E ﬀ ect of the Gallium and Vanadium on the Dibenzothiophene Hydrodesulfurization and Naphthalene Hydrogenation Activities Using Sulﬁded NiMo-V 2 O 5 / Al 2 O 3 -Ga 2 O 3

: The e ﬀ ect of Ga and V as support-modiﬁer and promoter of NiMoV / Al2O3-Ga2O3 catalyst on hydrogenation (HYD) and hydrodesulfurization (HDS) activities was studied. The catalysts were characterized by elemental analysis, textural properties, XRD, XPS, EDS elemental mapping and High-resolution transmission electron microscopy (HRTEM). The chemical analyses by X-ray Fluorescence (XRF) / Al-Ga(1%-I) < NiMo-S / Al 2 O 3 < NiMoV-S / Al-Ga(1%-SG), whereas the rate constants’ values (k) of naphthalene HYD from 0.022 to 2.23 L / (h · mol · m 2 ) as follow: NiMoV-S / Al-Ga(1%-SG) < NiMo-S / Al 2 O 3 < NiMoV-S / Al-Ga(1%-I). We consider that Ga and V act as structural promoters in the NiMo catalysts supported on Al 2 O 3 that allows the largest generation of BRIM sites for HYD and CUS sites for DDS. conﬁrmed the presence of Ni, Mo, V, Ga, S, Al and O with well-distribution on support. The NiMo / Al 2 O 3 and NiMoV / Al 2 O 3 -Ga 2 O 3 (1%-SG) showed better textural properties than NiMoV / Al 2 O 3 -Ga 2 O 3 (1%-I) with average pore radius between 6.18 and 7.89 nm. XRD conﬁrmed the presence of (NH 4 ) 4 [NiMo 6 O 24 H 6 ] • 5H 2 O and XPS evidenced Mo 4 + , Mo 6 + , Ni x S y , Ni 2 + , Ga 3 + and V 5 + species, which shown a dependence with the synthesis method of the support, whereas gallium and vanadium oxides were not detected due to the well dispersed on the support, suggesting that the synthesis method via impregnation induced largest presence of gallium on the surface allowing a better dispersion of V 5 + oxides inﬂuencing in the degree of sulﬁdation. The HRTEM analysis shown that the length and stacking distribution of MoS 2 crystallites changes with the support synthesis method varied from 5.07 to 5.94 nm and 2.74 to 3.58, respectively. The activities as dibenzothiophene HDS overall pseudo-ﬁrst-order rate constants’ values (k HDS ) from 1.65 to 7.07 L / (h · mol · m 2 ), and naphthalene HYD activity with rate constants’ values (k) from 0.022 to 2.23 L / (h · mol · m 2 ). The previous observations allow us to conclude that Ga and V act as structural promoters in the NiMo catalysts supported on Al 2 O 3 that contribute in the largest generation of BRIM sites for HYD and CUS sites for DDS. and E.M.; writing—original writing—review and visualization, and E.P.-P.; resources, E.P.-P., and


Introduction
The hydrotreating processes (HDT) uses hydrogenolysis and hydrogenation reactions to remove contaminants such as sulfur, nitrogen, oxygen and metals, and saturate hydrocarbons from liquid petroleum fractions within an oil refinery [1,2]. Catalytic hydrotreating depends largely on the origin of the feed, the operating conditions and the nature of the catalyst with the purpose of increase the quality of transportation fuels [3]. The current generation of hydrotreating catalysts are alumina supported Ni(Co) promoted Mo(W) sulfides; however, these catalysts have some defects, such as the difficulty in its sulfurization and the strong interaction between support and active species [4]. In these catalysts, the models by Topsøe and Chianelli propose that the active sites in these reactions are attributed to sites located on the edges, corners, BRIM or RIM [5,6]. The new regulations nowadays which aim at a severe oil feedstock specifications represent a challenging task for oil refineries [7]. In Colombia, the Ministries of Mines and Energy, in 2014 issued regulations that lead to improved quality of diesel in terms of sulfur and polycyclic aromatic content [8]. To achieve these regulations, in the last decades, efforts have been tried to improve the catalytic properties of traditional catalysts, such as changing the active phase and promoter, varying the preparation method and modifying the support [9,10]. In this sense, many studies describe the influence of support on the performance of HDT catalysts, because their interaction with the active phase determines the morphology, dispersion, sulfur lability, mobility and stability of the corresponding metal site [11]. Usually, the alumina is the catalytic support most used HDT, since it has excellent mechanical, low cost and ability to provide dispersion properties [12]. However, the active components are loaded on it through an impregnation method, which leads to a calcination step that causes the formation of Ni(Co)Mo(W)-AlO 4 species (compounds not active in HDT). Hence, recent studies have shown use alumina-modifier elements such as boron, fluorine, phosphorus, silicon, zeolites [13,14], magnesium [15], titanium [16], zinc [17], which could increase the dispersion of the active phase and decrease the active phase(promoter)-support interactions. By taking into account of these limitations, recent studies have shown as potential active phase for such applications the Anderson type polyoxomolybdates [18]. The planar structure of the Anderson type polyoxomolybdates is a relevant factor, producing an active surface with an ordered distribution and uniform deposition, besides the suppression of calcination steps during the activation process could avoid the decrease of active Ni(Co) which favors the synergic effect, doing it an interesting alternative to HDS traditional systems [19].
The addition of gallium and vanadium for the preparation NiMo/Al catalysts has been reported by De los Reyes, who suggested that the Ga 3+ added to alumina increased HDS activity [20,21]. Cimino and Lo Jacono reported the modification of Ni tetrahedral/octahedral ratio in Ni/Al 2 O 3 catalysts by the addition of Ga 3+ to alumina [22]. Zepeda et al. demonstrated that the addition of Ga has a strong effect on the CUS, improving the HYD mechanism in the HDS reaction [23]. Petre et al. found that the acidity of the support was modified with Ga, increasing its HDS activity and modifying the desulfurization (DDS)/HYD selectivity [24]. Altamirano et al. reported that the addition of Ga inhibit the formation of Ni(Co)Al 2 O 4 and it improves the sulfiding of the active species [20].
On the other hand, studies have shown that small amounts of vanadium to hydrotreating catalyst leads to the increase in the support acidity as reported by De Jonghe et al. in his study on toluene HYD using V-NiMo catalysts [25]. In this sense, Rankell and Rollman showed that VSx was active for HDT [26]. Lacroix [27] prepared VSx and it was more active in HDS than that MoS 2 and WS 2 , respectively. Paulino et al. have obtained V-based catalysts promoting the HDS and HDN of LCO (7 times greater activities than MoS 2 ) [28,29]. Escalante et al. showed that Al-MCM-41-supported V sulfides catalysts presented the highest formation of hydrogenated products in the thiophene HDS due to the support nature with lower Si/Al(Zr) ratios [30].
In this regard, seeing the importance of Ga and V separately to hydrotreating reactions the present work reports the effect of the addition of Ga and V in NiMoV/Al 2 O 3 -Ga 2 O 3 catalyst by two different preparation methods looking to enhance their desulfurization and hydrogenating properties on the HDS and HYD activity of dibenzothiophene and naphthalene. Table 1 shows the experimental chemical analyses of Al 2 O 3 -Ga 2 O 3 (1%-SG), Al 2 O 3 -Ga 2 O 3 (1%-I), NiMo/Al 2 O 3 , NiMoV/Al-Ga(1%-SG) and NiMoV/Al-Ga(1%-I) by XRF. The relative deviations between experimental and theoretical could relate to the synthesis procedures. Nevertheless, the experimental accuracy of Mo/Ni and (V+Ni)/(V+Ni+Mo) are in agree with the composition nominal proposed, i.e., 6 and 0.35, respectively [31].

Textural Properties
All the N 2 physisorption isotherms shown in Figure 1 are type IV in the IUPAC classification [32]. The hysteresis loops showed that Al 2 O 3 is type H1 due to uniform mesopores and, Al 2 O 3 -Ga 2 O 3 (1%-SG), Al 2 O 3 -Ga 2 O 3 (1%-I) and NiMoV/Al-Ga(1%-SG) types a combination of H1 and H2 related to the ink-bottle and uniform type of mesopores, respectively; while NiMoV/Al-Ga(1%-I) displayed a combination of H2 and H3 due to ink-bottle and laminar type mesopores. The isotherms behavior demonstrates the influence of the synthesis method on textural properties of the catalysts [32].
The Table 1 shows that the textural characteristics of the supports and catalysts using supports obtained by the sol-gel synthesis method are greater than those obtained by the conventional impregnation method due to the migration of the metallic phase (Ni, Mo, Ga and V) into the support pores during the impregnation process and/or synthesis of the material that decreases their pore volume and therefore the surface area [33]. Hence, the overall surface area was found to increase as follows: NiMoV/Al-Ga(1%-I) < NiMoV/Al-Ga(1%-SG) < NiMo/Al 2 O 3 < Al 2 O 3 -Ga 2 O 3 (1%-I) < Al 2 O 3 -Ga 2 O 3 (1%-SG) < Al 2 O 3 ; whereas the pore volume showed to increase as follows: NiMoV/Al-Ga(1%-I) < NiMo/Al 2 The comparison of the supports shows an increase in the surface area and pore volume with the variation of the synthesis method, which means that the Ga 3+ ions are incorporated into the Al 2 O 3 structure (Ga 3+ ion > Al 3+ ion) [34,35].

XRD Analysis
The XRD patterns of oxidic precursors corresponding to

XPS Analysis
The Figure 2 shows XPS analysis of NiMoV-S/Al-Ga(1%-x). XPS region of Mo 3d 5/2-3/2 showed signals on the surface of Mo 4+ (229 eV), Mo 6+ (232.5 eV) and 2s (226.5 eV), which might be attributable to the Mo sulfide phase, MoO 3 and signal of sulfur [38][39][40]. The higher amount of Mo 4+ species using the synthesis method of impregnation, suggesting that the increased presence on the surface of gallium and vanadium by impregnation method has a positive effect on reducibility (see Figure 3I). The signal of sulfur in the Mo 3d 5/2-3/2 region can be confirmed by the presence of three bands in the S 2p 3/2 region [39]: a signal at 161.7 eV due to terminal disulfide and/or sulfide (S 2− ), another signal at 163.1 eV corresponding to bridging disulfide (S 2 2− ) ligands and the signal at 168.9 eV, which can be assigned to SO 4 2− (see Figure 3III). The signals due to sulfide species are much more important for the catalyst with support modified by impregnation, which showed no presence of sulfates (see Table 2).
Catalysts 2020, 10, x FOR PEER REVIEW 7 of 19   Meanwhile, the Ni 2p region spectra of Figure 3II shows three Ni 2p 3/2-1/2 peaks at 853.1-853.6; 856.1-856.7 and 862 eV [41,42]. These signals suggest, respectively, the presence of NixSy sulfide phases (Ni 2 S 3 , Ni 9 S 8 or NiS), the NiMoO 4 species, and the strong shake-up lines characteristic of Ni 2+ species in a Ni-Mo-O matrix. Note that the signal of Ni does not show considerable variation in the type of Ni species on surface independently of the support synthesis method, although the proportion of Ni is greater in the impregnation synthesis method (see Table 2). The XPS spectra in the Ga 3d and V 2p 3/2-1/2 regions (not shown here), the Ga 3+ (20.5 eV) and V 5+ (517.1 eV) signals could be attributable to Ga 2 O 3 and V 2 O 5 with amounts from 0.1 to 0.6 on the surface [43,44]. The previous experimental results may be due to the presence of different V 5+ species on surface, that is, when the support is modified with Ga, small V rich-aggregates on the surface could predominate depending on their dispersion associated to the solubility of the precursors during synthesis [30]. In the synthesis method by impregnation is possible that, in the Al 2 O 3 -Ga 2 O 3 (1%-I) support, a large number of Ga 3+ sites will be available on the surface even after impregnating the V, which is reflected in the good reducing and sulfiding of the Anderson type polyoxomolybdates as seen in the NiMoV-S/Al-Ga(1%-I) catalysts. While in Al 2 O 3 -Ga 2 O 3 (1%-SG) there a greater dispersion of the V species.

SEM Analysis with Energy Dispersive X-ray Spectroscopy and Elemental Mapping
The SEM microscopy of the NiMoV-S/Al-Ga(1%-SG) and NiMoV-S/Al-Ga(1%-I) catalysts showed that the morphologies consist of particle cumulus with irregular geometries, being smaller particles for NiMoV-S/Al-Ga(1%-SG) as displayed the Figure 4. The EDS elemental mapping confirmed the presence of the atoms constituting the catalysts, i.e., Mo, Ni, Al, O, Ga, V and S. These elements are well-distributed on the support as shown by EDS elemental mapping (Figures 4 and 5). However, the Mo, V and S atoms in NiMoV-S/Al-Ga(1%-I) could not disperse in the whole selected area, suggesting that the concentration of these elements is slightly larger in few catalyst zones ("cluster"), hence the differences observed for V can be associated to the solubility of the precursors, suggesting that some V atoms could precipitate on the support surface forming V rich-aggregates [45].  (Figures 4 and 5). However, the Mo, V and S atoms in NiMoV-S/Al-Ga(1%-I) could not disperse in the whole selected area, suggesting that the concentration of these elements is slightly larger in few catalyst zones ("cluster"), hence the differences observed for V can be associated to the solubility of the precursors, suggesting that some V atoms could precipitate on the support surface forming V rich-aggregates [45].

High-resolution Transmission Electron Microscopy
The HRTEM analysis for NiMoV-S/Al-Ga(1%-SG) and NiMoV-S/Al-Ga(1%-I) is shown in the Figures 6 and 7. The HRTEM micrographs display the presence of homogeneously dispersed MoS2 crystallites with multi-layers (black thread-like fringes with separation of 0.65 nm characteristic of the basal planes (002)), whose values of D showed higher dispersion of the catalytically active MoS2 phase in NiMoV-S/Al-Ga(1%-SG) than NiMoV-S/Al-Ga(1%-I) (see Table 2). The Figures 6 and 7 shows that the length and stacking distribution of MoS2 crystallites changes with the support synthesis method (SG vs. I), which varied from 5.07 to 5.94 nm and 2.74 to 3.58, respectively [46]. Thus, HRTEM image shows that the impregnation method led to the agglomeration of Ni, Mo and V, which was confirmed with the increase in the length and stacking number of the NiMoS phase. This conclusion was also corroborated by EDS elemental mapping ( Figure 5). While for the catalyst obtained via sol-gel was improved the dispersion of NiMo species (D = 0.19 vs. 0.20). Meanwhile, the edge-to-corner ratio a MoS2 slab (fe/fc)Mo increased as the average slab length increased (6.43 to 7.79) [46].

High-Resolution Transmission Electron Microscopy
The HRTEM analysis for NiMoV-S/Al-Ga(1%-SG) and NiMoV-S/Al-Ga(1%-I) is shown in the Figures 6 and 7. The HRTEM micrographs display the presence of homogeneously dispersed MoS 2 crystallites with multi-layers (black thread-like fringes with separation of 0.65 nm characteristic of the basal planes (002)), whose values of D showed higher dispersion of the catalytically active MoS 2 phase in NiMoV-S/Al-Ga(1%-SG) than NiMoV-S/Al-Ga(1%-I) (see Table 2). The Figures 6 and 7 shows that the length and stacking distribution of MoS 2 crystallites changes with the support synthesis method (SG vs. I), which varied from 5.07 to 5.94 nm and 2.74 to 3.58, respectively [46]. Thus, HRTEM image shows that the impregnation method led to the agglomeration of Ni, Mo and V, which was confirmed with the increase in the length and stacking number of the NiMoS phase. This conclusion was also corroborated by EDS elemental mapping ( Figure 5). While for the catalyst obtained via sol-gel was improved the dispersion of NiMo species (D = 0.19 vs. 0.20). Meanwhile, the edge-to-corner ratio a MoS 2 slab (fe/fc) Mo increased as the average slab length increased (6.43 to 7.79) [46].

Catalytic Test
The dibenzothiophene HDS activities in function of the product conversion of the NiMo-S/Al 2 O 3 , NiMoV-S/Al-Ga(1%-SG) and NiMoV-S/Al-Ga(1%-I) catalysts are reported as overall pseudo-first-order rate constants after 6 h of reaction time. Hence, the main reaction products in the HDS of DBT were biphenyl (BP, direct desulfurization route), cyclohexylbenzene (CHB, hydrogenation route) and tetrahydrodibenzothiophene (THDBT), this latter being detected in appreciable amounts at low DBT HDS conversions (<70%) as shows the Figure 8 in the product distributions during reaction times. The catalysts obtained show a large effect of the support synthesis method on intrinsic HDS activities, since the overall activities were found to increase as follows: NiMoV-S/Al-Ga(1%-I) < NiMo-S/Al 2 O 3 < NiMoV-S/Al-Ga(1%-SG), i.e., overall pseudo-first-order rate constants' values (k) of 1.65, 2.47 and 7.07 L/(h·mol·m 2 ), respectively. Likewise, all HDS lead to higher DDS activity (BP formation) with conversions of 85, 87 and 90% for NiMoV-S/Al-Ga(1%-SG), NiMo-S/Al 2 O 3 and NiMoV-S/Al-Ga(1%-I), respectively (see Table 3). The hydrogenation abilities of the catalysts in the HDS reaction was calculated with the HYD/DDS ratios: NiMoV-S/Al-Ga(1%-SG) < NiMo-S/Al 2 O 3 < NiMoV-S/Al-Ga(1%-I). Thus, the introduction of Ga and V to NiMoV-S/Al-Ga(1%-SG) resulted in almost a three-fold increase of the rate constant than their unpromoted analog, while NiMoV-S/Al-Ga(1%-I) was more than half; display that NiMoV-S/Al-Ga(1%-SG) was the most active between the synthesized and tested catalysts. This result suggests that the way to incorporate Ga into the support influences the dispersion of the V 5+ species (structural promoter) [30]. It is well known that Ga-incorporation into A 2 O 3 -framework provides an increased number of acid sites that allow a better dispersion [20]. In the case of NiMoV-S/Al-Ga(1%-I) was observed small V rich-aggregates with greater presence of Ga on the surface that favors good hydrogenating properties NiMoS [20,21]. Table 3. Apparent rate constants of NiMoV-S/Al-Ga(1%-x) catalyst varying the synthesis method (x = SG and I) for DBT hydrodesulfurization (HDS) and naphthalene hydrogenation (HYD) in the reaction network shown in Schemes 1 and 2.

HDS Rate Constants, L/(h·mol·m 2 )
HYD Rate Constants, L/(h·mol·m 2 ) The aforementioned can be confirmed with naphthalene HYD activities, which shows that NiMoV-S/Al-Ga(1%-I) was more active than NiMo-S/Al 2 O 3 and NiMoV-S/Al-Ga(1%-SG) with conversions around 35% as shown in Figure 8. It showed a higher rate of constants' values (k), which varied in a wide range, from 0.022 to 2.23 L/(h·mol·m 2 ) (see Table 3). Liu et al. reported in their studies of naphthalene HYD on highly-loaded NiMo catalysts that the morphological differences of the agglomerated active components (MoS 2 nanoparticles) can be the main reason of their hydrogenation ability and in this sense our NiMoV-S/Al-Ga(1%-I) exhibited much larger MoS 2 nanoparticles than NiMoV-S/Al-Ga(1%-SG) as revealed by HRTEM analysis, suggesting that the hydrogenated intermediate tetralin did not need to desorb from the catalyst surface since there might exist enough space for the total hydrogenation reactions; whereas NiMo-S/Al 2 O 3 and NiMoV-S/Al-Ga(1%-SG) showed a higher selectivity towards tetralin, probably due to a function of adsorption nature more than hydrogenation ability of the catalyst [47]. Resuming all the above observations, we consider that Ga and V act as structural promoters in the NiMo catalysts supported on Al 2 O 3 that allows the largest generation of BRIM sites for HYD and coordinative unsaturated sites (CUS) for DDS.

Preparation of Alumina Modified with Gallium
The catalytic supports with 1 wt% as Ga 2 O 3 was prepared by two different methods that will be identified as Al 2 O 3 -Ga 2 O 3 (1%-SG) and Ga 2 O 3 /Al 2 O 3 (1%-I). Al 2 O 3 -Ga 2 O 3 (1%-SG) was prepared by the one-pot sol-gel synthesis [34]. In a typical experiment, appropriate amounts of aluminum(III)isopropylate (Al[OCH(CH 3  In the other hand, The Ga 2 O 3 /Al 2 O 3 (1%-I) was prepared by impregnation over pore volume adding dropwise to a flask containing 5 g of Al 2 O 3 (alumina was obtained as above-mentioned without adding gallium) an aqueous solution of Ga[CH 3 COCH=C(O-)CH 3 ] 3 at 353 K, under stirring and pH 6. after removing the solvent by evaporation, the as-made sample was dried at 383 K for 12 h and then it was calcined at 883 K for 6 h.

Preparation of Catalyst Precursors Supported on Modified Alumina with Gallium
The vanadium was impregnated on 3 g of Al 2 O 3 -Ga 2 O 3 (1%-I) and Al 2 O 3 -Ga 2 O 3 (1%-SG) over pore volume adding dropwise an acidified aqueous solution of ammonium metavanadate (5.5 wt% V 2 O 5 , sigma-Aldrich 98%) at 353 K, under stirring and pH 5-6 until that the solvent is removed by evaporation. The mass obtained was dried at 383 K for 12 h and then it was calcined at 773 K for 4 h. The (NH 4 ) 4 [NiMo 6 O 24 H 6 ]•5H 2 O supported on alumina modified with gallium and vanadium will be identified as NiMoV/Al-Ga(1%-x), where x is the synthesis method of the support (SG: sol-gel and I: impregnation). Likewise, NiMoV/Al-Ga(1%-x) sulfided will be identified as NiMoV-S/Al-Ga(1%-x).

Catalyst Characterization
The elemental analysis for NiMoV/Al-Ga(1%-x) was determined by XRF using a MagixPro PW-2440 Philips instrument. Sulfur elemental analysis was carried out employing a combustion method employing a Fisons EA 1108 CHNS-O analyzer in solids HDS postreaction. The textural properties were determined utilizing the physisorption technique of N 2 at 77 K using a Micromeritics 3FLEXTM instrument. The surface areas of samples were calculated by the Brunauer-Emmett-Teller multipoint method (BET) and, total pore volume and pore size distribution were determined from the adsorption branch of the isotherm using the Barret-Joyner-Halenda (BJH) model [48]. XRD analysis of the samples was carried out using a BRUKER D8 ADVANCE diffractometer with a Cu Kα radiation source (λ = 1.5418 Å) and Ni filter, within the range 5 • ≤ 2θ ≤ 90 • , step size of 0.02 • and acquisition speed of 0.08 • /s. Identification of the different phases was made using the JCPDS library [37]. The surface composition of the sulfided catalysts was determined through of X-ray photoelectron spectroscopy (XPS) with a Thermo Scientific K-Alpha spectrometer, equipped with a dual (non-monochromatic) Mg/Al anode, operated at 400 W and under a vacuum better than 10 −9 torr. Calibration of the instrument was carried out employing the Au 4f 7/2 line at 83.9 eV. The internal referencing of binding energies was made using the dominating Al 2p band of the support at 74,4 eV [49]. Morphology of the samples was observed by scanning electron microscopy (SEM) using a field emission scanning electron microscope (JEOL, model JSM-7800F, Japan) operated at 1 kV. The mapping images and elemental analysis characterization were acquired simultaneously at 15 kV using the energy-dispersive X-ray spectroscopy (EDS) analyzer coupled to the same JEOL 7800F instrument. The average morphology of the MoS 2 active phase in the catalysts was observed in HRTEM images, which were obtained on a JEOL 2010 microscope with a 1.9 Å point-to-point resolution at 200 kV. From 10 to 15 representative micrographs were obtained for each catalyst in high-resolution mode. Typically, the slabs lengths and stacking of least 350-400 crystallites of MoS 2 were measured for each catalyst along with its dispersion, the average fraction of Mo atoms at the MoS 2 edge surface was calculated as suggesting Li et al. [46].
In the reaction both the alumina supporting, and the V or Ga-modified alumina showed negligible dibenzothiophene and naphthalene conversion. Absence of mass and heat flow transport effects was verified according to established procedures [50,51]. All experiments reported in this work (synthesis protocols, characterizations and catalytic activity measurements) were carried out at least in triplicate. Good reproducibility was verified, better than 10% in all quantitative measurements. The system of differential equations to calculate the catalytic constants was solved using the Maxima software and the nonlinear parameter estimations were calculated until converged by minimizing the deviation from experimental concentrations using the Levenberg-Marquardt algorithm of the Origin 9 version. In this approach, the apparent rate constants of the dibenzothiophene HDS and naphthalene HYD were calculated as k1*, k2*, k3* and k4* (Equations (1)-(4)) and k1*, k2* and k3* (Equations (5)-(8)), which are defined by kn* = knKn, where kn and Kn are the intrinsic rate and the equilibrium adsorption constants, respectively.
(1) * * * The semi-empirical kinetic models of HDS and HYD were calculated according to the mechanism presented in the Schemes 1 and 2 [52,53], respectively. All the reactions were assumed irreversible due to the excess of hydrogen (considered constant), whereby the reactions are considered of the pseudo-first-order. The HDS kinetic model assumes the existence of active sites for hydrogenation and direct desulfurization, which can be expressed as R Total = R HYD + R DDS , namely the overall pseudo-first order rate constant (k) as k = k 1 * + k 2 *, where k 1 * and k 2 * are the apparent rate constants for the DDS and HYD routes; while the naphthalene is firstly hydrogenated to tetralin, and later to decalin isomers as final reaction products.
The system of differential equations to calculate the catalytic constants was solved using the Maxima software and the nonlinear parameter estimations were calculated until converged by minimizing the deviation from experimental concentrations using the Levenberg-Marquardt algorithm of the Origin 9 version. In this approach, the apparent rate constants of the dibenzothiophene HDS and naphthalene HYD were calculated as k 1 *, k 2 *, k 3 * and k 4 * (Equations (1)-(4)) and k 1 *, k 2 * and k 3 * (Equations (5)-(8)), which are defined by kn* = knKn, where kn and Kn are the intrinsic rate and the equilibrium adsorption constants, respectively.

Conclusions
In the present work, two NiMoV catalysts supported on Al 2 O 3 -Ga 2 O 3 (1%-x) were prepared using two synthesis method different. The changes in the support's composition with gallium and vanadium as promoter resulted in properties different and dispersion of the MoS 2 particles. The evaluation of the NiMoV/Al 2 O 3 -Ga 2 O 3 (1%-x) catalysts in the DBT hydrodesulfurization and NP hydrogenation showed that the catalysts presented significant differences in the activity and selectivity of the products. In this respect, the chemical analyses by FRX for the NiMoV/Al 2 O 3 -Ga 2 O 3 (x) catalysts showed stoichiometric values Mo/Ni~6 and (V + Ni)/(V + Ni + Mo)= 0.31-0.34, while EDS spectra and elemental mapping confirmed the presence of Ni, Mo, V, Ga, S, Al and O with well-distribution on support. The NiMo/Al 2 O 3 and NiMoV/Al 2 O 3 -Ga 2 O 3 (1%-SG) showed better textural properties than NiMoV/Al 2 O 3 -Ga 2 O 3 (1%-I) with average pore radius between 6.18 and 7.89 nm. XRD confirmed the presence of (NH 4 ) 4 [NiMo 6 O 24 H 6 ]•5H 2 O and XPS evidenced Mo 4+ , Mo 6+ , Ni x S y , Ni 2+ , Ga 3+ and V 5+ species, which shown a dependence with the synthesis method of the support, whereas gallium and vanadium oxides were not detected due to the well dispersed on the support, suggesting that the synthesis method via impregnation induced largest presence of gallium on the surface allowing a better dispersion of V 5+ oxides influencing in the degree of sulfidation. The HRTEM analysis shown that the length and stacking distribution of MoS 2 crystallites changes with the support synthesis method varied from 5.07 to 5.94 nm and 2.74 to 3.58, respectively. The activities as dibenzothiophene HDS overall pseudo-first-order rate constants' values (k HDS ) from 1.65 to 7.07 L/(h·mol·m 2 ), and naphthalene HYD activity with rate constants' values (k) from 0.022 to 2.23 L/(h·mol·m 2 ). The previous observations allow us to conclude that Ga and V act as structural promoters in the NiMo catalysts supported on Al 2 O 3 that contribute in the largest generation of BRIM sites for HYD and CUS sites for DDS.