ABSTRACT
Pt(NH3)4(NO3)2, Pt(NH3)4(Ac)2, (NH4)2PtCl4, and H2PtCl6 were used to prepare Pt/SAPO-11 catalysts to investigate the effect of Pt precursors on the hydroisomerization of n-dodecane. The catalyst derived from Pt(NH3)4(NO3)2 displays the best hydroisomerization activity and selectivity among these precursors. The hydroisomerization conversion of n-dodecane is affected by the platinum particle size, platinum dispersion, the location of platinum, and the valence state of platinum. The selectivity of n-dodecane is determined by the number of Brønsted acid sites and Pt crystal planes. These conclusions are verified by combining transmission electron microscopy, high-resolution transmission electron microscopy, hydrogen temperature programmed reduction, NH3-temperature programmed desorption, and Py-IR studies. The catalyst prepared with Pt(NH3)4(NO3)2 as the precursor exhibits the smallest platinum particle size and the highest platinum dispersion. Most of the platinum particles are supported on the external surface of SAPO-11 with the Pt(111) crystal face. Such a catalyst also possesses a suitable number of Brønsted acid sites and then displays the best catalytic performance. Obviously, the use of various precursors for the Pt-based catalyst can significantly affect the performance of Pt/SAPO-11 for the hydroisomerization of n-dodecane.
