Together with Emitec, we evaluated the potential of such a preturbo catalyst, shown here on the picture in the left upper corner. The addition of these catalysts to the standard system allowed on a modern diesel car to further improve the tailpipe emissions by about 30 %, as is apparent from the cumulated emissions over the NEDC, the red line with preturbo catalyst and the blue line with only the standard system
Dr. vora ppt chapter 4 aftertreatment
Catalytic Converters Dr. K. C. Vora
Importance of Environment & Technologies Environment Technologies 2010 System Integration Energy consumptionImportance Functions 2000 Electronics d System Integrate Emission CO2 1990 ics Electron Emission CO/HC/NOx m lic Syste Hydrau year year
Air Quality Impact of the Catalytic ConverterMore than 8x108 tons of combinedHC, CO, NOx were abated by 2000References: Heck and FarrautoMonograph: Vora & Ghosh.
Great success stories are continuing 100 % Engine Exhaust The development of automotive emission control technology over the > 98 % last three and a half decades is one of the greatest environmental success <2% stories of this century. O2 H2O CO2 Compared to the 1960s the emission N2 Catalyst of motor vehicles has dropped to a fraction, the fuel economy has doubled.< 0.05 % O2 > 1.95 % H2O CO2 HC N2 CO NOx
A Catalytic Converter• Catalytic converters transform NOx, CO and HC into N2, CO2 and H2O Can or shell Mat Ceramic Substrate with Catalytic Coating N2 CO2 H2O NOX CO HC
Working: Theory of Active Sites The Energy Path of a Catalysed & Uncatalysed Reaction.The active site may be viewed as the point on the catalyst material crystalline where theelectronic forces are optimum for the catalytic reaction to take place.CO and O2 are chemisorbed on the catalyst and can react readily because of their proximity andorientation. The process of adsorption also results in weakening of the bond between the atomswithin the CO molecule because some of the energy is shared with the surface. Thus, theadsorbed atoms of the molecules are less tightly bonded to the molecule and more easilyattracted to other atoms such as oxygen. The reaction between CO and oxygen is thus easierand more rapid. The products having achieved a lower energy state must desorb at the sametemperature, freeing the active site for additional reactions.
High cell density metal substratesIf the cell density is increased with the same constructionsize, the effective surface is enlarged accordingly.This considerably increases the efficiency of the system.Range: 50 to 1000 CPSI / 0.03 to 0.05 mm foil thickness.
TURBULENT METALLIC SUBSTRATES These foils generate turbulence in the exhaust gas stream and so greatly increase the efficiency of the catalyst.Types:•Radial flow near the wall inthe channels (TS design®)•A reduction of diffusionpaths and the hydraulicdiameter and a repeat of theentrance flow (LS design)•Radially open, perforatedstructures (PE designTM)•A combination of PE andLS structures.
DATA METALLIC CERAMIC SUBSTRATE SUBSTRATE Wall thickness (mm) (uncoated) 0.04 0.2-0.15 Cell density (epsi) 400 400 Clear cross section (%) 91.6 67.1-76.0 (uncoated) Specific surface area(m2/}) 3,2 2.4-2.8 Thermal conductivity(W/m.K) 14-22 0,1-0.8 Heat capaeity (kJ/kg.K) 0.5 1.05 Density (g/cm3) 7.4 2.2-2.7 Coefficient of Thermal 15 1 expansion (AL/LxlO"6/K) Max. short duration operating 1500 1200 temperature(°C) COMPARISON BETWEEN METALLIC & CERAMIC SUBSTRATES
Parameters Ceramic cell density Metallic cell (cpsi) density (cpsi) 200 300 400 400 500 600 Cell area, mm2 2.30 1.43 1.21 1.50 1.10 0.97 Surface to volume ratio, 189 220 2790 323 3580 3940 m"1 0 5 0 Open Frontal Area, % 70 60 76 89 86 83 Wall thickness, mm 0.28 0.30 0.15 0.05 0.05 0.05 COMPARISON BETWEEN CERAMIC AND METAL SUBSTRATE PARAMETERS
Pt Pd Rh Mine Ratio, upper Deposit 100 40 8 Catalyst Ratio, 1989 TWC 100 0 20 Approx, Cost in U.S,$/oz in 1989 600 140 1300 Approx. Cost in U.S,$/oz in 1994  400 140 800 DISPARITY OF PGM RATIOS AND COSTS
MICROSCOPTC STRUCTURE OF A COATED TYPE CATALYST
BENCH TEST COMPARISON OF BASE METAL V/S NOBLE METAL CATALYST
Sr. Noble Metal Non-Noble Metal oxides No. 1. Technology well-known and proven. ot commercially proven so far. N2. Pt-Pd as 2 way converter catalyst. Perovskite oxides LaCoOs/LaMnOs, Lai-xSixCoi-yMyOs complex oxides. 3. Pt-Pd/Rh proven combination for 3 -way Binary Cu-Cr oxide not established My. converter (Ratio 10:1, Europe 5:1, Mine Ratio 16.5:1), 4. Lower light-off temp., active even at Active from 250°C onwards. 100°C. 5. Conversion efficiency high at high Conversion efficiency tends to flatten temperatures. out at high temperatures, but modifications are equally active. 6. Narrow A/F for efficient 3-way NO + CO-»1/2N2 + CO2 Possible in two conversion. stages. 7. Not tolerant to high, continuous Pb level Could be made Pb-tolerant by a right in gasoline. catalyst formulation. 8. Not affected by SO2 (20 ppm SO2 in Poisoned by SO2. Development of SO2 exhaust for 0.03 wt% S in gasoline). resistant formulations. 9. Ceramic substrate, washcoated with No Washcoat on ceramic substrate. alumina and deposited with Pt/Rh (0. Direct deposition of Oxide precursors. 16/0.03 wt%Pt/Rh). (5-15 wt% as oxides). COMPARISON OF NOBLE V/S. NON-NOBLE CATALYST
CLAMSHELLCANNING OF CATALYTICCONVERTER(Alternative method isTerniquette)
EFFECTIVENESS OF CLOSED-LOOP &OPEN-LOOP THREE-WAY CATALYSTS
EMISSION DATA OF 4-STROKE ENGINEDMOTORCYCLE FITTED WITH CATALYTIC CONVERTER
EMISSION DATA OF 2-STROKE ENGINED MOPED FITTED WITH CATALYTIC CONVERTER
MICROSTRUCTURE OFA FRESH METALLIC MICROSTRUCTURE OFA FRESH CERAMIC CONVERTER CONVERTER MICRO STRUCTURE AFTER WASHCOAT ADHESION TEST MICROSTRUCTURE OFA FRESHCERAMIC CONVERTER AFTER SOME MICROSTRUCTURE SHOWING HOURS OF ENGINE RUN POISONING BY CONTAMINANATS
Automotive Emissions Importance of Cold Start Tailpipe HC Emissions (FTP Bag 1) 0.025 1500Tailpipe HC Mass (g/s) Temperature, (Deg F) 0.02 1200 0.015 900 Catalyst "Light-Off" X Temperature 0.01 600 0.005 300 0 0 0 100 200 300 400 500 Time (s)