n-Hexane Isomerization over NiO/SO2−4/ZrO2 Catalysts. Effect of Nickel Loading

The effect of nickel addition to the sulfated ZrO2 catalysts for n-hexane isomerization was investigated. A series of catalysts with different nickel concentration (from 0 to 9.6 wt%) were synthesized by supporting nickel on sulfated zirconia by incipient wetness method. After a calcination procedure the catalysts were characterized by X-ray diffraction, nitrogen physisorption (BET method) and its acidic properties were determined by NH3 adsorption. (TPD) and FT-IR of pyridine adsorption. The n-hexane isomerization reaction was carried out in a fixed bed microreactor at 673 K under 345 kPa of total pressure. Results showed that nickel content between 1.5 and 4.5 wt% improved the catalytic activity and favored the formation 2,3-dimethylbutane, which is a highly desired product. X-ray diffraction results showed no evidence of any NiO phase at NiO concentration below 9.6 wt% suggesting a NiO phase highly dispersed on the surface of ZrO2–SO2−4 with crystallite sizes lesser than 3nm. Catalytic activity and 2,3-dimethylbutane selectivity seems to be correlated with the NiO well dispersed phase rather than with their acidic properties.