Mole Balances in Chemical Reaction Engineering

This chapter is from the book

Elements of Chemical Reaction Engineering, 6th Edition

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This chapter is from the book

This chapter is from the book 

Elements of Chemical Reaction Engineering, 6th Edition

Learn More Buy

Summary

1. A mole balance on species j, which enters, leaves, reacts, and accumulates in a system volume V, is

   

   If, and only if, the contents of the reactor are well mixed will the mole balance (Equation (S1-1)) on species A give

   

2. The kinetic rate law for r_j is

   • The rate of formation of species j per unit volume (e.g., mol/s·dm³)

   • Solely a function of the properties of reacting materials and reaction conditions (e.g., concentration [activities], temperature, pressure, catalyst, or solvent [if any]) and does not depend on reactor type

   • An intensive quantity (i.e., it does not depend on the total amount)

   • An algebraic equation, not a differential equation (e.g., −r_A = kC_A or )

   For homogeneous catalytic systems, typical units of –r_j may be gram moles per second per liter; for heterogeneous systems, typical units of may be gram moles per second per gram of catalyst. By convention, –r_A is the rate of disappearance of species A and r_A is the rate of formation of species A.

3. Mole balances on species A in four common reactors are shown in Table S1-1.

TABLE S1-1 SUMMARY OF REACTOR MOLE BALANCES

	Reactor	Comment	Mole Balance Differential Form	Algebraic Form	Integral Form
	BR	No spatial variations
	CSTR	No spatial variations, steady state	—		—
	PFR	Steady state
	PBR	Steady state
	Fluidized CSTR	Steady state	—		—