Dibenzothiophene Hydrodesulfurization Reaction Research Articles

The regulatory role of cysteine in active phase construction of polyoxometalate-based hydrodesulfurization catalysts: Reduction, chelation, and dispersion

Polyoxometalate-based hydrodesulfurization (HDS) catalysts were modified using cysteine to construct efficient CoMoS active phase. Cysteine, characterized by chelating (–COOH, –NH2) and reducing (−SH) groups, assumed a triple role in catalyst synthesis, including reduction, chelation, and dispersion. Cysteine pre-reduced polyoxometalates to heteropoly blue, significantly increasing the catalyst sulfidation. The increased nucleophilicity of heteropoly blue enhanced their attraction to Co2+ ions, intensifying the Co-Mo bimetallic synergy. The formation of Co-chelate species delayed Co sulfidation, allowing for the concurrent sulfidation of both Co and Mo species and promoting the generation of the CoMoS active phase. Carbonaceous deposits from the high-temperature carbonization of cysteine weakened the metal-support interaction, facilitating the dispersion of the active phase. The S-CoPMo12-Cys/Al2O3 catalyst demonstrated high activity in the HDS reaction of dibenzothiophene, showcasing their potential for advanced HDS reaction.

The organic–inorganic dual anchoring strategy based on organic chelators and lacunary polyoxometalates for the preparation of efficient CoWS hydrodesulfurization catalysts

Designing catalysts with bimetallic intimate synergistic effects to enhance catalytic activity has always been a focused problem for hydrodesulfurization (HDS) systems. Efficient HDS catalysts with abundant CoWS active phases were prepared through novel organic–inorganic ligand dual anchoring strategy based on the organic chelating agents and lacunary polyoxometalates (POMs). Citric acid (CA) chelating agent and Co2+ promoter are pre-coordinated in the impregnating solution, the trivacant Keggin [SiW9O34]10- (SiW9) POMs attract the promoter through the nucleophilic oxygen groups at the vacant sites to form the CA-Co@SiW9 “sandwich-like” structure, which allows the organic chelator-promoter-active center to be intimate interaction in a single molecule, thus achieving atomic-scale Co-W proximity on the precursor. In the subsequent sulfidation process, CA delayed the reduction temperature of cobalt species, enabling more Co promoter to be anchored at the edge sites of WS2 clusters to form abundant CoWS active phases, which fully exerted the bimetallic intimate synergism in the HDS reaction. Furthermore, the carbon deposits generated from CA carbonation acted as secondary support weakening the interaction of active metals with Al2O3 support and increasing the sulfidation degree as well as the dispersion of active metals. As a result, the S-Co(CA)W/Al2O3 catalyst achieves a remarkable turnover frequencies (TOF) value of 1.24 × 10-3 s−1 in HDS reaction of dibenzothiophene (DBT). This dual anchoring method based on POMs inorganic ligand and organic chelator ligand provides a new idea for designing novel HDS catalysts.

CoMo supported on calcined (MeFeAl) tertiary hydrotalcites (Me2+: Co2+, Ni2+, Mg2+ or Zn2+) for dibenzothiophene hydrodesulfurization reaction

Se sintetizaron cinco hidrotalcitas terciarias conteniendo dos cationes trivalentes: Fe3+ y Al3+, y un catión divalente Mg2+, Co2+, Ni2+ o Zn2+. Se mantuvo una proporción molar [M+3/(M3++M2+)] de 0,22 y una proporción molar de [Fe3+/Al3+] de 0,66; con la excepción de la hidrotalcita MgFeAl cuya proporción fue duplicada a 1,32. Los óxidos de estas hidrotalcitas fueron usados como soportes de la fase activa (Mo) promovida con Co. Hidrotalcitas, óxidos mixtos y sus precursores catalíticos fueron caracterizados por las técnicas de: análisis químico por fluorescencia de rayos X, medidas de superficie, difracción de rayos (DRX), desorción a temperatura programada (TPD-CO2), análisis elemental (C y S) y microscopía electrónica de transmisión de alta resolución. Todos los precursores catalíticos fueron probados en la reacción de hidrodesulfuración de dibenzotiofeno mostrando el siguiente orden de actividad: CoMo/γAl2O3 > CoMo/MgFeAl(0,66)> CoMo/MgFeAl(1,32)> CoMo/CoFeAl> CoMo/NiFeAl> CoMo/ZnFeAl. La actividad catalítica y la selectividad hacia la formación de productos de hidrogenación con respecto a la desulfuración directa (HID/DSD) se incrementó a medida que se incrementó la basicidad del catalizador. Estos resultados fueron asociados con la fracción de Mo (fMo) y la naturaleza del soporte. Es importante mencionar que los catalizadores: CoMo/MgFeAl(0,66) y CoMo/MgFeAl(1,32) mostraron la más alta selectividad hacia la ruta de hidrogenación comparado con el catalizador de referencia (CoMo/γ- Al2O3). Adicionalmente, la actividad del catalizador CoMo/MgFeAL(0,66) hacia la ruta de HID fue la más alta, inclusive superando la actividad del CoMo/γ-Al2O3.

Hydrodesulfurization of Dibenzothiophene over Ni-Mo-W Sulfide Catalysts Supported on Sol-Gel Al2O3-CeO2.

To achieve sulfur content in gas oil at a near-zero level, new catalysts with improved hydrogenation functions are needed. In this work, new Ni-Mo-Mo hydrodesulfurization (HDS) catalysts supported by Al2O3-CeO2 materials were synthesized to evaluate their efficiency in the reaction of HDS with dibenzothiophene (DBT). Al2O3-CeO2 supports different CeO2 loadings (0, 5, 10 and 15 wt.%) and supported NiMoW catalysts were synthesized by sol-gel and impregnation methods, respectively. The physicochemical properties of the supports and catalysts were determined by a variety of techniques (chemical analysis, XRD, N2 physisorption, DRS UV-Vis, XPS, and HRTEM). In the DBT HDS reaction carried out in a batch reactor at 320 °C and a H2 pressure of 5.5 MPa, the sulfide catalysts showed a dramatic increase in activity with increasing CeO2 content in the support. Nearly complete DBT conversion (97%) and enhanced hydrogenation function (HYD) were achieved on the catalyst with the highest CeO2 loading. The improved DBT conversion and selectivity towards the hydrogenation products (HYD/DDS ratio = 1.6) of this catalyst were attributed to the combination of the following causes: (i) the positive effect of CeO2 in forcing the formation of the onion-shaped Mo(W)S2 layers with a large number of active phases, (ii) the inhibition of the formation of the undesired NiAlO4 spinel phase, (iii) the appropriate textural properties, (iv) the additional ability for heterolytic dissociation of H2 on the CeO2 surfaces, and (v) the increase in Brønsted acidity.

V-Containing Heteropoly Acids with Keggin Structure as Precursors of Sulfide Catalysts: Regularities of the Convertion of Dibenzothiophene and Naphthalene on Nonpromoted Mo–V Catalysts

Mixed PMoV heteropoly acids with Keggin structures H3+xPMo12–xVxO40 (x = 1–6) and modified sulfide catalysts on their basis were synthesized, their physicochemical characteristics were determined, and their performance in the reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation of naphthalene was evaluated. Modification of the Mo-containing catalysts with vanadium by impregnation with a solution of mixed heteropoly acids was found to enhance their catalytic activity in the studied reactions, as well as to increase the selectivity for the direct hydrodesulfurization route of the DBT HDS reaction.

Bimetallic CoMo Nanoparticles Supported over Carbon-Zeolite Composites as Dibenzothiophene Hydrodesulfurization Catalyst

Cobalt molybdenum catalysts supported on novel activated carbon-HZSM-5 composites with different mass ratios were prepared by wet-impregnation method and pre-sulfided by CS2. Characterization of these catalysts was done using X-ray powder diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption, and scanning electron microscope analytics. Their activity for the hydrodesulfurization reaction of dibenzothiophene was investigated at atmospheric pressure in the temperature range of 250–400 °C using the fixed-bed reactor with 0.5 g of each powder and pre-sulfided with CS2. The highest conversion of dibenzothiophene at the temperature range of 300–400 °C was obtained for the CoMo/activated carbon-HZSM-5(1:1) catalyst. The best selectivity for cyclohexylbenzene, which is the dominant product according to gas chromatography results, was obtained at all temperatures using CoMo/activated carbon-HZSM-5(3:1) catalyst. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Synthesis of Few Layer Amorphous 1T/2H MoS2 by a One-Step Ethanol/Water Solvothermal Method and Its Hydrodesulfurization Performance

Few layer (< 5 layers) MoS2 mixed with a 1T phase has the characteristics of a large specific surface area and an improved active site distribution. Therefore, it has been increasingly study for the catalytic hydrodesulfurization of polycyclic compounds. In this paper, few-layer MoS2 with a high proportion of the 1T phase is synthesized by a one-step solvothermal method using a green non-toxic ethanol/water solvent. Results show that few-layer MoS2 (3–5 layers) with a 1T phase up to 48% can be synthesized in a 50% ethanol solvent. This MoS2 is used to catalyse the hydrodesulfurization reaction of dibenzothiophene, and the target product conversion rate reaches 84.2%. Among them, biphenyl accounts for 70.2%, phenylcyclohexane accounts for 13.9%, and bicyclohexane accounts for 0.4%. According to the Hansen solubility parameter (HSP) distance Ra, the effects of solvents on the structure and morphology of MoS2 and the conversion of dibenzothiophene hydrodesulfurization are determined. This work is significant for the synchronous synthetic exfoliation of MoS2 with a controllable number of layers, a higher ratio of the 1T phase and good catalytic HDS of polycyclic compounds. Few layers and high proportion of 1T phase MoS2 by solvothermal synthesis for catalytic hydrodesulfurization of dibenzothiophene.

Kinetics of dibenzothiophene hydrodesulfurization reactions using CoMoP/Al2O3 and NiMoP/Al2O3

Over the last decades, the regulatory agencies, aiming to limit vehicle emissions, established more stringent fuel specifications, including ultra-low sulfur contents in diesel and gasoline. In such way, hydrodesulfurization (HDS) is a key process in the oil refining scheme for producing low sulfur fuels. The evaluation of the HDS reaction kinetics of refractory compounds, as dibenzothiophene (DBT), is an important tool in the search for improving the activity of usual industrial catalysts. In this context, the main objective of this work was the estimation of kinetic parameters of DBT HDS reactions using CoMoP/Al2O3 and NiMoP/Al2O3 catalysts at operational conditions which provide a wide range of DBT conversions. The estimation results were evaluated using statistical tests as t-Student and chi-square. Good fits to the evaluated experimental data were provided by two power-law models with different levels of detail: one considering the global DBT conversion only and the other considering a reactional scheme with two parallel routes (direct desulfurization to biphenyl and hydrogenation to cyclohexylbenzene). The apparent activation energies found were of the order of 90 to 100 kJ mol−1. Regarding the biphenyl hydrogenation to cyclohexylbenzene, the parameter estimation was hindered because this reaction is expected to be significant at conditions with high DBT conversions only.

Synergistic effect of acidity and active phases for NiMo catalysts on dibenzothiophene hydrodesulfurization performance

Serial Al-Ti-SBA-16 materials with highly ordered degree were successfully synthesized by a simple two-step method. The characterization results showed that incorporation of Al and Ti atoms into SBA-16 silica could obtain the supports with different acidities and modulate the distribution and dispersion of active phases for NiMo catalysts. The dibenzothiophene (DBT) hydrodesulfurization (HDS) evaluation results disclosed that the synergistic effect of enhancing acidity and properties of active metals could significantly improve the HDS performance. Importantly, it was the first time that the ratios of S-edge and Mo-edge concentrations were found to be well linked with the hydrogenation pathway (HYD)/direct desulfurization pathway (DDS) ratios. The HDS result showed that the acidity of S-H groups in S-edge sites could be promoted by B acid and further facilitated the DDS selectivity. As the Al and Ti contents in the support were 7.5% and 2.5% respectively, the NiMo/AT-7.5 catalyst exhibited the highest HDS performance due to its appropriate acidity, highest proportion of MoS2 phase and concentration of S-edge sites with high efficiency. Finally, the kinetic and thermodynamic analyses were applied to investigate the intrinsic HDS reactivity for various catalysts. The results confirmed the existence of synergistic effect in the DBT HDS reaction. It was also discovered that the B acid sites could further increase the desulfurization route (DS) of THDBT to CHB. In addition, the S-edge/Mo-edge ratio and kDDS/kHYD could also be well linked.

Ni2P/Al2O3 hydrodesulfurization catalysts prepared from hypophosphite under a nitrogen atmosphere

A novel method for preparing Ni2P/Al2O3(L) catalysts in an N2 atmosphere by decomposition of hypophosphites was proposed, and Ni2P/Al2O3(T) catalyst was synthesized by the temperature programmed reduction method in a H2 atmosphere for comparison. These prepared catalysts were washed with deionized water to remove impurities. The X-ray diffraction, N2-adsorption specific surface area measurements, CO uptake, and X-ray photoelectron spectroscopy were applied to characterize these catalysts. The activities of the Ni2P/Al2O3 catalysts prepared with the two different methods were tested in the dibenzothiophene hydrodesulfurization reaction.

Study of the impregnation of NiMo assisted by chelating agents for hydrodesulfurization-supported catalysts over mesoporous silica

Abstract

Synthesis and characterization of mechanically activated bulky molybdenum sulphide catalysts

Bulky catalysts on the basis of MoS 2 nano-crystallites have been obtained for the first time from commercial molybdenite in one-step synthesis using mechanical-chemical treatment with small additives of polar liquids. Physical and chemical properties of the synthesized catalysts were studied using sedimentation analysis, XRD, XPS, TEM and thermal analysis. The catalytic activity of the catalysts was examined in the course of dibenzothiophene hydrodesulphurization followed by the GC–MS analysis of the reaction products. Correlations between the catalytic activity and the methanol quantity added in the course of mechanical-chemical activation were established. The pathways of dibenzothiophene hydrodesulfurization reactions over the synthesized catalysts were proposed. Pour la première fois, des catalyseurs massiques à base de nano-crystallites MoS 2 ont été synthétisés à partir de molybdénite commerciale par activation mécanique en phase solide en une étape. Des liquides polaires ont été aussi additionnés en petites quantités comme adjuvants. Les propriétés physicochimiques des catalyseurs synthétisés ont été caractérisées par analyses par sédimentation, radiocristallographique et thermique, ainsi que par microscopie électronique à transmission et spectroscopie photoélectronique par rayons X. Les activités des catalyseurs dans une réaction modèle d’hydrogénolyse du dibenzothiophène ont été mesurées par analyse GC–MS. La corrélation entre l'activité catalytique et la quantité de methanol ajoutée au cours de l’activation mécano-chimique a été déterminée et discutée. Des hypothèses ont été émises sur les chemins réactionnels de l'hydrogénolyse des dibenzothiophènes à l’aide des catalyseurs synthétisés.

Comparison of Mo/MgO and Mo/γ-Al2O3 catalysts: impact of support on the structure and dibenzothiophene hydrodesulfurization reaction pathways

The MgO and P2O5-promoted γ-Al2O3 supports with alkaline and acidic natures, respectively, were prepared, impregnated with Mo atoms, and compared for dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction. Ultraviolet spectroscopy and the principal component analysis were used to identify the impact of the supports on the reaction pathways. The catalysts were characterized by BET surface analysis, X-ray diffraction, temperature-programmed reduction, Fourier transform infrared, and X-ray photoelectron spectroscopy. The γ-Al2O3-supported catalyst favors the hydrogenation pathway relative to the MgO-supported catalyst, which facilitates the direct desulfurization route. The different performance was attributed to the dissimilar Mo phases that emerged during the activation procedure. The activation under sulfo-reductive condition changed the Mo atoms on γ-Al2O3 support into the sulfide phase while extra oxidation took place for the MgO-supported catalyst. The migration and consumption of loosely bonded bulk oxygen atoms with under-coordinated Mo atoms on the MgO support were introduced as a possible reason for such extra oxidation. DFT calculations predicted an interaction between the Mo/MgO catalyst and DBT via the electron donation from the catalyst oxygen atoms to the aromatic rings, resulting in weakening and breaking of the C–S bonds. In spite of the higher resistance of the MgO-supported catalyst toward coking and its superior activity, its lower hydrogenation capability suggested using a dual-function catalyst. Accordingly, two catalysts were mixed and the synergism was observed in the HDS reaction of thiophene.

Catalytic performance of CoMo/Al2O3-MgO-Li(x) formulations in DBT hydrodesulfurization

In this work, it is reported the catalytic performance of low acidity catalysts in the hydrodesulfurization reaction of dibenzothiophene. Catalytic CoMo formulations supported on materials based on Al2O3-MgO modified with several amounts of lithium oxide (x=1, 5 and 10wt.% of Li2O) were used. It was correlated the effect of the atomic lithium content on the dispersion of the Mo and Co phases in their oxidized and sulfided forms, in order to explain their catalytic performance. Elemental chemical composition on the catalyst surface as well as sulfurization degree and the interaction of sulfided Co and Mo phases with the support were determined by X-ray photoelectron spectroscopy (XPS). Textural properties were measured by N2 physisorption technique; the identification of the crystalline phases was studied by X-ray powder diffraction (XRD) and Raman spectroscopy (RS). The chemical coordination state was determined from diffuse reflectance spectroscopy (DRS) measurements. Reducibility was determined by temperature programmed desorption (TPR). Dispersion of MoS2 crystallites was revealed by high resolution transmission electron microscopy (HRTEM). Catalytic activity of the formulations was evaluated using a pressurized batch reaction system through the hydrodesulfurization reaction of dibenzothiophene as a model molecule, selectivity toward direct desulfurization reaction route was studied following the biphenyl and cyclohexylbenzene reaction products identified by using gas chromatography; results show that there is an optimal amount of 3.7 at.% of Li, which maintains hydrodesulfurization function and decrease the hydrogenation function compared to the conventional CoMo catalyst.

Binary γ-Al2O3–α-Ga2O3 as supports of NiW catalysts for hydrocarbon sulfur removal

A series of γ-Al2O3–α-Ga2O3 binary mixed supports with different Ga2O3 content (labeled AlGa-x, where x is the wt.% of Ga2O3) were synthesized by a one-step precipitation method and calcination. These supports were used to prepare NiW catalysts and later tested in the hydrodesulfurization (HDS) reactions of gasoline and diesel model sulfur compounds. Morphology, surface and electronic properties of AlGa-x samples changed considerably depending on Ga2O3 content. Amorphous alumina and low gallium oxide content samples showed higher WS2 dispersion when compared with the gallium-free sample by HRTEM analysis. All materials displayed excellent catalytic activity in the 3-methyl-thiophene (3MT) and dibenzothiophene HDS reactions. The best catalytic performance for both tests was obtained with the NiW/AlGa-25 sulfided catalyst. Furthermore, hydrogenation capacity was clearly modified by the presence of GaAl2O4 spinels as well as α-Ga2O3. In the 3MT HDS reaction, the presence of isoprene among the reaction products showed that, using the NiW/AlGa-x catalyst, this reaction may be successfully conducted by the desulfurization pathway. Noteworthy was the formation of well-defined microcrystals in samples with the highest gallium oxide content. Results from this work reveal that the binary γ-Al2O3–α-Ga2O3 mixed oxides have great potential as support for hydrocarbon sulfur removal catalysts.

Effect of the divalent metal and the activation temperature of NiMoW and CoMoW on the dibenzothiophene hydrodesulfurization reaction

α and β trimetallic mixed oxides were obtained from ϕy layered phase precursors with (NH4)H1.4Ni2.3O(OH)(MoO4)1.4(WO4)0.6 and (NH4)H2Co2O(OH)(MoO4)1.6(WO4)0.4 formulas by calcination at temperatures as low as 673K. At this temperature, phase transition was confirmed by (TGA and DSC) thermal analysis. Oxides were activated ex-situ under a H2S/H2 (15%, v/v) mixture at two temperatures: 673K and 798K, to obtain metal sulfides phases, which were active catalysts in the hydrodesulfurization reaction of dibenzothiophene. The effect of the (Ni, Co) promoter and the activation temperature were studied to know the behavior and adequate activation conditions. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H2-TPR) provided useful information about the oxidation states of the metallic species in the mixed oxides, which were related to the catalytic activity in the hydrotreating reaction. Sulfided catalysts were also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for understanding their textural and morphological differences. Additional characterization was carried out using BET surface area and elemental analysis. All catalysts were tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 593K and 5.5MPa. The best catalytic behavior was obtained using Ni as promoter, activated at 798K. Nickel catalysts were more hydrogenating than cobalt catalysts.

Role of Cs on Hydrodesulfurization Activity of RuS2 Catalysts Supported on a Mesoporous SBA-15 Type Material

RuS2-Cs catalysts supported on SBA-15 type mesoporous materials for hydrodesulfurization (HDS) of dibenzothiophene (DBT) were synthesized. The influence of cesium content and sulfiding temperature (500 and 600 °C), as well as the cesium precursor salt employed (cesium hydroxide and cesium chloride), was studied. The quantity of ruthenium was maintained constant while the amount of cesium variable, with Cs/Ru molar ratios of 0.1:1, 0.5:1, and 1:1. The support, precursors, sulfided, and spent catalysts were characterized by X-ray diffraction (XRD), N2 adsorption−desorption isotherms at −196 °C, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) analysis, H2-TPRS, TPO, and DRIFT spectra of adsorbed NO. The catalytic properties of these materials were tested between 260 and 440 °C in the HDS of DBT under a hydrogen pressure of 3.0 MPa. The obtained results reveal that in mesoporous materials, the presence of cesium induces the agglomeration of the RuS2 active phase, that is, the lower the cesium content the better the RuS2 dispersion. In this sense, the catalysts with the lowest amount of Cs present the best catalytic results and at lower reaction temperatures. In terms of selectivity, the presence of Cs leads the DBT HDS reaction toward the direct desulfurization route (DDS) with a selectivity to biphenyl (BP) close to 100%. The cesium precursor salt employed did not modify the dispersion of Ru phase in the Cs-Ru/SBA-15 catalysts but affected the sulfur lability of the catalyst.

Effect of gallium as an additive in hydrodesulfurization WS2/γ-Al2O3 catalysts

Abstract The effect of gallium in W/Ga(x)–γ-Al2O3 catalysts was investigated in the hydrodesulfurization of dibenzothiophene. The γ-Al2O3 carrier was modified by the gallium addition prior to W impregnation and further calcination at 723 K. An electrophoretic study was carried out on the calcined Ga samples at 0, 0.29, 0.55, 0.84, 1.09, 1.43, 1.71 and 2.22 wt.% of Ga and it indicated that Ga addition affected significantly the surface of alumina. The presence of at least two gallium species was proposed, at low gallium content GaAl2O4 species decreased the isoelectric point (IEP) and probably the formation of Ga2O3 at higher contents increased again the IEP. Raman spectroscopy showed that the gallium incorporation had a strong effect in the formation of WOx species at the surface of catalysts. The highest amount of irregular WOx particles calculated by the Raman (O W O + W O)/W–O–W band intensities ratio was found on the W/Ga(1.09)–γ-Al2O3 catalyst. The presence of gallium induced higher activity on the dibenzothiophene hydrodesulfurization reaction in all catalysts tested. The highest Raman ratio and the highest activity were found for the W/Ga(1.09)–γ-Al2O3 catalyst, suggesting that better dispersed W species could be responsible for the highest HDS activities.

Synthesis and characterization of WO3 and WS2 hexagonal phase nanostructures and catalytic test in sulfur remotion

The aim of the present study was the synthesis and characterization of WO3 and WS2 nanostructures in hexagonal phases and the evaluation of the latter as catalyst in the dibenzothiophene hydrodesulfurization reaction. 2H-WS2 nanostructures were obtained from a precursor WO3 nanostructure by a two-step hydrothermal/gas phase reaction under well-controlled conditions. All nanostructures were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and the specific surface area of the materials was measured using the BET method. The catalytic activity and selectivity measurements of the resulting unsupported WS2 nanocatalysts are also presented. Catalytic activity was found to be highest for the 2H-WS2 from the WO3 nanostructure sulfided at 773 K (rate constant of 3 × 10−7 mol/g s).

Preparation and Characterization of SBA-15 Supported Cobalt–Molybdenum Sulfide Catalysts for HDS Reaction: An All Sulfide Route to Hydrodesulfurization Catalysts

MoS2 hydrodesulfurization (HDS) catalysts promoted with Co supported on SBA-15 were synthesized from sulfur-containing Mo sources [ammonium thiomolybdate (ATM), and tetramethylammonium thiomolybdate (TMATM)] and Co complexes cobalt dimethylthiocarbamate by using different synthesis strategies in order to achieve active catalysts. The (Co)-MoS2/SBA-15 catalysts were characterized with X-ray diffraction, N2-physisorption and High-Resolution Transmission Electron Microscopy. The catalytic performance in the HDS reaction of dibenzothiophene was examined at T = 623 K and P H2 = 3.4 MPa. The results of the experiments suggest that the sequence of impregnation steps has no significant influence on the HDS activity. On the other hand, the use of different thiomolybdate precursors significantly affects the catalytic activity. The catalysts derived from TMATM show lower HDS activities compared to the catalysts synthesized from ATM which is probably due to the presence of pronounced pore blocking as well as the generation of big needle-like aggregates of the Co–MoS2 phase. It seems that the formation of intermediate MoS3 is not a prerequisite for the generation of catalytic active CoMoS phases. The high activity and high selectivity for the direct desulfurization pathway of catalysts prepared with ATM despite the large MoS2 stacking could be due to the generation of a large number of coordinately unsaturated sites. Cobalt promoted molybdenum sulfide catalysts supported on mesoporous SBA-15 were prepared by an all sulfide route using sulfur-containing Mo and Co complexes. High catalytic activity at high Mo loading is observed for Co–MoS2/SBA-15 catalysts derived from ammonium thiomolybdate despite a pronounced stacking of MoS2 slabs. The catalysts prepared with tetramethylammonium thiomolybdate show lower HDS activities probably due to a pronounced pore blocking as well as the generation of big needle-like aggregates of the Co–MoS2 phase. The sequence of impregnation steps has no significant influence on the HDS activity. It seems that the occurrence of intermediate MoS3 is not necessary for the generation of catalytic active Co–MoS phases.