Approaching the 150 C Challenge with Passive Trapping Materials and Highly Active Oxidation Catalysts

Transcription

1 Approaching the 150 C Challenge with Passive Trapping Materials and Highly Active Oxidation Catalysts Andrew J. Binder1, Eleni Kyriakidou2, Todd J. Toops1, James E. Parks II1 1 Fuels, Engines, and Emissions Research Group, Oak Ridge National Laboratories 2 Chemical and Biological Engineering, University at Buffalo This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy Vehicle Technology Program ORNL is managed by UT-Battelle for the US Department of Energy

2 Acknowledgements ORNL Low Temperature Catalysis Team Eleni Kyriakidou*, Jae-Soon Choi, Todd J. Toops, James E. Parks DOE funding Advanced Combustion Systems Ken Howden and Gurpreet Singh Access to instrumentation through Michael Lance (ORNL) Micrographs and elemental maps captured using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities DOE Basic Energy Sciences Program Center for Nanophase Material Science (ORNL) user program 2 SECS * Eleni Kyriakidou is now an assistant professor in the Chemical and Biological Department at the University at Buffalo (SUNY)

3 Demand for Low Temperature Catalysis Develop new emission control technologies to enable fuel-efficient engines with low exhaust temperatures (<150ºC) to meet emission regulations Goal: 90% Conversion at 150ºC Greater combustion efficiency lowers exhaust temperature Catalysis is challenging at low temperatures Emissions standards getting more stringent Higher efficiency engines have lower exhaust temperatures* 400 Fuel Economy Standards 54.5 mpg CAFE by 2025 Fuel Economy Turbo Out Temperature (C) 3 SECS CDC RCCI BMEP (bar) Emissions *Reactivity Controlled Compression Ignition (RCCI) [a Low Temperature Combustion mode] vs. Conventional Diesel Combustion (CDC) >70% less NOx >85% less NMOG 70% less PM EPA Tier 3 Emission Regulations (phased in)

4 HC/NO x Trap paired with DOC could greatly improve cold-start effectiveness Example of a Catalyzed HC Trap. ceramic honeycomb monolith HC Trap Oxidation Catalyst Monolith 275 o C Kim, M.-Y., Kyriakidou, E.A., Choi, J.-S., Toops, T.J., Binder, A.J., Thomas, C., Parks, J.E., Schwartz, V., Chen, J., Hensley, D.K., Appl. Catal. B: Environ. 187 (2016) 181. Nunan, J., Lupescu, J., Denison, G., Ball, D., Moser, D., SAE Int. J. Fuels Lubr., 6 (2013) 430. o Commercial Diesel Oxidation Catalyst (DOC) is able to oxidize all HCs and CO at high temperatures (e.g. T 90% ~ 275 o C) o Zeolites have been proven to be effective in storing cold start HCs. o At higher temperatures, adsorbed HCs desorb from the surface. o Desorbed HCs are oxidized by the DOC leading to near zero HC emissions. 4 SECS 2017

5 DOC Catalyst: Pd/SiO 2 SiO 2 proves to be an active support for Pd catalysts with high durability. Able to synthesize a complete shell around SiO 2 core Pd (1 wt%) deposition solely on ZrO 2 outer shell While employing US-DRIVE low temperature protocols improved activity shown with this technique SiO 2 ZrO 2 Robust after aging at 900 C for 10h Improved initial dispersion technique still needed Temperature ( C) SECS 2017 T₉₀ T₅₀ Aged Degreened samples samples Pd/Zr Si@ Pd/Zr Si@ Pd/Zr Si@ Pd/Zr Si@ Pd/Zr Si@ Pd/Zr Pd/Zr Pd/Zr Pd/Zr Pd/Zr CO CC3H6 3 6 C2H4 2 4 CC3H8 3 8 THC DG 800 C 900 C DG 800 C 900 C DG 800 C CO C 3 H 6 C 2 H 4 C 3 H 8 THC DG = Degreened 900 C DG 800 C 900 C DG 800 C 900 C Si Zr Pd This research was performed, in part, using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities.

6 DOC Catalyst: Pt/SiO 2 + Pd/SiO 2 Significantly increased performance after 800 C aging can be achieved with a Pt+Pd mixture SiO 2 ZrO 2 SiO 2 mixed oxide PGM supported on a shell of ZrO 2 around a core of SiO 2 (SiO 2 ) Si Zr Pd Pd Si Zr Pd Pt Conversion Conversion (%) or NO (%) 2 ppm CO THC CO CO THC NO 2 THC Hydrothermally aged 800 C/10h Improved low temperature activity observed with Pt+Pd physical mixture Bed loading: 1.8% Pt and 1.0% Pd Also, active with liquid hydrocarbon LTC-D protocol using decane (C 10 H 22 ) Conversion (%) Temperature ( o C) C) C 3 H 6 C 10 H 22 CC 2 H 3 H 4 6 C 2 H 4 C 3 H 8 C 3 H 8 6 SECS Temperature ( o C)

7 Trapping Material: Zeolites Strategy v Understand ZSM-5 and BEA zeolites in HC adsorption and desorption to help optimization. v Systematic variation of key zeolite properties: Cation type (H + vs. Ag +, Pd 2+ ) H 2 O, CO 2 Pore structure (BEA vs. ZSM-5) Zeolite type Si/Al molar ratio Nominal cation form Surface area (m 2 /g) BEA 25 H BEA 25 Ag + /Pd 2+ NM ZSM-5 30 H ZSM-5 30 Ag + /Pd 2+ NM Ion-Exchanged Zeolites. H H 0, 1, 5 wt.% Ag/BEA 1 wt.% Ag/ZSM-5 1 wt.% Pd/BEA 1 wt.% Pd/ZSM-5 ZSM-5 BEA Liu, X., Lambert, J.K., Arendarskiia, D.A., Farrauto, R.J., Appl. Catal. B 35 (2001) 125. Lambert, J.K., Deeba, M., Farrauto, R.J, US Patent 6,074,973 (2000). Nunan, J., Lupescu, J., Denison, G., Ball, D., Moser, D., SAE Int. J. Fuels Lubr. 6 (2013) SECS 2017 Calcination: 500 o C (2 h)

8 Trapping Material: Pd/ZSM-5 Pd Pd Pd/ZSM-5 vs. Pd/Beta vc 3 H 6 adsorption is sensitive to the type of metal. vpd/zsm-5 shows the best C 3 H 6 /NOx trapping ability. Adsorption Conditions: C 3 H 6 : 167 ppm, 200 ppm NO, 10% O 2, 5% H 2 O, balance Ar, Total Flow: 600 sccm, SV: 90,000 h -1 Adsorption Pd/BEA Pd/BEA Pd/ZSM-5 Pd/ZSM-5 C 3 H 6 Feed NO Feed 8 SECS 2017

9 US-DRIVE Low Temperature Aftertreatment Team (LTAT) Protocols: Specific evaluation protocols are defined to ensure that gas streams mimic exhaust conditions accurately Full file at: LTC-D: Low Temp. Combustion Diesel Total HC 1 : 3000 ppm C 2 H 4 : 250 ppm C 3 H 6 : 100 ppm C 3 H 8 : 33.3 ppm *C 10 H 22 : 210 ppm CO: 2000 ppm NO: 100 ppm H 2 : 400 ppm H 2 O: 6 % CO 2 : 6 % O 2 : 12 % Balance N 2 Powder Catalyst Requirements Reactor ID 3-13 mm Catalyst particle size 0.25 mm (60 mesh) Catalyst bed L/D 1 Space velocity L/g-hr For 0.1 g sample, flow sccm 9 SECS 2017

10 Degreening and aging protocols also outlined Aging modes and times outlined to generally reflect the application Degreen: 4h at 700 C Gasoline: 50h at 800 C Lean/Stoich/rich cycling Exotherm while cycling Diesel: 50h at 800 C Also need to be able to survive 800 C for 50 h and be tolerant of sulfur (5 ppm SO 2 for 5h at 300 C) 10 SECS 2017

11 DOC activity baseline Pd/SiO 2 + Pt/SiO 2 (50:50 wt.) is our current highest performer for lean diesel (LTC-D) exhaust conversion. Aged 800C 4hr Exceptional low temperature activity observed with Pt+Pd physical mixture Aged conditions = 800ºC, lean, 4 hrs Bed PGM loading 1.8% wt. Pt 1.0% wt. Pd T 90 = 177ºC and 218ºC for CO and THC, respectively. Propane is a significant challenge and is often responsible for low T 90 values. 11 SECS 2017

12 The Works Trapping + DOC system Combining Pd/ZSM-5 trapping material with highly active DOC bed allows us to hit the 150ºC challenge for CO under lightly aged conditions. Flow Aged 800C 4hr Pd/ZSM-5 SiO 2 Mix Catalyst system reaches a T 90 = 134ºC and 177ºC for CO and HC, respectively Significant release of hydrocarbons and NO x occurs at 162ºC. Propane continues to be a stumbling block for reaching 150ºC THC conversion. Addition of hydrocarbon trap greatly enhances overall performance of the catalyst system. 12 SECS 2017

13 The Works Durability testing Post-aging and sulfation: T 90 = 177ºC and 218ºC for CO and THC, respectively. 5 ppm 300ºC for 5 hours. Desulfation under cycling lean-rich conditions for 30 min at 500ºC, 30s per condition. Aging at 800ºC, 50 hrs, lean conditions Sulfation and long term aging reduce the effectiveness of this system, but overall activity is still improved with respect to DOC baseline. 13 SECS 2017

14 Effects of Aging and Sulfation - DOC Pd/SiO 2 + Pt/SiO 2 DOC mixture was tested to determine the effects of aging on this component of the system. T90 s (ºC) Aged 4 hr 50 hr + Sulfation CO THC C 2 H C 3 H C 3 H C 10 H Protocol aging and sulfation severely hampers DOC mixture hydrocarbon activity. 14 SECS 2017

15 Pd/ZSM-5 Trapping Pd/ZSM-5 trapping material shows high trapping efficiency for hydrocarbons and NO x. C 10 H 22 has the highest trapping efficiency seen. Total Stored (g/g cat ) Total % 3 min % NO x % 38.5% THC C % 56.9% C 2 H % 27% C 3 H % 38% C 10 H % 79% 15 SECS 2017

16 Effects of Aging and Sulfation Pd/ZSM-5 Trapping Aged and sulfated trap loses almost all NOx, C 2 H 4, and C 3 H 6 trapping capability. C 10 H 22 trapping efficiency is largely unaffected. Total Stored (g/g cat ) Total % Δ % NO x ~ 0 0% -10% THC C % -3.4% C 2 H 4 ~ 0 0% -9% C 3 H % -9% C 10 H % -1% 16 SECS 2017

17 Pd/ZSM-5 Release Release Temp Release % NO x 222ºC / 454ºC 94% C 2 H 4 242ºC 9% C 3 H 6 205ºC 59% C 10 H ºC 48% Pd/ZSM-5 shows favorable release temperatures for pairing with a highly active DOC catalyst. Nearly 100% release of NO as NO x across two peak temperatures. Missing carbon balance is most likely CO 2. No significant byproducts (methane, etc ) seen via FTIR. 17 SECS 2017

18 Effects of Aging and Sulfation Pd/ZSM-5 Release Release Temp Release % NO x 217ºC 100% C 2 H 4 N/A N/A C 3 H 6 N/A 0 % C 10 H ºC 94% Aging and sulfation results in an increase in Decane release temperature. A very small NO x release peak can be seen at 217ºC as indication of some small storage. Missing carbon balance is most likely CO 2. No significant byproducts (methane, etc ) seen via FTIR. 18 SECS 2017

19 Pd/ZSM-5 Light-off Trapping ~200ºC Conversion CO ~140ºC THC NO x Pd/ZSM-5 was tested in a cold-start lightoff. Reactants were introduced directly upon ramp. Storage, release, and conversion can all be seen as well as a significant exotherm generated by conversion of hydrocarbons to CO 2 19 SECS 2017

20 Pd/ZSM-5 Light-off Trapping ~236ºC Conversion CO ~150ºC THC NO x Both CO and THC activity are severely effected by durability testing. Storage and release of hydrocarbons (primarily Decane) has shifted later. Conversion occurs later than DOC 20 SECS 2017

21 Summary Addition of trapping material before DOC can greatly enhance system activity for CO, HC, and NO x conversion. Pd/ZSM-5 -> [Pd+Pt]/SiO 2 achieves T 90 s near or below 150ºC for HCs and CO, respectively, after 800ºC 4 hour aging. Aged 800C 4hr 50 hour aging and sulfur tolerance can contribute to loss of activity, but addition of trap still shows significant benefits. Continuing focus is on understanding the specific cause of activity loss. Materials characterization DRIFTS analysis with the goal of determining storage/reaction sites. Aged 800C 50 hr + Sulfation 21 SECS 2017