E. Hillerova et al., MAGNESIA SUPPORTED NI-MO SULFIDE HYDRODESULFURIZATION AND HYDRODENITROGENATION CATALYSTS PREPARED BY NONAQUEOUS IMPREGNATION, Applied catalysis. A, General, 118(2), 1994, pp. 111-125
Magnesia supported Ni-Mo sulfide catalysts were prepared by three meth
ods: by impregnation from aqueous solutions, by precipitation-adsorpti
on of sulfides in a water-toluene emulsion, and by impregnation from n
on-aqueous solutions using dimethylsulfoxide and methanol as solvents.
They were tested in: (i) the single hydrodesulfurization of thiophene
(HDS), and (ii) the parallel hydrodesulfurization of thiophene (HDS,P
Y) and the hydrodenitrogenation of pyridine (HDN). The reference Ni-Mo
/alumina catalyst was the commercial sample Shell 324. The catalytic a
ctivity of samples prepared by aqueous impregnation and by precipitati
on-adsorption was low, activity for (HDS) and (HDN) of the best sample
being only about 30 and 20%, respectively, of the activity of the She
ll 324 catalyst at 320 degrees C. The chemical and textural instabilit
y of the high surface area magnesia in aqueous solutions was the limit
ing factor. Much higher activity was achieved by non-aqueous impregnat
ion, activity of the best Ni-Mo/MgO sample prepared by this method for
(HDS), (HDS,PY) and (HDN) being 94, 290 and 105%, respectively, of th
e activity of the Shell 324 catalyst at 320 degrees C. As compared wit
h the alumina supported catalyst, the special feature of the Ni-Mo/MgO
catalysts irrespective of the preparation method was lower inhibition
of HDS by parallel HDN and lower selectivity to HDN in parallel HDN a
nd HDS.