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

A tetrathiotungstate intercalated NiAl layered double hydroxide (LDH) was synthesized and activated to prepare NiW pre-sulfurized hydrotreating catalysts. The influence of activation atmosphere (N 2 and H 2 ) on the active phase, hydrodesulfurization (HDS) and hydrodearomatization (HDA) activities was investigated. At 300 °C, the catalyst activated under H 2 had more S 2 2− and NiWS phase than that under N 2 . The deeper decomposition of the LDH under H 2 formed more WS 3 while the partial removal of sulfur at the edge of WS 2 by H 2 generated more sulfur-deficient sites to facilitate the decoration of Ni. At 600 °C, metallic Ni and NiWO 4 were formed under H 2 and N 2 , respectively. Moreover, the H 2 atmosphere generated more -SH groups on the catalysts. The catalysts activated under H 2 exhibited higher HDS activity for dibenzothiophene (DBT) and HDA activity for tetralin (THN) than those activated under N 2 , because of the fewer S 2 2− , NiWS and -SH groups in the latter. The catalyst activated under H 2 at 600 °C showed the highest HDS activity, principally because metallic nickel could adsorb DBT to form highly flowable complexes migrating to active sites. Activating under H 2 at 300 °C offered the catalyst the highest HDA activity, due to more S 2 2− and -SH groups present. The use of different activation temperatures under H 2 may be a convenient way to tune the HDS and hydrogenation activity of LDH-based pre-sulfurized catalysts. Activation atmosphere and temperature determined active phases of NiW pre-sulfurized hydrotreating catalysts prepared via a tetrathiotungstate intercalated NiAl layered double hydroxide.