Direct Conversion of n-Butane to Isobutene in a Membrane Reactor: Thermodynamic Analysis

Isobutene is an important intermediate compound in the petrochemical industry for the production of polymers (butyl rubber, polybutene, and isoprene) and methyl tert-butyl ether. In this work, the n-butane dehydroisomerization reaction in a membrane reactor (MR) was investigated by thermodynamic analysis in a wide range of temperatures, reaction pressures, and equilibrium hydrogen partial pressures, by means of a simplified reaction scheme. The shift of the equilibrium conversion in an MR was evaluated by taking into account the chemical reaction equilibrium and the permeative equilibrium through a 100% hydrogen-selective membrane. The evaluated limits imposed by thermodynamics on an MR are much wider than those of a traditional reactor so that a conversion of about 7 times higher could be obtained over that of the traditional process under a set of operating conditions. This gives a powerful indication on how the use of an MR can extend the thermodynamic limits of this reaction, in terms of conversion, even at thermodynamically unfavorable operating conditions.