Hydrodesulphurization Research Articles

Effect of alumina–titania supports on the activity of Pd, Pt and bimetallic Pd–Pt catalysts for hydrorefining applications

A series of Pd, Pt and bimetallic Pd:Pt (4:1) based catalysts were supported on various alumina–titania mixed oxides. Their catalytic properties were probed on the thiophene hydrodesulphurisation (HDS). The supports were synthesised by the sol–gel method to obtain bulk mixed oxides. The Pd catalysts were tested in reduced and sulphided state, where the sulphided catalysts showed higher activity. While sulphided Pd increased its activity with titania content in the support, sulphided Pt proved to be more active when supported on the mixed oxide with the lowest titania concentration. The bimetallic catalysts presented the highest activity when supported on equimolar alumina–titania. A dependence of the deactivation rates with titania concentration in the mixed-oxide supports was detected for Pd and Pd–Pt bimetallic catalysts. On the other hand, almost no effect of the support composition on the Pt/alumina–titania deactivation rates was observed. The bimetallic catalyst activity and deactivation rates resemble closely those of the Pd monometallic catalysts suggesting a stronger influence of Pd on the performance of the bimetallic systems.

Structure and catalytic properties of molybdenum sulfide nanoplatelets

Abstract A nanostructured form of molybdenum disulfide/dioxide was prepared by a two-step hydrothermal/gas phase reaction carried at high-temperature sulfidation of molybdenum in H 2 S/H 2 for 2 h. The material was composed of a solid MoO 2 core with MoS 2+ x crystallites nucleating on its surface. Most of the MoS 2+ x have the shape of a single stacked platelet, which are 12–30 nm long and are about one MoS 2 unit cell wide. High-resolution electron microscopy (HREM), energy-dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM), in high-angle annular dark-field (HAADF). Electron diffraction (EDX) in the transmission electron microscope and X-ray diffraction were used to characterize the structure of the catalysts. It is found that the sample consists of MoS 2+x nanoplatelets with unit cell thickness which are exfoliated and are free to rotate along the basal plane. In addition, the edges of the platelets become very rough increasing the number of adsorption sites. The structure–catalytic properties of MoS 2+ x for hydrogenation over sulfur removal were observed in the hydrodesulphurization (HDS) reaction of dibenzothiophene (DBT). It was found that nanoplatelets have a very high catalytic activity for HDS. The number of adsorption sites is incremented by the presence of steps and kinks at the edges of the nanoplatelets.

HDN and HDS of model compounds and light gas oil derived from Athabasca bitumen using supported metal phosphide catalysts

Abstract Co0.4Ni2P and Ni0.3MoP catalysts, supported on Al2O3, fluorinated Al2O3 (Al2O3-F) and Mobil Catalytic Material (MCM-41), have been prepared from metal phosphate precursors by temperature-programmed reduction (TPR) to 1200 K. The catalysts have been characterized and their activity determined for the hydrodenitrogenation (HDN) of carbazole, the hydrodesulphurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the HDN and HDS of a light gas oil (LGO) derived from Athabasca bitumen. The formation of metal phosphides after TPR was confirmed by both X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The acidity of the catalysts, as measured by n-propylamine uptake, was determined by the support acidity and increased in the order Al2O3

Deactivation patterns of Mo/Al 2O 3, Ni–Mo/Al 2O 3 and Ni–MoP/Al 2O 3 catalysts in atmospheric residue hydrodesulphurization

In the present work, a comparative study on the deactivation behavior of three types of industrial hydrotreating catalysts, namely, Mo/Al 2O 3, Ni–Mo/Al 2O 3 and Ni–MoP/Al 2O 3, that are used to promote primarily hydrodemetallization (HDM), hydrodesulphurization (HDS) and hydrodesulphurization + hydrodenitrogenation (HDS/HDN) reactions, respectively, in the first, second and third reactor of commercial atmospheric residue desulfurization (ARDS) units was carried out. The main objective of the study was to contribute to a better understanding of the relationship between catalyst type and catalyst deactivation patterns. The used catalysts from these experiments were fully characterized to determine the extent and the cause of deactivation. Special emphasis was paid to understanding the nature of the coke and metal deposition on the used catalysts by applying chemical analysis and various advanced analytical techniques, such as solid-state carbon-13 nuclear magnetic resonance spectroscopy ( 13C NMR), temperature-programmed oxidation (TPO), electron probe micro-analysis (EPMA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The results are discussed scientifically based on the physico–chemical properties of the three catalysts.

Influence of the preparation method on the activity of phosphate-containing CoMo/HMS catalysts in deep hydrodesulphurization

Abstract Phosphate-containing hexagonal mesoporous silica (P/HMS) materials were used as supports of hydrotreating CoMo catalysts. Two series of catalysts were prepared by sequential and simultaneous impregnation of P/HMS substrates with cobalt and molybdenum salts solutions. Both bulk and surface structures of calcined and sulphided samples were determined by several techniques (SBET, XRD, UV–vis, TPD-NH3, TPR, FTIR of adsorbed NO and pyridine, HRTEM and XPS). The activity of P-containing CoMo catalysts was examined in hydrodesulphurization (HDS) of dibenzothiophene (DBT) and compared to that of a conventional commercial CoMo/Al2O3 catalyst. It was found that the dispersion of oxide and sulphide Co and Mo species depends on the presence of phosphate and also on the sequence of Co and Mo incorporation being co-impregnation more favourable than sequential impregnation. HRTEM analysis of sulphided samples (673 K) showed that larger stacking degree of MoS2 phase and better dispersion of Co and Mo species are achieved by co-impregnation. Activity tests revealed that sequential incorporation of Mo and Co is less effective for S-removal from DBT than co-impregnation. Contrary to sequential impregnation, the presence of P2O5 (up to 1.5 wt.%) on support surface enhanced S removal from DBT on the catalysts prepared by co-impregnation but the selectivity in this reaction was not influenced by phosphate and catalyst's preparation method. A close parallelism between active phase surface exposure and catalytic response was found.

Effect of Asphaltene Contained in Feed on Deactivation of Maya Crude Hydrotreating Catalyst

The effect of asphaltene contained in Maya heavy crude on the deactivation is studied. Different heavy feeds are prepared by the mixing of Maya with desulfurized diesel. A standard NiMo catalyst is used in a batch reactor to evaluate hydrodemetallation (HDM), hydrodesulphurization (HDS), and asphaltene (HDAsp) conversion. Textural properties of the spent catalysts are studied by pore size distribution and x-ray diffraction (XRD). Metals and coke deposition on the deactivated catalysts are also measured. It is found that HDM and HDAsp activities decrease with increasing concentration of asphaltene in feed, whereas the opposite trend is observed in the case of HDS. Both deposits of coke and vanadium on the catalyst's surface increase with the concentration of asphaltene in feed. The presence of asphaltene is the main reason to decrease surface area and total pore volume and hence it causes deactivation.

HDS of thiophene over CoMo/AlMCM-41 with different Si/Al ratios

A series of AlMCM-41 molecular sieves with different Si/Al ratios were synthesized followed by the deposition of cobalt and molybdenum oxides on these mesoporous supports by co-impregnation. Such materials were further calcined and catalysts with 15 wt.% of cobalt and molybdenum and a Co/(Co + Mo) atomic ratio of 0.30 were obtained. These materials were characterized by X-ray diffraction (XRD), transmission electron microscopy and selected area electron diffraction (TEM/SAED), X-ray fluorescence (XRF), and nitrogen adsorption. Hydrodesulphurisation (HDS) of thiophene was carried out at 350 °C in a fixed bed continuous flow micro reactor coupled on line to a gas chromatograph. The main XRD peaks of MCM-41 phase were observed in all samples and peaks due to MoO3 and CoMoO4 phases were also identified from XRD results. It was found that the as-synthesized catalysts presented reasonable conversion results for HDS of thiophene, when compared to other supported catalysts. The main products of HDS of thiophene were H2S, isobutene, 1-butene, n-butane, 2-butene-trans, and 2-butene-cis. It was observed that the reactivity of the as-synthesized catalysts is a direct function of the Si/Al ratio, nature and concentration of the active species on the mesoporous supports.

Characterization and HDS activities of mixed Fe–Mo sulphides supported on alumina and carbon

Alumina and activated carbon-supported mixed sulphides (FeMoS) were prepared as hydrotreating catalysts. Previous work had shown bulk Fe–Mo mixed sulphides to be promising catalysts for hydrotreatment. Characterizations of the solids by NH3-TPD proved to be a good technique to classify the solids according to their acidic strength. Thiophene hydrodesulphurization (HDS) and High vacuum gas oil (HVGO) hydrotreatment, performed at atmospheric pressure and high pressure respectively, were used as catalytic tests. Depending on the support, a more or less important synergetic effect is observed. The results are in agreement with a possible direct desulphurization process. The acidic strength plays an important role in determining the hydrogenolysis/hydrogenation ratio of the catalysts.

Selective recovery of molybdenum from spent HDS catalyst using oxidative soda ash leach/carbon adsorption method

The petroleum refining industry makes extensive use of hydroprocessing catalysts. These catalysts contain environmentally critical and economically valuable metals such as Mo, V, Ni and Co. In the present study, a simple hydrometallurgical processing of spent hydrodesulphurization (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixture was investigated. Recovery of molybdenum was largely dependent on the concentrations of Na 2CO 3 and H 2O 2 in the reaction medium, which in turn controls the pH of leach liquor and the presence of Al and Ni as impurities. Under the optimum leaching conditions (40 g L −1 Na 2CO 3, 6 vol.% H 2O 2, room temperature, 1 h) about 85% recovery of Mo was achieved. The leach liquor was processed by the carbon adsorption method, which selectively adsorbs Mo at pH around 0.75. Desorption of Mo was selective at 15 vol.% NH 4OH. With a single stage contact, it was found possible to achieve >99%, adsorption and desorption efficiency. Using this method, recovery of molybdenum as MoO 3 product of 99.4% purity was achieved.

Hydrometallurgical processing and recovery of molybdenum trioxide from spent catalyst

Hydrometallurgical processing of spent hydrodesulphurisation (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixtures was investigated. The results indicated that the recovery of molybdenum was largely dependent on the concentrations of Na 2CO 3 and H 2O 2 in the reaction medium, which controls the acidity of the leach liquor and carry over of impurities such as Al, Ni, P, Si and V. Leaching process was exothermic and leaching efficiency of molybdenum decreased with increasing solid to liquid ratio. Large scale leaching of spent catalyst, under optimum conditions: 20% pulp density, 85 g/L Na 2CO 3, 10 vol.% H 2O 2 and 1 h reaction, resulted a leaching efficiency of 84% Mo. The obtained leach liquor contained (g/L): Mo — 22.0, Ni — 0.015 and Al — 0.82, P — 1.1, Si — 0.094 and minor quantities of V — 8 mg/L, As and Co — < 1 mg/L. Recovery of Mo from leach solution as MoO 3 of 97.30% purity was achieved by ammonium molybdate precipitation method.

Ni(Co)-Mo-W sulphide unsupported HDS catalysts by ex situ decomposition of alkylthiomolybdotungstates

Ni(Co)-Mo-W sulphide unsupported hydrodesulphurization (HDS) catalysts were prepared by ex situ decomposition of trimetallic (Ni-Mo-W) precursors. The precursors were synthesized by reaction of the tetraalkylammonium thiomolybdotungstates salts, (R 4N) 4MoWS 8 (where R = H, methyl, propyl) with an aqueous solution of Ni(Co)Cl 2·6H 2O in order to give molar ratios of Ni/[Ni + (Mo + W)] = 0.5 and Co/[Co + (Mo + W)] = 0.3. A new method by the ex situ activation was used. First, the precursors were treated in a stainless steel vessel of 45 mL volume at 523 K for 2 h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H 2S/H 2 (15 vol.% H 2S) from room temperature to 673 K, dwell of 2 h at 673 K. All catalysts were tested in the HDS of dibenzothiophene (DBT) and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET specific surface area measurements. The ex situ activation method used in this work leads to catalysts with a wide distribution of specific surface areas (from 11.4 to 60.6 m 2/g), mesoporous structure with pore size ranging from 18 to 45 Å and type IV adsorption–desorption isotherms of nitrogen, poorly crystalline structures with different morphology and high catalytic activities in the HDS of dibenzothiophene (DBT).

Effect of the hydrogen spillover on the selectivity of dibenzothiophene hydrodesulfurization over CoS x/γ-Al 2O 3, NiS x/γ-Al 2O 3 and MoS 2/γ-Al 2O 3 catalysts

Dibenzothiophene (DBT) hydrodesulphurization (HDS) reaction at 3 MPa and 325–375 °C on Mo/γ-Al 2O 3 single-bed and Me/γ-Al 2O 3//SiO 2//Mo/γ-Al 2O 3 (Me = Co or Ni) double-bed catalysts were investigated. Results indicate that ratio cyclohexylbenzene (CHB)/biphenyl (BP) or selectivity is higher when using double-beds rather than a single-bed. Synergy in dibenzothiophene hydrodesulphurization on Co//Mo and Ni//Mo double-beds is also detected. Changes in selectivity and conversion are attributed to the action of spillover hydrogen (Hso) formed in the first bed that reaches the second bed.

Synthesis of Ni–Mo–W sulphide catalysts by ex situ decomposition of trimetallic precursors

Nickel–molybdenum–tungsten sulphide unsupported catalysts were prepared by ex situ decomposition of trimetallic (Ni–Mo–W) precursors. The precursors were synthesized by impregnation of ammonium or tetraalkylammonium thiomolybdates on tungsten thiosalts (ammonium or tetraalkylammonium thiotungstates). Finally, the bimetallic precursors (Mo–W) were impregnated with Ni(NO 3) 2·6H 2O previously dissolved in water in order to give a final molar ratio Ni:Mo:W of 2:1:1. By the ex situ decomposition (activation), the precursors were transformed under a flow of H 2S (15%) in hydrogen from room temperature to 673 K at 4 K/min, dwell of 4 h at 673 K. All catalysts were tested in the hydrodesulphurization (HDS) of dibenzothiophene (DBT) and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM). Furthermore, the specific surface areas were measured using the BET method. The catalysts obtained present low specific surface areas, poorly crystalline structures with cavities and disordered structure and different catalytic activities in the HDS of DBT. The best HDS catalytic activity was shown by the sample labeled as NiMoW–H ( k = 13.4 × 10 −7 mol/g * s).

Effect of phosphorus addition on unsupported Ni–Mo–W sulfide catalysts prepared by the in situ activation of nickel/tetramethylammonium thiomolybdotungstate

The effect of phosphorus addition was studied during the synthesis of unsupported trimetallic Ni–Mo–W catalysts prepared by the in situ activation of nickel-containing tetramethylammonium thiomolybdotungstate during the hydrodesulphurization (HDS) of dibenzothiophene (DBT). The trimetallic Ni–Mo–W precursors were prepared by the reaction of tetramethylammonium thiomolybdotungstates salts, [(CH 3) 4N] 4MoWS 8, with NiCl 2 and H 3PO 4 at P/Mo molar ratio of 0, 0.1, 0.5 and 1.0. These precursors are named Ni/[(CH 3) 4N] 4MoWS 8, P 0.1/Ni/[(CH 3) 4N] 4MoWS 8, P 0.5/Ni/[(CH 3) 4N] 4MoWS 8 and P/Ni/[(CH 3) 4N] 4MoWS 8, to give C 1, C 1P 0.1, C 1P 0.5 and C 1P catalysts, respectively. Catalysts were characterized by nitrogen adsorption studies, TEM, EDX, SEM and XRD. The addition of phosphorus has a detrimental effect on the HDS of dibenzothiophene. Phosphorus led to a strong decrease in BET specific surface area (from 46.9 m 2/g for the C 1 catalyst to 14.3 m 2/g for the C 1P catalyst) due to a pore plugging phenomenon. X-ray diffraction showed that the structure of unsupported nickel–molybdenum–tungsten sulfide catalysts corresponds to a low-stacked and poorly crystalline 2H–MoS 2 or 2H–WS 2 structure. Phosphorus induces the formation of less-folded slabs without modifying the dispersion along the basal plane or the stacking degree. However, the main effect of phosphorus is to favor the segregation of nickel sulfide and the loss of the promotional effect. This phenomenon would probably result from the stronger interaction of Mo and/or W with P than with Ni during the in situ preparation of these trimetallic NiMoW catalysts.

Improved deep desulphurisation of middle distillates by a two-phase reactor with pre-saturator

Hydrodesulphurisation (HDS) of middle distillates is up to now performed in trickle bed reactors equipped with an expensive H 2-recycle. To meet future low S-limits, hydrotreating of already pre-desulphurised oils is needed. The H 2-supply is then far beyond what is chemically consumed. In addition, conventional three-phase HDS-reactors are generally problematic with respect to mass transfer, hydrodynamics, and therefore, scale-up. In this paper, an improved HDS-concept based on a two-phase reactor is discussed. The oil is thereby externally saturated with H 2 and only the liquid is passed over the fixed bed. This concept was proven by experiments with light fuel oils (582 and 2252 ppm S, CoMo-catalyst, 1–6 MPa, 330–400 °C, up to 100 days continuous operation). In addition, kinetic studies were done with model oil consisting of a mixture of n-dodecane and selected S-species such as di-, tri- and tetra-methyl-dibenzothiophenes. In case of the presented two-phase concept, the H 2-recycle is redundant, the intrinsic reaction rate can be utilised (and accurately measured), and scale-up problems do not occur.

Influence of the presence of Al&lt;SUB align=right&gt;2O&lt;SUB align=right&gt;3 on Ni-Mo-W trimetallic catalysts for HDS

This work presents Ni-Mo-W tri-metallic catalysts of the type 'NEBULA', (Soled et al., 2001) bulk and supported, named NEBDMDS, NEB1 (5% Al2O3), NEB2 (25% Al2O3) and NEB3 (50% Al2O3). The materials were prepared from water-soluble ammonium salts by direct precipitation with nickel nitrate. Supported catalysts were synthesised obtaining a gel, which was aged, dried and calcinated. The precursors were sulphiding in a tubular furnace with a flow of DMDS (Dimethyl-disulphide)/N2. The generated catalysts were evaluated in the reaction of hydrodesulphurisation (HDS) of the dibenzothiophene (DBT). They were characterised by the adsorption of nitrogen using the Brunauer, Emmett and Teller (BET) method and Barrett Joyner and Halenda (BJH) method, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electronic Microscopy (TEM). The increase of the content of Al2O3 in the catalysts influenced on the decrease of the catalytic activity. The NEBDMDS catalyst presented the catalytic activity higher of 13.1 mol/s g.

Study of the effect of mechanical–chemical activation of Co–Mo/γ-Al 2O 3 and Ni–Mo/γ-Al 2O 3 catalysts for hydrodesulfurization

The effect of mechanical–chemical activation (MCA) of Ni(Co)–Mo catalysts, supported on γ-Al 2O 3 has been studied with respect to their phase composition, structure, catalytic activity and selectivity in the reaction of thiophene hydrodesulphurization (HDS). The mechanical-chemical treatment with a duration of 7 h has been accomplished with a planet-ball mill in air medium. The samples have been characterized by means of XRD, XPS, SEM and TPR prior to and after the MCA. The specific surface area and pore size distribution curves have been determined by recording of N 2 adsorption isotherms using BET method. The obtained results show that the HDS activity of the mechano-chemically-activated catalysts is considerably higher than their activity prior to this type of treatment. The applied mechanical–chemical activation caused a partial amorphization of the active components, deposited on the support, a decrease in the average particle size, separation and partial migration of the supported phase. The activation led to redistribution of the Mo 6+ ions on the surface, whereupon the share of the Mo 6+ ions, involved in the formation of the superficial Ni(Co)–Mo–O phase, became larger.

Effect of nitrogen removal from light cycle oil on the hydrodesulphurization of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene

Five light cycle oil feeds (LCO) with nitrogen contents ranging from 744.9 to 16.5 mg/L were prepared by removing organic nitrogen compounds gradually through adsorption on a silica column. These feeds were hydrotreated over a commercial Ni-Mo/Al 2O 3 catalyst to study the effect of nitrogen compounds on the hydrodesulphurization (HDS) of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. It was found that nitrogen compounds had the most negative impact on the HDS of 4- and/or 6-substituted dibenzothiophenes. The temperatures to achieve 50% HDS conversion were 5, 20 and 25 °C lower for dibenzothiophene, 4-methyldibenzothiphene and 4,6-dimethyldibenzothiophene, respectively, when the nitrogen content in the feed was reduced from 744.9 to 16.5 mg/L. Our results also revealed that, at lower temperatures, about 20% of the nitrogen compounds from the original light cycle oil were adsorbed on the catalyst's surface. The HDS of 4,6-dimethyldibenzothiophene was retarded until the HDN rate became greater than the adsorption rate, which might have freed some hydrogenation sites for adsorption. This phenomenon was not observed for the HDS of DBT. Our results suggest that nitrogen compounds and 4,6-dimethyldibenothiophene competed for the same type of active sites, and dibenzothiophene also could have been converted over a different site. In addition, the hydrodenitrogenation activity was also enhanced by the removal of nitrogen compounds. The experimental data was fitted to a Langmuir–Hinshelwood type of kinetic equation by assuming that the inhibition only affected the hydrogenation pathway.

Effect of sulfidation on Mo-W-Ni trimetallic catalysts in the HDS of DBT

This work presents the effect of different sulfiding agents on Mo-W-Ni trimetallic catalysts, such as “NEBULA” catalysts. The materials were prepared by direct precipitation of ammonium molybdate, ammonium tungstate and nickel nitrate, generating a trimetallic precursor designated NH 4-Ni-Mo 0.5W 0.5-O. Hydrogen sulfide (H 2S), dimethyl disulfide (DMDS) and dimethyl sulfide (DMS) in a hydrogen atmosphere were used to sulfide the precursor at 400 °C for 2 h. The NE B H 2 S , NEB DMDS and NEB DMS catalysts obtained were evaluated in the hydrodesulphurization (HDS) reaction of dibenzothiophene (DBT). DMDS and DMS are less polluting agents than H 2S, which is indeed a highly toxic compound. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, textural properties were measured using the BET and BJH methods. NE B H 2 S and NEB DMDS catalysts present similar catalytic activities for HDS, higher than NEB DMS. However, the latter catalyst was the most selective towards biphenyl (BF). NE B H 2 S and NEB DMDS catalysts were exposed twice to the HDS reaction, they presented an improvement in catalytic activity compared to the first catalytic test.

On the Performance of Metal Supported Catalysts Prepared by Microemulsion: Sol Gel and Precipitation of the Support Precursor

Ni/SiO2, NiMo/Al2O3 and CoMo/Al2O3 were prepared by microemulsion method. Precipitation and sol-gel of the support precursor allowed the synthesis of catalysts with differences in textural, structural and catalytic properties. The main difference between the precipitation and sol-gel microemulsion routes is the role of surfactant (Cetyltrimethyl Ammonium Bromide) in each synthesis method. The aggregation mechanism of support is modified by the synthesis route. There are differences in the catalytic performance of Ni/SiO2 microemulsion catalysts by the precipitation or sol-gel of support precursor. The hydrogenation of benzene, a low structure-sensitive reaction, showed that the precipitation 9%Ni/SiO2 microemulsion catalyst is more active than the sol-gel 9%Ni/SiO2 microemulsion catalyst. On other hand, these catalysts showed opposite result in the hydrogenation of C=C double bond of crotonaldehyde molecule. These results are indicative of the effects of nanostructured support and nanostructured active-phase in the hydrogenation activity. NiMo/Al2O3 and CoMo/Al2O3 catalysts prepared by sol-gel-microemulsion method were used in the hydrodesulphurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene. The HDS activity was improved as a function of metal content and it motivates the study of NiMo and CoMo microemulsion catalysts with higher contents of metals to enhance the HDS of 4,6-dimethyldibenzothiophene.