Hydroisomerization of n-Hexadecane over anion modified Pt/HfO ₂ catalysts

Pt-promoted tungsten-hafnia catalysts containing different amounts of tungsten (15 and 20 wt% WO ₃) were prepared and tested for hydroisomerization of n-hexadecane in a trickle-bed reactor. All catalysts were calcined under dry air flow at 723 K for 3 h. Pt-promoted sulfated hafnia was also prepared for the purpose of comparison. The catalysts were characterized using BET surface area, X-ray diffraction, and DRIFTS for the adsorption of pyridine. Tungsten-based hafnia catalysts exhibit moderate activity (<80 %) for hydroisomerization of n-hexadecane at a higher operating temperature of 673 K compared to sulfated hafnia (>95 %), which had an operating temperature of 493 K. However, tungsten-based hafnia catalysts were more selective towards iso-C ₁₆ even at higher n-hexadecane conversions. More cracking products were obtained with sulfated hafnia in which the selectivity to iso-C ₁₆ decreases exponentially with n-hexadecane conversion. The less acidic tungsten-hafnia catalysts may be suitable for producing more isomerized products compared to the sulfated analog.