Promoting di-isobutene selectivity over ZnO/ZrO₂-SO₄ in isobutene oligomerization

Isooctane attracts great interest in recent years because of its promising potential as friendly-environmental gasoline, which is obtained by dimerization of isobutene with a hydrogenation step. Herein, a solid acid catalyst sulfated zirconia modified by ZnO was prepared. The oligomerization of isobutene had been investigated over ZrO₂-SO₄ and ZnO(X)/ZrO₂-SO₄ catalyst in order to find efficient catalysts for the production of isobutene oligomers. The presence of ZnO obviously enhanced the dimerization of isobutene and ZnO(X)/ZrO₂-SO₄ exhibited the highest di-isobutene yield of 60%. Kinetic studies showed the higher trimerization-to-dimerization activation energy ratios of ZnO(X)/ZrO₂-SO₄ than those of ZrO₂-SO₄ from 353 to 393 K. In addition, reaction rate of dimerization was higher than trimerization over ZnO(X)/ZrO₂-SO₄. The high L/B ratio manifested the capability to enhance the selectivity of C₈ in isobutene dimerization. Furthermore, ZnO(X)/ZrO₂-SO₄ exhibited stable conversion for the dimerization of isobutene.