Investigation of performance of Ni/W-USY/Al₂O₃ catalyst with full mesoporous in Fischer Tropsch wax hydrocracking

Ni/W-USY/Al₂O₃ with full mesoporous structure was prepared and used for hydrocracking of Fischer Fropsch wax. The catalyst was evaluated for its reaction performance, product characteristics and catalyst properties change. In a 312 h experiment, the result showed that the catalyst possessed high initial activity, and maintained stable after 120 h, and did not show obvious deactivation afterward. When the heavy wax conversion reached 73.95% at the stable stage, the fuel oil selectivity reached to 98.46% and C_{3, 4} constituted the most cracked gas. Gasoline, kerosene and diesel, as the products, were transparent and composed of paraffins and iso-paraffins substituted by methyl-groups. The iso-paraffin contents in the three products were 63.98%, 52.26% and 48.90% respectively. The fresh catalyst contained two main active states of WS₂ and NiWS, had good metal dispersion and rich mesoporous structure. With transition from high activity to stable state of the catalyst property, part of W migrated and formed more Ni-S-W bonds with Ni, and some W-S bonds broke to form W-W bonds after releasing S, resulting in the increase of active states of NiWS and the decrease of WS₂, and forming more Brönsted acid sites and less Lewis acid sites.