Alkylation of isobutane with 2-butene over anion-modified zirconium oxide catalysts Original Research Article

Alkylation of isobutane with cis-2-butene was carried out in the liquid phase in a fixed bed reactor with a sulfated zirconia catalyst, ZrO2/SO4. The influence of the main process variables, i.e., time-on-stream (TOS), isobutane/olefin (I/O) ratio, feed flow rate and reaction temperature on 2-butene conversion and product distribution was investigated. A high initial C5+ alkane yield was observed, associated chiefly with cracking of trimethylpentanes (TMPs). The alkylation/cracking ratio increased with increasing TOS. A run was carried out at 24°C for 70 h with essentially complete conversion of butene to alkylate (C5+), and a TMP maximum selectivity of 69%. No unsaturated olefins or straight chain paraffins were detected in the alkylate product during the catalyst lifetime. The length of the run allowed determination of the apparent sequence in which the various products were formed and converted into one another. Unpromoted ZrO2/SO4 had a higher activity and longer lifetime (TOS) than a platinum promoted catalyst, PtZrO2/SO4. A Pt/ZrO2/WO3 catalyst had even less activity. Two ZrO2/SO4 catalysts which were prepared from the same Zr(OH)4 had similar activity. The ZrO2/SO4 catalyst was regenerated with air at 450°C, with no loss in selectivity to TMPs.