TPR and TPS

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TPR and TPS

• Temperature Programmed Reduction (TPR)
• characterisation of oxidic catalysts and other
  reducible catalysts
• qualitative information on oxidation state
• quantitative kinetic data
• optimisation of catalyst pretreatment
• Temperature Programmed Sulphiding (TPS)
• similar to TPR

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Examples of TPR
Reduction of oxidic species Study of coke
deposits Reduction of sulphides
MO H2 M H2O coke H2 hydrocarbons
H2O MS H2 M H2S
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Thermodynamics
?G0 (kJ/mol)
T (K)
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Equipment for TPR
reactor
H
/
Ar
2
molsieve
FID
TCD
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TPR of 9.1 wt CoO/Al2O3
o n m l k
j i h g f
Temperature (K)
Temperature (K)
Temperature (K)
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TPR Patterns of Reference Materials
TCD
CoAl2O4
FID
Co3O4
CoO
400 800 1200
Temperature (K)
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Influence of hard and soft Ions
CoMoO4
CoAl2O4
Co3O4
400 800 1200
Temperature (K)
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TPS of MoO3/Al2O3
Reactions MO H2 ? M H2O MO H2S ? M H2O
S MO H2S ? MS H2O M H2S ? MS H2
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TPS of MoO3/Al2O3
e
100 mg, 4.5 atoms/nm2 200 mg, 2.2 atoms/nm2 400
mg, 1.0 atoms/nm2 800 mg, 0.5 atoms/nm2 400 mg,
carrier
d
c
b
a
50 H2S conversion
0 20 40 400 600 800
1000 1200
Time (min) Temperature (K)
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TPS of MoO3/Al2O3
100 mg 4.5 atoms/nm2
H2
H2S
H2O
400 600 800 1000 1200
Temperature (K)
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Molecular Scheme of Sulphiding
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Modelling of TPR Patterns
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Kinetic Models for Reduction
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TPR of Fe2O3
H2/Ar saturated with 3 H2O
7.0 mg 15.9 mg 8.2 mg 3.6 mg
d
dry H2/Ar
c
b
a
500 600 700
Temperature (K)
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TPR of Fe2O3 as a Function of Heating Rate
10.0 K/min 0.08 mg
f
Dry H2/Ar
5.0 K/min 0.19 mg
e
2.0 K/min 0.91 mg
d
1.0 K/min 1.8 mg
c
b
0.5 K/min 2.8 mg
a
0.2 K/min 3.6 mg
500 600 700
Temperature (K)
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TPR of Fe2O3 as a Function of Heating Rate
f
10.0 K/min 0.17 mg
Wet H2/Ar (3 H2O)
5.0 K/min 0.33 mg
e
d
2.0 K/min 0.90 mg
1.0 K/min 1.5 mg
c
0.5 K/min 2.6 mg
b
0.2 K/min 7.0 mg
a
500 600 700 800
Temperature (K)
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Arrhenius Plots from TPR of Fe2O3
(K-1 s-1)
c
b
-15 -16 -17 -18 -19
a
dry series main peak
Ea 111 kJ/mol
wet series low T peak
wet series main peak
12 13 14 15
16 17 18
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Calculated Fe3O4 ? Fe TPR Peaks
three-dimensional nucleation (Avrami Erofeev)
f(?) 3(1-?) -ln(1-?)2/3
two-dimensional phase boundary f(?) (1-?)1/2
two-dimensional nucleation (Avrami Erofeev)
f(?) 2(1-?) -ln(1-?)1/2
three-dimensional phase boundary f(?) (1-?)2/3
unimolecular decay f(?) (1-?)
Three-dimensional diffusion (Jander) f(?)
3(1-?)2/3/2(1-(1-?)1/3)
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Comparison of Measured and Calculated Fe3O4 ? Fe
TPR Peaks
three-dimensional nucleation (Avrami Erofeev)
f(?) 3(1-?) -ln(1-?)2/3
calculated
Wet series
Dry series