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 1 1

Today’s lecture Introduction Definitions General Mole Balance Equation Batch (BR) Continuously Stirred Tank Reactor (CSTR) Plug Flow Reactor (PFR) Packed Bed Reactor (PBR) 2

Chemical Reaction Engineering Chemical reaction engineering is at the heart of virtually every chemical process. It separates the chemical engineer from other engineers. Industries that Draw Heavily on Chemical Reaction Engineering (CRE) are: CPI (Chemical Process Industries) Examples like Dow, DuPont, Amoco, Chevron 3

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Chemical Plant for Ethylene Glycol (Ch. 5) Smog (Ch. 1) Plant Safety (Ch. 11,12,13) Lubricant Design (Ch. 9) Cobra Bites (Ch. 6 DVD-ROM) Oil Recovery (Ch. 7) Wetlands (Ch. 7 DVD-ROM) Hippo Digestion (Ch. 2) 5

Materials on the Web and CD-ROM 6

Let’s Begin CRE 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. 7

Chemical Identity A chemical species is said to have reacted when it has lost its chemical identity. The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms. 8

Chemical Identity A chemical species is said to have reacted when it has lost its chemical identity. There are three ways for a species to loose its identity: 1. Decomposition CH 3 CH 3  H 2 + H 2 C=CH 2 2. Combination N 2 + O 2  2 NO 3. Isomerization C 2 H 5 CH=CH 2  CH 2 =C(CH 3 ) 2 9

Reaction Rate The reaction rate is the rate at which a species looses its chemical identity per unit volume. The rate of a reaction (mol/dm 3 /s) can be expressed as either: The rate of Disappearance of reactant: -r A or as The rate of Formation (Generation) of product: r P 10

Reaction Rate Consider the isomerization A  B r A = the rate of formation of species A per unit volume -r A = the rate of a disappearance of species A per unit volume r B = the rate of formation of species B per unit volume 11

Reaction Rate EXAMPLE: A  B If Species B is being formed at a rate of 0.2 moles per decimeter cubed per second, ie, r B = 0.2 mole/dm 3 /s Then A is disappearing at the same rate: -r A = 0.2 mole/dm 3 /s The rate of formation (generation of A) is r A = -0.2 mole/dm 3 /s 12

Reaction Rate For a catalytic reaction, we refer to -r A ', which is the rate of disappearance of species A on a per mass of catalyst basis. (mol/gcat/s) NOTE: dC A /dt is not the rate of reaction 13

Reaction Rate Consider species j: 1. r j is the rate of formation of species j per unit volume [e.g. mol/dm 3 s] 2. r j is a function of concentration, temperature, pressure, and the type of catalyst (if any) 3. r j is independent of the type of reaction system (batch, plug flow, etc.) 4. r j is an algebraic equation, not a differential equation (e.g. = -r A = kC A or -r A = kC A 2 ) 14

General Mole Balance F j0 FjFj GjGj System Volume, V 15

General Mole Balance If spatially uniform If NOT spatially uniform 16

General Mole Balance Take limit 17

General Mole Balance General Mole Balance on System Volume V F A0 FAFA GAGA System Volume, V 18

Batch Reactor Mole Balance Batch Well Mixed 19

Batch Reactor Mole Balance Integrating Time necessary to reduce number of moles of A from N A0 to N A. when t = 0 N A =N A0 t = t N A =N A 20

Batch Reactor Mole Balance NANA t 21

CSTR Mole Balance Steady State CSTR 22

Well Mixed CSTR volume necessary to reduce the molar flow rate from F A0 to F A. CSTR Mole Balance 23

Plug Flow Reactor 24

Plug Flow Reactor Mole Balance 25

Rearrange and take limit as Δ V  0 Plug Flow Reactor Mole Balance 26 This is the volume necessary to reduce the entering molar flow rate (mol/s) from F A0 to the exit molar flow rate of F A.

Alternative Derivation – Plug Flow Reactor Mole Balance Steady State PFR 27

Differientiate with respect to V The integral form is: This is the volume necessary to reduce the entering molar flow rate (mol/s) from F A0 to the exit molar flow rate of F A. Alternative Derivation – Plug Flow Reactor Mole Balance 28

Steady State PBR Packed Bed Reactor Mole Balance 29

Packed Bed Reactor Mole Balance Rearrange: PBR catalyst weight necessary to reduce the entering molar flow rate F A0 to molar flow rate F A. The integral form to find the catalyst weight is: 30

Reactor Mole Balance Summary ReactorDifferentialAlgebraicIntegral CSTR Batch NANA t PFR FAFA V 31

Reactors with Heat Effects EXAMPLE: Production of Propylene Glycol in an Adiabatic CSTR Propylene glycol is produced by the hydrolysis of propylene oxide: Fast Forward 10 weeks from now: 32

What are the exit conversion X and exit temperature T? Solution Let the reaction be represented by A+B  C v0v0 Propylene Glycol 33

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39 Evaluate energy balance terms

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Analysis We have applied our CRE algorithm to calculate the Conversion (X=0.84) and Temperature (T=614 °R) in a 300 gallon CSTR operated adiabatically. X=0.84 T=614 °R T=535 °R A+B  C 42

KEEPING UP 43

Separations These topics do not build upon one another FiltrationDistillationAdsorption 44

Reaction Engineering Mole BalanceRate LawsStoichiometry These topics build upon one another 45

Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 46

Mole BalanceRate Laws 47

Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 48

End of Lecture 1 49

Additional Applications of CRE 50 Supplemental Slides

Additional Applications of CRE 51

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Compartments for perfusion Perfusion interactions between compartments are shown by arrows. V G, V L, V C, and V M are -tissue water volumes for the gastrointestinal, liver, central and muscle compartments, respectively. V S is the stomach contents volume. Stomach V G = 2.4 l Gastrointestinal V G = 2.4 l t G = 2.67 min Liver Alcohol V L = 2.4 l t L = 2.4 min Central V C = 15.3 l t C = 0.9 min Muscle & Fat V M = 22.0 l t M = 27 min 54

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