chemical reaction engineering i chapter 1 mole balance and
TRANSCRIPT
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Mole Balance and Kinetics by Sureena
Chemical Reaction Engineering I
Chapter 1
Mole Balance and Kinetics
by
Sureena AbdullahFaculty of Chemical and Natural Resources
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Mole Balance and Kinetics by Sureena
Chapter Description
Aims
Expected Outcomes
References & other information
• Describe on the concepts of rate of reactions • Explain about the chemical kinetics, emphasizing definitions and able to relate on
how the reaction rate depends on the concentrations of the reacting chemicals.
• Formulate the rate of reactions for elementary reactions • Define the Rate Law
• Elements of Chemical Reaction Engineering’, by H. Scott Fogler
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Mole Balance and Kinetics by Sureena
Subtopics
Reaction Kinetics and Data Analysis
General mole balance equations
Introduction to conceptual design
1.1
1.2
1.3
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Mole Balance and Kinetics by Sureena
Reaction Kinetics and Data Analysis
o Rate of reaction
o rA → the no. of moles reacting (A) per unit time per
unit volume (mol/dm3 . s)
o rA’ → the no. of moles A per unit time per unit
catalyst mass (mol/ s . g catalyst)
o Unit : mol/dm3/s
o Can be expressed in terms of (sign convention):
i. The rate of disappearance of a substance, -rA
ii. The rate of formation of the substance, rA
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Mole Balance and Kinetics by Sureena
• The reaction kinetics are formulated based on experimentally proven mechanism, not an arbitrary phenomenon
• Rate law is the simplest model, for instance:
A → Products
The rate of transformation of A can be:-
1. Linear function of concentration; or
-rA = kCA
2. Quadratic function of concentration; or -rA = kCA2
• Other function of concentration, such as -rA = k1CA/(1+k2CA) etc
Reaction Kinetics and Data Analysis
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Mole Balance and Kinetics by Sureena
Relation of Rate in Reaction
• For a reaction given below:
aA + bB → cC + dD
• Example:
2NO + O2 →2NO2
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Mole Balance and Kinetics by Sureena
Rate Law
• Consider the following reaction:
aA + bB → cC + dD
The rate law may be written as :
e.g;
where k = specific reaction rate
α = order with respect to A
β = order with respect to B
α+β = overall order
• What happen if
1. α = a and β = b
2. α ≠ a and β ≠ b
Elementary Rate Law
• Stoichiometry coefficients = individual reaction order of each species.
• H2 +I2 → 2HI
(rHI) = k CH2 CI2
Non-elementary Rate Law
• CO+CI2→COCI2
• This rxn is 1st order with respect to CO,
3/2 order with respect to CI2 and 5/2
order overall.
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Mole Balance and Kinetics by Sureena
General Moles balance Equation
FjoFj
Gj and
dNj/dt
System
Volume
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Mole Balance and Kinetics by Sureena
Design Equation for Batch Reactor
j
AO
N
N A
A
)V(r
dNt
−𝑁𝐴0𝑑𝑋
𝑑𝑡= 𝑟𝐴 V
X=𝑁𝐴0−𝑁𝐴
𝑁𝐴0
Limiting reactant
𝑡 = න0
𝑋𝑁𝐴0𝑉
𝑑𝑋
−𝑟𝐴
BatchVrA
A dt
dN
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Mole Balance and Kinetics by Sureena
Design Equation for Continuous Reactors
10
)(r
FFV
A
AA0
AA r
dV
dF
A
AO
F
F A
A
)(r
dFV
'A
Ar
dW
dF
A
AO
F
F
'
A
)(r
dFW
A
X=𝐹𝐴0−𝐹𝐴
𝐹𝐴0
Limiting reactant
𝑉 =𝐹𝐴0𝑋
−𝑟𝐴
𝑑𝑋
𝑑𝑉=−𝑟𝐴𝐹𝐴0
𝑉 = න0
𝑋
𝐹𝐴0𝑑𝑋
−𝑟𝐴𝑑𝑋
𝑑𝑊= −
𝑟𝐴′
𝐹𝐴0
𝑊 = න0
𝑋
𝐹𝐴0𝑑𝑋
−𝑟𝐴′
CSTR
PFR
PBR
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Mole Balance and Kinetics by Sureena
Mole Balance for Reactive Unit
• GENERAL
• Stirred Tank Reactor (STR)
• Tubular Reactor
0
j
j j j
dNF F r V
dt
0A
A A A
dNF F r V
dt
AA V A V V A
dNF F r V
dt
Batch?
Continuous (CSTR)?
Plug Flow?
Packed-Bed?
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Mole Balance and Kinetics by Sureena
Authors Information
Credit to the authors:
Dr Mohd Sabri Mahmud, Assoc Prof Dr
Maksudur Rahman Khan, Dr Hamidah
Abdullah