Field of the Invention
-
The present invention relates to the use of a fuel additive for protecting
and improving operation of combustion exhaust after treatment systems. The
additive contains one or more manganese compounds. The additive can be
introduced into a combustion chamber as part of the fuel, or it may be injected
alone or with the fuel into the combustion exhaust. The additive will then
enhance the operation of after treatment systems including, for example, those
that incorporate catalyzed and continuously regenerating technology diesel
particulate filters.
Description of the Prior Art
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It is well known in the automobile industry, or any industry where
hydrocarbonaceous fuels are burned, to reduce tailpipe (or smokestack)
emissions by using various strategies. For example, the most common method
for reducing emissions from spark ignition engines is by careful control of the
air-fuel ratio and ignition timing. Retarding ignition timing from the best
efficiency setting reduces HC and NOx emissions, while excessive retard of
ignition increases the output of CO and HC. Increasing engine speed reduces
HC emissions, but NOx emissions increase with load. Increasing coolant
temperature tends to reduce HC emissions, but this results in an increase in
NOx emissions.
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It is also known that treating the effluent stream from a combustion
process by exhaust after treatment can lower emissions. The effluent contains
a wide variety of chemical species and compounds, some of which may be
converted by a catalyst into other compounds or species. For example, it is
known to provide exhaust after treatment using a three-way catalyst and a lean
NOx trap. Other catalytic and non-catalytic methods are also known.
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Thermal reactors are noncatalytic devices which rely on homogeneous
bulk gas reactions to oxidize CO and HC. However, in thermal reactors, NOx is
largely unaffected. Reactions are enhanced by increasing exhaust temperature
(e.g. by a reduced compression ratio or retarded timing) or by increasing
exhaust combustibles (rich mixtures). Typically, temperatures of 1500 °F (800
°C) or more are required for peak efficiency. Usually, the engine is run rich to
give 1 percent CO and air is injected into the exhaust. Thermal reactors are
seldom used, as the required setting dramatically reduces fuel efficiency.
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Catalytic systems are capable of reducing NOx as well as oxidizing CO
and HC. However, a reducing environment for NOx treatment is required which
necessitates a richer than chemically correct engine air-fuel ratio. A two-bed
converter may be used in which air is injected into the second stage to oxidize
CO and HC. While efficient, this procedure results in lower fuel economy.
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Single stage, three way catalysts (TWC's) are widely used, but they
require extremely precise fuel control to be effective. Only in the close
proximity of the stoichiometric ratio is the efficiency high for all three
pollutants, excursions to either side of stoichiometric can cause increases in
hydrocarbon and carbon monoxide or NOx emissions. Such TWC systems can
employ, for example, either a zirconia or titanium oxide exhaust oxygen sensor
or other type of exhaust sensor and a feedback electronic controls system to
maintain the required air-fuel ratio near stoichiometric.
-
Catalyst support beds may be pellet or honeycomb (e.g. monolithic).
Suitable reducing materials include ruthenium and rhodium, while oxidizing
materials include cerium, platinum and palladium.
-
Diesel systems raise a different set of challenges for emissions control.
Strategies for reducing particulate and HC include optimizing fuel injection and
air motion, effective fuel atomization at varying loads, control of timing of fuel
injection, minimization of parasitic losses in combustion chambers, low sac
volume or valve cover orifice nozzles for direct injection, reducing lubrication oil
contributions, and rapid engine warm-up.
-
In terms of after treatment, it is known that diesel engines generally burn
lean and the exhaust will therefore usually contain excess oxygen. Thus, NOx
reduction with conventional three-way catalysts is not feasible. NOx is removed
from diesel exhaust by either selective catalytic reduction, the use of lean NOx
catalysts such as those comprised of zeolitic catalysts or using metals such as
iridium, or catalyzed thermal decomposition of NO into O2 and N2.
-
Diesel particulate traps such as catalyzed diesel particulate filters (C-DPFs)
and continuously regenerating technology diesel particulate filters (CRT-DPFs)
have been developed which employ ceramic or metal filters. Thermal
and catalytic regeneration can burn out the material stored. New particulate
standards currently under review may necessitate such traps. Fuel
composition, including sulfur and aromatic content, and the burning of
lubricant can contribute to increased particulate emissions. Catalysts have
been developed for diesels which are very effective in oxidizing the organic
portion of the particulate.
-
Improved fuel economy can be obtained by using a lean-bum gasoline
engine, for example, a direct injection gasoline engine, however currently NOx
cannot be reduced effectively from oxidizing exhaust using a typical three-way
catalyst because the high levels of oxygen suppress the necessary reducing
reactions. Without a NOx adsorber or lean NOx trap (LNT), the superior fuel
economy of the lean-burn gasoline engine cannot be exploited. The function of
the LNT is to scavenge the NOx from the exhaust, retaining it for reduction at
some later time. Periodically, the LNT must be regenerated by reducing the
NOx. This can be accomplished by operating the engine under rich air-fuel
ratios for the purpose of purging the trap. This change in operating conditions
can adversely effect fuel economy as well as driveability. These LNT's may also
be placed on diesel engines, which also operate in a lean air-fuel mode. As in
the lean-burn gasoline engines, the exhaust of both types of engines is net
oxidizing and therefore is not conducive to the reducing reactions necessary to
remove NOx. It is an object of the present invention to improve the storage
efficiency and durability of the LNT and to prolong the useful life of the LNT
before regeneration is necessary.
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It is well known that NOx adsorbers are highly vulnerable to deactivation
by sulfur (see, for example, M. Guyon et al., Impact of Sulfur on NOx Trap
Catalyst Activity-Study of the Regeneration Conditions, SAE Paper No. 982607
(1998); and P. Eastwood, Critical Topics in Exhaust Gas Aftertreatment,
Research Studies Press Ltd. (2000) pp.215-218.) and other products resulting
from fuel combustion and normal lubricant consumption. It is an object of the
present invention to provide fuel or lubricant compositions capable of reducing
the adverse impact of sulfur, and other exhaust byproducts, on the emissions
system including NOx adsorbers and LNTs.
-
Performance fuels for varied applications and engine requirements are
known for controlling combustion chamber and intake valve deposits, cleaning
port fuel injectors and carburetors, protecting against wear and oxidation,
improving lubricity and emissions performance, and ensuring storage stability
and cold weather flow. Fuel detergents, dispersants, corrosion inhibitors,
stabilizers, oxidation preventers, and performance additives are known to
increase desirable properties of fuels.
-
Organometallic manganese compounds, for example
methylcyclopentadienyl manganese tricarbonyl (MMT®), available from Ethyl
Corporation of Richmond, Virginia, are known for use in gasoline as both
emissions-reducing agents and as antiknock agent (see, e.g. U.S. Patent
2,818,417). These manganese compounds have been used to lower deposit
formation in fuel induction systems (U.S. Patents 5,551,957 and 5,679,116),
sparkplugs (U.S. Patent 4,674,447) and in exhaust systems (U.S. Patents
4,175,927; 4,266,946; 4,317,657, and 4,390345). Organometallic iron
compounds, such as ferrocene, are known as well for octane enhancement
(U.S. Patent 4,139,349).
-
Organometallics for example compounds of Ce, Pt, Mn or Fe among
others have been added to fuel to enhance the ability of particulate traps to
regenerate or to directly reduce the emissions of particulate from diesel or
compression ignition type engines or other combustion systems. These
additives function through the action of the metal particles that are the
product of additive breakdown on the particulate matter during combustion or
in the exhaust or particulate trap.
Summary of the Invention
-
Accordingly, it is an object of the present invention to overcome the
limitations and drawbacks of the foregoing systems and methods to provide
methods for using a composition to protect and improve the operation of
combustion exhaust after treatment systems.
-
In one embodiment, a method of enhancing the operation of an emission
after treatment system in a diesel fuel combustion system includes supplying a
diesel fuel comprising an additive that includes a manganese compound to a
diesel fuel combustion system. The combustion system comprises a catalyzed
or, alternatively, continuously regenerating technology diesel particulate filter.
The fuel is then combusted in the combustion chamber to produce at least one
byproduct comprising the manganese compound. The manganese is in an
effective amount to complex with the at least one combustion byproduct. The
manganese compound or manganese ion may be an inorganic metal compound
or an organometallic compound. The inorganic metal compound can be
selected from the group consisting of fluorides, chlorides, bromides, iodides,
oxides, nitrates, sulfates, phosphates, carbonates, hydrides, hydroxides,
nitrides, and mixtures thereof. The organometallic compound is selected from
the group consisting of alcohols, aldehydes, ketones, esters, anhydrides,
sulfonates, phosphonates, chelates, phenates, crown ethers, carboxylic acids,
amides, acetyl acetonates, and mixtures thereof. A preferred organometallic
compound is manganese methylcyclopentadienyl tricarbonyl.
-
In a still further embodiment, a method of enhancing the operation of an
emissions after treatment system in a diesel fuel combustion system comprises
supplying a diesel fuel to a diesel fuel combustion system. The combustion
system may comprise a catalyzed diesel particulate filter or a continuously
regenerating technology diesel particulate filter. The fuel is combusted in a
combustion system to produce at least one combustion byproduct in an
exhaust stream. An additive comprising a manganese compound is injected
into the exhaust stream. The manganese compound complexes with at least
one combustion byproduct. The manganese compound which can be an
inorganic or organometallic compound is supplied in an effective amount to
complex with the at least one combustion byproduct. The inorganic metal
compound or organometallic compound may be as noted earlier herein.
-
In a still further embodiment, an emissions control system for the after
treatment of a diesel fuel combustion process exhaust stream comprises an
exhaust passageway. The exhaust passageway allows for passage of an
exhaust stream containing exhaust byproducts from the combustion of a diesel
fuel comprising a manganese compound. This system also includes a
catalyzed or continuously regenerating technology diesel particulate filter
located within the exhaust passageway and adapted to contact the exhaust
stream. The exhaust stream comprises a manganese compound which
complexes with at least one of the exhaust byproducts. The alternatives of
possible manganese compounds include those noted herein.
-
In a still further embodiment, an emission control system for the after
treatment of a diesel fuel combustion process exhaust stream includes an
exhaust passageway. The exhaust passageway for the passage of an exhaust
stream contains exhaust byproducts from the combustion of a diesel fuel. A
catalyzed or continuously regenerating technology diesel particulate filter is
located within the exhaust passageway and is adapted to contact the exhaust
stream. The exhaust stream has an additive introduced into it, the additive
comprising a manganese compound which complexes with at least one of the
exhaust byproducts. The alternatives of possible manganese compounds
include those noted herein.
-
In a still further embodiment, a method of enhancing the operation of an
emission after treatment system in a combustion system includes supplying a
fuel comprising an additive that includes a manganese compound to a fuel
combustion system. The fuel is then combusted in the combustion chamber to
produce at least one byproduct comprising the manganese compound. The
manganese is in an effective amount to complex with the at least one
combustion byproduct.
-
In a still further embodiment, a method of enhancing the operation of an
emissions after treatment system in a combustion system comprises supplying
a fuel to a combustion system. The fuel is combusted in a combustion system
to produce at least one combustion byproduct in an exhaust stream. An
additive comprising a manganese compound is injected into the exhaust
stream. The manganese compound complexes with at least one combustion by
product.
Detailed Description
-
The additives used in the methods and systems of the present invention
are inorganic or organometallic manganese containing compounds soluble in
fuels. This fuel is then combusted in a combustion system that includes an
after treatment system. It protects the after treatment system from harmful
combustion byproducts that could otherwise neutralize their effectiveness. The
manganese in the additive also promotes the oxidation of carbon particulate
matter. Upon introduction into the exhaust stream, the manganese comes into
contact with the carbon fraction of the particulate, accelerates carbon oxidation
reactions, and aids in after treatment system regeneration. The manganese
compound also reduces the rate of soot accumulation. The exhaust system
may also contain other after treatment systems.
-
The hydrocarbonaceous fuel combustion systems that may benefit from
the present invention include all combustion engines that burn fuels. By
"combustion system" herein is meant any and all internal and external
combustion devices, machines, engines, turbine engines, boilers, incinerators,
evaporative burners, stationary burners and the like which can combust or in
which can be combusted a fuel. Fuels suitable for use in the operation of
combustion systems of the present invention include diesel fuel, jet fuel,
kerosene, synthetic fuels, such as Fischer-Tropsch fuels, liquid petroleum gas,
fuels derived from coal, natural gas, propane, butane, unleaded motor and
aviation gasolines, and so-called reformulated gasolines which typically contain
both hydrocarbons of the gasoline boiling range and fuel-soluble oxygenated
blending agents, such as alcohols, ethers and other suitable oxygen-containing
organic compounds. Oxygenates suitable for use in the present invention
include methanol, ethanol, isopropanol, t-butanol, mixed C1 to C5 alcohols,
methyl tertiary butyl ether, tertiary amyl methyl ether, ethyl tertiary butyl ether
and mixed ethers. Oxygenates, when used, will normally be present in the
base fuel in an amount below about 25% by volume, and preferably in an
amount that provides an oxygen content in the overall fuel in the range of
about 0.5 to about 5 percent by volume. Other fuels that are useful in the
methods and devices of the present invention are gasoline, bunker fuel, coal
dust, crude oil, refinery "bottoms" and by-products, crude oil extracts,
hazardous wastes, yard trimmings and waste, wood chips and saw dust,
agricultural waste or tillage, plastics and other organic waste and/or by-products,
and mixtures thereof, and emulsions,
suspensions, and dispersions thereof in water, alcohol, or other carrier
fluids. By "diesel fuel" herein is meant one or more fuels selected from the
group consisting of diesel fuel, biodiesel, biodiesel-derived fuel, synthetic diesel
and mixtures thereof and other products meeting the definitions of ASTM
D975. It is preferred that the sulfur content of the diesel fuel be less than 100
ppm, and especially preferred that the sulfur content be less than 30 ppm.
Fuels having relatively high sulfur content, while within the scope of the
present invention, are currently impractical for use with catalytically enhanced
after treatment systems.
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Conventional combustion systems useful with the present invention will
typically include some degree of emission control or after treatment system. In
all cases of combustion, the emission treatment may include a catalytic system
to reduce harmful emissions. Of course, other emission treatment systems are
well known. Unfortunately, many of such emission systems have a tendency to
lose their effectiveness over time due to poisoning or degradation of emission
treatment system components.
-
The present invention contemplates providing a manganese compound to
an additive, to a fuel composition or, alternatively, directly into the exhaust
stream or combustion zone resulting from the combustion process, whereby
the operation of the emission treatment system components will be
significantly enhanced. A copending application discloses various delivery and
combination opportunities when using an aqueous, water soluble, manganese
containing additive. U.S. Patent Application Serial No. 10/165,462, filed June
7, 2002.
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The preferred metal herein includes elemental and ionic manganese,
precursors thereof, and mixtures of metal compounds including manganese.
These manganese compounds may be either inorganic or organic. Also
effective in the present invention is the generation, liberation or production in
situ of manganese or manganese ions.
-
Preferred inorganic metallic compounds in an embodiment of the present
invention can include by example and without limitation fluorides, chlorides,
bromides, iodides, oxides, nitrates, sulfates, phosphates, nitrides, hydrides,
hydroxides, carbonates and mixtures thereof. Manganese sulfates and
phosphates will be operative in the present invention and may, in certain fuels
and combustion applications, not present unacceptable additional sulfur and
phosphorus combustion byproducts. Preferred organometallic compounds in
an embodiment of the present invention include alcohols, aldehydes, ketones,
esters, anhydrides, sulfonates, phosphonates, chelates, phenates, crown
ethers, carboxylic acids, amides, acetyl acetonates, and mixtures thereof.
-
Especially preferred manganese containing organometallic compounds
are manganese tricarbonyl compounds. Such compounds are taught, for
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 B1.
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Suitable manganese tricarbonyl compounds which can be used in the
practice of this invention include cyclopentadienyl manganese tricarbonyl,
methylcyclopentadienyl manganese tricarbonyl, dimethylcyclopentadienyl
manganese tricarbonyl, trimethylcyclopentadienyl manganese tricarbonyl,
tetramethylcyclopentadienyl manganese tricarbonyl,
pentamethylcyclopentadienyl manganese tricarbonyl, ethylcyclopentadienyl
manganese tricarbonyl, diethylcyclopentadienyl manganese tricarbonyl,
propylcyclopentadienyl manganese tricarbonyl, isopropylcyclopentadienyl
manganese tricarbonyl, tert-butylcyclopentadienyl manganese tricarbonyl,
octylcyclopentadienyl manganese tricarbonyl, dodecylcyclopentadienyl
manganese tricarbonyl, ethylmethylcyclopentadienyl manganese tricarbonyl,
indenyl manganese tricarbonyl, and the like, including mixtures of two or more
such compounds. Preferred are the cyclopentadienyl manganese tricarbonyls
which are liquid at room temperature such as methylcyclopentadienyl
manganese tricarbonyl, ethylcyclopentadienyl manganese tricarbonyl, liquid
mixtures of cyclopentadienyl manganese tricarbonyl and
methylcyclopentadienyl manganese tricarbonyl, mixtures of
methylcyclopentadienyl manganese tricarbonyl and ethylcyclopentadienyl
manganese tricarbonyl, etc.
-
Preparation of such compounds is described in the literature, for
example, U.S. Pat. No. 2,818,417, the disclosure of which is incorporated
herein in its entirety.
-
When formulating additives to be used in the methods and systems of
the present invention, the manganese compounds are employed in amounts
sufficient to reduce the impact of poisons, e.g., sulfur, lead, zinc, soot and
phosphorus, on the after treatment systems, reduce the rate of soot
accumulation, reduce the temperature at which the soot oxidizes, and
otherwise generally enhance the operation of after treatment systems
including, for instance, a catalyzed diesel particulate filter, or alternatively, a
continuously regenerating technology diesel particulate filter.
-
Manganese compounds are believed to bind with poisons in the exhaust
stream to prevent those poisons from binding or depositing on an after
treatment system such as the catalytic surface of the diesel particulate filter.
See, e.g., A. J. Nelson, J. L. Ferreira, J. G. Reynolds, J. W. Roos and S. D.
Schwab, "X-Ray Absorption Characterization of Diesel Exhaust Particulates,"
Applications of Synchrotron Radiation Techniques to Materials Science V,
Materials Research Society Conference Proceedings, No. 590, 63 (2000). For
instance, manganese sulfates and phosphates may be formed and are trapped
within a filter. These manganese sulfates and phosphates do not form a glaze
over or otherwise tie up catalytic sites in a filter. This mechanism is
distinguished from other additives such as platinum. Platinum compounds do
not bond or otherwise complex with poisons such as sulfates and phosphates.
Instead, it is hypothesized in the literature that platinum compounds in an
additive act to replace or substitute as the catalyst on the surface of the filter.
It is basic chemical differences such as those described herein that distinguish
manganese from other metals like platinum. In formulating additives for use in
the present invention, therefore, it is important that effective amounts of
manganese be employed, and further that any other metal compounds that can
be additionally incorporated must not have any negative effects on the
manganese mechanisms.
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The amount or concentration of the additive may be selected based on
the concentration of sulfur in the diesel fuel. A preferred treatment rate of the
manganese compound can be in excess of 100 mg of manganese/liter, more
preferably up to about 50mg/liter, and most preferably about 1 to about
30mg/ liter.
-
The term "after treatment system" is used throughout this application to
mean any system, device, method, or combination thereof that acts on the
exhaust stream or emissions resulting from the combustion of a diesel fuel.
"After treatment systems" include all types of diesel particulate filters - -
catalyzed and uncatalyzed, lean NOx traps and catalysts, select catalyst
reduction systems, SOx traps, diesel oxidation catalysts, mufflers, NOx sensors,
oxygen sensors, temperature sensors, backpressure sensors, soot or
particulate sensors, state of the exhaust monitors and sensors, and any other
types of related systems and methods.
-
There are multiple types of diesel particulate filters (DPFs).
Conventional, uncatalyzed DPFs are a well-known technology that has been
used for many years. In operation, combustion byproducts such as
particulates and soot are trapped and then oxidized, or "burned off".
"Catalyzed diesel particulate filters" (C-DPFs) are filters incorporating a catalyst
on or within the filter substrate that are adapted to reduce the oxidation
temperature of the combustion byproducts captured in the filter. C-DPFs
currently include cordierite or silicon carbide monolithic type filters. A
"continuously regenerating technology diesel particulate filter" (CRT-DPF) is a
system where the catalyst is a separate, flow-through substrate that precedes
the diesel particulate filter in the exhaust passageway.
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Diesel fuels, when combusted in engines operating under the diesel
cycle, emit unburned soot particles into the exhaust gas stream. Because the
oxidation temperature of soot is in excess of 500°C, it is desirable to employ
catalysts either within or preceding the filters to lower the soot oxidation
temperature. A catalyst that is part of the filter substrate, i.e., a catalyzed
diesel particulate filter, or C-DPF, requires an exhaust temperature between
325 and 400°C to initiate filter regeneration. Regeneration is the oxidation of
accumulated soot. In this system, the soot accumulates on the catalytic sites
within the filter substrate and the combination of temperature, pressure and
the presence of the catalyst lower the temperature required for regeneration. In
a continuously regenerating technology diesel particulate filter, soot oxidation
temperature is reduced because the catalyst oxidizes NO in the exhaust gas to
NO2. The increased level of NO2 promotes an increased level of soot oxidation
within the filter.
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The terms "complex" or "complexing" are intended herein to describe the
combination of or reaction by the manganese containing compound with the
combustion byproduct(s) such as poisons, soot and other particulates. The
combination includes covalent or ionic reactions or any other binding of the
metal compound with the combustion byproduct. Further, the term
"combustion byproduct" includes, but is not limited to, particulates, soot,
unburned soot, uncombusted hydrocarbons, partially-combusted
hydrocarbons, combusted hydrocarbons, oxides of nitrogen, and any other gas,
vapor, particle or compound that results from the combustion of a fuel.
-
Reference is also made throughout of the term "enhanced" in the context
of operation of an emissions after treatment system. The term "enhanced"
means an improvement in the operation of an after treatment system relative to
the operation of a similar system that does not have a manganese compound
combusted or injected or otherwise streamed through it. "Enhanced" operation
includes, but is not limited to, reduction in the impact of poisons on the
emissions control system, reduction in the rate of soot accumulation, and
reduction in the temperature at which the soot is oxidized in the filter.
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When the emissions system contains a component which is poisonable
by combustion byproducts (such as those containing sulfur, phosphorus, lead,
zinc or soot), for instance, a barium-containing lean NOx trap, the present
invention provides novel methods for providing a substance which competes
with the active site (e.g., barium) in the lean-burning exhaust. As long as the
manganese containing compound of the additive will compete with the metal of
the catalyst system for complexing with the potential emissions system poisons
(e.g., sulfur) the manganese may be suitable for use as scavenging agents.
Further, the manganese scavengers of the present invention can reduce the
detrimental impact of other poisons such as sulfur, phosphorus, lead, zinc, or
soot on emissions control systems of the lean burn combustion systems in one
embodiment of the present invention.
-
In this invention, when the manganese containing, fuel-borne catalyst
was used in combination with the CRT-DPF, there was an unanticipated
benefit. There is a lower soot accumulation rate within the CRT-DPF and the
regeneration temperature is reduced below the regeneration temperature
observed with either the fuel-borne catalyst or CRT-DPF alone.
Example 1
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The additives useful herein are organometallic, manganese containing
compounds soluble or dispersible in diesel fuel. The manganese promotes the
oxidation of carbon particulate matter. The exhaust gas after treatment device
is a continuously regenerating technology diesel particulate filter (CRT-DPF).
Upon introduction of the fuel into the combustion chamber or exhaust stream,
the manganese is released and combines or complexes with the carbon fraction
of the particulate matter, accelerating the oxidation reactions that take place
prior to and during accumulation within the CRT-DPF. The measure of soot
loading within a filter is the increase in exhaust gas backpressure (EGBP). A
comparison of EGBP profiles during base and additized fuel soot loading tests
are shown in Figures 1 and 2. Figure 1 displays the initial soot accumulation
profile prior to catalyst light-off, and shows that use of the additized fuel leads
to an immediate benefit of reduced EGBP. The continuation of this benefit
through 10 hours is displayed in Figure 2. The soot accumulation rate for base
fuel, as measured by EGBP increase, is 0.06 kPa per hour. When additized
fuel is tested, the rate is reduced by a factor of three to 0.02 kPa per hour.
More details regarding this testing described herein is contained in SAE Paper
No. 2002-01-2728, "The Role That Methylcyclopentodienyl Manganese
Tricarbonyl (MMT) Can Play in Improving Low-Temperature Performance of
Diesel Particulate Filters" which is incorporated herein in its entirety.
-
The base fuel used in this example was an ultra-low sulfur diesel fuel
obtained from Phillips. This fuel had a nominal sulfur level of 3 ppm. The
additive was provided so that the additized fuel had 20 mgMn/liter. The
additive used was MMT® (Ethyl Corporation).
-
After filters are loaded with soot, it is useful to examine the temperature
where regeneration (the burning-off of accumulated soot) will occur. Figure 3
shows the results of regeneration tests when base fuels and additized fuels are
burned. With unadditized fuel, filter regeneration was not observed at
temperatures exceeding 380°C. With additized fuel, regeneration begins when
exhaust temperature exceeds approximately 280°C. The accumulated carbon
within the filter combusts, leading to complete filter regeneration. Notably,
once the soot is burned off, the engine backpressure remains below that
amount of backpressure seen with the unadditized fuel. In other words, not
only does the soot burn off at a lower temperature with the additized fuel, the
backpressure remains lower than with unadditized fuel as shown in Figure 3.
Example 2
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The exhaust gas after treatment device is a catalyzed diesel particulate
filter (C-DPF). Upon introduction of the additized fuel into the combustion
chamber or exhaust stream, the manganese is released and combines with the
carbon fraction of the particulate matter, accelerating the oxidation reactions
that take place prior to and during accumulation within the C-DPF. Because
the rate of soot accumulation is lower and the soot contains a catalyst metal,
the regeneration temperature is reduced relative to what would be expected
with the C-DPF and unadditized fuel.
Example 3
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In the applications described in Examples 1 and 2, the manganese used
will form stable metal complexes including manganese phosphates. A portion
of the manganese released into the combustion chamber or exhaust interacts
with lubricant-derived phosphorus to form the stable metal phosphates as
solid particulate and this reduces or prevents phosphorus deposition on the
catalyst metal employed in the CRT-DPF, or the C-DPF. The use of these
manganese containing fuel additives will protect the catalyst from deterioration
resulting from phosphorus poisoning.
Example 4
-
In the applications described in Examples 1 and 2, the manganese
additive used is one that will also form stable metal sulfates. The CRT-DPF or
C-DPF is followed by a lean-NOx storage device that is sensitive to sulfur
poisoning. A portion of the metal released into the combustion chamber or
exhaust interacts with either fuel or lubricant-derived sulfur to form stable
manganese sulfates, thereby scavenging the SO2 and SO3 and reducing or
preventing deposition of sulfur species on the lean-NOx storage device.
Example 5
-
The manganese containing additives of the present invention enhance
operation of an after treatment system by reducing the sintering of combustion
byproduct metal on the surface of the DPF. The sintering of combustion
byproduct metals may cover and render ineffective catalyst sites on the surface
of the catalyzed DPF. "Sintering" is the fusion of combustion byproduct
particles on the filter surfaces as a result of the heat in that filter. The
manganese containing additive reduces the amount of sintering on the filter
surfaces, as compared to the amount of sintering when unadditized fuel is
burned, and therefore increases the effective life of the filter. It also makes the
filter easier to clean because of the reduced sintering of the byproducts to the
walls of the filter.
Example 6
-
The manganese containing additives of the present invention enhance
operation of an after treatment system by accelerating ash buildup in a DPF
but nevertheless reducing rate of backpressure increase. The manganese
binds with combustion byproducts, e.g., sulfur and phosphorous oxides, and
forms stable manganese compounds that are then trapped as and with the ash
in the filter. Surprisingly, it has been discovered that this literal increase in
ash does not increase backpressure. Further, by using a manganese
containing additive, the DPF will need to be cleaned less often and the ash can
be more completely removed when it is cleaned.
-
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
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 course 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.
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At numerous places throughout this specification, reference has been
made to a number of U.S. Patents, published foreign patent applications and
published technical papers. All such cited documents are expressly
incorporated in full into this disclosure as if fully set forth herein.
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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 to be covered is as set forth
in the ensuing claims and the equivalents thereof permitted as a matter of law.
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Patentee does not intend to dedicate any disclosed embodiments to the
public, and to the extent any disclosed modifications or alterations may not
literally fall within the scope of the claims, they are considered to be part of the
invention under the doctrine of equivalents.