Hydroprocessing on chromium-containing metal sulfide catalysts

[Display omitted] ► The hydrodenitrogenation activity and selectivity of MoS2 can be greatly enhanced by chromium. ► Chromium and iron are synergistic co-promoters for enhancing the HDN activity of MoS2. ► The predominant phase in unsupported chromium-promoted MoS2 catalysts comprises nanocrystalline MoS2 and amorphous Cr2S3. We showed previously that unsupported catalysts prepared from amine thiomolybdates incorporated with bivalent metals (Fe, Ni, Co) are highly active for hydrodenitrogenation (HDN) and hydrodesulfurization (HDS). In particular, an iron-promoted molybdenum sulfide catalyst gives a much higher HDN-to-HDS activity ratio than commercial supported catalysts. The present study examines trivalent chromium as a promoter for MoS2. The catalyst precursors are synthesized via two routes: one involves olation, the other chelation. Tests with a catalytic cycle oil show that the behaviors of the Cr-containing catalysts prepared from the two routes are qualitatively similar. Chromium is a more effective HDN promoter than iron. The Fe0.5Cr0.5Moy (1≤y≤1.5) trimetallic sulfide is more active and selective for HDN than FeMo and CrMoy bimetallic sulfides. The predominant phase in the chromium-containing catalysts comprises nanocrystalline MoS2 and amorphous Cr2S3.