Magnifying the morphology change induced by a nickel promoter in tungsten(IV) sulfide industrial hydrocracking catalyst: A HAADF-STEM and DFT study

Abstract

Changes in the two-dimensional (2D) morphology of nonpromoted WS 2 and Ni-promoted WS2 (NiWS) catalytically active nanolayers supported on amorphous silica-alumina (ASA) are revealed by aberration-corrected scanning transmission electron microscopy and rationalized by density functional theory calculations. The presence of the Ni atoms modifies the triangular shape of nonpromoted WS2/ASA nanolayers into a more hexagonal one for NiWS/ASA by stabilizing the S edge more strongly than the W edge. The higher catalytic activity induced by the addition of the promoter confirms the relevance of such a morphology effect for industrial catalysts. Up for a promotion: By combining high-angle annular dark-field scanning transmission electron microscopy analysis and DFT calculations, the effect of a Ni promoter on the 1D morphology of the NiWS phase supported on amorphous silica-alumina (ASA) is revealed and rationalized. The addition of the Ni promoter induces the observed morphology effect in a catalytically active system relevant for industrial application. TOF=Turnover frequency. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.