Is oxidative coupling the royal road for the valorization of methane to olefines?
Unifying Concepts in Catalysis
Cluster of Excellence
Is oxidative coupling the royal road
for the valorization of methane to olefines?
R. Schomäcker, V. Fleischer, S. Parishan, J. Sauer, M. Baldowski,
K. Kwarpien, A. Thomas, S. Mavlyankariev, R. Horn, A. Trunschke,
P. Schwach, R. Schlögl, Y.Cui, N. Nilius, H.J. Freund, F. Rosowski
U. Simon, M. Yildiz, O. Görke, H. Godini, G. Wozny
Presentation at „Changing Landscape…“-Workshop,
Washington, DC, March 7-8, 2016
The Scenario
Working hypothesis
Oxidative coupling of methane is economically viable, if:
- added value is high
- methane is not wasted
- energy demand is appropriate
- capital expenditure is reasonable
Pioneering work
G.F. Keller, M.M. Bhasin,
J. Catal. 1982, 73, 9
catalyst
M. Hinsen, M. Baerns,
Chem. Z. 1983, 107, 223
catalyst
A.C. Jones, J.J. Leonardo et al., US patent 4 443644, 1984
periodic feed
strategy
160
140
papers
120
100
Reihe1
80
60
40
20
0
1985
1990
1995
2000
2005
2010
year
U. Zavyalova, M. Holen, R. Schlögl, M. Baerms, ChemCatChem, 2011, 3, 1935
Milestone 1: The Lunsford Mechanism of OCM
methane activation
2CH 4
2CH 3 2[ Li O ]H
2[ Li O ]
catalyst
regeneration
1
O2
2
. Lunsford
mechanism
[ Li O 2 ]
[ Li VO ]
product
formation
C 2 H 6 H 2O
•
Optimal loading for initial activity: 0.5 wt% Li/MgO
•
No stable Li/MgO-catalyst
•
Still active after Li-Loss
•
No selectivity
J. H. Lunsford, Angew. Chem. 1995, 107, 1059 – 1070;
Angew. Chem. Int. Ed. Engl. 1995, 34, 970 – 980
Milestone 2: The first kinetic model
Z. Stansch, L. Mleczko, M.B. ,
Ind. Eng. Chem. Res. 1997, 36, 2568
LaO2O3 (27at%)/CaO
Milestone 3: Mn-doped Na2WO4/SiO2
X.Fang et al, J. Mol. Catal. (China), 6 (1992) 427
X CH4
D.J. Wang, M.P. Rosynek, J.H. Lunsford, J. Catal.
155 (1995) 390
S C2
Y C2
Na2WO4/SIO2
0.11
0.75
0.08
MnOx/SiO2
0.16
0.34
0.07
Na2WO4/Mn/
SiO2
0.37
0.65
0.24
Z. Jiang, H. Gong, S. Li, Stud. Surf. Sci. Catal. 112 (1997)
481
200 g batches with spray drying technology
H. Liu, X. Wang, D. Yang, R. Gao, Z. Wang, J.
Yang, J. Nat. Gas. Chem. 17 (2008) 59
U. Simon, O. Görke, A. Bertold, S. Arndt, R. Schomäcker,
H. Schubert, Chem. Eng. J.168 (2011) 1352-1359
Milestone 4: OCM at La2O3
CH4
COx
[1]
O2
[1]
650 °C
O2EPR
[2,3]
CO2
[6]
[8]
EA = 39 kcal/mol
CH4 CH3
10 kcal/mol
[4,7]
O-
XPS EPR
LaxFeyO3
CH4
CH3
[4,5]
O22-
La2O2CO3
CH3
CH4
EPR
?
O2- [7]
XPS
EPR XPS
IR
increase selectivity!
LaxCeyOz
[1] C. Louis, T.L. Chang, M. Kermarec, T. Le Van, J.M. Tatibuët, M. Che, Colloids Surfaces A Physicochem. Eng. Asp. 72 (1993) 217
[2] T. Levan, M. Che, J.M. Tatibouet, M. Kermarec, J. Catal. 142 (1993) 18
[3] J.-L. Dubois, M. Bisiaux, H. Mimoun, C.J. Cameron, Chem. Soc. Japan Chemistry (1990) 967
[4] M.S. Palmer, M. Neurock, M.M. Olken, J. Am. Chem. Soc. 124 (2002) 8452
[5] C. Lin, K.D. Campbell, J. Wang, J.H. Lunsford, J. Phys. Chem. 90 (1986) 534
[6] Y. Sekine, K. Tanaka, M. Matsukata, E. Kikuchi, Energy and Fuels 23 (2009) 613
[7] C. Au, T. Zhou, W. Lai, C. Ng, Catal. Letters 49 (1997) 53
[8] V.J. Ferreira, P. Tavares, J.L. Figueiredo, J.L. Faria, Catal. Commun. 42 (2013) 50
[9] S. Gadewar, S.A. Sardar, P. Grosso, A. Zhang, V. Julka, P. Stolmanov, Continuous Process for Converting Natural Gas to Liquid
Hydrocarbons, U.S. Patent US8921625B2, 2014 (Siluria Technologies)
Milestone 5: unconventional approaches
Who is who in OCM
Author
Publications*
Citations*
M. Baerns
J.H. Lunsford
V.R. Chaudhary
J.R.H. Ross
K. Fujimoto
J.B. Moffat
C. Mirodatos
A.G. Anshitz
47
43
36
36
33
31
29
25
1323
1696
926
666
728
528
334
261
* Web of Science, 25.7.2014
The UNICAT concept
Multi scale approach for atomic to plant level
Model studies for understanding complexity
Feasibility studies in mini-plant
* table adopted from E. V. Kondratenko, M. Baerns
Handbook of Heterogeneous Catalysis, Vol. 6, Ch. 13.17, 2008
Multi scale approach to OCM
G. Wozny
R. Schlögl
M. Kraume
H.J. Freund
T. Risse
H. Schubert
R. Horn
A. Thomas
R. Schomäcker
M. Driess
J. Sauer
M. Scheffler
Mechanism of Oxidative Coupling of Methane
2 CH4 + O2 → C2H4 + 2 H2O (+ CO2)
+ O2
COx
O2ad
*
CH3
O2ad
*
O
+ CH 3
+ O2
+ O2
CH4
O2
COx
+ CH 3
C2H6
C2H6
C2H5
O
O
C2H4
Origin of low selectivity
- OCM is initiated by oxygen activation (AFM, DFT, Model catalysts)
- Selective and inselective oxygen species at all catalysts (TAP, TPSR)
- Electron donors (dopants, defects) cause oxygen dissociation (AFM, Model catalyst)
- Formation of methyl radicals at selective oxygen species (Kinetics, KIE, Model cat.)
- Combustion of methane at inselective species (Kinetics, KIE)
- Parallel gas phase combustion at increased oxygen partial pressure (Profile R.)
K. Kwapien, J.Paier, J. Sauer, M. Geske, U. Zavyalowa, R. Horn, P. Schwach, A. Trunschke, R. Schlögl, Angew. Chem. Int, Ed. 2014, 53, 11-6
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund, Angew.Chem.Int.Ed. 2013, 52, 11385
B. Beck, V. Fleischer, S. Arndt, M. G. Hevia, A. Urakawa, P. Hugo, R. Schomäcker Catalysis Today 2014, 228, 212–218
The Puzzle of Information
How to get started?
Searching for more pieces?
Joining central pieces?
A simple example
2
A simple example
2
Experiments in a TAP reactor
In collaboration with J. Perez-Ramires, ICIQ, Taragona, now ETH Zurich
Pump-probe experiments in a TAP reactor
- Increasing delay of CH4
leads to decrease of CO2
and C2H6 stays constant
- weakly adsorbed oxygen
leads to total oxidation
* + O2
*O2
- strongly adsorbed oxygen
is responsible for methyl
radical formation
*+O
*O
- smaller ratio between
weakly and strongly
adsorbed oxygen at
Mn/Na2WO4/SiO2
Dynamic experiment
750 °C, 30 nml/min, 1g catalyst
S(C2) = 0.89
• C2 Selectivity unexpacted
high in dynamic experiments
at constant temperature
• less oxygen species on the
catalyst surface than in
steady state exp.
2
Characteristics of MgO prior to reaction
S-MgO
C-MgO
SG-MgO
Mg oxidation
Ultra pure commercial MgO
Sol-gel synthesis
HT-MgO
MW-MgO
Hydrothermal post treatment
Hydrothermal post treatment
in microwave autoclave
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
2
Deactivation of C-MgO
t = 230 h
t=0h
t=6h
t = 25 h
t = 66 h
Rate of methane consumption decreases with decreasing number of
monoatomic steps observed with CO as probe molecule by IR
P. Schwach, M. G. Willinger, A. Trunschke, R. Schlögl ,
Angewandte Chemie International Edition 2013, 52, 11381–11384
Structure sensitivity of MgO during reaction
Eley-Rideal mechanism
•
•
•
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
CH4 adsorbes and is activated
O2 leads to methyl radical formation
Superoxide identified by EPR
Mechanism of OCM at MgO
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
Baldowski, Sauer, unpublished
Energy, Gibbs free energy (kJ/mol)
Mechanism of OCM at MgO
CH3−/H+
18
121
O2
ads
+ O2
TS
28
272
Int-1a
Int-1b
O2 −
24
254
4
136
~O2
10
217
d(O-O)/d(Mg-O)
~O2
122/215
1013 K, 0.1 MPa
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
Baldowski, Sauer, unpublished
127/227
Int-2
-5
224
− CH3
135/253
Mo-doped CaO films on Mo(001)
Mechanism:
•Mo-donors in CaO transfer charges
into O2 molecules bound to surface
• Formation of pre-disscoiated O2species
• Final dissociation via electron
tunneling from STM tip
Experimental evidence:
• Work function increase after O2 dosage
only in the case of doped films
• no O2 adsorption at 300 K for pristine
CaO
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund,
Angew.Chem.Int.Ed. 2013, 52, 11385
Mo-doped CaO films on Mo(001)
O-O
O2
8.0nm
8.0nm
As dosed O2: Molecular species
After dissociation with STM tip
(scanning below 2.5 V sample bias)
(electron injection with 3.0 eV energy)
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund,
Angew.Chem.Int.Ed. 2013, 52, 11385
Doping of MgO with Fe
P. Schwach, M. Willinger, A. Trunschle, R. Schlögl
Angew.Chem.Int.Ed. 2013, 52, 11381
OCM on MgO
CH3
O2- [Mg2+, HO-]
O2
CH4
[Mg2+,
CH3
H2O
58
180
O2-
CH3
CH4
O- [Mg2+, HO-]
CH4
HO2- [Mg2+, HO-]
Fe doping [2] or
N2O as oxidant [3]
increase selectivity
]
-7
114
133
241
COx
CH3
103
226
114
119
[Mg2+, O22- ]
CH4
COx
H2O
CH3
EA 0K [kJ/mol]
Gibbs Free Energy, 1013 K, 0.1 MPa
[1] K. Kwapien, J. Paier, J. Sauer, M. Geske, U. Zavyalova, R. Horn, P. Schwach, A. Trunschke, R. Schlögl, Angew. Chemie - Int. Ed. 53 (2014) 8774
[2] P. Schwach, M.G. Willinger, A. Trunschke, R. Schlögl, Angew. Chemie - Int. Ed. 52 (2013) 11381
[3] H. Yamamoto, H.Y. Chu, M.T. Xu, C.L. Shi, J.H. Lunsford, 142 (1993) 325
Bi-metallic Na2WO4 /Mn/SiO2 catalysts for OCM
• Provides/stores
lattice oxygen
• Works without gas
phase oxygen
• Deep oxidation
catalyst for methane
How does it
work?
• Selective OCM
catalysts
• Needs oxygen
source to form
methyl radicals
OCM in transient
experiments
Support variation for MnxOy/Na2WO4/SiO2
pre-catalyst
silica support
commercial
nanostructured
(SBA-15)
catalyst
Impregnation
Calcination
Na2WO4 · 2 H2O
Mn(ac)2 ·4 H2O
750°C
Up-scaling of catalyst synthesis
M. Yildiz, Y. Aksu, U. Simon, K. Kailasam, O. Goerke, F. Rosowski,
R. Schomäcker, A. Thomas, S. Arndt Chem. Commun. 2014, 50, 14440
Support variation for MnxOy/Na2WO4/SiO2
Distribution of
Mn-Na2WO4 on
commercial
Green - W
Red - Mn
nanostructured
(SBA-15)
silica supports
M. Yildiz, U. Simon, T. Otremba, K. Kailasam, Y. Aksu, A. Thomas, R. Schomäcker, S. Arndt Catalysis Today 2014, 228, 5-14
H.R. Godini, A. Gili, O. Görke, S. Arndt, U. Simon, A. Thomas, R. Schomäcker, G. Wozny, Catalysis Today, 2014, DOI
10.1016/j.cattod.2014.01,005
Support variation for MnxOy/Na2WO4/SiO2
X
X
Mn-Na2WO4/SBA-15
X
Mn-Na2WO4/commercial silica
Testing in lab scale reactor at 750 °C (C2-Yield= 12 %)
In mini-plant membrane reactor at 810 °C (C2-Yield= 23 %)
M. Yildiz, Y. Aksu, U. Simon, K. Kailasam, O. Goerke, F. Rosowski,
R. Schomäcker, A. Thomas, S. Arndt Chem. Commun. 2014, 50, 14440
Dynamic Experiments
• At reaction temperature the
catalyst is oxidized by air
• Reactor is purged with Helium
to remove oxygen in gas phase
and weakly adsorbed one
• Defined amount of methane is
dosed into the reactor
• Reaction mixture is analysed
by mass spectroscopy
Catalyst activity can be
analyzed without gas phase
oxidation reactions
pulse
Molefraction (%)
Repetitive dynamic experiments
•
Repetitive methane pulses
allow to study the available
amount of oxygen
Na2WO4 (5%)/Mn(2%)@Quartz
O (µmol/gcat)
20.5
Na2WO4 (5%)/Mn(2%)@SBA15
68.9
OCM at Na2WO4/Mn/SiO2
• Infeasibility of various spectroscopic techniques
• mechanism proposed by analogy to other systems
CH4 COx CH4
[1]
O2
O2,ads
O2-
cus
H2O
CH3
COx
HO2-
Mn doping [2]
increases activity
and selectivity
OCH4
CH3
COx
CH3
O22-
[1] B. Beck, V. Fleischer, S. Arndt, M.G. Hevia, A. Urakawa, P. Hugo, R. Schomäcker, Catal. Today 228 (2014) 212
[2] S. Ji, T. Xiao, S. Li, C. Xu, R. Hou, K.S. Coleman, M.L.H. Green, Appl. Catal. 225 (2002) 271
H2O
Network of surface reactions at MnxOy/Na2WO4/SiO2
OCM in a mini-plant reactor
Fluidized Bed Reactor
+
Isothermal reaction
- Sensitive to free gas volume
Reactor performance
2%Mn-2.2%Na2WO4/SiO2 catalyst, particle size 250-450 μm
Bed height: 10 cm, CH4:O2 = 1.7 to 10,
Feed Flow rate: 0.1 l/min – 40 l/min, 45 37
g catalyst
OCM membrane reactor set-up
Alumina
Performance indicators of the membrane reactor
2%Mn-5%Na2WO4/SiO2 catalyst (4 g), average particle size 250-450 μm
Contours were made by using 40 experimental data
Reactor concept: Chemical looping
Operation steps:
1. O2 is dosed to oxidize
the catalyst
2. Reactor is purged with
inert gas to remove gas
phase oxygen
3. CH4 dosage to perform
OCM
4. Purge with He to remove
unconverted methane
Continuous operation
Early pulses
Late pulses
Early pulses
Late pulses
Looping
XCH4
0.28
SC2
0.78
Y
0.22
STY
83
with diluent
µmol(C2)
/g*h
Steady State
XCH4
0.29
SC2
0.63
Y
0.18
STY
µmol(C2)
/g*h
2 g catalyst, 1 ml CH4 pulse, 1 ml O2 pulse, 775 °C, 30 nml/min
529
Continuous operation
800°C
2 g catalyst, 1 ml CH4 pulse, 1 ml O2 pulse, 30 nml/min
Economic Analysis
Simulations with Aspen Plus & Aspen Process Economic Analyzer v8.8
Production capacity is one million tonnes per year
Ethylene price 947 Euro/tone
1. Case I (OCM Reaction Unit + CO2 separation Unit+Demethanizer
Unit+C2-Splitter Unit)
2. Case II (OCM Reaction Unit + CO2 separation Unit + Demethanizer
Unit + C2-Splitter Unit + Ethane Dehydrogenation Unit)
3. Case III (OCM Reaction Unit + C2H4 adsorption/Desorption Unit +
C2-Splitter Unit + Ethane Dehydrogenation Unit)
OCM to Ethylene (Case I)
Amine scrubbing (30%wt MEA)
Energy needed: 8 GJ/t-CO2
Energy cost associated: 14.3 €/t-CO2
OCM reactor: Mn-Na2WO4/SiO2 catalyst
Membrane reactor (40% conv. & 62% sel.)
Cluster of Excellence
Is oxidative coupling the royal road
for the valorization of methane to olefines?
R. Schomäcker, V. Fleischer, S. Parishan, J. Sauer, M. Baldowski,
K. Kwarpien, A. Thomas, S. Mavlyankariev, R. Horn, A. Trunschke,
P. Schwach, R. Schlögl, Y.Cui, N. Nilius, H.J. Freund, F. Rosowski
U. Simon, M. Yildiz, O. Görke, H. Godini, G. Wozny
Presentation at „Changing Landscape…“-Workshop,
Washington, DC, March 7-8, 2016
The Scenario
Working hypothesis
Oxidative coupling of methane is economically viable, if:
- added value is high
- methane is not wasted
- energy demand is appropriate
- capital expenditure is reasonable
Pioneering work
G.F. Keller, M.M. Bhasin,
J. Catal. 1982, 73, 9
catalyst
M. Hinsen, M. Baerns,
Chem. Z. 1983, 107, 223
catalyst
A.C. Jones, J.J. Leonardo et al., US patent 4 443644, 1984
periodic feed
strategy
160
140
papers
120
100
Reihe1
80
60
40
20
0
1985
1990
1995
2000
2005
2010
year
U. Zavyalova, M. Holen, R. Schlögl, M. Baerms, ChemCatChem, 2011, 3, 1935
Milestone 1: The Lunsford Mechanism of OCM
methane activation
2CH 4
2CH 3 2[ Li O ]H
2[ Li O ]
catalyst
regeneration
1
O2
2
. Lunsford
mechanism
[ Li O 2 ]
[ Li VO ]
product
formation
C 2 H 6 H 2O
•
Optimal loading for initial activity: 0.5 wt% Li/MgO
•
No stable Li/MgO-catalyst
•
Still active after Li-Loss
•
No selectivity
J. H. Lunsford, Angew. Chem. 1995, 107, 1059 – 1070;
Angew. Chem. Int. Ed. Engl. 1995, 34, 970 – 980
Milestone 2: The first kinetic model
Z. Stansch, L. Mleczko, M.B. ,
Ind. Eng. Chem. Res. 1997, 36, 2568
LaO2O3 (27at%)/CaO
Milestone 3: Mn-doped Na2WO4/SiO2
X.Fang et al, J. Mol. Catal. (China), 6 (1992) 427
X CH4
D.J. Wang, M.P. Rosynek, J.H. Lunsford, J. Catal.
155 (1995) 390
S C2
Y C2
Na2WO4/SIO2
0.11
0.75
0.08
MnOx/SiO2
0.16
0.34
0.07
Na2WO4/Mn/
SiO2
0.37
0.65
0.24
Z. Jiang, H. Gong, S. Li, Stud. Surf. Sci. Catal. 112 (1997)
481
200 g batches with spray drying technology
H. Liu, X. Wang, D. Yang, R. Gao, Z. Wang, J.
Yang, J. Nat. Gas. Chem. 17 (2008) 59
U. Simon, O. Görke, A. Bertold, S. Arndt, R. Schomäcker,
H. Schubert, Chem. Eng. J.168 (2011) 1352-1359
Milestone 4: OCM at La2O3
CH4
COx
[1]
O2
[1]
650 °C
O2EPR
[2,3]
CO2
[6]
[8]
EA = 39 kcal/mol
CH4 CH3
10 kcal/mol
[4,7]
O-
XPS EPR
LaxFeyO3
CH4
CH3
[4,5]
O22-
La2O2CO3
CH3
CH4
EPR
?
O2- [7]
XPS
EPR XPS
IR
increase selectivity!
LaxCeyOz
[1] C. Louis, T.L. Chang, M. Kermarec, T. Le Van, J.M. Tatibuët, M. Che, Colloids Surfaces A Physicochem. Eng. Asp. 72 (1993) 217
[2] T. Levan, M. Che, J.M. Tatibouet, M. Kermarec, J. Catal. 142 (1993) 18
[3] J.-L. Dubois, M. Bisiaux, H. Mimoun, C.J. Cameron, Chem. Soc. Japan Chemistry (1990) 967
[4] M.S. Palmer, M. Neurock, M.M. Olken, J. Am. Chem. Soc. 124 (2002) 8452
[5] C. Lin, K.D. Campbell, J. Wang, J.H. Lunsford, J. Phys. Chem. 90 (1986) 534
[6] Y. Sekine, K. Tanaka, M. Matsukata, E. Kikuchi, Energy and Fuels 23 (2009) 613
[7] C. Au, T. Zhou, W. Lai, C. Ng, Catal. Letters 49 (1997) 53
[8] V.J. Ferreira, P. Tavares, J.L. Figueiredo, J.L. Faria, Catal. Commun. 42 (2013) 50
[9] S. Gadewar, S.A. Sardar, P. Grosso, A. Zhang, V. Julka, P. Stolmanov, Continuous Process for Converting Natural Gas to Liquid
Hydrocarbons, U.S. Patent US8921625B2, 2014 (Siluria Technologies)
Milestone 5: unconventional approaches
Who is who in OCM
Author
Publications*
Citations*
M. Baerns
J.H. Lunsford
V.R. Chaudhary
J.R.H. Ross
K. Fujimoto
J.B. Moffat
C. Mirodatos
A.G. Anshitz
47
43
36
36
33
31
29
25
1323
1696
926
666
728
528
334
261
* Web of Science, 25.7.2014
The UNICAT concept
Multi scale approach for atomic to plant level
Model studies for understanding complexity
Feasibility studies in mini-plant
* table adopted from E. V. Kondratenko, M. Baerns
Handbook of Heterogeneous Catalysis, Vol. 6, Ch. 13.17, 2008
Multi scale approach to OCM
G. Wozny
R. Schlögl
M. Kraume
H.J. Freund
T. Risse
H. Schubert
R. Horn
A. Thomas
R. Schomäcker
M. Driess
J. Sauer
M. Scheffler
Mechanism of Oxidative Coupling of Methane
2 CH4 + O2 → C2H4 + 2 H2O (+ CO2)
+ O2
COx
O2ad
*
CH3
O2ad
*
O
+ CH 3
+ O2
+ O2
CH4
O2
COx
+ CH 3
C2H6
C2H6
C2H5
O
O
C2H4
Origin of low selectivity
- OCM is initiated by oxygen activation (AFM, DFT, Model catalysts)
- Selective and inselective oxygen species at all catalysts (TAP, TPSR)
- Electron donors (dopants, defects) cause oxygen dissociation (AFM, Model catalyst)
- Formation of methyl radicals at selective oxygen species (Kinetics, KIE, Model cat.)
- Combustion of methane at inselective species (Kinetics, KIE)
- Parallel gas phase combustion at increased oxygen partial pressure (Profile R.)
K. Kwapien, J.Paier, J. Sauer, M. Geske, U. Zavyalowa, R. Horn, P. Schwach, A. Trunschke, R. Schlögl, Angew. Chem. Int, Ed. 2014, 53, 11-6
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund, Angew.Chem.Int.Ed. 2013, 52, 11385
B. Beck, V. Fleischer, S. Arndt, M. G. Hevia, A. Urakawa, P. Hugo, R. Schomäcker Catalysis Today 2014, 228, 212–218
The Puzzle of Information
How to get started?
Searching for more pieces?
Joining central pieces?
A simple example
2
A simple example
2
Experiments in a TAP reactor
In collaboration with J. Perez-Ramires, ICIQ, Taragona, now ETH Zurich
Pump-probe experiments in a TAP reactor
- Increasing delay of CH4
leads to decrease of CO2
and C2H6 stays constant
- weakly adsorbed oxygen
leads to total oxidation
* + O2
*O2
- strongly adsorbed oxygen
is responsible for methyl
radical formation
*+O
*O
- smaller ratio between
weakly and strongly
adsorbed oxygen at
Mn/Na2WO4/SiO2
Dynamic experiment
750 °C, 30 nml/min, 1g catalyst
S(C2) = 0.89
• C2 Selectivity unexpacted
high in dynamic experiments
at constant temperature
• less oxygen species on the
catalyst surface than in
steady state exp.
2
Characteristics of MgO prior to reaction
S-MgO
C-MgO
SG-MgO
Mg oxidation
Ultra pure commercial MgO
Sol-gel synthesis
HT-MgO
MW-MgO
Hydrothermal post treatment
Hydrothermal post treatment
in microwave autoclave
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
2
Deactivation of C-MgO
t = 230 h
t=0h
t=6h
t = 25 h
t = 66 h
Rate of methane consumption decreases with decreasing number of
monoatomic steps observed with CO as probe molecule by IR
P. Schwach, M. G. Willinger, A. Trunschke, R. Schlögl ,
Angewandte Chemie International Edition 2013, 52, 11381–11384
Structure sensitivity of MgO during reaction
Eley-Rideal mechanism
•
•
•
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
CH4 adsorbes and is activated
O2 leads to methyl radical formation
Superoxide identified by EPR
Mechanism of OCM at MgO
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
Baldowski, Sauer, unpublished
Energy, Gibbs free energy (kJ/mol)
Mechanism of OCM at MgO
CH3−/H+
18
121
O2
ads
+ O2
TS
28
272
Int-1a
Int-1b
O2 −
24
254
4
136
~O2
10
217
d(O-O)/d(Mg-O)
~O2
122/215
1013 K, 0.1 MPa
Kwapien, Paier, Sauer, Geske, Zavyalova, Horn,
Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed., 2014, 53, 8774
Baldowski, Sauer, unpublished
127/227
Int-2
-5
224
− CH3
135/253
Mo-doped CaO films on Mo(001)
Mechanism:
•Mo-donors in CaO transfer charges
into O2 molecules bound to surface
• Formation of pre-disscoiated O2species
• Final dissociation via electron
tunneling from STM tip
Experimental evidence:
• Work function increase after O2 dosage
only in the case of doped films
• no O2 adsorption at 300 K for pristine
CaO
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund,
Angew.Chem.Int.Ed. 2013, 52, 11385
Mo-doped CaO films on Mo(001)
O-O
O2
8.0nm
8.0nm
As dosed O2: Molecular species
After dissociation with STM tip
(scanning below 2.5 V sample bias)
(electron injection with 3.0 eV energy)
Y. Cui, X. Shao, M. Baldofski, J. Sauer, N. Nilius, H.J. Freund,
Angew.Chem.Int.Ed. 2013, 52, 11385
Doping of MgO with Fe
P. Schwach, M. Willinger, A. Trunschle, R. Schlögl
Angew.Chem.Int.Ed. 2013, 52, 11381
OCM on MgO
CH3
O2- [Mg2+, HO-]
O2
CH4
[Mg2+,
CH3
H2O
58
180
O2-
CH3
CH4
O- [Mg2+, HO-]
CH4
HO2- [Mg2+, HO-]
Fe doping [2] or
N2O as oxidant [3]
increase selectivity
]
-7
114
133
241
COx
CH3
103
226
114
119
[Mg2+, O22- ]
CH4
COx
H2O
CH3
EA 0K [kJ/mol]
Gibbs Free Energy, 1013 K, 0.1 MPa
[1] K. Kwapien, J. Paier, J. Sauer, M. Geske, U. Zavyalova, R. Horn, P. Schwach, A. Trunschke, R. Schlögl, Angew. Chemie - Int. Ed. 53 (2014) 8774
[2] P. Schwach, M.G. Willinger, A. Trunschke, R. Schlögl, Angew. Chemie - Int. Ed. 52 (2013) 11381
[3] H. Yamamoto, H.Y. Chu, M.T. Xu, C.L. Shi, J.H. Lunsford, 142 (1993) 325
Bi-metallic Na2WO4 /Mn/SiO2 catalysts for OCM
• Provides/stores
lattice oxygen
• Works without gas
phase oxygen
• Deep oxidation
catalyst for methane
How does it
work?
• Selective OCM
catalysts
• Needs oxygen
source to form
methyl radicals
OCM in transient
experiments
Support variation for MnxOy/Na2WO4/SiO2
pre-catalyst
silica support
commercial
nanostructured
(SBA-15)
catalyst
Impregnation
Calcination
Na2WO4 · 2 H2O
Mn(ac)2 ·4 H2O
750°C
Up-scaling of catalyst synthesis
M. Yildiz, Y. Aksu, U. Simon, K. Kailasam, O. Goerke, F. Rosowski,
R. Schomäcker, A. Thomas, S. Arndt Chem. Commun. 2014, 50, 14440
Support variation for MnxOy/Na2WO4/SiO2
Distribution of
Mn-Na2WO4 on
commercial
Green - W
Red - Mn
nanostructured
(SBA-15)
silica supports
M. Yildiz, U. Simon, T. Otremba, K. Kailasam, Y. Aksu, A. Thomas, R. Schomäcker, S. Arndt Catalysis Today 2014, 228, 5-14
H.R. Godini, A. Gili, O. Görke, S. Arndt, U. Simon, A. Thomas, R. Schomäcker, G. Wozny, Catalysis Today, 2014, DOI
10.1016/j.cattod.2014.01,005
Support variation for MnxOy/Na2WO4/SiO2
X
X
Mn-Na2WO4/SBA-15
X
Mn-Na2WO4/commercial silica
Testing in lab scale reactor at 750 °C (C2-Yield= 12 %)
In mini-plant membrane reactor at 810 °C (C2-Yield= 23 %)
M. Yildiz, Y. Aksu, U. Simon, K. Kailasam, O. Goerke, F. Rosowski,
R. Schomäcker, A. Thomas, S. Arndt Chem. Commun. 2014, 50, 14440
Dynamic Experiments
• At reaction temperature the
catalyst is oxidized by air
• Reactor is purged with Helium
to remove oxygen in gas phase
and weakly adsorbed one
• Defined amount of methane is
dosed into the reactor
• Reaction mixture is analysed
by mass spectroscopy
Catalyst activity can be
analyzed without gas phase
oxidation reactions
pulse
Molefraction (%)
Repetitive dynamic experiments
•
Repetitive methane pulses
allow to study the available
amount of oxygen
Na2WO4 (5%)/Mn(2%)@Quartz
O (µmol/gcat)
20.5
Na2WO4 (5%)/Mn(2%)@SBA15
68.9
OCM at Na2WO4/Mn/SiO2
• Infeasibility of various spectroscopic techniques
• mechanism proposed by analogy to other systems
CH4 COx CH4
[1]
O2
O2,ads
O2-
cus
H2O
CH3
COx
HO2-
Mn doping [2]
increases activity
and selectivity
OCH4
CH3
COx
CH3
O22-
[1] B. Beck, V. Fleischer, S. Arndt, M.G. Hevia, A. Urakawa, P. Hugo, R. Schomäcker, Catal. Today 228 (2014) 212
[2] S. Ji, T. Xiao, S. Li, C. Xu, R. Hou, K.S. Coleman, M.L.H. Green, Appl. Catal. 225 (2002) 271
H2O
Network of surface reactions at MnxOy/Na2WO4/SiO2
OCM in a mini-plant reactor
Fluidized Bed Reactor
+
Isothermal reaction
- Sensitive to free gas volume
Reactor performance
2%Mn-2.2%Na2WO4/SiO2 catalyst, particle size 250-450 μm
Bed height: 10 cm, CH4:O2 = 1.7 to 10,
Feed Flow rate: 0.1 l/min – 40 l/min, 45 37
g catalyst
OCM membrane reactor set-up
Alumina
Performance indicators of the membrane reactor
2%Mn-5%Na2WO4/SiO2 catalyst (4 g), average particle size 250-450 μm
Contours were made by using 40 experimental data
Reactor concept: Chemical looping
Operation steps:
1. O2 is dosed to oxidize
the catalyst
2. Reactor is purged with
inert gas to remove gas
phase oxygen
3. CH4 dosage to perform
OCM
4. Purge with He to remove
unconverted methane
Continuous operation
Early pulses
Late pulses
Early pulses
Late pulses
Looping
XCH4
0.28
SC2
0.78
Y
0.22
STY
83
with diluent
µmol(C2)
/g*h
Steady State
XCH4
0.29
SC2
0.63
Y
0.18
STY
µmol(C2)
/g*h
2 g catalyst, 1 ml CH4 pulse, 1 ml O2 pulse, 775 °C, 30 nml/min
529
Continuous operation
800°C
2 g catalyst, 1 ml CH4 pulse, 1 ml O2 pulse, 30 nml/min
Economic Analysis
Simulations with Aspen Plus & Aspen Process Economic Analyzer v8.8
Production capacity is one million tonnes per year
Ethylene price 947 Euro/tone
1. Case I (OCM Reaction Unit + CO2 separation Unit+Demethanizer
Unit+C2-Splitter Unit)
2. Case II (OCM Reaction Unit + CO2 separation Unit + Demethanizer
Unit + C2-Splitter Unit + Ethane Dehydrogenation Unit)
3. Case III (OCM Reaction Unit + C2H4 adsorption/Desorption Unit +
C2-Splitter Unit + Ethane Dehydrogenation Unit)
OCM to Ethylene (Case I)
Amine scrubbing (30%wt MEA)
Energy needed: 8 GJ/t-CO2
Energy cost associated: 14.3 €/t-CO2
OCM reactor: Mn-Na2WO4/SiO2 catalyst
Membrane reactor (40% conv. & 62% sel.)