Catalysts were first widely introduced on series production cars in the U.S. market for model year 1975 to comply with stricter environmental regulations US Protection Agency on exhaust emissions of automobiles. Catalytic converters are still most commonly used systems of motor vehicles, but can also be used on generators, forklifts, mining equipment, trucks, buses, locomotives, airplanes and other engines mounted on the units. Normally, this is a response to government regulation.
The main catalyst, or substrate. "Catalytic converter recycling", the heart is often a ceramic monolith with a honeycomb structure, made of sheet metal but FeCrAl monoliths were introduced in the 1990's and are used by some car manufacturers. The honeycomb geometry provides a large surface area to support the primary reactant, catalyst, and is often called a catalyst support.The cordierite ceramic substrate used in most of the "Catalytic Converter Recycling" was invented by Rodney Bagley, Irwin Lachman and Ronald Lewis at Corning Glass for which they were inducted into the Hall of Fame National Inventors in 2002.
The catalyst was invented by Eugene Houdry, a French engineer and expert in the petroleum refining catalyst, who lived in the United States around 1950. When the results of the first studies on the smog of Los Angeles was published Houdry was concerned about the role of car exhaust in the air and form a separate company, Oxy-catalyst, to develop catalytic converters for motors gasoline - an idea ahead of his time as he was granted a patent (US2742437). The widespread adoption had to wait until it is extremely effective anti-knock agent tetraethyl lead was removed from gasoline in most environmental concerns, because the lead would destroy the inverter to form a coating on the surface of catalyst, effectively turning it off.
"Catalytic Converter Recycling" is a device used to convert the toxic exhaust gases from a combustion engine of non-toxic substances. Inside of a catalyst that stimulates a catalyst for a chemical reaction in which harmful by-products of combustion through a chemical reaction. The type of chemical reaction depends on the type installed as a catalyst, such as the current North American gas light trucks are equipped with a three-way "Catalytic Converter Recycling", which reduces carbon monoxide (CO), unburned hydrocarbons ( HC) and nitrogen oxides (NO, NO2 and N2O) to produce carbon dioxide (CO2), nitrogen (N2) and water (H2O). The catalyst was developed by John J. Mooney and Carl D. Keith from Engelhard Corporation, creating the first generation catalyst in 1973.
The washcoat. A washcoat is a carrier of catalytic materials and equipment used to broadcast over a large area. Aluminum oxide, titanium dioxide, silicon dioxide, or a mixture of silica and alumina can be used. Catalytic materials are suspended in washcoat before applying for the kernel. Washcoat materials are selected to form a rough surface, irregular, increasing the surface over the smooth surface of bare substrate. It maximizes the catalytic surface available to react with the engine exhaust.
These three reactions occur most efficiently when the "Catalytic Converter Recycling" receives exhaust of an engine running slightly above the stoichiometric point. This is between 14.6 and 14.8 parts of air to feed a part by weight of gasoline. The ratio of LPG (liquefied petroleum or gas (LPG)), natural gas and ethanol fuels are each a little different, requiring a change in the parameters of the fuel system when using these fuels. Generally, engines with 3-way catalytic converters are equipped with a computerized closed loop feedback system fuel injection using one or more oxygen sensors, so early in the deployment of three-way catalysts, carburetors equipped for feedback control mixture were used.
The same catalyst is most precious. Platinum is the catalyst more active and is widely used, but is not suitable for all applications because of unwanted additional reactions and high costs. Palladium and rhodium are two other precious metals used. Reduction catalyst with rhodium, palladium, used for testing, and platinum is used for both reduction and oxidation. Cerium, iron, manganese and nickel are also used, although each has its limitations. Nickel is not legal for use in the European Union (as the reaction of carbon monoxide). Copper can be used everywhere except North America, where its use is illegal, because the formation of dioxins.
This type of "Catalytic Converter Recycling" is widely used in diesel engines to reduce emissions of hydrocarbons and carbon monoxide. They are also used in gasoline engines for cars on American and Canadian market until 1981. Why am I not able to control nitrogen oxides, have been replaced by three-way converters. Since 1981, three-way (redox) catalysts have been used in systems for controlling vehicle emissions in the United States and Canada, in many other countries have adopted stringent regulations on vehicle emissions, which effectively require one to three way converters are on petrol-driven vehicles. Three-way catalytic
Three-way catalysts are effective when the engine is used in a narrow band of air-fuel ratio near stoichiometry, so that the exhaust gas ranges from the rich (excess fuel) and lean (excess oxygen) . But the conversion efficiency drops very quickly when the engine is operating outside of this band of air-fuel ratio. During the lean engine operation, there is an excess of oxygen and NOx reduction is not favored. In rich conditions, consumer surplus fuel all available oxygen before the "Catalytic Converter Recycling" is only stored oxygen available for the oxidation. Systems, closed loop control is necessary because of the conflicting demands of an effective reduction of NOx and HC oxidation. The control system shall prevent the NOx reduction catalyst to be completely oxidized, but to replenish the oxygen storage material to retain its function as an oxidation catalyst.
Side effects may occur in the three-way catalyst, such as the formation of hydrogen sulfide and ammonia odiferous. The formation of each may be limited by changes in the washcoat and precious metals used. It is difficult to withdraw them completely. Removing sulfur-free or low-sulfur, or reduction of hydrogen sulfide. For example, when controlling emissions of hydrogen sulfide desired, nickel or manganese added to the washcoat. Both drugs work to block the adsorption of sulfur in the washcoat. Hydrogen sulfide is formed when the washcoat has adsorbed sulfur during a low temperature part of the operating cycle, which is then released during the high temperature part of the cycle and the sulfur combines with HC.
Three-way catalytic converters can store oxygen in the exhaust gas stream, usually when the air-fuel ratio is low. When insufficient oxygen is available in the exhaust stream, the stored oxygen is released and consumed (see cerium (IV)). The lack of oxygen occurs when oxygen in the NOx reduction is not available or certain maneuvers such as enriching the mixture hard acceleration beyond the capacity of the converter for the supply of oxygen.
The reduction of NOx emissions from compression ignition engines has been addressed by the addition of exhaust gases to incoming air charge, known as exhaust gas recirculation (EGR). In 2010, most diesel light produced in the United States said catalytic systems for vehicles to meet new federal requirements for emissions. There are two techniques that were developed for the catalytic reduction of NOx under lean exhaust conditions - Selective Catalytic Reduction (SCR) and lean NOx trap or NOx adsorption. Instead of precious metals containing NOx adsorbers, most manufacturers of metals selected SCR system uses ammonia as a reagent for reducing NOx into nitrogen.
For compression ignition (diesel engines know), the catalyst most commonly used is the diesel oxidation catalyst (DOC). This catalyst uses O2 (oxygen) in exhaust gases to convert the CO (carbon monoxide) into CO2 (carbon dioxide) and HC (hydrocarbons) in H2O (water) and CO2. These converters are often operating at 90 percent efficiency, virtually eliminate odors and help reduce diesel particulate matter (soot). These catalysts are not active for the reduction of NOx, because any reducing agent present react first with the high concentration of O2 in diesel exhaust.
Diesel exhaust contains relatively high levels of particulate matter (soot), which is in much elemental carbon. Catalysts can not clean elemental carbon, even if they remove up to 90 percent of the soluble organic fraction is then purified particles of soot trap or diesel particulate filter (DPF). A FAP is composed of a cordierite substrate with a geometry that forces the exhaust flow through the substrate walls, leaving the soot particles trapped. As the amount of soot trapped in the DPF increases, the pressure against the exhaust.
Many of the vehicles are coupled catalyst near the engine exhaust manifold. This device heats up quickly, because it is close to the engine, and reduce cold engine emissions from burning of the richest oil are used to start a cold engine. In the past, about three-way catalyst used by the air injection pipe between the first (NOx reduction) and the second (oxidation of HC and CO) phase converter. This tube was part of the secondary air injection system. Injected into the air to set the oxidation reactions of oxygen. Upstream of the air injection point was also some oxygen during the heating of the engine, which led to the unburnt fuel in the light of the first section of the exhaust catalyst.
Catalyst poisoning occurs when the catalyst is exposed to exhaust gases contain substances that coat the surfaces of work, the encapsulation of the catalyst, so that it can contact and treat the exhaust gases. The most prominent guest is an advantage, so that vehicles fitted with catalytic converters can be used in unleaded gasoline. Other common catalyst poisons are manganese (mainly from gasoline additive MMT), and silicone, which can become a flow of exhaust gas when the engine has a leak, the coolant in the combustion chamber. Phosphorus is another catalyst impurities. Although phosphorus is no longer used in gasoline, is (and zinc, the second low-level catalytic away) was, until recently, widely used anti-wear additives in engine oil, such as zinc dithiophosphate.
More modern systems of "Catalytic Converter Recycling" does not have air injection systems. Instead, provide a constant change of air-fuel mixture that quickly and exhaust cycles continuously between rich and poor. Oxygen sensors are used to control the escape of oxygen before and after the "Catalytic Converter Recycling", and this information is used by the electronic control unit to adjust the fuel injection to avoid the first (NOx reduction) to become a catalyst charged oxygen, while maintaining the second (the oxidation of HC and CO) catalyst is sufficiently saturated with oxygen. The reduction and oxidation catalysts are normally found in a single case, however, in some cases can be stored separately.
Any condition that causes abnormally high levels of unburned hydrocarbons - raw or partially burned fuel - to reach the converter will tend to raise its temperature significantly, so the risk of a collapse of the substrate and the catalyst deactivation and the resulting restriction escape severe. Vehicles equipped with OBD OBD-II are designed to alert the driver to a state of failures by flashing the check engine light on the dashboard.
Emissions regulations vary considerably from one jurisdiction to another. In North America, most spark ignition engines over 25 hp brake (19 kW) output built after 1 January 2004, is equipped with three-way catalysts. In Japan, came to a similar regulatory framework in force January 1, 2007, while the EU has focused on the regulation limiting the production of pollutants, without specifying a particular technology will be used begins with the Euro 1 regulations in 1992 and is gradually becoming more stringent in future years. Most car engines ignition in North America were equipped with catalytic converters since the mid-1970s, and the technology used in non-automotive applications are generally based on automotive technology.
Most of the pollution of a car that happens to put out the first five minutes before the "Catalytic Converter Recycling" is heated sufficiently. In 1999, BMW introduced the "Catalytic Converter Recycling" Electrical, the flagship sedan E38 750iL. Coils within the catalyst composition is heated with electricity as soon as start the engine when the "Catalytic Converter Recycling" to operating temperature much faster than conventional catalysts to provide clean cold starting and low emissions vehicles (LEV) are met. Environmental catalysts have proven to be reliable and efficient way to reduce harmful emissions.
If the sulfur passes over a catalyst, it can be further oxidized in the catalyst, which can be further oxidized to SO2 SO3. Sulfur oxides are precursors of sulfuric acid, an essential component of acid rain. Although it is possible to add substances such as vanadium catalyst washcoat to the fight against the formation of sulfur dioxide, reducing the effectiveness of the addition of catalyst. The most effective solution is to refine fuel at the refinery to produce ultra low sulfur content. Regulations in Japan, Europe and North America close to limit the amount of sulfur allowed in fuels. But at the cost of production of clean fuels, it is impractical for use in many developing countries. As a result, suffer from cities in countries with high levels of traffic to acid rain that damage the stone and wood buildings and damage local ecosystems.
The requirement for an internal combustion engine equipped with a three-way "Catalytic Converter Recycling" to run at the stoichiometric point means it is less effective if it was running lean. Thus, there is an increasing amount of fossil fuel consumption and emissions of carbon dioxide the vehicle. But the NOx control on lean burn engines is problematic and requires special lean NOx catalysts to meet U.S. emissions.
Some early designs converters severely restricted the flow of exhaust gases, which have adversely affected vehicle performance, driveability and fuel economy. Because carbs have been used can not precisely control air-fuel mixture, which could overheat and ignite flammable materials in the car. Elimination of a modern "Catalytic Converter Recycling" in the new state will slightly increase the performance of the vehicle without retuning, but its removal or continues.The exhaust section where it can be replaced by a converter welded straight pipe section or a section flange of the test drive off road legal can be replaced by a drive equipped in the same section to suppress legal road use, or the emissions test. In the United States and many other countries it is illegal to remove or disable a "Catalytic Converter Recycling" for any other reason than its replacement.
Several jurisdictions, the laws now on the train to diagnostic monitor the activities and conditions of the release control system, including the "Catalytic Converter Recycling". OBD systems take many forms. Temperature sensors are used for two purposes. The first is a warning, usually two-way catalytic converters, as is still sometimes used on LPG forklifts. Function of the sensor is to warn the temperature of the catalyst than the safety limit of 750 ° C. NOx sensors are very expensive and are generally used only when the diesel engine is equipped with a catalyst, selective catalytic or NOx absorber to the feedback system. SCR system can be installed on one or two sensors. When a sensor is mounted on the pre-catalyst, when two are installed the other is a post-catalyst. They are used for the same reasons and in the same way as the oxygen sensor - the only difference is the substance to be monitored.
Although catalytic converters are effective in "removing oil and other harmful emissions", do not solve the underlying problem created by the combustion of fossil fuels. Besides water, the main product of combustion engine exhaust gases - with a "Catalytic Converter Recycling" or not - is carbon dioxide (CO2). Carbon dioxide produced by fossil fuels is one of the emissions of greenhouse gases reported by the Intergovernmental Panel on Climate Change (IPCC) of being a most likely cause of global warming. In addition, the U.S. EPA said catalyst is an important and growing cause of global warming due to the release of nitrous oxide (N2O) emission of greenhouse gases over 300 times more potent than carbon dioxide. "Catalytic Converter Recycling" production requires palladium or platinum.
The oxygen sensor is the basis for the system of closed loop control of a spark ignited rich burn engine, but it is also used for diagnostics. A second oxygen sensor is mounted after the "Catalytic Converter Recycling" to monitor the levels of O2. On-board computer makes comparisons between the readings of two sensors. If both sensors show the same output, the computer recognizes that the catalyst is either not working or has been removed and operate a check engine light and engine performance delay. Simple oxygen sensor simulators" have been developed to work around this problem by simulating the change through the catalyst with the plans and pre-assembled equipment available on the Internet, although it is not legal for road use, they have been used with mixed results. Similar arrangements apply an offset of the sensor signals to the motor driving more fuel-economic lean, which can damage the engine or "Catalytic Converter Recycling".
Due to the external situation and the use of precious metals, including precious platinum, palladium and rhodium, the converters are a target for thieves. The problem is particularly common in Toyota trucks and late model sport utility vehicles, due to its high ground clearance and easily remove the bolt on catalytic converters. Soldiers in the converters are also at risk of theft of cars and trucks, as it can be removed easily. Removing the drive flight may inadvertently damage the wiring of the car or the fuel line leading to dangerous consequences. Increased costs of metal in the United States in recent years have resulted in a significant increase in the number of incidents of theft converter, which can cost up to $ 1,000 to replace it.
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