CO2 + 3H2 = CH3OH + H2O What is used as a catalyst in this equation. ?
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Answer:
1. Gerard B. Hawkins Managing Director, CEO
2. • Reactions • Equilibrium • Catalyst Activity • Byproducts
3. Key synthesis reaction is CO2 + 3H2 <=> CH3OH +H2O Heat of reaction is -49 kJ/kmol Equilibrium reaction Also Water Gas Shift Reaction
4. WGS reaction is CO + H2O <=> CO2 + H2 Heat of reaction is -41 kJ/kmol Equilibrium reaction This combines with the methanol synthesis reaction to convert CO to methanol CO +2H2 <=> CH3OH
5. The reaction rate is defined by the following equation −= 1 3 22 3 22 3 1 KHPCOP OHCHP HPCOPkp dt OHCHd mn .][].[ ][ .][.][. ][ Where P[] is the partial pressure Kinetic Term Equilibrium Term
6. Due to water gas shift reaction can also have this equation in terms of CO Powers for this equation are ◦ n is 0.5 ◦ m is 1.5 ◦ This is from one source ◦ Other sources have different powers Our belief is methanol is produced from CO2
7. The reaction rate is defined by the following equation −= 1 2 2 3 2 3 .][].[ ][ 1.][.][. ][ KHPCOP OHCHP HPCOPkp dt OHCHd mn Where P[] is the partial pressure Kinetic Term Equilibrium Term
8. Catalysis in action High science at the atomic level
9. 150 200 250 300 350 400 450 0.000001 0.00001 0.0001 0.001 0.01 0.1 1 Temperature (°C) Kp-EquilibriumConstant 1 bara 100 bara 200 bara As can be seen pressure has a large effect Note Y axis is a log scale
10. ML % mol Catalyst Volume Increasing Pressure
11. Increasing Temperature ML % mol Catalyst Volume Equilibrium Lines
12. 180 200 220 240 260 280 300 320 0 2 4 6 8 10 12 14 Temperature (°C) RelativeRate Kinetically Limited Equilibrium Limited Maximum Rate
13. Maximum rate line is where the maximum methanol reaction rate occurs. By following this line, the minimum catalyst volume will be achieved for a given duty Therefore should try and ensure reaction path follows this line closely Each type of converter tracks this line in a particular way
14. MethanolConcentration(mol-%) Equilibrium line Temperature (°C) Max Rate Line
15. MethanolConcentration(mol-%) Equilibrium line Temperature (°C) Want to be here !
16. 180 200 220 240 260 280 300 320 0 2 4 6 8 10 Temperature (°C) MethanolConcentration(mol%) Max Rate Curve Methanol Equilibrium
17. 180 200 220 240 260 280 300 320 0 2 4 6 8 10 Temperature (°C) MethanolConcentration(mol%) Max Rate Curve Methanol Equilibrium
18. Also some side reactions The following species are produced ◦ Alcohol's - Ethanol, propanol, butanol & pentanol ◦ Ketones - Acetone, Methyl Ethyl Ketone etc. ◦ Formates - Methyl Formate ◦ Ethers - Di Methyl Ether (DME) ◦ Acetates - Methyl Acetates ◦ Hydrocarbons Methane C2-C9's Parrafinic Waxes C10 +
19. By product reactions are as follows ◦ Ethanol : 2 CH3OH + H2 <===> CH3-CH2OH + H2O ◦ Acetone : CH3-CHOHCH3 <===> CH3-CO- CH3 + H2 ◦ DME : 2 CH3OH <===> CH3-O-CH3 + H2O ◦ Methane : CO + 3H2 <===> CH4 + H2O
20. Exothermicity ◦ Methanol is thermodynamically less stable than other possible by-products ◦ Highlighted by heats of reaction Free Energy of Formation ◦ Methanol is thermodynamically less likely to be formed than other possible products ◦ Highlighted by free energy of formation
21. Crude production rates Converter space velocity Converter temperatures Gas compositions, CO and H2 mainly Catalyst impurities Oil leaks
22. Ethanol favored by ◦ high temperatures and CO partial pressures ◦ high levels of sodium ions ◦ high levels of active iron Higher alcohols are ◦ Limited by kinetic formation rate ◦ A function of CO/H2 ratio Exit Bed Temp °C 280 300 315 Ethanol 0.21% 0.447% 0.62%
23. Ketones dependent on temperature ◦ Acetone is a key light which must be removed in the Topping column ◦ MEK is virtually impossible to remove by distillation and will end up in the product Methyl Formate is equilibrium limited ◦ Little variation with temperature ◦ Easier to top than acetone. DME is equilibrium limited ◦ Very volatile and easy to remove in the topping column Methane favored by high temperatures and high levels of active iron
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