Kinetic assessment of the simultaneous hydrodesulfurization of dibenzothiophene and the hydrogenation of diverse polyaromatic structures

Abstract

<p>The work presents a kinetic study of the simultaneous hydrodesulfurization of dibenzothiophene and hydrogenation of aromatics with different chemical structures. This kind of studies are seldom reported, since many authors deal almost exclusively with hydrodesulfurization. Furthermore, most of these authors employ power rate laws for kinetic modelling neglecting a rigorous analysis of the thermodynamic parameters of the reactions; namely, adsorption enthalpies and entropies.<br></p><p></p><p>Considering this fact, we decided to base our kinetic modelling on a Langmuir-Hinshelwood-Hougen-Watson (LHHW) formalism testing the hypothesis of the existence of one or two different catalytic sites for hydrogenation and desulfurization. The consistency of the aforementioned thermodynamic parameters was assessed considering the criteria postulated by Boudart.</p><p></p><p>Our results allowed concluding that a LHHW model considering two actives sites provides a statically satisfactory fitting of experimental data. In addition, it was possible to determine that inhibition effects of aromatics on hydrodesulfurization exist but depend to some extent on the molecular structure of the aromatic.</p><p></p><p>On the other hand, this work also contributes by providing experimental values of adsorption constants of compounds reacting under hydrotreatment conditions which despite the significant advances in theoretical calculations are not yet available in open literature.</p>

Kinetic Modeling of Hydrotreating for Enhanced Upgrading of Light Cycle Oil

“…These species are the most refractory sulfur compounds, and both steric hindrance and electronic factors are claimed to be responsible for their low reactivity. 15 With respect to apparent activation energies, values between 76 and 122 kJ mol −1 have been obtained, which are in concordance with the values reported in the literature the removal of sulfur-containing molecules in petroleum-derived feedstocks. 51,52 The quality and accuracy of the fitting can be evaluated from the comparison between the prediction of the model (lines) and the experimental data (symbols) plotted in Figure 3.…”

Promotion of C-S Bond Scission over Solid Catalytic Sulfides by Aromatics and Nitrogen Heterocycles

“…On the other hand, it is well known that the hydrodesulfurization of dibenzothiophene undergoes via two parallel pathways: (i) direct desulfurization (DDS) which leads to the formation of biphenyl (BP), and (ii) hydrogenation (HYD) where one of the benzene rings of dibenzothiophene is first hydrogenated to tetrahydro-dibenzothiophene (THDBT) and then to hexa-hydro-dibenzothiophene (HHDBT), followed by the scission of the C-S-C bond to yield cyclohexylbenzene (CHB). 8 In this sense, it is necessary to analyze how the above described effects affected both pathways.…”

“…The second hypothesis is that the hydrogenation-dehydrogenation equilibrium established in the first step of the hydrotreating reaction sequence for the naphthalene 8,23 , indole 24 , and quinoline 25,26 could supply additional surface hydrogen for the C-S bond scission reaction. The reactions networks of the hydrogenations of quinoline, indole, and naphthalene are presented in the Supporting Information (Section S3).…”

“…The presence of nitrogen heterocycles and polyaromatic hydrocarbons on the feedstock of hydrotreating units has been considered one of the main problems to achieve ultra-low sulfur fuels 4,5 because they can outcompete organosulfur compounds for the active sites of the supported Ni(Co)-MoS2 catalysts. [6][7][8][9] In this sense, most researches agree that nitrogen heterocycles bind more strongly than aromatics and organosulfur compounds over the catalytic sites hence inhibiting hydropurification. Furthermore, a linear correlation between the proton affinity of different nitrogen heterocycles and the adsorption equilibrium constants has been found (Figure 1S).…”

Site-dependent reactivity of MoS2 nanoparticles in hydrodesulfurization of thiophene

“…The concentration of the CUS sites has been shown to be dependent on the chemical potential of hydrogen and sulfur in the gas phase and the type of MoS 2 -edge 5,[28][29][30][31][32][33][34][35] . In parallel to DDS, the hydrogenation pathway (HYD) can proceed, in which thiophene adsorption is followed by hydrogenation before C-S bond scission [36][37][38][39][40] . The HYD route involves a different type of active site 4 , proposed to be brim sites located at the top of the MoS 2 particle edges 6,8 .…”