A registered trademark for a standardized, high-purity 32.5% urea solution in deionized water. It is specifically formulated for use in Selective Catalytic Reduction (SCR) systems to reduce nitrogen oxides (NOₓ) in diesel exhaust by converting them into harmless nitrogen (N₂) and water vapor (H₂O).
The ISO 22241 designation for AdBlue or Diesel Exhaust Fluid (DEF), standing for “Aqueous Urea Solution 32.5%.” It ensures consistent quality for use in SCR systems.
A condition where excess ammonia (NH₃), introduced through AdBlue decomposition, is not fully consumed in the NOₓ reduction reaction and exits the SCR system, potentially causing regulatory and odor issues.
The resistance to exhaust gas flow within the exhaust system, often caused by blockages or soot buildup in components like the Diesel Particulate Filter (DPF) or Diesel Oxidation Catalyst (DOC), which can affect engine performance and fuel economy.
Mercedes-Benz’s proprietary emissions control technology that integrates SCR and DPF systems to reduce NOₓ and particulate matter in diesel vehicles, meeting stringent emissions regulations.
A structured ceramic or metallic base inside catalytic components (such as SCR or DOC), onto which active catalytic materials are applied. It provides surface area for chemical reactions to take place.
A honeycomb-like ceramic structure commonly used as the substrate in emission control devices such as SCR catalysts and DPFs. It offers a large surface area for catalytic coatings while allowing exhaust gases to pass through.
A simulation technique used to model the flow and behavior of exhaust gases within emission control systems. CFD helps optimize system design for better efficiency and uniformity in chemical reactions.
Pollutants emitted during the initial engine warm-up period when exhaust temperatures are too low for emission control components like the SCR or DOC to operate at full efficiency.
A toxic gas produced by incomplete combustion, which is typically oxidized into less harmful carbon dioxide (CO₂) within the DOC.
A non-toxic greenhouse gas resulting from complete oxidation processes within the engine and aftertreatment system, including the conversion of CO in the DOC.
Operation of the Selective Catalytic Reduction system at lower exhaust temperatures, where NOₓ conversion efficiency may be reduced. Often a focus in emissions research and design optimization.
Any foreign substance such as dust, oil, calcium, or fuel residues that can degrade or damage emission control components by clogging filters or poisoning catalysts.
The temperature at which AdBlue begins to freeze and form crystals (~–11 °C), which can impair injection and dosing systems if not properly managed.
A method of reducing NOₓ emissions by recirculating a portion of exhaust gas back into the intake air, after cooling it, thereby lowering combustion temperatures.
The chemical process of converting harmful carbon monoxide (CO) into carbon dioxide (CO₂) within the Diesel Oxidation Catalyst (DOC), contributing to cleaner exhaust.
The American term for AdBlue, a standardized mixture of 32.5% high-purity urea and 67.5% demineralized water. DEF is injected into the exhaust stream of diesel vehicles equipped with Selective Catalytic Reduction (SCR) systems to convert harmful nitrogen oxides (NOₓ) into nitrogen (N₂) and water vapor (H₂O).
An emissions control device that captures and stores soot (particulate matter) from diesel engine exhaust. DPFs help meet particulate emission standards by preventing soot from being released into the atmosphere.
A catalyst in the exhaust system that facilitates the oxidation of carbon monoxide (CO) and unburned hydrocarbons (HC) into carbon dioxide (CO₂) and water vapor, also aiding in the generation of heat needed for DPF regeneration.
The process by which accumulated soot in the DPF is burned off at high temperatures, converting it into CO₂ and restoring the filter’s capacity. Regeneration can be passive (during normal driving) or active (through increased exhaust temperature).
A maintenance procedure that removes non-combustible residues like ash or sintered soot from the DPF. Unlike regeneration, cleaning is typically done off-vehicle using pneumatic or thermal methods to restore filter performance.
Government-imposed regulations that limit the amount of specific pollutants—such as NOₓ, CO, PM, and HC—that vehicles and engines can emit. Standards vary globally (e.g., Euro 6 in Europe, EPA Tier standards in the U.S.).
A thermodynamic property representing the total heat content of a system. In SCR applications, enthalpy influences how quickly exhaust gases reach the necessary temperatures for catalytic reactions and NOₓ conversion.
An experimental variation of a diesel particulate filter that uses ethanol-based catalytic solutions to assist in soot oxidation. It aims to lower the regeneration temperature and potentially reduce fuel penalties.
A technique that lowers NOₓ emissions by redirecting a portion of cooled exhaust gases back into the engine intake. This dilutes the incoming air, reducing combustion temperatures and NOₓ formation.
The condition of a vehicle or engine meeting the legally mandated emission limits for various pollutants. Compliance is verified through laboratory testing or onboard diagnostics and is required for certification and road use.
A group of atmospheric gases, such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), that trap heat and contribute to global warming. Diesel engines and their combustion processes can emit several GHGs, making their reduction a key focus of emissions control strategies.
A ceramic or metallic monolith with a honeycomb-like structure, used in SCR, DOC, and DPF components. Its design maximizes surface area for catalytic reactions while allowing exhaust gases to flow through with minimal restriction.
An engine in which fuel combustion occurs internally, producing mechanical power. Diesel ICEs are common in heavy-duty vehicles and require exhaust aftertreatment systems to meet emissions regulations.
An international standard that defines the composition, handling, and quality requirements for AdBlue (DEF). Compliance with ISO 22241 ensures compatibility with SCR systems and prevents catalyst damage.
A dosing device that delivers precise amounts of AdBlue/DEF into the exhaust stream upstream of the SCR catalyst, allowing for accurate control of ammonia availability for NOₓ reduction.
A variant of Selective Catalytic Reduction optimized to operate effectively at lower exhaust temperatures, typically encountered during cold starts or light-load driving conditions. These systems use specially formulated catalysts (e.g., Cu-zeolite) that remain active below traditional SCR temperature thresholds, allowing for earlier NOₓ conversion and improved overall emissions control in real-world driving.
A solid ceramic or metallic substrate with a honeycomb structure coated with catalytic material. It provides high surface area and low flow resistance for efficient chemical reactions in DOC, DPF, and SCR units.
A catalyst that incorporates metals such as vanadium oxide (V₂O₅), platinum, or palladium. In SCR systems, vanadium-based catalysts are used for NOₓ reduction, especially in stationary or older diesel applications. These catalysts are effective at high temperatures but may be phased out in favor of zeolite-based alternatives due to environmental and durability concerns.
A group of harmful gases primarily composed of nitric oxide (NO) and nitrogen dioxide (NO₂), formed during high-temperature combustion. NOₓ contributes to smog, acid rain, and respiratory issues and is the primary target of SCR systems in diesel emission control.
The company that designs and produces vehicles or engines and their certified emissions systems. OEMs specify the use of approved DEF and aftertreatment components to maintain regulatory compliance and protect warranties.
A continuous, automatic process in which the DPF burns off accumulated soot using the heat naturally present in the exhaust stream during regular driving conditions. It requires sufficient exhaust temperatures but does not require active intervention or fuel injection.
A type of SCR catalyst with flat, stacked surfaces rather than a honeycomb structure. Plate catalysts can offer improved flow dynamics and lower pressure drop in certain designs and are used in specific compact or low-flow applications.
Measures applied during the production of AdBlue/DEF to ensure it meets strict ISO 22241 standards. QC includes monitoring urea concentration, purity, and absence of harmful contaminants to protect SCR components.
A high-flow DEF dispensing nozzle designed to rapidly refill AdBlue tanks, especially in fleet or commercial vehicle settings. Quick-fill systems reduce downtime and support large-scale refueling operations.
A chemically active substance—in this case, AdBlue (DEF)—used in the SCR process to reduce NOₓ emissions. When heated, it decomposes into ammonia (NH₃), which reacts with NOₓ in the SCR catalyst.
A technique used to measure the refractive index of AdBlue to verify urea concentration. Inline or laboratory refractometers ensure the DEF meets the required 32.5% urea concentration for optimal SCR performance.
Diesel aftertreatment components like DPFs and DOCs that have been restored to original specifications through cleaning, inspection, and part replacement. REMAN parts are cost-effective and meet OEM performance standards when properly reconditioned.
The active catalytic material inside the SCR system that facilitates the conversion of nitrogen oxides (NOₓ) into nitrogen (N₂) and water (H₂O) using ammonia (NH₃) from DEF. Typically made of Cu-zeolite or Fe-zeolite for durability and high efficiency.
An emissions control technology that uses a catalyst and ammonia (from DEF) to convert nitrogen oxides (NOₓ) in diesel exhaust into harmless nitrogen (N₂) and water vapor (H₂O). It is widely used to meet strict NOₓ emissions regulations.
A DPF cleaning method in which a portion of exhaust is diverted to a separate burner or reactor to oxidize soot while the engine continues running normally. This allows for continuous operation without interrupting vehicle function.
The primary operational mode of the SCR system under normal, high-temperature conditions (typically above 200°C). In this mode, NOₓ reduction is most efficient and complete due to optimal catalyst activity and ammonia conversion.
The internal structure within catalysts like SCR, DOC, or DPF, usually made of ceramic (cordierite) or metal (stainless steel), that physically supports the catalytic coating. Its honeycomb design maximizes surface area while allowing exhaust gases to pass through with minimal restriction, promoting efficient chemical reactions.
A method of actively cleaning the DPF by increasing exhaust temperature—either through late fuel injection, an onboard burner, or electric heating—to ignite and burn off accumulated soot. This process restores filter capacity when passive regeneration is insufficient.
The resistance of catalytic materials and substrates to structural or chemical degradation at high temperatures. High thermal stability ensures long service life of SCR, DOC, and DPF components, especially during regeneration or full-load engine operation.
DEF available at commercial truck stops, often dispensed from high-volume pumps for convenient refilling of heavy-duty vehicles. Quality and availability may vary, so drivers are encouraged to verify that the DEF meets ISO 22241 standards.
Diesel fuel refined to contain no more than 15 parts per million (ppm) of sulfur. ULSD is required for modern emissions systems, as high sulfur content can poison catalysts and lead to excessive SO₂/SO₃ formation.
A nitrogen-based compound (CO(NH₂)₂) used as the active ingredient in AdBlue (DEF). When heated in the exhaust stream, urea decomposes into ammonia (NH₃), which then reacts with NOₓ in the SCR catalyst to produce nitrogen and water.
A standardized 32.5% by weight solution of high-purity urea in demineralized water. Also known as AdBlue (Europe), DEF (U.S.), or AUS 32 (ISO term), this solution is injected into the exhaust system for NOₓ control in SCR-equipped diesel engines.
The thermal breakdown of urea into isocyanic acid (HNCO) and ammonia (NH₃), typically occurring between 150°C and 300°C in the exhaust stream. The ammonia is used for NOₓ reduction in SCR, while HNCO hydrolyzes further into NH₃ and CO₂.
A traditional metal oxide catalyst used in some SCR systems, particularly in stationary or older mobile diesel applications. Composed mainly of vanadium pentoxide (V₂O₅), often with tungsten or titanium oxides, it facilitates NOₓ reduction at mid-to-high temperatures. However, vanadium catalysts are less thermally durable than zeolite types and may generate undesirable byproducts like N₂O or SO₃ at elevated temperatures.
One of the harmless end-products formed during the SCR reaction when ammonia (from urea/DEF) reacts with nitrogen oxides (NOₓ). Along with nitrogen gas (N₂), water vapor exits the tailpipe as a sign of successful NOₓ conversion and clean combustion.
A class of synthetic crystalline aluminosilicate catalysts (e.g., Cu- or Fe-zeolites) used in modern SCR systems. Zeolites provide excellent thermal stability and a large surface area for ammonia storage and NOₓ conversion, especially under varying load and temperature conditions. Their high durability makes them ideal for meeting strict emission standards in heavy-duty vehicles.
