Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
  • F01N3/2807—Metal other than sintered metal
  • F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
  • F01N3/2817—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates only with non-corrugated sheets, plates or foils
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
  • F01N3/2825—Ceramics
  • F01N3/2828—Ceramic multi-channel monoliths, e.g. honeycombs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
  • F01N3/2835—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support fibrous
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2839—Arrangements for mounting catalyst support in housing, e.g. with means for compensating thermal expansion or vibration
  • F01N3/2842—Arrangements for mounting catalyst support in housing, e.g. with means for compensating thermal expansion or vibration specially adapted for monolithic supports, e.g. of honeycomb type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2330/00—Structure of catalyst support or particle filter
  • F01N2330/02—Metallic plates or honeycombs, e.g. superposed or rolled-up corrugated or otherwise deformed sheet metal
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2330/00—Structure of catalyst support or particle filter
  • F01N2330/06—Ceramic, e.g. monoliths
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2330/00—Structure of catalyst support or particle filter
  • F01N2330/10—Fibrous material, e.g. mineral or metallic wool
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
  • F01N2570/12—Hydrocarbons

Definitions

• This invention relates to improved catalytic converters for control of automotive emissions.
• this invention relates to fast light-off, low pressure drop catalytic converters. It also relates to converters to achieve very high conversions.
• the present invention not only makes possible improved catalyst utilization of rugged fast light- off catalytic converters for automotive engine exhaust control which utilize the short channel length catalysts such as those of the above cited patent and the co-pending application filed February 23. 1994 (attorney docket #2885-23), but of conventional catalytic monoliths.
• monolith and “monolith catalyst” refer not only to conventional monolithic structures and catalysts such as employed in conventional catalytic converters but also to short channel length structures of enhanced mass transfer efficiency such as woven screens.
• minilith refers to monolith elements having flow channels of less than three millimeters in length and more than forty channels per square centimeter.
• catalyst brick refers to an assembly of minilith catalyst elements having channel flow passages less than three millimeters in length and having more than forty channels per square centimeter and spaced apart by monolith elements of larger channel size.
• carbonaceous compound and "hydrocarbon” as used in the present invention refer to organic compounds and to gas streams containing fuel values in the form of compounds such as carbon monoxide, organic compounds or partial oxidation products of carbon containing compounds.
• light-off refers to the temperature at which a catalyst achieves about fifty percent of the conversion achieved at the normal operating temperature.
• the increased catalytic frontal area achivable with converters of the present invention allows a greater catlyst volume for a specified pressure drop, or alternatively use of much higher channel density, to achieve a greater conversion efficiency in pressure drop limited applications.
• the catalysts of prior U.S. patent #5,051,241 and the aforementioned application filed on February 23, 1994, incorporated herein by reference thereto, are especially advantageous in the present invention.
• Mass transfer of reactants to the surface becomes sensitive to the inlet flow rate rather than being significantly limited by the diffusion rate through a thick laminar flow boundary layer as in conventional monolith catalysts, whether ceramic or metal.
• the amount of pollutants oxidized is essentially independent of exhaust gas flow rate and thus percent conversion decreases with increase in flow rate.
• the amount of reactants oxidized typically increases with increase in flow rate.
• the reaction rate can even approach the intrinsic kinetic reaction rate at the given catalyst temperature without imposing an intolerable pressure drop.
• Conversion levels of 99.9% or even higher are achievable in an automotive converter smaller in size than a lower conversion level conventional catalytic converter. Even conversion levels high enough for abatement of toxic industrial fumes are achievable in compact reactors.
• catalysts bricks used in the present invention allows placement of a converter close to engine exhaust ports for more rapid heatup on starting an engine at low ambient temperatures. It has also been found that channel walls as thin as 0.1 mm or even less than 0.03 mm are practical with small channel diameters thus permitting high open areas even with such small channel diameters. Thus, as many as several thousand flow channels per square centimeter or even more are feasible without reducing open area in the direction of flow below sixty percent. Open areas greater than 65, 70 or even 80 percent are feasible even with high channel density miniliths.
• the reduced catalyst mass together with the increased heat transfer rate enables a short channel catalyst to reach operating temperature much sooner than would a conventional automotive catalyst. If placed sufficiently close to the engine exhaust manifold, a minilith catalyst element can even reach operating temperature in less than ten seconds without the need for electrical heating.
• Many alloys are commercially available which are suitable for metal miniliths of the present invention including Haynes alloy 25, Inconel 600, and even certain stainless steels. With metal microliths, alloy selection is often determined primarily by oxidation resistance at the maximum operating temperature required by the given application.
• the low pressure drops possible with catalytic converters based on the present invention makes it possible to utilize a large number of small diameter elements, even as many as two hundred in a one inch length, such that the converter diameter is not significantly larger than the engine exhaust pipe. This makes it much easier to place the converter catalyst at the exit of or even in the engine exhaust manifold, resulting in even faster catalyst warm up without electrical heating, and allows use of screens of different composition to achieve both hydrocarbon and NOx control. In fume abatement applications, the large number elements feasible means that it practical to achieve whatever conversion levels are needed, even as high as 99.999 or better.
• catalytic reactors based on the present invention offer advantages in any catalytic conversion system where reactor diameter is advantageously minimized or where it is desireable to minimze catalyst bed depth.
• Figure 1 shows a cross-sectional side view of a conventional monolith catalyst mounted in a conduit at an oblique angle to the direction of flow.
• Figure 2 shows a cross sectional side view of a converter with an oblique mounted monolith having flow paths parallel to the direction of the flow through the converter.
• a monolith catalyst 11 is mounted in housing 10 at an oblique angle relative to the inlet gas flow direction.
• the catalyst is mounted at an angle of between about ten and forty degrees to the direction of flow.
• monolith 21 has flow paths essentially parallel to the direction of converter flow in converter 20 so that fluid passing through converter 21 enters the flow channels with minimal change in direction as shown by the flow direction arrow thus allowing monolith 21 to be mounted at an oblique angle, phi, as little as five degrees. This reduces pressure losses.
• monolith 21 is an assembly of minilith catalysts, preferrably in the form of a catalyst brick such as described in pending patent application case attorney draft 2885-23 filed on February 23, 1994. It should be noted that unlike parallel mounted catalyst beds, oblique mounting promotes a uniform fluid approach velocity across the catalyst inlet face. This is because the flow cross sectional area decreases in appoximate proportion to the flow volume.
• a minilith catalyst of the present invention is made by vacuum sputtering platinum onto a stainless steel screen which has been cleaned by heating in air to 750K. Typically the platinum coating may be thinner than 100 angstroms but may be thicker for greater catalyst life.
• a similarly thin layer of ceria or alumina may be deposited prior to deposition of the platinum.
• Catalysts containing palladium, iridium, rhodium or other metals can be similarly prepared.
• a wire screen formed from a catalytic alloy such as a platinum doped alloy
• a catalytic alloy such as a platinum doped alloy
• ceramic miniliths can be made such as by slicing of ceramic honeycomb extrudates prior to firing. Such ceramic honeycomb extrudates advantageously may contain an organic binder to facilitate production of thin slices.
• ceramic miniliths are most advantageously in the form of fiber mats or screens composed of long fibers spun from any desired ceramic composition, preferably catalytic ceramics. As necessary for sufficient low temperature catalytic activity, ceramic and metal miniliths may be catalyzed using various techniques well known in the art.
• a multi-element catalytic microlith automotive exhaust reactor having forty minilith catalyst elements of 250 flow channels per square centimeter is constructed using a five centimeter wide strip of 70% open area screening of platinum coated stainless steel wires having a diameter of 0.10 mm with each screen spaced apart by a downstream screen having four channels per square centimeter with platinum coated wires 0.25 mm in diameter with the assembly clamped between two heavier screens of 1.5 mm diameter wires having one channel per square centimeter to form a catalyst brick nominally thirty centimeters long which is mounted in a container at an oblique angle of about nine degrees to the gas flow.
• catalyst light-off is within ten seconds of engine starting and thus exhaust emissions are controlled during initial operation of the engine.
• a fume abatement reactor is onstructed with a catalyst brick having 100 elements of screening with about thirty 0.050 mm wires of platinum coated nichrome per centmeter (nominally 900 flow channels per square centimeter) . Each element is spaced apart from the preceeding one by a screen having nine 0.10 mm wires per centimeter.
• the catalyst brick is mounted at an oblique angle of five degrees to the gas flow to minimize pressure drop with a minimum reactor diameter. Fumes containing 50 pp by volume of benzene in air are preheated to 700 degrees Kelvin and passed through the microlith reactor. Better than 99.9 percent conversion of the benzene to carbon dioxide and water is achieved.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Exhaust Gas After Treatment (AREA)
• Catalysts (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1995
  • 1995-08-16 EP EP95930851A patent/EP0724474A4/de not_active Withdrawn
  • 1995-08-16 CA CA 2173959 patent/CA2173959A1/en not_active Abandoned
  • 1995-08-16 WO PCT/US1995/010492 patent/WO1996005906A1/en not_active Application Discontinuation
  • 1995-08-16 JP JP8508200A patent/JPH09504474A/ja active Pending

Patent Citations (4)

Non-Patent Citations (1)

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