Catalytic converters
A catalytic converter is an essential component in internal combustion engines designed to reduce toxic emissions from vehicles. Developed in response to regulatory efforts by the Environmental Protection Agency (EPA) in the early 1970s, catalytic converters became standard in cars starting in 1975. These devices primarily function by converting harmful substances in exhaust gases, such as carbon monoxide (CO), nitrogen oxides (NOx), and unburnt hydrocarbons, into less harmful emissions like carbon dioxide (CO2) and nitrogen.
The effectiveness of catalytic converters has significantly contributed to improved air quality in urban areas, notably reducing smog in cities like Los Angeles over the decades. However, while they help minimize certain pollutants, catalytic converters also generate greenhouse gases, including CO2 and nitrous oxide (N2O), raising concerns about their environmental impact. Additionally, the rise in the use of these devices has historically led to increased incidents of theft due to the valuable precious metals used in their construction, such as platinum, palladium, and rhodium. Overall, catalytic converters play a critical role in balancing vehicle emissions and air quality while also presenting new challenges for society.
Catalytic converters
Definition
A catalytic converter is a device to reduce the amount of toxic emissions in the exhaust of an internal combustion engine. It was developed in response to efforts in the early 1970s by the Environmental Protection Agency (EPA) to tighten regulations on emissions from internal combustion engines. The 1975 model cars were produced with catalytic converters. The first converter, a two-way converter, oxidized carbon monoxide (CO) to carbon dioxide (CO2) and oxidized unburnt hydrocarbons to CO2 and water. The hydrocarbons were molecules of gasoline that escaped a car’s pistons without being burned. Beginning in 1981, also had a third component that reduced nitrogen oxides to nitrogen and oxygen.
Catalytic converters are composed of three parts. There is a core or substrate honeycomb constructed of either ceramic material or stainless steel. The honeycomb design provides maximum surface area. A washout of silica and alumina is added to the substrate to increase the surface area. The catalyst is a precious metal attached to the washout. Platinum or rhodium is usually used as the reducing catalyst, and platinum or palladium is usually used as the oxidizing catalyst.
Exhaust gas reaches the reducing catalyst first. Nitrogen oxides attach to the catalyst, and the reaction to separate nitrogen from oxygen is aided by the nitrogen being bound. After the oxygen is removed, nitrogen atoms can combine to form diatomic nitrogen gas. Carbon from the CO in the exhaust is held in the oxidizing area, where oxygen reacts with it to form CO2. Similarly, hydrocarbons are held to be oxidized to CO2 and water.
Significance for Climate Change
Catalytic converters drastically reduce the amount of nitrogen oxides, hydrocarbons, and carbon monoxide emitted into the atmosphere. Nitrogen oxides and hydrocarbons are two of the main reactants, along with sunlight, producing photochemical smog. The catalytic converter has been a major factor, along with reformed gasoline, in reducing smog in many places. For example, in 1975, the air in Los Angeles exceeded the ozone standard 192 out of 365 days. By 2005, Los Angeles air exceeded ozone standards on only twenty-seven days of the year. Los Angeles’s air quality improved consistently over the thirty years between 1975 and 2005. Smog in the city was cut by two-thirds. In 1977, the city experienced 121 stage 1 smog alerts, the most severe designation denoting a day when air quality is particularly unhealthy. In 1980, there were seventy-nine stage 1 smog alerts in Los Angeles, and there were only seven such alerts in 1996. The air quality in Los Angeles is a lot cleaner in the twenty-first century than it was in the 1980s. Still, air quality has remained a complicated issue for Los Angeles, which has seen its air quality begin to decline again. In 2019, 66 days were considered good air quality days, 213 were moderate, and 57 were unhealthy. By 2021, those numbers changed to 41 good air quality days, 228 moderate, and 70 unhealthy, and by 2023, the city had 41 good air quality days, 237 moderate, and 32 unhealthy.
Despite the upturn in bad air quality days in some urban areas in the early twenty-first century, there has been drastic improvement nationally since the final decades of the twentieth century. The deployment of catalytic converters is not the only factor in achieving this significant improvement in air quality. It is, however, a major factor. By reducing the smog-related emissions from motor vehicles, the catalytic converter prevented a great deal of pollutants from being released into the atmosphere. According to the EPA, in 2021 automobiles emitted approximately 99 percent less CO, hydrocarbons, and nitrogen oxides than did 1970 models.
The effects of catalytic converters have not all been positive, however. The devices oxidize CO and hydrocarbons, converting them to CO2. CO2 is a greenhouse gas (GHG) that contributes to global warming. The transportation industry is one of the major sources of CO2. In addition to transforming other pollutants into CO2, catalytic converters often reduce fuel efficiency, increasing a vehicle’s output of CO2 per kilometer. Moreover, nitrogen oxides are not always reduced completely to nitrogen gas by catalytic converters. Instead, they may be reduced to nitrous oxide (N2O), a GHG whose is three hundred times that of CO2. As the number of vehicles with catalytic converters has increased, the N2O in the atmosphere has also increased. As of 2022, according to the EPA, it constituted percent of the GHGs emitted from human activities.
Catalytic converters function well only after they are warmed up. Thus, they do not effectively reduce the emissions of the first gasoline burned after starting a motor vehicle. Catalytic converters can deteriorate if exposed to intense heat. Lead and some other elements will contaminate the catalyst. For this reason, it is illegal to use leaded gasoline in a vehicle with a catalytic converter. Contaminated and deteriorated converters may increase, rather than decrease, the pollution emitted from a car. Catalytic converters have helped clean the air of smog, but they have come to represent a new problem by generating GHGs.
The generation of GHGs from catalytic converters has not been the only negative consequence of the devices. Catalytic converters have had unforeseen economic and social consequences as thefts of the devices have skyrocketed to record highs. According to the National Insurance Crime Bureau, catalytic converter thefts rose from 16,660 in 2020 to 64,000 in 2022. Thieves targeted the devices for money, as rhodium, palladium, and platinum used in making the parts are highly valuable.
Bibliography
"Air Quality Days by Year for Los Angeles County, California." Los Angeles Almanac, www.laalmanac.com/environment/ev01b.php. Accessed 14 Jan. 2023.
Barboza, Tony. "Los Angeles Began 2020 with a Clear-Air Streak but Ended with Its Worst Smog in Decades." Phys.org, 7 Dec. 2020, phys.org/news/2020-12-los-angeles-began-clean-air-streak.html. Accessed 14 Jan. 2023.
Bode, H. Material Aspects in Automotive Catalytic Converters. Weinheim, Germany: Wiley-VCH, 2002.
"Catalytic Converter Thefts Skyrocket across the Nation." National Insurance Crime Bureau (NCIB), 10 May 2023, www.nicb.org/news/blog/catalytic-converter-thefts-skyrocket-across-nation-0. Accessed 13 Dec. 2024.
Guerin, Emily. "LA Explained: Smog." LAist, 3 Oct. 2018, laist.com/news/climate-environment/la-explained-smog. Accessed 14 Jan. 2023.
"History of Reducing Air Pollution from Transportation in the United States." EPA, 20 Aug. 2024, www.epa.gov/transportation-air-pollution-and-climate-change/history-reducing-air-pollution-transportation. Accessed 3 Dec. 2024.
Kubsh, Joseph Edward. Advanced Three-Way Catalysts. Warrendale, Pa.: Society of Automotive Engineers, 2006.
"Overview of Greenhouse Gases." EPA, 16 May 2022, www.epa.gov/ghgemissions/overview-greenhouse-gases. Accessed 27 Jan. 2023.
Society of Automotive Engineers. Advanced Catalysts for Emission Control. Warrendale, Pa.: Author, 2003.
Society of Automotive Engineers. Emission: Advanced Catalysts and Substrates, Measurement and Testing, and Diesel Gaseous Emissions. Warrendale, Pa.: Author, 2003.