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Emissions reduction of high and low polluting new technology vehicles equipped with a CeO2 catalytic system
The Science of the Total Environment 235 Ž1999. 71]76
Emissions reduction of high and low polluting new technology vehicles equipped with a CeO 2 catalytic system K. NikolaouU Organization for the Master Plan and En¨ ironmental Protection of Thessaloniki, 4 Angelaki St., 54636 Thessaloniki, Greece
Abstract The efficiency of a catalytic system that provides the vehicle combustion chamber with an adequate amount of cerium oxide ŽCeO 2 ., without affecting the operational parameters of the engine, has been studied for pollutant emissions reduction. New technology gasoline engine passenger cars, equipped with this catalytic system, have been driven on their normal route by the same drivers, in order to obtain the same traffic conditions and the same driving mode, as far as possible. These vehicles were tested for CO and HC emissions before and after the installation of the catalytic system. The new technology passenger cars examined have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the CeO 2 catalytic system.. The two categories are: Ža. high polluting cars with CO and HC emissions above the implemented standards; and Žb. low polluting cars with emissions below the standards. Both car categories equipped with the CeO 2 system, present important reduction of the pollutant emissions. The results are interpreted statistically and they are correlated with other studies. Q 1999 Elsevier Science B.V. All rights reserved. Keywords: Cerium oxide; Catalytic system; Vehicle emissions; Carbon monoxide; Hydrocarbons
1. Introduction The primary pollutants like carbon monoxide ŽCO. and hydrocarbons ŽHC. are strongly related to the vehicle emissions and they determine con-
U
Tel.: q30-31-224950; fax: q30-31-224720. E-mail address: [email protected] ŽK. Nikolaou.
siderably the photochemical air pollution in an urban area. Cerium is widely known as one of the catalytically active components used to remove pollutants from vehicle Žauto-exhaust . emissions. The active form of Ce is CeO 2 Žcerium dioxide. or ceria or ceric oxide which is the most stable oxide of cerium. When cerium salts are calcined in air or oxygen-containing environments, tetravalent
0048-9697r99r$ - see front matter Q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 9 9 . 0 0 1 9 1 - 6
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K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Ce ŽIV. oxide is formed. The sesquioxide, Ce 2 O 3 with trivalent Ce ŽIII., can be prepared in strongly reducing conditions but is unstable in the air readily converting to the dioxide. Cerium has one of the highest free energies of formation for an oxide ŽKilbourn 1992, 1993, 1994.. Current three-way catalytic converters contain finely divided ceria dispersed within the washcoat. CeO 2 is known to improve the dynamic performance for the removal of CO Žcarbon monoxide., NO x Žnitrogen oxides. and HC Žhydrocarbons. under conditions with rich-lean airrfuel oscillation in the automotive exhaust. Structural and energetic factors play an important role in the development of a new generation of automobile exhaust catalysts containing CeO 2 doped with ZrO 2 andror other rare earth oxides such as PrO x , Y2 O 3 and La 2 O 3 . These new catalysts possess high oxygen storage capacity, improved thermal stability and enhanced catalytic properties ŽTrovarelli et al., 1997.. Another application is the use of cerium as a fuel additive. Studies on diesel engine buses operated on a cerium-based fuel additive concluded that CeO 2 and cordierite filter interaction is limited ŽPattas et al., 1992.. A catalytic system containing a group of rare earths, with the most prevalent being CeO 2 , providing the vehicle combustion chamber with ceria nanoparticles in order to optimise the combustion and reduce the vehicle pollutant emissions, has been tested and operated in many countries around the world like: USA, Canada, UK, Japan, Belgium, Mexico and Greece. The results of the last decade of these vehicle emission reduction
tests, using the CeO 2 system, showed an important reduction of CO, HC, NO x and particulate emissions ŽNikolaou, 1996.. The main idea of this catalytic system is to provide the combustion chamber with an adequate amount of cerium oxide ŽCeO 2 ., without affecting the operational parameters of the engine Žsee Fig. 1.. The system’s cylindrical metal canister contains a group of rare earth compounds, with the most prevalent being cerium oxide. A venturi-created vacuum, pulls filtered ambient air through the device. The cerium oxide enriched air travels from the device to the engine’s air induction system via a rubber connector hose. In the combustion chamber, micro amounts of cerium oxide catalyse the combustion reaction, lowering average combustion temperature and improving engine performance ŽNikolaou, 1996, 1997; Nikolaou et al., 1998a.. During the first 3000]5000 km Ždepending on the engine state., this catalytic system removes carbon-build-up from valves, valve settings and other internal engine surfaces. After this clean-up phase, the system yields its full potential and reduces the vehicle pollutant emissions and simultaneously the vehicle fuel consumption. The amount of CeO 2 will perform for approximately 65000]75000 km, or the equivalent, depending on the amount of idling. Once spent, the metal canister can be replaced within minutes. Because of the fact that there are no moving parts in the device, no maintenance is required. The system can be retrofitted on gasoline, diesel or alternative fuel-operated vehicles.
Fig. 1. The CeO 2 catalytic system procedure.
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
The efficiency of this system in diesel and gasoline engine vehicles has been evaluated in previous studies, using various criteria. A study on diesel engine vehicles Žurban public transport buses and taxis., equipped with the CeO 2 catalytic system showed that the older and higher polluting diesel engine cars present the lower percent reduction during the first kilometres of operation with the catalytic system Ž29% reduction of particulate emissions after 8000 km. and 43% after the clean-up phase. The newer diesel engine cars present the maximum reduction Ž93%. of the particulate emissions during the first 8000 km. It has been also observed as a significant fuel consumption reduction, by a minimum of 10% ŽNikolaou, 1997.. Another study on gasoline engine passenger cars equipped with the CeO 2 catalytic system was realised using as criterion their mileage. The old technology cars Žwithout three-way catalyst ., after 1 km of system use, present an increase of CO and a small reduction Ž13]14%. of HC emissions. They present reduction of CO Ž10]18%. and HC Ž26]31%. emissions, after 3000 km of system use. The older new technology cars equipped with three-way catalyst, after 1 km of system use, present reduction of CO Ž54]77%. and HC Ž49]55%. emissions. They present a better reduction of CO Ž79]85%. and HC Ž59]82%. emissions, after 3000 km of system use. The newer technology cars equipped with three-way catalyst, after 1 km of system use, present reduction of CO Ž91]94%. and HC Ž61]65%. emissions. They present a better reduction of CO Ž96]97%. and HC Ž72]82%. emissions, after 3000 km of system use ŽNikolaou et al., 1998a.. Similar results were obtained in a parallel study, where it has been determined the influence of this catalytic system on the emissions reduction in correlation to the accumulation of km, for various vehicles Žcommon car, car with uninstalled threeway catalyst, car with turbo engine. and on fuel consumption reduction Ž10]20%. with measurements on an electronic dynamometer ŽNikolaou et al., 1998b.. In this study, 34 new technology gasoline engine passenger cars, equipped with the CeO 2 catalytic system were tested for CO and HC emis-
73
sions before and after the installation of the system. The examined passenger cars have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the catalytic system.: cars with emissions above and below the implemented standards.
2. Materials and methods During 1996]1997 in Thessaloniki, 34 new technology passenger cars equipped with threeway catalytic converters ŽTWC. and using unleaded gasoline were driven on their normal route by the same drivers, in order to obtain the same traffic conditions and the same driving mode, as far as possible. For each of the 34 passenger cars, the following parameters have been examined: model year, engine size Žl., number of kilometres before the installation of the system Žmileage., number of kilometres after the installation of the system, CO Ž%. and HC Žppm. emissions at 900 rev.rmin and 2500 rev.rmin: before,1 kilometre after and 3000 km after the installation of the CeO 2 catalytic system. The CO and HC emissions were measured by the non-dispersive infrared radiation ŽNDIR. absorption method, in order to be in accordance with the reference method of the relative Ministerial In Common Act: FEK 829rBr94 of the Hellenic State and the directives of the European Union. The examined new technology passenger cars have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the CeO 2 catalytic system. with reference to the implemented standards for CO and HC vehicle emissions. The implemented standards are: Ža. CO, 0.5% at 900 rev.rmin; Žb. CO, - 0.3% at 2500 rev.rmin; Žc. HC, - 120 ppm at 900 rev.rmin; and Žd. HC, - 100 ppm at 2500 rev.rmin. Passenger cars having emissions above the three of the four Žabove mentioned. standards, are characterised as high polluting cars. Passenger cars having emissions below the two Žat least. of
74
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Fig. 2. The CO average emissions at 900 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
the four standards, are characterised as low polluting cars. Both categories have cars with: model year from 1991 to 1996, various mileage from 20 000 to 150 000 km Žaverage 70 000 km. before the installation of CeO 2 catalytic system and various engine size from 1.3 to 2.0 l Žaverage 1.5 l.. Consequently, the only difference between the two car categories is the level of their initial emissions. 3. Results Fig. 2 represents the CO average emissions Žat 900 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 89% reduction after 1 km and 3000 km. The low polluting cars present 79% reduction after 1 km and 84% reduction after 3000 km, with reference to the initial emissions. Fig. 3 represents the CO average emissions Žat 2500 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 58% reduction after 1 km and 95% reduction after 3000 km. The low polluting cars present 74% reduction after 1 km and 94% reduction after 3000 km, with reference to the initial emissions. Fig. 4 represents the HC average emissions Žat 900 rev.rmin. for each category of the examined new technology passenger cars before the instal-
Fig. 3. The CO average emissions at 2500 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
lation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 55% reduction after 1 km and 67% reduction after 3000 km. The low polluting cars present 54% reduction after 1 km and 70% reduction after 3000 km, with reference to the initial emissions. Fig. 5 represents the HC average emissions Žat 2500 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 59% reduction after 1 km and 85% reduction after 3000 km. The low polluting cars present 59% reduction after 1 km and 80% reduction after 3000 km, with reference to the initial emissions.
4. Discussion and conclusions The examined new technology Žwith three-way catalytic converters-TWC. passenger cars present an average reduction of CO and HC emissions of the order of 67]95% after the installation of the CeO 2 catalytic system Žafter accumulation of 3000 km of system use.. This percentage does not include the emissions decrease resulting from the fuel consumption reduction Ž10]20%. after the installation of the system ŽNikolaou et al., 1998a,b.. The high polluting new technology cars Žpassenger cars having emissions above the three of the four implemented emissions standards. present 58]89% average reduction of CO and
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Fig. 4. The HC average emissions at 900 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
55]59% of HC emissions during 1 km after the installation of the CeO 2 catalytic system. These cars present 89]95% average reduction of CO and 67]85% of HC emissions, after 3000 km of system use. Before installation of the CeO 2 system, 100% of the high polluting cars present emissions of CO at 2500 rev.rmin and HC at 900 rev.rmin above the standards and 77% of CO at 900 rev.rmin and HC at 2500 rev.rmin. After the installation, 100% of these cars present emissions below the standards except a small percentage Ž8%. of the cars, which continue to have emissions of HC at 900 rev.rmin above the standards. The low polluting new technology cars Žpassenger cars having emissions below the two of the four implemented emissions standards. present 74]79% average reduction of CO and 54]59% of HC emissions, 1 km after the installation of the CeO 2 catalytic system. These cars, after 3000 km
Fig. 5. The HC average emissions at 2500 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
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of system use, present 84]94% average reduction of CO and 70]80% of HC emissions. Before the installation of the CeO 2 system, 93% of the low polluting cars present emissions of CO at 900 rev.rmin below the standards, 59% of CO at 2500 rev.rmin, 73% of HC at 900 rev.rmin and 91% of HC at 2500 rev.rmin. After the installation, 100% of these cars present emissions below the standards except a small percentage Ž9%. of the cars, which continue to have emissions of CO at 2500 rev.rmin above the standards. These results show that both categories Žhigh and low polluting. of the new technology passenger cars present the lower percent reduction of CO and HC emissions during the first kilometre and a better percent reduction during the next 3000 km of operation with the CeO 2 catalytic system. This is due to the fact that during the first kilometre, this catalytic system removes carbon build-up from internal engine surfaces. After this clean-up phase, the system yields its full potential and all the cars Ževen the high polluting cars. present emissions which are considerably below the implemented standards. For the small percentage Ž8]9%. of the cars, which present emissions above one standard Žonly. for each category, it can be assumed that these cars have a longer clean-up phase Žbecause of their engine status: high mileage and maintenance-regulation problems. in order to present the best possible pollutant emissions reduction. Consequently, additional reductions can occur as these cars accumulate additional kilometres, equipped with the catalytic system, as it has been demonstrated in other works ŽNikolaou, 1997; Nikolaou et al., 1998a.. These results and conclusions are in accordance with those observed in other studies ŽNikolaou, 1996, 1997; Nikolaou et al., 1998a,b.. The observed reduction of CO and HC emissions of the new technology cars is of great importance for the reduction of the total vehicle emissions, because it is well known that only a small percentage of vehicles Ž10]20%. contribute to more than half of CO and HC total vehicle emissions ŽNikolaou and Stedman, 1993; Nikolaou et al., 1994.. These vehicles Žmainly with maintenance
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K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
and regulation problems. are not only old technology or old model vehicles. The newer polluting vehicles are more numerous and dominate the total fleet emissions and consequently, it is important to place more focus on their emissions reduction. References Kilbourn B. Cerium. A guide to its role in chemical technology. New York, USA: Molycorp, 1992:42. Kilbourn B. A lanthanide lanthology. Part I, A-L. New York, USA: Molycorp, 1993:61. Kilbourn B. A lanthanide lanthology. Part II, M-Z. New York, USA: Molycorp, 1994:55. Nikolaou K, Stedman D. Remote sensing of vehicle emissions-case study: Thessaloniki, Greece. Com Con 1993;4:80]86. Nikolaou K, Stedman D, Papaioannou S, Zoumakis N, Kelesis A. Determination of parameters influencing the vehicle emissions in Greece, using a remote sensing system. Actes INRETS 1994;37:160]165.
Nikolaou K, Ganos T, Triandafyllis G. Influence of CeO 2 catalytic system in vehicle emissions and fuel consumption reduction. Fres Environ Bull 1998a; 7a:in press. Nikolaou K, Tsilikas N, Papaioannou S, Triandafyllis G. Vehicle emissions reduction in correlation to the accumulation of km using a CeO 2 catalytic system. Proceedings of the World Automotive Congress FISITA ’98, Paris, France. Paper F98T619, 1998:10. Nikolaou K. Evaluation of a system for the vehicle fuel consumption and pollutant emissions decrease, Žin Greek.. OMPEPT Technical Report. Thessaloniki, Greece, 1996:44. Nikolaou K. Results evaluation of vehicle emission reduction tests using a rare earths catalytic system. In: Marcatos NC, Rakopoulos CD, Manias NS, editors. Proceedings of the 1st European Conference on Clean Cars. National Technical University of Athens, Greece, 1997:413]420. Pattas K, Samaras Z, Sherwood D, Umehara K, Cantiani C, Aguerre Chariol O, Barthe P, Lemaine J. Cordierite filter durability with cerium fuel additive: 100,000 km of revenue service in Athens. SAE Paper No 920363, 1992:289]301. Trovarelli A, De Leitenburg C, Dolcetti G. Design better cerium-based oxidation catalysts. Chemtech 1997; 27Ž6.:32]37.
Emissions reduction of high and low polluting new technology vehicles equipped with a CeO 2 catalytic system K. NikolaouU Organization for the Master Plan and En¨ ironmental Protection of Thessaloniki, 4 Angelaki St., 54636 Thessaloniki, Greece
Abstract The efficiency of a catalytic system that provides the vehicle combustion chamber with an adequate amount of cerium oxide ŽCeO 2 ., without affecting the operational parameters of the engine, has been studied for pollutant emissions reduction. New technology gasoline engine passenger cars, equipped with this catalytic system, have been driven on their normal route by the same drivers, in order to obtain the same traffic conditions and the same driving mode, as far as possible. These vehicles were tested for CO and HC emissions before and after the installation of the catalytic system. The new technology passenger cars examined have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the CeO 2 catalytic system.. The two categories are: Ža. high polluting cars with CO and HC emissions above the implemented standards; and Žb. low polluting cars with emissions below the standards. Both car categories equipped with the CeO 2 system, present important reduction of the pollutant emissions. The results are interpreted statistically and they are correlated with other studies. Q 1999 Elsevier Science B.V. All rights reserved. Keywords: Cerium oxide; Catalytic system; Vehicle emissions; Carbon monoxide; Hydrocarbons
1. Introduction The primary pollutants like carbon monoxide ŽCO. and hydrocarbons ŽHC. are strongly related to the vehicle emissions and they determine con-
U
Tel.: q30-31-224950; fax: q30-31-224720. E-mail address: [email protected] ŽK. Nikolaou.
siderably the photochemical air pollution in an urban area. Cerium is widely known as one of the catalytically active components used to remove pollutants from vehicle Žauto-exhaust . emissions. The active form of Ce is CeO 2 Žcerium dioxide. or ceria or ceric oxide which is the most stable oxide of cerium. When cerium salts are calcined in air or oxygen-containing environments, tetravalent
0048-9697r99r$ - see front matter Q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 9 9 . 0 0 1 9 1 - 6
72
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Ce ŽIV. oxide is formed. The sesquioxide, Ce 2 O 3 with trivalent Ce ŽIII., can be prepared in strongly reducing conditions but is unstable in the air readily converting to the dioxide. Cerium has one of the highest free energies of formation for an oxide ŽKilbourn 1992, 1993, 1994.. Current three-way catalytic converters contain finely divided ceria dispersed within the washcoat. CeO 2 is known to improve the dynamic performance for the removal of CO Žcarbon monoxide., NO x Žnitrogen oxides. and HC Žhydrocarbons. under conditions with rich-lean airrfuel oscillation in the automotive exhaust. Structural and energetic factors play an important role in the development of a new generation of automobile exhaust catalysts containing CeO 2 doped with ZrO 2 andror other rare earth oxides such as PrO x , Y2 O 3 and La 2 O 3 . These new catalysts possess high oxygen storage capacity, improved thermal stability and enhanced catalytic properties ŽTrovarelli et al., 1997.. Another application is the use of cerium as a fuel additive. Studies on diesel engine buses operated on a cerium-based fuel additive concluded that CeO 2 and cordierite filter interaction is limited ŽPattas et al., 1992.. A catalytic system containing a group of rare earths, with the most prevalent being CeO 2 , providing the vehicle combustion chamber with ceria nanoparticles in order to optimise the combustion and reduce the vehicle pollutant emissions, has been tested and operated in many countries around the world like: USA, Canada, UK, Japan, Belgium, Mexico and Greece. The results of the last decade of these vehicle emission reduction
tests, using the CeO 2 system, showed an important reduction of CO, HC, NO x and particulate emissions ŽNikolaou, 1996.. The main idea of this catalytic system is to provide the combustion chamber with an adequate amount of cerium oxide ŽCeO 2 ., without affecting the operational parameters of the engine Žsee Fig. 1.. The system’s cylindrical metal canister contains a group of rare earth compounds, with the most prevalent being cerium oxide. A venturi-created vacuum, pulls filtered ambient air through the device. The cerium oxide enriched air travels from the device to the engine’s air induction system via a rubber connector hose. In the combustion chamber, micro amounts of cerium oxide catalyse the combustion reaction, lowering average combustion temperature and improving engine performance ŽNikolaou, 1996, 1997; Nikolaou et al., 1998a.. During the first 3000]5000 km Ždepending on the engine state., this catalytic system removes carbon-build-up from valves, valve settings and other internal engine surfaces. After this clean-up phase, the system yields its full potential and reduces the vehicle pollutant emissions and simultaneously the vehicle fuel consumption. The amount of CeO 2 will perform for approximately 65000]75000 km, or the equivalent, depending on the amount of idling. Once spent, the metal canister can be replaced within minutes. Because of the fact that there are no moving parts in the device, no maintenance is required. The system can be retrofitted on gasoline, diesel or alternative fuel-operated vehicles.
Fig. 1. The CeO 2 catalytic system procedure.
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
The efficiency of this system in diesel and gasoline engine vehicles has been evaluated in previous studies, using various criteria. A study on diesel engine vehicles Žurban public transport buses and taxis., equipped with the CeO 2 catalytic system showed that the older and higher polluting diesel engine cars present the lower percent reduction during the first kilometres of operation with the catalytic system Ž29% reduction of particulate emissions after 8000 km. and 43% after the clean-up phase. The newer diesel engine cars present the maximum reduction Ž93%. of the particulate emissions during the first 8000 km. It has been also observed as a significant fuel consumption reduction, by a minimum of 10% ŽNikolaou, 1997.. Another study on gasoline engine passenger cars equipped with the CeO 2 catalytic system was realised using as criterion their mileage. The old technology cars Žwithout three-way catalyst ., after 1 km of system use, present an increase of CO and a small reduction Ž13]14%. of HC emissions. They present reduction of CO Ž10]18%. and HC Ž26]31%. emissions, after 3000 km of system use. The older new technology cars equipped with three-way catalyst, after 1 km of system use, present reduction of CO Ž54]77%. and HC Ž49]55%. emissions. They present a better reduction of CO Ž79]85%. and HC Ž59]82%. emissions, after 3000 km of system use. The newer technology cars equipped with three-way catalyst, after 1 km of system use, present reduction of CO Ž91]94%. and HC Ž61]65%. emissions. They present a better reduction of CO Ž96]97%. and HC Ž72]82%. emissions, after 3000 km of system use ŽNikolaou et al., 1998a.. Similar results were obtained in a parallel study, where it has been determined the influence of this catalytic system on the emissions reduction in correlation to the accumulation of km, for various vehicles Žcommon car, car with uninstalled threeway catalyst, car with turbo engine. and on fuel consumption reduction Ž10]20%. with measurements on an electronic dynamometer ŽNikolaou et al., 1998b.. In this study, 34 new technology gasoline engine passenger cars, equipped with the CeO 2 catalytic system were tested for CO and HC emis-
73
sions before and after the installation of the system. The examined passenger cars have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the catalytic system.: cars with emissions above and below the implemented standards.
2. Materials and methods During 1996]1997 in Thessaloniki, 34 new technology passenger cars equipped with threeway catalytic converters ŽTWC. and using unleaded gasoline were driven on their normal route by the same drivers, in order to obtain the same traffic conditions and the same driving mode, as far as possible. For each of the 34 passenger cars, the following parameters have been examined: model year, engine size Žl., number of kilometres before the installation of the system Žmileage., number of kilometres after the installation of the system, CO Ž%. and HC Žppm. emissions at 900 rev.rmin and 2500 rev.rmin: before,1 kilometre after and 3000 km after the installation of the CeO 2 catalytic system. The CO and HC emissions were measured by the non-dispersive infrared radiation ŽNDIR. absorption method, in order to be in accordance with the reference method of the relative Ministerial In Common Act: FEK 829rBr94 of the Hellenic State and the directives of the European Union. The examined new technology passenger cars have been divided into two categories using as criterion the level of their initial emissions Žbefore the installation of the CeO 2 catalytic system. with reference to the implemented standards for CO and HC vehicle emissions. The implemented standards are: Ža. CO, 0.5% at 900 rev.rmin; Žb. CO, - 0.3% at 2500 rev.rmin; Žc. HC, - 120 ppm at 900 rev.rmin; and Žd. HC, - 100 ppm at 2500 rev.rmin. Passenger cars having emissions above the three of the four Žabove mentioned. standards, are characterised as high polluting cars. Passenger cars having emissions below the two Žat least. of
74
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Fig. 2. The CO average emissions at 900 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
the four standards, are characterised as low polluting cars. Both categories have cars with: model year from 1991 to 1996, various mileage from 20 000 to 150 000 km Žaverage 70 000 km. before the installation of CeO 2 catalytic system and various engine size from 1.3 to 2.0 l Žaverage 1.5 l.. Consequently, the only difference between the two car categories is the level of their initial emissions. 3. Results Fig. 2 represents the CO average emissions Žat 900 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 89% reduction after 1 km and 3000 km. The low polluting cars present 79% reduction after 1 km and 84% reduction after 3000 km, with reference to the initial emissions. Fig. 3 represents the CO average emissions Žat 2500 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 58% reduction after 1 km and 95% reduction after 3000 km. The low polluting cars present 74% reduction after 1 km and 94% reduction after 3000 km, with reference to the initial emissions. Fig. 4 represents the HC average emissions Žat 900 rev.rmin. for each category of the examined new technology passenger cars before the instal-
Fig. 3. The CO average emissions at 2500 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
lation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 55% reduction after 1 km and 67% reduction after 3000 km. The low polluting cars present 54% reduction after 1 km and 70% reduction after 3000 km, with reference to the initial emissions. Fig. 5 represents the HC average emissions Žat 2500 rev.rmin. for each category of the examined new technology passenger cars before the installation of the CeO 2 catalytic system and after 1 km and 3000 km using this system. The high polluting cars present 59% reduction after 1 km and 85% reduction after 3000 km. The low polluting cars present 59% reduction after 1 km and 80% reduction after 3000 km, with reference to the initial emissions.
4. Discussion and conclusions The examined new technology Žwith three-way catalytic converters-TWC. passenger cars present an average reduction of CO and HC emissions of the order of 67]95% after the installation of the CeO 2 catalytic system Žafter accumulation of 3000 km of system use.. This percentage does not include the emissions decrease resulting from the fuel consumption reduction Ž10]20%. after the installation of the system ŽNikolaou et al., 1998a,b.. The high polluting new technology cars Žpassenger cars having emissions above the three of the four implemented emissions standards. present 58]89% average reduction of CO and
K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
Fig. 4. The HC average emissions at 900 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
55]59% of HC emissions during 1 km after the installation of the CeO 2 catalytic system. These cars present 89]95% average reduction of CO and 67]85% of HC emissions, after 3000 km of system use. Before installation of the CeO 2 system, 100% of the high polluting cars present emissions of CO at 2500 rev.rmin and HC at 900 rev.rmin above the standards and 77% of CO at 900 rev.rmin and HC at 2500 rev.rmin. After the installation, 100% of these cars present emissions below the standards except a small percentage Ž8%. of the cars, which continue to have emissions of HC at 900 rev.rmin above the standards. The low polluting new technology cars Žpassenger cars having emissions below the two of the four implemented emissions standards. present 74]79% average reduction of CO and 54]59% of HC emissions, 1 km after the installation of the CeO 2 catalytic system. These cars, after 3000 km
Fig. 5. The HC average emissions at 2500 rev.rmin, for high and low polluting new technology passenger cars before Ž0 km. and after Ž1 km and 3000 km. the installation of the CeO 2 catalytic system.
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of system use, present 84]94% average reduction of CO and 70]80% of HC emissions. Before the installation of the CeO 2 system, 93% of the low polluting cars present emissions of CO at 900 rev.rmin below the standards, 59% of CO at 2500 rev.rmin, 73% of HC at 900 rev.rmin and 91% of HC at 2500 rev.rmin. After the installation, 100% of these cars present emissions below the standards except a small percentage Ž9%. of the cars, which continue to have emissions of CO at 2500 rev.rmin above the standards. These results show that both categories Žhigh and low polluting. of the new technology passenger cars present the lower percent reduction of CO and HC emissions during the first kilometre and a better percent reduction during the next 3000 km of operation with the CeO 2 catalytic system. This is due to the fact that during the first kilometre, this catalytic system removes carbon build-up from internal engine surfaces. After this clean-up phase, the system yields its full potential and all the cars Ževen the high polluting cars. present emissions which are considerably below the implemented standards. For the small percentage Ž8]9%. of the cars, which present emissions above one standard Žonly. for each category, it can be assumed that these cars have a longer clean-up phase Žbecause of their engine status: high mileage and maintenance-regulation problems. in order to present the best possible pollutant emissions reduction. Consequently, additional reductions can occur as these cars accumulate additional kilometres, equipped with the catalytic system, as it has been demonstrated in other works ŽNikolaou, 1997; Nikolaou et al., 1998a.. These results and conclusions are in accordance with those observed in other studies ŽNikolaou, 1996, 1997; Nikolaou et al., 1998a,b.. The observed reduction of CO and HC emissions of the new technology cars is of great importance for the reduction of the total vehicle emissions, because it is well known that only a small percentage of vehicles Ž10]20%. contribute to more than half of CO and HC total vehicle emissions ŽNikolaou and Stedman, 1993; Nikolaou et al., 1994.. These vehicles Žmainly with maintenance
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K. Nikolaou r The Science of the Total En¨ ironment 235 (1999) 71]76
and regulation problems. are not only old technology or old model vehicles. The newer polluting vehicles are more numerous and dominate the total fleet emissions and consequently, it is important to place more focus on their emissions reduction. References Kilbourn B. Cerium. A guide to its role in chemical technology. New York, USA: Molycorp, 1992:42. Kilbourn B. A lanthanide lanthology. Part I, A-L. New York, USA: Molycorp, 1993:61. Kilbourn B. A lanthanide lanthology. Part II, M-Z. New York, USA: Molycorp, 1994:55. Nikolaou K, Stedman D. Remote sensing of vehicle emissions-case study: Thessaloniki, Greece. Com Con 1993;4:80]86. Nikolaou K, Stedman D, Papaioannou S, Zoumakis N, Kelesis A. Determination of parameters influencing the vehicle emissions in Greece, using a remote sensing system. Actes INRETS 1994;37:160]165.
Nikolaou K, Ganos T, Triandafyllis G. Influence of CeO 2 catalytic system in vehicle emissions and fuel consumption reduction. Fres Environ Bull 1998a; 7a:in press. Nikolaou K, Tsilikas N, Papaioannou S, Triandafyllis G. Vehicle emissions reduction in correlation to the accumulation of km using a CeO 2 catalytic system. Proceedings of the World Automotive Congress FISITA ’98, Paris, France. Paper F98T619, 1998:10. Nikolaou K. Evaluation of a system for the vehicle fuel consumption and pollutant emissions decrease, Žin Greek.. OMPEPT Technical Report. Thessaloniki, Greece, 1996:44. Nikolaou K. Results evaluation of vehicle emission reduction tests using a rare earths catalytic system. In: Marcatos NC, Rakopoulos CD, Manias NS, editors. Proceedings of the 1st European Conference on Clean Cars. National Technical University of Athens, Greece, 1997:413]420. Pattas K, Samaras Z, Sherwood D, Umehara K, Cantiani C, Aguerre Chariol O, Barthe P, Lemaine J. Cordierite filter durability with cerium fuel additive: 100,000 km of revenue service in Athens. SAE Paper No 920363, 1992:289]301. Trovarelli A, De Leitenburg C, Dolcetti G. Design better cerium-based oxidation catalysts. Chemtech 1997; 27Ž6.:32]37.