Page 165 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

For chemical reactors, we considered the following items in our justification:
1. Favorable Equilibrium Conversion: If the reaction is endothermic and approaches equilibrium,
it benefits from operating at high temperatures. We recall Le Chatelier’s principle, which
states, “For a reacting system at equilibrium, the extent of the reaction will change so as to
oppose any changes in temperature or pressure.” For an endothermic reaction, an increase in

temperature tends to push the reaction equilibrium to the right (toward products). Conversely,
low temperatures decrease the equilibrium conversion.
2. Increase Reaction Rates: All chemical reaction rates are strongly dependent upon temperature
through an Arrhenius type equation:

(6.1)

As temperature increases, so does the reaction rate constant, k reaction , for both catalytic and
noncatalytic reactions. Therefore, temperatures greater than 250°C may be required to obtain a
high enough reaction rate in order to keep the size of the reaction vessel reasonable.
3. Maintain a Gas Phase: Many catalytic chemical reactions used in processes today require both
reactants and products to be in the gas phase. For high-boiling-point materials or operations