Chemical Reaction Engineering General Mole Balance Equation Applied

Chemical Reaction Engineering General Mole Balance Equation Applied to Batch Reactors, CSTRs, PFRs, and PBRs

Chemical Identity • A chemical species is said to have reacted when it has lost its chemical identity.

Chemical Identity • A chemical species is said to have reacted when it has lost its chemical identity. • The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms.

Chemical Identity • A chemical species is said to have reacted when it has lost its chemical identity. • The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms. 1. Decomposition

Chemical Identity • A chemical species is said to have reacted when it has lost its chemical identity. • The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms. 1. Decomposition 2. Combination

Chemical Identity • A chemical species is said to have reacted when it has lost its chemical identity. • The identity of a chemical species is determined by the kind, number, and configuration of that species’ atoms. 1. Decomposition 2. Combination 3. Isomerization

Reaction Rate • The reaction rate is the rate at which a species looses its chemical identity per unit volume.

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.

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:

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: r. A = the rate of formation of species A per unit volume

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: r. A = the rate of formation of species A per unit volume -r. A = the rate of a disappearance of species A per unit volume

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: r. A = the rate of formation of species A per unit volume -r. A = the rate of a disappearance of species A per unit volume r. B = the rate of formation of species B per unit volume

Reaction Rate • EXAMPLE: If B is being formed at 0. 2 moles per decimeter cubed per second, ie, r. B = 0. 2 mole/dm 3/s

Reaction Rate • EXAMPLE: If B is being formed at 0. 2 moles per decimeter cubed per second, ie, r. B = 0. 2 mole/dm 3/s Then A is disappearing at the same rate: -r. A= 0. 2 mole/dm 3/s

Reaction Rate • EXAMPLE: If B is being formed at 0. 2 moles per decimeter cubed per second, ie, r. B = 0. 2 mole/dm 3/s Then A is disappearing at the same rate: -r. A= 0. 2 mole/dm 3/s The rate of formation (generation of A) is r. A= -0. 2 mole/dm 3/s

Reaction Rate • For a catalytic reaction, we refer to -r. A', which is the rate of disappearance of species A on a per mass of catalyst basis.

Reaction Rate • For a catalytic reaction, we refer to -r. A', which is the rate of disappearance of species A on a per mass of catalyst basis. NOTE: d. CA/dt is not the rate of reaction

Reaction Rate Consider species j:

Reaction Rate Consider species j: • rj is the rate of formation of species j per unit volume [e. g. mol/dm 3*s]

Reaction Rate Consider species j: • rj is the rate of formation of species j per unit volume [e. g. mol/dm 3*s] • rj is a function of concentration, temperature, pressure, and the type of catalyst (if any)

Reaction Rate Consider species j: • rj is the rate of formation of species j per unit volume [e. g. mol/dm 3*s] • rj is a function of concentration, temperature, pressure, and the type of catalyst (if any) • rj is independent of the type of reaction system (batch, plug flow, etc. )

Reaction Rate Consider species j: • rj is the rate of formation of species j per unit volume [e. g. mol/dm 3*s] • rj is a function of concentration, temperature, pressure, and the type of catalyst (if any) • rj is independent of the type of reaction system (batch, plug flow, etc. ) • rj is an algebraic equation, not a differential equation

Reaction Rate Consider species j: • rj is the rate of formation of species j per unit volume [e. g. mol/dm 3*s] • rj is a function of concentration, temperature, pressure, and the type of catalyst (if any) • rj is independent of the type of reaction system (batch, plug flow, etc. ) • rj is an algebraic equation, not a differential equation • We use an algebraic equation to relate the rate of reaction, -r. A, to the concentration of reacting species and to the temperature at which the reaction occurs [e. g. -r. A = k(T)CA 2].

General Mole Balance

Batch Reactor Mole Balance

Constantly Stirred Tank Reactor Mole Balance

Plug Flow Reactor Mole Balance PFR:

Plug Flow Reactor Mole Balance PFR: The integral form is:

Plug Flow Reactor Mole Balance PFR: The integral form is: This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA 0 to the exit molar flow rate of FA.

Packed Bed Reactor Mole Balance PBR

Packed Bed Reactor Mole Balance PBR The integral form to find the catalyst weight is:

Reactor Mole Balance Summary