Chemical Reaction Engineering

Transcription

1 Lecture 6 hemical Reaction Engineering (RE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

2 Lecture 6 Tuesday 1/9/13 Block 1: Mole Balances Block : Rate Laws Block 3: Stoichiometry Block 4: ombine Review of Blocks 1, and 3 Examples : Undergraduate Reactor Experiments STR PFR BR Gas Phase Reaction with hange in the Total Number of Moles

3 Review Lecture Building Block 1: Mole Balances in terms of conversion, Reactor Differential lgebraic Integral Batch STR N dt r V V F r t N r V t 3 PFR PBR F dv r F V F r dw r W F r W

4 Review Lecture 3 Building Block : Rate Laws 4 Power Law Model: r k B 3 B α β order in order in B Overall Rection Order 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 r nd order in, 1st order in B, overall third order k B α β

5 Review Lecture 4 Building Block 3: Stoichiometry 5

6 Review Lecture 5 Building Block 4: ombine 6

7 Review Lecture 5 Building Block 4: ombine 7

8 Today s lecture Example for Liquid Phase Undergraduate Laboratory Experiment (H O) O + H O H 3 OOH + B Entering Volumetric flow rate v =.33 dm 3 /s cetic nhydride 7.8% (1M) Water 9.% (51.M) Elementary with k 1.95x1-4 dm 3 /(mol.s) ase I STR V = 1dm 3 ase II PFR V =.311 dm 3 8

9 Today s lecture Example for Gas Phase : PFR and Batch alculation NOl NO + l B + Pure NOl fed with NOl, =. mol/dm 3 follows an elementary rate law with k =.9 dm 3 /(mol.s) ase I PFR with v = 1 dm3/s Find space time, τ with =.9 Find reactor volume, V for =.9 ase II Batch constant volume Find the time, t, necessary to achieve 9% conversion. ompare τ and t. 9

10 Part 1: Mole Balances in terms of onversion lgorithm for Isothermal Reactor Design 1. Mole Balances and Design Equation. Rate Laws 3. Stoichiometry 4. ombine 5. Evaluate. Graphically (hapter plots) B. Numerical (Quadrature Formulas hapter and appendices). nalytical (Integral Tables in ppendix) D. Software Packages (ppendix- Polymath) 1

11 STR Laboratory Experiment Example: H 3 O + H H 3 OOH 1M 51. B M? V 1 dm 3 dm s 11 + B 1) Mole Balance: STR: V F r

12 STR Laboratory Experiment ) Rate Law: r kb 3) Stoichiometry: F -F F =F (1-) B F Θ B -F F B =F (Θ B -) F F =F 1

13 F F 1 1 F B B B B B B 13 STR Laboratory Experiment

14 STR Laboratory Experiment 1 k r k' B 1 k V k V k 1 k 1 1 V k 1 k

15 PFR Laboratory Experiment + B dm 3.34 s 1) Mole Balance: ) Rate Law: dv.311 dm 3 r F r k B? 3) Stoichiometry: 1 15 B B

16 PFR Laboratory Experiment 4) ombine: r k' B1 k1 k 1 V dv k dv 1 1 ln 1 k 1e k.311dm.34dm 3 kd 3 sec 96. sec k.1s

17 Gas Flow PFR Example NOl NO + l B + 1 T T dm 3 s k P P 3 dm.9 mol s..9 V? mol L 1) Mole Balance: dv r F ) Rate Law: r k 17

18 Gas Flow PFR Example 3) Stoichiometry: (Gas Flow) `1 B + ½ 4) ombine: k 1 r 1 k1 dv V k dv kv Da k

19 Gas Flow PFR Example k 1 ln1 1 1 y k sec k 19 V V 94 L

20 onstant Volume Batch Example Gas Phase B + t=? 1) Mole Balance: dt r N V r N V r ) Rate Law: r k 3) Stoichiometry: (Gas Flow) V V N 1 1 V r k 1

21 onstant Volume Batch Example 4) ombine: dt k 1 k 1 dt k k 1 k t dt 1 t 155sec

22 Heat Effects Isothermal Design Stoichiometry Rate Laws Mole Balance

23 3 End of Lecture 6