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Reactor Design Project synthesis of Maleic Anhydride through Partial Oxidation of n-butane

Chemical Reaction Engineering Dr. Robert P. Hesketh Dr. Concetta LaMarca. Yousef Ghotok Joseph Havelin Wednesday, 23 rd April 2008. Reactor Design Project synthesis of Maleic Anhydride through Partial Oxidation of n-butane. Outline.

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Reactor Design Project synthesis of Maleic Anhydride through Partial Oxidation of n-butane

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  1. Chemical Reaction Engineering Dr. Robert P. Hesketh Dr. ConcettaLaMarca YousefGhotok Joseph Havelin Wednesday, 23rd April 2008 Reactor Design Projectsynthesis of Maleic Anhydride through Partial Oxidation of n-butane

  2. Outline • Background, Process Reactions, and Rate Expressions • Initial Calculations • Case I  Reactor Volume Using Simple Reaction Rate Expression • Case II Pressure Drop and Reactor Configuration • Case III Multiple Reactions • Case IV  Energy Balance for Multiple Reactions • Case V Optimization of Reactor Design

  3. Background, Process Reactions, and Rate Expressions • Maleic anhydride is a cyclic organic chemical with formula C4H2O3. • Primary Use: Synthesis of Unsaturated Polyester Resins • N-butane is the most common feedstock used in production of maleic anhydride. • Bergman and Frisch discovered synthesizing maleic anhydride from n-butane by catalyzing the oxidation reaction. • By 1985, all commercial producers of maleic anhydride in the US used n-butane as their feed. • Worldwide Production: 1,359,000 tons per year • US Production: 273,800 tons per year

  4. Background, Process Reactions, and Rate Expressions • The partial oxidation of n-butane at the surface of the catalyst produces maleic anhydride and water, and side reactions produce carbon monoxide, carbon dioxide and water. • Catalyst used is vanadium-phosphorus oxide ((VO)2P2O7). • Reactor Type  Fixed-Bed Reactor • Advantages: easy use and low maintenance demand • Disadvantages: hot spots and pockets of diluted butane

  5. Background, Process Reactions, and Rate Expressions • Balanced Stoichiometric Equation:Cases I and II • C4H10 + 3.5O2 → C4H2O3 + 4H2O • Rate Equation: Cases I and II • rM= k1 · CB • Pseudo-First Order Rate Constant: Cases I and II • k1 = 8.1048 · 106 exp(-15649/T) [m3/kgcat-sec] • Reactions From the Oxidation of N-Butane: Cases III, IV, and V

  6. Background, Process Reactions, and Rate Expressions • Reaction Pathway Diagram: Cases III, IV and V • Reaction Rate Expressions: Cases III, IV and V Rate Constants and Parameters

  7. Initial Calculations • Assumptions: • Open system at steady state • Negligible changes in kinetic and potential energy • Negligible work • 14 days’ worth of downtime per year • Inlet gas 1.7 mol% n-butane • 80% conversion rate; side reactions not considered in this preliminary stage • 25,000 tons/year production rate • Reference temperature = 25 ºC = 298 K

  8. Initial Calculations • Stoichiometric Tables: • Molar Stoichiometric Table • Mass Stoichiometric Table

  9. CaseI • Additional Assumptions: Isothermal Reactor Model to Estimate the Reactor Volume • Isothermal Temperature = 673 K • Bulk Density = 900 kgcat/m3 • Void Fraction = 0.44 • Particle Diameter = 5 mm • Inlet Pressure = 1.5 bar

  10. CaseI • Polymath: Isothermal Packed Bed Reactor Model • Results • Stream Flows • Aspen Plus®: RPLUG Reactor • Stream Flows

  11. CaseI • Polymath: Isothermal Packed Bed Reactor Model • Effect of Catalyst Weight and Temperature on Conversion

  12. CaseII • Additional Assumptions: Pressure Drop in the Fixed-Bed Reactor Must not Exceed 1/10 the Initial Pressure • Pressure drop along the length of the reactor

  13. CaseII • Polymath: Isothermal Packed Bed Reactor Model • Results • Stream Flows • Aspen Plus®: RPLUG Reactor • Stream Flows for Single Tube Reactor • Stream Flows for Multi-Tube Reactor

  14. CaseII • Polymath: Isothermal Packed Bed Reactor Model • Effect of Catalyst Weight and Temperature on Conversion

  15. CaseII • Polymath: Isothermal Packed Bed Reactor Model • Effect of Length on Pressure Drop

  16. CaseII • Comparison of Three Models

  17. CaseIII • Additional Assumptions: • Side reactions and byproducts are taken into consideration • Polymath: Isothermal Packed Bed Reactor Model • Results • Stream Flows • Aspen Plus®: RPLUG Reactor • Stream Flows for Multi-Tube Reactor • Stream Flows for Single Tube Reactor

  18. CaseIII • Polymath: Isothermal Packed Bed Reactor Model • Effect of Reaction Temperature on Selectivity of Maleic Anhydride

  19. CaseIII • Aspen Plus®: RPLUG Reactor • Effect of Reactor Length on Molar Flows

  20. CaseIII • Comparison of Three Models

  21. CaseIV • Additional Assumptions: • Non-isothermal • Energy Balance taken into consideration • Heat exchanger with constant coolant temperature, Ta = 673 K • Overall Heat Transfer Coefficient = 105 J/(m2*K*s)

  22. CaseIV • Polymath: Non-Isothermal Packed Bed Reactor Model • Results • Stream Flows • Aspen Plus®: RPLUG Reactor • Stream Flows for Multi-Tube Reactor

  23. CaseIV • Aspen Plus®: RPLUG Reactor • Effect of Varying Ta On Hot Spot

  24. CaseIV • Comparison of Isothermal and Real Reactor Models: • Polymath • Aspen

  25. CaseV • Optimal Reactor Conditions: • Criteria Met: • Minimal reactor size • Minimized cost • Constant selectivity throughout runs • Gain < 2 • Pressure Drop < 10%

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