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Partial Oxidation of Propylene to Acrolein

Partial Oxidation of Propylene to Acrolein

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Partial Oxidation of Propylene to Acrolein

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  1. Partial Oxidation of Propylene to Acrolein Final Design Presentation April 23, 2008 Kerri M. May Megerle L. Scherholz Christopher M. Watts

  2. Overview • Introduction • Process Background • Design Process • Determination of Volume • Pressure Drop • Multiple Reactions • Heat Effects • Optimization • Final Design • Conclusion

  3. Introduction • Design of fixed-bed reactor • Production of acrolein by partial oxidation • CH2 = CH - CH3 + O2 → CH2 = CH – CHO + H2O • 13,500 Mtons/year with a 2 week downtime • Corresponds to 0.007941 kmol/s • Original design: ideal/isobaric/isothermal • Final design: pressure drop, multiple reactions and heat effects • Optimized using selectivity and gain

  4. Process Background • Literature Operating Conditions (1,2)

  5. Process Background Continued • Assumptions • Given for final design • Deviations for other models discussed

  6. Process Background Continued • Stoichiometric Flow Rates

  7. Process Background Continued • Catalyst chosen based on kinetics • Bismuth molybdate (6) • Co-current Heat Exchanger Fluid • Exothermic reaction • Molten Salt used as coolant fluid • Sodium tetrasulfide (7) • Melting temperature (294°C)

  8. Process Background Continued • Selectivity of Acrolein • Selectivity of Other Profitable Products • Gain

  9. Process Background Continued • Reaction Kinetics of Byproducts (6,8) • Reaction Pathway • Assumptions: • Steady State • Single-site oxygen adsorption • Rate of oxidation of acrolein to carbon oxides is negligible compared to other rates

  10. Process Background Continued • Reaction rates for the formation of acrolein and byproducts (6,8) Where: r2 = rate of formation of acrolein, kmol/kgcat-s r3co2 = rate of formation of carbon dioxide, kmol/kgcat-s r3co = rate of formation of carbon monoxide, kmol/kgcat-s r4 = rate of formation of acetaldehyde, kmol/kgcat-s s ka = rate constant for oxygen adsorption, (kmol-m3)1/2/kgcat-s k12 = rate constant for propylene reaction to acrolein, m3/kgcat-s k13co2 = rate constant for propylene reaction to carbon dioxides, m3/kgcat-s k13co = rate constant for propylene reaction to carbon monoxide, m3/kgcat-s k14 = rate constant for propylene reaction acetaldehyde, m3/kgcat-s Co = concentration of oxygen, kmol/m3 Cp = concentration of propylene, kmol/m3 n12 = number of moles of oxygen which react with one mole of propylene to produce acrolein, kmol/kmol n13co2 = number of moles oxygen which react with one mole of propylene to product carbon dioxide, kmol/kmol n13co = number of moles of oxygen which react with one mole of propylene to produce carbon monoxide, kmol/kmol n14 = number of moles of oxygen which react with one mole of propylene to produce acetaldehyde, kmol/kmol

  11. Process Background Continued • Rate Constants at 325, 350, and 390°C • Pre-exponential Factors and Activation Energies

  12. Design Process

  13. Optimization • Acrolein Selectivity • Greater at increased temperatures • Improved when coolant and inlet temperatures are equal • Higher pressure, higher selectivity • Other Usable Product Selectivity • Decreased at increased temperatures • Favored at lower pressures • Greater when coolant temperature less than the inlet temperature

  14. Optimization Continued • Gain • Greater at increased inlet temperature • Independent of coolant and inlet temperature relationship • Optimization Conclusion: • Focus on selectivity opposed to gain

  15. Final Design • Operating Conditions • Temperature- 390°C • Pressure- 3 atm • Reactor Configurations • Volume- 19.08 m3 • Diameter- 3.4 m • Length- 2.01 m • Number of Tubes- 17920 (1” Dia.)

  16. Final Design Continued

  17. Final Design Continued

  18. Final Design Continued • Temperature Profile

  19. Conclusions • Reactor volume decreased with complexity increase • Selectivity crucial to optimization • Final model discussed would operate viably • Changed reactor dimensions to optimize final design

  20. Questions?

  21. Works Cited • Maganlal, Rashmikant, et al. Vapor phase oxidation of propylene to acrolein. 6437193 United States, August 20, 2002. • Chemical Database Property Constants. DIPPR Database [Online]. Available from Rowan Hall 3rd Floor Computer Lab. (Accessed on 1/24/2008). • LaMarca, Concetta, PhD. Chemical Reaction Engineering Design Project. February 2008. Chemical Engineering Department, Rowan University, Glassboro. • Transient Kinetics from the TAP Reactor System: Application to the Oxidation of Propylene to Acrolein. Creten, Glenn, Lafyatis, David S., and Froment, Gilbert F. Belgium: Journal of Catalysis, 1994, Vol. 154. • Chemical Database Property Constants. DIPPR Database [Online]. Available from Rowan Hall 3rd Floor Computer Lab. (Accessed on 1/24/2008). • The reaction network for the oxidation of propylene over a bismuth molybdate catalyst. Tan, H. S., Downie, J. and Bacon, D. W. Kingston : The Canadian Journal of Chemical Engineering, 1989, Vol. 67 • Physical Properties Data Compilations Relevant to Energy Storage.  II. Molten Salts:  Data on Single and Multi-Component Salt Systems.  G.J. Janz, C.B. Allen, N.P. Bansal, R.M. Murphy, and R.P.T. Tomkins Molten Salts Data Center, Rensselaer Polytechnic Institute, NSRDS-NBS61-II, April 1979 • The kinetics of the oxidation of propylene over a bismuth molybdate catalyst. Tan, H. S., Downie, J. and Bacon, D. W. Kingston : The Canadian Journal of Chemical Engineering, 1988, Vol. 66