How does a catalytic converter reduce emissions, and why are they stolen?

Numbers match the citations in the article. A working link isn't proof that a page supports a claim; check the quoted passage and date.

1. 1

   Catalytic converter (Wikipedia)

   WikipediaPublished Oct 13, 2026Checked Oct 15, 2026

   “A catalytic converter is an exhaust emission control device which converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually used with internal combustion engines fueled by gasoline (petrol), including lean-burn engines, and sometimes on kerosene heaters and stoves. The first widespread introduction of catalytic converters was in the United States automobile market. To comply with the US Environmental Protection Agency's stricter regulation of exhaust emissions, most gasoline-powered vehicles starting with the 1975 model year are equipped with catalytic converters. These "two-way" oxidation converters combine oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). "Three-way" converters, which also reduce oxides of nitrogen (NOx), were first commercialized by Volvo on the California-specification 1977 240 cars. When U.S.”

2. 2

   A novel method for linking reciprocating saw blades, suspected of being used for theft, to a stolen catalytic converter by using toolmarks comparison techniques.

   Journal of forensic sciences (Aronson et al.)Published Jan 31, 2025Checked Oct 15, 2026

   “A skilled thief can easily and quickly steal the catalytic converter by getting underneath the vehicle and, in a few moments, simply cut the exhaust pipes in front of and behind the catalytic converter using a common cutting tool, such as a reciprocating saw. Beyond the high price and the ease of committing the theft, police investigators experience difficulties finding forensic evidence that will incriminate the suspect. Furthermore, linking the cut items, such as the reciprocating saw, is not a simple challenge because of its mode of operation. The cyclic movement of the saw's blade, back and forth, removes a section of material. Therefore, examining a saw mark is mainly based on details relating to class characteristic features rather than individual characteristics. The authors seek to challenge this approach and demonstrate the feasibility of linking, using microscopic toolmarks comparison, cordless reciprocation saw, and the potential individual marks that may have resulted from the tip of its blade on the catalytic converter during the cutting action.”

3. 3

   2020–2022 catalytic converter theft ring (Wikipedia)

   WikipediaPublished Oct 7, 2026Checked Oct 15, 2026

   “From 2020 to 2022, an organized criminal group stole and then resold catalytic converters through the United States. The regional theft rings sent their stolen catalytic converters to DG Auto Parts in Freehold, New Jersey, who removed the precious metals from them and ground them into dust. The precious metals were then sold to Dowa Metals and Mining America for refining, after which they were sent to Japan; these sales are believed to have generated approximately $545 million in revenue for DG Auto Parts. The investigation that led to the discovery of the interstate theft ring was prompted by a wave of catalytic converter thefts in the Oklahoma area in late 2020 and early 2021, with similar rises across the United States. On May 2, 2021, police became aware of Tyler Curtis, the owner of Curtis Cores in Broken Arrow, Oklahoma, when he was involved in a traffic stop where (among other illicit things) 128 catalytic converters were found in the bed of his pickup truck; all had jagged edges, suggesting they had been stolen. By September, a team of investigators had linked Curtis Cores with DG Auto Parts, which was owned by Navin and Tinu Khanna.”

4. 4

   Stricter vehicle standards reduce total pollutants but increase the fraction of toxic organics.

   Environmental science and ecotechnology (Yang et al.)Published Jul 25, 2026Checked Oct 15, 2026

   “Notably, a modern hybrid vehicle emitted nearly twice the mass of OVOCs (25.4 mg km-1) compared to its conventional counterpart (13.3 mg km-1), driven by frequent engine start-stop cycles that reduce aftertreatment efficiency. This distinct operational profile allows us to identify specific compounds-namely, vinyl acetate and methyl t-butyl ether-as molecular markers for hybrid powertrains in our study. Consequently, despite superior fuel economy, this tested hybrid vehicle exhibited a 69% increase in non-carcinogenic health risks and nearly double the carcinogenic risk, overwhelmingly dominated by aromatics and toxic OVOCs such as acrolein. Furthermore, while absolute emissions declined, persistent aromatics continued to account for over 70% of the secondary organic aerosol formation potential. These findings highlight a critical tension between fuel efficiency advancements and toxicological impacts, suggesting that future emission regulations must transition from total mass limits to species-specific controls to fully safeguard public health.”

5. 5

   Exhaust gas after treatment using air preheating and selective catalytic reduction by urea to reduce NOx in diesel engine.

   Heliyon (Tushar et al.)Published Jan 31, 2025Checked Oct 15, 2026

   “The experimental setup involved a mechanical urea injection system, a platinum-rhodium catalyst, and an air-preheating mechanism utilizing exhaust gas heat. Tests were conducted at varying engine speeds and loads to evaluate the combined system's performance. Results indicate that the combined air preheating and urea-SCR system achieved a NOx reduction of up to 55 % under low engine load conditions, with a corresponding CO emission reduction of 19 % for preheated set-up. The system enhanced brake thermal efficiency (BTE) and reduced brake-specific fuel consumption (BSFC) compared to baseline configurations, with no significant backpressure observed. A significant noise level reduction (21-27 %) was also achieved, highlighting the dual benefits of emissions and noise control. The findings demonstrate that combining urea-SCR with air preheating is an effective strategy for reducing NOx emissions while maintaining or improving engine performance. This approach offers a promising pathway for enhancing diesel engine emission control systems. Further studies are recommended to explore the scalability of this method for larger engines and to assess long-term system stability.”