Systematic analysis of the gallium ions and structure-directing agents in the preparation of NiW HDS catalysts over mixed oxides of Al2O3-TiO2

Abstract

In this study, we prepared Al _2 O _3 -TiO _2 (AT) mixed oxides to synthesize NiW catalysts for sulfur removal reactions. The AT support samples were prepared with various surfactants. Additionally, gallium atoms (2.4 wt%) were introduced as an additive to coat the outer surface layers of AT support that lacked Al ^3+ or Ti ^2+ cations. Characterization results showed substantial differences in textural properties, chemical composition, and surface acidity. The x-ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HR-TEM) results demonstrated that the NiW/AT-L-Ga sample has a better combination of dispersion, sulfidation, and promotion among materials. The sulfided NiW/AT-L-Ga catalyst had the highest catalytic activity. After incorporating Ga, XPS observed that the activity could be associated with an increase in the NiWS active phase; however, including a surfactant in the synthesis of the support allowed an increase in the amount of NiWS phase. The active phase was modeled considering the HR-TEM results for the slab length, revealing the atoms at the border susceptible to promotion.

Keywords

• mixed oxides
• hydrodesulfurization
• alumina
• titania
• sulfides