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Partial Oxidation of Benzene to Maleic AnhydrideDerek BechtMike RaymondEric NetteMatt Hunnemeder
Overview• Project Description
• Background
• Assumptions
• Solution Methodology
• Final Design
• Overall Comparison
Project Description•Reaction: Partial oxidation of benzene
•Reactor: Fixed bed reactor
•Production: 50000 M tons/year maleic anhydride
•Step by step modeling process
Fogler H.S. Elements of Chemical Reaction Engineering; Pearson Education: New Jersey, 2006.
Maleic Anhydride
Feed stocks1
Benzene
N-Butene
N-Butane
Major Uses2
Resins
Oil Additives
Copolymers
Financial Considerations•Market Price3,4
▫Maleic Anhydride: $1.54/kg - $ 1.70/kg
▫Benzene: $929.99/m3 – $940.55/m3
•Financial Earnings▫$20,922,183/yr neglecting all cost, except
feed
Standard Assumptions• Open system + steady state
• Negligible potential and kinetic energy
• No mechanical or shaft work
• Turbulent flow▫Uniform temperature, pressure, and
concentration within the control volume
• 2 weeks downtime
Benzene Specific Assumptions•1.1 mol % inlet benzene5
•Conversion, XB, is 0.76 6
•Dry air
•Negligible CO2 in airA. Bielanski, M. N. (1997). V2O5-MoO3 Catalysts for Benzene Oxidation. Applied catalysts , 223-261.
Reactor and Particle Properties•Bulk Density7 = 930 kgcat/m3
•V2O5-MoO3 Particle Diameter8 = 0.006m
•Void Fraction = 0.4 m3gas/m3
rxtr
•Heat Transfer Coefficient8 = 202.4 W/m2-K
•Coolant Temperature8 = 653 K
Solution Methodology•Ideal Reactor -> Realistic Reactor
•Considerations:▫Pressure drop
▫Side reactions
▫Temperature rise/drop
Case 1: Ideal Reactor•Assumptions Reaction Kinetics
▫Isothermal▫One reaction▫Isobaric
•Inlet Conditions Feed Rates▫658 K Benzene: 0.02122 kmol/s▫1.5 atm Oxygen: 0.4177 kmol/s▫1.1 mol% benzene Nitrogen: 1.577 kmol/s
Conversion Profile
Heat Duty Profile
Case 2: Pressure Drop• Additional Assumptions Momentum
Equations▫ Ideal Gas
▫ Constant Density
• Additional Property▫ Viscosity9 = 3.2197E-5 PaS
Conversion Profile
Particle Diameter
Case 3: Multiple Reactions•Mechanism Rate
Expressions
2 C6H6 + 6 O2 -> 3 C4H2O3 + 3 H2O
C6H6 + 6 O2 -> 3 CO + 3 CO2 + 3 H2O
Molar Flow Rates
Selectivity
Case 4: Energy Balance•Additional Assumptions
▫Constant heat capacity
▫Constant coolant temperature
▫Multi-tube reactor
Coolant Temperature
Inlet Temperature
Final Design: Optimization•Pressure
•Temperature
Pressure (bar)
Conversion
Pressure Drop %
Selectivity
Hot Spot (K)
1.5 0.764 9.33 0.319 671.01.75 0.823 7.95 0.313 674.0
2 0.867 6.93 0.308 676.9
Inlet Temperature
(K)Conversion Selectivity
Flow Maleic Anhydride (kmol/s)
648 0.7598 0.3036 1.686E-02653 0.7625 0.3037 1.692E-02658 0.7597 0.3035 1.685E-02668 0.7417 0.3028 1.644E-02
Overall ComparisonProperty Initial Design Final Design
Temperature (K) 658 653Inlet Benzene (kmol/s) 0.02122 0.02684Catalyst Weight (kg) 139,750 76,400Reactor Length (m) 97.4 2.476
Diameter (m) 7.2 6.5Volume (m3) 150 82.2
Potential Earnings ($/yr)
20,822,183 8,901,617
Pressure Drop 9.95%Selectivity 0.3036
Coolant Gain 1.008Inlet Gain 0.051
References1) Barone et al., United States Patent 4018709. Patent Issued 1977.
2) Maleic anhydride - Chemical Profile. <http://www.the-innovation-group.com/ChemProfiles/Maleic%20Anhydride.htm>. (accessed 01/24/2008).
3) William Lemos. US Price Report – Maleic Anhydride. <http://www.icis.com/v2/chemicals/9076024/maleic-anhydride/pricing>. (accessed 01/25/2008).
4) Americas Market Summary – Benzene. http://www.icis.com/articles/2008/01/29/9096633/NOON-SNAPSHOT. (accessed 01/24/2008).
5) Sharma R.K. et al. (1984). Selective Oxidation of Benzene to maleic anhydride at Commercially Relevant Conditions. Institution of Chemical Engineers Symposium Series, 353-360.
6) Americas Market Summary – Benzene. http://www.icis.com/articles/2008/01/29/9096633/NOON-SNAPSHOT. (accessed 01/24/2008).
7) U.S. Patents. (1996). Oxide catalyst and process for producing maleic anhydride by oxide catalyst (No. 266510 filed on 1994-06-27).
8) U.S. Patents. (1978). Process for the Manufacture of Maleic Anhydride (No. 4070379 filed on 10/21/1976). http://www.freepatentsonline.com/4070379.html
9) Chemical Database Property Constants. DIPPR Database [Online]. Available from Rowan Hall 3rd Floor Computer Lab. (Accessed on 1/24/2008).
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