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.

The dry reforming of methane is a promising technology for the abatement of CH 4 and CO 2 . Ni−La 2 O 3 catalysts are characterized by their long-term stability (100 h) when tested at full conversion. The kinetics of dry reforming over these types of catalysts has been studied using both power-law and Langmuir− Hinshelwood-based approaches. However, these studies typically deal with fitting the net CH 4 rate, hence disregarding competing and parallel surface processes and the different possible configurations of the active surface. In this work, we synthesized a Ni−La 2 O 3 catalyst and tested six Langmuir−Hinshelwood mechanisms considering both single and dual active sites for assessing the kinetics of dry reforming and the competing reverse water−gas shift reaction and investigated the performance of the derived kinetic models. In doing this, it was found that: (1) all of the net rates were better fitted by a single-site model that considered that the first C−H bond cleavage in methane occurred over a metal−oxygen pair site; (2) this model predicted the existence of a nearly saturated nickel surface with chemisorbed oxygen adatoms derived from the CO 2 dissociation; (3) the CO 2 dissociation can either be an inhibitory or an irrelevant step, and it can also modify the apparent activation energy for CH 4 activation. These findings contribute to a better understanding of the dry reforming reaction's kinetics and provide a robust kinetic model for the design and scale-up of the process.

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<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>

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