Considerations Relating to a Reversible Reaction

Since many important gas-phase catalytic reactions are reversible, we focus on the implications of this characteristic for reactor design. These stem from both equilibrium and kinetics considerations. 

In Example 21-1 above, the effects on equilibrium of changing P (at constant T and r, initial molar ratio of inert species to limiting reactant) and changing r (at constant P and T) are examined. Here, we focus on the effect of T (at constant P, r) through the dependence of fractional conversion on T. For the reaction A +. . . products (at equilibrium), we examine the behavior of fA (7), where represents /A at equilibrium. 

There is an important difference in this behavior between an exothermic reaction and an endothermic reaction. Fran equation 3.1-5, the van t Hoff equator, the equilibrium constant (Keq) decreases with increasing T for an exothermic reaction, and increases for an endothermic reaction. The behavior of f eq(T) corresponds to this. 

As an example for an endothermic reaction, we use the dehydrogenation of ethylbenzene, reaction (D) in Section 21.1. This is developed in mare detail in file following example. 

For the dehydrogenation of ethylbenzene at equilibrium, CgH10 (EB) CgHg (S) + H2, calculate and plot /EB eq(T), at P = 0.14 MPa, with an initial molar ratio of inert gas (steam, H20) to EB of r = 15 (these conditions are also indicative of commercial opera-liens). Assume ideal-gas behavior, with Kp = 82 X IQ5 exp( — 15,200IT) MPa. 

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