Chemical Reaction Engineering I Chapter 1 Mole Balance and ...
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Mole Balance and Kinetics by Sureena Chemical Reaction Engineering I Chapter 1 Mole Balance and Kinetics by Sureena Abdullah Faculty of Chemical and Natural Resources Engineering [email protected]
Transcript of Chemical Reaction Engineering I Chapter 1 Mole Balance and ...
Mole Balance and Kinetics by Sureena
Chemical Reaction Engineering I
Chapter 1
Mole Balance and Kinetics
by
Sureena AbdullahFaculty of Chemical and Natural Resources
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
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
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
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
Mole Balance and Kinetics by Sureena
Relation of Rate in Reaction
• For a reaction given below:
aA + bB → cC + dD
• Example:
2NO + O2 →2NO2
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.
Mole Balance and Kinetics by Sureena
General Moles balance Equation
FjoFj
Gj and
dNj/dt
System
Volume
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
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
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?
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
