K int r é æ 2gW ö æ 2gW öù êexpç r * RT ÷ - expç rRT ÷ú ø è øû ë è Science in synthesis gas production Research I Technology I Catalysts Jens Sehested CORE and Surface Phenomena and Catalysis lecture Gent University, 9 May 2014, Gent, Belgium Confidential Presentation outline ¡ Synthesis gas production overview – The reactions – The technologies ¡ The heart in synthesis gas production: The steam reforming reaction over nickel – Sintering (stability of Ni particles) – Carbon formation and limits for whisker carbon formation – Reaction over nickel and other transition metals ¡ Can we cheat equilibrium in methanol synthesis? Confidential Haldor Topsøe A/S in brief ¡ Established in 1940 by Dr. Haldor Topsøe. 100% family owned ¡ ~2,800 employees in 11 countries across five continents. ¡ HQ in Lyngby, Denmark. Production in Denmark, USA and soon in China ¡ Three key operating business areas: – Chemicals – Environmental – Refinery Haldor Topsøe 1913-2013 ¡ Revenue ~ 700 million EUR (2013) Confidential Construction at the Pearl GTL project, Qatar, 2010 What is synthesis gas? ¡ Synthesis gas is a mixture of CO/CO2/H2 that is used in a number of syntheses of wide range of chemicals ¡ Synthesis gas can be made from – Steam reforming – Gasification – Partial oxidation Confidential Typical methanol process ~ 2500 MTPD Oxygen Steam Sulphur removal Steam Prereformer Methanol reactor Secondary reformer Hydrogenator Steam Makeup comp. Natural gas Steam reformer Condensate Light ends to fuel Product methanol Water Raw methanol Raw methanol storage Confidential Pre-reformer; Primary reformer; Secondary reformer; ATR O2 / Air Process Gas CH4 + H2O à 3H2 + CO; CH4 + 3/2O2 à CO2 + H2O; CO2 + H2 àCO + H2 Mainly Ni based catalysis; T-range [390 – 1050oC] Confidential Steam Reforming and shift reactions CH4 + H2O CnHm + n H2O CO + H2O CO + 3H2 (-DH0298 = -206 kJ/mol) n CO + (n+m/2) H2 CO2 + H2 (-DH0298 < 0) (-DH0298 = 41 kJ/mol) ¡ Steam refoming is strongly endothermic – i.e. favourable equilibrium at high T, low p ¡ Shift is weakly exothermic – i.e. favourable equilibrium at low T Confidential Steam reforming and methane conversion CH4 + H2O CO + 3H2 (-DH0298 = -206 kJ/mol) Methane conversion, % 100 1 bar abs 80 20 bar abs 60 40 S/C = 5.0 S/C = 2.5 S/C = 1.0 20 0 400 500 600 700 800 900 400 S/C = 5.0 S/C = 2.5 S/C = 1.0 500 600 Reforming equilibrium temperature, °C Confidential 700 800 900 1000 Tubular steam reforming Heat Feed ~500°C Heat Heat Catalyst Heat Heat ~900°C Confidential Oryx GTL plant – Qatar 34,000 BPD Prereformer Natural gas Refor ming Synthesis gas FT Confidential Autothermal reformer HC Crac- Transport king fuel Adiabatic pre-reforming Temperatures typically 400-600°C Feed flexibility – conversion of HHC Reducing size of down stream reformers Removes traces of sulphur 470 O2 / Air 460 Natural Gas and Steam T e m p e ra tu re , d e g C ¡ ¡ ¡ ¡ Process Gas 450 440 430 420 0 0,2 0,4 0,6 Relative axial distance Synthesis Gas Confidential 0,8 1 Air or Oxygen Autothermal reforming Natural gas, or reformed gas + steam burner Combustion zone CH4 + 1½O2 CO + 2H2O Thermal and catalytic zones CH4 + H2O CO + 3H2 CO + H2O CO2 + H2 Synthesis gas Confidential Economy of Scale for Syngas The choice of technology depends on scale of operation H2O/CH4 Log costs Air H2O/CH4 O2-plant O2 Syngas Air H2O/CH4 Tubular Reformer O2 Log capacity Syngas Confidential The heart in synthesis gas generation is steam reforming CnH2n+2 + nH2O CH4 + H2O CO + H2O O2 / Air Process Gas Ni Ni Ni nCO + (2n + 1) H2 CO + 3H2 CO2 + H2 Ni(111), 0.20nm Ni(200), 0.18nm Confidential From nano to mega Active phase Pore structure 0,0000000001m = 1Å 0,000000001m = 1nm Catalyst from 0,001m = 1mm Confidential Reactor 1m Presentation outline ¡ Synthesis gas production overview – The reactions – The technologies ¡ The heart in synthesis gas production: The steam reforming reaction over nickel – Sintering (stability of Ni particles) – Carbon formation and limits for whisker carbon formation – Reaction over nickel and other transition metals ¡ Can we cheat equilibrium in methanol synthesis? Confidential Environmental TEM (ETEM) S. Helveg Philips CM300-ST FEG FEI Titan 80-300 Cs-corr FEG FEG x Gas handling gas path: x = 5.4mm Sample QMS Gas handling Sample Aberration corrector Detectors - Tietz F114 CCD - GIF2000 Detectors -US1000 & Tridiem 863 4mm § 1-20mbar, 10-50Nml/min, 600-900oC Adv. Catal. 50, 77 (2006) Confidential Sintering of metal catalysts Nickel steam reforming catalysts 1 1:1 2 =30 H2O:HH22=O:H 1:1, bar g 0.9 0.8 Relative Ni area 0.7 0.6 650 °C 0.5 0.4 0.3 800 °C 0.2 0.1 0 0 100 200 300 400 500 Time (hours) 600 700 800 Ni/MgAl Confidential 2O4 Sintering in steam reforming Prereforming Tubular reforming 400-600°C 500-900°C High steam partial pressures 2 mbar H2, 500°C, red. Ni/MgAl2O4 2 mbar H2, 750°C, 5h Autothermal reforming 2 mbar H2:H2O=1:1 750°C, 5h Confidential T. Hansen PhD thesis (2006) 900-1200°C Particle Migration and Coalescence (PMC) H2, 600°C Ni/MgAl2O4 Confidential Ostwald Ripening (OR) H2, 700°C – Atom migration – Vapour migration Ni/MgAl2O4 Confidential Predicting sintering: 30 min 5 nm ¡ ¡ ¡ Ni/MgAl2O4 reforming catalyst 750oC, H2:H2O = 1:1 @ 3.6mbar TEM: 300keV, 740 e-/Å2s ¡ Ni/MgAl2O4 reforming catalyst ¡ 750oC, H2:H2O = 1:1 @ 3.6mbar ¡ TEM: 300keV, 740 e-/Å2s Initial Ex situ, 30 min Model, 30 min K int (750°C ) = 5 ×10 -3 nm 2 s -1 Challa et al. JACS 133, 20672 (2011) Confidential Bridging the gap: Catalyst and ETEM data 5 nm 14 12 dNi/dNi,0 10 1/ 3 d Ni æç K 3D OH-dim er t æç PH O ö÷ ö÷ = +1 3 0.5 ÷ ç ÷ P d Ni , 0 çè d Ni , 0 è H ø ø 8 6 4 2 2 174-700 h 28.2 bar H2O 2.8-12 bar H2 700 h, H2O:H2=10, 31 bar 174.3 h, H 2O:H 2=10, 31 bar 2 0 450 700 h, H2O:H2=2.5, 40 bar 500 550 600 650 700 750 800 850 Temperature (°C) K int (750°C ) = (0.9 - 17 ) ×10 nm s -3 2 -1 K int (750°C ) = 1.2 ×10 -3 nm 2 s -1 Challa et al. JACS 133, 20672 (2011) Confidential Sehested et al. J. Catal. 223, 432 (2004) Sehested et al. Unpublished Is it possible to reduce sintering? Promotor ¡ Alloy with another metal: Ni carrier Ni Ni carrier Huge Ni particles > 200 nm Ni bimetallic particles 5 – 50 nm Ni/Al2O3 Ni/Al2O3 + 11mol% precious metal After aging at 850°C, 30 bar g and H2O/H2 = 6 during 10 days Confidential F.Morales-Cano et al. (2012) Exposure to Industrial Conditions Invention ¡ Promoted catalysts tested in an ATR for 6 months p-Ni/Al2O3 Ni/Al2O3 ¡ Ni volatilization and sintering are suppressed in the presence of precious metal promotor Catalyst after 6 months ATR operation Rings retrieved after 6 months Ni/Al2O3 F.Morales-Cano et al. (2012) Ni/Al O + precious metal 2 3 Confidential Pressure drop over an ATR ¡ Interactions behind the pressure shell between: O2 – Flame … CH4 – Gas phase … CO2 – Refractory … CO H2 – Tiles … H2O Al(OH)3 – Catalyst … – Rubies … – Pressure drop … – … Al2O3 Confidential ΔP Pressure drop in industrial ATR - low H2O/CH4 ratio dP comparison in various ATR runs 160 140 120 Relavtive dP 100 80 60 40 20 dP optimized cat. bed 0 0 2000 4000 6000 8000 10000 Runtime (h) Confidential 12000 14000 16000 18000 20000 Presentation outline ¡ Synthesis gas production overview – The reactions – The technologies ¡ The heart in synthesis gas production: The steam reforming reaction over nickel – Sintering (stability of Ni particles) – Carbon formation and limits for whisker carbon formation – Reaction over nickel and other transition metals ¡ Can we cheat equilibrium in methanol synthesis? Confidential How can we improve the steam ref. section in GTL? Steam Gas to liquid (GTL) – heat exchange reforming Natural gas Prereforming Oxygen Tail Gas from FT ATR HTER-s • Reduces size and duty of WHB • Reduces size and duty of fired heater • Lower ASU cost Confidential Synthesis gas to WHB Effect of whisker carbon formation Decreasing H2O/CH4 Confidential How does a carbon fiber grow? Ni C fiber 4 2 1 C fiber Ni 2 ? Ni Graphite whisker 20nm Baker et al, J. Catal. 26, 51 (1972), ibid. 30, 86 (1973) Confidential Imaging of carbon formation • CH4:H2=1:1, 2.1mbar, 536°C • Image size: 22x22nm2 • 10 frames/s (display rate x2.5) • Growth rate ~1nm/s Nature 427 (2004) 426 Confidential Graphene Formation at Ni Steps 5nm 0s 0.2s 0.8s 1.0s 0.4s 0.6s 1.2s 1.4s § Spontaneous formation of mono-atomic Ni step sites § Transport of C and Ni atoms Confidential Surface dynamics CH4 C H2 Ni III II I Ni § CH4:H2=1:1, 2.1 mbar, 525°C § Image size: 21.3x21.3nm2, 10 frames/s (display rate x2.5) Nature 427 (2004) 426; Phys. Rev. B 73, 115419 (2006) Confidential Growth mechanism § Ni transport proceeds along the Ni surface § C transport along the surface or sub-surface dominates bulk transport and could be rate-limiting for growth DFT - energy barriers for C transport CH4 C H2 III I: Surface transport of C II I Ni Ni 1.42eV II: Subsurface transport of C 1.55eV III: Bulk C transport 2.33eV Experimental Growth 1.3-1.5eV Barriers Nature 427 (2004) 426 Phys. Rev. B 73, 115419 (2006) Confidential Effect of nanoparticle size § Energy gained by forming carbon layers § Stablizing interactions between the carbon layers § Bending the layers offsets the stabilization Pt NPs ca. 4nm Pt NPs ca. 2nm Pt/MgO exposed to C2H6:H2:He=12:15:33 mL/min 600 oC Peng, Somodi, Helveg, Kisielowski, Specht, Bell, J. Catal. 2012, 286, 22. Confidential Effect of particle size and limits for carbon formation at Ni Equilibrated gas Unequilibrated gas CO/CO2/CH4/H2/H2O 104 Carbon Relative weight (%) 15%Ni/MgAl2O4 103 dNi = 102 nm 102 101 No carbon 0.92%Ni/MgAl2O4 100 dNi = 7 nm 99 575 625 675 725 775 825 875 Temperature (K) Carbon formation in a mixture of C4H10/H2/H2O/He Sehested, Christensen, Jacobsen, Helveg, Rostrup-Nielsen, ACS Meeting (2005) p.PETR-137 Bengaard et al. J. Catal. 209, 354 (2002) Confidential Presentation outline ¡ Synthesis gas production overview – The reactions – The technologies ¡ The heart in synthesis gas production: The steam reforming reaction over nickel – Sintering (stability of Ni particles) – Carbon formation and limits for whisker carbon formation – Reaction over nickel and other transition metals ¡ Can we cheat the equilibrium in methanol synthesis? Confidential Steam reforming at low H2O/CH4 ratio Whisker carbon growth Steam Natural gas Oxygen Tail Gas from FT Prereforming Synthesis gas to WHB ATR HTER-s Rhodium particle Confidential 0,9 0,8 Frequency 0,7 Experimental 0,6 0,5 0,4 0,3 0,2 0,1 0 10 30 50 70 90 110 130 150 More Diameter (Å) ¡ Transmission electron microscopy ¡ In situ investigations ¡ Zirconia support ¡ 18 samples (Rh, Ru, Ni, Ir, Pt, Pd) Reactivity per site ¡ Plug flow reactor ¡ 500°C Confidential Turn over frequency (TOF) ¡ Combination of in situ TEM data and activity measurements - Reaction at undercoordinated sites Ligthart,Santen, Hensen, J. Cat. 280 206 (2011) Reaction order in agreement with: Rostrup-Nielsen, J. Catal. 31 173 (1973) Rh Rh, Ru > Ni, Pd, Pt > Re > Co Kikuchi et al., Bull. Jpn. Pet. Inst. 16 95 (1974) Rh, Ru > Ni > Ir >Pd, Pt >> Co,Fe Terrace site J. Catal. 144 38 (1993) site Rostrup-Nielsen and Hansen, Defect Rh, Ru > Ir > Ni > Pt, Pd Qin et al., Catal. Today 21 551 (1994) Ni Ru > Rh > Ir > Pt > Pd Pt Ir Reaction order observed by Wei and Iglesia: Pt > Ir > Rh > Ru, (Ni) Ru, Rh ¡ TOF: Ru, Rh > Ni, Pt, Ir, Pd Wei and Iglesia, J. Phys. Chem. B 108 (13) 4094 (2004) Confidential Jones et al, J. Catal. 259, 147 (2008) Micro-kinetic modelling CH4(g)+2* = CH3*+H* ¡ 9 step model – CH4 dissociative adsorption and CO formation are considered to rate determining steps – Remaining reaction are assumed to be quasi-equilibrated CH3*+* = CH2*+H* CH2*+* = CH*+H* CH*+* = C*+H* H2O(g)+2* = OH*+H* ¡ 8 intermediates OH*+* = O*+H* ¡ 2 reaction barriers C*+O* = CO*+* ¡ Shift reaction equilibrated H* = 0.5H2(g)+* CO* = CO(g)+* CO(g)+H2O(g) = CO2(g)+H2(g) Jones et al, J. Catal. 259, 147 (2008) Confidential Activity of the methane steam reforming ¡ Reaction barriers and binding energies scaled to ΔEO, ΔEC using linear scaling and BEP F. Abild-Pedersen et al., Phys. Rev. Lett. 2007. Model: Ru > Rh ~ Ni > Ir >>Pt ~ Pd Exp: Ru ~ Rh > Ni ~ Ir ~ Pt ~ Pd 500°C, 1 bar, 10% conversion Jones et al, J. Catal. 259, 147 (2008) Confidential Presentation outline ¡ Synthesis gas production overview – The reactions – The technologies ¡ The heart in synthesis gas production: The steam reforming reaction over nickel – Sintering (stability of Ni particles) – Carbon formation and limits for whisker carbon formation – Reaction over nickel and other transition metals ¡ Can we cheat equilibrium in methanol synthesis? Confidential Typical methanol process Oxygen Steam Sulphur removal Steam Prereformer Methanol reactor Secondary reformer Hydrogenator Steam Makeup comp. Natural gas Steam reformer Condensate Light ends to fuel Product methanol Water Raw methanol Raw methanol storage Confidential Methanol reactor Synthesis gas Syngas 4-5 cm Boiling water Steam Methanol catalyst CO + 2H2 → CH3OH CO2 + 3H2 → CH3OH + H2O 7m Water Cu/Zn/Alumina Pellets Temperature: ~250°C Product May 9, 2014 Confidential Typical methanol loop What if we could… Confidential … simplify the methanol synthesis to this Confidential Can we cheat the methanol equilibrium? ¡ Presented at NGCS in Oslo 1990 ¡ Various reactor layouts and sizes tested, but economic assessment was unfavourable due to low STY Confidential The CONRAD concept Synthesis gas ¡ CONdensing RADial flow converter ¡ Reactor comprising two-zone tubes – High T zone in center of tube – Low T zone along tube wall Internals ¡ Internals for gas-liquid separation ¡ Balance between heat transfer and mass transfer Methanol Confidential The BioDME project 3G vehicle development Fuel injection development Vehicle production Fuel properties Syngas generation and cleaning Vehicle field test DME Distribution & filling DME production Black liquor LPG subst. Biomass www.biodme.eu Confidential Methanol Synthesis MeOH reactor Conrad Synthesis Gas Steam Steam MeOH cat. Raw MeOH Confidential Observed syngas conversions Confidential Measured Space time yield in BWR Step-out Space Time Yields in BWR 4 3.5 S T Y k g /k g /h 3 2.5 2 1.5 1 0.5 0 8-11 2011 28-12 2011 16-2 2012 6-4 2012 26-5 2012 15-7 2012 Date Confidential 3-9 2012 23-10 2012 12-12 2012 Measured CONRAD performances CONRAD STY relative to target 400 CONRAD A 350 CONRAD C 300 S T Y In d e x CONRAD D 250 200 150 100 50 0 8-11 2011 28-12 2011 16-2 2012 6-4 2012 26-5 2012 15-7 2012 Date Confidential 3-9 2012 23-10 2012 12-12 2012 Economic Assessment Total installed costs for various MeOH production processes Reforming Synthesis Total installed cost Synthesis SMR+ATR1) Loop 100 100 ATR Loop 83 91 ATR CONRAD 77 66 ATR CONRAD1) 83 88 1) Assuming performance as demonstrated The CONRAD concept works, but more work is needed! Confidential Summary ¡ Nickel sintering: – We understand the underlying mechanisms for sintering of nickel particles during steam reforming well – This knowledge may be used in new catalysts ¡ Carbon formation: – Mechanism involving surface diffusion of C and Ni atoms – Surface defects act as nucleation centers for CNF growth – Carbon limit and rate depends on both metal and particle size ¡ Steam reforming activity: – Reaction proceeds at surface defects – Rate highest for Ru and Rh in agreement with microkinetic model ¡ The CONRAD concept works, but needs further development Confidential Acknowledgements ¡ Haldor Topsøe A/S: S. Helveg P. Lenvig Hansen A. M. Molenbroek B. S. Clausen J. R. Rostrup-Nielsen F.M. Morales J.G. Jakobsen M.S. Skjøth-Rasmussen E.L. Sørensen M. Thorhauge ¡ Danish Technical University: T. W. Hansen J.K. Nørskov (Stanford University) F. Abild-Pedersen (Stanford University) I. Chorkendorff ¡ University of New Mexico: A. K. Datye A. T. Delariva S.R. Challa Confidential
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