Preparation of WS2 catalysts by in situ decomposition of tetraalkylammonium thiotungstates

Tungsten tetraalkylammonium thiosalts are used as precursors for the in sit u formation of WS2 catalysts in dibenzothiophene (DBT) hydrodesulfurization . The thermal decomposition of alkyl-ammonium thiosalts proceeds directly t o WS2 without WS3 formation, as in the case of ammonium thiotungstate (ATT) , allowing good control of the catalyst's stoichiometry, The alkyl-ammonium thiosalts give WS2 particles with different characteristic morphologies. T he hydrodesulfurization (HDS) activities of WS2 catalysts derived from alky lthiosalts are higher than those of catalysts derived from the ammonium thi osalt, The reaction rate increases with the size of the cation in the precu rsor. No correlation of catalytic activities with surface areas is found. T he S/W and C/W surface ratios determined by Auger electron spectroscopy dec rease with increasing cation size. Surface composition is WS2.25C1.7, WS1.7 C-0.9 and WS1.3 C-0.7 for the in situ catalysts derived from ammonium, met hylammonium, and butylammonium precursors, respectively. The improved catal ytic properties of WS2 catalysts derived from alkylammonium thiosalts in th e HDS of DBT are attributed to the formation of carbon-containing tungsten sulfide phases on the catalyst's surface. (C) 2000 Elsevier Science B.V. Al l rights reserved.