Effect of SiO2/Al2O3 ratio in Ni/Zeolite-Y and Ni-W/Zeolite-Y catalysts on hydrocracking of heptane

This study investigated the effect of the SiO2/Al2O3 ratio in the range of 5-80 in zeolite Y (ZY) as a support for the bi-functional reaction of heptane hydrocracking. Bi-metallicity impact, through the addition of W on Ni in the supported metal catalysts was also examined. The catalytic activity was assessed at 350?C and 400?C in order to deduce an optimized composition of the catalyst in terms of metal composition and Si/Al ratio. The results were correlated to the catalysts' surface and bulk properties, the latter after employing a number of material characterization techniques. It was shown that Ni-W bimetallic catalysts demonstrated better catalytic activity (conversion, 78% to 91%) than Ni-based monometallic counterpart catalysts (conversion, 74.2% to 82.7%), with NiO-WO3-ZY30 (SiO2/Al2O3 ratio equal to 30) exhibiting the highest conversion. This was attributed to the bimetallic's enhanced metal dispersion and smaller particle size, evaluated using temperature-programmed desorption (TPD) of H-2 and high-resolution transmission electron microscopy (HR-TEM) imaging. The stronger acidity, as quantified by total acidity calculations, of zeolite Y having higher Si/Al ratio, and their balanced ratio of micro-and meso-porosity played a vital role in their catalytic performance. This study provides useful design guidelines on how to adjust both the Si/Al ratio in the zeolite Y support and the catalyst's bimetallicity for enhanced hydrocracking performance.