Warm Syngas Clean-up Process Development: Multi-Contaminant Removal using Sorbents and Ir-Ni Tar Reforming Catalyst

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1 Warm Syngas Clean-up Process Development: Multi-Contaminant Removal using Sorbents and Ir-Ni Tar Reforming Catalyst Robert A. Dagle, Kurt A. Spies, David L. King Pacific Northwest National Laboratory, Richland, WA

2 Syngas Purification for Chemical and Fuel Production Coal or Biomass Gasifier Raw Syngas Clean-up Process Clean Syngas WGS Synthesis, H 2 Production Sulfur & Metal Contaminants Application Requirements: Chemical Synthesis ppb Power Generation < 5 ppm Tars < 0.1 mg/nm 3 < 5 mg/nm 3

3 Raw Syngas Components Typical Coal Syngas Biomass (wood) Syngas WRI Coal Syngas H 2, % CO, % CO 2, % CH 4, % C 2+, % N 2, % H2S, ppmv 10-10, COS, ppmv 0-1,000 - < 2 NH3, ppmv 0-3, , Tars*, mg/nm ,000 ~500 Coal Syngas Impurities: Impurity HCl K Na AsH 3 PH 3 Hg Sb Se Pb Cd ppmv * Tar concentrations vary depending on gasifier type and operating conditions

4 Driving Force For Warm Gas Cleanup Common desulfurization strategies utilize physical adsorption solvents to remove sulfur and other contaminates Selexol -5 to 25 C Sulfur removal to 5 ppmv Rectisol -30 to -70 C Sulfur removal to < 100 ppbv Both processes are inefficient due to the temperature requirements to cool and re-heat the syngas

5 PNNL Warm Syngas Clean-up Process Desulfurization Unit Operations R2A Metal Removal Unit Operation Tar Removal Unit Operation Warm Dirty Syngas R1 Chlorine Removal Bulk S-Removal (Regenerable) R2B Bulk S-Removal (Regenerable) R3 Trace Metal Polishing R4 Tar & Light HC Reforming R5 LT-WGS Warm Clean Syngas Na 2 CO 3 ZnO ZnO & CuNi Ir-Ni/MgAl 2 O 4 CuZnAl 450 C 450 C 300 C 850 C 235 C

6 Sulfur Removal: Thermodynamic Calculation R3 R2 ZnO + H 2 S(s) = ZnS + H 2 O(g) Water content of the feed impacts the H 2 S threshold on ZnO

7 Sulfur Removal: Sorbent Capacity Temperature Dependence Operating the adsorbent at 450 C achieved the highest sulfur capacity ZnO + H 2 S(s) = ZnS + H 2 O(g) 3000 ppm H 2 S, 38.4 % CO, 38.4 % H 2, 3.2 % N 2, 20% H 2 O, 12,000 hr -1, G-72D ZnO Süd Chemie/ Clariant

8 Sulfur Removal: Regeneration Stability 5-10 ppmv sulfur slip after first cycle Stabilized capacity after 4 cycles 5 th & 4 th 3 rd 2 nd Fresh Sorbent Regeneration Conditions: 650 C in 5% O 2 /N ppm H 2 S, 38.4 % CO, 38.4 % H 2, 3.2 % N 2, 20% H 2 O, 12,000 hr -1, G-72D ZnO Süd Chemie/ Clariant

9 Sulfur Removal: Impact of Carbonyl Sulfide 200 O C Dry 450 O C Dry 450 O C Wet COS H 2 S 1000 ppm H 2 S, 80 % N 2, 20% H 2 O, 12,000 hr -1, G- 72E ZnO Süd Chemie/ Clariant COS hydrolysis is temperature dependent

10 Methane Conversion (%) Tar and Light Hydrocarbon Steam Reforming: Ir and Rh Metals Supported on MgAl 2 O 4 Ni-based catalysts are widely used for SR of biomass-derived HC s, however, suffer from coking and metal sintering PGM-based catalysts were thus investigated Methane steam reforming turnover rate at 850 o C for relevant transition metals follows the order: Pd > Pt > Ir > Rh, Ru > Ni SR of model biomass-derived syngas (w/o tar) over supported transition metals (850 o C) Ir Rh Pt Ru Pd However, Rh and Ir are found to have the best combination of activity and stability for reforming in the presence of simulated biomass-derived syngas Furthermore, highly dispersed 1nm Ir and 2 nm Rh metal clusters were found resistant to metal sintering when supported on MgAl 2 O 4 spinel support Journal of Catalysis 316 (2014) Time-On-Stream (hr) Ir and Rh metal clusters after 850 o C operation with simulated biomass-derived syngas

11 Methane conversion (%) Methane conversion (%) Tar and Light Hydrocarbon Steam Reforming: Ir-Ni/MgAl 2 O 4 Bimetallic Catalysts Promoting Ir with Ni enhances catalytic stability Both Ni sintering and coking is reduced with Ir addition IrNi catalysts also offer more stability than with Ir (or Rh) particles alone In agreement with theoretical calculations, small Irº clusters (~2 to 3 atoms) supported on large Niº particles ( 5 nm) present more resistance to coking than either small Irº clusters or Niº particles alone Ir o clusters Ir atoms Ni o clusters Steam reforming of model biomass-derived syngas (850 o C, 1 atm, 114,000 hr -1 ) Time-on-stream ( hours) 2.5%Ir15%Ni/MgAl 2O Accumulated moles of C fed /g catalyst 5%Ir/MgAl 2 O 4 2.5%Ir15%Ni/MgAl 2 O 4 5%Ir15%Ni/MgAl 2 O 4 1%Ir15%Ni/MgAl 2 O 4 0.5%Ir15%Ni/MgAl 2 O 4 15%Ni/MgAl 2 O 4 15%Ni/MgAl 2O 4 loading 3 Feed: 19.8% H 2, 9.9% CO, 10% CO 2, 5.7% CH 4, 09% C 2 H 4, Benzene=0.34%, Naphthalene=0.08%, H 2 O=52.8%, He=bal. Applied Catalysis B: Environmental, in review

12 Other Contaminant Removal: Ni Based Reforming Catalyst for NH 3 NH ppmv NH % CO 9.8 % CO % H 2 4.9% CH 4 50% H 2 O 10% He 1% N2 Industrial Engineering & Chemical Research 52 (2013)

13 Other Contaminant Removal: Na 2 CO 3 for HCl Ind. Eng. Chem. Res. 2013, 52,

14 Other Contaminant Removal: Supported Cu-Ni Adsorbent (300 C) Phosphine & Arsine Removal Nickel was added to the copper sorbent to suppress its water-gas-shift activity 33.6 % CO, 9.8 % CO 2, 26.6 % H 2, 30% H 2 O Chemistry of Materials 21 (2009)

15 Process Demonstration PNNL Developed mobile bench-scale gas cleanup process Water-quenched coal-derived syngas from Western Research Institute 2013 Tested on-site in Wyoming at WRI 2014 Tested at PNNL with WRI syngas

16 Process Demonstration: Results Very stable Compared to 2013 Addition of Improved Tar Reformer was large improvement Vast majority of contaminants removed from syngas (>99.9% sulfur and tar removed) PPM levels of sulfur found on front end spent WGS catalyst bed Water Gas Shift Catalyst Performance Considerable progress achieved from 2013 demonstration where significant deactivation occurred

17 Summary Warm gas clean-up is feasible and provides efficiency gains relative to ambient or subambient liquid phase capture of impurities Material for multi-contaminant removal process was demonstrated for 100 hours with ~1 SLPM Wyoming coal-derived syngas

18 Acknowledgments Co-Workers: Rong Xing, Vanessa M. Lebarbier, Libor Kovarik, Christopher J. Howard, Liyu Li, Matthew D. Flake, James E. Rainbolt Financial support by US DOE Office of Fossil Energy (NETL), State of Wyoming PNNL internal research Collaborators NETL Center for Clean Energy Engineering (University of Connecticut) Chinese Academy of Sciences (CAS) A portion of this work was carried out in the Environmental Molecular Sciences Laboratory (EMSL) at PNNL, a US DOE Office of Science user facility Questions: Robert.Dagle@pnnl.gov

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20 Slight WGS Deactivation in 2014 WRI Demonstration