Shape Selectivity in Hydroisomerization of n -Hexadecane over Pd Supported on Zeolites: ZSM-22, ZSM-12 and Beta

The development of bifunctional catalysts with high branched isomers selectivity in hydroisomerization of n -alkanes constantly remains crucial for the manufacture of green biodiesel from vegetable oil. Herein, three bifunctional catalysts (Pd/zeolite) have been prepared by providing 0.5 wt % Pd over the ZSM-12, ZSM-22 and Beta zeolite, respectively. The physicochemical properties of above-prepared zeolites and catalysts were investigated by XRD, SEM, N 2 physical adsorption, NH 3 -TPD, Py-IR measurements and H 2 chemisorption methods. The catalytic property for the n -hexadecane hydroisomerization over three bifunctional catalysts was measured which indicate that higher distribution of mono-branched iso -hexadecane is received over Pd/ZSM-22 and Pd/ZSM-12 catalysts based on the zeolites with one dimensional pore channel due to the high shape selectivity. Compared with Pd/ZSM-12, the Pd/ZSM-22 catalyst displays the higher selectivity for iso- hexadecane because of more favorable metal-acid balance caused by the larger C Pd /C H+ ratio. Furthermore, the Pd/Beta catalyst shows highest catalytic activity and maximum iso -hexadecane yield of 69.7% when the n -hexadecane conversion is 78.9%, which results from the maximal porosity, Brønsted acid sites density and mild acidity.