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Catalyst 101
The basics of the sulphuric acid catalyst Presented by Lars Dam Raaby
Established 1940 Ownership: Haldor Topsøe Holding A/S
(100%) Annual turnover (2011): ~780 MM USD Number of employees ~2100
Fertiliser industry
Heavy chemical and petrochemical industries
Refining industry
Environmental and power sector
Topsøe Group’s headquarters in Lyngby, Denmark
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Dr. Haldor Topsøe (born 24 May 1913)
Agenda
The working principle of the
sulphuric acid catalyst
– Active phase
– Carrier
– Shape
Catalyst in real life
– Colours of the catalyst
– Pressure drop build-up
– Deactivation
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The sulphuric acid catalyst
The working principle
The sulphuric acid catalyst
Active melt
Carrier
Shape
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The carrier – diatomaceous earth
Active phase – the melt
Vanadium pentoxide + pyrosulphates
Pyrosulphate formation
M2SO4 + SO3 ↔ M2S2O7
(M = K, Na, Cs)
[(VVO)2O(SO4)44-]
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SO3
SO3
(V O) O(SO ) OV -4
2 4 4
2V OSO (s)IV
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(V O) O(SO ) SOV
2 4 4 3
-4
(V O) O(SO )V
2 4 4
-4
(V O) O(SO ) OV
2 4 4 2
-4
2V O(SO )IV
4 2
-2
2SO4
-2SO2
O2
2
1
3
4
SO2 SO3
SO2
Source: O.B. Lapina et al (1999). Catalysis Today, 469-479.
Mechanism of catalytic SO2 oxidation
VV is the active oxidation state
Effect of liquid loading on activity
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The sulphuric acid catalyst
SO2,O2
SO3
V2O5 promoted with alkali pyrosulphates on an inert SiO2 carrier
Supported liquid phase – SLP catalyst
Catalyst sizes and shapes
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Pressure drop
Theoretical pressure drop
Catalyst size Relative SA Void fraction
ε
deq (mm)
6 mm cylinder 130 0.38 11.3 6.5
10 mm ring 100 0.50 4.0 7.1
12 mm Daisy 100 0.55 2.7 6.2
20 mm ring 53 0.50 4.0 13
25 mm Daisy 52 0.55 2.7 12
3
11),,(
eqdvfP
3ε
ε1
Pressure drop – sizes and shapes
1000 1200 1400 1600 1800 2000 800
0
100
200
300
400
Gas velocity, Nm3/hr/m2
P, m
mW
C/m
be
d h
eig
ht
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The catalyst in real life
The catalyst in operation
Active melt
Carrier
Shape
Catalyst
colours
Pressure drop build-up
Deactivation
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Colours of the catalyst
The colours of vanadium
Vanadium exists in four oxidation
states
Every oxidation state has a
distinct color – here shown in
aqueous solution
V2+ V3+ V4+ V5+
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Catalyst exposed to reducing conditions
- could look something like this
or this…
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Raman spectrum at room temperature
Cooled in 10% SO2
1200 1100 1000 900 800 700 600
Raman shift, cm-1
Room temperature in 10% SO2
K4(VIVO)3(SO4)5
Counts
/s
1237 1197
1049
1020
1000
973
743
947
621 599 1123
1102 1074
Raman spectrum at 380°C
Switching from air to 10% SO2
1200 1100 1000 900 800 700 600
Raman shift, cm-1
380°C in air/10% SO2
MX(VO4)y polymer
Counts
/s
870
842
772
696
1200 1100 1000 900 800 700 600
Raman shift, cm-1
Counts
/s
(VIVO)3(SO4)54-
998
973
926
619
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Raman spectrum at 480°C in 10% SO2
1200 1100 1000 900 800 700 600
Raman shift, cm-1
480°C in 10% SO2
VVO2(SO4)23-
Counts
/s
1183
1045 983
960
942
788 664
605
844
(VVO)2O(SO4)44- /
Heat treatment of catalyst
Before heat treatment
After heat treatment
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Heat treatment of catalyst
Pressure drop build-up
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Pressure drop build-up
Does this look familiar?
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Dust protection – principle
Pressure drop build-up with
and without dust protection layer
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Operating time [months]
500
400
300
200
100
0 0 6 12 18 24
Rela
tive p
ressure
dro
p
High dust load
No dust protection
Top layer of 25 mm Daisy
+100%
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Industrial experience 1330 MTPD plant based on off-gas from Cu ores
0
200
400
600
800
1000
1200
5 10 15 20 25 30 35 40 0
Months
Before installation of
dust protection catalyst
After installation of 25 mm Daisy
dust protection catalyst
Pre
ssure
dro
p,
mm
WC
Catalyst deactivation
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Mechanical
– Dust covering surface
– Moisture/acid condensation
Chemical deactivation
– Typical As, F
Thermal deactivation
– Temperature > 630-650°C
– Irreversible degradation of the support
Catalyst deactivation
Temperature optimisation due to
catalyst deactivation
Temperature, °C
Convers
ion
Equilibrium curve
Catalyst activity
100
80
60
40
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Non-optimum inlet temperature to bed 4 – effect on SO2 emission
Inlet temperature to bed 4, °C
SO
2 e
mis
sio
n, ppm
~ 0.01 % SO3
~ 0.5 % SO3
440 420 400
500
300
200
100
400
450 430 410 390
What can we do?
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1944 1970 1984 1987
1988
1996
1998
VK38
First with
Rings
First with
Daisy
High-
Vanadium
VK48
First with
Caesium
VK58
Topsøe VK history in brief
1992
VK-WSA
2002
VK-WSX
2007 VK69
VK59 2nd Caesium
Generation
25 mm
2010
VK-701 LEAP5 2nd Caesium
Generation
VK38 and VK48 applications
Single absorption Double absorption
VK38
VK38
VK48
VK48
VK38
VK38
VK48
VK38
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VK59 and VK69 applications
Single absorption Double absorption
VK38
VK38
VK48
VK59
VK38
VK38
VK48
VK69
VK59
VK-701 LEAP5TM applications
Single absorption
VK38
VK38
VK48
VK-701
Double absorption
VK38
VK38
VK-701
VK69
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Case study Reduced emissions from a single-absorption plant
Layout : 4-pass single-absorption
SO2 source : Metallurgical off-gas
Feed gas : 8.0% SO2, 10.5% O2
Catalysts in beds 1/2/3 : VK38 / VK38 / VK48
Conversion outlet bed 3 : 96.7%
Production: 1000 MTPD
VK38
VK38
VK48
VK48 VK59 VK-701
Case study Reduced emissions from a single-absorption plant
Catalyst in bed 4, 55m3 VK48 VK59 VK-701 LEAP5
Inlet temperature, °C 430 420 420
Overall conversion, % 97.88 98.03 98.36
SO2 in the stack, ppm 1920 1780 1485
Relative SO2 emission 100 93 77
SO2 emission reduced by 17% compared to VK59
SO2 emission reduced by 23% compared to VK48
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Industrial experiense
VK38 – 25mmD Dust protection
– > 70 references (2007)
VK59
– > 130 refereces (1998)
VK69
– > 85 references (1996)
VK-701 LEAP5
– > 2 (+1) references (2010)
Summary
The sulphuric acid catalyst is made up by:
– active vanadium pyrosulphate melt
– inert sillica carrier
– optimised shape
Catalyst of strange colour due to the nature of vanadium
Pressure drop build-up can be delayed by using dust
protection catalyst
The nature of the catalyst results in slow deactivation
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Thank you