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 Optimization
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 kmol/s
Original design: ideal/isobaric/isothermal
Final design: pressure drop, multiple reactions and heat effects
Optimized using selectivity and gain

4. Inlet Percent of Propylene (mol %) Inlet Percent of Air (mol %)
Process Background
Literature Operating Conditions (1,2)
Temperature (°C)
Pressure (atm)
Percent Conversion
Inlet Percent of Propylene (mol %)
Inlet Percent of Air (mol %)
1-3.4 85 2 98

5. Process Background Continued
Assumptions
Given for final design
Deviations for other models discussed
Parameter
Value
Particle Size
5 mm (3)
Bulk Density
1415 kg-cat/m3-rxtr (4)
Packed Bed Void Fraction
0.38 (4)
Tube Diameter
1 in. ( m)
Viscosity of Air at 390°C
3.15 x 10-5 kg/m-s (5)
Coolant Temperature
673K (390°C)
Overall Heat Transfer Coefficient
227 J/W-m2-K (3)

6. Process Background Continued
Stoichiometric Flow Rates
Inlet Compositions
Outlet Compositions
Mole (kmol/s)
Propylene
Oxygen
Inert Nitrogen
Acrolein
Water
Total

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
Units
350°C
375°C
390°C
ka, (kmol- m3)1/2/kgcat-s
±0.41
±1.33
±0.15
k12, m3/kgcat-s
2.19±0.14
3.86±0.37
5.38±0.35
k13, m3/kgcat-s
2.7±0.18
2.94±0.31
2.70±0.27
k14, m3/kgcat-s
0.273±0.21
0.452±0.55
0.628±0.71
Rate Constants
Pre-exponential Factor, A
Activation Energy, E (kJ/mol) ka
(kmol-m3)1/2/kgcat-s
k12
(m3/kgcat-s)
k13co2
(m3/kgcat-s)
k13co
(m3/kgcat-s)
k14
(m3/kgcat-s)

12. Design Process Reactor 1 Reactor 2 Reactor 3 Reactor 4 Volume
Pressure Drop
Mult. Reactions
Heat Effects
Volume (m3)
4174.6
22.51
19.19
Num. Tubes (1” Dia.)
N/A
683600
17920
16880
Reactor Dia. (m) 21
3.4
3.3
Reactor Len. (m)
12.05
2.4792
2.24
Cat. Weight (kg-cat)
3.07 x 107
5.91 x 106
31850
27150
Particle Size (mm) 3 5
Nitrogen Feed (kmol/s)
Oxygen Feed (kmol/s)
Propylene Feed (kmol/s)
Inlet Temp. (°C)
350
390
Inlet Pressure (atm) 1
Pressure Drop (%)
0.37
7.97
7.82
Acrolein Prod. (kmol/s)
Propylene Conversion (%)
85.13
85.02
84.99
85.01

13. Optimization Acrolein Selectivity Other Usable Product 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 Reactor Configurations
Temperature- 390°C
Pressure- 3 atm
Reactor Configurations
Volume m3
Diameter- 3.4 m
Length m
Number of Tubes (1” Dia.)

16. Final Design Continued
Inlet Flows (kmol/s)
Polymath Outlet (kmol/s)
Aspen Plus ® Outlet (kmol/s)
Nitrogen
Oxygen
Propylene
Acrolein
Acetyldehyde
Carbon Monoxide
Carbon Dioxide
Water
Total
Pressure (Pa)
303975
284200
284080
Temperature (K)
663

17. Final Design Continued
Polymath
Aspen Plus ®
Pressure Drop
6.59 %
6.54 %
Conversion
85.05 %
85.17 %
Selectivity of Acrolein
1.71
Selectivity of Others
0.48
Hot Spot Temperature °C °C
Hot Spot. Location
0.18 m
0.21 m
Gain
1.16
1.17

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 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 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.
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