibromoethane, DBE), the use of a reduced amt. of DCE decreases the rate of catalyst deactivation, esp. w.r.t. hydrocarbon conversion.

Description

 The present invention relates to a petroleum fuel for internal combustion engines and in particular for engines which have been fitted with a catalytic purification unit for the exhaust gas.

The petroleum fuel used in spark ignition internal combustion engines is classified according to its octane number, which is the volume percentage of trimethyl 2,2,4 pentane (iso octane) in a mixture of 2,2-trimethyl, 4 pentane and normal heptane which has the same detonating properties as the tested fuel. The detonation of an internal combustion engine is the characteristic metallic noise resulting from the detonations in series, that is to say the spontaneous combustion of the compressed charge before it is ignited by the spark. In an attempt to prevent detonation, anti-knock substances such as tetraethyl lead or tetramethyl lead have been added to the fuel
Other additives are often present in the fuel in addition to anti-knock substances to facilitate the removal of lead compounds from the vicinity of the cylinder and the valves and into the exhaust gas stream.

Two of these adjuvants are 1,2-dichloroethane (ethylene diamine dichloride) and 1,2-dibromoethane (ethylene dibromide). When a catalytic exhaust gas purification unit is disposed in the In the exhaust gas stream, an unleaded petrol fuel must be used to prevent poisoning of the catalyst such as platinum in the unit.

The present invention provides a petroleum fuel which contains a lead compound and an antidetomnt compound and a lead adjuvant and which will not be a poison for the platinum-containing catalyst exhaust gas purification unit, so3Lau. at least will poison this unit to a lesser degree and at a higher speed
slow.

In the countries of the European Community the level
proposed lead in petroleum fuel since
January 1981 is a maximum of 0.4 g / l and a minimum of 0.15 g / l. The amount of aplomb adjuvant present in the petroleum fuel is measured in theory. One theory is the amount of lead adjuvant that will theoretically react with the total amount of lead present to form a compound that is easily removed from the engine in the course of time. exhaust gas. The petroleum fuel used in the
UK currently normally contains a half-theory of dibromo 1,2 ethane and a theory of 1,2-dichloroethane as a lead adjuvant.

 According to an object of the present invention, the petroleum fuel suitable for internal combustion engines comprising a catalytic unit for purifying exhaust gas control comprises a lead compound and from 0.1 to 0.8 dichloromethane theories. 1,2 ethane. According to another aspect of the invention, a method of operating a spark ignition internal combustion engine comprising a catalytic exhaust purification unit containing a platinum group metal through BqueUe is employed. as the engine exhaust gas passes, the petroleum fuel used during engine operation contained gtramethyl lead or tetraethyl lead and 0.1 to 0.8 theories of 1,2-dichloroethane.

According to one embodiment, the exhaust gas purification unit comprises a monolith comprising a number of passages for the exhaust gas, a first layer of refractory material applied to the walls of these passages, and a second layer of a meti dlgroupe pitme called on this first layer. Preferably, the lead content of the fuel is between 0.15 to 0.4 g / l measured as the amount of lead, the lead being present in the form of one or more antiknock agents mentioned above. In the indicated area above 0 1 to 0.8 theories of 1,2-dichloroethane are particularly preferred 0.4 to 0.6 theories.To study the effects of exhaust gases from the combustion of a petroleum fuel containing lead compounds and self additives such as lead additives, tests were carried out on a catalyst using an installation for producing simulated exhaust gas from an internal combustion engine. The facility includes a modified flame reactor so that the fuel can be injected into the reactor, mixed
with air and with a propane gas pilot light in a conical double combustion chamber.

The catalyst may be disposed in one or two positions downstream of the combustion chamber. The fuel inlet is adjusted so that substantially stoichiometric combustion of the fuel occurs. A further addition of air, usually referred to as "secondary air", is added to the exhaust stream after the combustion chamber so that there is an excess of 0.5% oxygen present in the gas stream. exhaust when it passes over the catalyst. Nitrogen oxides were also added to the secondary stream so that there was a concentration of about 2000 ppm of nitrogen oxides in the exhaust gas stream.

 The duration of the test was 8 hours, the amounts of hydrocarbons and carbon monoxide present in the exhaust stream being measured, before and after the passage of the catalyst every hour. Before each test, the system was allowed to run for two hours using a non-active catalyst support set up to allow the reactor walls to equilibrate with the lead compounds present in the gas stream. 'exhaust.

 The catalyst support used was a cylindrical ceramic support with a cell density of 46.5 cells / cm 2, a length of 7.62 cm and a diameter of 5.08 cm. The catalytic metal used was platinum with a charge of 1.41 g / dm3. An intermediate layer of alumina was present between the support and the catalyst layer.

 In the first series of tests, a petroleum fuel containing 0.4 g / l of lead in the form of tetramethyl lead and a lead adjuvant in the form of dibromo-1,2-ethane present in the following amounts were used. theories, 1 theory, theory and zero. The inlet temperature was maintained at 6300C for all tests. The effect of the exhaust gases, obtained by combustion of such a petroleum fuel on the catalyst is shown in Figure 1 where the rate of loss of efficiency of the catalytic conversion is shown. for different exhaust gas compounds.

 In a second series of tests, a petroleum fuel containing 0.4 g / l of lead in the form of tetramethyl lead and a lead additive in the form of 1,2-dichloroethane were used in the amounts of 2 theories. , 1 theory, (theory, and zero.

The effect of the exhaust gas obtained by burning a petroleum fuel on the catalyst is shown in Figure 2 where the rate of loss of efficiency of the catalytic conversion is shown for different exhaust gas compounds.

 A comparison of the effect of the two adjuvants of lead, 1,2-dibromo ethane and 1,2-dichloroethane on the catalyst conversion yield is given in Figure 3 where the rate of yield loss of the catalytic transformation of methane is represented.

Another series of tests was carried out using a catalyst aged for 50 hours (aged on a British Leyland Dolomite engine of 1.8 liters) and these tests were carried out using a Marina type vehicle with Dolomite engine. 1.8 1 using the EEC -15 tests with the following results ::
% of transformation

<tb> HC <SEP> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HC <SEP><SEP> CO
<tb> 0.4g <SEP> / 1 <SEP> of <SEP> nlomh + <SEP> one <SEP> usual <SEP> mixture <SEP> for <SEP> 2.6 <SEP> 79.2
<tb> engine <SEP> of <SEP> lDCE <SEP><SEP> + <SEP><SEP> DBE <SEP> measured <SEP> in <SEP> theories
<tb> 0.4 <SEP> g <SEP> / 1 <SEP> + <SEP> + <SEP><SEP> Theory <SEP> DCE <SEP> 27.3 <SEP> 77.1
<Tb>
From the above results, it will be appreciated that improved performance is achieved particularly with respect to the removal of hydrogen when using a half-theory of a dichloroethane as compared to the usual motor mixtures. . Above the expression "EEC" means Economic Commission of Europe while "DCE" and DBE have the meanings mentioned previously in the description.

 The catalyst was a typical monolith of 62.0 cells per cm 2 refractory material 15.24 x 10.16 cm in diameter having a first layer of alumina bottoms with a charge of 0.06 g / dm 3 and a second layer of platinum catalyst with a charge of 1.41 g / dm3.

 Naturally, various modifications may be made by those skilled in the art to the products and processes which have just been described solely as non-limiting examples without departing from the scope of the invention.

Claims (11)

claims: An oil fuel for a combustion engine comprising an exhaust catalytic purification unit characterized in that it comprises a lead compound and 0.1 to 0.8 theories of 1,2-dichloroethane. 2. petroleum fuel according to claim 1, characterized in that the lead content of the fuel is in the range of 0.15 to 0.4 g per liter measured in amount of lead. 3. Fuel oil according to claim 2, charac terized in that the lead content of the fuel is present in the form of an anti-knock compound selected from the group comprising tetraethyl lead and tetramethyl lead. 4. Petroleum fuel according to any one of claims 1 to 3, characterized in that it contains 0.4 to 0.6 theories of 1,2-dichloroethane. 5. A method of operating a spark ignition combustion engine comprising a catalytic exhaust purification unit with platinum group catalyst, through which the exhaust gas from the engine is passed through. engine, characterized in that one uses a petroleum fuel containing a lead compound and 0.1 to 0.8 theories of 1,2-dichloroethane. 6. Method according to claim 5, characterized in that the lead content is in the range of 0.15 to 0.4 g / l measured in amount of lead. 7. Method according to any one of claims 5 or 6, characterized in that the lead content of the fuel is present in the form of an anti-knock compound selected from the group comprising tetraethyl lead and tetra methyl lead. 8. Method according to any one of the claims 5 t  6 or 7, characterized in that it contains 0.4 to 0.6 theory of 1,2-dichloroethane.  9. Method according to any one of claims 5 to 8, characterized in that the exhaust gas purification unit comprises a monolyth comprising a plurality of passages for the exhaust gas, a first layer of a refractory material. applied to the walls of these passages and a second layer of a platinum group metal applied to this first layer. 10. The method of claim 9, characterized in that the monolith is made of a ceramic material. 11. The method of claim 10, characterized in that the monolythe is made of a ceramic material having 62 cells per cm2 of cross section with a first layer of alumina and a second layer of platinum.