Chemistry: analytical and immunological testing – Testing of catalyst
Reexamination Certificate
2000-05-26
2003-01-14
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Testing of catalyst
C422S119000, C436S056000, C436S084000, C436S149000, C436S164000, C436S172000
Reexamination Certificate
active
06506605
ABSTRACT:
This invention relates generally to a method for determining the efficiency of a catalyst coating and more particularly to a method for determining the effectiveness of a catalyst based ozone depletion system.
The invention is particularly applicable to and will be described with specific reference to an on-board diagnostic system determining failure of an ozone depletion system applied to heat exchange surfaces in a vehicle and indicating such failure to the vehicle's operator. However, the invention is believed to have broader application and could be employed to determine the conversion efficiency of a stationary system using a catalyst based ozone depletion system such as heat exchangers or HVAC systems in residential, commercial or industrial facilities. Still further, the invention is also believed to have application to certain catalyst formulations, other than those utilized in an ozone depletion system, but which have distinguishing performance characteristics similar to those of a catalyst based ozone depletion system.
INCORPORATION BY REFERENCE
The following United States patents are incorporated by reference herein and made a part hereof:
a) U.S. Pat. No. 5,051,671 issued Sep. 24, 1991 to Crider et al. entitled “Proximity Sensor and Control”;
b) U.S. Pat. No. 4,325,255 issued Apr. 20, 1982 to Howard et al. entitled “Ultrasonic Apparatus and Method for Measuring the Characteristics of Material”;
c) U.S. Pat. No. 5,556,663 issued Sep. 17, 1996 to Chang et al. entitled “Excimer Fluorescence Method for Determining Cure of Coatings”;
d) U.S. Pat. No. 5,343,146 issued Aug. 30, 1994 to Kock et al. entitled “Combination Coating Thickness Gauge Using a Magnetic Flux Density Sensor and an Eddy Current Search Coil”;
e) U.S. Pat. No. 5,185,773 issued Feb. 9, 1993 to Blossfeld et al., entitled “Method and Apparatus for Nondestructive Selective Determination of a Metal”; and,
f) U.S. Pat. No. 6,034,775 issued Mar. 7, 2000 to McFarland et al., entitled “Optical Systems and Methods for Rapid Screening of Libraries of Different Materials”.
The above patents are cited so that the Detailed Description of this Invention need not recite in detail sensor apparatus and techniques known to those skilled in the art. None of the patents cited above or incorporated by reference herein form any part of the present invention.
BACKGROUND
i) Catalyst Based Ozone Depletion Systems
It is known that ground-level ozone, O
3
, is the main harmful ingredient in smog and at relatively small concentrations, ground level atmosphere is physically harmful. It is also known that ozone is produced by complex chemical reactions when its precursors such as VOC (volatile organic compounds) and NOx (nitrogen oxides) react in the presence of sunlight. The precursors mentioned are present in emissions produced from vehicles powered by internal combustion engines. The United States EPA has determined that cars and light trucks emit a substantial portion of precursors which produce ground level ozone.
The EPA, in implementing the provisions of the United States Clean Air Act, has identified 26 metropolitan areas within the United States which its modeling techniques show have or will exceed National Ambient Air Quality Standards for ozone in the near future. Accordingly, the EPA has promulgated increasingly tighter emission regulations directed to limiting emissions from vehicles which promote ozone formation.
It has been recognized for some time that a significant quantity of atmospheric air is used or drawn in by a vehicle while it is moving and that atmospheric air can be cleansed by the vehicle. For example, U.S. Pat. No. 3,738,088 to Colosimo passed a stream of atmospheric air drawn into a duct at the front of a vehicle through a filter and an electrostatic precipitator, powered electrically by the engine, which removed particulates from the atmospheric air before exhausting the cleansed air back into the atmosphere. Similar cleansing techniques have been widely used for purifying cabin air in a moving vehicle.
While there are various known ways or methods to remove or convert ozone to a benign chemical or compound, the assignee of the present invention has determined and formulated various catalyst coatings utilizing Manganese Dioxide, MnO
2
, which has been found effective to convert ozone to oxygen (O
3
→3/2O
2
) at slightly elevated temperatures. Reference can be had to assignee's U.S. Pat. No. 5,997,831, U.S. Ser. No. 09/151,784 filed Sep. 11, 1998 and Ser. No. 09/317,723 filed May 24, 1999 for examples of catalyst coatings which contain an ozone depleting substance, principally forms of MnO
2
, all incorporated by reference herein. Specifically, the assignee has determined that vehicles having radiators and/or air conditioning units operate at slightly elevated temperatures from ambient whereat the ozone depleting catalysts formulated by assignee are especially effective in converting ozone to oxygen while exhibiting characteristics allowing the catalyst to adhere to vibrating surfaces and function in the harsh environment that a motor vehicle is subjected to. The assignee of this invention has marketed its ozone depleting substances under its PremAir® brand name.
The environmental regulatory agencies have recognized the potential for vehicles to purify the atmosphere as well as being one of the causes of air pollution. To the extent that internal combustion engines produce emissions which cause the formation of ozone then, in principle, an offsetting “credit” should and is allowed providing that a vehicle can be shown to reduce ground level ozone present in the atmosphere. In practice this requires an on-board diagnostic (OBD) system to determine the effectiveness of the vehicle to cleanse or convert ozone in atmospheric air to a clean form, i.e., O
2
.
Obviously, the most effective way to determine the functioning of an ozone depletion system is to measure the ozone concentration in the atmospheric air stream upstream and downstream of the ozone depletion system. The difference between the measurements provides an accurate “count” of the quantity of ozone removed from the atmospheric air stream passing through the ozone depleting system. Another type of OBD system is widely used to determine the functioning of the typical TWC catalyst (three way catalyst) for removing HC (hydrocarbons) in that oxygen sensors, upstream and downstream of the TWC catalyst, sense upstream and downstream oxygen concentrations in the exhaust gas to estimate a storage capacity of the TWC catalyst which in turn is correlated to the efficiency at which the TWC catalyst converts certain noxious emissions.
A direct ozone sensing approach will not practically function today as an OBD system to measure the effectiveness of an ozone depletion system installed on a moving vehicle for several reasons. First, the ozone concentration that is being sensed is small and variable. For example, standard regulatory limits are 0.12 ppm over one hour with proposed regulations reducing the exposure to 0.08 ppm over an 8 hour period. Even in high smog concentration areas, such as Los Angeles, ground level ozone concentration may reach 0.20 ppm during summer, daytime hours and 0.01-0.02 ppm during nightime. The ozone sensor has to therefore have a sensitivity sufficient to detect and measure minute quantities of ozone present in a moving gas stream. Second, while current ozone detectors exist that can measure ozone concentration in the range of 100 ppb, the cost of current ozone sensors (priced in the thousands of dollars and not unusually, in the ten thousand dollar range) far exceeds that acceptable for an OBD application, even given the scales of economy achieved in the automotive market. Third the physical dimensions, response time and robustness of currently available ozone sensors is simply insufficient for an OBD system. For example many ozone sensors use a two step process of measuring light absorption through transmission measurements in an ozone free reference sample compared to an extracted ambient atmosphere sample to de
Allen Fred Mitchell
Anderson Dennis Ray
Heck Ronald Marshall
Hoke Jeffrey B.
Liu Xinsheng
Engelhard Corporation
Lindenfelder Russell G.
Soderquist Arlen
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