Electronic Supplementary Material (ESI) for Catalysis Science & Technology.
This journal is © The Royal Society of Chemistry 2016
Supporting Information
Fe/γ-Al2O3 and Fe-K/γ-Al2O3 as Reverse Water-Gas Shift Catalysts
Jason A. Loiland1, Matthew J. Wulfers1, Nebojsa S. Marinkovic2, and Raul F. Lobo1,*
1Center
for Catalytic Science and Technology, Department of Chemical and Biomolecular
Engineering, University of Delaware, Newark, DE 19716, USA
2Department
of Chemical Engineering, Columbia University, New York, NY 10027, USA
Corresponding Author e-mail: [email protected]
Quantity Adsorbed (cm3/g)
250
200
150
100
50
0
0.0
0.2
0.4
0.6
0.8
Relative Pressure (P/Po)
Figure S1. N2 adsorption isotherm for 10% Fe – 2.5% K/Al2O3.
1.0
Intensity (a.u.)
Al2O3
4.5% Fe/Al2O3
4.2% Fe - 3.4% K/Al2O3
10
20
30
40
50
60
70
2 (o)
Figure S2. Powder XRD patterns of 4.2% Fe – 3.4% K/Al2O3, 4.5% Fe/Al2O3 and γ–Al2O3.
Figure S3. Elemental mapping images of 4.5% Fe/Al2O3. Iron highlighted (green, top left),
oxygen highlighted (yellow, top right), and regular SEM image (bottom).
Figure S4. Elemental mapping images of 4.2% Fe – 3.4% K/Al2O3. Regular SEM image (top
left), oxygen highlighted (yellow, top right), potassium highlighted (red, bottom right), and iron
highlighted (green, bottom right).
160
140
753 K
120
753 K
100
743 K
733 K
723 K
80
60
40
Period in which partial
pressures were varied
20
0
Rate CO formation (mmol gcat-1 h-1)
Rate CO formation (mmol gcat-1 h-1)
160
140
120
100
80
60
753 K
20
0
0
250
500
750
1000 1500
Time on Stream (min)
753 K
743 K
733 K
723 K
40
Period in which partial
pressures were varied
0
250
500
750
10001500
Time on Stream (min)
Figure S5. CO formation rates on 4.2% Fe -3.4% K/Al2O3 (left) and 4.5% Fe/Al2O3 (right) during
experiments in which kinetic parameters were determined with equimolar concentrations of CO2
and H2 in the feed. Temperatures are indicated in the figure, and the partial pressures of CO2 and
H2 were 15 kPa.
4.5
4.2% Fe - 3.4% K/Al2O3
4.5% Fe/Al2O3
4.0
ln(Rate)
Emeas = 69 kJ mol-1
Emeas = 46 kJ mol-1
3.5
0.00132
0.00134
0.00136
0.00138
-1
1/T (K )
Figure S6. Arrhenius plots from conversion of CO2 on 4.5% Fe/Al2O3 and 4.2% Fe - 3.4%
K/Al2O3. Reaction conditions: T = 723-753 K, PCO2 = 15 kPa, PH2 = 15 kPa, Ftot = 75 sccm.
CO Formation Rate (mmol h-1 gcat.-1)
Fe-K/Al2O3
70
60
kH/kD  1.03
50
40
30
20
Fe/Al2O3
0
50
kH/kD  0.65
100
150
Relative Time on Stream (min.)
Figure S7. CO formation rates on 4.5% Fe/Al2O3 and 4.2% Fe – 3.4% K/Al2O3 while flowing H2
(open circles) or D2 (filled circles). Reaction conditions: T = 723 K, PCO2 = 15 kPa, PH2 or PD2 =
15 kPa, Ftot. = 75 sccm.
8x10-9
Ion current (A)
CO2
6x10-9
Helium
purge
H2
m/z = 2
-9
4x10
H2
Helium
purge
m/z = 28
2x10-9
m/z = 18
0
100
120
140
160
180
200
Relative Time (min)
Figure S8. Ion currents at m/z = 2 (H2), 18 (H2O), and 28 (CO) during H2/CO2 switching
experiments on 4.2% Fe – 3.4% K/Al2O3. Arrows with a label indicate a change in gas
composition to the indicated gas. Reaction conditions: T = 773 K, FHe = 36 sccm, FH2 or FCO2 = 4
sccm. The figure is a modification of Figure 2.
m/z = 18
m/z = 28
m/z = 40
m/z = 44
Ion Current (A)
3x10-8
2x10-8
1x10-8
10% CO2 + 1% Ar + He
0
0
2
4
6
8
10
Time (min)
Figure S9. Transient response curves for Ar (m/z = 40), CO2 (m/z = 28, 44), CO (m/z = 28), and
H2O (m/z = 18) during gas switching experiments over Fe-K/Al2O3. Gas flow was switched from
10% H2/He to 10% CO2/1% Ar/He. Reaction conditions: T = 773 K, total flow rate = 40 sccm.
120
(1) during CO2
(2) after 30 min helium purge
% Reflectance
100
2904
80
60
40
1568
4000
3500
3000
1800
1600
1343
1400
1200
Wavenumber (cm-1)
Figure S10. Diffuse reflectance IR spectra collected in situ of 7.7% Fe – 3.4% K/Al2O3 after 30
min of CO2 flow (purple) and after purging the chamber for 30 min with helium. The
temperature was 723 K.
1.5
(2) end pretreatment
(4) end 2nd reduction
1.0
800
(1) before heating
(3) end of CO2 flow
0.5
Fraction of Fe3+
0.75
600
0.50
0.25
400
Temperature (K)
(E)
20% H2 / 80% He
100% He
20% CO2 / 80% He
1.00
0.00
0.0
0
7100 7120 7140 7160 7180 7200
50
100
150
Time (min)
200
200
250
Energy (eV)
Figure S11. XANES spectra collected in-situ (left) during a gas switching experiment on 4.5%
Fe/Al2O3 and fraction of Fe3+ (right) over the duration of the experiment. The catalyst was
pretreated in H2, and the H2 flow was then stopped while CO2 was added simultaneously. The
catalyst was then re-reduced in H2 after the period in CO2. Trxn = 773 K, PCO2 or PH2 = 20 kPa, Ftot
= 10 sccm.
1.5
(2) end pretreatment
(4) end 2nd reduction
20% H2 / 80% He
100% He
20% CO2 / 80% He
1.00
1.0
800
0.5
Fraction of Fe3+
(1) before heating
(3) end of CO2 flow
600
0.50
0.25
400
Temperature (K)
(E)
0.75
0.00
0.0
7100
200
0
7120
7140
7160
7180
7200
50
100
150
200
Time (min)
Energy (eV)
Figure S12. XANES spectra collected in situ (left) during a gas switching experiment on 4.2% Fe – 3.4%
K/Al2O3 and fraction of Fe3+ (right) over the duration of the experiment. The catalyst was pretreated in H2,
and the H2 flow was then stopped while CO2 was added simultaneously. The catalyst was then re-reduced in
H2 after the period in CO2. Reaction conditions: Trxn = 773 K, PCO2 or PH2 = 20 kPa, Ftot = 10 sccm.
1.5
(2) end pretreatment
(3) during CO2/H2 flow
(3) end of CO2/H2 flow
1.00
800
Fraction Fe3+
(E)
(1) before heating
0.5
600
0.50
50% He / 50% H2
50% CO2 / 50% H2
0.25
0.00
0.0
7100
400
Temperature (K)
0.75
1.0
7120
7140
7160
7180
Energy (eV)
7200
0
50
100
150
200
200
Time (min)
Figure S13. XANES spectra collected in situ before and during flow of CO2/H2 on 4.2% Fe –
3.4% K/Al2O3 (left) and fraction of Fe3+ determined form XANES spectra over the duration of
the experiment (right). Trxn = 823 K, Ftot = 10 sccm.
1.5
(2) end pretreatment
(3) during CO2/H2 flow
(3) end of CO2/H2 flow
800
(E)
0.5
0.0
600
0.50
50% He / 50% H2
50% H2 / 50% CO2
0.25
400
Temperature (K)
(1) before heating
Fraction of Fe3+
0.75
1.0
7100
1.00
0.00
7120
7140
7160
7180
Energy (eV)
7200
0
25
50
75
200
Time (min)
Figure S14. XANES spectra collected in situ before and during flow of CO2/H2 on 4.5% Fe/Al2O3
(left) and fraction of Fe3+ determined form XANES spectra over the duration of the experiment
(right). Trxn = 823 K, Ftot = 10 sccm.
-7
H2
H2/D2
H2
CO2 + H2/D2
H2
Ion Current (A)
10
m/z = 2
m/z = 3
m/z = 4
m/z = 28
10-8
10-9
10-10
10-11
20
30
40
50
60
Time (min.)
Figure S15. Ion currents at m/z = 2 (H2), 3 (HD), 4 (D2), and 28 (CO) during flow of 7.5 kPa H2,
7.5 kPa H2 + 7.5 kPa D2, and 7.5 kPa H2 + 7.5 kPa D2 +15 kPa CO2 on Fe/Al2O3. Arrows with a
label indicate a change in gas composition to the indicated gas. Reaction conditions: T = 753 K,
Ftot = 75 sccm.
Table S1. Catalyst precursor amounts, nominal weight loadings, and actual weight loadings.
Catalyst
Mass Fe
Precursor / g
Mass K
Precursor / g
Mass Al2O3
/g
Nominal
Fe
Loading /
wt %
Nominal
K
Loading /
wt %
Actual Fe
Loading /
wt %
Actual K
Loading /
wt %
1Fe 3K
4Fe
10Fe
8Fe 3K
5Fe 1K
4Fe 4K
0.22
0.994
1.99
1.99
1.50
0.994
0.19
--0.243
0.10
0.243
2.75
2.75
2.75
2.75
2.75
2.75
1.05
4.8
9.1
8.7
6.9
4.5
3.7
--4.3
1.9
4.6
0.9
4.5
9.1
7.7
6.7
4.2
3.5
3.4
2.3
3.4