1. Nano Catalysis Reduce exhaust emissions with catalytic converters
Reduce precious metal use through nanoparticles
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2. Pd: A Catalyst
HC (hyrdocarbons) & CO require oxygenation —> CO2 & H2O
NOx requires reduction —> N2 & O2
NOx is an issue at high temperatures and thus not at start-up
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3. Overview Short videos on toxic pollutants in the air
What is a cat?..It's a catalytic converter
History
Pollution- types, chemical rxn's, agencies, methods used to ↓ emissions
Structure
Nano techniques for manufacture..Top down vs Bottom up
Future work
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4. What is a cat?
Catalytic converters use catalysts, which speed up chemical rxn's, and consist of the precious metals: Pt, Pd & Rh over a ceramic base.
Pt & Pd oxidize CO & UHC (unburned hydrocarbons)… CDR (carbon dioxide removal) is achieved with the CO2ube. CO2 is a greenhouse gas.
Pt & Rh reduce NOx ..NOx forms when the combustion chamber is >2700°C
Results:
CO & UHC are ↓ 97%
70% of CO & UHC occur during cold-start emissions, therefore before the “light-off” period (when temperatures are <300°C)
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5. History Lead (fuel additive TEL) poisoned cat! Eugene Houdry
TEL was added in the 1920’s to raise octane levels
TEL was significantly reduced by the EPA in 1976.
Eugene Houdry
studies of smog in LA were published
Founded the company Oxy-Catalyst to develop cats for gasoline engines. Idea was ahead of its time
1973- LA air pollution episode
1974- The first cat in the US Developed by John J. Mooney and Carl D. Keith at the Engelhard Corporation
1975- Every new car has to have a cat EPA mandate
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6. Videos..FYE Video 1 Video 2 Video 3
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7. Pollution 6 harmful pollutants Ideal fuel only has HC's Smog
CAA (Clean Air Act) requires EPA to set NAAQS (National Ambient Air Quality Standards)
6 harmful pollutants
CO, Pb, NOx, SO2
PM- particulate matter (PM2.5 is thought of and not PM10)
O3- ground level ozone. This is a secondary pollutant resulting from NOx, VOC (volatile organic carbons) & sunlight
Ideal fuel only has HC's
Actual fuel has N, S, P, Fe, Cu, Ni, Cr, Si.
Can pre-treat via further processing but there is an added cost.
Smog
Smog- smoke & fog. CO, NOx, VOC (by means of negative crankcase ventilation & tailpipe), SO2 & HC
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8. Chemical Rxn's of Isooctane/Gasoline/Petrol
Complete combustion:
C8H18 + z(O N2) → a(CO2) + b(H2O) z(N2)
C: a = 8, H: b = 9, O: z = a + (1/2)b = 12.5
3.76? X/0.79 = 1/0.21 → X = (air is 79% N, 21% O)
Incomplete combustion:
C8H18 + z(O N2) → a(CO2) + b(CO) + c(H2O) + d(H2)
z = 12.5, C: 8 = a + b, H: 9 = c +d, O: 12.5 = a + (1/2)b + (1/2)c
4th eq: Water gas shift rxn: CO & H2 = water gas
O + N2 → NO + N
N + O2 → NO + O2
N + OH → NO + H
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9. Chemical Rxn's in Catalysis
Oxidation:
C + H2O → CO + H2
2CO + O2 → 2CO2
C8H O2 = 8CO2 + 9H2O
RH → R → RO2 → RCHO → RCO → CO where R is a HC radical
CO + OH ↔ CO2 + H
Reduction
2NOx → N2 + O2x
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10. Agencies Air Pollution Control Act, 1955
Clean Air Act, Clean Air Act- 189 hazardous air pollutants were defined.
Motor Vehicle Air Pollution Control Act, 1965
Air Quality Act, 1967
Clean Air Act Amendments, 1970, 1977, 1990
US Environmental Protection Agency (USEPA)..Green Chemistry Pgm
National Ambient Air Quality Standards (NAAQS)
FL State Implementation Plan (SIP)
National Emission Standards for Hazardous Air Pollutants (NESHAP)
New Source Performance Standards (NSPS)
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11. ↓ Air Pollution (i.e. GHG & toxicity)
Improve engine combustion
Reformulation of fuels (pre-treatment)
Contains oxygenates (i.e. alcohol or ether..ethanol & MTBE).
2% O added to burn cleaner-> 11% MTBE. 87% of the additive is MTBE not ethanol.
Ethanol- highly volatile (high vapor pressure) ∴ evaporates readily especially in summer creating smog, and separates from gasoline.
30% of gasoline uses it. It is in 19 states & D.C..
Oxidation/reduction catalysts
Exhaust Gas recirculation (EGR)..most SI & diesel engines have it
Avoid cold start- Thermal management systems (TMS)
Phase change material (PCM)- Sodium acetate- latent heat storage, solid-liquid
Variable-Conduction Insulation (VCI)- metal hydride -stores heat to minimize cold start emissions
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12. GHG emission by Economic Sectors
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13. Cost Breakdown TWC
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14. Shorten light-off time
Light-off temp- temp at which 50% of the emissions are being converted as they pass through the catalytic converter
EHC- electrical heating of catalytic convertors (2kW- using car battery, issue with battery capacity since it requires power for 25-30s)
APEHC- alternator powered electrically heated catalyst.
5-mile trip, starting the car cold generates about
30% more NOX and 60% more CO than starting the car when it is warm
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15. Cat UNF ST: Nanofabrication EML 6933 Brian White
Determines A/F ratio then data sent RT to control electronic fuel injection and thus emission control
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16. TWC – oxidizing/reducing cat 1981- two way-> three way to reduce NOx
Reaction of Exhaust with Catalyst (TWC) Resulting in Clean Emissions
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17. Platinum Group Metals - PGM
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18. Cost $ - Precious Metals
3 – 7 g of Pt per cat
Relative amounts of each metal: Pt:Pd:Rh = 5:2.5:1
Cost of each metal/cat: $354-$152: $90-$39: $48-$21
70 – 90% less precious metals by using 5 nm diameter nanoparticles, which have a higher surface area to volume ratio
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19. Design/ Structure 1) Catalyst support/ substrate- 2) Wash coat-
First.. Pellet-type Al2O3
Then.. ceramic monolith w/ “Honeycomb” structure
Thin walled- ceramic (i.e. cordierite) or metal block (i.e. Al2O3, Kanthal (FeCrAl))
Parallel channels- 0.5 – 10 mm dia. Straight paths. Why?
2) Wash coat-
Carrier for the catalytic materials, layer of inorganic metal oxides (i.e. Al2O3, SiO2, & TiO2)
Heterogeneous catalyst
Rough- to ↑ surface area
3) Noble metals-
Pt, Pd, Rh (Ca, Pb, As tailings)
Ce, Fe, Mg, Zr & Ni, Cu are also used but create toxic by-products
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20. Design/ Structure
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21. Potential Issues Catalyst Bed Deactivation
Thermal deactivation- sintering, solid-state transform
Fouling- physical deposition of substances
Crushing- mechanical forces on catalyst (high velocity exhaust gases)
Poisoning- occurs due to layer forming on the wash-coat surface (i.e. Zn, Ca, & Mg phosphates and CePO4, Ce(PO3)3, & AlPO4
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22. Nano Catalysis
Pt nanoparticles (colloidal spheres) supported on functionalized TiO2
Nanoporous silica layer, as cathode catalyst, improves the thermostability of the Pt, preventing sintering/agglomeration of Pt.
UNF ST: Nanofabrication EML 6933 Brian White

23. Zeolite
Microporous, aluminosilicate minerals used as commercial adsorbents and catalysts
Alumina & silica with sodium hydroxide
Sodium aluminate & sodium silicate
Abundance of cations such as Na+, K+, Ca2+, Mg2+, etc.
Large surface area
Molecular sieve- sorts molecules on a size exclusion process
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24. Metal-Organic Framework (MOF)
MOF has exposed sites of metal cation (Mg2) that attach to CO2
CO2 is adsorbed to a greater extent by appending diamines to the open coordination sites
Coordination network- A metal ion or cluster of metal ions and an organic molecule (ligands- anions, linker, or complexing agent)
1 gram has a surface area of greater than 3 football fields!
Well ordered, ultra-porous crystals
Chemisorption- strong binding
Physisorption- light relaxing of molecule on surface
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25. MOF
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26. SWNH’s (Single Walled Nanohorns)
Derived from SWNT’s
C or TiO2
Coated with (d < 5 nm) Pt nanoparticles
40–50 nm in tubule length
2–3 nm in diameter
20° cone opening angle
1000's of SWNH’s form the ‘dahlia-like' and ‘bud-like’ structured aggregates with d = nm.
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27. Videos Crucible- http://www.tubechop.com/watch/5698522
Zeolite-
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28. Testing methods
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29. Monodisperse Particles
Ensure particles are the same size using dynamic light scattering
Monochromatic light source (i.e. laser) is sent through a polarizer that hits the particles creating a speckle pattern (interference of diffracted light)
Diffracted light is then sent through another polarizer
Repeated at short time intervals
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30. Future Work
The goal is to grow different shapes that make surfaces more catalytically active
At the moment only about 10 percent of the platinum particles in a catalytic converter are active
Save cost by using less expensive cobalt catalyst material
Increase catalysis activity through tetrapod structure (crystal structure of a tetrahedral shape)
Nano and microscale patterning methods with varying degrees of accuracy exist (i.e. heteroepitaxy)
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31. References UNF ST: Nanofabrication EML 6933 Brian White
1) Shah, R.. “Automotive Air Pollution and its Control by Catalytic Converters.” University of Illinois at Urbana-Champaign. (2013).
2) Lecture Series Heterogeneous Catalysis: Catalyst Deactivation.” (2011).
3) Heberling, M.. “Government-Reformulated Gas: Bad in More Ways than One. The Freeman.
Reformulated Gas Is Useless at Best, Expensive and Harmful at Worst.” (2003)
4) Stafford, N.. “Catalytic Converters go Nano.” Royal Society of Chemistry. Web. (2007).
5) Thole, J.. “Nanotechnology promises better catalytic converter.” Web (2010)
6) Tilley, R.. “Catalytic Converters and Platinum Nanoparticles.” The University of Waikato. (2008).
7) Serp, P., Philippot, K.. “Nanomaterials in Catalysis.”
8) Suib, S.. “New and Future Developments in Catalysis: Catalysis by Nanoparticles.”
9) Metal-Organic Frameworks: CO2 Capture”. Long Group. Web.
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32. Quiz ?’s
1) What precious metals are used for oxidation and which ones for reduction?
2) US EPA mandates what and in which year?
3) What does lead do besides being a neurotoxin?
4) What does the acronym TWC stand for?
5) a) The parallel channels of the monolith ceramic should have what type of channels and why? Hint: so engine performance stays high.
b) Pt is embedded in what type of nanofiber?
c) i) What does a catalyst do?
c) ii) Name at least one nano-catalytic method?
d) What is nanofabrication and how can it improve cat's?
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33. Answers Pt, Pd – oxidize & Pt, Rh – reduce
Every car has a cat as of 1975
Poisons cat
Three-way catalytic converter
a) Straight paths to decrease pressure loss.
b) TiO2
c) i) Speeds up a rxn
c) ii) MOF’s, SWNH’s, zeolite, crucible
d) Manufacturing materials (or devices) in the size range of nm. Use less material through increased surface area to volume ratio.
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