Dehydrogenation of ethyl benzene (EB) in the presence of excess water (an inert component) produces styrene (S) and hydrogen:
. This reaction is endothermic (i.e., favored by high temperatures). This Demonstration plots the equilibrium conversion versus temperature (blue curve) for various values of the total pressure,
, and the initial molar ratio,
, of water to ethyl benzene. The shape of this curve shows the typical sigmoidal increase in conversion with the increase in temperature for endothermic reactions. Conversions in the blue region are accessible while those in the red region are inaccessible. Typical values used in industry for
are 0.14 MPa and 15, respectively. The equilibrium constant as a function of temperature is given by:
(expressed in MPa).