Direct conversion of n-butane to isobutene in a membrane reactor: a thermodynamic analysis

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