Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing nonmetal element
Reexamination Certificate
2000-01-31
2002-10-15
Nguyen, Nam (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing nonmetal element
C205S763000, C423S212000
Reexamination Certificate
active
06464854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of providing water for use on-board an automobile. More particularly, the present invention relates to operating an electrolyzer on-board an automobile.
2. Background of the Related Art
Catalytic converters are commonly used to reduce unwanted emissions through catalytic combination of the emissions with oxygen from the air. Catalytic combination, often referred to as catalytic combustion, is a flameless process in which mixtures of emissions (or fuel) and air (or oxygen) are passed over a catalyst at a temperature high enough to favor total oxidation of the emissions (or of the fuel). The reaction occurs at the catalyst surface resulting in liberation of energy and production of reaction products. For organic fuels, the reaction products are primarily carbon dioxide and water.
The control and suppression of unwanted emissions created by the operation of an internal combustion engine is a primary consideration for engine designers and vehicle manufacturers because of nearly world-wide governmental requirements regarding acceptable emission levels. Over eighty percent (80%) of the unacceptable emissions or pollutants created by internal combustion engines equipped with catalytic converters occur during cold start operations. These pollutants are emitted for a period of one to three minutes after cold engine starting, in large part because that is the time period required for the catalyst to reach an efficient operating temperature. Therefore, even though the engine exhaust is flowing through the catalytic converter, until the exhaust heats the catalytic converter to its operating range from engine start up, the engine emissions are only slightly catalytically decomposed during that time period.
In order to meet governmental emission standards for internal combustion engine exhaust, a catalytic converter is located in the exhaust stream of the engine. The converter typically includes a canister holding a suitable catalyst, such as a three-way catalytic converter (TWC) catalyst monolith, that will oxygenate unburned, unacceptable components in the exhaust stream including hydrocarbons (HC), their partially oxidized derivatives such as aldehydes and carbon monoxide (CO), and at the same time reduce nitrogen oxides (NO
x
), after almost stoichiometric fuel bum with oxygen in the cylinders of the engine. The exhaust gas is passed through the catalyst monolith, thereby completing the oxygenation of unburned HC and CO, and the reduction of NO
x
in the exhaust to convert these unacceptable emissions into acceptable emissions. Certain unacceptable emissions in the exhaust stream, including unburned hydrocarbons and carbon monoxide, require an oxidation reaction to destroy them so that they end up as the corresponding oxides, e.g., water and carbon dioxide. On the other hand, NO
x
requires a reduction reaction to develop N
2
and O
2
. In fact, the O
2
product of this reduction contributes to the oxidation of the HC and CO in the exhaust.
Catalytic converters are typically manufactured by coating a substrate, such as a metal or ceramic material, with a high surface area material, typically a metal oxide media. The catalytic material, such as a noble metal, is then deposited on the high surface area material. In the formation of such a catalytic converter, a sintered, dense and hardened ceramic substrate for example, which can be in the shape of a honeycomb, wagon-wheel, spiral or other molded or shaped objects, or simply be in the form of pellets, is coated with a slurry of the high surface area material, after which the catalyst is applied to the slurry-coated substrate, typically by application of a solution of a salt of that metal.
More particularly, the underlying ceramic substrate can be cordierite, mullite, alumina, lithium aluminosilicates, titania, zircon, feldspar, quartz, fused silica, clays, kaolin clay, aluminum titanate solid solutions, silicates, zirconia, spinels, glasses, glass ceramics, aluminates, and mixture thereof The constituent ceramic materials are generally admixed with binders or shaping agents, processed, molded where applicable, and sintered. Coating of the substrate with the high surface area media can be effected either by immersion or dipping, followed by heat-treating the coated substrate at a temperature between 500° C. and 600° C. Procedures for depositing a high surface area “wash-coat” on the previously sintered ceramic substrate are disclosed, for example, in U.S. Pat. No. 3,824,196. Following application of the slurry of high surface area material, the catalyst is applied in the manner stated above. Alternatively, a single “wash-coat” mixture of the high surface area media and the catalytic material can be applied together.
TWC catalysts are currently formulated and designed to be effective over a specific operating range of both lean and rich fuel/air conditions and a specific operating temperature range. These particular catalyst compositions enable optimization of the conversion of HC, CO, and NO
x
. This purification of the exhaust stream by the catalytic converter is dependent on the temperature of the exhaust gas and the catalytic converter works optimally at an elevated temperature, generally at or above about 300° C. “Light-off temperature” is generally defined as the temperature at which fifty percent (50%) of the emissions from the engine are being converted as they pass through the catalyst. The time period between “cold start” and reaching the light off temperature is generally referred to as the “light-off time.”
The conventional method of heating the catalytic converter is to heat the catalyst by contact with high temperature exhaust gases from the engine. This heating, in conjunction with the exothermic nature of the oxidation reaction occurring at the catalyst, will bring the catalyst to light-off temperature. However, until the light-off temperature is reached, the exhaust gas passes through the catalyst relatively unchanged. In addition, the composition of the engine exhaust changes as the engine heats from the cold start temperature, and the catalyst monolith is typically designed to work best with the composition of the exhaust stream produced at the normal elevated engine operating temperature.
There have been several attempts to shorten or avoid the light-off time of the catalytic converter. Current techniques employ one of the following methods: electrical heating of the exhaust gases and/or of the catalytic converter itself; thermal insulation of the exhaust line and/or the catalytic converter; multi-chambered configurations of the catalytic converter; placing the catalytic converter adjacent to the engine for heating; combustion of fuels upstream of the catalytic converter; and catalytic combination of fuels and oxygen at the catalyst surface. All of these methods have drawbacks and limitations.
Placing the catalytic converter almost immediately adjacent to the engine is not desirable because of the tendency to overheat the catalyst with resulting accelerated degradation of the catalyst. Thermal insulation is also not a desirable option because of the same problems, especially during operation at maximum operating temperature ranges.
Electrical heating of catalytic converters (“EHC”) has been a popular proposed method of attempting to preheat the catalyst monoliths. Limitations on the equipment and process, however, affect the utility of this method. The primary limitation on electrical preheating is the electrical energy required by the heater. The typical car battery is not a practical power source to supply the electrical power because the electrical load on the vehicle battery during the period required may exceed the rated battery output. In any event, the load placed on a typical 12 volt vehicle battery will shorten the lifetime of the battery. Also, there is a measurable delay between the time the operator of the vehicle places the ignition switch in the “on” position and the time the heater brings the catalyst to light-
Andrews Craig C.
Appleby A. John
Cisar Alan J.
Murphy Oliver J.
Salinas Carlos
Lynntech Inc.
Nguyen Nam
Smith-Hicks Erica
Streets Jeffrey L.
Streets & Steele
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