Method and composition for reducing emissions from a gasoline engine equipped with a three-way catalytic converter

Abstract

Gasoline engines equipped with three-way catalysts emit less NOx, hydrocarbons and carbon monoxide when operated on fuels containing a bimetallic catalyst comprising rhodium acetylacetonate and a fuel-soluble platinum compound such as diphenyl cyclooctadiene platinum(II) or platinum acetyl acetonate. The total metals in the additive will be dosed at a concentration of less than about 2 ppm (milligrams of metal to liter of gasoline) based on the amount of gasoline burned in the engine. Preferred dosages will be from about 0.15 to about 1.5 ppm, with a ratio of platinum to rhodium of from about 3:1 to about 15:1.

Description

[0001] The invention relates to compositions and methods that enable reduction of emissions while permitting a gasoline engine to operate efficiently.[0002] The use of three-way catalytic converters for gasoline-powered engines has become the standard. The life of these converters is often less than the life expected of the vehicles in which they are installed, due to attrition, poisoning, masking, sintering and mechanical damage. But, even when they lack the requisite activity to meet regulatory compliance, they still contain significant amounts of catalytic metals. Replacement is expensive and wasteful. And, unfortunately, many vehicles are and will continue to be driven long after they become environmental hazards.[0003] The art has endeavored to provide an additive for gasoline, which could be used for an entire fleet to maintain a suitable level of catalyst activity. It has further looked for a specific additive that could be added to gasoline at a suitable dosage to renew the ...

AI Technical Summary

Benefits of technology

0014] These and other objects are achieved by the present invention, which provides an improved composition and process for maintaining or renewing the activity of a three-way catalytic converter.

Problems solved by technology

The life of these converters is often less than the life expected of the vehicles in which they are installed, due to attrition, poisoning, masking, sintering and mechanical damage.

But, even when they lack the requisite activity to meet regulatory compliance, they still contain significant amounts of catalytic metals.

Replacement is expensive and wasteful.

And, unfortunately, many vehicles are and will continue to be driven long after they become environmental hazards.

This search has been difficult because effectiveness for one purpose must be balanced with other factors such as chemical composition necessary to deliver the catalyst to the catalytic converter at a cost that is practical and safe in terms of toxicity and handling.

This cost has been found to be a matter of initial synthesis as well as to the presence of incompatible chemical species.

Moreover, the search for effective catalytic fuel additives for improving the operation of a catalytic converter is a difficult technical problem because treatment of the various gaseous exhaust species presents conflicting requirements.

For example, lowering emissions of hydrocarbons and carbon monoxide are chemical oxidation problems while lowering emissions of NO.sub.x is a chemical reduction problem.

In the Epperly, et al., patent, it was noted that the additives could provide improved operation of a catalytic converter; however, all of the compounds referenced appear to require expensive synthesis procedures.

Applicants have determined, however, that the chlorides have several disadvantages, among which are a corrosive effect on the exhaust system, including certain catalyst supports, and a tendency to release catalyst metals from a catalyst support due to a decrease in the vapor pressure of the metal compounds.

In addition, chlorides can present negative health and safety issues.

Moreover, the concept of modulating concentration by varying the surface contact appears problematic in view of an expected variation of solubility with temperature and fuel composition.

Despite the industry's successful work on providing effective catalytic converters with creditable durability, there has not been the same degree of success with the identification of a specific bimetallic catalyst rejuvenator that could be directly added to gasoline for effective and economical effect.

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