Influence of zeolite content in NiW/Y-ASA-Al2O3 catalyst for second stage hydrocracking

Abstract

NiW catalysts for second stage hydrocracking were prepared by impregnation of granulated supports with ultrastable zeolite Y content of 5−30 wt%; amorphous silica-alumina content of 45−20 wt%; and γ-Al2O3 content of 50 wt%. The catalysts were studied by low-temperature N2 adsorption, HRTEM, XPS and IR spectroscopy of adsorbed pyridine. Sulfide NiWS particles have been revealed to be similar in all the catalysts according to HRTEM and XPS. It has been shown that concentration of Brønsted acid sites increases with increasing of zeolite content in the catalysts. Hydrocracking tests were carried out at a pressure of 16.0 MPa, a LHSV of 1.4 h−1 and H2 to oil ratio of 750 (v/v). Two samples of unconverted oil with nitrogen content of 11 and 65 ppm obtained from the products of VGO hydrocracking under different severities were used as the feedstocks. The higher zeolite content the higher activity of the catalyst was achieved. However, the increase of zeolite content leaded to the decrease of selectivity to diesel. It has been found that increasing of nitrogen content in the feedstock was followed by a sharp decline in catalyst activity while the change in selectivity to diesel was insignificant. Optimal zeolite content in the support for studied conditions and feedstock with nitrogen content of 65 ppm was 20 wt%.