Inhibiting effect of oxygenated model compounds on the HDS of dibenzothiophenes over CoMoP/Al2O3 catalyst
Abstract
The effect of oxygen compounds (guaiacol and phenol) on the hydrodesulfurization (HDS) of
4,6-dimethyldibenzothiophene (46DMDBT) and dibenzothiophene (DBT) was studied on a sulfided
CoMoP/Al2O3 catalyst in a fixed bed microreactor (340 ◦C, 4.0 MPa). The reaction scheme of the transformation
of guiaicol and of phenol (the main intermediate in the transformation of phenol) was established
under deep HDS operating conditions. The transformation of phenol involved two main routes: a hydrogenation
pathway (HYD) involving first the hydrogenation of the aromatic rings followed by C–O bond
rupture (leading to the formation of benzene) and a direct deoxygenation (DDO) pathway involving only
a C–O bond rupture (leading to cyclohexane). These two ways were independent, no transformation of
benzene into cyclohexane was observed. Both oxygen compounds inhibited the hydrodesulfurization of
sulfur compounds due to competitive adsorption between the oxygen and sulfur containing compounds,
with the effect of guaiacol being stronger than the effect of phenol. The inhibition was similar in the
transformation of 46DMDBT and DBT for the same oxygen molecule, showing that the two main routes
(HYD and DDS) involved in the HDS were affected in the same way. This corresponds to a competitive
adsorption between the oxygen and sulfur compounds containing on the catalyst surface according to a
Langmuir–Hinshelwood model.