How The Most Hated Auto Part Changed The World

this episode is brought to you by brilliant according to the Environmental Protection agency's estimate in 2019 seven percent of the light duty vehicles in the United States did not comply with their mandated vehicle emissions regulations even more astonishing is the fact that one specific component on these vehicles account for about 68 of these compliance failures for many of that seven percent this light represents a repair bill that can span anywhere from 900 to over twenty seven hundred dollars depending on the vehicle and at the heart of this statistic is a mandated component that seemingly adds no benefit to the performance of the vehicle it's fitted to the catalytic converter though the catalytic converter has become the primary mechanism of the automobile industry for controlling exhaust emissions in internal combustion engines its origin is a byproduct of industrialization as a whole during the turn of the 20th century the smog created in urban areas by Factory Smoke Stacks triggered the first concerns for air quality as the automobile and the internal combustion engine became more abundant their impact on air quality grew more worrisome during the 1940s in the United States the growing problem of urban smog specifically in the Los Angeles area prompted the French mechanical engineer Eugene hujri to take interest in the problem who drew was an expert in catalytic oil refining and had developed techniques for catalytically refining heavy liquid tars into Aviation gasoline these methods were instrumental to U.S wartime Aviation field production during World War II following World War II hoodri founded a company called oxycatalyst applying his expertise to the air pollution problem his device called a catalytic converter or cat was initially intended for industrial use but would then be adapted for gasoline engines eventually resulting in a patented catalytic converter designed for automotive use hugeur's design worked by flowing exhaust gases through a chemical structure with a high surface area coated in a catalyst the Catalyst would induce a chemical reaction in the exhaust gases causing the primary pollutants to oxidize into less harmful chemicals the fundamentals of this design would carry forward to Modern catalytic converters as a greater understanding of air pollution would bring about drastic regulatory changes the exhaust gases of all internal combustion engines used on vehicles is composed primarily of three constituent gases nitrogen carbon dioxide and water vapor in lean operating modes of gasoline engines and in diesel engines oxygen is also present diesel engines by Design generally operate with excess air which always results in exhausted oxygen especially at low engine loads the nitrogen and oxygen are primarily pastors of atmospheric gases while carbon dioxide and water vapor are the direct products of the combustion process depending on the engine type and configuration these harmless gases form 98 to 99 of an engine's exhaust however the remaining one to two percent of combustion products comprises thousands of compounds all of which to some degree create air pollution the primary components of these pollutants carbon monoxide and nitrogen oxides are formed within the highly reactive high temperature flame zone of the combustion cycle while unburned and partially oxidized hydrocarbons tend to form near the cylinder walls where the combustion flame is quenched particulate matter especially in diesel engines are also produced in the form of soot in addition to this engine exhaust also contains partially burnt lubricating oil and Ash from Metallica additives in the lubricating oil and wear Metals Beyond this a myriad of Trace compounds are also present for decades it was not fully understood how these exhaust products created smog especially during bright sunny summer months finally in 1948 after collecting samples from the polluted air of Los Angeles flavor chemist Ari haugensmith was able to identify ozone as a primary component of smog from this Hagen Smith discovered that nitrogen oxides from Automotive exhausts and gaseous hydrocarbons from both vehicles and Industrial processes when exposed to sunlight would form form peroxy acyl nitrates and ozone this process is known as photochemical smog additionally some of the sulfur dioxide and nitrogen oxides from exhaust gases eventually are oxidized in the troposphere to nitric acid and sulfuric acid which when mixed with water form the primary components of acid rain smog particularly in dense Urban regions is a major health hazard ground level ozone sulfur dioxide nitrogen dioxide and carbon monoxide are especially harmful to senior citizens children and people with health and lung conditions the peroxy acyl nitrates created in the atmosphere are also powerful respiratory and irritants several major Studies have also found links between mortality and the presence of smog one such study published in nature magazine found that over a four year period smog episodes in the city of Janan in Eastern China were associated with a 5.87 percent increase in the rate of overall mortality in 1970 the United States passed the clean year act which required all vehicles to cut their emissions by 75 percent in only five years one of the most significant objectives of the cleaner Act was the removal of the anti-knock agent tetraethyl-led from most types of gasoline up until this point lead and fuel had prevented the use of catalytic converters on vehicles it tended to cake on the operating surfaces of a catalytic converter rendering it ineffective with lead now removed from Gasoline by 1975 the first widespread use of catalytic converters and vehicles began in the United States modern Automotive catalytic converters are composed of a steel housing containing a catalyst Support called a substrate that's placed in line with an engine's exhaust stream because the Catalyst requires a temperature of over 450 degrees Celsius to function they are generally placed as close to the engine as possible to promote rapid warm-up and heat retention on early catalytic converters the Catalyst media was made of pallets placed in a packed bed these early designs were restrictive sounded terrible and wore out easily during the 1980s this design was superseded by a ceramic-based honeycomb monolithic substrate coated in a catalyst the honeycomb structure used is typically cubic in nature these new cores offer better flow and because of their much larger surface area exposed more Catalyst material to the exhaust stream the ceramic substrate used is primarily made of a synthetic mineral known as cordurite during the manufacturing process the corduroid crystals are purposely aligned along one axis in order to resist cracking from the thermal cycling of Automotive use in order to disperse the catalytic material on the substrate it's suspended within an aluminum oxide-based wash coat designed to form a rough irregular surface this is done to further increase the catalytically active surface area as well as to prevent sintering of the catalytic metal particles at temperatures above 1000 degrees Celsius the Catalyst material used is generally a mix of three precious metals from the Platinum Group Platinum Palladium and rhodium the exact composition used is dependent on the engine displacement and the type of fuel used each metal covers one specific type of reaction rhodium is used as a reduction Catalyst Palladium is an oxidation Catalyst and platinum is used both for reduction and oxidation the first generation of Automotive catalytic converters used up until 1981 worked only by oxidation these were known as two-way converters as they could only perform two simultaneous reactions the oxidation of carbon monoxide to carbon dioxide and the oxidation of hydrocarbons to carbon dioxide and water by 1981 the three-way catalytic converters had superseded their two-way predecessor in the United States and Canada many other countries would also adopt similar stringent vehicle emission regulations making their use now a requirement three-way catalytic converters induce chemical reactions that reduce nitrogen oxide to harmless nitrogen this reaction can occur with either carbon monoxide hydrogen or hydrocarbons within the exhaust gas in order to support the competing reactions Sirius zirconia is added to three-way catalytic converters allowing them to store and release oxygen between them while three-way catalytic converters are more efficient at removing pollutants their effectiveness is highly sensitive to the air fuel mixture ratio for gasoline combustion this ratio is between 14.6 and 14.8 Parts air to one part fuel furthermore they need to oscillate between lean and Rich mixtures within this band in order to keep both reduction and oxidation reactions running because of this requirement computer-controlled closed-loop electronic fuel injection is required for their effective use when the combustion process is made lean there is more oxygen than is required this causes the reaction to favor the oxidation of carbon monoxide and hydrocarbons excess oxygen is also stored by the serious zirconia during the state when the system Cycles back to running rich there is more fuel than needed and the reaction now favors the reduction of nitrogen oxides because the oxygen in the exhaust stream is now reduced the oxygen stored within the Syria zirconia begins to release stimulating the oxidation reaction these reactions operate at a constant imbalance resulting in the system never achieving 100 efficiency furthermore too lean of a mixture can cause oxidation damage to the reduction Catalyst while too rich of a condition renders the oxidation reaction ineffective on diesel engines the damaging effect of the excess oxygen in their combustion process limits them to two-way catalytic converters nitrogen oxides are typically mitigated with other systems such as exhaust gastric circular relation and as of 2010 the use of ammonia to reduce nitrogen oxides to nitrogen known as selective catalytic reduction the ammonia is introduced to the catalytic system by the injection of a urea solution called diesel exhaust fluid into the exhaust stream additionally newer diesel engines are also fitted with diesel particulate filters to supplement their catalytic converters because air fuel ratios are so critical to three-way catalytic converters a mechanism to sense this becomes critical to their efficacy known as an oxygen sensor or a Lambda sensor these electronic devices measure how rich or lean combustion is within a narrow band of air fuel ratio from the oxygen present in the exhaust stream typically this band aligns with the efficiency zone of the catalytic converter oxygen sensors provide a feedback signal to the fuel injection system creating a closed loop in which it can closely oscillate lean and Rich conditions in order to maximize catalytic converter efficiency a more sophisticated variant known as a wideband air fuel sensor is sometimes used instead to further refine control of the air fuel ratio an oxygen sensor is also used to verify the operational efficiency of a catalytic converter by comparing the oxygen level Downstream of the catalytic converter against the sensor Upstream of it this mechanism is a key feature of the OBD1 and OBD2 onboard diagnostic standard which constantly monitors the functionality of the vehicle's emission control system alerting faults through a check engine light it's estimated that on average the Flow Restriction caused by a modern catalytic converter system reduces Peak engine power by roughly one percent and in exchange the EPA estimates that the introduction of catalytic converters and other improvements in air quality have saved more than one hundred thousand lives and has led to a 40 percent reduction of carbon monoxide emitted by cars trucks and motorcycles it took careful scientific observation to connect the dots between cause and effect with air pollution ultimately leading to the catalytic converter as a solution the scientific approach allowed new ideas to be combined with existing Technologies to solve a difficult problem and with brilliant building this scientific mindset to solve design challenges has never been easier Brilliance is my go-to tool for diving head first into learning A New Concept in stem it's a website an app built off the principle of active problem solving because to truly learn something it takes more than just watching it you have to experience it brilliant is constantly revamping their courses to offer even more interactivity and with their recently updated scientific thinking course you'll be able to examine the world around us Through The Eyes of scientific principles in this course you'll dispense with number crunching and Mathematics in search of something more useful physical insights brilliant helps you develop this scientific intuition using interactive 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Channel: New Mind

Views: 280,733

Keywords: catalytic converter, how a catalytic converter works, smog, photochemical smog formation, photochemical smog and acid rain, acid rain, engine exhaust system, engine exhaust, clean air act 1970, clean air act explained, lead in gasoline, twc, three-way catalytic converter, three-way catalyst, three-way catalyst converter bank 1, how an oxygen sensor works, o2 sensor, nitrogen oxide pollution, nitrogen oxide, nitrogen oxide effects, carbon monoxide poisoning, ozone, air pollution

Id: gYzzdPBCrxw

Length: 13min 37sec (817 seconds)

Published: Wed Dec 21 2022