HYDRODESULFURIZATION OF DIBENZOTHIOPHENE AND 4,6-DIMETHYLDIBENZOTHIOPHENE - EFFECT OF AN ACID COMPONENT ON THE ACTIVITY OF A SULFIDED NIMO ON ALUMINA CATALYST

The transformation of dibenzothiophene and 4,6-dimethyldibenzothiophen e was carried out in a flow reactor at 340 degrees C under a 3.0 MPa h ydrogen pressure. A sulfided NiMo on alumina was used as reference cat alyst. The effect of the acidity was studied by mixing this catalyst w ith silica-alumina, or by using a bifunctional NiMo-Y zeolite catalyst . On the sulfided NiMo on alumina catalyst, dibenzothiophene transform ed mainly through direct desulfurization, yielding biphenyl. This reac tion was much slower in the case of 4,6-dimethyldibenzothiophene, whic h renders the molecule less reactive. The addition of an acidic functi on to the sulfide catalyst did not modify the reactivity of dibenzothi ophene while it strongly increased that of 4,6-dimethyldibenzothiophen e. This is attributed to the isomerization of 4,6-dimethyldibenzothiop hene into 3,6-dimethyldibenzothiophene, which is more reactive than 4, 6-dimethyldibenzothiophene. In the presence of an acidic component, cr acking of the desulfurized molecules can also be observed. (C) 1998 El sevier Science B.V.