Lifetime impact of SO2-poisoning of Cu-CHA catalysts for NH3-SCR Peter S. Hammershøi, Anker D. Jensen and Ton V. W. Janssens CLEERS 2018, Ann Arbor, MI

Please Note: This contents of presentation has been published in: [1] P.S. Hammershøi, P.N.R. Vennestrøm, H. Falsig, A.D. Jensen, T.V.W. Janssens, Importance of the Cu oxidation state for the SO 2 -poisoning of a Cu-SAPO-34 catalyst in the NH 3 -SCR reaction, Appl. Catal. B Environ. 236 (2018) 377–383. doi:10.1016/j.apcatb.2018.05.038. [2] P.S. Hammershøi, A.D. Jensen, T.V.W. Janssens, Impact of SO 2 -poisoning over the lifetime of a Cu-CHA catalyst for NH 3 -SCR, Appl. Catal. B Environ. 238 (2018) 104–110. doi:10.1016/j.apcatb.2018.06.039. Please refer to these publications to cite from this presentation. 2/1/2019 Umicore Template 2017

Diesel exhaust and NH3-SCR Diesel exhaust gas contains NOx (NO and NO2) and SO2 (1-2 ppmv) Selective catalytic reduction (SCR) with NH3: 4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O SCR catalysts: V2O5-based, Fe-zeolites and Cu-zeolites 2/1/2019 CLEERS 2018

Background and aims Background: Colder exhaust gas in near future: Better fuel efficiency → lower CO2 emissions Better cold start performance Hybrids Superior low-temperature activity of Cu-zeolites Main disadvantage of Cu-zeolites is SO2-poisoning Questions: What causes the deactivation by SO2? Is the lifetime impact of SO2 prohibitive for practical application? SO2 2/1/2019 CLEERS 2018

What causes the deactivation by SO2? 2/1/2019 NSC 2018

Cu-CHA catalyst and deactivation mechanisms Cu-CHA catalysts Microporous structure SCR activity from Cu sites Blocking of Cu sites by SO2 or, pore-blocking by deposition of ammonium sulfates? CHA framework Adapted from www.iza-structure.org 2/1/2019 CLEERS 2018

Deactivation by blocking of Cu sites SO2 in SCR gas: SO2/Cu lower than 1 No deposition of ammonium sulfate SO2+O2+H2O: SO2/Cu higher than 0 Cu,S interactions! Different trends for SO2/Cu vs temperature – related to Cu,S chemistry? SCR gas: 500 ppmv NO 530 ppmv NH3 10 % O2 5 % H2O 2/1/2019 Adapted from Hammershøi et al. Appl. Catal. B (2018), 236, 377-383 CLEERS 2018

Cu,S interactions by DFT SO2 prefers Z-CuI SO3 prefers Z-CuIIOH Z-CuI + Z-CuIIOH + SO2 Z-CuI··SO2 (ΔE = -1.12 eV) Z-CuIIHSO3 (ΔE = -0.73 eV) SO3 Z-CuI··SO3 (ΔE = -0.89 eV) Z-CuIIHSO4 (ΔE = -1.81 eV) Adapted from Hammershøi et al. Appl. Catal. B (2018), 236, 377-383 2/1/2019 CLEERS 2018

Effect of NH3 on Cu oxidation state SCR-gas conditions Only way to have CuI is to have NH3 present: High [NH3] → CuI Low [NH3] → CuII CuII CuI 2/1/2019 Janssens et al., ACS Catal. 5, 2832-2845 (2015) CLEERS 2018

Effect of temperature [CuI] [NH3] ↓ [CuII] [SO2] SO2 oxidation rate ↑ Increasing temperature: [CuI] [NH3] ↓ [CuII] [SO2] SO2 oxidation rate ↑ [SO3] Low T High T With SCR gas CuI + SO2 CuII + SO3 Without SCR gas CuII + SO2 2/1/2019 CLEERS 2018

Importance of Cu oxidation state SO2 in SCR gas: CuI and CuII present Adsorption effect SO2+O2+H2O: only CuII Increased oxidation rate of SO2 to SO3 Similar trends above 400 °C – effectively similar exposure conditions 2/1/2019 Adapted from Hammershøi et al. Appl. Catal. B (2018), 236, 377-383 CLEERS 2018

What is the lifetime impact of SO2? 2/1/2019 CLEERS 2018

SO2-poisoning behavior of Cu-CHA Low-temperature NOx conversion drops after SO2 exposure Heating to 550 °C partially restores NOx conversion 2/1/2019 CLEERS 2018

Impact of SO2 concentration and exposure time Deactivation appears to depend on: SO2 concentration · exposure time [ppm·h] Deactivation can be accelerated 2/1/2019 CLEERS 2018

SO2/Cu exposure over a catalyst lifetime Assumptions for lifetime SO2 exposure of a Cu-CHA SCR catalyst in a heavy-duty vehicle Distance: 800 000 km Fuel efficiency: 30 L/ 100 km Sulfur content in diesel: 5 wt ppm (converts to 0.5-2 ppmv SO2 in exhaust) (Ultra-low sulfur diesel: EU <10 wt ppm, USA <15 wt ppm) Catalyst: 1.5 kg Cu-CHA with 3 wt% Cu: 45 g Cu Potential total lifetime exposure: SO2/Cu = 44 2/1/2019 CLEERS 2018

Lifetime deactivation experiments SO2+O2+H2O exposure Regeneration 1-120 h @200-500 °C Total SO2/Cu = 42 Cu-CHA: Si/Al 14.6 Cu/Al 0.42 6 h @550 °C in SO2- free gas ICP: S/Cu ICP: S/Cu 2/1/2019 CLEERS 2018

ICP: sulfur uptake – S/Cu ratio Sulfur uptake faster at 300-400 °C With NO+NH3 S/Cu at 200 °C should increase Regenerated S/Cu similar for all temperatures 2/1/2019 CLEERS 2018

Lifetime deactivation of a Cu-CHA catalyst (solid lines: deactivation at 200 °C – dashed lines: S/Cu by ICP) S/Cu ratios increase in parallel to deactivation Deactivation occurs fast! After 1 % of the total lifetime SO2/Cu exposure, deactivation is above 70 % Deactivation level ≠ S/Cu ratio Regeneration can limit deactivation to 20 % 2/1/2019 CLEERS 2018

Conclusions Deactivation by Cu,S species – not ammonium sulfates Interactions of SO2 and SO3 depend on Cu oxidation state Deactivation occurs fast Regeneration is possible at 550 °C in SO2-free gas The use of Cu-CHA catalysts is contingent on: efficient regeneration and, use of ultra-low sulfur diesel 2/1/2019 CLEERS 2018

Thanks to collaborators! PhD student: Peter S. Hammershøi Technical University of Denmark (DTU): Professor Anker D. Jensen Umicore Denmark ApS: Principal Scientist Peter N.R. Vennestrøm Research Specialist Jesper S. Larsen Haldor Topsøe A/S: Research Scientist Hanne Falsig Innovation Fund Denmark 2/1/2019 NSC2018

Thank you for your attention