Kinetic Assessment of the Simultaneous Hydrodesulfurization of Dibenzothiophene and the Hydrogenation of Diverse Polyaromatic Structures

Abstract

The elimination of sulfur from fossil fuels via hydrodesulfurization (HDS) is paramount to produce cleaner fuels. Ultradeep HDS refers to reducing sulfur in fuels below the 10 ppm level. Nevertheless, under such conditions, dibenzothiophenes (DBTs) are to be desulfurized in the presence of highly complex aromatic structures that possibly exert inhibitory effects. Therefore, this contribution presents a kinetic study of the inhibition effect of diverse aromatic structures: naphthalene (NP), fluorene (FL), and phenanthrene (PHE), on the HDS of dibenzothiophene over a sulfided NiMo/γ-Al 2 O 3 catalyst. Kinetic modeling was based on the Langmuir−Hinshelwood−Hougen− Watson (LHHW) formalism and was submitted to regression analyses with the reparametrized form of the Arrhenius and van't Hoff equations. Before addressing inhibition effects, the kinetics of the HDS of DBT was revisited. In this sense, observations were better fitted when considering that the two parallel pathways for the HDS of DBT, i.e., the so-called direct desulfurization (DDS) and hydrogenation-mediated desulfurization (HYD) routes, occur on two different types of active sites. The developed model was used as a basis for the kinetic modeling of the inhibition of aromatics on the HDS of DBT. The kinetic parameters for the aromatics were estimated on both catalytic sites and exhibited thermodynamic consistency. Kinetic modeling indicated the following: (i) aromatic compounds and their reaction products are adsorbed on both DDS and HYD sites; (ii) the hydrogenation of naphthalene occurs on both sites while fluorene and phenanthrene only react on HYD sites; (iii) the entropy values suggested that the mobility of the molecules is higher on HYD sites than on DDS sites, except for dibenzothiophene; and (iv) fluorene strongly inhibits HYD sites, because of its structure similarity with dibenzothiophene. These findings are important because they provide an insight into the inhibition effects of polyaromatic compounds of different chemical structures on ultradeep HDS.

Chemometric Exploration of APPI(+)-FT-ICR MS Data Sets for a Comprehensive Study of Aromatic Sulfur Compounds in Gas Oils

“…At highest severity (HDT 3) no more NBT or thiophenes are identified, proving hydrotreatment efficiency. Refractory character of BT and DBT is highlighted, and especially the DBT one 35 which is reportedly attributed to inhibitor effects from H 2 S, basic nitrogen compounds, and aromatics. 36 Relatively high nitrogen contents in HDT 1 and HDT 2 could also explain hydrodesulfurization lack of efficiency.…”

High Metal–Acid Balance and Selective Hydrogenation Activity Catalysts for Hydrocracking of 1-Methylnaphthalene to Benzene, Toluene, and Xylene

“…The results of 1-MN hydrocracking reaction indicated that the 5W­(l)/Beta catalyst possessed higher selective hydrogenation activity than 5W/Beta. In the transition-metal catalyst system, only the brim sites of WS 2 phase exhibit hydrogenation activity. − Compared with 5W/Beta, 5W­(l)/Beta had good dispersion and short length of WS 2 slab at similar metal loading content. In consequence, 5W­(l)/Beta had more slabs than 5W/Beta and nearly twice effective tungsten species of those of 5W/Beta.…”

Adsorption of Dibenzothiophene in Gasoline by Si-MCM-41/Sodium Alginate Porous Hybrid Membrane

“…In order to explore the adsorption kinetics of DBT with Si-MCM-41/SA porous hybrid membranes, the pseudo-second-order kinetic model [30,31] was used to fit and analyze the adsorption kinetic data. The pseudo-second order kinetic equation is as follows [32]:…”