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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. Lecture 6

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Lecture 6 - Tuesday 1/25/2011 2

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ReactorDifferentialAlgebraicIntegral CSTR PFR Batch X t PBR X W 3 Previous Lectures

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4 A reactor follows an elementary rate law if the reaction orders just happens to agree with the stoichiometric coefficients for the reaction as written. e.g. If the above reaction follows an elementary rate law 2nd order in A, 1st order in B, overall third order Previous Lectures

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Today’s lecture Example for Liquid Phase Undergraduate Laboratory Experiment (CH 2 CO) 2 O + H 2 O 2CH 3 COOH A + B 2C Entering Volumetric flow rate v 0 = 0.0033 dm 3 /s Acetic Anhydride7.8% (1M) Water92.2% (51.2M) Elementary with k’1.95x10 -4 dm 3 /(mol.s) Case I CSTRV = 1dm 3 Case II PFRV = 0.311 dm 3 8

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Today’s lecture Example for Gas Phase : PFR and Batch Calculation 2NOCl 2NO + Cl 2 2A 2B + C Pure NOCl fed with C NOCl,0 = 0.2 mol/dm 3 follows an elementary rate law with k = 0.29 dm 3 /(mol.s) Case I PFR withv 0 = 10 dm3/s Find space time, with X = 0.9 Find reactor volume, V for X = 0.9 Case IIBatch constant volume Find the time, t, necessary to achieve 90% conversion. Compare and t. 9

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Algorithm for Isothermal Reactor Design 1. Mole Balance and Design Equation 2. Rate Law 3. Stoichiometry 4. Combine 5. Evaluate A. Graphically (Chapter 2 plots) B. Numerical (Quadrature Formulas Chapter 2 and appendices) C. Analytical (Integral Tables in Appendix) D. Software Packages (Appendix- Polymath) 10 Lecture 6

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Example: CH 3 CO 2 + H 2 0 2CH 3 OOH 1) Mole Balance: CSTR: 11 A + B 2C

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2) Rate Law: 3) Stoichiometry: B F A0 Θ B -F A0 X F B =F A0 ( Θ B -X) AF A0 -F A0 XF A =F A0 (1-X) C02F A0 XF C =2F A0 X 12

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1) Mole Balance: 2) Rate Law: 3) Stoichiometry: 15 A + B 2C

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4) Combine: 16

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2 NOCl 2 NO + Cl 2 1) Mole Balance: 2) Rate Law: 17 2A 2B + C

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3) Stoich: Gas 4) Combine: A B + ½C 18`1

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1) Mole Balance: 2) Rate Law: 3) Stoich: Gas, but: 20 Gas Phase 2A 2B + C

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4) Combine: 21

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Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 22

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End of Lecture 6 23

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