Views: 0 Author: Cécile Favre, John May & Dirk Bosteels Publish Time: 2025-06-26 Origin: International Paper
Abstract
The paper reviews the technologies available to meet the exhaust emissions regulations for passenger cars, light-duty and heavy-duty vehicles, non-road mobile machinery and motorcycles adopted by the European Union for implementation by 2016. This includes fast light-off catalysts, more thermally durable catalysts, improved substrate technology, diesel particulate filters, selective catalytic reduction, NOx adsorbers and lean DeNOx catalysts.
This paper presents results from a recent heavy-duty diesel test program showing that Euro VI emissions limits can be met with some safety margin with a Diesel Oxidation Catalyst (DOC), a Catalyzed Diesel Particulate Filter (CDPF), a Selective Catalytic Reduction (SCR) system and an Ammonia Slip Catalyst (ASC) applied to a ‘world’ engine with low engine-out NOx emissions.
AECC is an international association of European companies engaged in the development, production and testing of catalyst and filter based technologies for engine exhaust emissions control. This includes the development, testing and manufacture of autocatalysts, ceramic and metallic substrates and specialty materials incorporated into the catalytic converter and filter plus catalyst based technologies to control diesel engine emissions (especially particulates and nitrogen oxides).
Catalyst-equipped cars were first introduced in the USA in 1974 but only appeared on European roads in 1985. It was 1993 before the European Union set new car emission standards that effectively mandated the installation of emission control catalysts on gasoline fuelled cars.
Nowadays, AECC members’ technologies are incorporated in the exhaust emission control systems on all new cars and an increasing number of commercial vehicles, buses, non-road mobile machineries and motorcycles in Europe. They are used as part of an integrated approach to emissions control which includes the combustion system, fuel quality and electronic control systems.
The European Union (EU) emissions limits for passenger cars and heavy-duty vehicles have continuously been lowered since 1993 with the Euro 1 to 6 consecutive stages (1) and the Euro I to Euro VI stages (2) respectively. Not only have HC, CO, NOx and PM limits been dramatically reduced but also cold starts, particle number and CO2 measurement have been added into emissions driving cycles. For engines intended for heavy-duty vehicles and non-road mobile machinery (NRMM), transient operation has also been added. Motorcycles and non-road mobile machinery have lagged behind but their environmental performance keeps improving nevertheless with Euro 1 to 3 stages for motorcycles (3) and Stages I to IV for NRMM (4).
Fuel and lubricant quality affects the performance of emissions control systems either by preventing the use of a technology unless the fuel quality is improved (the improved fuel is ‘enabling’ the use of that technology) or by ‘enhancing’ the performance of emissions control systems. In this case both the existing fleet and new vehicle registrations benefit. The motor industry has published information on the effects of fuel quality, with recommendations, in the ‘Worldwide Fuel Charter’ (5).
Examples of enabling fuels are unleaded petrol that allows three-way catalysts to be used and ultra-low sulfur fuels required so that NOx adsorbers can be used and which ease the use of catalyst-based Diesel Particulate Filters (DPF). Lead has long been recognized as a catalyst poison as well as having impacts on human health, and is no longer permitted in European fuels. The ban on the sale of leaded petrol in EU and elsewhere, provides an example to influence other regions
Examples of enhancing fuels are the further reductions in the levels of lead, phosphorus and alkali metals that improve the performance and life of three-way catalysts and the introduction of ultra-low sulfur gasoline and diesel fuels. Reducing sulfur levels all the way down to near-zero delivers improved performance of catalysts.
The negative impact on catalyst performance of sulfur in gasoline and diesel fuels has been reported by AECC as part of the stakeholders input to the European Commission’s review on fuel quality. A technical summary on EU fuel quality is available on the AECC website (6).
The sulfate storage and release process was minimized by the introduction of the <10 ppm sulfur diesel fuel being progressively introduce across the EU since 2005. This fuel quality is necessary for the full potential of emissions control systems to be realized. Ultra-low sulfur fuels, already widely available, will be mandatory in the EU for passenger cars and heavy-duty applications by 2011. Non-road mobile machinery will also require the use of ultra low sulfur diesel (10 ppm S) as of 1 January 2011.
Also, there are concerns over the use of some metallic additives, with suggestions that their use in gasoline may, under some driving conditions, lead to deposits on exhaust system components such as the oxygen sensor and catalyst. Metallic or other ash-forming materials in diesel fuel will also add to the amount of ash captured by particulate filters and may require the system to be designed so as to allow for the additional ash. Detergent additives, on the other hand offer positive benefits. Their use helps keep the fuel injection system and combustion system clean, so helping to prolong optimum operating conditions for the emissions control technology.
Exhaust emissions can be lowered by reducing engine-out emissions through improvements to the combustion process and fuel management, or by changes to the type of fuel or its composition.
Emissions control systems – autocatalysts, adsorbers and particulate filters – in combination with good quality fuel (low sulfur content) and enhanced engine management reduce emissions to very low levels. As well as their application in new vehicles and machinery, many emissions control systems can also be applied in retrofit applications to good effect.
