1. ChE 402: Chemical Reaction Engineering
Steady State Nonisothermal Reactor (Chapter 8)
The energy balance
Adiabatic operations
Non-isothermal flow reactors with heat exchange
Equilibrium conversion and adiabatic temperature
Optimum feed temperature

2. The Energy Balance
Because most reactions we not carried out isothermally, we now focus our attention on heat effect in chemical reactors.
The basic design equations, rate laws, and stoichiomctrjc relationships derived and used in Chapter 4 for isothermal reactor design are still valid for the design of nonisothermal reactors.
The major difference lies in the method of evaluating the design equation when temperature varies along the length of a PFR or when heat is removed from a CSTR.

3. The Energy Balance Rationale:
To identify the additional information necessary to design nonisothermal
Reactors:
Example:
Calculate the reactor volume necessary for 70% conversion:
The reaction is exothermic and the reactor is operated adiabatically. As a result
temperature will increase with conversion down the length of the reactor.

4. The Energy Balance

5. The Energy Balance First Law of Thermodynamics
For a closed system the energy balance is

6. The Energy Balance
open systems

7. The Energy Balance Evaluating the Work Term
It is customary to separate the work term, into flow work and other work,

8. The Energy Balance Evaluating the Energy Term
In almost all chemical reactor situations, the kinetic, potential, and "other"
energy terms are negligible jn comparison with the enthalpy, heat transfer, and
work terms, and hence will be omitted: that is.

9. The Energy Balance
For steady state operation:

10. The Energy Balance

11. The Energy Balance

12. The Energy Balance

13. The Energy Balance

14. The Energy Balance

15. The Energy Balance
We can use this sequence lo prepare a table of as a function of
X. We can then proceed to size PFR and CSTRs.
If there is cooling along the Length of a PFR. we could then apply Equation
(T8-I .E) to this reaction to arrive at two coupled differential equations.

16. The Energy Balance
Similarly, for the case of the reaction carried out in a CSTR. we
could use Polymath or MATLAB to solve two nonlinear equations in X and T.
These two equations are combined mole balance

17. The Energy Balance Heat of Reaction In general,
For the generalized reaction:
In general,

18. The Energy Balance
Energy Balance Equation becomes:

19. The Energy Balance
Enthalpies:

20. The Energy Balance
A large number of reaction carried out in the industries without changing the phase
To calculate the change in enthalpy (Hi - Hio) when the reacting fluid is
heated without phase change from its entrance temperature, TR, to a temperature T
Energy Balance Equation becomes:

21. The Energy Balance
The heat of reaction at temperature T is given in terms of the enthalpy of each species at temperature T, that is,
where the enthalpy of each species is given by

22. The Energy Balance

23. The Energy Balance

24. The Energy Balance
The minus sign indicates the reaction is exothermic. If the heat capacities are constant or if the mean heat capacities over the range 25 to 3500C are readily available

25. The Energy Balance

26. ChE 402: Chemical Reaction Engineering
Steady State Nonisothermal Reactor (Chapter 8)
The energy balance
Adiabatic operations
Non-isothermal flow reactors with heat exchange
Equilibrium conversion and adiabatic temperature
Optimum feed temperature

27. The Energy Balance Heat of Reaction In general,
For the generalized reaction:
In general,

28. The Energy Balance
Energy Balance Equation becomes:

29. The Energy Balance
Enthalpies:

30. The Energy Balance
A large number of reaction carried out in the industries without changing the phase
To calculate the change in enthalpy (Hi - Hio) when the reacting fluid is
heated without phase change from its entrance temperature, TR, to a temperature T
Energy Balance Equation becomes:

31. The Energy Balance
The heat of reaction at temperature T is given in terms of the enthalpy of each species at temperature T, that is,
where the enthalpy of each species is given by

32. The Energy Balance

33. The Energy Balance

34. The Energy Balance
The minus sign indicates the reaction is exothermic. If the heat capacities are constant or if the mean heat capacities over the range 25 to 3500C are readily available

35. The Energy Balance

36. The Energy Balance Heat of Reaction & Enthalpies In general,
For the generalized reaction:
In general,

37. The Energy Balance
Energy Balance Equation becomes:

38. The Energy Balance
Enthalpies:

39. The Energy Balance
A large number of reaction carried out in the industries without changing the phase
To calculate the change in enthalpy (Hi - Hio) when the reacting fluid is
heated without phase change from its entrance temperature, TR, to a temperature T
Energy Balance Equation becomes:

40. The Energy Balance
The heat of reaction at temperature T is given in terms of the enthalpy of each species at temperature T, that is,
where the enthalpy of each species is given by

41. The Energy Balance

42. The Energy Balance

43. The Energy Balance
The minus sign indicates the reaction is exothermic. If the heat capacities are constant or if the mean heat capacities over the range 25 to 3500C are readily available

44. The Energy Balance

45. Adiabatic Operation
Reactions in industry are frequently carried out adiabaticaIly with heating or
cooling provided either upstream or downstream.
Adiabatic Energy Balance

46. Adiabatic Operation In most systems, the work term, can be neglected
In almost all of the systems we will study, the reactants will be entering the
system at the same temperature; therefore,
Adiabatic operation
In many instances, the term in the denominator
is negligible
with respect to the term,

47. Adiabatic Operation

48. Adiabatic Operation
Adiabatic Tubular Reactor

49. Adiabatic Operation

50. Adiabatic Operation

51. Adiabatic Operation

52. Adiabatic Operation

53. Adiabatic Operation

54. Adiabatic Operation

55. Adiabatic Operation

56. Adiabatic Operation

57. Adiabatic Operation
Recalling the rate law gives us

58. Adiabatic Operation
Solution by Hand Calculalion

59. Adiabatic Operation

60. Adiabatic Operation

61. Adiabatic Operation

62. ChE 402: Chemical Reaction Engineering
Steady State Nonisothermal Reactor (Chapter 8)
The energy balance
Adiabatic operations
Non-isothermal flow reactors with heat exchange
Equilibrium conversion and adiabatic temperature
Optimum feed temperature

63. Non-isothermal flow reactors with heat exchange
Steady-State Tubular Reactor
we consider a tubular reactor in which heat is either added or removed through the cylindrical walls of the reactor
In modeling, the reactor, we shall assume that there are no radial gradients in the reactor and that the heat flux through the wall per unit volume of reactor

64. Non-isothermal flow reactors with heat exchange
Deriving the Energy Balance
The heat flow to the reactor, ∆Q. is given in terms of the overall heat transfer coefficient, U, the heat exchange area, ∆A. and the difference between ambient temperature Ta;, and the reactor temperature T.
where a is the heat exchange area per unit volume of reactor.
taking the limit as Energy balance Equation becomes.

65. Non-isothermal flow reactors with heat exchange
From a mote balance on species i. we have
the enthalpy Equation
Differentiating the enthalpy Equation

66. Non-isothermal flow reactors with heat exchange

67. Non-isothermal flow reactors with heat exchange

68. Non-isothermal flow reactors with heat exchange

69. Non-isothermal flow reactors with heat exchange

70. Non-isothermal flow reactors with heat exchange

71. Non-isothermal flow reactors with heat exchange

72. Non-isothermal flow reactors with heat exchange

73. Non-isothermal flow reactors with heat exchange

74. Non-isothermal flow reactors with heat exchange

75. Non-isothermal flow reactors with heat exchange

76. Non-isothermal flow reactors with heat exchange

77. Non-isothermal flow reactors with heat exchange

78. Non-isothermal flow reactors with heat exchange

79. Non-isothermal flow reactors with heat exchange

80. Non-isothermal flow reactors with heat exchange

81. Non-isothermal flow reactors with heat exchange

82. ChE 402: Chemical Reaction Engineering
Steady State Nonisothermal Reactor (Chapter 8)
The energy balance
Adiabatic operations
Non-isothermal flow reactors with heat exchange
Equilibrium conversion and adiabatic temperature
Optimum feed temperature

83. Equilibrium Conversion
The highest conversion that can be achieved in reversible reactions is the equilibrium conversion.
For endothermic reactions, the equilibrium conversion is increases with increasing temperature up to a maximum of 1.0.
For exothermic usually the equilibrium conversion decreases with increasing temperature.

84. Equilibrium Conversion
Exothermic Reactions:
To determine the maximum conversion that can be achieved in an exothermic
reaction carried out adiabatically, we find the intersection of the equilibrium conversion as a function of temperature from Figure 8.4(b) with temperature conversion relationships from the energy balance

85. Equilibrium Conversion

86. Equilibrium Conversion

87. Equilibrium Conversion

88. Equilibrium Conversion

89. Equilibrium Conversion

90. Equilibrium Conversion

91. Equilibrium Conversion

92. Equilibrium Conversion

93. Equilibrium Conversion
Endothermic Reactions:
Because the reaction is endothermic, equilibrium conversion increases with increasing temperature. A typical equilibrium curve and temperature conversion trajectory for the reactor sequence are shown in Figure 8-8.

94. Equilibrium Conversion

95. Equilibrium Conversion
that for an entering temperature of 300 K the adiabatic equilibrium conversion was 0.42.
For 95% of equilibrium conversion (X, = 0,42), the conversion exiting the first
reactor is 0.4. The exit temperature is found from a rearrangement of Equation
2. Calculate the Heat Load
There is no work done on the reaction gas mixture in the exchanger, and the
,th e energy balance given

96. Equilibrium Conversion

97. Equilibrium Conversion
We see that 220 kcal/s is removed from the reaction system mixture. The rate at which energy must be absorbed by the coolant stream in the exchanger is
We consider the case where the coolant is available at 270 K but cannot be heated above 400 K and calculate the coolant flow rate necessary to remove 220 kcal/s from the reaction mixture. Rearranging Equation

98. Equilibrium Conversion
let's next determine the counter current heat exchanger area

99. Equilibrium Conversion

100. Equilibrium Conversion
The conditions entering the second reactor are T = 350 K and X = 0.4. The energy balance starting from this point is shown in Figure
the equilibrium conversion is 60% and the corresponding exit temperature is
T = ( )400 = 430 K
The heat-exchange duty to cool the reacting mixture fmm 430 K back to
350 K can again be calculated from

101. Equilibrium Conversion

102. Equilibrium Conversion
an entering temperature of 300 K the adiabatic equilibrium conversion was
0.42. For 95% of equilibrium conversion (X, = 0,421, the conversion exiting the first reactor is 0.4. The exit temperature is found from a rearrangement of Equation

103. Equilibrium Conversion

104. Equilibrium Conversion

105. Equilibrium Conversion
We consider the case where the coolant is available at 270 K but cannot be heated above 400 K and calculate the coolant flow rate necessary to remove220 kcal\s from the reaction mixture.

106. Equilibrium Conversion

107. Equilibrium Conversion
The conditions entering the second reactor are T = 350 K and X = 0.4. The energy balance starting from this point is shown The corresponding adiabatic equilibrium conversion is Ninety-five percent of the equilibrium conversion is 60% and the corresponding exit temperature is T = ( )400 = 430 K.
The heat-exchange duty to cool the reacting mixture from 430 K back to 350 K can again be calculated from Equation

108. Equilibrium Conversion
Optimum Feed Temperature
Adiabatic reactor of fixed size or catalyst weight. The reaction is reverse and exothermic.

109. Equilibrium Conversion

110. Equilibrium Conversion

111. ChE 402: Chemical Reaction Engineering
Steady State Nonisothermal Reactor (Chapter 8)
The energy balance
Adiabatic operations
Non-isothermal flow reactors with heat exchange
Equilibrium conversion and adiabatic temperature
Optimum feed temperature

112. CSTR with Heat Effects General Steady State Energy Balance Equation:
CSTR Mole balance:
Rearranging the above equation:

113. CSTR with Heat Effects
Energy Balance for the Coolant

114. CSTR with Heat Effects
Solving this equation to find the exit temperature:
From the above equation we can get,

115. CSTR with Heat Effects
General Energy Balance in term of Conversion

116. CSTR with Heat Effects
Volume of CSTR
Again,
For pure component

117. CSTR with Heat Effects

118. CSTR with Heat Effects
CSTR

119. CSTR with Heat Effects

120. CSTR with Heat Effects

121. CSTR with Heat Effects

122. CSTR with Heat Effects

123. CSTR with Heat Effects

124. CSTR with Heat Effects

125. CSTR with Heat Effects

126. CSTR with Heat Effects

127. CSTR with Heat Effects

128. ChE 402: Chemical Reaction Engineering
Catalyis and Catalytic Reactors (Chapter 10)
Definition of catalysis and catalytic processes
Catalysts properties and classification
Steps in a catalytic reaction and adsorption isotherms

129. Catalyst
A catalyst is a substance that affects the rate of a reaction but emerges from the process unchanged. A catalyst usually changes a reaction rate by promoting a different molecular path ("mechanism") for the reaction.
For example, gaseous hydrogen and oxygen are virtually inert at room temperature, bur react rapidly when exposed to platinum.

130. Homogeneous catalysis
Homogeneous catalysis concerns processes in which a catalyst is in solution with at least one of the reactants. An example of homogeneous catalysis is the industrial 0x0 process for manufacturing normal isobutylaldehyde. It has propylene, carbon monoxide, and hydrogen as the reactants and a liquid-phase cobalt complex as the catalyst.

131. Heterogeneous catalysis
A heterogeneous catalytic process involves more than one phase: usually
the catalyst is a solid and the reactants and products are in liquid or gaseous
form. Much of the benzene produced in this country today is manufactured
from the dehydrogenation of cyclohexane (obtained from the distillation of
crude petroleum) using platinum-on-alumina as the catalyst:
A heterogeneous catalytic reaction occurs at or very near the fluid-solid interface. The principles that govern heterogeneous catalytic reactions can be applied for both catalytic and noncatalytic fluid-solid reactions. The two other types of heterogeneous reactions invoIve gas-Iiquid and gas-liquid-solid systems.
Reactions between gases and liquids are usually mass-transfer limited.

132. Because a catalytic reaction occurs at the fluid-solid interface, a large inter
cia1 area is almost always essential in attaining a significant reaction rate. many catalysts, this area is provided by an inner porous structure {i.e., solid contains many tine pores, and the surface of these pores supplies the a needed for the high rate of reaction),