Hydro-upgrading of n-octadecane over Pt–Mg/HY catalysts

• Magnesium was added as a promoter to Pt/HY catalyst.
• Pt dispersion was improved with the addition of Mg.
• Weak acid sites, mainly Lewis acid sites, were formed over PtMg/HY catalyst.
• PtMg/HY catalyst was applied to hydro-upgrading of n-octadecane.
• The optimized PtMg/HY catalyst enhanced jet-fuel production.

This work is aimed at investigating the effect of the addition of Mg to Pt/HY catalyst for hydro-upgrading of n-octadecane for production of jet-fuel. Characterizations of catalysts were performed with N2 adsorption–desorption, temperature-programmed reduction in H2 flow, ammonia temperature-programmed desorption, and Fourier transform infrared spectroscopy of adsorbed pyridine. When 3–5 wt% magnesium was added to the Pt/HY catalyst, the conversion of n-octadecane increased, which could be attributed to the increase of dispersion of Pt metal. When magnesium loading was increased over the Pt/HY catalyst, the strength and the number of strong acid sites over the catalyst surface decreased and the number of weak acid sites increased. These results were caused by increasing of the ratio of Lewis acid sites to Brönsted acid sites, which was confirmed by NH3-TPD and FT-IR spectroscopy of adsorbed pyridine. The high yield of jet-fuel over the PtMg(5.0)/HY can be attributed not only to the higher dispersion of Pt metal, but also the higher number of weak strength acid sites. The selectivity to iso-paraffin in the jet-fuel fraction could be reached above 80 wt% over the optimized PtMg/HY catalyst.

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