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![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∆−
∝](https://image.slidesharecdn.com/methanolsynthesis-theoryandoperation-130730212230-phpapp02/75/Methanol-Synthesis-Theory-and-Operation-6-2048.jpg)
![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 =](https://image.slidesharecdn.com/methanolsynthesis-theoryandoperation-130730212230-phpapp02/75/Methanol-Synthesis-Theory-and-Operation-7-2048.jpg)
Uploaded byGerard B. Hawkins
Methanol Synthesis - Theory and Operation
This document summarizes the theory and operation of methanol synthesis. It describes the typical methanol synthesis flowsheet that involves natural gas processing, reforming, and methanol production and purification steps. It also discusses the methanol synthesis reactions, catalysts used including their properties and deactivation mechanisms. Key factors that affect the equilibrium and kinetics of the synthesis reactions like temperature, pressure and catalyst activity are described. Methods to maximize the reaction rate within operational constraints are covered.
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Methanol Synthesis - Theory and Operation
- 1. Theory and Operationof Methanol Synthesis Gerard B. Hawkins Managing Director, CEO
- 2. Introduction Flowsheets Catalysts Catalyst Deactivation
- 3.
- 4. Methanol Flowsheet Natural Gas Sulphur Removal Saturator Reforming Air Condensate Compression BFW Demin Water CW CW Synthesis Distillation MP Steam Purgeto 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 definedby Which can be rearranged to Which is far more useful [ ] [ ] [ ] [ ]3 22 23 . . HPCOP OHPOHCHP Kp = [ ] [ ] [ ]3 22 2 3 . ][. HPCOP OHPKp OHCHP =
- 8.
- 9. Effect of Temperatureon CH3OH %
- 10. Effect of Pressureon CH3OH %
- 11.
- 12. Effect of OperatingParameters 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 OperatingTemperature on Equilibrium and Kinetics
- 14. Concept of MaximumRate Line If reaction follows the max rate line then minimum catalyst volume for maximum production
- 15. Methanol Synthesis CatalystVSG-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 CatalystPoisons 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 CopperSurface 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 notedbefore, • 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 Eitherby • Sintering • Poisoning from Sulfur Chlorides Carbonyls
- 24. Thermal Sintering Historicallyalways 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 ThermalSintering ? 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 catalystdeactivate ? 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 Sulfuris 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 Chloridereacts 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 0.575 012 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’sof Catalyst 0 1 Activity Comp A Comp A2 Comp B Comp C Comp C2 VSG-M101 1.80
- 32. Activity of VSG-M101 Timeon 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 Manydifferent 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 Verysimilar 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 Manytypes Recover heat to steam Tracks max rate line closely Each has own Pro’s and Con’s Linde Variobar Toyo MRF Lurgi SRC
- 38. Process Information Disclaimer Informationcontained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss or damage resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.