Molybdenum Species Research Articles

Extraction of molybdenum from acidic leach solution of Ni–Mo ore by solvent extraction using tertiary amine N235

ABSTRACTTertiary amine N235 diluted with sulphonated kerosene containing sec-octyl alcohol as a phase modifier was used to directly extract molybdenum from the acidic leach solution of Ni–Mo ore. The results indicated that the extraction of molybdenum can reach more than 88% using a solvent extraction system consisting of 10 vol.-% N235 and 10 vol.-% sec-octyl alcohol in sulphonated kerosene with an O/A ratio of 1:2 at room temperature for 20 min. The extracted molybdenum species of Mo7O21(OH)33–, MoO2(SO4)22– and MoO2(HSO4)42– in loaded organic phase were identified, and the predominant species was Mo7O21(OH)33–. Molybdenum in the loaded organic phase can be stripped with ammonia solution, and the stripping of molybdenum can reach 95.8% at an O/A ratio of 7:1, phase contact time of 10 min, and the ammonia concentration of 6 mol L−1.

Phosphorus modified MoO3–Bi2SiO5/SiO2 catalyst for gas-phase epoxidation of propylene by molecular oxygen

The phosphorus (P) modified MoO3–Bi2SiO5/SiO2 catalyst was prepared by a simple co-impregnation method and investigated in the epoxidation of propylene by molecular oxygen. The catalyst was characterized by X-ray diffraction (XRD), N2 adsorption–desorption analysis, NH3-temperature-programmed desorption (NH3-TPD), transmission electron microscopy, and Raman spectroscopy. It was found that the P-modified MoO3–Bi2SiO5/SiO2 catalyst with a P/Mo molar ratio of 0.5 exhibits the best catalytic performance for epoxidation of propylene by O2, the TOFs for propylene oxide (PO) formation was four times higher than that of the unmodified one at 633 K. The modification by P could promote the dispersion of MoO3 nanoparticles and increase the number of weak and moderate acid sites with respect to the phosphorus-free MoO3–Bi2SiO5/SiO2 catalyst, which were beneficial to the formation of PO. Moreover, the introduction of P also could protect the mesoporous structure by inhibiting the formation of Bi2Mo3O12, which was beneficial to the dispersion of active species. We suppose that the phosphorus, bismuth and molybdenum species of P-modified MoO3–Bi2SiO5/SiO2 catalyst play important roles for propylene epoxidation by molecular oxygen.

PH-dependent release of environmentally friendly corrosion inhibitor from mesoporous silica nanoreservoirs

Coatings for corrosion protection usually contain pigments that constantly release substances actively inhibiting corrosion. However, this constant leaching places an important limitation on the protection lifetime of the coating. An intelligent release system may improve the long-term function of a coating, as uncontrolled loss by leaching is inhibited. This ensures that high amounts of inhibitors are still present when needed. Furthermore, this is also favourable for the environment, as no inhibitor is unnecessarily released into it. In this sense, smart mesoporous systems are excellent candidates thanks to their ability to provide more efficient and longer lasting anticorrosive protection by responding quickly to external stimuli such as local environmental changes (temperature, pH, local defects, humidity, etc.). A change in pH is a particularly interesting stimulus since, as is well known, corrosion activity leads to local pH changes in cathodic and anodic areas.In the present paper an environmentally friendly corrosion inhibitor, sodium phosphomolybdate, has been loaded into mesoporous silica nanoparticles. One of the main goals has been to study whether this corrosion inhibitor compound can offer controlled release as a function of pH, even in the absence of encapsulation. The results have shown that the polymerisation processes experienced by molybdenum species, as well as the different phosphate ions present as a function of pH, prevent their release into the environment in the absence of an outer capsule within the pH 3–9 range, thus avoiding the need to carry out an encapsulation stage.

New solid oxo-rhenium and oxo-molybdenum catalysts for the deoxydehydration of glycols to olefins

Several new solid oxo-rhenium and oxo-molybdenum catalysts were tested for the deoxydehydration (DODH) of 1,2-diols to terminal olefins employing aromatic solvents and reaction temperatures of 150–200°C. A catecholato oxo-rhenium catalyst tethered to silica was prepared and found to have comparably high DODH activity to its soluble analog with triphenylphosphine as the reductant. Catalyst re-use and leach-test experiments show significant leaching into the liquid phase. Silica, ceria and, for the first time, alumina and iron oxide were tested as supports for perrhenate, with ceria producing the least active material in 1,2-decane diol DODH. Decene yields obtained with ReOx/SiO2, ReOx/Fe2O3, ReOx/Al2O3 were highest when triphenylphosphine was the reductant and reached 70−78% (at 90–100% conversion) at 150°C. These three catalysts were also effective with gaseous reductants H2 or CO. Leaching of rhenium species occurred for all supports and was most pronounced for SiO2. New solid oxo-molybdenum catalysts were synthesized. At 200°C, decene yields observed using MoOx/Fe2O3, MoOx/SiO2, MoOx/Al2O3, MoOx/TiO2 and MoOx/ZrO2 were comparable and did not exceed 20%. There were homogeneous contributions through leached molybdenum species.

Effect of potassium promotion on the structure and performance of alumina supported carburized molybdenum catalysts for Fischer-Tropsch synthesis

Fischer-Tropsch synthesis produces light olefins and long chain hydrocarbons from syngas generated from fossil and renewable feedstocks. Molybdenum carbide exhibits catalytic properties approaching those of metal catalysts in a number of hydrogenation reactions. The present paper focuses on the effect of promotion with potassium on the structure and performance of alumina supported carburized molybdenum catalysts in Fischer-Tropsch synthesis. Molybdenum carbide catalysts were synthesized by temperature programmed carburization in methane and hydrogen. Molybdenum was highly dispersed in both calcined and carburized alumina supported catalysts. Mixed oxides of potassium, molybdenum and aluminium were uncovered in the calcined promoted catalysts. These oxides are converted in molybdenum carbide species on their carburization. Potassium promotion strengthens interaction between molybdenum and aluminium. The potassium promoted catalysts exhibited higher selectivity to light olefins and long chain hydrocarbons but lower Fischer-Tropsch reaction rate compared to the unpromoted counterpart. The observed lower Fischer-Tropsch reaction rate on the promoted catalysts was attributed to more difficult carburization of the molybdenum species and electronic effects due to the presence of potassium. The light olefin and C5+ selectivities decrease at higher carbon monoxide conversion probably because of secondary olefin hydrogenation and hydrocarbon hydrogenolysis.

Effect of the support on the hydrodeoxygenation of m-cresol over molybdenum oxide based catalysts

The hydrodeoxygenation (HDO) of m-cresol was investigated over supported molybdenum oxide catalysts at 340°C under 4MPa as total pressure. All catalysts were fully characterized using several techniques such as atomic absorption, N2 physisorption, XRD, H2-TPR, NH3-TPD, Raman spectroscopy, TEM analysis and oxygen chemisorption. It was noted that the reducibility of molybdenum species depends on the support used and follows the same order than the one determined from the HDO activity, i.e. MoOx/Al2O3>MoOx/SBA–15>MoOx/SiO2. In addition, the use of an ordered mesoporous silica support (SBA-5) or an acidic support (Al2O3) favored significantly the dispersion of MoOx particles compared to SiO2.Under these experimental conditions, m-cresol transformation underwent through two parallel deoxygenation routes which involved either the direct CO bond scission leading to toluene (DDO route), or the total hydrogenation of the aromatic ring yielding mainly to a mixture of methylcyclohexene isomers (HYD route). Regardless of the support used, the DDO route was always predominant. A reaction mechanism was proposed to explain the formation of toluene, the main product observed from HDO of m-cresol. To explain the formation of this aromatic, a selective adsorption through the oxygen atom of the phenolic reactant on oxygen vacancies, acting as HDO active sites, was proposed.

Solvent Extraction of Molybdenum (VI) from Hydrochloric Acid Leach Solutions Using P507. Part I: Extraction and Mechanism

ABSTRACTThe extractant 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) was used to selectively extract molybdenum (VI) from the hydrochloric acid leach solution of molybdenite after roasting with lime. The effects of solution acidity, organic composition, extractant concentration, impurity concentration, temperature and phase volume ratio on the separation of molybdenum (VI) over impurities of iron (III), aluminum, silicon and phosphorus were investigated. The increase in solution acidity resulted in the depolymerization of molybdenum heteropolyanions and , and the formation of molybdenum cations of . The saturated loading capacity of molybdenum (VI) with 30% (v/v) P507 in sulfonated kerosene reached 44.5 g/L. More than 99.8% of the molybdenum (VI) was extracted in a four-stage counter current extraction using an organic system consisting of 30% (v/v) P507 and 70% (v/v) sulfonated kerosene and a hydrochloric acid leach solution containing 14.8 g/L Mo(VI) and 1.73 mol/L H+ with an A/O ratio of 2.86/1 at room temperature for 7 min, while the extraction of iron(III) and phosphorus was only 1.02% and 2.96%, respectively. The separation factor of molybdenum and impurities was in the range of 104.31 ~ 105.89. The extracted molybdenum (VI) species of Mo2O5A2·2HA in the loaded organic solution was identified by the combination of the slope and saturation methods, and further proved by the FTIR spectral analysis.

A Redox-anchoring Approach to Well-dispersed MoCx /C Nanocomposite for Efficient Electrocatalytic Hydrogen Evolution.

Here we report a redox-anchoring strategy for synthesizing a non-noble metal carbide (MoCx ) nanocomposite electrocatalyst for water electrolysis in acidic media, using glucose and ammonium heptamolybdate as carbon and Mo precursors, respectively, without the need of gaseous carbon sources such as CH4 . Specifically, the aldehyde groups of glucose are capable of reducing Mo6+ to Mo4+ (MoO2 ), and thus molybdenum species can be well anchored by a redox reaction onto a carbon matrix to prevent the aggregation of MoCx nanoparticles during the following carbonization process. The morphology and chemical composition of the electrocatalysts were well characterized by BSE-SEM, TEM, XRD and XPS. The obtained MoCx -2 sample showed a reasonably high hydrogen evolution reaction (HER) activity and excellent stability in an acidic electrolyte, and its overpotential required for a current density output of 20 mA cm-2 is as low as 193 mV. Such a prominent performance is ascribed to the excellent dispersity and nano-size, and the large reactive surface area of MoCx particles. This work may open a new way to the design and fabrication of other non-noble metal carbide nanocatalysts for various electrochemical applications.

Corrosion resistance improvement of nitinol by anodisation in the presence of molybdate ions

The corrosion behaviour of Nitinol (NiTi) alloy was studied in Ringer solution. In order to improve its corrosion resistance, protective films were formed on the NiTi surface by means of anodisation under potentiostatic or galvanostatic control in the presence of the corrosion inhibitor molybdate in alkaline and acidic solutions.The anodisation process reduces considerably the Ni content and increases the Ti content in the oxide film, indicating that the Ti/Ni stoichiometry in the outermost surface is much higher than in pure NiTi. The titanium enrichment on the outermost surface as TiO2 enhanced its anticorrosion performance, as was suggested by the decrease in the amount of Ni and Ti released in Ringer solution under open circuit potential (OCP) condition and under potentials where the bare substrate suffers pitting attack.The best anodised film in terms of corrosion protection was obtained under potentiostatic condition in alkaline solution. The presence of oxidised molybdenum species in the oxide potentiostatically grown in alkaline solution, generates a corrosion protective film with a smoother and denser surface than other oxides formed in acidic solutions, without any defects like micro-cracks or pores.

Anodisation of AZ91D magnesium alloy in molybdate solution for corrosion protection

We report the formation of a protective film on magnesium alloy AZ91D by means of anodisation under potentiostatic conditions in a molybdate solution. Results of the characterisation of the films by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are presented. The anodic film is mainly composed by magnesium oxides or hydroxides and molybdenum oxides. The corrosion protection performance of the coating was investigated in Ringer solution by monitoring the open circuit potential, polarisation techniques and electrochemical impedance spectroscopy (EIS). The coated electrodes exhibit significant corrosion protection properties due to the presence of molybdenum species in the film.

Insight into the structure and molybdenum species in mesoporous molybdena–alumina catalysts for isobutane dehydrogenation

The relationship of the structure and Mo species of mesoporous molybdena–alumina catalysts with isobutane dehydrogenation has been investigated.

DFT Study on the Interaction of Tris(benzene-1,2-dithiolato)molybdenum Complex with Water. A Hydrolysis Mechanism Involving a Feasible Seven-Coordinate Aquomolybdenum Intermediate.

In the present work, the reactivity of the tris(benzene-1,2-dithiolato)molybdenum complex ([Mo(bdt)3]) toward water is studied by means of the density functional theory (DFT). DFT calculations were performed using the M06, B3P86, and B3PW91 hybrid functionals for comparison purposes. The M06 method was employed to elucidate the reaction pathway, relative stability of the intermediate products, nature of the Mo-S bond cleavage, and electronic structure of the involved molybdenum species. This functional was also used to study the transference of electrons from the molybdenum center toward the ligands. The reaction pathway confirms that [Mo(bdt)3] undergoes hydrolysis, yielding dihydroxo-bis(benzene-1,2-dithiolato)molybdenum complex ([Mo(OH)2(bdt)2]) and benzenedithiol. The reaction takes place through seven transition structures, one of them involving an aquo seven-coordinate molybdenum intermediate stabilized by a lone pair (LP) LPO→LPMo hyperconjugative interaction. This heptacoordinate species allows understanding of the observed oxygen atom exchange between water and tertiary phosphines mediated by these complexes. Calculations also show that [Mo(C2H4S2)3] and [Mo(OH)2(C2H4S2)2] have d2 and d0 electronic configuration, and hence an electron pair must be transferred during the course of the hydrolysis. The frontier molecular orbital (FMO) analysis concludes that the electron pair is transferred in the rupture of the second Mo-S bond, from the occupied donating Mo dx2-y2 orbital to the unoccupied C2H4(SH)2 S-C σ* ligand orbital. This result is supported by the bond dissociation energy calculations, which demonstrate that the neutral dissociation of the second Mo-S bond is energetically the more favorable.

Optimization of the synthesis technique of molybdenum sulfide catalysts supported on titania for the hydrodesulfurization of thiophene

The present work deals with the optimization of the preparation method for the synthesis of unpromoted molybdenum catalysts supported on titania. Four methodologies have been followed: equilibrium–deposition–filtration (EDF), wet impregnation (WI), dry impregnation (DI) and controlled wet impregnation (CWI). The Mo surface density of all catalysts was 3.2 Mo atoms/nm2. The catalysts were characterized using N2 adsorption, XRD, XPS and DRS. The catalysts were evaluated in the hydrodesulfurization (HDS) of thiophene, using an atmospheric differential fixed bed reactor. EDF technique provided the most active catalyst followed by that prepared by WI and then by those prepared by DI or CWI. Although the impregnation technique does not influence the structure of the catalysts at nanoscale, a suitable choice of the impregnation technique leads to the increasing contribution of supported molybdenum clusters with small size and thus with high number of the Ti–O–Mo (Ti–S–Mo) bridges per Mo atom, stabilizing highly S-deficient structures. In order to confirm the favorable influence of titania on the catalytic performance, we have synthesized by DI a Mo catalyst supported on γ-alumina with the same loading. The relatively low activity exhibited by this catalyst was attributed to the different structure of the supported molybdenum species with respect to those formed on titania and to the lower Mo dispersion.

An Exceptionally Stable Metal-Organic Framework Supported Molybdenum(VI) Oxide Catalyst for Cyclohexene Epoxidation.

Molybdenum(VI) oxide was deposited on the Zr6 node of the mesoporous metal-organic framework NU-1000 via condensed-phase deposition where the MOF is simply submerged in the precursor solution, a process named solvothermal deposition in MOFs (SIM). Exposure to oxygen leads to a monodisperse, porous heterogeneous catalyst, named Mo-SIM, and its structure on the node was elucidated both computationally and spectroscopically. The catalytic activity of Mo-SIM was tested for the epoxidation of cyclohexene. Near-quantitative yields of cyclohexene oxide and the ring-opened 1,2-cyclohexanediol were observed, indicating activity significantly higher than that of molybdenum(VI) oxide powder and comparable to that of a zirconia-supported analogue (Mo-ZrO2) prepared in a similar fashion. Despite the well-known leaching problem of supported molybdenum catalysts (i.e., loss of Mo species thus causes deactivation), Mo-SIM demonstrated no loss in the metal loading before and after catalysis, and no molybdenum was detected in the reaction mixture. In contrast, Mo-ZrO2 led to significant leaching and close to 80 wt % loss of the active species. The stability of Mo-SIM was further confirmed computationally, with density functional theory calculations indicating that the dissociation of the molybdenum(VI) species from the node of NU-1000 is endergonic, corroborating the experimental data for the Mo-SIM material.

Benzothiophene hydrodesulfurization over NiMo/alumina catalysts modified by citric acid. Effect of addition stage of organic modifier

NiMo/Al2O3 catalysts were obtained by one-pot simultaneous impregnation of Mo, Ni and P (at 12, 3 and 1.6 wt%, respectively) over alumina. Citric acid (CA) was added (Ni/CA=1 mol ratio) to determine its influence over molybdenum species, as nickel precursor used was complexated Ni acetate. Three different preparation methodologies were used: (a) modification of calcined (400 °C) NiMo/Al2O3 by CA impregnation, (b) CA deposition directly onto Al2O3 carrier, prior to Ni-Mo-P impregnation, (c) simultaneous Ni-Mo-P-CA deposition on alumina support. Materials were characterized by N2 physisorption, infrared and UV-vis spectroscopies, temperature-programmed reduction and thermal analysis (TG-DTG), and tested in liquid-phase benzothiophene (BT) conversion in batch reactor. CA deposition over calcined NiMo/Al2O3 resulted in diminished proportion of refractory Mo6+(t) tetrahedral species but also in octahedral Mo6+(o) reducible at higher temperature, as to those over non-modified NiMo/alumina. That was reflected in lower hydrodesulfurizating (HDS) ability. The highest BT HDS activity (70% increase, as to the conventional calcined formulation with no organic additive) was found when CA was impregnated over bare alumina prior to Ni-Mo-P deposition. In that case, decreased interaction between deposited molybdenum and nickel species and the support was evidenced, that due to surface “passivation” from citric adsorption/decomposition on alumina surface. On the other hand, simultaneous Ni-Mo-P-CA deposition, where low pH of impregnating solution (pH~1.4) devoided citric acid ionization, (then, no Mo-citrate complex formation) was ineffective in providing catalyst of enhanced HDS activity.

Correlation between structure, acidity and activity of Mo-promoted Pt/ZrO2-TiO2-Al2O3 catalysts for n-decane catalytic cracking

A series of Pt/MoO3/ZrO2-TiO2-Al2O3 composite oxides with various MoO3 contents were prepared by incipient wetness impregnation method, and coated on the inner wall of stainless-steel microchannels. Catalytic cracking of n-decane (as model molecule of hydrocarbon fuel) over such monolithic catalysts were investigated under high temperature and high pressure conditions. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) and temperature programmed desorption of ammonia (NH3-TPD) techniques. The correlation between the catalytic performances of MoO3 modified catalysts and their structure as well as acidic property were observed. It was found that the conversion and heat sink of n-decane were obviously heightened compared with that obtained from thermal cracking. In particular, the catalyst which contains 7.0wt.% MoO3 exhibited the best catalytic cracking activity among the prepared catalysts, which is in well agreement with its highest amount of total acid sites and strong acid centers, along with the finely dispersed isolated and octahedral molybdenum species.

A Spectroscopic and Electrochemical Study of Molybdenum(IV) and Tungsten(IV) Species in Alkali Chloride Melts

Alkali chloride based melts can be employed as the working media for electrowinning and electrorefining refractory metals, including molybdenum and tungsten. In addition, chloride melts are suitable for manufacturing various items of these metals and recycling molybdenum and tungsten containing scrap. Knowing electrochemical properties and speciation of the metals of interest in the molten electrolyte is essential for designing a feasible process. Molybdenum and tungsten are the polyvalent metals and follow the general trend of increasing the lowest stable oxidation state in the high temperature chloride ionic media as one moves down the group from 3d to 5d transition metal. In the group 6 of the periodic table the lowest oxidation state of chromium in fused chlorides is +2, and this increases to +3 for molybdenum and +4 for tungsten. The oxidation state +4 is unusual for molybdenum in molten chlorides and the aim of the present study was finding the conditions of Mo(IV) species formation, determining their stability and comparing molybdenum(IV) and tungsten(IV) species behavior and electrochemical properties. The experiments were performed between 500–900 oC in the melts based on LiCl–KCl–CsCl, NaCl–KCl–CsCl and NaCl–CsCl eutectic mixtures. Anodic dissolution of metallic tungsten results in the formation of predominantly W(IV) ions. Increasing temperature causes slight increase of the average oxidation state of tungsten in the melt. The electrode potentials of tungsten were determined by potentiometry and the speciation characterized by electronic absorption spectroscopy measurements. Prolonged holding of tungsten-containing chloride melts in contact with silica results in partial oxidation of W(IV) ions. Red-ox processes involving Mo(III) and Mo(IV) ions were studied by cyclic voltammetry and potentiometry combined with in situ electronic absorption spectroscopy measurements. Anodic oxidation of Mo(III) chloro-ions on a glassy carbon electrode results in formation of Mo(IV) species. Mo(III)-Mo(IV) oxidation-reduction is reversible. Molybdenum(IV) chloro-species, MoCl6 2– are stable at 550-600 oC. At higher temperatures a disproportionation reaction occurs: 2 MoCl6 2– → MoCl6 3– + MoCl6 –. Molybdenum(V) ions decompose and molybdenum pentachloride sublimes from the melt: 2 MoCl6 – → MoCl5↑ + Cl–. Reactions of molybdenum and tungsten dioxides with hydrogen chloride in fused alkali chlorides were also investigated by in situ spectroscopy measurements. Depending on temperature and cationic composition of the melt the following reactions take place in the case of molybdenum: MoO2 + 4 HCl + 2 Cl– → MoCl6 2– + H2O MoO2 + 2 HCl → MoOCl2↑ + H2O Decreasing temperature or increasing mean alkali cation radius favors MoCl6 2–formation. Reaction of MoO2with HCl is a convenient method of preparing Mo(IV) containing chloride melts. Molybdenum and tungsten dioxides can be prepared by hydrogen reduction of the respective trioxides and the reduction processes were also studied in the course of the present work. The authors are grateful to Dr. A.V. Chukin for the help with XRD measurements.

A Spectroscopic and Electrochemical Study of Molybdenum(IV) and Tungsten(IV) Species in Alkali Chloride Melts

Speciation and electrochemical properties of molybdenum(IV) and tungsten(IV) species were investigated in NaCl–CsCl, NaCl–KCl–CsCl and LiCl–KCl–CsCl eutectic based melts between 500–900 oC. Metallic tungsten dissolves anodically, yielding W(IV) ions that are prone to oxidation upon prolonged contact with silica. Electrode potentials of tungsten in fused chlorides were measured. Electronic absorption spectra of the melts containing the products of anodic dissolution of tungsten were recorded. Mo(IV) ions can be formed by reacting molybdenum dioxide with hydrogen chloride or by anodic oxidation of Mo(III) ions. Electronic absorption spectra of Mo(IV) species were recorded and Mo(III)/Mo(IV) red-ox potentials were estimated.

Surface Structure and Photocatalytic Properties of Bi2WO6 Nanoplatelets Modified by Molybdena Islands from Chemical Vapor Deposition

We report on a novel route of preparing molybdena-modified bismuth tungstates and their successful application in the photocatalytic oxygen evolution reaction and the oxidation of glycerol. Hierarchically assembled monocrystalline Bi2WO6 nanoplatelets with a specific surface area of 10 m2/g were obtained applying a hydrothermal synthesis method using Na2WO4 and Bi(NO3)3 as precursors, followed by a solvent-free chemical vapor deposition method using Mo(CO)6, resulting in highly dispersed molybdena species. Extensive characterization using X-ray photoelectron spectroscopy, low-energy ion scattering, and Raman spectroscopy showed that microcrystalline MoO3 islands were formed on the bismuth tungstate surface that grew in height and lateral dimension with increasing loading. Correspondingly, the molybdena-modified materials were found to have favorable photocatalytic and photoelectrochemical properties in the oxygen evolution reaction and the selective oxidation of glycerol.

MoOx-VOx based catalysts for the oxidative desulfurization of refractory compounds: Influence of MoOx-VOx interaction on the catalytic performance

The oxidative desulfurization (ODS) process has emerged as a new technology to achieve ultra-low sulfur levels in diesel fuels. This work presents the performance of MoOx-VOx based catalysts in the ODS process and an evaluation of the interaction between MoOx and VOx in these bimetallic catalysts, using Al2O3 as catalytic support, and hydrogen peroxide and tertbutil-hidroperoxide as oxidant agents. The catalysts were characterized by scanning electron microscopy (SEM-EDX), nitrogen physisorption, X-ray diffraction (XRD) and temperature programed reduction (TPR). The catalytic activity of MoOx-VOx/Al2O3 was higher than the monometallic catalysts: MoOx/Al2O3 and VOx/Al2O3. The characterization results suggested that in MoOx-VOx catalysts the molybdenum species interact strongly with the support and that the vanadium species were distributed mainly as isolated-vanadium species, due to the interaction between VOx and MoOx.