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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
Catalysis and Catalysts - TPR and TPS
Examples of TPR
Reduction of oxidic species:
MO + H2
M + H2O
Study of coke deposits:
coke + H2
hydrocarbons + H2O
Reduction of sulphides:
MS + H2
Catalysis and Catalysts - TPR and TPS
M + H2S
G0 (kJ/mol)
Thermodynamics
Catalysis and Catalysts - TPR and TPS
T (K)
Equipment for TPR
reactor
H2/Ar
molsieve
FID
TCD
Catalysis and Catalysts - TPR and TPS
TPR of 9.1 wt% CoO/Al2O3
400
800
1200
Temperature (K)
Catalysis and Catalysts - TPR and TPS
e
j
o
d
i
n
c
h
m
b
g
l
a
f
k
400
800
1200
Temperature (K)
400
800
1200
Temperature (K)
TPR Patterns of Reference Materials
TCD
CoAl2O4
FID
Co3O4
CoO
400
800 1200
Temperature (K)
Catalysis and Catalysts - TPR and TPS
Influence of ‘hard’ and ‘soft’ Ions
CoMoO4
CoAl2O4
Co3O4
400
Catalysis and Catalysts - TPR and TPS
800
1200
Temperature (K)
TPS of MoO3/Al2O3
Reactions:
MO + H2

M + H2 O
MO + H2S

M + H2O + S
MO + H2S

MS + H2O
M + H2S

MS + H2
Catalysis and Catalysts - TPR and TPS
TPS of MoO3/Al2O3
e
100 mg, 4.5 atoms/nm2
d
200 mg, 2.2 atoms/nm2
pH2S
c
400 mg, 1.0 atoms/nm2
b
800 mg, 0.5
atoms/nm2
a
400 mg, carrier
50% H2S conversion
Catalysis and Catalysts - TPR and TPS
0
20
40
Time (min)
400
600
800 1000 1200
Temperature (K)
TPS of MoO3/Al2O3
100 mg
4.5 atoms/nm2
H2
pH 2
pH2S
H2S
H2O
pH2O
400
Catalysis and Catalysts - TPR and TPS
600 800 1000 1200
Temperature (K)
Molecular Scheme of Sulphiding
O
O
+ H2S
Mo
O
Al
- H2O
O
Al
O
S
Mo
O
Al
I
O
+ H2S
- H2O
Al
S
Mo
O
Al
O
+ H2S
Mo
O
Al
O
Al
V
Catalysis and Catalysts - TPR and TPS
- H2O
Al
S
- H2O
S
Mo
O
Al
S
Al
IV
-S
-S
- H2O
O
+ H2S
III
II
+ H2
S
S
+ H2S
Mo
O
Al
O
Al
VI
-S
- H2O
S
Mo
O
Al
S
Al
VII
Modelling of TPR Patterns
Catalysis and Catalysts - TPR and TPS
Kinetic Models for Reduction
Model
nth Order
f()
(1-)n
g()
(1-(1-)1-n)/(1-n)
Random nucleation
Unimolecular decay law
(1-)
-ln(1-)
Phase boundary controlled reaction
(contracting area)
(1-)1/2
2(1-(1-)1/2)
Phase boundary controlled reaction
(controlled volume)
(1-)2/3
3(1-(1-)1/3)
Two dimensional growth of nuclei 2(1-)[-ln(1-)]1/2
(Avrami-Erofeev)
[-ln(1-)]1/2
Three dimensional growth of nuclei 3(1-)[-ln(1-)]2/3
(Avrami-Erofeev)
[-ln(1-)]1/3
One dimensional diffusion
Parabolic law
1/2
2
-1/ln(1-)
(1-)ln(1-) + 
Three dimensional diffusion
(Jander)
[3(1-)2/3]/ [2(1-(1-)1/3)]
[1-(1-)1/3]2
Three dimensional diffusion
(Ginstling-Brounshtein)
3/[2((1-)-1/3 -1)]
1-2/3 - (1-)2/3
Two dimensional diffusion
Catalysis and Catalysts - TPR and TPS
Catalysis and Catalysts - TPR and TPS
TPR of Fe2O3
H2/Ar saturated
with 3% H2O
7.0 mg
d
dry H2/Ar
15.9 mg
c
8.2 mg
b
3.6 mg
a
500
Catalysis and Catalysts - TPR and TPS
600
Temperature (K)
700
TPR of Fe2O3 as a Function of Heating Rate
Dry H2/Ar
500
600
Temperature (K)
Catalysis and Catalysts - TPR and TPS
700
f
10.0 K/min
0.08 mg
e
5.0 K/min
0.19 mg
d
2.0 K/min
0.91 mg
c
1.0 K/min
1.8 mg
b
0.5 K/min
2.8 mg
a
0.2 K/min
3.6 mg
TPR of Fe2O3 as a Function of Heating Rate
f
10.0 K/min
0.17 mg
e
5.0 K/min
0.33 mg
d
2.0 K/min
0.90 mg
c
1.0 K/min
1.5 mg
b
0.5 K/min
2.6 mg
a
0.2 K/min
7.0 mg
Wet H2/Ar
(3% H2O)
500
Catalysis and Catalysts - TPR and TPS
600
700
Temperature (K)
800
Arrhenius Plots from TPR of Fe2O3
 β
ln 2
 Tmax

 (K-1 s-1)

b
c
a
-15
-16
dry series
main peak
-17
Ea = 111 kJ/mol
wet series
low T peak
wet series
main peak
-18
-19
12
13
14
15
1
Tmax
Catalysis and Catalysts - TPR and TPS
16
(10-4 K-1)
17
18
Calculated Fe3O4  Fe TPR Peaks
dα
(10-2 K-1)
dT
a
4
two-dimensional
phase boundary;
f() = (1-)1/2
3
three-dimensional
phase boundary;
f() = (1-)2/3
2
b
three-dimensional nucleation
(Avrami Erofeev);
f() = 3(1-) [-ln(1-)]2/3
two-dimensional nucleation
(Avrami Erofeev);
f() = 2(1-) [-ln(1-)]1/2
c
d
e
unimolecular decay;
f() = (1-)
f
1
Three-dimensional diffusion
(Jander);
f() = [3(1-)2/3]/[2(1-(1-)1/3)]
0
500
550
600
Temperature (K)
Catalysis and Catalysts - TPR and TPS
650
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
a
b
500
550
600
Temperature (K)
Catalysis and Catalysts - TPR and TPS
650