Department of Chemical and Petroleum Engineering Sharif University of Technology, Iran

Transcription

1 Tayebeh Hamzehlouyan Department of Chemical and Petroleum Engineering Sharif University of Technology, Iran ETH-Conference on Combustion Generated Nanoparticles June 0, 018

2 1. Motivation. Experimental set up 3. SO oxidation on diesel oxidation catalyst 4. SO adsorption-desorption on a Pt/γ-Al O 3 catalyst 5. Sulfur impact on NO oxidation on the catalyst 6. Different deactivation impacts of SO, SO 3 and H SO 4 7. Conclusions

3 Diesel Oxidation Catalyst (DOC) Diesel Particulate Filter (DPF) Selective Catalytic Reduction (SCR) NO CO, HC, SOF, PAH O NO CO, H O SO,SO 3, SO H SO 4 DPF and SCR Catalysts The relative amounts of SO and SO 3 over a Pt/Al O 3 DOC? Different forms of sulfur can have different impacts on DOCs 3

4 Feed: 0 ppm SO, 1%CO, 10% O No SO Pt/Al O 3 1 st run with SO nd run with SO 3 rd run with SO PM emissions decreases due to oxidation of soluble organic fraction (SOF) At 450 C, an overall increase in total PM emission due to sulfate formation Gracia et al., J. Catal. 33 (005) 37 Sulfur can lead to catalyst deactivation The aftertreatment catalyst performance is adversely impacted by sulfur 4

5 Feed gas Water injection system SO 3 reactor 5

6 Prof. Bill Epling s lab, University of Houston, TX 6

7 Catalyst γ-al O 3 and Pt/γ-Al O 3 - supplied by JMI Reactor set up Gas inlet TC 1 TC 3 TC Quartz rods Quartz tube Catalyst Wrapping material Analyzer MKS MG-030 FTIR for gas-phase analysis ZnSe windows and MgF -coated mirrors Gas outlet to FTIR analyzer 7

8 SSSS + 11 OO SSSS 33 Reaction mechanism SO O 1, + * S 3,4 + * * * 5,6 O O * * SO + O SO * 7,8 SO O * 3 S 3 + * 3 Catalytic activity Equilibrium Feed: SO : 149 ppm SO 3 :106 ppm O :10% 8 Hamzehlouyan et al.; Applied Catalysis B: Environmental 15 (014) 108

9 SO concentration (ppm) 100 SO-S1 AlO3 SO loading in washcoat Pt/AlO3 γ-alo3.3 μmol/m 800 Pt/γ-AlO3.5 μmol/m 700 Temperature SO-S 60 SO-S3 48 ppm SO-S C 0 Temperature ( C) Empty reactor 95 C Time (s) Alumina effect is significant on the SO storage/release on Pt/γ-AlO3 Pt enhances the contribution of the more stable species 11

10 Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) Thermo Scientific Nicolet 6700 FT-IR Harrick Scientific praying mantis In situ characterization of surface intermediates under reaction dynamics 10

11 SO saturated-150c SO saturated-400c OH groups SO -S SO -S1 SO -S 160 cm -1 Kubelka-Munk Bisulfite HSO cm Surface sulfate 1060 cm -1 Surface sulfite cm Wavenumbers (cm -1 ) cm -1 SO -S Wavenumbers (cm -1 ) At 150 C, molecularly adsorbed SO 3 and sulfites form on Pt/Al O 3 At 400 C, surface sulfates are dominant 11

12 SO -S1: Molecular SO on Al sites SO -S: Surface sulfite SO -S3: Surface sulfate SO -S4: Bulk Al (SO 4 ) 3 Hamzehlouyan et al.; Applied Catalysis B: Environmental 181 (016) 587 1

13 Conversion 100% 90% 80% 70% 60% 50% 40% NO oxid without S NO oxid with 38 ppm SO NO oxid with 41 ppm SO3 SO conversion Mixed effect of SO and SO 3 30% 0% 10% 0% Temperature ( C) NO: 405 ppm, O : 5%, balanced with N SV = 5000 h -1, Total flow = 3.55 L/min NO oxidation is significantly inhibited in the presence of sulfur oxides At T 50 C, SO oxidation becomes important 13

14 Different impacts of SO, SO 3 and H SO 4 Conversion (%) 100% 80% 60% 40% 0% SO treated SO3 treated HSO4 treated 5% water in feed Adsorbed sulfur (μmol/m ) % Temperature ( C) Treatment SO SO 3 H SO 4 Procedure S inhibition effect on Pt/γ-Al O 3 : 50 ppm SO at 40 C overnight H SO 4 > SO 3 > SO Hamzehlouyan et al.; Topics in Catalysis 59 (016) 108 SO SO3 HSO4 77 ppm SO 3 at 40 C for h and in the feed 50 ppm H SO 4, % water, 10% O at 150 C for 4 h 14

15 Conclusions The kinetic model for SO oxidation can predict relative amounts of SO and SO 3 at different temperatures SO adsorption study showed significant effect of catalyst support in sulfur storage Multiple sulfur species on diesel oxidation catalyst were identified Sulfur uptake on Pt/γ-Al O 3 upon exposure to different forms of sulfur: H SO 4 > SO 3 > SO Deactivation impact of different sulfur species: H SO 4 > SO 3 > SO 15

16 University of Houston Dr. Bill Epling Dr. Chaitanya Sampara Cummins, Inc. Dr. Aleksey Yezerets Dr. Junhui Li Dr. Ashok Kumar MKS Instruments, Inc. Dr. Barbara Marshik Sylvie Bosch-Charpenay Bill Murphy Johnson Matthey Dr. Howard Hess

17 17 SSSS + 11 OO SSSS 33 rr SSSS = kk[ssss ] αα [OO ] ββ [SSSS 33 ] γγ T 74 C SO : ppm SO 3 : ppm O : 5-15%

18 Temp. T 300 C T > 300 C RDS Surface reaction and O adsorption Surface reaction Surface coverage Surface coverage at channel outlet θ SO θ SO Temperature(C) θ O θ vacant Feed: SO : 149 ppm SO 3 :106 ppm O :10% Hamzehlouyan et al.; Applied Catalysis B: Environmental 15 (014)

19 Two CO TPO runs were conducted back to back after SO saturation. No significant change was observed in the CO oxidation activity. The sulfur species are in a stable state on the catalyst. CO Conversion (%) CO: 513 ppm, O : 5%, balanced with N SV = h -1, Ramp rate = 10 C/min Fresh SO treated_run1 SO treated_run T C 158 C 160 C Temperature ( C) SO treatment: 50 ppm SO at 0 C for 3 h 19

20 NO oxidation activity of Pt/γ-Al O 3 was tested after SO saturation. During the NO oxidation cycles, no significant change occurs on the active sites involved in the reaction. Upon SO adsorption, stable sulfur species are formed on the catalyst. NO Conversion (%) NO: 30 ppm, O : 5%, balanced with N SV = h -1, Total flow = 5.8 L/min Fresh SO treated SO treated-4h SO co-fed Temperature ( C) SO treatment: 50 ppm SO at 0 C for 3 h SO co-feeding: 38 ppm SO in the feed 0

21 NO oxidation activity was substantially recovered after baking, due to the sulfur migration from PGM to support. Catalyst Baking : Heating at 400 C with 5% O to redistribute sulfur. Time effect not significant at 400 C. Freshly-deposited SO is associated with the active sites. NO Conversion (%) T 5% Fresh SO treated SO treated-4h SO co-fed 16 C 17 C 40 C Temperature ( C) Junhui Li et al., SAE (013) 1

22 Adsorption mechanism 1, SO + S1 SO S 1 3,4 SO + S SO S 5,6 SO + S3 SO S 3 x SO ( zt, ) θ (, ) SO Si zt 7,8 O S3+ S4 SO S4 + S3 S Pt/γ-Al O 3 Adsorption conditions: SO =48 ppm T=157 C

23 Surface coverages on Pt/γ-Al O 3 [SO ] = 50 ppm Adsorption T = 160 C SO : SO -S1: SO -S: SO -S3: Gas phase SO -Al Surface sulfite Surface sulfate SO -S4: Bulk Al (SO 4 ) 3 inlet Outlet Ultra low S fuel: 15 ppm [SO ] = 1 ppm Saturation time 16 h Hamzehlouyan et al.; Applied Catalysis B: Environmental 181 (016) 587 3