Zinc-modified Pt/SAPO-11 for improving the isomerization selectivity to dibranched alkanes

Abstract

Zinc-modified Pt/SAPO-11 catalysts were prepared by incipient wetness impregnation and assessed in the hydroisomerization of n-octane. Their physicochemical properties were investigated using powder X-ray diffraction, scanning electron microscopy, nitrogen adsorption-desorption, pyridine-adsorbed infrared spectroscopy, temperature-programmed desorption of NH3, temperature-programmed reduction of hydrogen, temperature-programmed desorption of hydrogen, transmission electron microscopy, and X-ray photoelectron spectroscopy. The addition of zinc resulted in high dispersion of platinum. Zinc acted as a competitive adsorbent, changed the location of platinum. The catalyst with a zinc loading of 0.5% gave the highest selectivity to dimethylhexanes, but the conversion was lower than those achieved with the other catalysts. Dimethylhexanes have large molecular diameters, and therefore their diffusion may be difficult. This weakens the catalytic activity of the zinc-modified catalysts and lowers the n-octane conversion.