Effect of Zirconium modified Y zeolite via in situ synthesis and its regulation on the formation of excellent NiW catalyst for ultra-deep hydrodesulfurization of 4,6-DMDBT

Abstract

Alternative support materials, such as Y zeolite, have been introduced to overcome the challenges associated with industrial alumina-supported hydrodesulfurization (HDS) catalysts. However, to improve catalytic activity while avoiding excessive hydrocarbon cracking, the properties of Y zeolite, including acidity, should be modulated. Herein, Zr-modified Y zeolite was prepared via in-situ synthesis, and the corresponding NiW catalyst was obtained by impregnating hybrid zeolite-alumina supports with metal precursors. The catalytic performance was tested using 4,6-dimethyldibenzothiophene (4,6-DMDBT) as an HDS probe. The position of the Zr species in the zeolites depended on the modification methods. The ZrHY zeolite prepared by impregnation mainly formed non-framework ZrO2 on the surface of zeolite, whereas the HZrY zeolite via in-situ synthesis exhibited Zr species dispersed in the zeolitic framework. Zr species in the zeolitic framework not only enhanced the acidities of the zeolite and hybrid-support (HZrY-Al2O3), but also regulated the interaction of active metals and hybrid support, which significantly enhancing the catalytic activity of the catalyst. Among the four investigated catalysts, the turnover frequency (TOF) and reaction rate constant (k) of 4,6-DMDBT HDS over NiW/HZrYA catalyst were higher efficient than those of other catalysts, and their isomerization selectivity was improved, reducing hydrogen consumption. This enhanced efficiency was attributed to the NiW/HZrYA catalyst having more suitable acid sites, a greater degree of active metals sulfidation, more NiWS phase, superior isomerization performance, and a higher matching degree between hydrogenation and hydrolysis activity. These findings are great meaning for design the ultra-deep low hydrogen consumption HDS catalysts.