Effect of Extra-Framework Fe Species in Pt/Fe/ZSM-23 Catalysts on Hydroisomerization Performance of n-Hexadecane

Pt/xFe/ZSM-23 catalysts with various Fe contents were prepared to explore the influence of extra-framework Fe (EF-Fe) on the n-hexadecane (n-C16) hydroisomerization performance. UV–vis and 57Fe Mössbauer spectroscopic results suggest that the Fe species composition was significantly different under various Fe contents, with (HO–Fe(III)–O–Fe(III)–OH) and [Fe(OH)2]+ as the main Fe species at low Fe content (<1.98 wt %), whereas the Fe2O3 clusters/particles as the dominant ones at high Fe content (>1.98 wt %). Moreover, the concentration of Brønsted acid sites and Pt dispersion could be controlled by tailoring the Fe content. Correspondingly, the hydroisomerization performance of n-C16 over Pt/xFe/ZSM-23 catalysts was dramatically changed with various Fe contents. The Pt/1.98Fe/ZSM-23 catalyst with 1.98 wt % EF-Fe content exhibited considerably excellent hydroisomerization performance, and both n-C16 conversion and selectivity to iso-hexadecane (i-C16) could reach over 80 wt % when the reaction temperature was 310 °C.