Method of oxidizing soot and reducing soot accumulation in a diesel fuel combustion after treatment system

Abstract

A method of reducing the negative effects of accumulation of ash in a diesel fuel combustion system includes supplying a diesel fuel having an additive that includes a manganese compound to a diesel fuel combustion system. The combustion system includes a catalyzed diesel particulate filter or, alternatively, a continuously regenerating technology diesel particulate filter. The fuel is then combusted in the combustion system to product at least one byproduct that includes the manganese compound. The manganese compound is supplied in an amount effective to complex with the combustion byproduct.

Description

[0001] 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[0002] 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 NO...

AI Technical Summary

Benefits of technology

[0012] It is well known that NO.sub.x adsorbers are highly vulnerable to deactivation by sulfur (see, for example, M. Guyon et al., Impact of Sulfur on NO.sub.x 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 NO.sub.x adsorbers and LNTs.

[0013] 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.

[0015] 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.

[0016] 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.

[0023] 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.

Problems solved by technology

Retarding ignition timing from the best efficiency setting reduces HC and NO.sub.x emissions, while excessive retard of ignition increases the output of CO and HC.

Increasing coolant temperature tends to reduce HC emissions, but this results in an increase in NO.sub.x emissions.

However, in thermal reactors, NO.sub.x is largely unaffected.

Thermal reactors are seldom used, as the required setting dramatically reduces fuel efficiency.

While efficient, this procedure results in lower fuel economy.

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.

Diesel systems raise a different set of challenges for emissions control.

Thus, NO.sub.x reduction with conventional three-way catalysts is not feasible.

Improved fuel economy can be obtained by using a lean-burn gasoline engine, for example, a direct injection gasoline engine, however currently NO.sub.x 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 NO.sub.x adsorber or lean NO.sub.x trap (LNT), the superior fuel economy of the lean-burn gasoline engine cannot be exploited.

This change in operating conditions can adversely effect fuel economy as well as driveability.

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 NO.sub.x.

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.

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