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 0.319 671.0

1.75 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-02

653 0.7625 0.3037 1.692E-02

658 0.7597 0.3035 1.685E-02

668 0.7417 0.3028 1.644E-02

Overall ComparisonProperty Initial Design Final Design

Temperature (K) 658 653

Inlet Benzene (kmol/s) 0.02122 0.02684

Catalyst Weight (kg) 139,750 76,400

Reactor Length (m) 97.4 2.476

Diameter (m) 7.2 6.5

Volume (m3) 150 82.2

Potential Earnings ($/yr)

20,822,183 8,901,617

Pressure Drop 9.95%

Selectivity 0.3036

Coolant Gain 1.008

Inlet 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).

Questions and Comments?