Synthesis, characterization, and hydrotreating activity of niw presulfurized catalysts prepared via a tetrathiotungstate-intercalated NiAl LDH

Abstract

A tetrathiotungstate-intercalated NiAl layered double hydroxide (LDH) was synthesized and then calcined under N2 at various temperatures to prepare a series of NiW presulfurized hydrotreating catalysts. Upon calcination, WS42- in the interlayer decomposes into WS3 and then WS2, releasing sulfur to sulfurize nickel in the sheets. The property and activities of catalysts for hydrodesulfurization (HDS) of dibenzothiophene and hydrodearomatization (HDA) of tetralin are dependent on the calcination temperature. At 300 °C, WS3 can be well maintained, offering highly active hydrogenation sites S22- and superior HDA activity. As the temperature increases up to 500 °C, WS3 converts into WS2, while nickel sulfides migrate to the edge of WS2 to form NiWS phases with high HDS activity. LDH-based presulfurized catalysts can achieve fully sulfurized and well-dispersed tungsten species even at high tungsten loadings and can retain more WS3 even at high temperatures because of the peculiar properties of LDHs. Therefore, they show better HDS and superior HDA activities over an oxidic NiW LDH-based catalyst (LDO) and an alumina-supported NiWS presulfurized catalyst (NiWS/Al2O3). The optimized catalyst shows 1.59 and 1.05 times higher HDS activity than LDO and NiWS/Al2O3 while 2.05 and 1.77 times higher HDA activity than LDO and NiWS/Al2O3, respectively. It also shows better HDS and HDA activity for a real diesel than a NiCoMoW/Al2O3 commercial catalyst.