A novel synthesis of highly active and highly stable non-noble-nickel-modified persulfated Al2O3@ZrO2 core-shell catalysts for n-pentane isomerization

Abstract

The non-noble metal modified sulfated zirconia was found easy to deactivate. Herein, highly active and highly stable non-noble core-shell Ni-S2O82−/Al2O3@ZrO2 catalysts (Ni-SA@Z-x, x = Al content in wt%) have been successfully prepared and investigated for n-pentane isomerization. The results showed that the core-shell Ni-SA@Z-30 provided a sustained high isopentane yield (63.1%) with little or no deactivation within 5000 min at a mild reaction pressure of 2.0 MPa, which can be attributed to the following factors: (i) carbon deposition was greatly suppressed by the large pore size and huge pore volume; (ii) the loss of sulfur entities was suppressed because the small and highly dispersed tetragonal ZrO2 particles can bond with the S species strongly; (iii) strong Brønsted acidity can be maintained well after the isomerization. The pore structures and acid nature of the core-shell Ni-SA@Z-x are entirely different from those of the normal structure Ni-S2O82−/ZrO2-Al2O3, even though the Al content and the compositions of the individual components are the same. The Al2O3 cores endow the catalysts with high internal surface area and high mechanical strength. Meanwhile, the ZrO2 shell, which consists of more and smaller tetragonal ZrO2 particles because of the large surface area of the Al2O3 core, promotes the formation of more stable sulfur species and stronger binding sites.