Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Mixture is exhaust from internal-combustion engine
Patent
1992-08-26
1994-12-27
Chin, Peter
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Mixture is exhaust from internal-combustion engine
4232135, 4232137, 60300, 422180, 422222, B01D 5336
Patent
active
053763459
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improved catalytic reaction systems and to methods for catalytic reaction of carbon containing compounds. In one specific aspect the present invention relates to quick light-off, fast thermal response catalysts for use in catalytic exhaust gas reactors and in catalytic fuel combustion systems.
In one still more specific aspect, this invention relates to low thermal mass electrically conductive catalysts suitable for rapid electrical heating to operating temperature.
2. Brief Description of the Related Art
Automotive emissions are still a major environmental problem in spite of the major advances brought about by the use of catalytic converters. One factor limiting the performance of catalytic converters is that pollution is not controlled during the thirty or so seconds required to bring the converter catalyst to its operating temperature. In present converters, warm-up is dependent on heating of the catalyst by hot engine exhaust gases. Although electrical heating can be utilized to preheat the catalyst prior to engine operation, the power and the time delay required with present catalyst structures, ceramic or metal, have been deemed unacceptable.
The need to reduce catalyst warm-up time of the conventional ceramic monolith automotive catalysts to reduce emissions during the warm-up period has led to increased interest in metal monolith catalysts. However, merely substituting metal for ceramic in a conventional monolith structure yields catalysts which still have much too high a thermal mass. Although metal monoliths are electrically conductive and could therefore be electrically preheated, fast enough heat up times have not yet been demonstrated as feasible with conventional monoliths. Even if sufficient electrical power were made available, thermal shock damage would likely be a problem if a conventional metal monolith were heated as rapidly as needed for elimination of start-up emissions, even with use of a conventional miniature catalyst suitable for only partial conversion of start-up emissions. Thus there is a critical need for a catalyst system which can control hydrocarbon emissions during initial engine operation without the need for heating prior to engine cranking.
For catalytic combustors the problem is not just emissions but the ability to function in certain applications. For example, an automotive catalytic combustor gas turbine must start in roughly the same time frame as present automotive engines.
The present invention provides catalysts and systems which make possible much more rapid warm-up of converter catalysts without electrical heating and near instantaneous electrical heating of catalysts in combustors, catalytic converters and other chemical reaction systems.
SUMMARY OF THE INVENTION
Definitions of Terms
In the present invention the terms "monolith" and "monolith catalyst" refer not only to conventional monolithic structures and catalysts such as employed in conventional catalytic converters but also to any equivalent unitary structure such as an assembly or roll of interlocking sheets or the like.
The terms "low thermal mass catalyst" and "microtherm" used herein refer to a thermally shock resistant catalyst element or structure which can be heated from 300 degrees Kelvin to 800 degrees Kelvin at a rate of at least one hundred degrees Kelvin per second with a power input of less than fifty watts per square centimeter of open area in the plane perpendicular to the direction of flow.
The terms "microlith" and "microlith catalyst" refer to high open area monolith catalyst elements with flow paths so short that reaction rate per unit length per channel is at least fifty percent higher than for the same diameter channel with a fully developed boundary layer in laminar flow, i.e. a flow path of less than about two mm in length, preferably less than one mm or even less than 0.5 mm and having flow channels with a ratio of channel flow length to channel diameter less than about two to one, but prefera
REFERENCES:
patent: 3708982 (1973-10-01), Kitzner
patent: 3797231 (1974-03-01), McLean
patent: 3910850 (1975-10-01), Turner
patent: 4012290 (1977-03-01), Olson
patent: 4350664 (1982-09-01), Gaysent
patent: 4556543 (1985-12-01), Mochida
patent: 4976929 (1990-12-01), Cornelison
patent: 5026273 (1991-06-01), Cornelison
patent: 5146744 (1992-09-01), Whittenberger
patent: 5170624 (1992-12-01), Cornelison
patent: 5180559 (1993-01-01), Ma
patent: 5190812 (1992-08-01), Cornelison
patent: 5229080 (1993-07-01), Abe
patent: 5246672 (1993-09-01), Bak
patent: 5264186 (1993-11-01), Harada
patent: 5266279 (1993-11-01), Haerle
patent: 5286460 (1994-02-01), Abe
Chin Peter
Hoffmann John
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