Flowsheets Catalysts Catalyst Deactivation

1. Theory and Operation of
Methanol Synthesis
Gerard B. Hawkins
Managing Director, CEO

2. Introduction
 Flowsheets
 Catalysts
 Catalyst Deactivation

3. Methanol Flowsheet

4. Methanol Flowsheet
Natural
Gas
Sulphur
Removal Saturator
Reforming
Air
Condensate
Compression
BFW
Demin
Water
CW
CW
Synthesis
Distillation
MP
Steam
Purge to
Fuel
Crude
Methanol
Product
Methanol
Fusel
Oil
Refining Column
Bottoms
HP
Steam

5. Methanol Synthesis Reactions
 Purpose of synthesis loop is to convert H2, CO
and CO2 to methanol
CO + 2H2  CH3OH ∆H = - 90.64 kJ/kmol
CO + H2O  CO2 + H2 ∆H = - 41.17
kJ/kmol
 Both reactions are revisible and exothermic
 Combine to give
CO2 + 3H2  CH3OH + H2O ∆H = - 49.74
kJ/kmol

6. Methanol Synthesis Reactions
 Methanol is produced from CO2
 Proven by use of radioactive C14
 CO is shifted to CO2 and then to
methanol
 Rate of reaction is given by
5.0
2
2]./[3
][
][
.exp.
OHP
COP
Activity
dt
OHdCH TRE∆−
∝

7. Equilibrium
 Equilibrium defined by
 Which can be rearranged to
 Which is far more useful
[ ] [ ]
[ ] [ ]3
22
23
.
.
HPCOP
OHPOHCHP
Kp =
[ ]
[ ] [ ]3
22
2
3
.
][.
HPCOP
OHPKp
OHCHP =

8. Effect of Temperature on Kp

9. Effect of Temperature on
CH3OH %

10. Effect of Pressure on CH3OH %

11. Definition of ATE

12. Effect of Operating Parameters on
Equilibrium and Kinetics
 For good conversion need following
conditions
Parameter Equilibrium Kinetics
Temperature Low High
Pressure High High
Catalyst Activity High High
So there is a conflict for temperature

13. Effect of Operating Temperature
on Equilibrium and Kinetics

14. Concept of Maximum Rate Line
 If reaction follows the max rate line then
minimum catalyst volume for maximum
production

15. Methanol Synthesis Catalyst VSG-M101
 Available as
• VSG-M101
 Synthesis of methanol
• from mixtures of CO, CO2 and H2
 Copper on a ZnO-Al2O3 support
 Proprietary metal oxides are added to
prevent sintering and improve dispersion of
copper crystallites

16. Methanol Synthesis Catalyst
History
 Over 30 years manufacturing
experience
 45,000+ m³ of methanol synthesis
catalyst made
 4,000 m³ of VSG-M101series
catalyst currently installed in PRC

17. Methanol Synthesis Catalyst
Properties
 Effect Property
 Activity - Copper surface area
 Life - Microstructure
 Strength - Macrostructure
 Selectivity - Formulation

18. Methanol Synthesis Catalyst
Properties
 Typical composition for VSG-M101
• CuO 64 wt%
• Al2O3 10 wt%
• ZnO 24 wt%

19. Methanol Synthesis Catalyst
Properties
 Spherical Pellet
• Diameter 5 mm
• Height 4 - 5 mm
 Bulk density 1,400 - 1,600 kg/m³
 Radial crush strength >205N/m

20. Methanol Synthesis Catalyst Poisons
 Poison
 Sulfur
 Chlorine
 Iron
 Elemental Carbon
 Metals e.g. V, K, Na
 Nickel
 Ammonia
 HCN
 Oxygen
 Ethene
 Ethyne
 Particulates
 Effect & Limit
 Activity, 0.20% mass
 Activity, 0.02% mass
 0.15% mass
 Absent
 Selectivity, Absent
 Selectivity, 0.04% mass
 TMA, 10 ppmv
 Amines, Absent
 Activity, 1000 ppm
 20 ppmv
 5 ppmv
 Absent
ppmv figures refer to MUG composition.
% mass figures refer to accumulation on catalyst.

21. Relationship of Copper Surface Area and
Activity
0 10 20 30 40
0
0.2
0.4
0.6
0.8
1
1.2
Copper Surface Area m2/gram
Activity
Copper
Surface Area

22. VSG-M101Properties
 As noted before,
• Catalyst deactivation is caused by thermal
sintering
• Copper crystallites grow - the surface area
falls
 It also improves the catalyst's ability to
maintain the separation of crystallites with
time
• This prevents sintering and so activity is more
stable

23. Catalyst Deactivation
 Either by
• Sintering
• Poisoning from
 Sulfur
 Chlorides
 Carbonyls

24. Thermal Sintering
 Historically always believed to be due to
thermal sintering
 But also reactant and carbonyl poisoning
 Thermal sintering of copper catalysts is
unavoidable
 Rate is critically dependent on temperature
• Therefore the hotter the catalyst the faster the rate
of deactivation
• Operation at low temperatures reduces activity loss
due to sintering
 Rate of sintering slows as the catalyst ages

25. What Causes Thermal Sintering
?
 Hence activity rules reflected this by
defining activities by temperature bands
 Also defined activities by converter type
• This does include a temperature effect
• Also effect of gas mal distribution
• For example cold cores in Quench
Lozenge converters

26. How does catalyst deactivate ?
CuCu
Cu
Cu
Cu
CuCu
Cu
Cu
Cu
Cu
Cu Cu
• Thermal sintering
–Cu molecules migrate and join other Cu particles to
make bigger particles but with a smaller surface area

27. Sulfur Poisoning
 Sulfur is a powerful poison for Cu/Zn catalysts
 The ZnO component provides a sink for sulfur
by formation of ZnS
 An effective catalyst requires an intimate
mixture of Cu and ZnO and a high free ZnO
surface area

28. Chloride Poisoning
 Chloride reacts with copper to form CuCl
(mp = 430oC)
 CuCl provides a mechanism for loss of
activity by sintering
 Catalyst requires well dispersed and
stabilized copper to minimize the effects
of chloride poisoning

29. Catalyst Deactivation Model
0.175
0.275
0.375
0.475
0.575
0 12 24 36 48
Time Months
Activity
High Temperature
Operation
Low Temperature
Operation

30. What Causes Deactivation ?
 Now looking at the effect of Iron and
Nickel Carbonyls
 Seen some high levels 5,000 ppm on
discharged catalyst samples
 Looking at the most effective guard
beds
 Could be worth 10 % extra on activity
 Consider the above to be confidential

31. Copper Surface Area’s of Catalyst
0
1
Activity
Comp A Comp A2 Comp B
Comp C Comp C2 VSG-M101
1.80

32. Activity of VSG-M101
Time on line (months)
0 2 4 6 8 10
0.0
0.1
0.2
0.3
0.4
Relativeactivity
0.5
VULCAN VSG-M101
VULCAN VSG-M101D
0.6
0.7
0.8
0.9

33. Converter Types
 Many different converter types
• Tube Cooled
• Quench Lozenge; ARC and CMD
• Steam raising
 Aim is the same
• Keep process gas cool
• Contain the catalyst
• Maximize reaction rate

34. Loop Design
 Very similar not matter what type of
converter

35. Quench Type Converters
 Original – very simple mechanical design not the
most efficient
 Replaced with slightly more complex design which
is more efficient (better mixing)
ARC Converter
Quench Converter

36. Tube Cooled Converters
 Very simple design which integrates
catalyst and process gas preheat
 Allows for heat recovery into
saturator circuit
TCC Design

37. Steam Raising
 Many types
 Recover heat to steam
 Tracks max rate line closely
 Each has own Pro’s and Con’s
Linde Variobar
Toyo MRF
Lurgi SRC

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