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In this work, Co-promoted MoS2 catalysts supported on Al-modified mesoporous silica (HMS and SBA-16) have been prepared by the decomposition of ammonium tetrathiomolybdate and cobalt nitrate precursors in a H2S/H2 gas mixture. The effects of the support morphology and Al incorporation method (one-pot synthesis vs. support's grafting) on the catalyst activity were investigated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) conducted in a high-pressure batch reactor at 350 °C and total H2 pressure of 3.3 MPa. The physical and chemical characterization of the oxide precursors and spent catalysts was studied by a variety of several techniques (N2 adsorption–desorption, XRD, SEM, EDS, 27Al MAS NMR, Raman, TG/DTA and DRS UV–vis). The MoS2 phase of all catalysts exhibits similar size (about 2.8 nm) and stacking layers (4). Activity tests showed that CoAT/HMS-Al was most active and selective toward direct desulfurization (DDS) reaction pathway among the catalysts studied. Its catalytic response was similar to that of CoMo/γ-Al2O3 catalyst activated by reductive sulfiding. A linear correlation was found between DBT conversion at a reaction time of 5 h and the specific surface area and mean pore diameter of the catalysts. The best DBT HDS activity showed CoAT/HMS-Al catalyst having the best textural properties among the catalysts studied. Modification of SBA-16 with Al3+ ions by the one-step synthesis method rendered the catalyst more active in the HDS reaction than its modification by grafting. [ABSTRACT FROM AUTHOR]

In this work, novel trimetallic catalysts based on transition metal sulphides (Ru, Mo and Ni) supported on SBA-15 were synthesized. Citric acid (CA) was used as chelating agent in order to enhance the dispersion of the active phase and minimize the metal-support interaction. Sulfided catalysts were evaluated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 320 °C and 54.5 atm of total H2 pressure. The effects of different Ru/(Ni + Mo) atomic ratios on the active phase were studied. The catalysts were characterized using Micro-Raman spectroscopy, DRIFTS, XRD, XPS, HR-TEM and SEM techniques. Results have shown that there was a better dispersion of the metallic phases, which improves the physicochemical properties of the catalysts, increasing the catalytic activity. The trimetallic RuxMoNi catalyst with the lowest atomic ratio, have shown superior catalytic activity compared to their higher atomic ratio counterparts. The interaction of the chelating agent improved the catalytic activity, which was superior to that observed for NiMo based catalysts, considered one of the most active hydrotreating catalysts. [ABSTRACT FROM AUTHOR]

This work studies the effect of the support modifications (SBA-15) with Ti by using a ternary system as an active phase (Ni, Mo, W). Calcined and sulfided catalysts were characterized by a variety of techniques such as XRD, S BET , TPR, TPD-NH 3 , DRS-UV–vis, micro-Raman spectroscopy and HRTEM. Sulfided catalysts were tested in the hydrodesulphurization (HDS) of dibenzothiophene (DBT) performed in a batch reactor at 320 °C and total hydrogen pressure of 800 psi. This reaction was selected for the catalyst screening because DBT is a typical sulfur-containing hydrocarbon present in high-boiling petroleum fractions and coal derived liquids and the absence of any diffusion limitation for DBT molecule to entry into the porous structure of the SBA-15 supported catalysts. We observed that the incorporation of Ti did not decrease the catalytic activity in the HDS of DBT reaction except for Si/Ti = 40 catalyst. UV–vis analyses show a higher amount of tetrahedral species for CAT/40TiS15 in counterpart with CAT/60TiS15 that showed a lower amount of those species however, the lower amount of Ti in the catalyst (CAT/60TiS15) showed the highest hydrogenation capability among the catalysts studied (HYD/DDS = 0.81 ) despite the main route in the HDS of DBT reaction was the direct desulfurization (DDS) pathway (selectivity). [ABSTRACT FROM AUTHOR]

This study shows that ternary Ni-Mo-W sulfide catalysts supported on hexagonal mesoporous silica modified with Ti (HMS-Ti) showed a high enhancement of dibenzothiophene (DBT) transformation via hydrogenation route with respect to their Ti-free counterpart. The reaction of hydrodesulphurization (HDS) of DBT was carried out at in a batch reactor at 320 °C and 5.5 MPa of total H 2 pressure. The catalysts were characterized by a variety of techniques (chemical analysis, N 2 adsorption-desorption isotherms, low- and wide-angles XRD, TPR, TPD-NH 3 , DRS UV–vis, TPO/TG and HRTEM). At reaction time of 5 h, all synthetized catalysts exhibited higher DBT conversion (84–100%) than both commercial NiMo/γ-Al 2 O 3 and NiW/γ-Al 2 O 3 catalysts (59 and 69%, respectively). For all catalysts, the DBT transformation occurs via direct desulfurization (DDS) and hydrogenation (HYD) pathways. The DDS was the main reaction route for Ti-free sample whereas for both Ti-containing samples the DBT transformation occurs mainly via HYD reaction route. At a reaction time of 5 h, the best catalyst (NiMoW/HMS-Ti1) exhibited 100% of DBT conversions and the highest yield of hydrogenation route products. From the activity results, it is concluded that only the structure of Ti species is relevant for the catalyst activity, but not the amount of Ti incorporated in the HMS framework. The superior activity of sulfide NiMoW/HMS-Ti1 is linked with the best properties of its oxide precursor: a lowest band energy gap and a large amount of Mo(W) 6+ ions having octahedral coordination. After sulfidation, the best catalyst exhibited the “onion-type” Mo(W)S 2 structures which offer the best conditions for the formation of “bright rim” Mo edge sites, which are known to be active sites for DBT transformation via HYD reaction route. [ABSTRACT FROM AUTHOR]

Two series of SBA-16-supported Co Mo W ternary sulfide catalysts with atomic ratio r = Mo/(Mo + W) ranging from 0.3 to 0.7 were prepared by the simultaneous impregnation of SBA-16 and phosphated-SBA-16 substrates with metal precursors. The samples were characterized by a variety of techniques (chemical analysis, N 2 physisorption, SEM, XRD, DRS UV–vis, TPR, TPD-NH 3 , Raman spectroscopy, HRTEM, XPS and coke burning) . The catalytic performance was evaluated in the hydrodesulphurization (HDS) of dibenzothiophene (DBT), carried out in a batch reactor at 350 °C and 3.1 MPa of total H 2 pressure. The maximum activity at the same atomic ratio r = 0.4 was observed for the catalysts supported on SBA-16 modified with phosphorous ( r = 0.4(P)). HRTEM evidenced that this was because different MoS 2 crystalline structures were formed: the P-free sample prepared with Mo/(Mo + W) atomic ratio of 0.6 ( r = 0.6) exhibited the MoS 2 -2H crystalline structure whereas the P-containing samples prepared with Mo/(Mo + W) atomic ratio of 0.4 ( r = 0.4(P)) exhibited the interplanar distance corresponding to (0 0 3) planes of MoS 2 -3R crystalline structure. Additionally, the best activity of the r = 0.4(P) sulfide catalyst was linked with the enhancement of the WS 2 species surface exposure accompanied with a larger sulfidation degree of W species (from XPS). [ABSTRACT FROM AUTHOR]

Unsupported CoMoW sulfide hydrodesulfurization (HDS) catalysts were prepared by in situ decomposition of sulfur-containing precursors. The precursors were synthesized by reaction of the ammonium and tetraalkylammonium thiomolybdotungstates (R 4 N) 4 MoWS 8 (where R = H, methyl, propyl) with an aqueous solution of CoCl 2 ·6H 2 O in order to give molar ratios of Co/[Co + (Mo + W)] = 0.3. Co-promoted precursors were then in situ decomposed during the HDS of dibenzothiophene (DBT)-producing CoMoW sulfide catalysts. Solids were analyzed after the in situ activation by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction and for textural properties by using the BET and BJH methods. Catalysts with relatively high surface area and type IV N 2 adsorption–desorption isotherms were obtained. The use of the Co-promoted ammonium thiomolybdotungstate as precursor was found to be beneficial in the catalytic activity. The positive role of carbon in monometallic HDS catalysts confirmed by Chianelli and Berhault was not evidenced here since the catalytic activity decreased with the introduction of an alkyl group in the precursor. [ABSTRACT FROM AUTHOR]

In this work, the catalytic activity of ternary Co–Mo–W/Al-SBA-16 systems was investigated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) performed in a batch reactor at 350 °C and total H 2 pressure of 33.8 bar. The synthesized materials were characterized by a variety of techniques (chemical analysis, N 2 adsorption–desorption isotherms, XRD, TPR, TPD-NH 3 , FTIR of adsorbed pyridine, DRS-UV–vis, HRTEM and XPS). By applying the direct synthesis method, high surface area substrates with Al 3+ incorporated into the silica framework. The activity results indicate that all CoMoW/Al-SBA-16 catalysts were active in the HDS of DBT, the largest activity was found in the catalyst with the highest Al-content. This behavior was explained in terms of its largest specific area and good dispersion of the metal sulfide phases having average size of 3.3 nm (from HRTEM). Moreover, FT-IR spectroscopic study of adsorbed pyridine indicated Al incorporation into a SBA-16 substrate produces both Brønsted and Lewis acidities, which are beneficial for the HDS of DBT. All catalysts showed a high selectivity towards biphenyl indicating that HDS of DBT reaction proceeds mainly via direct desulfurization (DDS) reaction pathway. [ABSTRACT FROM AUTHOR]

Highlights: [•] Naturally occurring zeolite supported NiMoW catalysts were tested in hydrodesulfurization of dibenzothiophene. [•] The best catalyst was synthesized from ammonium thiosalts of Mo and W. [•] The use of tetraalkylammonium thiometalates precursors decrease the HDS activity. [•] The density of active phases on the support surface influenced on the HDS activity [ABSTRACT FROM AUTHOR]

Abstract: P-containing SBA-16 mesoporous systems were used as supports of ternary Ni–Mo–W hydrodesulfurization (HDS) catalysts. The samples were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, TPR, TPD-NH3, DRS UV–vis and HRTEM). XRD profiles evidenced the formation of crystalline Mo1- x W x O3 and NiMoO4 phases on the surface of oxide catalyst precursors with high P-loadings (1.0 and 1.6wt.%). The UV–vis DRS measurements showed a substantial decrease of energy band gap after P-loading onto the SBA-16 substrate with respect to P-free sample. The sulfided catalysts were tested in separate HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) reactions performed in a batch reactor at 320°C and H2 pressure of 5.0MPa. For both HDS reactions, the initial catalyst activity displayed a volcano-type curve indicating that catalyst behavior depends strongly on the phosphorous loading being all catalysts more active in the HDS of DBT then in the HDS of 4,6-DMDBT. The NiMoW/SBA-16 catalyst loaded with optimized amount of phosphorous (1.0wt.%) showed superior initial activity than the P-free counterpart. This effect was attributed to the enhancement of active phases dispersion on the support surface, as revealed by HRTEM measurements. It was found that the formation of “onion-type” Mo(W)S2 phases on the catalyst surface was detrimental for the HDS activity. At reaction time of 5h, the most active NiMoW/SBA-16 catalyst loaded with 1.0wt.% of P showed similar activity in both HDS of DBT and 4,6-DMDBT reactions. It was found that HYD route of both reactions was promoted by the support modification with P and due to inhibition of coordinatively unsaturated sites (CUSs) by competitive adsorption of products (mainly H2S). [Copyright &y& Elsevier]

Abstract: This research compares the hydrodesulphurization (HDS) activity of supported Co(Ni)-Mo-W ternary catalysts with respect to the nature of the support (hexagonal mesoporous silica (HMS) versus SBA-16 material having cage-like mesoporous structure), the type of promoter (Co vs. Ni) and the nature of Al species formed after support modification with Al. Both Al-HMS and Al-SBA-16 mesoporous silica substrates were prepared by the one-pot sol–gel synthesis method via the neutral templating pathway using dodecylamine and Pluronic F127 as surfactants, respectively. The oxide precursors were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, DRS UV–vis spectroscopy and 27Al NMR), whereas sulphided catalysts were characterized by XPS and HRTEM, and tested in the HDS of DBT conducted in a high-pressure batch reactor at T =350°C and P =3.1MPa. The activity results revealed that NiMoW/Al-HMS catalyst was more active than all Co-promoted catalysts (including a commercial CoMo/Al2O3 catalyst). The HDS activity was found to be markedly influenced by the textural properties of support and the dispersion of the active phases on the catalyst surface. It has been hypothesised that the presence of extraframework AlNO3 phases on the surface of CoMoW/Al-SBA16 compromises its HDS activity because of the formation of a less active “onion-type” Mo(W)S2 structure. [Copyright &y& Elsevier]

Unsupported Ni/MoS2 and Ni/WS2 HDS catalysts were prepared by in situ activation of hexamethylenediammonium thiometallates promoted with Ni. The method involved an aqueous solution reaction of ammonium thiomolybdate (ATM) or ammonium thiotungstate (ATT) with Ni(NO3)2·6H2O and hexamethylenediamine. Ni-promoted precursors were then in situ activated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) producing Ni/MoS2 and Ni/WS2 catalysts. Solids were analyzed after the in situ activation by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and for textural properties by using the BET and BJH methods. Catalysts with relatively high surface area and type IV N2 adsorption–desorption isotherms were obtained. The use of the hexamethylenediammonium precursor led to a significant nickel promotion of MoS2 and WS2 catalysts. For Ni/MoS2, the use of this carbon-containing precursor was found to be more beneficial for the final HDS catalytic activity than using the classical ammonium tetrathiomolybdate (ATM) without carbon. For Ni/WS2, compared to tetraalkylammonium thiosalts, the lower amount of carbon in excess formed during the decomposition of the hexamethylenediammonium precursor coupled with a lower crystallization rate of WS2 favors a correct nickel accommodation on the WS2 edges. [ABSTRACT FROM AUTHOR]

Abstract: Phosphate-loaded mesoporous SBA-15 and SBA-16 materials were used as supports of novel ternary Co-Mo-W hydrodesulfurization catalysts. The effects of support morphology (SBA-15 against SBA-16) and its modification with variable amounts of phosphorus were studied. The sulfided catalysts were tested in a reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 350°C and 3.1MPa of total H2 pressure. The calcined, fresh sulfided and spent catalysts were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, TPR, TPD-NH3, DRS UV–vis, micro-Raman spectroscopy, XPS, HRTEM and TPO/TGA). Regardless of the support, it was found that the presence of phosphorous inhibited the HDS activity, and the catalytic response of both SBA-15- and SBA-16-based systems did not depend on the support morphology. In terms of the reaction rate constants (k), both CoMoW/SBA-15 and CoMoW/SBA-16 catalysts were more active than a CoMo/Al2O3 commercial catalyst containing a small amount of phosphorous in its formulation. In general, the spent CoMoW/(x)P-SBA-16 catalysts showed a lower coke formation than their SBA-15-based counterparts because the phosphate incorporation to the SBA-16 material led to decrease in coke formation in the final catalysts, as opposite to the behavior of SBA-15-based counterparts. [Copyright &y& Elsevier]

Abstract: Nanostructures of tungsten trioxide (WO3) have been successfully synthesized by using an aged route at low temperature (60 °C) followed by a hydrothermal method at 200 °C for 48 h under well controlled conditions. The material was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Specific Surface Area (SBET) were measured by using the BET method. The lengths of the WO3 nanostructures obtained are between 30 and 200 nm and their diameters are from 20 to 70 nm. The growth direction of the tungsten oxide nanostructures was determined along [010] axis with an inter-planar distance of 0.38 nm. [Copyright &y& Elsevier]

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). [ABSTRACT FROM AUTHOR]

Hexamethylenediammonium thiometallate (HeDaT) of molybdenum and tungsten were synthesized using the aqueous solution method. This method improved significantly the yield of the catalysts. The HeDaT precursors were in situ activated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) generating MoS2 and WS2 catalysts. To characterize the precursors Fourier Transform Infra Red (FTIR), Ultraviolet (UV–Vis) and Nuclear Magnetic Resonance (1H NMR) spectroscopy techniques were used to determine their chemical structures. In addition, thermal analysis (TGA-DTA) were performed to study the fragmentation and decomposition behavior of their molecular structures. Catalysts were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed the shapes of the particles and the characteristic fringes of the layered MoS2 and WS2 phases, respectively. Specific surface areas were determined by the BET method with values of 5 and 19 m2/g with type I and IV adsorption–desorption nitrogen isotherms for both catalysts. The X-ray diffraction study showed poorly crystalline catalysts with weak (002) intensity for the MoS2 and a better-defined (002) reflection for the WS2. [ABSTRACT FROM AUTHOR]

Abstract: Unsupported Ni-Mo-W sulphide hydrodesulphurization (HDS) catalysts were prepared by ex-situ decomposition of trimetallic Ni-Mo-W precursors varying the nickel concentration. Firstly, the trimetallic precursors were treated in a stainless steel vessel of 45mL volume at 523K for 2h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H2S/H2 (15vol.% H2S) from room temperature to 673K. A series of four catalysts was tested in HDS of dibenzothiophene (DBT). The catalysts were labeled as Ni0.5, Ni1 and Ni2 according with the molar ratio of Ni in the sample. In addition, a precursor with a molar ratio Ni-Mo-W of 2:1:2 was prepared varying the concentration of tungsten, named as W2. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and BET specific surface area measurements. The ex-situ activation method leads to catalysts with a distribution of specific surface areas from 8 to 34m2/g, showing type IV adsorption–desorption isotherms of nitrogen typical for mesoporous materials, and poorly crystalline structures with different morphology, and varying phase composition. The Ni:Mo:W atomic ratios for the trimetallic catalysts show variations and are slightly smaller than those expected. The sample labeled as Ni-Mo-W2 showed the highest catalytic activity in the HDS of DBT (k =12×10−7 mol/gs). [Copyright &y& Elsevier]

[Display omitted] Inorganic hexagonal mesoporous silica (HMS) and aluminum modified HMS materials (Al-HMS) were prepared and used as supports of transition metal sulfide hydrodesulfurization (HDS) catalysts based on nickel, molybdenum, and tungsten as active phase. The samples were characterized with XRD, HRTEM, TPD, N 2 physisorption and UV–Vis. The catalytic activity of the trimetallic catalysts was performed in the HDS of dibenzothiophene (DBT). When Al was incorporated into the inorganic support, important changes and effects were observed on the physicochemical properties. On the other hand, the incorporation of Al into the HMS led to a decrease in the reaction rate (k) and a trend toward a direct path of desulfurization was observed for all materials. [ABSTRACT FROM AUTHOR]

Abstract: 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, (R4N)4MoWS8 (where R=H, methyl, propyl) with an aqueous solution of Ni(Co)Cl2·6H2O 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 45mL volume at 523K for 2h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H2S/H2 (15vol.% H2S) from room temperature to 673K, dwell of 2h at 673K. 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 60.6m2/g), mesoporous structure with pore size ranging from 18 to 45Å and type IV adsorption–desorption isotherms of nitrogen, poorly crystalline structures with different morphology and high catalytic activities in the HDS of dibenzothiophene (DBT). [Copyright &y& Elsevier]

Abstract: 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(NO3)2·6H2O 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 H2S (15%) in hydrogen from room temperature to 673K at 4K/min, dwell of 4h at 673K. 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). [Copyright &y& Elsevier]

NiMoS/TiMg and NiWS/TiMg nanocatalysts were synthesized, characterized by various techniques and tested in the hydrodesulphurization (HDS) of dibenzothiophene (DBT). TiMg mixed oxides containing 5, 10 or 15 wt% of MgO were prepared by sol–gel and then used as catalyst supports. A constant atomic ratio of Ni/(Ni + M) = 0.5 was kept for all the catalysts (M = Mo or W). The catalysts were first prepared by sequential-wet impregnation. Then, after an ex-situ sulfidation process, they were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and physisorption of N2 following the BET method. The presence of MgO in the NiMoS/TiMg and NiWS/TiMg catalysts resulted in an enhancement in the HDS activity of DBT. In addition, their HDS activities were higher than those observed in the NiMoS/Ti and NiWS/Ti catalysts. Furthermore, higher HDS activity was found for the NiMoS/TiMg compared with their NiWS/TiMg catalysts counterpart. [ABSTRACT FROM AUTHOR]

Ternary sulfided NiMoW/Ti-HMS solids with varying Si/Ti ratio (e.g. , 20, 40, 60) and with Ti incorporated via a post-synthesis method were evaluated in the hydrodesulfurization of dibenzothiophene. Ti-incorporation improved the catalytic activity of the samples up to 2.4 times compared to the sample without titanium and to a reference industrial catalyst. The performance was mainly associated with differences observed in the stacking and length and the dispersion of the active phase, this effect being stronger for the NiMoW/HMS-Ti 20 sample. The latter displayed the highest catalytic activity and sulfur removal via hydrogenation. Unlabelled Image • Catalytic activity depends on the coordinatively unsaturated Mo4+ and W4+ sites. • HDS optimum efficiency is reached for the NiMoW/HMS-Ti 20 catalyst. • A preference for the DDS route was observed for all catalysts. • Reaction pathway was related to the promotional effect of Ni species [ABSTRACT FROM AUTHOR]

Trimetallic CoNiMo hydrodesulfurization (HDS) catalysts were herein synthesized on Al 2 O 3 support through an incipient wetness co-impregnation procedure using ammonium heptamolybdate and cobalt (and nickel) acetate as precursors. CoNiMo catalysts were obtained by adding in a small proportion of nickel with a molar amount representing between 1 and 10% of the total Co atomic loading. This addition of low amounts of nickel allows keeping the (Co + Ni)/(Co + Ni + Mo) molar ratio close to the optimum value of 0.3. The as-formed catalysts were labeled as CoNixMo/Al 2 O 3 with x the relative stoichiometry of Ni compared to Co. Catalysts were then characterized by N 2 adsorption-desorption isotherms, X-ray diffraction, ICP-OES spectroscopy, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT). Results show a significant impact of adding small amounts of nickel to alumina-supported Co-promoted MoS 2 on the final HDS activity. While up to CoNi 0.03 Mo/Al 2 O 3 , the resulting HDS activity is hardly influenced by the addition of nickel, a strong beneficial effect is observed for CoNi0.05Mo/Al 2 O 3 with activity reaching a value of 7.2 × 10−7 mol.g cat −1.s−1. Increasing further, the amount of nickel abruptly decreased the DBT HDS activity. Interpretation of these results is then provided considering the additional role of nickel for improving the intrinsic activity of the HDS sites. Image 1 • The influence of incorporating low amounts of nickel into cobalt-promoted MoS 2 catalysts was herein evaluated. • HDS optimum efficiency is reached for the CoNi 0.05 Mo/Al 2 O 3 catalysts. • The CoNi 0.1 Mo/Al 2 O 3 catalyst with the richest Ni content shows the lowest HDS activity. • TOF values allowed us to analyze the incorporation of nickel into Co-promoted MoS 2 slabs. [ABSTRACT FROM AUTHOR]

Iron sulfide films were synthesized by the solid–gas reaction of diethyl disulfide on iron foils in the temperature range of 658–768 K using a microbalance, where the film growth kinetics followed Deal–Grove behavior. Analysis of the films by X-ray photoelectron and Raman spectroscopies as well as X-ray diffraction and scanning electron microscopy analysis revealed the formation of combined FeS/FeS2(troilite/pyrite) films with a sheet-like morphology at low temperatures and only FeS (troilite) films with granular morphology at higher temperatures. [ABSTRACT FROM PUBLISHER]

In the field of heterogeneous photocatalysis, catalyst concentration is one of the main parameters that restricts light availability, specifically in photocatalytic annular slurry reactors design. Therefore, data that describes the dependence of energy on both, distance and catalyst concentration is needed. This paper proposes the local relative light intensity (LRLI) as a quantity that represents the residual energy on radial distance. Experimental measurements of LRLI were made from 0 mm to 25 mm, using two commercial TiO2 powders in a wide range of concentration (200 to 1000 mg/L). Results show that residual energy was less than 80% at 6 mm from the source, for both catalysts in all concentrations. Furthermore, a forward-scattered behavior was detected, the LRLI profiles (LRLI vs radial distance) followed an exponential decay model. All profiles were correlated as a catalysts concentration function. Information obtained was used to develop a methodology to calculate the LRLI values at any radial distance for a settle catalyst concentration. The calculated values of LRLI approaches real data with a relative local accumulated error less than 10% for both catalysts. This methodology may be applied to calculate the energy available in any TiO2/UV-A annular slurry system. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous SBA-15 material was used as support of binary Co-Mo hydrodesulfurization (HDS) catalysts prepared using a novel approach based on the use of already sulfided precursors (ammonium tetrathiomolybdate and cobalt diethyldithiocarbamate). The effects of atmosphere and activation temperature were studied to optimize the preparation of highly active CoMo/SBA-15 hydrodesulfurization catalysts. Two sets of catalysts were synthesized using either a N2/H2 (10% H2) or a H2/H2S (15% H2S) atmosphere at three different temperatures of activation (723, 773 and 823K). The catalysts were tested in the HDS of dibenzothiophene (DBT) and the catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The use of already sulfided precursors leads to a homogeneous dispersion of the active phase inside the SBA-15 channels. Moreover, the N2/H2 activation procedure at 723K allows obtaining optimized HDS active catalysts. Finally, a confinement effect of MoS2 slabs inside the SBA-15 channels leads to a high selectivity along the direct desulfurization pathway. [Copyright &y& Elsevier]

This article is focused on the problem of the inhibition of the hydrodeoxygenation (HDO) reaction by competitive adsorption of the S-containing compounds on the active sites. The phosphorous effect during co-processing of pyrolysis bio-oils and S-content model compounds over sulfide NiMo/P/HMS-Al catalysts was investigated. A series of NiMo catalysts supported on mesoporous P (x) /HMS-Al materials were prepared and characterized by several techniques. Guaiacol (GUA) was considered as a pyrolysis bio-oils model compound, while the dibenzothiophene (DBT) was used as a model molecule of S-content. The activity test revealed that support modification with 1.1 wt% of P (NM-P1.1) decreased the inhibition of HDO reaction by co-adsorption of DBT on the active sites. With the most active NM-P1.1 catalyst, the formation of a less susceptible to coke formation product (phenol) was favored. The main superiority of sulfided NM-P1.1 catalyst comes from the support decoration with P 2 O 5 nanoparticles leading to its highest Brønsted acidity, the surface enrichment with metal sulfide species as well as with the diminishing of Al leaching from the framework of support during the HDO reaction. The activity tests demonstrated that support modification with phosphorous is an efficient method to solve the problem of the HDS inhibition by the HDO reaction. Unlabelled Image • The NiMoP/HMS-Al 1.1 wt% of P loaded exhibited the best HDO activity and stability during simultaneous HDO and HDS reactions • P loaded is effective method for diminishing the inhibition of HDO reaction by co-adsorption of S-containing compound • Surface P 2 O 5 nanoparticles decoration is effective for lowering Al leaching from the support framework during HDO reaction [ABSTRACT FROM AUTHOR]

This paper presents the catalytic activity of ruthenium phosphides supported on SBA-15 material as hydrodesulfurization (HDS) catalysts of gasoline model compounds. It was studied the influence of the P/Ru molar ratio of 0.5, 1, 2, 3, and 4.5 (samples were labeled as 0.5-P/Ru, 1-P/Ru, 2-P/Ru, 3-P/Ru and 4.5-P/Ru) in the hydrodesulfurization of 3-methyl-thiophene as a model molecule and evaluated under mild reaction conditions. The ruthenium phosphide phase was synthesized from a conventional phosphate reduction method using RuCl 3 and (NH 4) 2 HPO 4 as precursors. The catalysts were characterized by XRPD, N 2 adsorption–desorption isotherms, TEM, EDS, XPS, NH 3 -TPD, H 2 -TPD and CO chemisorption. All catalysts maintained the mesoporous structure characteristic of the SBA-15 support, although pore blockage occurred at high P loadings. TEM images and EDS mapping showed well dispersed active phosphide phases, mainly RuP and Ru 2 P, as evidenced by XRPD. 3-P/Ru catalyst became to be the most active in the HDS reaction, with a high isomerization ability, which was assigned to its medium acidity and higher amount of active species on the surface that activates H 2 species. • The ruthenium phosphide catalysts are effective for the HDS for selective sulfur removal of gasoline model compounds. • The phosphorus load leads the formation of Ru 2 P active phase, optimizing a P/Ru molar ratio of 3. • The ruthenium phosphide catalysts displayed medium acidity properties that led to a high isomerization ability. [ABSTRACT FROM AUTHOR]

• Ru-Mo/SBA-15 catalysts exhibit synergetic effect between Ru and Mo in the HDS of DBT reaction. • The introduction of optimized amount of Ru impurites into MoS 2 phase changes the electronic properties of this phase. • The Ru-induced metalization of Mo ions enhanced selectivity toward hydrogenation rute products. The effect of introducing Ru impurities into the MoS 2 crystalline structure of the sulfided Ru x Mo (1- x) S 2 /SBA-15 catalysts have been investigated using density functional theory (DFT) calculations and the catalyst characterization by different techniques (chemical analysis (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), N 2 physisorption, DRIFTS of adsorbed pyridine (DRIFTS-Py) and X-ray photoelectron spectroscopy (XPS)). The catalyst activity was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction carried out in a batch reactor, T = 320 °C and total H 2 pressure of 5.5 MPa. From electronic structure DFT calculations is was concluded that the 4d orbitals of both Mo and Ru played an important role in the catalyst optimization being the processes of transport and charge transference the most important ones. It was found that the enrichment with Ru, promotes a greater electronic participation (DOS at the Fermi level) of the different atoms in the Ru x Mo (1-x) S 2 phase leading to metallization of the Mo ions. The catalyst activity in HDS of DBT reaction demonstrated a similar behavior to that of theoretical density of states (DOS) calculated via DFT. All bimetallic systems presented the synergetic effect between Ru and Mo in the HDS of DBT reaction over Ru x Mo (1- x) S 2 /SBA-15 catalysts. The highest activity observed for Ru content of x = 0.4 was consistent with theoretical results predicting that the optimum DOS contributions should be around x = 0.44. The most active Ru 0.4 Mo 0.6 S 2 /SBA-15 exhibit the best hydrogenation properties linked with the Ru-induced metallization of Mo ions in the Ru 0.4 Mo 0.6 S 2 phase. This catalyst showed two-fold higher hydrogenation properties than CoMoS/γ-Al 2 O 3 reference catalyst. The linear dependencies of initial activity on Brønsted-to-Lewis acidities ratio (from DRIFT-Py) and total metal surface exposure (from XPS) were observed. [ABSTRACT FROM AUTHOR]

In this work mesoporous Al-SBA-15 was synthesized by the sol-gel method and used as a solid acid catalyst for the conversion of a model mixture of tricaprylin with 20 wt% of palmitic acid at T = 175–215 °C. The incorporation of aluminum to the SBA-15 through the sol-gel method, gives rise to mesoporous materials with the typical hexagonal arrangement of SBA-15 (XRD). In addition, these materials possess Lewis and Brönsted acid sites (pyridine adsorption), large surface area and wide pore diameter (N 2 physisorption) being capable of catalyzing simultaneously transesterification of triglycerides (tricaprylin) and esterification of palmitic acid (up to 20 wt%) resulting in FAME yields of 40–87%. A detailed analysis of the reaction products indicates that the conversion of triglyceride to diglyceride is the limiting step during the acid transesterification over Al-SBA-15 catalysts, which results from the difficulty to protonate triglycerides followed by methanol addition. A simplified lumped first order reaction model reproduces well the experimental data for the acid transesterification of tricaprylin in the presence of a high content of free fatty acids (palmitic acid). The calculated activation energy was 64.7 kJ mol −1 which is in the range of 45–120 kJ mol −1 previously reported for acid catalysts. [ABSTRACT FROM AUTHOR]

This study reports the effect on catalytic activity resulting from Ni incorporation in Pt nanoparticles supported on carbon nanotubes (CNTs) for electrochemical methanol oxidation at low temperature in acidic conditions. Chemical composition, morphology and structure of the Pt 1–X Ni X /CNTs (X = 0, 0.1, 0.2, 0.3, 0.4, 0.5) catalysts were studied by EDS, SEM, XRD, TEM and TGA. The catalytic activity of the prepared materials in methanol electro-oxidation reaction was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). The results of catalytic activity of the nanostructured materials showed a volcano-type relationship between the Ni relative concentration current density. The enhancement of catalytic activity was attributed to changes in surface electronic structure of Pt nanoparticles that impacted in an increment of active sites for methanol dehydrogenation and oxidation processes. On the other hand, high concentration of Ni (concentration ≥ 30 at.%) in Pt nanoparticles caused a substantial decrease of the catalytic activity due to a depletion of active sites for the methanol dehydrogenation process. The highest catalytic activity was observed when the Ni relative concentration reaches 30 at.%. [ABSTRACT FROM AUTHOR]

A group of hydrodesulfurization (HDS) catalysts, based on transition metal sulfides (Co-Mo-W) and supported on mechanically-mixed mesoporous silicas (SBA-15 and SBA-16), have been synthesized and characterized by physicochemical methods (DRS-UV–vis, Micro Raman spectroscopy, XRD, SEM, HRTEM, EDS and catalytic activity). It has been demonstrated that the use of a mixture of silicas with two different porous structures has an advantage with respect to the use of the SBA-15 and SBA-16 separately for the preparation of supported catalysts for hydrodesulfurization reactions of refractory sulfur compounds, such as dibenzothiophene. This is because the presence of different porous structures has a positive effect over the diffusion processes of the precursors of the active phases on the support, and the whole result is a higher catalytic activity for the HDS reactions of dibenzothiophene, even more than that of the commercial catalyst used as a comparative model; this activity is also related with the stage of the synthesis process in which the mixture is done. [ABSTRACT FROM AUTHOR]

Abstract This work presents the results obtained from the dosimetric properties of the new radiation detectors of KMgF 3 :Tb + PTFE. The thermoluminescent material was obtained by microwave technique. The polycrystalline powder obtained was mixed with polytetrafluoroethylene resin powder in the ratio 2:3 to make dosimeters in pellet form. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy 60Co gamma radiation, the repeatability test in the measurements, during ten cycles of heat treatment, irradiation and readouts, showed ± 3.7% DS, the stability test of thermoluminescent signal, during two months showed that the fading is practically null. For the results obtained, this new detector could be very useful for radiation dosimetry, in clinical applications. Highlights • The synthesis of KMgF 3 :Tb assisted via microwave was performed. • The dosimetric properties of KMgF 3 :Tb + PTFE phosphor was studied. • The material has very good reproducibility. • The TL signal is very stable. • This TL material is suitable for dosimetry. [ABSTRACT FROM AUTHOR]

Herein reported are the synthesis and the photocatalytic activity of MWCNT/TiO 2 heterojunction photocatalysts obtained by microwave-assisted method using titanium butoxide as precursor. The obtained materials were characterized by XRD, Raman, SEM, TEM, UV–vis, FTIR, surface area (BET) and photoluminescence. The characterization results showed that the addition of MWCNT did not provide structural changes on TiO 2 . The photocatalytic activities of the synthesized materials were investigated using acid blue 9 dye as a model molecule. The results indicate an enhancement on photocatalytic activity by the addition of low amount of MWCNT (1 and 3 wt%). The improvement is attained to the synergic effect between TiO 2 and MWCNT which reduces the electron–hole pair recombination according with the photoluminescence study. In this way, a proposed schema for the enhanced photoactivity of the MWCNT/TiO 2 heterojunction photocatalyst is discussed. [ABSTRACT FROM AUTHOR]

Abstract: This contribution describes the effect of SBA-15(16) support modification with variable quantity of P2O5 (0.5 and 1.0wt%) on the catalytic response of supported ternary CoMoW catalysts tested in the gas-phase hydrogenolysis of anisole, as a model compound for pyrolysis oil. The catalysts were characterized by a variety of techniques (S BET, XRD, TPD-NH3, XPS, HRTEM and coke combustion followed by TG/DTG). Under steady-state conditions, the sulfided CoMoW/SBA-16 catalyst modified with a small amount of phosphate (0.5wt%) recorded the highest activity and stability in anisole transformation at 310°C and 3MPa of hydrogen pressure. All catalysts exhibited similar selectivities at the same anisole conversion (38%), indicating that catalyst morphology did not influence the catalytic behavior. Regardless of the carrier, deoxygenation was not significant, with demethylation (phenol) and isomerization (o-cresol, o-xylenol) being the main reaction routes. The highest activity recorded by the phosphate-containing CoMoW/SBA-16 catalyst is associated with its highest total acidity, the largest population of Mo(W)S2 phases located mainly within the inner support porous structure, the greatest sulfidation degree of W species and major stability during time-on-stream operation with respect to other catalysts. [Copyright &y& Elsevier]

Abstract: Different amounts of C and C–Cu mixtures were employed to produce Al–C and Al–C–Cu powder composites by mechanical milling. In order to determine the Cu effect, hardness tests were carried out in the as-milled samples and at different sintering temperatures. Also, X-ray analyses using Rietveld program, transmission electron microscopy and calorimetry were used for the microstructural characterization. In agreement with the results, the Cu powder acts as carrier in the incorporation of graphite into the Al matrix. Also, due to the presence of graphite particles together with Al4C3 precipitation, hardness values remain stable even at elevated temperatures for these Al-based composites. [Copyright &y& Elsevier]

Unsupported trimetallic NiMoW sulfide catalysts with high hydro-desulphurization activities are prepared from Ni-containing ammonium thiomolybdo tungstates by in situ and ex situ activation. These precursors are prepared by adding an aqueous NiCl2 solution to an aqueous (NH4)4MoWS8 solution in either a 1:1 or 0.5:1 Ni/Mo(W) molar ratio. The resulting precursors Ni0.5/(NH4)4MoWS8 and Ni/(NH4)4MoWS8 yield Ni0.5MoW-in situ, NiMoW-in situ, Ni0.5MoW-ex situ and NiMoW-ex situ sulphide catalysts, respectively. The activation method affects both physical and chemical properties, such as macro and microstructure, crystalline structure, specific surface area, N2 adsorption–desorption isotherms. The in situ/ex situ activation of these ammonium thiotrimetallate precursors leads to a mesoporous structure with a pore size ranging from 20 to 60 Å and type IV N2 adsorption–desorption isotherms. X-ray diffraction patterns of unsupported NiMoW sulfide catalysts correspond to those of a microcrystalline material, with outstanding reflections attributed to MoS2, WS2, NiS, and Ni9S8 phases. [ABSTRACT FROM AUTHOR]

A series of trimetallic Ni–Mo–W catalysts supported on cubic mesoporous silica (SBA-16) modified with Ti were prepared with the aim to study the effect of Ti incorporation method (sol-gel against pore volume post-synthesis impregnation) on the physical and chemical properties of the synthetized materials. The catalytic behavior of the sulfided catalysts was evaluated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT). The catalyst characterization by variety of techniques demonstrated that one-pot synthesis led to Ti ions incorporation into SBA-16 structure and an increase of acidity whereas the post-synthesis method led to formation of octahedral Ti species decorating support's surface. The catalytic behavior was closely linked with the characteristics of their oxide precursors. The catalysts prepared by sol-gel method demonstrated to be more effective toward S-removal from DBT than the catalyst modified by post-synthesis method. The initial HDS activity of the best NiMoW/S16–Ti catalyst doubled that of NiMoW/SBA-16 and a commercial NiMo/γ-Al 2 O 3 which was linked with its better textural properties, acidity and adequate active phases dispersion. The main effect of the support modification with Ti was the enhancement of selectivity toward HYD route products. The best hydrogenation selectivity was archived by Ti incorporation via post-synthesis method which was linked to the formation of curved Mo(W)S 2 layers having a large amount of "brim" HYD sites. Image 1 • HDS activity of NiMoW catalysts was enhanced by Ti incorporation into SBA-16 framework. • The post-synthesis support's decoration with TiO 2 enhanced HYD selectivity. • The bent Mo(W)S 2 layers are formed around of TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Nickel addition in the unsupported Ga-containing WS 2 catalysts of varying Ga-content on their catalytic performance for the hydrodesulfurization of dibenzothiophene was studied. Nickel addition caused a drastic enhancement of the catalytic activity of the samples. The catalyst with 1.5 wt% Ni addition showed the highest activity. Besides, all Ga-loaded catalysts enhanced the hydrogenation pathway of dibenzothiophene transformation, starting with the hydrocracking reactions of the aromatic rings prior to their hydrogenation. FTIR studies of NO adsorption showed that Ga-addition increased both the dispersion of Ni and W species and the interaction of Ni species with W. Unlabelled Image • Ga addition has a strong effect on the morphology of NiWS 2 phase. • Ga incorporation enhanced the total acidity of the catalysts. • Ga incorporation enhanced the catalytic performance of the catalysts in the HDS of DBT. [ABSTRACT FROM AUTHOR]