Systematic study of the oxidation of methane using supported gold palladium
nanoparticles under mild aqueous conditions
Supplementary Information
Mohd Hasbi Ab Rahim,1,2 Michael M. Forde,1 Ceri Hammond,1 Robert L. Jenkins,1 Nikolaos
Dimitratos,1,3 Jose Antonio Lopez-Sanchez,1,4 Albert F. Carley,1Stuart H. Taylor, 1 David J.
Willock1 and Graham J. Hutchings1*
1
Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place,
Cardiff, UK, CF10 3AT, UK
2
Present address: Faculty of Industrial Sciences & Technology, University Malaysia Pahang,
Lebuhraya Tun Razak, 26300, Kuantan, Pahang, Malaysia
3
Present address: Department of Chemistry, University College London, 20 Gordon Street,
WC1H 0AJ London (UK) and Research Complex at Harwell, Rutherford Appleton Laboratory,
Harwell Oxford, Didcot, OX11 0FA (UK)
4
Present address: Stephenson Institute for Renewable Energy, Chadwick Building, University
of Liverpool, Liverpool L69 4ZF (UK)
Table S1 Liquid phase oxidation of methane using homogeneous and heterogeneous catalysts with H2O2
Entry
Catalyst
Product amount (μmol)
CH3OH [a]
HCOOH [a]
MeOOH
[a]
CH3OH Selec.
CO2 in
TOF [d]
Unreacted
H2O2
(%)[c]
(μmol) [e]
gas[b]
1
HAuCl4
7.74
37.93
0
10.25
13.8
11.18
27
2
HAuCl4/TiO2
3.40
29.60
25.78
14.02
4.7
14.56
109
3
HAuCl4
0.68
0
0.46
0.10
54.8
0.25
4960
4
5wt%Au-Pd/TiO2IW
2.49
0
0
1.01
71.1
0.70
15
Test Conditions Entries 1-4: Reaction Time: 30 min; CH4 pressure: 30 bar, Catalyst: 1.0 x 10-5 mol of metal; [H2O2]: 0.5M;. Solvent: H2O, 10 mL; reaction temperature:
90°C except entry 3: 50°C.
[a] Analysis
using 1H-NMR, [b] Analysis using GC-FID, [c] Methanol selectivity = (mol of CH3OH/ total mol of products) * 100, [d] Turn over frequency (TOF) = mol of
products / mol of metal / reaction time (h), [e] Assayed by Ce+4 (aq) titration.
Table S2 Effect of reaction temperature on catalytic performance of 2.5wt%Au-2.5wt%Pd/TiO2 for the selective oxidation of methane with
H2O2
Product amount (μmol)
Oxy. Productivity
CH3OH Select.
Entry
T (°C)
CH3OH
HCOOH
[a]
TOF
(Mol/kgcat/
MeOOH
[a]
Unreacted
CO2
b]
(%)
[c]
H2O2
[e]
Hour)[d]
[a]
(μmol) [f]
1
2
1.31
0
1.40
0.19
45.2
0.196
0.58
4471
2
30
1.55
0
1.28
0.20
51.2
0.205
0.61
935
3
50
1.89
0
1.57
0.37
49.3
0.250
0.77
383
4
70
2.02
0
1.38
0.76
48.6
0.246
0.83
43
5
90
2.49
0
0
1.01
71.1
0.180
0.70
15
Test conditions: Reaction Time: 30 min, Catalyst: 27.6 mg (1.0 x 10-5 mol of metal), CH4 pressure: 30 bar, Stirring rate: 1500 rpm, [H2O2]: 0.5M,, Solvent: H2O, 10 mL,
[a]
Analysis using 1H-NMR,
[b]
Analysis using GC-FID,
[c]
Methanol selectivity = (mol of CH3OH/ total mol of products) * 100,
[d]
Oxygenates productivity = mol of
oxygenates / Kgcat / reaction time (h), [e] Turn over frequency (TOF) = mol of oxygenates / mol of metal / reaction time (h), [f] Assayed by Ce+4 (aq) titration
Table S3 Effect of Au:Pd ratio on catalytic performance of 5wt% (Au-Pd)/TiO2 catalyst for the selective oxidation of methane with H2O2.
Product amount (μmol)
Unreacted
Au:Pd ratio
CH3OH Select.
Entry
TOF [d]
MeOOH
(wt%:wt%)
CH3OH
[a]
HCOOH
[a]
CO2
[b]
(%)
H2O2
[c]
(μmol) [e]
[a]
1
5Au
0.74
0
0.93
0.29
37.8
0.39
2979
2
4Au: 1Pd
0.93
0
2.53
0.15
25.8
0.72
798
3
2.5Au: 2.5Pd
1.89
0
1.57
0.37
49.3
0.77
383
4
1Au: 4Pd
1.64
0
0.54
0.13
71.0
0.46
85
5
5Pd
1.74
0
0.67
0.22
72.2
0.53
110
Test conditions: Reaction Time: 30 min, Reaction Temp: 50 oC, CH4 pressure: 30 bar, Catalyst: 1.0 x 10-5 mol of metal, [H2O2]:0.5M, Solvent: H2O, 10 mL, [a] Analysis using 1HNMR, [b] Analysis using GC-FID, [c] Methanol selectivity = (mol of CH 3OH/ total mol of products) * 100, [d] Turn over frequency (TOF) = mol of oxygenates / mol of metal /
reaction time (h), [e] Assayed by Ce+4 (aq) titration
Catalysts: synthesized via impregnation method and calcined at 400 oC in static air for 3 hours.
Table S4 Effect of support materials on the catalytic performance of 2.5wt% Au-2.5wt%Pd supported catalyst for the selective oxidation of
methane with H2O2.
Product amount (μmol)
Oxygenate
Unreacted
CH3OH Select.
Entry
Support
productivity
TOF [e]
MeOOH
CH3OH
[a]
HCOOH
[a]
CO2 in
gas[b]
(%)[c]
H2O2
(Mol/kgcat/
(μmol) [f]
[a]
Hour) [d]
1
TiO2
1.89
0
1.57
0.37
49.3
0.250
0.77
383
2
Carbon
0.63
0
0
1.55
28.9
0.046
0.44
87
3
CeO2
0.63
0
0.74
0.16
41.2
0.099
0.31
192
4
SiO2
0.30
0
0
1.31
18.6
0.022
0.32
58
5
γ-Al2O3
0.94
0
1.37
0.43
34.3
0.167
0.55
2942
Test conditions: Reaction Time: 30 min, Reaction Temp: 50 oC, CH4 pressure: 30 bar, Catalyst: 27.6 mg (1.0 x 10-5 mol of metal), [H2O2]: 0.5M, Solvent: H2O, 10 mL, [a] Analysis
using 1H-NMR,
[b]
Analysis using GC-FID
[c]
Methanol selectivity = (mol of CH3OH/ total mol of products) * 100,
[d]
Oxygenates productivity = mol of oxygenates / Kgcat /
reaction time (h), [e] Turn over frequency (TOF) = mol of oxygenates / mol of metal / reaction time (h), [f] Assayed by Ce+4 (aq) titration
Table S5 Effect of catalyst pre-treatment on the catalytic performance of 2.5wt%Au-2.5wt%Pd/TiO2 for the selective oxidation of methane with H2O2
Product amount (μmol)
Unreacted
CH3OH Select.
Entry
Pre-treatment
TOF
MeOOH
CH3OH
[a]
HCOOH
[a]
H2O2
[b]
CO2 in gas
(%)
[d]
[c]
[a]
(μmol) [e]
1
Static air, 400 oC
1.89
0
1.57
0.37
49.3
0.77
383
2
5%H2/Ar, 400 oC
0.58
0
0
<0.05
92.1
0.13
27
3
Static air, 400 oC then NaBH4 treatment
0.30
0
0
<0.05
85.7
0.07
27
4
Static air, 400 oC, then H2O2 treatment
0.40
0
0
<0.05
88.8
0.09
61
1.14
0
0.29
0.53
65.9
0.39
30
5
50%O2/He, 400oC
Test conditions: Reaction Time: 30 min, Reaction Temp: 50 oC, CH4 pressure: 30 bar, Catalyst: 27.6 mg (1.0 x 10-5 mol of metal), [H2O2]:0.5M, Solvent: H2O, 10 mL, [a] Analysis
using 1H-NMR, [b] Analysis using GC-FID, [c] Methanol selectivity = (mol of CH3OH/ total mol of products) * 100, [d] Turn over frequency (TOF) = mol of oxygenates / mol of
metal / reaction time (h), [e] Assayed by Ce+4 (aq) titration
Catalyst: Synthesised via impregnation method.
Figure S1 Pd (3d) and Au (4d) regions of the XPS spectra of 2.5wt%Au-2.5wt%Pd/TiO2
catalysts with different pre-treatments. (a) 400 oC in static air, (b) 400 oC in 5%H2/Ar flow, (c)
400 oC in static air and hydrogen peroxide treatment. The Pd0 signal is observed in the
samples treated under reducing conditions.
Figure S2 Log plot for data obtained in the oxidation of methane using 2.5wt%Au2.5wt%Pd/TiO2 with H2O2 as oxidant at variable initial methane pressure. Test conditions:
[H2O2]: 0.5M; T: 50 °C; stirring rate: 1500 rpm; reaction time: 0.5h; catalyst mass: 28mg
(1x10-5 mole (AuPd)).
(i)
Pd0
Pd2+
Pd0
Pd2+
(ii)
Pd0
Pd2+
Pd0
Pd2+
Figure S3 Deconvolution of Pd (3d) spectra of used 2.5wt%Au-2.5wt%Pd/TiO2 catalyst, (i)
after methane reaction with added H2O2 (ii) after methane reaction with H2O2 generated insitu from H2/O2 . The percentage of Pd2+ calculated for each used catalyst after methane
oxidation was 56.5 % and 52.7 % respectively, both values being significantly lower than that
calculated for the freshly calcined catalyst (85.5%).