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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