Exhaust Emission Catalyst Technology NEW CHALLENGES and OPPORTUNITIES in EUROPE

Exhaust Emission Catalyst Technology NEW CHALLENGES AND OPPORTUNITIES IN EUROPE

By Dirk Bosteels and Robert A. Searles Association for Emissions Control by Catalyst, Av. de Tervueren 100, 6-1040 Brussels, Belgium; (www.aecc.be)

New technologies, incorporating the platinum group metals, are available to meet the exhaust emission regulations for cars, light-duty and heavy-duty vehicles and motorcycles being adopted by the European Unionfor implementation during the new century. These technologies include low light-offcatalysts, more themlly-durable catalysts, impmved substrate technology, hydrocarbon adsorbers, electrically heated catalysts, DeNOx catalysts and adsorbers, selective catalytic reduction and diesel particulate filters. This large range of technologies will allow exhaust emissions from all engines, both on- and non-road, to be lowered to unprecedented levels. This paper examines the state of emission control technologies currently available for all types of engine.

Catalyst-equipped cars were fist introduced in challenge is to abate the remaining pollutants emit- the U.S.A. in 1974 (1) but only appeared on ted while enabhg use of fuel-efficient engine European roads in 1985. Indeed, it was not until technologies. This is paramount for achieving 1993 that the European Union (ELI) set new car good air quality and the targets for greenhouse gas emission standards that effectively mandated the reductions given the large increase in the number installation of emission control catalysts on gaso- of vehicles on European roads, the projections for he-fuelled cars. Worldwide, now more than 275 further increases in vehicle numbers and the million of the world's 500 million cars and over 85 greater distances driven each year. per cent of all new cars produced are equipped with autocatalysts. Emissionsfmm On-Road Vehickr In the EU directives are being adopted to leg- The EU emission limits for passenger cars that islate the maximum exhaust emissions permitted came into effect from 1993 were lowered in 1996 from a wide range of vehicles and equipment pow- and again in 2000. For passenger cars (Tables I and ered by the internal combustion engine. Exhaust Il) and hght commercial vehicles the emission emission catalyst technology is increasingly being standards have been agreed for 2000 and 2005 (3). fitted on heavy-duty vehicles, buses, motorcycles Lght commercial vehicle limit values are adjusted and on non-road engines and vehicles. The 13 to compensate for the &her vehicle weights. candidate countries currently negotiating entry to Heavy-duty diesel (HDD) vehicles have new the EU (includingPoland, Hungary and the Czech test cycles and tougher emission standards Republic) d,as a result of adopang the limit val- finalised for 2000 and 2005. The limit values for ues of the EU, increase the application of the enhanced environmentally friendly vehicles technologies developed to control emissions in (EEVs) are set to serve as a basis for fiscal incen- the EU. tives by EU Member States. The 2005 (Euro W) emission standards set limit values for carbon European Union Exhaust Emission monoxide (CO) (1.5 g/kWh), hydrocarbons (HCs) and Fuel Legislation (0.46 g/kWh) and nitrogen oxides (NOx) (3.5 The final report of the European Auto Oil II g/kWh) and also PM limit values intended to force programme (2) concluded that some ait quality the use of particulate traps/diesel particulate filters problems, such as atmospheric levels of particulate (DPFs). The PM limits are 0.02 g/kWh on the matter (PM) and ozone, are not yet solved. The steady state cycle (ESC) and 0.03 g/kWh on the

Phtinwnr Met& Rev., 2002,46, (I), 27-36 27 Table I Gasoline Car Limit Values, g/km

Year co HC NOx HC t NOx

1993/94 2.72 - - 0.97 1996/97(*) 2.2 (2.7) - (0.341) - (0.252) 0.5 2000/01 2.3 0.20 0.15 - 2005/06 1 .o 0.10 0.08 -

' Limit values corrected to current EU test cycle with no 40 second idle at start of test transient cycle (ETC). The new limit values are a being ratified by the European Parliament and 30 per cent reduction in CO, HC and NOx and an Council. Tighter emission limits from 2003 for 80 per cent reduction in PM from Euro III limit new types of motorcycles are agreed and corre- values of October 2000. spond to a reduction of 60 per cent for HCs and In 2008 (Euro V), the NOx limit of 2.0 g/kWh CO for four-stroke motorcycles, and 70 per cent reflects the need for DeNOx or Selective Catalytic for HCs and 30 per cent for CO for two-stroke Reduction (SCR) catalysts. The limit is subject to a motorcycles. A second stage with new mandatory European Commission study, which will report by emission limits for 2006 is proposed, to be based the end of 2002, on technical progress of the on the new worldwide motorcycle emission test required emission control technologies (4). cycle 0,which is also being developed by The Working Party on Pollution and Energy the UNECE in Geneva. (GRPE), an expert group of the World Forum for Harmonization of Vehicle Regulations’ (WP.29) at Emissionsfrom Engines Used in Nan-RoadApplications the United Nations Economic Commission for The process of bringing emission limit values Europe (UNECE) in Geneva, is developing a and fuel quality in non-road applications in line worldwide heavy-duty certification procedure with those of on-road vehicles has begun. (WHDC) and is loow at new measurement pro- Technology adopted and proven in on-road appli- tocols in order to ensure that ultra heparticles are cations will in time be transferred to non-road controlled by hture emission legislation to mir- applications. The first European legislation to reg- imise the health effects of diesel patticle emissions. ulate emissions from non-road mobile equipment Another current action is a proposal by the is being implemented in two stages (5): European Commission to set tougher, catalyst- Stage I implemented in 1999 requiring emission limits for motorcycles. This is Stage I1 implemented from 2001 to 2004,

Table II Diesel Car Limit Values, g/km

Year co HC t NOx NOx PM 1993194 2.72 0.97 - 0.14 1996/97( *) 1.o 0.7/0.9§ - 0.0810.1 0 (1.06) (0.71/0.91§) (0.63/0.81§) - 2000101 0.64 0.56 0.50 0.05 2005106 0.50 0.30 0.25 0.025

Limit vulues corrected to currenr EU test cycle with no 40 second idle at starr oftest Values.for Direct Injection Diesels

Phtintm Metuh h.,2002,46, (1) 28 Table Ill EU Emission Limits for Non-Road Diesel Engines, g/kWh Net Power co I HC NOx I PM Stage I 130-560 kW 5.0 1.3 9.2 0.54 75-1 30 kW 5.0 1.3 9.2 0.70 37-75 kW 6.5 1.3 9.2 0.85

Stage II 130-560 kW 3.5 1 .o 6.0 0.2 75-1 30 kW 5.0 1 .o 6.0 0.3 37-75 kW 5.0 1.3 7.0 0.4 18-37 kW 5.5 1.5 8.0 0.8 dependmg on the engine power output. emission limits for small spark-ignition engines The equipment covered indudes mobile con- below 19 kW used in lawn mowers, chain saws, struction machinery, forklift trucks, road bush cutters, trimmers and snow removal equip- maintenance equipment, ground support equipment. The proposal, which is now being ment in airports, aedal lifts and mobile cranes. considered by the European Parliament and Agricultural and forestry tractors have the same Council, has been developed in cooperation with emission standards but with different implementa- the US. Environmental Protection Agency in a tion dates (6). Engines used in ships, railway move toward worldwide harmonisation. locomotives, aircraft, and generating sets, not yet The proposal indudes two stages of limit val- covered by the directive, are being considered by a ues: the first to be met 18 months after the Commission working group and will be included directive comes into force and the second one in the future. between 2004 and 2010 dependmg on the catego- Stages I and I1 are based on a steady-state 8- ry of the engine. The second stage will lower mode test procedure, and emission limit values are emissions from handheld engines by about 80 to shown in Table 111. 85 per cent. Values for the Stage 111 limits using a new tran- Gasoline and diesel engines installed in recre- sient test procedure (NRTC) are under discussion ational crafts and personal watercrafts are already in a European Commission working group. The subject to some emission and noise requirements intention is to develop global solutions and to and limits (8). The European Commission pro- develop the legislation in dose cooperation with posed amendments in October 2000 to the current the U.S.A. and Japan, using the global agreement directive, fuaher reducing the exhaust pollutants. under UNECE in Geneva as the basis for legislation. Fuels A European Commission Task Force has been The mandatory standards for fuel sulfur levels set up to improve the fuel quality for non-road for on-road fuels were set in 1998 (9). However applications. Reducing sulfur content in non-road after a full technical study the European fuels in line with those being introduced in the Commission adopted a proposal in May 2001 to road sector would allow engine makers to use the require the introduction of sulfur-free (< 10 ppm) advanced emission control technologies of cata- gasoline and diesel by each EU Member State lysts and traps to reduce gaseous and particulate from 1 January 2005. Under the proposal, still to emissions. A Commission proposal was issued be ratified, gasoline and diesel fuel with ‘a sulfur at the end of 2000 (7) and established the first content’ would be banned from the EU market

Phtimm~Mefa? Rm, 2002,46, (1) 29 All, except the first, of the above opportunities, will now be examined, looking at established and new technologies.

Established Exhaust Emission Catalyst Technology AutocatahJtts Oxidation catalysts convert CO and HCs to COZ and water and decrease the mass of diesel particulate emissions but have little effect on NOx. Three-way catalysts WCs) operate in a closed loop system which contains a lambda- (or oxygen) sensor to regulate the &/fuel ratio. CO and HC are simultaneously oxidised by the catalyst to COZ and water while NOx is reduced to nitrogen. These simultaneous oxidising and reducing reactions have the highest efficiency in the small air-to-fuel ratio window around the stoichiometiic value, when air and fuel are in chemical balance. The Fig. I Effect of different pgm loadings mid cornposition 011 light-off temperature active components of these catalysts are the platinum group metals (pgms) platinum (Pt), palladium from 201 1. These fuels will speed the introduction (Pd) and rhodium (Rh) in various combinations. of the latest fuel-efficient technologies in cars and other vehicles, significantly reducing the emissions Diesel Oxihtion Cata!ysfJ (DOCS) of carbon dioxide (COZ). An oxidation catalyst will remove the soluble organic fraction (SOF) of diesel particulate by up Exhaust Emissions from Internal to 90 per cent (10). Destruction of SOF is impor- Combustion Engines tant because this portion of the particulate There are a number of ways in which exhaust contains numerous chemicals of concern to health emissions can be lowered: experts. DOCs can thus reduce total particulate Reducing engine-out emissions by improving emissions by 25 to 50 per cent, depending on the the combustion process and fuel management, or constituents that make up the total particulate. by changes to the type of fuel or its composition They also reduce diesel smoke, eliminate the pun- Decreasing the time required for the catalytic gent diesel exhaust odour and make significant converter to reach its full efficiency reductions in CO and HCs. However the number Increasing the conversion efficiency of catalysts of particles is unchanged and issues associated with Storing pollutants during the cold start for the effects of ultra-fine particulates are unresolved. release when the catalyst is working DOC technology has been successfully used on all Using catalysts and adsorbers to destroy NOx diesel cars sold in Europe since 1996; not many under lean operation heavy-duty vehicles are equipped with a catalyst Using particulate filters with efficient regenera- (11). tion technology DOCs are also used in conjunction with NOx Increasing the operating life of autocatalysts adsorbers, DeNOx catalysts, DPFs or selective and supporting systems catalytic reduction (SCR) to increase NO2 levels Retrofitting catalytic converters, particulate or to ‘clean-up’ any by-pass of injected reductant traps and associated engine and fuel management used for NOx reduction (HCs or ammonia). The systems if they are not original equipment. preferred pgm for DOCs is Pt.

PLatinum Metah Kev., 2002, 46, (1) 30 Fig. 2 Imn~~r~i~~ententsto the thermal stahiliry cmd oxygen storage capmi8 vj'ci ccitolyst support of mixed cerium and :irconiurn o.i-ides ufirr air Ngeiiig at 900%,for 6 hours

Fast Lgbt-off Catahsts three-way operation and indicate the 'health' of the The catalytic converter has to work soon after catalytic converter for onboard diagnostic (OBD) the engine is switched on, and to achieve this the systems. Figure 2 shows the progress made with exhaust temperature at which it starts to function mixed cerium and zirconium oxides (14). needs reducing so that untreated exhaust emitted at the start of the legislated emissions test and on Substrate Technology short journeys in the real world is minimised. Great progress has been made in the technolo- Reductions in the thermal capacity of substrates gy of the substrates on which the active catalyst is and improvements to the type and composition of supported. In 1974 ceramic substrates based on the active pgm catalyst have reduced light-off cordierite (2Mg0.W203.5SiO$ had a density of times from as long as one to two minutes down to 200 cells per square inch (cpsi) of cross-section (31 less than 20 seconds (12). In Figure 1, the effect of cells cm-7 and a wall thickness of 0.012 inch or 12 different catalyst compositions as they affect the mil (0.305 mm). By the end of the 1970s the cell light-off temperature are shown. density had increased through 300 to 400 cpsi and The introduction of a new generation of Pt/Rh wall thickness had been reduced by 50 per cent to technologies for current and future emission star- 6 mil. Now 400,600,900 and 1200 cpsi substrates dards is a technically and commercially amactive are available and wall thickness can be reduced to alternative to Pd-based technologies for high 2 mil - almost 0.05 mm (15-19). Further increas- demanding applications in close-coupled and es in cell density and reductions in wall thickness underfloor positions using different cold start are in development. strategies (13). Substrates derived from ultra thin foils of cor- rosion-resistant steels came onto the market in the More Thermally Durable Catalysts late 1970s. In the beginning the foils were made Increased stability of the catalytic converter at from material 0.05 mm thick, allowing high cell high temperature allows it to be mounted closer to densities to be achieved and complex internal the engine and increases its life, particularly during structures could be developed. Today, wall thick- demanding driving. Catalysts with stabilised pgm ness is down to 0.025 mm and cell densities of 800, crystallites and washcoat materials which maintain 1000 and 1200 cpsi substrates are available (20,21). high surface area at temperatures around 1000°C Progress in ceramic and metal substrate tech- are necessary. The surface area of the washcoat is nology has given major benefits. A larger catalyst stabilised by improved oxygen storage compo- surface area can be incorporated into a given con- nents that also maximise the air-fuel 'window' for verter volume and this allows better conversion

Pkatinnm MetaLr Rm, 2002, 46, (1) 31 efficiency and durability. The thin walls reduce thermal capacity and avoid the penalty of increased 10 pressure losses. Alternatively the same perfor- 9 mance can be incorporated into a smaller 78 E converter volume, which, as cars become more 17m 6 compact, makes the catalyst easier to fit close to vi the engine. 55 $4 I3 w New Technologies for Exhaust 2 Emissions Control 1 Stoichiometric Combustion 0 co HC NOx Hydrocarbon Adsorbers Special materials, such as zeolites, are incorpo- I Fig. 3 Influence of improved three-wuy catalyst and rated upstream of or into the catalyst in HC hydrocurbon udsorber systems on CO, HC and NOx adsorber systems. Hydrocarbon emissions are col- emissions (European cycle) lected when exhaust temperatures are too low for effective catalyst operation. The HCs are then des- depend on exhaust temperature and the availabili- orbed at higher temperatures when the catalyst has ty of reducing agents. There are currently four reached its operating temperature and is ready to NOx-reducing systems under evaluation and receive and destroy the HCs. This technology has development by industry: the potential to reduce HCs to less than half the [i] Passive DeNOx catalysts using reducing agents levels emitted from a TWC converter (22), see available in the exhaust stream Figure 3. [i] Active DeNOx catalysts using added HCs as reducing agents El'ectvicalh Heated Catahst .$terns [iii] NOx traps or adsorbers used in conjunction A small metallic substrate ahead of the main with a TWC catalyst, and onto which the catalyst is deposited, [iv] Selective catalytic reduction using a selective allows an electric current to pass so it will heat up reductant, such as ammonia from urea. quickly. This brings the catalyst to its full operating Each of these systems offers different possibilities temperature in a few seconds (23). in the amount of NOx control achievable and in the complexity of the system. Fuel parameters, such Lean Combustion as sulfur content, can affect catalyst performance. The development of lean bum direct injection gasoline engines and increased use of diesel DeNOx (or LanNOx) Cata& engines makes lean combustion a challenge for Advanced sa~cturalproperties in the catalytic automotive catalysis. Lean combustion is essential coating of DeNOx catalysts are used to create a to limit CO:! emissions and reduce fuel consump- rich 'microclimate' where HCs from the exhaust tion. New diesel technologies with electronic can reduce the NOx to nitrogen, while the overall management and direct injection can achieve fur- exhaust remains lean. Further developments focus ther improvements in fuel consumption. on increasing the operating temperature range and Conventional TWC technology (used on gasoline the conversion efficiency. engines) needs a richer environment with lower &/fuel ratios to reduce NOx, so a radical new NOxAdsorbers (or Lean NOx Traps) approach is required. NOx traps or adsorbers are a more promising The use of DeNOx catalysts and NOx traps development as results show that NOx adsorber brings the prospect of substantially reduced emis- systems are less constrained by operational tem- sions of oxides of nitrogen. NOx conversion rates peratures than DeNOx catalysts. NOx traps

Phtinum Metah REP., 2002,46, (1) 32 adsorb and store NOx under lean conditions. A typical approach is to speed up the conversion of nimc oxide (NO) to nitrogen dioxide (NO,) using a pgm-containing oxidation catalyst or TWC mounted close to the engine so that NO2 can be rapidly stored as nitrate. The function of the NOx storage element can be fulfilled by materials that are able to form sufficiently stable nitrates within the temperature range determined by the lean operation regime of a direct injection gasoline engine. Thus especially alkaline, alkaline earths and, to a certain extent, also rare earth compounds can be used. When this storage media nears capacity it must be regenerated. This is accomplished in a NOx regeneration step. Unfortunately, alkaline and alkaline earth compounds have a strong affinity for sulfation. As a conse- quence alkaline and alkaline earth compounds are almost irreversibly poisoned by the sulfur contained in the fuel during the NOx storTage operation mode,mode, leading to a Fig. 4 The working principle of rhe NOx adsorber: Upper diagram: under lean (low fuel) conditions, NO reucrs with 02 on decrease in NOx adsorption efficiency dur- the Pr catdvst, to produce NOr which is them adsorbed. Lower ing operation. The stored NOx is released diagrurn: under rich (highfuel) conditions by creating a rich atmosphere with injection of a small amount of fuel. The rich running portion timing, results in a considerable increase in tion is of short duration and can be accomplished fuel consumption, dependent upon the sulfur con- in a number of ways, but usually includes some tent. Reducing fuel sulfur levels is the best way of combination of intake air throthg, exhaust gas using the full fuel economy and CO, reduction recirculation, late ignition tirmng and post com- potential of modern direct injection gasoline bustion fuel injection. The released NOx is quickly engines. reduced to N2by reaction with CO (the same reac- Developments and optimisation of NOx tion that occurs in a TWC for spark-ignited adsorber systems are currently underway for diesel engines) on a Rh catalyst site or on another pgm and gasoline engines. These technologies have catalyst that is also incorporated into this unique demonstrated NOx conversion efficiencies rang- single catalyst layer (Figure 4). ing from 50 to in excess of 90 per cent, depending Thermal dissociation of the alkaline and aka- on the operaang temperatures and system respon- line earth sulfates, under oxygen-rich conditions, siveness, as well as fuel sulfur content (27,28). The would require temperatures above 1000°C. Such system is in production with direct injection gaso- temperatures cannot be achieved under realistic line engines. driving conditions. However, it has been demonstrated that it is possible to decompose the Sehctive Catabiic Reduction (Sa) corresponding alkaline earth sulfates under reduc- SCR technology has been used successfully for ing exhaust and elevated temperature conditions more than two decades to reduce NOx emissions to restore the NOx storage capacity (24-26). The from power stations fired by coal, oil and gas, necessary catalyst heating, for example by late igni- from marine vessels and stationary diesel engines.

Phtinnm Mefdr Rev., 2002,46, (1) 33 SCR technology for HDD vehicles has been developed to the commercialisation stage and was available as an option in the series production of several European truck-manufacturing companies in 2001. SCR technology permits the NOx reduction reaction to take place in an oxidising atmosphere. It is called ‘selective’ because the catalytic reduction of NOx with ammonia as a reductant occurs prefer- entially to the oxidation of ammonia with oxygen. Several types of catalyst are used and the temperature of the exhaust envi- Fig. 5 Wall flow diesel partirulute filteK illustrating how the Ionment determines the choice. For exhausi gas can puss through thefilter walls. Particulate matter mobile source applications the preferred becomes trapped in the walls reductant source is aqueous urea, which rapidly hydrolyses to produce ammonia in the is the fine particulate carried deep into the lungs exhaust stream. which could be the most dangerous size of PM to SCR for heavy-duty vehicles reduces NOx health. emissions by around 80 per cent, HC emissions by Since the wall flow filter would readily become around 90 per cent and PM emissions by around plugged with particulate material in a short time, it 40 per cent in the EU test cycles, using current is necessary to ‘regenerate’ the filtration properties diesel fuel (< 350 ppm sulfur) (29, 30). Fleet tests of the filter by regularly burning off the collected with SCR technology show excellent NOx reduc- PM. The most successful methods to initiate and tion performance for more than 500,000 km of sustain regeneration include: ttuck operation. This experience is based on over [a] Incorporating a pgm-based oxidation catalyst 6,000,000 km of accumulated commercial fleet upstream of the DPF. This operates as a conven- operation (31-33). tional oxidation catalyst but also increases the ratio The combination of SCR with a pre-oxidation of NO2 to NO in the exhaust. Trapped particulates catalyst, a hydrolysis catalyst and an oxidation cat- bum off at normal exhaust temperatures using the alyst enables higher NOx reduction under low load powerful oxidative properties of NOz (37). and low temperature conditions (34-36). [b] Using very small quantities of fuel-borne catalyst, such as cerium oxide. The catalyst, when Diesel Particuhte Filtets (DPFs) collected on the DPF as an intimate mixture with A diesel particulate filter is positioned in the the particulate, allows the particulate to bum at exhaust and is designed to collect solid and liquid normal exhaust temperatures to form COz and PM emissions while allowing the exhaust gases to water, while the solid residues of the catalyst are pass through the system. Figure 5 shows one type retained on the DPF (37). of filter material. [c] Incorporating a catalytic coating, typically a However, a number of filter materials are used, combination of pgm and base metals, on the DPF incluw ceramic monoliths, woven silica fibre to lower the temperature at which PM bums. coils, ceramic foam, wire mesh and sintered or [d] Electrical heating of the DPF either on or off shaped metals. Collection efficiencies of these var- the vehicle, which would allow simple regenera- ious filters range from 30 to over 90 per cent, but tion, but would impose a fuel penalty. most DPFs achieve over 99 per cent when [el A combination of the above mentioned systems expressed as numbers of ultra fine particles. This is and intelhgent engine-management allows efficient very important since health experts believe that it regeneration under all operating conditions. The

Pbtinwnr Metah Rev., 2002, 46, (1) 34 first diesel passenger cat equipped with a com- particles into the atmosphere. Urea-based SCR bined filter system was commercialised in 2000 systems and DPFs with an appropriate regenera- and evaluations indicate a good and durable per- tion strategy are anticipated to be used on the next formance of the system. The system has now been generation HDD engines and to show significant extended to other models (39,40). reductions of both NOx and PM (4547). Continuously regeneraw DPFs are very successful in retrofit applications of older HDD Conclusions vehicles and buses in various regions over the There is thus a wide range of gaseous and par- world. Real world durability of these systems is ticulate emission control options based on the use proven every day in major cities in Europe and the of catalytic, adsorption and trapping technologies, U.S.A. (4143). With any catalyst/DPF combina- with the pgms playing an essential role. don which includes pgms the use of diesel fuel Retrofitting of catalyst systems and particulate having a sulfur content lower than 10 ppm is nec- traps is increasing in response both to fiscal incen- essary to keep the formation of sulfate particulates tive schemes introduced by governments and to within future legislated limits (44). meet the requirements of environmental zones, particularly in cities. Europe has a strong automo- Combined Emission ConhL Systems (DPF + SCR) tive emissions control industry well placed to help A combined emission control system is an meet the challenge of future emission regulations attractive proposition; this is because of the strin- by worlung with its partners in the automotive gent emission limit values for NOx and PM set for industry. Advanced catalyst and trap systems, HDD engines in 2005 and 2008, the demands by together with optimised engine management and the transport sector for minimum fuel consump- emission controls can aid the achievement of the don of the engine and the political, public and future low emission standards deemed necessary health concerns over the emission of ultra he to meet air quality goals.

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Emmerling, A. Doring, U. Graf, M. The Authors Harris, J. van den Tillaart and B. Hupfeld, Dirk Bosteels is Technical Manager of AECC and his professional ‘Reduction of NOx from HD diesel engines with background is in emissions testing and vehicle safety urea SCR compact systems’, 19th Vienna Motor homologation. Symp., 7-8 May, 1998, VDI Fortschrittsberichte Rob Searles is Executive Director of AECC and has been involved Rehi 12, Nr. 348,366-386 with catalytic emissions control for more than 30 years

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