1. Course Name: Catalysis and Catalytic Processes Course Code : CHPE550
Dr. Qazi Nasir
Office No: 5D-40, College of Engineering

2. Rate Law Homogenous reaction Reaction which involves only one phase
Heterogeneous reaction
Reaction which involves more then one phase
Irreversible reaction
Reaction which proceeds only in one direction
Reversible reaction
Reaction which can proceed in either direction

3. Rate Law Molecularity of reaction
The number of atoms, ions or molecules involved in reaction step
Unimolecular reaction
Bimolecular
Termolecular reaction

4. Rate Law
Relative rates of reaction Can be obtained from the ratio of stoichiometric coefficients

5. Rate Law
Example If NO2 is formed at a rate of 4 mol/m3/s The rate of formation of NO The rate of disappearance of NO is The rate of disappearance of O2 is

6. Rate Law
The reaction order and the rate law The rate of disappearance of A, -rA depends on temperature and composition. It can written as product of rate constant kA & function of concentration of various species
Rate law of kinetic expression

7. Rate Law Power Law models
Dependence of the reaction rate (-rA) on concentration fn(Cj) is determined by experimental observation
Alternatively, power law models are used
The exponents of concentration is reaction order

8. Rate Law Power Law models
Units of –rA are in terms of concentration per unit time but units of specific reaction rate kA depends on reaction order
Consider the following reaction

9. Rate Law Elementary reaction
The one that evolves a single step such as biomolecular reaction
The stoichiometric coefficient in this reaction are identical to the power it the rate law
Nonelementary reaction

10. Rate Law Nonelementary reaction
Large number of both homogenous and heterogeneous reactions don not follow simple rate laws
Homogeneous Reactions
The over all order does not have to be an integer

11. Rate Law Nonelementary reaction Heterogeneous Reactions
In many gas-solid reaction, it is often practice to write rate laws in terms of partial pressures rather than concentration
e.g. hydrodemethylation of toluene (T) to form benzene (B) and methane (M) over solid catalyst
The rate of disappearance of toluene per mass of catalyst, -r’T, follows Langmuir-Hinshelwood kinetics and rate law found experimentally to be

12. Rate Law Nonelementary reaction Heterogeneous Reactions
Where KB and KT are the adsorption constants with units of kPa-1 (atm-1) and specific reaction rate has units
Rate of reaction in terms of concentration rather then partial pressure can be written as

13. Rate Law The Reaction Rate Constant
The reaction rate constant k is not truly a constant
It merely independent of concentration
It is almost strong function of temperature
It may be function of total pressure (gas phase-R)
In liquid system it is function of other parameter
e.g. ionic strength, choice of solvent

14. Rate Law The Reaction Rate Constant
Swedish chemist Arrhenius first suggested the temperature dependence of the specific reaction rate, kA could be correlated in equation

15. Rate Law Activation Energy
Most atoms and molecules undergoes reaction, there is an activation energy
Couples of reason
The molecules need energy to distort or stretch their bonds so that they break them to form new bonds
The steric and electron repulsion forces must be overcome as the reacting molecules come close together

16. Rate Law Activation Energy
One way to view the barrier to a reaction is through the use of the reaction coordinates
The coordinates denotes the potential energy of the system as a function of the progress along the reaction path as we go from reactant to an intermediate to product

17. Rate Law
Activation Energy

18. Rate Law Activation Energy
Example: Determination of the Activation Energy
Calculate the activation energy for the decomposition of benzene Diazonium chloride to give chlorobenzene and nitrogen using the table information

19. Rate Law Activation Energy The equation that best fit the data
The slope of the line
Example 3-1 Page 95

20. Batch System
Batch reactor are primarily used for the production of specialty chemicals and to obtained reaction rate data in order to determine reaction rate laws and rate law parameters such as k, the specific reaction rate

21. Batch System
At time t=0, open the reactor and place a number of moles of species A, B, C, D and I (NAO, NBO, NCO, NDO and Nt) into the reactor

22. Batch System
At time t=0, open the reactor and place a number of moles of species A, B, C, D and I (NAO, NBO, NCO, NDO and Nt) into the reactor

23. Batch System Equation of Batch Concentrations
The concentration of A is the moles of A per unit volume CA = NA/V. Similarly, for other components