1. Review Chapters (1 – 6)
CHPE550: Catalysis and Catalytic Processes
Lecturer: Dr Qazi Nasir Office : 5D-40, College of Engineering

2. Introduction to reaction engineering
Chemical kinetics is the study of chemical reaction rates and reaction mechanisms.
The study of chemical reaction engineering (CRE) combines the study of chemical kinetics with the reactors in which the reactions occur
Phthalic anhydride

3. Introduction to reaction engineering
Manufacture of Phthalic anhydride

4. Introduction to reaction engineering
Water Treatment
Microelectronics
Nanoparticles
Living system
Manufacture of chemicals and pharmaceuticals

5. Introduction to reaction engineering
Smog
Hippo Digestion
Molecular CRE

6. Introduction to reaction engineering
Oil Recovery
Pharmacokinetics
Cobra Bites

7. Introduction to reaction engineering Reaction Rate
The reaction rate is the rate at which a species looses its chemical identity per unit volume
The identity of a chemical species is determined by the kind, number; and configuration of that species' atoms
For example. the species nicotine (a bad tobacco alkaloid) is made of a fixed number of specific atoms in a definite molecular arrangement or configuration

8. Introduction to reaction engineering Reaction Rate
Even though two chemical compounds have exactly the same number of atoms of each element, they could still be different species because of different configurations. For example, 2-butene has four carbon atoms and eight hydrogen atoms; however, the atoms in this compound can form two different arrangements

9. Introduction to reaction engineering Reaction Rate
The reaction rate is the rate at which a species looses its chemical identity per unit volume
The rate of a reaction can be expressed as the rate of disappearance of a reactant or as the rate of appearance of a product.
Consider species A: A  B
-rA = the rate of a disappearance of species A per unit volume
rB = the rate of formation of species B per unit volume

10. Introduction to reaction engineering Reaction Rate
There are three basic ways a species may lose its chemical identity: decomposition. combination. and isomerization.
Decomposition: For example. if benzene and propylene are formed from cumene molecule

11. Introduction to reaction engineering Reaction Rate
Combination: A second way that a molecule may lose its species identity is through combination with another molecule or atom

12. Introduction to reaction engineering Reaction Rate
The third way a species may lose its identity is through isomerization, such as the reaction

13. Introduction to reaction engineering Reaction Rate
Consider the reaction of chlorobenzene and chloral to produce the insecticide DDT (dichorodiphenyl-tricholoethane) in the presence of fuming sulphuric acid

14. Introduction to reaction engineering Reaction Rate
The numerical value of the rate of disappearance of reactant A, -rA is a positive number
e.g. -rA = 4 mol A/dm3.s
The rate of reaction, -rA is the number of moles of A (e.g.. chloral) reacting (disappearing) per unit time per unit volume (mol/dm3.s).
Symbol A represent chloral, B be chlorobenzene, C be DDT, and D be H2O

15. Introduction to reaction engineering Reaction Rate
The heterogeneous reactions involve more than one phase. In heterogeneous reaction systems, the rate of reaction is usually expressed in measures other than volume, such as reaction surface area or catalyst weight.

16. Introduction to reaction engineering Reaction Rate
The rate equation (i.e., rate law) for rj is an algebraic equation that is solely a function of the reacting materials and reaction conditions (e.g., concentration, temperature, pressure or type of catalyst at a point in a system)
The rate equation is independent of the type of reactor (e.g., batch or continuous) in which reaction occurs

17. Introduction to reaction engineering Reaction Rate
The chemical reaction rate law is essentially an algebraic equation involving concentration, not a differential equation
The algebraic form of the rate law for –rA for the reaction may linear function of conc or

18. Introduction to reaction engineering General Mole Balance Equation
To perform a mole balance on any system, the system boundaries must first be specified.
To perform a mole balance on species j in a system volume where species j represents the particular chemical species of interest, such as water or NaOH
Balance on system volume

19. Introduction to reaction engineering General Mole Balance Equation
A mole balance on species j at any instant in time. t. yields the following equation:

20. Introduction to reaction engineering General Mole Balance Equation
Gj. is just the product of the reaction volume V. and the rate of formation of species j, rj
Suppose now that the rate of formation of species j for the reaction varies with the position in the system volume

21. Introduction to reaction engineering General Mole Balance Equation
Dividing up the system volume, V

22. Introduction to reaction engineering General Mole Balance Equation
The rate of generation, ∆Gj1, in terms of rj1 and sub volume ∆V1 is
Similarly the expression can be written for ∆Gj1 and other sub volumes
The total rate of generation within the system volume is the sum of all the rates of generation in each of the sub volumes

23. Introduction to reaction engineering General Mole Balance Equation
By taking the appropriate limits (i.e., let M →∞ and ∆V→0) and making use of the definition of an integral and rewrite the foregoing equation in the form
General mole balance equation
we can develop the design equations
for various types of reactors

24. Reactor Mole Balance Summary
Differential
Algebraic
Integral
Batch
CSTR
PFR (Plug flow reactor)
PBR (Packed bed reactor)

25. Reactor Sizing CSTR
CSTR is modeled as being well mixed such that there are no spatial variations in the reactor. The CSTR mole balance when applied to species A in the reaction
Simplifying, we get CSTR volume required to achieve specific conversion X
X = conversion

26. Reactor Sizing CSTR
Given – rA as a function of conversion, – rA=f(X), one can size any type of reactor. We do this by constructing a Levenspiel plot.
0.2
0.4
0.6
0.8 10 20 30 40 50
Here we plot either
as a function of X. X
XEXIT
For vs. X, the
volume of a CSTR is:
X = conversion

27. Space Time
Space time, τ, is obtained by dividing reactor volume (V) by the volumetric flow rate entering the reactor (vo):
The space time is the time necessary to process one reactor volume of fluid based on entrance conditions.
Consider a tubular reactor which is 20 m long & 0.2 m3 in volume. The dash line represent 0.2 m3 of fluid goes directly upstream of reactor.

28. Space Time
Typical space time for industrial reactors

29. Space Time
Sample industrial space times

30. Space Velocity
Space velocity, SV, is obtained by dividing the volumetric flow rate entering the reactor by the reactor volume :
The SV is the reciprocal of the space time.
Two velocity used in industry is LHSV and GHSV

31. Rate Law Basics k is given by the Arrhenius Equation: Where:
E = activation energy (cal/mol)
R = gas constant (cal/mol*K)
T = temperature (K)
A = frequency factor (units of A, and k, depend on overall reaction order)

32. Batch Stoichiometric Table
At time t = 0, we will open the reactor and place a number of moles of species A, B. C, D, and I (NAO NB0, NCO and Nt respectively) into the reactor.

33. Batch Stoichiometric Table
Species
Symbols
Initial
Change
Remaining A
NA0
-NA0X
NA=NA0(1–X) B
NB0=NA0ΘB
-(b/a)NA0X
NB=NA0(ΘB –(b/a)X) C
NC0=NA0ΘC
(c/a)NA0X
NC=NA0(ΘC+(c/a)X) D
ND0=NA0ΘD
(d/a)NA0X
ND=NA0(ΘD+(d/a)X)
Inert I
NI=NA0ΘI
NI = NA0ΘI
NT0
NT=NT0+δNA0X

35. Algorithm : Pressure Drop in a Packed Bed Reactor
Analyze the following second order gas phase reaction that occurs isothermally in a PBR: 
A   B
Mole Balance:
Must use the differential form of the mole balance to separate variables (remember that FA = FAO * X):
Rate Law:
Second order in A and irreversible:

36. Multiple Reactions and Pressure Drop
In terms of conversion: ε

37. MEMBRANE REACTORS (MR’s)
Fogler page and
Membrane Reactors are used to :
(1) increase conversion when reaction thermodynamically limited
(2) increase selectivity when multiple reactions are occurring

38. (1) Thermodynamically limited reactions
These are reactions where equilibrium lies far to the left
and therefore there is little conversion
If reaction is exothermic, increasing the temperature will
drive reaction further to the left ; decreasing the temp.
results in very slow reaction rate .
- therefore very little conversion
If reaction endothermic, increasing the temp moves
reaction to right therefore favouring higher conversion.
However for many reactions increasing the temp can
destroy the catalyst.

39. STRUCTURE OF MEMBRANE REACTOR
Membrane can either be barrier to certain components
while permeable to others, or
contain active reactive sites and may be a catalyst in itself.
Therefore membrane can either be inert or catalytic
Achieve very high conversions by allowing one of reaction
products diffuse out (eg. Hydrogen is small enough to diffuse
through pores) , therefore high conversion, and
reaction proceeds to completion

40. STRUCTURE OF MEMBRANE REACTOR
Two main types of catalytic membrane reactors
Inert membrane reactor with catalyst pellets on the feed side (IMRCF)
Catalytic membrane reactor (CMR)

41. For the reaction:
the mole balance on hydrogen must be modified because hydrogen leaves through both sides of the reactor and at the end of the reactor. Therefore the mole balance on hydrogen
becomes:
where RB is the molar rate of B leaving the reactor kC is the mass transfer coefficient

42. (2) Enhancing Selectivity
RB = FBO/Vt
FBO molar feed rate of B at sides
Vt the total reactor volume
The feed rate can be controlled by
Controlling pressure drop across
the reactor membrane
Selectivity can be achieved by controlling the feed of species through the reactor and through the membrane.
Can enhance selectivity by keeping one reactant low.
Can keep concentration low by feeding through sides of membrane
Home Task

44. Selectivity and Yield Instantaneous Overall Selectivity: Yield:
Example:
desired product ,
undesired product,

45. Finding the Rate Law Deferential Method Integral Method
Initial Rate Method
Half Life Method
Least Square Method
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