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Science in synthesis gas production

Jens SehestedCORE and Surface Phenomena and Catalysis lecture

Gent University, 9 May 2014, Gent, Belgium

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¡ Synthesis gas production overview– The reactions

– The technologies

¡ The heart in synthesis gas production: The steamreforming 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?

Presentation outline


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 inChina

¡ Three key operating businessareas:– Chemicals– Environmental– Refinery

¡ Revenue ~ 700 million EUR (2013)Haldor Topsøe 1913-2013


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

Construction at the Pearl GTL project, Qatar, 2010


Steam

Pre-reformer

Secondaryreformer

Steam

Steam

Oxygen

Makeupcomp.

Light ends to fuel

Methanolreactor

Water

Rawmethanol

Raw methanol storage

Condensate

Steam reformer

Sulphur removal

Hydrogenator

Naturalgas

Productmethanol

Typical methanol process ~ 2500 MTPD


Pre-reformer; Primary reformer; Secondary reformer;ATR

CH4 + H2Oà 3H2 + CO; CH4 + 3/2O2 à CO2 + H2O; CO2 + H2 àCO + H2Mainly Ni based catalysis; T-range [390 – 1050oC]

Process Gas

O2 / Air


Steam Reforming and shift reactions

CH4 + H2O CO + 3H2 (-DH0298 = -206 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

CnHm + n H2O n CO + (n+m/2) H2 (-DH0298 < 0)

CO + H2O CO2 + H2 (-DH0298 = 41 kJ/mol)


Steam reforming and methane conversion

400 500 600 700 800 900 400 500 600 700 800 900

S/C = 5.0S/C = 2.5S/C = 1.0

S/C = 5.0S/C = 2.5S/C = 1.0

Reforming equilibrium temperature, °C

0

20

40

60

80

100Methane conversion, %

1 bar abs 20 bar abs

1000

CH4 + H2O CO + 3H2 (-DH0298 = -206 kJ/mol)


Tubular steam reforming

Heat

Heat

Heat

Heat

Heat

Feed

Catalyst

~500°C

~900°C


Oryx GTL plant – Qatar 34,000 BPD

Prereformer Autothermalreformer

Naturalgas

Reforming

Synthesisgas

FT HC Crac-king

Transportfuel


Adiabatic pre-reforming¡ Temperatures typically 400-600°C¡ Feed flexibility – conversion of HHC¡ Reducing size of down stream reformers¡ Removes traces of sulphur

420

430

440

450

460

470

0 0,2 0,4 0,6 0,8 1

Relative axial distance

Tem

pera

ture

,deg

C

Process Gas

O2 / Air

Natural Gasand Steam

SynthesisGas


Combustion zoneCH4 + 1½O2 CO + 2H2O

Thermal and catalytic zonesCH4 + H2O CO + 3H2CO + H2O CO2 + H2

Autothermal reformingAir or Oxygen

Natural gas,or reformed gas+ steam

burner

Synthesis gas


Economy of Scale for SyngasThe choice of technology depends onscale of operation

Log capacity

Log costs TubularReformer

O2-plant

H2O/CH4

Air

H2O/CH4O2

Syngas

Air

H2O/CH4O2

Syngas

H2O/CH4

Air

H2O/CH4O2

Syngas

Air

H2O/CH4O2

Syngas


The heart in synthesis gas generation issteam reforming

Ni(111),0.20nm

Ni(200),0.18nm

CnH2n+2 + nH2O nCO + (2n + 1) H2

CH4 + H2O CO + 3H2

CO + H2O CO2 + H2

Ni

Ni

Ni

ProcessGas

O2 /Air


From nano to mega

Reactor1m

Catalyst from0,001m = 1mm

Pore structure0,000000001m = 1nm

Active phase0,0000000001m = 1Å


Environmental TEM (ETEM)

Philips CM300-ST FEG

gas path:x = 5.4mm

x

FEG

Sample

Detectors- Tietz F114 CCD- GIF2000

Gas handling

QMS

FEG

Sample

Gas handling

Aberrationcorrector

Detectors-US1000 & Tridiem 863

§ 1-20mbar, 10-50Nml/min, 600-900oC

FEI Titan 80-300 Cs-corr

Adv. Catal. 50, 77 (2006)

4mm

S. Helveg


Sintering of metal catalysts

Ni/MgAl2O4

H2O:H2 = 1:1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 100 200 300 400 500 600 700 800

Time (hours)

Rel

ativ

eN

iare

a

800 °C

650 °C

Nickel steam reforming catalysts

H2O:H2 = 1:1, 30 bar g


Sintering in steam reformingTubular reformingPrereforming Autothermal reforming

400-600°C 500-900°C 900-1200°CHigh steam partial pressures

2 mbar H2,750°C, 5h

2 mbar H2:H2O=1:1750°C, 5h

2 mbar H2,500°C, red.

T. Hansen PhD thesis (2006)Ni/MgAl2O4


Particle Migration and Coalescence (PMC)

H2, 600°C

Ni/MgAl2O4


Ostwald Ripening (OR)

Ni/MgAl2O4

H2, 700°C– Atom migration

– Vapour migration


Predicting sintering: 30 min¡ Ni/MgAl2O4 reforming catalyst¡ 750oC, H2:H2O = 1:1 @ 3.6mbar¡ TEM: 300keV, 740 e-/Å2s

Challa et al. JACS 133, 20672 (2011)

InitialEx situ, 30 minModel, 30 min

¡ Ni/MgAl2O4 reforming catalyst¡ 750oC, H2:H2O = 1:1 @ 3.6mbar¡ TEM: 300keV, 740 e-/Å2s

123int 105)750( --×=° snmCK

5 nm


Bridging the gap: Catalyst and ETEM data

( ) 123int 10179.0)750( --×-=° snmCK

3/1

5.0H

OH3

0,Ni

erdimOH3

0,Ni

Ni 1PP

dtDK

dd

2

2

÷÷ø

öççè

æ+÷

÷ø

öççè

æ= -

123int 102.1)750( --×=° snmCK

0

2

4

6

8

10

12

14

450 500 550 600 650 700 750 800 850

Temperature (°C)

d Ni/d

Ni,0

174.3 h, H2O:H2=10, 31 bar

700 h, H2O:H2=10, 31 bar

700 h, H2O:H2=2.5, 40bar

174-700 h28.2 bar H2O2.8-12 bar H2

Challa et al. JACS 133, 20672 (2011)

5 nm

Sehested et al. UnpublishedSehested et al. J. Catal. 223, 432 (2004)

ConfidentialConfidentialAfter aging at 850°C, 30 bar g and H2O/H2 = 6 during 10 days

Huge Ni particles > 200 nm

Ni bimetallicparticles 5 – 50nm

Ni/Al2O3 Ni/Al2O3 + 11mol% precious metal

Is it possible to reduce sintering?¡ Alloy with another metal:

F.Morales-Cano et al. (2012)

NiNi Ni

Promotor

carrier carrier


Rings retrieved after 6months

Exposure to Industrial Conditions¡ Promoted catalysts tested in an ATR for 6

months

¡ Ni volatilization and sintering are suppressed inthe presence of precious metal promotor

Ni/Al2O3

p-Ni/Al2O3

Catalyst after 6 months ATR operation

Ni/Al2O3 Ni/Al2O3 + preciousmetalF.Morales-Cano et al. (2012)

Invention


Pressure drop over an ATR¡ Interactions behind the

pressure shell between:– Flame …

– Gas phase …

– Refractory …

– Tiles …

– Catalyst …

– Rubies …

– Pressure drop …

– …

COH2

H2O

CO2

CH4

O2

Al2O3

ΔPAl(OH)3


Pressure drop in industrial ATR - low H2O/CH4 ratio

0

20

40

60

80

100

120

140

160

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Rel

avtiv

edP

Runtime (h)

dP comparison in various ATR runs

dP optimized cat. bed0

20

40

60

80

100

120

140

160

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Rel

avtiv

edP

Runtime (h)

dP comparison in various ATR runs


How can we improve the steam ref. section in GTL?Gas to liquid (GTL) – heat exchange reformingSteam

Natural gas

ATRHTER-s

Oxygen

Synthesis gas toWHB

Prereforming

Tail Gas from FT

• Reduces size and duty of WHB• Reduces size and duty of fired heater• Lower ASU cost


Effect of whisker carbon formation

Decreasing H2O/CH4


Graphitewhisker

4 2

Ni

20nm

Ni

C fiber

Ni

C fiber 1

2

Baker et al, J. Catal. 26, 51 (1972),ibid. 30, 86 (1973)

?

How does a carbon fiber grow?


• 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

Imaging of carbon formation


5nm

0s 0.2s 0.4s 0.6s

0.8s 1.0s 1.2s 1.4s

Graphene Formation at Ni Steps

§ Spontaneous formation of mono-atomic Ni step sites§ Transport of C and Ni atoms


§ 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)

Surface dynamics

C H2

CH4

NiIIIIII

Ni


§ Ni transport proceeds along the Ni surface

§ C transport along the surface or sub-surface dominates bulk transportand could be rate-limiting for growth

Phys. Rev. B 73, 115419 (2006)

Growth mechanism

C H2

CH4

Ni

IIIIII

Ni

I: Surface transport ofC 1.42eV

II: Subsurfacetransport of C 1.55eV

III: Bulk C transport 2.33eV

Experimental GrowthBarriers 1.3-1.5eV

DFT - energy barriers for C transport

Nature 427 (2004) 426


Effect of nanoparticle size§ Energy gained by forming carbon layers

§ Stablizing interactions between the carbon layers

§ Bending the layers offsets the stabilization

Peng, Somodi, Helveg, Kisielowski,Specht, Bell, J. Catal. 2012, 286, 22.

Pt/MgO exposed to C2H6:H2:He=12:15:33 mL/min 600 oC

Pt NPsca. 2nm

Pt NPsca. 4nm


Effect of particle size and limits for carbonformation at Ni

Equilibrated gasCO/CO2/CH4/H2/H2O

Bengaard et al. J. Catal. 209, 354 (2002)

Carbon formation in a mixture ofC4H10/H2/H2O/He

99

100

101

102

103

104

575 625 675 725 775 825 875

Temperature (K)

Rel

ativ

ew

eigh

t(%

)

15%Ni/MgAl2O4

0.92%Ni/MgAl2O4

dNi = 102 nm

dNi = 7 nm99

100

101

102

103

104

575 625 675 725 775 825 875

Temperature (K)

Rel

ativ

ew

eigh

t(%

)

15%Ni/MgAl2O4

0.92%Ni/MgAl2O4

dNi = 102 nm

dNi = 7 nm

Sehested, Christensen, Jacobsen, Helveg,Rostrup-Nielsen, ACS Meeting (2005) p.PETR-137

Unequilibrated gas

Carbon

No carbon







¡ Can we cheat the equilibrium in methanol synthesis?



Steam reforming at low H2O/CH4 ratio

Whisker carbon growth

Rhodium particle

SteamNatural gas

ATRHTER-s

Oxygen Synthesisgas toWHB

Prereforming

Tail Gas from FT


Experimental

¡ Plug flow reactor

¡ 500°C

¡ Zirconia support

¡ 18 samples (Rh, Ru,Ni, Ir, Pt, Pd)

¡ Transmission electron microscopy

¡ In situ investigations

Reactivity per site

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

10 30 50 70 90 110 130 150 More

Diameter (Å)

Freq

uenc

y


¡ Combination of in situ TEM data and activitymeasurements - Reaction at undercoordinated sites

¡ TOF: Ru, Rh > Ni, Pt, Ir, Pd

Turn over frequency (TOF)

Reaction order observed byWei and Iglesia:

Pt > Ir > Rh > Ru, (Ni)Wei and Iglesia, J. Phys. Chem. B 108 (13) 4094 (2004)

Jones et al, J. Catal. 259, 147 (2008)

PtIrRu, Rh

Ni

Reaction order in agreement with:

Rh, Ru > Ni, Pd, Pt > Re > Co

Rh, Ru > Ni > Ir >Pd, Pt >> Co,Fe

Rh, Ru > Ir > Ni > Pt, Pd

Ru > Rh > Ir > Pt > Pd

Rostrup-Nielsen, J. Catal. 31 173 (1973)

Kikuchi et al., Bull. Jpn. Pet. Inst. 16 95 (1974)

Rostrup-Nielsen and Hansen, J. Catal. 144 38 (1993)

Qin et al., Catal. Today 21 551 (1994)

Terrace site Defect site

Ligthart,Santen, Hensen,J. Cat. 280 206 (2011)

Rh


Micro-kinetic modelling¡ 9 step model

– CH4 dissociative adsorption andCO formation are considered torate determining steps

– Remaining reaction are assumedto be quasi-equilibrated

¡ 8 intermediates

¡ 2 reaction barriers

¡ Shift reaction equilibrated

CH4(g)+2* = CH3*+H*CH3*+* = CH2*+H*CH2*+* = CH*+H*CH*+* = C*+H*

H2O(g)+2* = OH*+H*OH*+* = O*+H*C*+O* = CO*+*H* = 0.5H2(g)+*CO* = CO(g)+*

CO(g)+H2O(g) = CO2(g)+H2(g)Jones et al, J. Catal. 259, 147 (2008)


Activity of the methane steam reforming¡ Reaction barriers and

binding energiesscaled to ΔEO, ΔEC

using linear scalingand BEP

Model: Ru > Rh ~ Ni > Ir >>Pt ~ Pd

Exp: Ru ~ Rh > Ni ~ Ir ~ Pt ~ PdJones et al, J. Catal. 259, 147 (2008)

500°C, 1 bar, 10% conversion

F. Abild-Pedersen et al., Phys. Rev. Lett.2007.


Steam

Pre-reformer

Secondaryreformer

Steam

Steam

Oxygen

Makeupcomp.

Light ends to fuel

Methanolreactor

Water

Rawmethanol

Raw methanol storage

Condensate

Steam reformer

Sulphur removal

Hydrogenator

Naturalgas

Productmethanol

Typical methanol process


7 m

4-5 cm

Boiling water

Methanol reactor

May 9, 2014

Methanol catalystCO + 2H2 → CH3OHCO2 + 3H2 → CH3OH + H2O

Cu/Zn/Alumina

Pellets

Temperature: ~250°C

Product

Syngas

Water

Steam

Synthesis gas


Typical methanol loop

What if we could…


… simplify the methanol synthesis to this


Can we cheat the methanol equilibrium?

¡ Presented at NGCS in Oslo 1990

¡ Various reactor layouts and sizes tested, but economicassessment was unfavourable due to low STY


The CONRAD concept¡ CONdensing RADial flow converter

¡ Reactor comprising two-zone tubes

– High T zone in center of tube

– Low T zone along tube wall

¡ Internals for gas-liquid separation

¡ Balance between heat transfer andmass transfer

Methanol

Synthesis gas

Internals


The BioDME project

Biomass

Blackliquor

Syngasgeneration

andcleaning

DMEproduction

DMEDistribution

& filling

Vehiclefield test

LPG subst.

Fuelinjection

development

Vehicleproduction

3G vehicledevelopment

Fuelproperties

www.biodme.eu


Methanol Synthesis

MeOH reactor

Steam

Raw MeOH

Synthesis GasSteam

Conrad

MeOH cat.


Observed syngas conversions


Step-out Space Time Yields in BWRMeasured Space time yield in BWR

0

0.5

1

1.5

2

2.5

3

3.5

4

8-11 2011 28-12 2011 16-2 2012 6-4 2012 26-5 2012 15-7 2012 3-9 2012 23-10 2012 12-12 2012

Date

STY

kg/k

g/h


CONRAD STY relative to targetMeasured CONRAD performances

0

50

100

150

200

250

300

350

400

8-11 2011 28-12 2011 16-2 2012 6-4 2012 26-5 2012 15-7 2012 3-9 2012 23-10 2012 12-12 2012

Date

STY

Inde

x

CONRAD A

CONRAD C

CONRAD D


Economic Assessment

1) Assuming performance as demonstrated

The CONRAD concept works, but more work is needed!

Total installed costs for various MeOH productionprocessesReforming Synthesis Total

installedcost

Synthesis

SMR+ATR1) Loop 100 100

ATR Loop 83 91

ATR CONRAD 77 66

ATR CONRAD1) 83 88


Summary¡ Nickel sintering:

– We understand the underlying mechanisms for sintering of nickel particlesduring 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 inagreement with microkinetic model

¡ The CONRAD concept works, but needs further development


Acknowledgements

S. HelvegP. Lenvig HansenA. M. MolenbroekB. S. ClausenJ. R. Rostrup-NielsenF.M. MoralesJ.G. JakobsenM.S. Skjøth-RasmussenE.L. SørensenM. Thorhauge

T. W. HansenJ.K. Nørskov (Stanford University)F. Abild-Pedersen (Stanford University)I. Chorkendorff

A. K. DatyeA. T. DelarivaS.R. Challa

¡ Haldor Topsøe A/S:

¡ Danish Technical University:

¡ University of New Mexico:

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