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 N 2 at various temperatures to prepare a series of NiW presulfurized hydrotreating catalysts. Upon calcination, WS 4 2– in the interlayer decomposes into WS 3 and then WS 2 , 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, WS 3 can be well maintained, offering highly active hydrogenation sites S 2 2– and superior HDA activity. As the temperature increases up to 500 °C, WS 3 converts into WS 2 , while nickel sulfides migrate to the edge of WS 2 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 WS 3 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/Al 2 O 3 ). The optimized catalyst shows 1.59 and 1.05 times higher HDS activity than LDO and NiWS/Al 2 O 3 while 2.05 and 1.77 times higher HDA activity than LDO and NiWS/Al 2 O 3 , respectively. It also shows better HDS and HDA activity for a real diesel than a NiCoMoW/Al 2 O 3 commercial catalyst.

The influence of activation atmosphere on the active phase and hydrotreating activity of LDH-based NiW pre-sulfurized catalysts

“…The doublet separation and peak area ratio of two splitting spin-orbits follow the rule reported previously. 10 The corresponding binding energy and percentages of various species are listed in Table 2. The spectrum of S2p consists of two doublets: one at around 162.9 and 161.8 eV assigned to 2p 1/2 and 2p 3/2 of S 2− , the other at around 164.4 and 163.3 eV assigned to 2p 1/2 and 2p 3/2 of S 2 2− .…”

“…A nitrate NiAl LDH with a Ni/Al ratio of 2 denoted as NiAl–NO 3 was used as a precursor to synthesize tetrathiotungstate-intercalated NiAl LDHs via an ion-exchange method. 10 First, 2.4 g ammonium tetrathiotungstate (ATT) that was lab-synthesized as reported previously 11 and 2.0 g NiAl–NO 3 were dispersed in 100 mL water, in which the molar ratio of WS 4 2− to NO 3 − was set to 1. Second, a 10 wt% ammonia solution was added to the suspension to adjust the pH to 8.…”

“…[6][7][8] Most recently, our group has reported presulfurized NiMo and NiW HT catalysts derived from tetrathiomolybdate and tetrathiotungstate intercalated NiAl LDHs. [9][10][11] Such LDHs were synthesized by an ion exchange method using nitrate NiAl LDHs as precursors, and afterwards they were further activated under N 2 at different temperatures to prepare a series of pre-sulfurized HT catalysts. These catalysts showed better hydrodesulfurization (HDS) activity for dibenzothiophene (DBT) and hydrodearomatization (HDA) activity for tetralin (THN) than oxidic catalysts prepared by molybdate or tungstate intercalated NiAl LDHs and a commercial catalyst.…”

“…Moreover, it was found that the pre-sulfurized NiW catalyst based on a tetrathiotungstate intercalated NiAl LDH exhibited much higher HDS and HDA activities than an alumina-supported NiWS pre-sulfurized catalyst with similar Ni and W loadings prepared by a conventional impregnation method. 10 This is due to the highly dispersed tungsten sulfides and the well retained S 2 2− species even at elevated temperatures.…”

Novel Impregnation–Deposition Method to Synthesize a Presulfided MoS2/Al2O3 Catalyst and Its Application in Hydrodesulfurization

“…Recently, ammonium tetrathiomolybdate [ATTM, (NH 4 ) 2 MoS 4 ] has attracted significant attention as an established active component for the preparation of catalysts in the sulfuric form (i.e., the presulfided catalysts). ,, It was found that the molybdenum sulfide catalyst prepared by the decomposition of ATTM exhibited a good activity toward thiophene hydrogenolysis. , Catalytic hydrogenolysis activity was directly correlated with the number of anion vacancies and the low valence state of the reduced MoS 2 /Al 2 O 3 catalysts. Moreover, as ATTM has already tetrahedrally bonded to molybdenum atoms, which simplifies the sulfidation of oxide precursors, the decomposition of ATTM will lead to completely sulfided catalysts.…”