chemical reaction engineering

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

Introduction

Definitions

General Mole Balance Equation

BatchCSTRPFR

PBR

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)Dow, DuPont, Amoco, Chevron

Materials on the Web and CDROM

http://www.engin.umich.edu/~cre/

Developing Critical Thinking Skills

Socratic Questioning

is the

Heart of Critical Thinking

R. W. Paul’s Nine Types of Socratic

Questions

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.

• A chemical species is said to have reacted when it has lost its chemical identity.

Chemical Identity


• The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms.

Chemical Identity


1. Decomposition

Chemical Identity


1. Decomposition

2. Combination

Chemical Identity


1. Decomposition

2. Combination

3. Isomerization

Chemical Identity

• The reaction rate is the rate at which a species looses its chemical identity per unit volume.

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/dm3/s) can be expressed as either

the rate of Disappearance: -rA

or as

the rate of Formation (Generation): rA

Reaction Rate

Reaction Rate

Consider the isomerization AB

rA = the rate of formation of species A per unit volume

-rA = the rate of a disappearance of species A per unit volume

rB = the rate of formation of species B per unit volume

Reaction Rate

• EXAMPLE: AB If Species B is being formed at a rate of

0.2 moles per decimeter cubed per second, ie,

rB = 0.2 mole/dm3/s

Reaction Rate• EXAMPLE: AB

rB = 0.2 mole/dm3/s

Then A is disappearing at the same rate:

-rA= 0.2 mole/dm3/s

Reaction Rate

• EXAMPLE: ABrB = 0.2 mole/dm3/s

Then A is disappearing at the same rate:

-rA= 0.2 mole/dm3/s

The rate of formation (generation of A) is

rA= -0.2 mole/dm3/s

Reaction Rate

• For a catalytic reaction, we refer to -rA',

which is the rate of disappearance of

species A on a per mass of catalyst basis.

(mol/gcat/s)

NOTE: dCA/dt is not the rate of reaction

Reaction Rate

Consider species j:

• rj is the rate of formation of species j per unit volume [e.g. mol/dm3/s]

Reaction Rate

• rj is the rate of formation of species j per unit volume [e.g. mol/dm3*s]

• rj is a function of concentration, temperature, pressure, and the type of catalyst (if any)

Reaction Rate• rj is the rate of formation of species j per unit

volume [e.g. mol/dm3/s]


• rj is independent of the type of reaction system (batch reactor, plug flow reactor, etc.)

Reaction Rate• rj is the rate of formation of species j per unit

volume [e.g. mol/dm3/s]


• rj is independent of the type of reaction system (batch, plug flow, etc.)

• rj is an algebraic equation, not a differential equation

General Mole Balance

Batch Reactor Mole Balance

CSTRMole Balance

Plug Flow Reactor

Plug Flow Reactor Mole Balance

PFR:

The integral form is:

V dFAr

AFA 0

FA

This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA0 to the

exit molar flow rate of FA.

Packed Bed Reactor Mole Balance

PBR

The integral form to find the catalyst weight is:

W dFA

r AFA 0

FA

FA0 FA r AdW dNA

dt

Reactor Mole Balance Summary

Fast Forward to the Future

Thursday March 20th, 2008

Reactors with Heat Effects

Production of Propylene Glycol in an Adiabatic CSTR

What are the exit conversion X and exit temperature T?

Solution

Let the reaction be represented by

KEEPING UP

Separations

These topics do not build upon one another

Filtration Distillation Adsorption

Reaction Engineering

These topics build upon one another

Mole Balance Rate Laws Stoichiometry

Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

Mole Balance Rate Laws

Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

Batch Reactor Mole Balance

Continuously Stirred Tank Reactor Mole Balance

C S T R Mole Balance

CSTRMole Balance

Plug Flow Reactor


PFR:


PFR:


V dFAr

AFA 0

FA


PFR:


V dFAr

AFA 0

FA

This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA0 to the

exit molar flow rate of FA.


PBR


PBR

FA0 FA r AdW dNA

dt


PBR

The integral form to find the catalyst weight is:

W dFA

r AFA 0

FA

FA0 FA r AdW dNA

dt


Asynchronous Video Series

Chapter 1:

General Mole Balance Equation Applied to

Batch Reactors, CSTRs, PFRs, and PBRs

H. Scott Fogler, Ph.D.

http://www.engin.umich.edu/~cre





Pharmaceutical – Antivenom, Drug Delivery

Medicine – Tissue Engineering, Drinking and Driving

Compartments for perfusion

Perfusion interactions between compartments are shown by arrows.

VG, VL, VC, and VM are -tissue water volumes for the gastrointestinal, liver, central and muscle compartments, respectively.

VS is the stomach contents volume.

StomachVG = 2.4 l

GastrointestinalVG = 2.4 ltG = 2.67 min

Liver

Alcohol

VL = 2.4 l tL = 2.4 min

CentralVC = 15.3 l tC = 0.9 min

Muscle & FatVM = 22.0 l tM = 27 min





Pharmaceutical – Antivenom, Drug Delivery

Medicine –Pharmacokinetics, Drinking and Driving

Microelectronics – CVD

Reaction Rate



Reaction Rate



-rA = the rate of a disappearance of species A per unit volume

chemical reaction engineering

Technology