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Lecture 7

Lecture 7. Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place. Today’s lecture. Block 1: Mole Balances Block 2: Rate Laws Block 3: Stoichiometry Block 4: Combine

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Lecture 7

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  1. Lecture 7 Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

  2. Today’slecture • Block 1: Mole Balances • Block 2: Rate Laws • Block 3: Stoichiometry • Block 4: Combine • California Professional Engineers Exam Exam is not curved, 75% or better to pass Problem 4-12

  3. General Guidelines for California Problems Some hints: 1. Group unknown parameters/values on the same side of the equation example:[unknowns] = [knowns] 2. Look for a Case 1 and a Case 2 (usually two data points) to make intermediate calculations 3. Take ratios of Case 1 and Case 2 to cancel as many unknowns as possible 4. Carry all symbols to the end of the manipulation before evaluating, UNLESS THEY ARE ZERO

  4. Gas Phase PFR The irreversible elementary reaction takes place in the gas phase in an isothermal tubular (plug-flow) reactor. Reactant A and a diluent C are fed in equimolar ratio, and conversion of A is 80%. If the molar feed rate of A is cut in half, what is the conversion of A assuming that the feed rate of C is left unchanged? Assume ideal behavior and that the reactor temperature remains unchanged. [From California Professional Engineering/Engineers Exam.] Unknown:

  5. Gas Phase PFR Will the conversion increase or decrease? INCREASE: Slower Volumetric Rate (Reactants spend more time in the reactor DECREASE: Concentration of Reactant Diluted

  6. Gas Phase PFR Assumptions: 1) MoleBalance: 2) Rate Law: 3) Stoichiometry: (gas phase) A  ½ B

  7. Gas Phase PFR 4) Combine:

  8. Gas Phase PFR Case 1: Case 2: Take ratio of Case 2 to Case 1

  9. Gas Phase PFR Most make this assumption to keep pressure the same, CT02=CT01

  10. Gas Phase PFR Solve with computer, X=0.758

  11. Heat Effects Isothermal Design Stoichiometry Rate Laws Mole Balance

  12. End of Lecture 7

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