The catalytic activity of Ni/W bimetallic sulfide nanostructured catalysts in the hydrodesulfurization of dibenzothiophene

Abstract

Two types of catalysts containing NiW bimetallic sulfide nanostructures were prepared by a chemical method employing ammonium thiotungstate and nickel nitrate as metal-sulfide precursors followed by sulfidation in H2S/H2 at 400 °C. The nanostructures were grown with excess of Ni, at atomic ratio R = 0.75, 0.85 (R = Ni/Ni + W). High resolution electron microscopy (HRTEM) micrographs revealed the formation of two types of nanostructures, nickel sulfide nanoparticles and long nanorods of tungsten suboxide, both coated by WS2 layers. The Ni/W catalyst containing mostly nanorods presented twice the catalytic activity (pseudo-zero order constant rate k = 12 × 10−7 mol/s.g) of the Ni/W catalyst containing nanoparticles (k = 6.3 × 10−7 mol/s.g) with a low selectivity for tetrahydrodibenzothiophene (THDBT) and high selectivity to cyclohexylbenzene (CHB, 50 mol%). In turn the Ni/W catalyst containing nanoparticles presented a catalytic activity comparable to a Ni/Mo catalyst without inorganic fullerene (IF) nanostructures (k = 7.2 × 10−7 mol/s.g) but with higher selectivity for hydrogenation to THDBT, (14 mol%) than the sample with nanorods.