Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02482735 2004-09-28
Ej7607
METHOD FOR REDUCING COMBUSTION CHAMBER DEPOSIT FLAKING
The present invention is directed to a method of reducing combustion
chamber deposit flaking, and consequently, reducing cold start emissions. The
method includes combustion of a fuel having a fuel additive containing a
metallic compound. In one example, the metallic compound is a manganese-
containing compound.
Back rg ound
Spark ignited internal combustion engines (carbureted, port fuel injection
"PFI", multiple point injection "MPI", direct-injection gasoline "DIG", etc.)
accumulate combustion chamber deposits (CCD) during operation. This deposit
is a result of both inefficient combustion of the fuel during the power
stroke, and
thermal polymerization reactions of certain fuel components to give high
molecular weight material that does not burn very well. The deposit layers
both
on cylinder head surfaces inside the combustion chamber and on piston tops.
The piston top deposit in particular is fuel and moisture sensitive, and tends
to
curl and slough off when the deposit is fuel wetted and/or exposed to
moisture.
The symptoms of this flaking manifest themselves during cold start cranking
when the combustion charge blows the sloughed off deposit from the
combustion chamber and into the exhaust valve seats. The deposit flakes thus
lodged in this new location wedge in the sealing band of the exhaust valves
and
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prevent the tight sealing necessary to contain the fuel / air combustion
charge
during the compression stroke, thus inhibiting ignition and necessitating
extended engine cranking periods to dislodge the deposit so that the engine
can
fire up normally. During this cranking, instead of the combustion charge being
contained in the cylinder for the subsequent spark ignition, the combustion
charge is prematurely expelled into the exhaust system and loads the catalytic
converter with raw fuel. Some of this raw fuel escapes out of the exhaust
aftertreatment system and may contribute to cold start hydrocarbon "HC"
emissions. Also, when the engine does finally fire up, the subsequent hot
combustion gases ignite this raw fuel. The ensuing vigorous combustion of raw
fuel in the exhaust system may melt the catalytic converter due to the -
excessively high temperatures generated by this burn, and seriously damage the
exhaust aftertreatment system.
The symptoms of CCD flaking have only recently been observed with the
advent of advanced emissions control strategies aimed at lowering hydrocarbon
emissions at cold start. The reasons for all these changes resulted from the
discovery that a significant portion of total vehicular hydrocarbon emissions
were generated during the initial 90 seconds it takes conventional, under the
floor three-way catalytic converters to light off during cold start.
Therefore,
shortening this time interval became of paramount importance. Government
environmental regulators also recognized this fact and mandated that vehicle
manufacturers develop an on board diagnostic system (OBD) to monitor the
emissions control system in a manner that would minimize hydrocarbon
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emissions to the environment, and this system be under warranty to ensure
that it performed its intended task for the duration of the specified warranty
period.
The emission control changes being made have resulted in cold start
difficulties ascribed to the higher fueling rates during cold start causing
combustion chamber deposits to flake off and become lodged in the exhaust
valve sealing band area, thereby preventing a good seal during compression
and hence leading to misfires. The OBD system detects this immediately
because of the subsequent elevated hydrocarbon emissions due to unburned
fuel, and illuminates the malfunction indicator light {MIL) on the dashboard,
necessitating a visit to the dealership for corrective .repairs. Cold start
difficulties due to CCD flaking tend to occur mainly in higher displacement
engines with more cylinders {6, 8, and 10 cylinder engines] because in these
bigger engines the cranking rate is lower, and it takes longer to blow the
flaked
deposits away from the exhaust valves.
One way to deal with the cold start problem caused by CCD flaking is to
not drive the vehicle a short distance under light load, thereby leaving the
chamber to soak for extended periods of time. Another way to get around this
problem is to simply continue cranking to blow away the offending deposit
flakes, and on start up, rev up the engine for an additional thirty seconds to
clean out the rest of the flaking deposit. However, this method inadvertantly
leads to very high levels of hydrocarbon emissions and may cause the OBD MIL
to illuminate.
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CA 02482735 2004-09-28
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Description
Combustion chamber deposit (CCD) flaking has been discovered to be
reduced and even eliminated with the use of a fuel additive containing a
metallic compound. In one example, a manganese-containing compound,
MMT, completely suppresses CCD flaking.
A method of reducing combustion chamber deposit flaking in spark
ignited internal combustion engines that experience combustion chamber
deposits comprises the steps of supplying a fuel comprising an additive that
included a. metal-containing compound to a spark ignited internal combustion
engine, wherein the metal-containing compound is supplied in an amount
effective to reduce combustion chamber deposit flaking.
The metal-containing compound may be a compound containing one or
more of the following metals: manganese, platinum, palladium, rhodium, iron,
cerium, copper, nickel, silver, cobalt and molybdenum, and mixtures thereof.
An example of a manganese compound is described in detail herein, but other
metal-containing additives may be used. In each alternative, the metal
compound in the fuel is combusted in a spark ignited internal combustion
engine. Use of the metal - containing additive reduces or eliminates CCD
flaking.
The fuels and additives herein are adapted to be combusted in any spark
ignited internal combustion engine. Specific engines that will benefit include
those having carbureted systems, port fuel injection systems, mufti point
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injection systems, and direct injection gasoline systems. Also, turbocharged
and supercharged versions of the foregoing will benefit. Other engines having
advanced emissions controls, including for example exhaust gas recirculation,
will benefit. Additionally, Otto cycle and two-stroke internal combustion
engines will benefit.
The nonleaded or unleaded gasoline bases in the present fuel
composition are conventional motor fuel distillates boiling in the general
range
of about 70°F to 440°F. They include substantially all grades of
unleaded
gasoline presently being employed in spark ignition internal combustion
engines. Generally they contain both straight runs and cracked stock, with or
without alkylated hydrocarbons, reformed hydrocarbons and the like. Such
gasolines can be prepared from saturated hydrocarbons, e.g., straight stocks,
alkylation products and the like, with detergents, antioxidants, dispersants,
metal deactivators, rust inhibitors, mufti-functional additives, demulsifiers,
fluidizer oils, anti-icing, combustion catalysts, corrosion inhibitors,
emulsifiers,
surfactants, solvents or other similar and known additives. It is contemplated
that in certain circumstances these additives may be included in
concentrations above normal levels.
Generally, the base gasoline will be a blend of ;stocks obtained from
several refinery processes. The final blend may also contain hydrocarbons
made by other procedures such as alkylates made by the reaction of C4
olefins and butanes using an acid catalyst such as sulfuric acid ar
hydrofluoric
acid, and aromatics made from a reformer.
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The motor gasoline bases used in formulating the fuel blends of this
invention generally have initial boiling points ranging from about 70°F
to about
100°F and final boiling points ranging from about 420°F to about
440°F as
measured by the standard ASTM distillation procedure (ASTM D-86).
Intermediate gasoline fractions boil away at temperatures within these
extremes.
It is also desirable to utilize base gasolines having a low sulfur content as
the oxides of sulfur tend to contribute to the irritating and choking
characteristics of smog and other forms of atmospheric pollution. To the
extent
it is economically feasibie, the base gasolines should contain not more than
about 100 ppm of sulfur in the form of conventional sulfur-containing
impurities. Another alternative includes fuels in which the sulfur content is
no
more than about 30 ppm.
The gasoline bases which this invention employs should be lead-free or
substantially lead-free. However, the gasoline may contain antiknock
quantities
of other agents such as cyclopentadienyl nickel nitrosyl, N-methyl aniline,
and
the like. Antiknock promoters such as 2.4 pentanedione may also be included.
On certain occasions it will be desirable for the gasoline to contain
supplemental valve and valve seat recession protectants. Nonlimiting examples
include; boron oxides, bismuth oxides, ceramic bonded CaF. sub.2, iron
phosphate, tricresylphosphate, phosphorus and sodium based additives and
the like. The fuel may further contain antioxidants such as 2,6 di-tert-
butylephenol, 2,6-di-tert-buyl-p-cresol, phenylenedia~mines such as N-Nl
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-di-sec-butyl-p-pheylenediamine, N-isopropylphenylenediamine, and the like.
Likewise, the gasoline may contain dyes, metal deactivators, or other
additives
recognized to serve some useful purpose. The descriptive characteristics of
one
common base gasoline is given as follows. Obviously many other standard and
specialized gasolines can be used in Applicants' fuel blend.
CHARACTERISTICS OF GASOLINES
API Gravity (@ 60 50 - 70
F)
Reid Vapor Pressure, 6 - 8
EPA, (psi)
Sulfur (ppm) 0 - 500
Research Octane 85 - 120
Motor Octane 75 - 90
R+M/2 87-II0
Oxygenates (%) 0 - 30
Aromatics {%) 0 - 50
Olefins {%) 0 - 30
Paraffins (%) 30 -- 100
ASTM Distillation
Vol % EvaQorate Temp., F.
IBP 70 - 100
100 - 130
120- I40
140 - 160
150 - i 70
170 - 190
190 - 210
200 - 220
220 - 240
240 - 260
280 - 300
340 - 370
3 80 - 400
EP 420 - 440
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One metal that may be used includes elemental and ionic manganese,
precursors thereof, and mixtures of metal compounds including manganese.
These manganese compounds rnay be either inorganic or organic. Also
effective is the generation, liberation or production in situ of manganese or
manganese ions.
Inorganic metallic compounds in an example can include by example and
without limitation fluorides, chlorides, bromides, iodides, oxides, nitrates,
sulfates, phosphates, nitrides, hydrides, hydroxides, carbonates and mixtures
thereof. Metal sulfates and phosphates will be operative and may, in certain
fuels and combustion applications, not present unacceptable additional sulfur
and phosphorus combustion byproducts. Organometallic compounds in an
example include alcohols, aldehydes, ketones, esters, anhydrides, sulfonates,
phosphonates, chelates, phenates, crown ethers, carboxylic acids, amides,
acetyl acetonates, and mixtures thereof.
Exemplary manganese containing organometallic compounds are
manganese tricarbonyl compounds. Such compounds a.re taught, fox example,
in US Patent Nos. 4,568,357; 4,674,447; 5,113,803; 5,599,357; 5,944,858 and
European Patent No. 466 512 B 1.
Suitable manganese tricarbonyl compounds which can be used include
cyclopentadienyl manganese tricarbonyl, methylcyclopentadienyl manganese
tricarbonyl, dimethylcyclopentadienyl manganese tricarbonyl,
trimethylcyclopentadienyl manganese tricarbonyl, tetramethylcyclopentadienyl
manganese tricarbonyl, pentamethylcyclopentadienyl manganese tricarbonyl,
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ethylcyclopentadienyl manganese tricarbonyl, diethylcyclopentadienyl
manganese tricarbonyl, propylcyclopentadienyl manganese tricarbonyl,
isopropylcyelopentadienyl manganese tricarbonyl, tart-butylcyclopentadienyl
manganese tricarbonyl, octylcyclopentadienyl manganese triearbonyl,
dodecylcycIopentadienyl manganese tricarbonyl, ethylmethylcyclopentadienyl
manganese tricarbonyl, indenyl manganese tricarbonyl, and the like, including
mixtures of two or more such compounds. In one alternative are the
cyclopentadienyl manganese tricarbonyls which are liquid at room
temperature such as methylcyclopentadienyl manganese tricarbonyl,
ethyicyclopentadienyl manganese tricarbonyl, liquid mixtures of
cyclopentadienyl manganese tricarbonyl and methylcyclopentadienyl
manganese tricarbonyl, mixtures of methylcyciopentadienyl manganese
tricarbonyl and ethylcyclopentadienyl manganese tr~icarbonyl, etc.
Preparation of such compounds is described in the literature, for
example, U.S. Pat. No. 2,818,417.
When formulating additives to be used in the methods herein, the metal-
containing compound must be employed in amounts sufficient to reduce or
eliminate CCD flaking in the spark ignited internal <:ombustion engine. The
amounts will vary according to the particular metal or mixture of metals and
metal-containing compounds. In the example of a manganese-containing
compound, the amount of manganese added can be about 1 to about 5~ mg
manganese per liter.
CA 02482735 2005-O1-05
The metal-containing compounds are believed to act as both a free
radical sink and a combustion catalyst. As a radical sink, the compounds may
be inhibiting radical initiated fuel polymerization reactions hence limiting
contribution to hydrocarbonaceous CCD by this route. As a combustion catalyst,
the manganese, for instance, catalytiically participates in the CCD removal
mechanism by promoting carbon oxidation at lower temperatures.
The term "cold start emissions" refers to and its defined herein in
accordance with the industry definition. The industry recognized definition of
cold-start emissions can be found in the FTP-75 (F~°deral Test
Procedure).
Details of the test procedure are described in the Code of Federal Regulations
(CFR 40, Part 86). Briefly, the test procedure consists of the following three
phases: 1) Cold-start, 2) Transient, and 3) Hot-start. The FTP-75 emissions
cycle simulates 11.04 miles ( 17.77 km) distance of travel in a time of 1874
seconds at an average speed of 21.2 mph (34.1 km,/h). Before the test, the
vehicle is conditioned overnight at 25 +/- 5 C to as:~ure cold start
conditions.
The cold start is initiated followed by the transient phase. Then the vehicle
is
shut down for a hot soak of 10 minutes before being restarted to perform the
hot phase. The emissions from each phase are collected in a separate Teflon
bag for each test phase, and analyzed. Quantities of each emission component
(HC, CO, COa, NOX, etc) are expressed in g/mile (g/km) for each phase. For
hydrocarbon emissions (HC) the cold-start phase is the most important
because it contributes 80 - 90% of the total from th.e three phases.
*Trade-mark
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Exam-pies
Fuels that included and did not include a metal-containing compound
were compared in an engine test. Manganese in MMT~ was the additive used at
a treat rate 8.25 mg. of manganese per liter of fuel.
The vehicle used in this study was a Dodge: Intrepid*with a six cylinder
engine. It was operated for 3000 miles on the test cycle while fueled with non
additized CITGO RUL gasoline. At the end of the test the engine was dismantled
and rated for CCD flaking according to a procedure adapted from that published
by Gautam T. Kalghatgi in the SAE Paper Series 2002-O1-2833.
Test Procedure: CCD F lakin~ Test on the Dodge Intrepid
Ethyl Test Outline:
Vehicle: Chrysler Dodge Intrepid
Fuel: CITGO Regular Unleaded
Test # Without MMT Additive
1:
Test # With MMT Additive
2:
Cycle: IVD Chassis Dyno Cycle (Average 45
mph)
Two shifts per day (about 600 miles)
Soak overnight
End test at a cumulative 3000 miles:
At End of Test:
1. Dismantle engine as per regular IVD/CCD test
2. Measure deposit thickness on both the head and pistons using
the template
3. Spray piston tops with soap water ( T. drop of liquid household
detergent per 100 mL water) using a. house plant water sprayer
4. After 3 hours photograph piston tops and note extent of flaking
*Trade-mark
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5. Spray piston tops again and leave overnight.
6. Photograph piston tops and note extend of flaking
7. Remove flaked deposit by vacuum and weigh
8. Photograph piston tops
9. Measure thickness of remaining deposit using the template
10. Scrape and total piston top deposit
11. Complete IVD and CCD determination on head.
By the term "average" it is meant the average of deposit amounts on the
six valves or the six piston tops, or the six cylinder head locations
corresponding to the six pistons.
Table 1: The Manganese Containing Additive Inhibited CCD Flaking
Additive Flaked AmountTotal Engine Engine IVD
of CCD
CCD milli milli ams milli ams
ams
No 89.4 '783.4 312.2
Yes 0 688.9 305.9
As is evident from this test example, the 'use of the specific metal-
containing additive noted completely eliminated flaking of combustion chamber
deposits. In other words, no CCD flaked off when the additive was used. Other
metal-containing additives may be used, and the treat rate of any additive may
be varied. By changing the selection of additive and/or the treat rate of the
additive, the amount of reduction in flaking rnay be controlled. It is
believed
that, in the case of a manganese-containing additive, a treat rate of about
two
mg. of manganese per liter of fuel will achieve up to about a 50% reduction in
CCD flaking.
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Given the discovered absence of CCD flaking, i.t should be evident that a
more complete combustion occurs, especially during the cold start period of
engine operation. There were no flakes to block the sealing of the exhaust
valves. Therefore, less raw fuel is allowed to pass through the cylinder and
into
the exhaust system. Accordingly, cold start emissions of hydrocarbons should
be reduced by use of the additive in spark ignited internal combustion engines
that experience combustion chamber deposits.
It is to be understood that the reactants and components referred to by
chemical name anywhere in the specification or claims hereof, whether referred
to in the singular or plural, are identified as they exist prior to coming
into
contact with another substance referred to by chemical name or chemical type
(e.g., base fuel, solvent, etc.). It matters not what chemical changes,
transformations and/or reactions, if any, take place in the resulting mixture
or
solution or reaction medium as such changes, transformations and/or
reactions are the natural result of bringing the specified reactants and/or
components together under the conditions called for pursuant to this
disclosure. Thus the reactants and components are identified as ingredients to
be brought together either in performing a desired chemical reaction (such as
formation of the organometallic compound) or in forming a desired composition
(such as an additive concentrate or additized fuel blend). It will also be
recognized that the additive components can be added or blended into or with
the base fuels individually per se and/or as components used in forming
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preformed additive combinations and/or sub-combinations. Accordingly, even
though the claims hereinafter may refer to substances, components and/or
ingredients in the present tense ("comprises", "is", etc.), the reference is
to the
substance, components or ingredient as it existed at the time just before it
was
first blended or mixed with one or more other substances, components and/or
ingredients in accordance with the present disclosure. The fact that the
substance, components or ingredient may have lost its original identity
through
a chemical reaction or transformation during the <:ourse of such blending or
mixing operations or immediately thereafter is thus wholly immaterial for an
accurate understanding and appreciation of this disclosure and the claims
thereof.
This invention is susceptible to considerable variation in its practice.
Therefore the foregoing description is not intended', to limit, and should not
be
construed as limiting, the invention to the particular exemplifications
presented hereinabove. Rather, what is intended 1to be covered is as set forth
in the ensuing claims and the equivalents thereof permitted as a matter of
law.
Patentee does not intend to dedicate any disclosed embodiments to the
public, and to the extent any disclosed modifications or alterations may not
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literally fall within the scope of the claims, they are considered to be part
of the
invention under the doctrine of equivalents.
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