Isomerization of <i>n</i>-Butane over SO₄^2–/Al₂O₃–ZrO₂ in a Circulated Fluidized Bed Reactor: Prospects for Commercial Application

Abstract

The stability of alumina-promoted sulfated zirconia (SZA) was investigated to achieve the isomerization of n -butane in a circulating fluidized bed (CFB) unit. The pilot-scale evaluation in a CFB unit showed high stability of the SZA catalyst and that the catalytic activity was dominated by the residence time of n -butane rather than its linear velocity. Increases in the reaction and regeneration temperature both led to an increase in the conversion of n -butane and a decrease in the selectivity to isobutane, caused by increasing side reactions. Although the regeneration was conducted in air, a trace of SO 2 evolved during the regeneration, which could be minimized at the appropriate gas stripping temperature, low regeneration temperature, and high space time of the feed. Compared with conventional fixed-bed technologies, the CFB process shows lower selectivity to isobutane due to the inevitable axial back-mixing and severe “dimerization-cracking” reaction.