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Catalytic converter on a Dodge Ram Van.
Catalytic converter on a Dodge Ram Van. The Dodge Ram Van was a Full-size Van marketed under the Dodge brand by the Chrysler Corporation and later DaimlerChrysler
Catalytic converter on a Saab 9-5.
Catalytic converter on a Saab 9-5. The Saab 9-5 is an Executive car produced by the Swedish automobile maker Saab.

A catalytic converter (colloquially, "cat" or "catcon") is a device used to reduce the toxicity of emissions from an internal combustion engine. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a First widely introduced on series-production automobiles in the US market for the 1975 model year to comply with tightening EPA regulations on auto exhaust, catalytic converters are still most commonly used in motor vehicle exhaust systems. Mass production (also called flow production, repetitive flow production, series production, or serial production) is the production of The United States of America —commonly referred to as the Year 1975 ( MCMLXXV) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. The model year of a product is a number used to describe approximately when a product was produced Exhaust gas is Flue gas which occurs as a result of the Combustion of fuels such as Natural gas, Gasoline /petrol Diesel, Fuel Catalytic converters are also used on generator sets, forklifts, mining equipment, trucks, buses, trains, and other engine-equipped machines. In Electricity generation, an electrical generator is a device that converts Mechanical energy to Electrical energy, generally using Electromagnetic This article is about the semi-truck For the North American use of the word see Pickup truck. A train is a connected series of vehicles that move along a track ( Permanent way) to transport freight or passengers from one place to another A catalytic converter provides an environment for a chemical reaction wherein toxic combustion by-products are converted to less-toxic substances. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called

Contents

Functions

Three-way catalytic converters

A three-way catalytic converter has three simultaneous tasks:

  1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
  2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
  3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable This is between 14. 8 and 14. 9 parts air to 1 part fuel, by weight, for gasoline (the ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels). Autogas is the common name for Liquified petroleum gas (LPG when it is used as a Fuel in Internal combustion engines in Vehicles. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation. If an engine could be operated with infinitesimally small oscillations about the stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.

Since 1981, three-way catalytic converters have been at the heart of vehicle emission control systems in North American roadgoing vehicles, and have been used on "large spark ignition" (LSI) engines since 2001 in California, and from 2004 in the other 49 states. A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder An ignition system is a system for igniting a fuel-air mixture LSI engines are used in forklifts, aerial boom lifts, ice resurfacing machines and construction equipment. The converters used in those types of machines are three-way types, and are designed to reduce combined NOx+HC emissions from 12 gram/BHP-hour to 3 gram/BHP-hour or less, as mandated by the United States Environmental Protection Agency's (EPA) 2004 regulations. Automobile emissions control covers all the technologies that are employed to reduce the Air pollution -causing emissions produced by Automobiles Exhaust emissions For other uses of the words gram or gramme see Gram (disambiguation. A further drop to 2 gram/BHP-hour of NOx+HC emissions is mandated in 2007 (note: NOx is the industry standard short form for nitric oxide (NO) and nitrogen dioxide (NO2) both of which are smog precursors. Nitric oxide or nitrogen monoxide is a Chemical compound with Chemical formula N[[Oxygen O]] Nitrogen dioxide is the Chemical compound with the formula N[[Oxygen O]]2 HC is the industry short form for hydrocarbons). The EPA intends to introduce emissions rules for stationary spark ignition engines, to take effect in January 2008. [1]

Two-way catalytic converters

A two-way catalytic converter has two simultaneous tasks:

  1. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
  2. Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

This type of catalytic converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Water is a common Chemical substance that is essential for the survival of all known forms of Life. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. They were also used on spark ignition (gasoline) engines in USA market automobiles up until 1981, when they were replaced by three-way converters due to regulatory changes requiring reductions on NOx emissions. The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric Reduction of the NOx emissions requires an additional step. Platinum catalysis can be used. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78

Instead of catalysis, for diesel engines a true reactant, ammonia pyrolyzed in situ from urea, can be used to reduce the NOx into nitrogen, see AdBlue. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor In situ (ɪn siːˈtuː is a Latin phrase meaning in the place. Urea is an Organic compound with the Chemical formula ( N[[hydrogen H]]22 C[[oxygen O]] AdBlue is the registered trademark for AUS32 (Aqueous Urea Solution 32

The regulations regarding hydrocarbons vary according to the engine regulated, as well as the jurisdiction. In Law, jurisdiction (from the Latin ius iuris meaning "law" and dicere meaning "to speak" is the practical Authority In some cases, "non-methane hydrocarbons" are regulated, while in other cases, "total hydrocarbons" are regulated. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Technology for one application (to meet a non-methane hydrocarbon standard) may not be suitable for use in an application that has to meet a total hydrocarbon standard. Methane is not toxic, but is more difficult to break down in a catalytic converter, so in effect a "non-methane hydrocarbon" standard can be considered to be looser. Since methane is a greenhouse gas, interest is rising in how to eliminate emissions of it. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared

Catalyst poisoning and deactivation

Catalyst poisoning occurs when the catalytic converter is exposed to exhaust containing substances that coat the working surfaces, encapsulating the catalyst so that it cannot contact and treat the exhaust. Catalyst poisoning refers to the effect that a Catalyst can be 'poisoned' if it reacts with another compound that bonds chemically (similar to an inhibitor The most notable contaminant is lead, so vehicles equipped with catalytic converters can only be run on unleaded gasoline. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly This is because if a 'leaded' fuel (a fuel with lead content) is burnt there will be a residue of lead which can damage the catalytic converter. Other common catalyst poisons include manganese primarily from the gasoline additive MMT, and silicon which can enter the exhaust stream if the engine has a leak allowing coolant into the combustion chamber. Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Methylcyclopentadienyl manganese tricarbonyl (MMT is an Organometallic compound with the formula (CH3C5H4Mn(CO3 Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Antifreeze is a Cryoprotectant used in Internal combustion engines and for many other heat transfer applications such as electronics cooling and Chillers Phosphorus is another catalyst contaminant. Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Although phosphorus is no longer used in gasoline, it (and zinc, another low-level catalyst contaminant) was until recently widely used in engine oil antiwear additives such as ZDDP. Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 AW additives, or antiwear additives, are additives for Lubricants to prevent metal-to-metal contact between parts of Gears EP additives Zinc dithiophosphates are a family of Coordination compounds that feature zinc bound to the anion of dithiophosphoric acid Beginning in 2006, a rapid phaseout of ZDDP in engine oils was begun.

Depending on the contaminant, catalyst poisoning can sometimes be reversed by running the engine under a very heavy load for an extended period of time. The increased exhaust temperature can sometimes liquefy or sublime the catalytic contaminant, removing it from the catalytic surface. However, removal of lead deposits in this manner is usually not possible due to lead's high boiling point. In particularly bad cases of catalytic lead poisoning, the catalytic converter may actually become completely plugged with lead residue.

Any condition that causes abnormally high levels of unburned hydrocarbons to reach the converter will tend to significantly elevate its temperature, bringing the risk of a meltdown of the substrate and resultant catalytic deactivation and severe exhaust restriction. Vehicles equipped with OBD-II diagnostic systems are designed to alert the driver of a misfire condition, along with other malfunctions, by means of the "Check Engine" light on the dashboard. On-Board Diagnostics, or OBD, in an Automotive context is a generic term referring to a vehicle's self-diagnostic and reporting capability

Technical details

Cross section of a Metal-core Converter
Cross section of a Metal-core Converter

The catalytic converter consists of several components:

  1. The core, or substrate. In modern catalytic converters, this is most often a ceramic honeycomb, however stainless steel foil honeycombs are also used. The word ceramic is derived from the Greek word κεραμικός ( keramikos) In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 The purpose of the core is to "support the catalyst" and therefore it is often called a "catalyst support". The ceramic substrate was invented by Rodney Bagley, Irwin Lachman and Ronald Lewis at Corning Glass for which they were inducted into the National Inventors Hall of Fame in 2002. Irwin Lachman is a scientist and artist born in Brooklyn NY in 1930 and who grew up in Jersey Homesteads, NJ (now called Roosevelt Corning Incorporated ( is an American manufacturer of Glass, Ceramics and related materials primarily for industrial and scientific applications The National Inventors Hall of Fame is an organization that recognizes Inventors and invention everywhere promotes creativity and advances the spirit of innovation and entrepreneurship See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar.
  2. The washcoat. In an effort to make converters more efficient, a washcoat is utilized, most often a mixture of silica and alumina. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide The washcoat, when added to the core, forms a rough, irregular surface which has a far greater surface area than the flat core surfaces, which is desirable to give the converter core a larger surface area, and therefore more places for active precious metal sites. The catalyst is added to the washcoat (in suspension) before application to the core.
  3. The catalyst itself is most often a precious metal. Platinum is the most active catalyst and is widely used. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 However, it is not suitable for all applications because of unwanted additional reactions and/or cost. Palladium and rhodium are two other precious metals that are used. Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Rh redirects here For other uses see Rh (disambiguation Rhodium (ˈroʊdiəm is a Chemical element with the symbol Platinum and rhodium are used as a reduction catalyst, while platinum and palladium are used as an oxidization catalyst. Cerium, iron, manganese and nickel are also used, though each has its own limitations. Cerium (ˈsɪəriəm is a Chemical element with the symbol Ce and Atomic number 58 Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Nickel is not legal for use in the European Union (due to reaction with carbon monoxide). Nickel carbonyl ( IUPAC name tetracarbonylnickel) is a colorless Organometallic complex that is a versatile reagent first described in While copper can be used, its use is illegal in North America due to the formation of dioxin. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Not to be confused with Dioxane or Digoxin. Dioxin is a heterocyclic, organic, antiaromatic compound

Conventional spark ignition engines

Catalytic converters are used on spark ignition (gasoline; liquified petroleum gas (LPG); flexible fuel vehicles burning varying blends of E85 and gasoline; compressed natural gas (CNG)) engines; and compression ignition (diesel) engines. Liquefied petroleum gas (also called LPG, GPL, LP Gas, or Autogas) is a mixture of Hydrocarbon Gases used as a Fuel A flexible-fuel vehicle (FFV or dual-fuel vehicle ( Colloquially called a flex-fuel vehicle) is an alternative fuel Automobile or E85 is an Alcohol fuel mixture that typically contains a mixture of up to 85% denatured fuel ethanol and Gasoline or other hydrocarbon (HC by Compressed Natural Gas (CNG is a Fossil fuel substitute for Gasoline (petrol Diesel, or Propane Fuel. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum

For spark ignition engines, the most commonly used catalytic converter is the three-way converter which converts the three main pollutants of concern — CO, HC, and NOx— to less-toxic substances. The control of NOx involves a reduction process that releases oxygen and the control of CO and HC involves an oxidation process that consumes oxygen. Therefore, a 3-way converter contains two catalyst-coated stages: The first catalyst stage encountered by the exhaust is for reduction of NOx, which produces oxygen employed by the second stage to oxidize CO and HC. 3-way converters work most efficiently with exhaust from engines operated on a stoichiometric air-fuel mixture. Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable Generally, such engines are equipped with closed-loop feedback fuel mixture control employing one or more oxygen (lambda) sensors. Control theory is an interdisciplinary branch of Engineering and Mathematics, that deals with the behavior of Dynamical systems The desired output An oxygen sensor, or lambda sensor is an electronic device that measures the proportion of Oxygen (O2 in the gas or liquid being analyzed While a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Since NOx emissions are now regulated throughout the world, open-loop fuel systems are obsolete in many jurisdictions. Closed-loop maintenance of the stoichiometric air-fuel ratio is most often attained by means of an engine management system with computer-controlled fuel injection, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used during the transition to fuel injection. An engine control unit (ECU is an Electronic control unit which controls various aspects of an Internal combustion engine 's operation Fuel injection is a system for mixing fuel with air in an Internal combustion engine. A carburetor (North American spelling or carburettor ( Commonwealth spelling) is a device that blends air and Fuel for an Internal Within a narrow ratio band surrounding stoichiometry, conversion of all three pollutants is very complete, sometimes approaching 100%. However, outside of that band, conversion efficiency falls off very rapidly. Two-way (or oxidation) converters act only to control CO and HC, and have therefore been abandoned on conventional spark ignition engines in most jurisdictions due to an inability to control NOx.

A three-way catalyst reduces emissions of CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) simultaneously when the oxygen level of the exhaust gas stream is below 1. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric 0%, though performance is best at below 0. 5% O2. Unwanted reactions, such as the formation of H2S (hydrogen sulfide) and NH3 (ammonia), can occur in the three-way catalyst. Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Formation of each can be limited by modifications to the washcoat and precious metals used. It is, however, difficult to eliminate these side products entirely.

For example, when control of H2S (hydrogen sulfide) emissions is desired, nickel or manganese is added to the washcoat - both substances act to block the adsorption of sulfur by the washcoat. H2S 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. For "lean burn" spark ignition engines (e. g. compressed natural gas, or compressed natural gas with diesel fuel pilot injection), an oxidation catalyst is used in the same manner as in a compression ignition engine.

Recently, many systems have used a pre-catalyst in the system to reduce startup emissions and burn off hydrocarbons from the extra-rich mixture used in a cold engine. Upstream and downstream parts are now often separated in the system to provide an optimum temperature and space for extra oxygen sensors. The converter needs to be placed close enough to the engine to quickly reach operating temperature but far enough away to avoid heat damage.

Many three-way catalytic converters utilize an air injection tube between the first (NOx reduction) and second (HC and CO oxidation) biscuits of the converter. This tube is fed by either an air pump or by an aspirator. Theory and origins Secondary air injection (commonly air injection, colloquially smog pump, trademark Air Injection Reactor) is an Automobile Theory and origins Secondary air injection (commonly air injection, colloquially smog pump, trademark Air Injection Reactor) is an Automobile The injected air provides oxygen for the catalyst's oxidizing reaction. These systems also sometimes include an upstream air injector to admit oxygen to the exhaust system before it reaches the catalytic converter. This precleans the extra-rich exhaust from a cold engine, and helps bring the catalytic converter quickly up to operating temperature.

Most newer systems do not employ air injection. Instead, they provide a constantly varying mixture that quickly and continually cycles between lean and rich to keep the first catalyst (NOx reduction) from becoming oxygen loaded, and to keep the second catalyst (CO oxidization) sufficiently oxygen-saturated. They also utilize several oxygen sensors to monitor the exhaust, at least one before the catalytic converter for each bank of cylinders, and one after the converter. Some systems contain the reduction and oxidation functions separately rather than in a common housing.

Diesel engines

For compression ignition (i. e. , Diesel) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum The catalyst uses excess O2 (oxygen) in the exhaust gas stream to oxidize CO (Carbon Monoxide) to CO2 (Carbon Dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible particulates (soot), however they are incapable of reducing NOx as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Soot (ˈsʊt is a general term that refers to the black impure carbon particles resulting from the incomplete combustion of a hydrocarbon

To reduce NOx on a compression ignition engine it is necessary to change the exhaust gas - two main technologies are used for this - selective catalytic reduction (SCR) and NOx (NOx) traps (or NOx Adsorbers). Selective catalytic reduction ( SCR) is a means of converting nitrogen oxides, also referred to as {{chem|NO|x}} with the aid of a Catalyst into A NOx adsorber or NOx trap (also called Lean NOx trap, abbr LNT is a device that is used to reduce Oxides of nitrogen

Another issue for diesel engines is particulate (soot). This can be controlled by a soot trap or diesel particulate filter (DPF), as catalytic converters are unable to affect elemental carbon (however they will remove up to 90% of the soluble organic fraction). A clogging soot filter creates a lot of back pressure decreasing engine performance. However, once clogged, the filter goes through a regeneration cycle where diesel fuel is injected directly into the exhaust stream and the soot is burned off. After the soot has been burned off the regeneration cycle stops and injection of diesel fuel stops. This regeneration cycle should not affect performance of the engine.

All major diesel engine manufacturers in the USA (Ford, Caterpillar, Cummins, Volvo, MMC) starting January 1, 2007 are required to have a catalytic converter and a soot filter inline, as per new United States Environmental Protection Agency (EPA) regulation. [2]

Oxygen storage in three-way converters

In order to oxidize CO and HC, the catalytic converter also has the capability of storing the oxygen from the exhaust gas stream, usually when the air fuel ratio goes lean. When insufficient oxygen is available from the exhaust stream the stored oxygen is released and consumed. This happens either when oxygen derived from NOx reduction is unavailable or certain maneuvers such as hard acceleration enrich the mixture beyond the ability of the converter to compensate.

Note that diesel catalysts do not use this feature as there is sufficient O2 in the exhaust gas stream to handle the CO & HC reductions needed.

Regulations

Emissions regulations vary considerably from jurisdiction to jurisdiction, as do what engines are regulated. In North America any spark ignition engine of over 19 kW (25 hp) power output built later than January 1, 2004 probably has a three-way catalytic converter installed. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. New Year See also New Year The Ancient Romans began their consular year on January 1st since 153 BC "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " In Japan a similar set of regulations came into effect January 1, 2007, while the European Union has not yet enacted analogous regulations. For a topic outline on this subject see List of basic Japan topics. New Year See also New Year The Ancient Romans began their consular year on January 1st since 153 BC Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in Most automobile spark ignition engines in North America have been fitted with catalytic converters since the mid-1970s and the technology used in non-automotive applications is generally based on automotive technology. This article is about the Decade 1970-1979 For the Year 1970 see 1970.

Diesel engine regulations are similarly varied, with some jurisdictions focusing on NOx (nitric oxide and nitrogen dioxide) emissions and others focusing on particulate (soot) emissions. This can cause problems for the engine manufacturers as it may not be economical to design an engine to meet two sets of regulations.

An important issue is that fuel quality varies widely from place to place, even within jurisdictions, as do the regulations covering fuel quality. In North America, Europe, Japan, and Hong Kong both gasoline and diesel fuel are highly regulated and there are campaigns under way to regulate CNG and LPG as well. In most of Asia and Africa this is not true - in some places sulfur content of the fuel can reach 20,000 parts per million (2%). Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Any sulfur in the fuel may be oxidized to SO2 (sulfur dioxide) or even SO3 (sulfur trioxide) in the combustion chamber. Sulfur trioxide (also spelled sulphur trioxide) is the chemical compound with the formula SO3 A combustion chamber is the part of an Engine in which Fuel is burned If sulfur passes over a catalyst it may be further oxidized in the catalyst, i. e. (SO2 may be further oxidized to SO3). Sulfur oxides are precursors to sulfuric acid, a major component of acid rain. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure While it is possible to add substances like vanadium to the catalyst wash coat to combat sulfur oxide formation, this will reduce the effectiveness of the catalyst—the best solution is further refinement of the fuel at the refinery to remove the sulfur. Vanadium (vəˈneɪdiəm is a Chemical element that has the symbol V and Atomic number 23 Regulations in Japan, Europe and —by 2007— North America tightly restrict the amount of sulfur permitted in motor fuels. However, the expense is such that this is not practical in many developing countries. As a result cities in these countries with high levels of vehicular traffic suffer damage to buildings due to acid rain eating away the stone/woodwork, and acid rain has deleterious effects on the local ecosystem.

Regulatory agencies

The agencies charged with regulating engine emissions vary from jurisdiction to jurisdiction, even in the same country. For example, in the United States, overall responsibility belongs to the EPA, but due to special requirements of the State of California, emissions in California are regulated by the Air Resources Board. The United States of America —commonly referred to as the California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The California Air Resources Board, also known as ( CARB) is the "clean air agency" in the Government of California. In Texas, the Texas Railroad Commission is responsible for regulating emissions from LPG fueled rich burn engines (but not gasoline fueled rich burn engines). The Railroad Commission of Texas is the state agency that regulates the oil and gas industry, gas utilities pipeline safety safety in the Liquefied petroleum

Criticism

Environmental impact

Catalytic converters have proven to be reliable devices and have been successful in reducing noxious tailpipe emissions. The California Air Resources Board, also known as ( CARB) is the "clean air agency" in the Government of California. Environment Canada (EC, legally incorporated as the Department of the Environment under the Department of the Environment Act ( R The Railroad Commission of Texas is the state agency that regulates the oil and gas industry, gas utilities pipeline safety safety in the Liquefied petroleum Transport Canada is the department within the government of Canada which is responsible for developing Regulations, Policies and services However, they may have some adverse environmental impacts in use:

Catalytic converter theft

Due to the exterior location and the use of valuable precious metals including platinum, palladium, and rhodium, converters are a target for thieves. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Rh redirects here For other uses see Rh (disambiguation Rhodium (ˈroʊdiəm is a Chemical element with the symbol The problem is especially common among late-model Toyota trucks and SUVs, due to their high ground clearance and easily-removed bolt-on catalytic converters. (pronounced) is a Multinational corporation headquartered in Japan, and is currently the world's largest Automaker. This article is about the semi-truck For the North American use of the word see Pickup truck. A sport utility vehicle ( SUV) is a generic marketing description for a rugged automotive vehicle similar to a Station wagon but built on a light-truck chassis Welded-in converters are also at risk of theft from SUVs and trucks, as they can be easily removed with a battery powered reciprocating saw. A reciprocating saw is a type of saw in which the cutting action is achieved through a push and pull reciprocating motion of the blade [3] [4]The saw removal of the converter can often inadvertently damage the car’s wiring or fuel line resulting in dangerous consequences. Rises in metal costs inside the United States during recent years have led to a large increase in theft incidents of the converter, encouraged in part by a resale price for converters that approaches two hundred dollars. [5]

Diagnostics

Various jurisdictions now legislate on-board diagnostics to monitor the effectiveness of the emissions control system, including the catalytic converter and such diagnostics are often included in aftermarket retrofit kits as a matter of course, even if legislation does not directly require them. Retrofitting refers to the addition of new technology or features to older systems

On-board diagnostics take several forms, depending upon the legislation and the type of emissions control product being monitored, the three main types are:

Temperature sensors

Temperature sensors are used for two purposes. A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument The first is as a warning system, typically on obsolete 2-Way catalytic converters such as are still sometimes used on LPG forklifts. The function of the sensor is to warn of temperature excursions above the safe operating temperature of 750°Celsius of the two-way catalytic converter. The Celsius Temperature scale was previously known as the centigrade scale. Note that modern catalytic converters are not as susceptible to temperature damage with many modern three-way platinum based converters able to handle temperatures of 900°C sustained. Temperature sensors are also used to monitor catalyst functioning - usually two sensors will be fitted, with one before the catalyst and one after to monitor the temperature rise over the catalytic converter core. For every 1% of CO in the exhaust gas stream the exhaust gas temperature will rise by 100°C.

Oxygen sensors

The Oxygen sensor or "lambda sensor" is the basis of the closed loop control system on a spark ignited rich burn engine, however it is also used for diagnostics. An oxygen sensor, or lambda sensor is an electronic device that measures the proportion of Oxygen (O2 in the gas or liquid being analyzed Oxygen sensors only work when at operating temperature, when they output a voltage based on the O2 level in the exhaust gas to the computer. Typically a single wire oxygen sensor will take 3-5 minutes to reach operating temperature. The more expensive heated sensors (3 to 5 wires) can reach operating temperature in 1 minute.

The simplest sort of diagnostic an oxygen sensor can perform is related to the closed loop control system. If the system makes a change to the air-fuel ratio based on oxygen sensor readings, and the readings do not change, the sensor will light an indicator on the instrument panel warning the operator that there is a problem with the vehicle. There is a delay before this happens - usually five minutes of engine operation. Most systems do not store the state, so turning off the engine and turning it back on will reset the system, and if the error is transient the light will not come back on. However, if the problem is recurring, the light will come on as soon as the sensor reaches operating temperature and a manufacturer-defined driving pattern known as a drive-trace is completed. Until this procedure has finished, the diagnostic computer will set a parameter called a readiness monitor to "unready". The readiness monitor system was implemented in order to ensure that diagnostic computers would not falsely report working emissions systems in vehicles whose computer's error memory had recently been cleared. Such diagnostics have been factory fitted to automobiles since 1985 in North America and factory fitted to off-road spark ignition engines since 2004.

The second sort of diagnostic is more complex and is a result of the California OBD-II rule (though temperature sensors are sometimes used for this). On-Board Diagnostics, or OBD, in an Automotive context is a generic term referring to a vehicle's self-diagnostic and reporting capability In vehicles with OBD-II, a second oxygen sensor is fitted after the catalytic converter to monitor the O2 levels. The on-board computer makes comparisons between the readings of the two sensors. If both sensors give the same output, the catalytic converter is non-functioning, and must be replaced. It will also spot less serious damage to a catalytic converter, such as the use of leaded racing fuel in an on-road vehicle.

NOx sensors

NOx sensors are extremely expensive and are generally only used when a compression ignition engine is fitted with a selective catalytic reduction converter, or a NOx adsorber catalyst in a feedback system. When fitted to an SCR system, there may be one or two sensors. When one sensor is fitted it will be pre-catalyst, when two are fitted the second one is post catalyst. They are utilized for the same reasons and in the same manner as an oxygen sensor - the only difference is the substance being monitored.

See also

References

  1. ^ Proposed Emission Standards Of Performance For Stationary Spark Ignition Internal Combustion Engines
  2. ^ Clean Diesel Trucks, Buses, and Fuel: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements | Heavy-Duty Highway Diesel Program | US EPA
  3. ^ Catalytic converter theft article
  4. ^ Newsweek An Exhausting New Crime Jan 9, 2008
  5. ^ MSNBC As precious metals prices soar, catalytic converters are targets for thieves Feb. 12, 2008

External links

Patents

Dictionary

catalytic converter

-noun

  1. (automotive) A chamber containing a finely divided platinum catalyst in which carbon monoxide and hydrocarbons from the exhaust are oxidized to carbon dioxide.
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