Activity and regenerability of sulfated zirconia superacid catalysts in isobutane/1-butene alkylation

Alkylation of isobutane with 1-butene was carried out in the gas phase at atmospheric pressure over sulfate-promoted zirconia superacid catalysts prepared by two different procedure. The method of sulfation does not seem to much affect the surface area, superacidity, and crystalline phases present in the catalysts. However, sulfation by impregnation produces a catalyst with more acid sites in the weak and medium strength region. The catalysts showed high C-8 selectivity comparable to liquid acid catalysts; however, use of 1-butene as olefin feed reduces the selectivity toward trimethylpentanes. Increase of olefin space velocity and reaction temperature increases olefin conversion but dimerization of olefin was favored over alkylation. Although the catalysts last their activity within initial few minutes, they could be regenerated by heating in air. Activity of the regenerated catalysts is slightly lower, but the selectivity remains nearly unchanged.