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Objetivo: En este estudio se evaluó el efecto de la modificación con óxido de zinc del soporte convencional en catalizadores de hidrodesulfuración (HDS) a base polioxometalato Anderson-Evans de NiMo5W. Metodología: Los catalizadores fueron sintetizados por el método de co-precipitación del polioxometalato Anderson-Evans de NiMo5W sobre Al2O3. Los catalizadores se caracterizaron por FRX, MEB/EDS, CHONS, propiedades texturales, FT-IR, Raman y titulación potenciométrica con n-butilamina. Resultados: La MEB reveló tamaños de agregados de partículas para NiMo5W/γ-Al2O3 entre 0,7 μm y 4,1 μm, y para NiMo5W/γ-Al2O3-ZnO entre 0,5 μm y 3,5 μm. Las isotermas fueron de tipo IV característica de materiales mesoporosos, sus áreas específicas fueron γ-Al2O3 (207 m2/g), γ-Al2O3-ZnO (185 m2/g), NiMo5W/γ-Al2O3 (97 m2/g) y NiMo5W/γ-Al2O3-ZnO (121 m2/g). FTIR demostró que la inclusión de ZnO en el soporte promueve una mejor adsorción del polioxometalato en la superficie. Raman de los catalizadores solo mostró modos característicos del MoS2 A1g: (378 cm-1) y (404 cm-1). La titulación potenciométrica con n-butilamina indicó mayor densidad de sitios ácidos para NiMo5W/γ-Al2O3 (20,6 μmol/m2) frente a NiMo5W/γ-Al2O3-ZnO (15,2 μmol/m2). El catalizador NiMo5W/γ-Al2O3-ZnO (95%/67%) presentó mayor conversión de indol e HDN que NiMo5W/γ-Al2O3 (85%/55%). Conclusiones: La reacción de hidrodesnitrogenación de Indol siguió el mecanismo de reacción reportado en la literatura. La reacción de hidrodesnitrogenación de Indol siguió el mecanismo de reacción reportado en la literatura. De ahí que, el catalizador NiMo5W/γ-Al2O3-ZnO (95%/67%) presentó mayor conversión de indol e HDN que NiMo5W/γ-Al2O3 (85%/55%).

Currently, polypropylene (PP) is highlighted using sorbitol-based clarifying agents since these agents are high quality, low cost, and work as a barrier against moisture, which makes PP ideal for packaging food, beverages, and medical products, among others. The use of analytical methods capable of recovering these additives in wastewater streams and then reusing them in the PP clarification stage represents an innovative methodology that makes a substantial contribution to the circular economy of the PP production industry. In this study, a method of extraction and recovery of the Millad NX 8000 was developed. The additive was recovered using GC-MS and extracted with an activated carbon column plus glass fiber, using an injection molded sample, obtaining a recovery rate greater than 96%. TGA, DSC, and FTIR were used to evaluate the recovered additive’s glass transitions and purity. The thermal degradation of the recovered additive was found to be between 340 and 420 °C, with a melting temperature of 246 °C, adopting the same behavior as the pure additive. In FTIR, the characteristic absorption peak of Millad NX 8000 was observed at 1073 cm−1, which indicates the purity of the extracted compound. Therefore, this work develops a new additive recovery methodology with high purity to regulate the crystallization behavior and of PP.

Ti modified MCM-41-supported NiMo and CoMo catalysts and their respective Ti free reference catalysts were prepared, characterized, and tested for the hydrodesulfurization reactions. The samples were synthesized by well-known procedures, such as liquid crystal templating and successive impregnation method for the supports and catalysts, respectively. Ti precursor was directly incorporated into the micellar solution before adding the silica precursor at different molar Si/Ti ratios (x = 75 and 50). Fourier transform infrared spectroscopy, solid-state 29Si-nuclear magnetic resonance, small- and wide-angle X-ray diffraction, and nitrogen physisorption were used as characterization techniques. Four sulfided catalysts were also characterized by high-resolution transmission electron microscopy. The catalysts showed important increases in the reaction rates during both thiophene and dibenzothiophene hydrodesulfurization when the support was structurally modified with Ti-atoms. The samples supported on Ti-MCM-41(75) presented a higher activity than those supported on Ti-MCM-41(50), and they were superior to their respective Si-MCM-41-supported NiMoS and CoMoS catalysts, even NiMoTiM75 and CoMoTiM75 catalysts presented better performance compared to the conventional NiMo/Al2O3 and CoMo/Al2O3 catalysts in the DBT hydrodesulfurization. Ti incorporation also enhanced the selectivities to the hydrogenated products, which could be beneficial to destabilize refractory S-containing molecules.

In this research, the presence of microplastics was detected through a differential scanning calorimetry (DSC) analysis of three wastewater treatment plants. One of these plants applied only a preliminary treatment stage while the others applied up to a secondary treatment stage to evaluate their effectiveness. The results showed the presence of polyethylene (PE), polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET), which were classified as fragments, fibers or granules. During the evaluation of the plants, it was determined that the preliminary treatment did not remove more than 58% of the microplastics, while the plants applying up to a secondary treatment with activated sludge achieved microplastic removal effectiveness between 90% and 96.9%.

The effect of Ga as support modifier and V as second promoter on the NiMoV/Al2O3-Ga2O3 catalyst varying the synthesis method (SG: sol–gel synthesis vs I: impregnation synthesis) was studied. The catalysts were characterized by elemental analysis, textural properties, XRD, XPS, 27Al NMR, Raman, EDX elemental mapping and HRTEM. The chemical analyses by XRF showed coincidence between experimental and theoretical values according to stoichiometric values proposed to Mo/Ni = 6 and (V + Ni)/(V + Ni + Mo) = 0.35. The sol–gel synthesis method increased the surface area by incorporation of Ga3+ ions into the Al2O3 forming Ga–O–Al bonding; whereas the impregnation synthesis leads to decrease by blocking of alumina pores, as follows NiMoV/Al2O3-Ga2O3(I)

The effect of the sulfur and metal-type content of MoP-S/

Cobalt molybdenum carbide supported on activated carbon was synthesized and the effect of sulfiding on the catalytic activity of the glycerol trioleate deoxygenation process (DOX) was evaluated. Prior to the glycerol trioleate deoxygenation reactions, the catalyst was reduced and sulfided with CS2/H2. The CoMo/CA carbide was characterized by specific area (B.E.T), X-ray diffraction (XRD), elemental analysis (CHON-S), potentiometric titration with n-butylamine and X-ray photoelectron spectroscopy (XPS). The specific area of the CoMo/CA carbide and the support were 246 m2/g and 881 m2/g, respectively. XRD analysis proved the presence of Co6Mo6C2 and metallic cobalt. XPS showed the presence on the surface of signals assignable to Moδ+, Mo4+, Mo6+, Co2+, S2– and SO42–. Sulfided CoMo/CA carbide showed higher activad to glycerol trioleate esoxygenation than unsulfided CoMo/CA carbide. The highest yield was obtained at 310 °C, 900 psi H2 and 2 h of reaction (100% conversion) and a higher selectivity towards heptadecane (55%) and octadecane (45%) favoring decarboxylation (HDCX) and decarbonylation (HDCn) than hydrodeoxygenation (HDO).

The effect of Ga and V as support-modifier and promoter of NiMoV/Al2O3-Ga2O3 catalyst on hydrogenation (HYD) and hydrodesulfurization (HDS) activities was studied. The catalysts were characterized by elemental analysis, textural properties, XRD, XPS, EDS elemental mapping and High-resolution transmission electron microscopy (HRTEM). The chemical analyses by X-ray Fluorescence (XRF) and CHNS-O elemental analysis showed results for all compounds in agreement, within experimental accuracy, according to stoichiometric values proposed to Mo/Ni = 6 and (V+Ni)/(V+Ni+Mo) = 0.35. The sol-gel synthesis method increased the surface area by incorporation of Ga3+ ions into the Al2O3 forming Ga-O-Al bonding, whereas the impregnation synthesis method leads to decrease by blocking of alumina pores, as follows NiMoV/Al-Ga(1%-I) &lt, NiMoV/Al-Ga(1%-SG) &lt, NiMo/Al2O3 &lt, Al2O3-Ga2O3(1%-I) &lt, Al2O3-Ga2O3(1%-SG) &lt, Al2O3, propitiating Dp-BJH between 6.18 and 7.89 nm. XRD confirmed a bulk structure typical of (NH4)4[NiMo6O24H6]&bull, 5H2O and XPS the presence at the surface of Mo4+, Mo6+, NixSy, Ni2+, Ga3+ and V5+ species, respectively. The EDS elemental mapping confirmed that Ni, Mo, Al, Ga, V and S are well-distributed on Al2O3-Ga2O3(1%-SG) support. The HRTEM analysis shows that the length and stacking distribution of MoS2 crystallites varied from 5.07 to 5.94 nm and 2.74 to 3.58 with synthesis method (SG to I). The results of the characterization sulfided catalysts showed that the synthesis method via impregnation induced largest presence of gallium on the surface influencing the dispersion V5+ species, this effect improves the dispersion of the MoS2 phase and increasing the number of active sites, which correlates well with the dibenzothiophene HDS and naphthalene HYD activities. The dibenzothiophene HDS activities with overall pseudo-first-order rate constants&rsquo, values (kHDS) from 1.65 to 7.07 L/(h&middot, mol&middot, m2) follow the order: NiMoV-S/Al-Ga(1%-I) &lt, NiMo-S/Al2O3 &lt, NiMoV-S/Al-Ga(1%-SG), whereas the rate constants&rsquo, values (k) of naphthalene HYD from 0.022 to 2.23 L/(h&middot, m2) as follow: NiMoV-S/Al-Ga(1%-SG) &lt, NiMoV-S/Al-Ga(1%-I). We consider that Ga and V act as structural promoters in the NiMo catalysts supported on Al2O3 that allows the largest generation of BRIM sites for HYD and CUS sites for DDS.

The reaction of the H2salophen ligand, 2,2′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis (methanylylidene))diphenol, with one molar equivalent of Si(NCS)4, MeSi(NCS)3 (13), or HMeSi(NCS)2 afforded neutral hexacoordinate silicon complexes, which have an-NCS bi-functionality (complex 1) and mono-functionality (complex 14). The reaction of Si(NCS)4 with the H2salophen-type ligand1,1′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene)) bis(naphthalen-2-ol) (H2Noph), afforded the hexacoordinate silicon complex 15, which has an-NCS bi-functionality. Single-crystal X-ray structural and elemental analyses were used to characterize and confirm the structure of the starting material 13 and complexes 1, 14, and 15. The complexes were characterized in solution by 1H, 13C, and silicon-29 nuclear magnetic resonance (29Si NMR) and in the solid state by 29Si cross-polarization/magic angle spinning (CP/MAS) NMR. Because of the poor solubility of complex 1, it was only possible to characterize it in the solid state by 13C and 29Si CP/MAS NMR and in solution by 1H NMR.

The effect of Nb as a support modifier on the NiMo6/Al2O3–Nb2O5(x) (x = 0, 1, 4, and 8 wt% Nb) catalysts was studied. The supports were prepared by one-pot coprecipitation from soluble precursors. The XRF analysis of the catalysts showed that the contents of Mo and Ni increased slightly with the presence of Nb. Micropore area and pore volume augmented importantly with Nb content, resulting in pore diameters between 5.3 and 9.3 nm. XPS analysis showed that the presence of Nb decreases the active metal–support interaction, improving the Mo and Ni sulfidation degree. The Raman spectra of sulfided catalysts suggested an increase in the number of layers of MoS2 in the presence of Nb. Generally, the thiophene HDS activity at normal pressure of sulfided NiMo6/Al2O3–Nb2O5(8) was greater than that of the sulfided catalysts with x = 0, 1, and 4 wt% Nb, which can be attributed to the Nb promotion that would have an effect on the type of active site (Bronsted or Lewis acidic sites), since the number of sites by CO chemisorption for sulfided NiMo6/Al2O3–Nb2O5(x) did not show correlation with the catalytic activity. The high-pressure HDS activity of dibenzothiophene was also greater in the presence of Nb, and the hydrogenation route was preferred for the Nb-promoted solid, while the unpromoted one showed a larger yield of direct desulfurization products.

The γ-Al 2 O 3 -supported Anderson-type complexes (NH 4 ) 4 [NiMo 6 − x W x O 24 H 6 ]·5H 2 O (x = 0, 3 or 6) were carburized with CH 4 /H 2 (1:4) mixture (denoted by NiMo 6 − x W x -C/Al). These solid compounds have been tested in a continuous flow, fixed bed reactor for thiophene hydrodesulfurization and polychlorinated biphenyls hydrodechlorination, and in (semi-) batch reactor for dibenzothiophene selective oxidation. The specific surface area and pore volume of NiMo 6 -C/Al were greater than those of NiW 6 -C/Al and NiMo 3 W 3 -C/Al. XRD results evidenced a bulk structure typical of Mo 2 C, W 2 C, WC and NiC. FT-IR verified the absence of bands corresponding to metal oxides. Generally, the catalytic activity toward a given reaction product of NiMo 6 -C/Al was greater than those of NiW 6 -C/Al and NiMo 3 W 3 -C/Al due either to its better textural properties or to a more complete transformation of the metal phases into active ones.

Alumina supported (NH4)4[NiMo6-xWxO24H6]•5H2O Anderson type heteropolyoxometalates were synthesized by coprecipitation. These solids were used as precursors in the thiophene hydrodesulfurization catalytic at 400 °C. The catalytic precursors were characterized by textural properties (BET specific surface area and, total pore volume and pore diameter distribution), X-ray diffraction (XRD), IR spectroscopy (FTIR) and S analysis (CHON-S). The specific surface area was between 109 and 35 m2/g with total pore volume and pore diameter distribution of 0,11-0,34 cm3/g and 8,9-9,6 nm, respectively. XRD showed the presence of NiWO4, (NH4)4[NiMo6O24H6]•5H2O and WO3. FTIR analysis can be assigned to the characteristic vibrations of Anderson-type structure, due to stretching and bending of the functional groups present. The NiMo6-O/Al precursor was the most active in the HDS, it had a conversion of 72,75% and was even more active than the AERO commercial catalyst. The results of HDS revealed that the catalytic activity increases as follows: NiMo6-O/Al > AERO > NiMo3W3-O/Al > NiW6–O/Al. The catalytic selectivity of precursors and commercial catalyst (AERO) was directed towards the cis-butene. Se sintetizaron heteropolioxometalatos tipo Anderson (NH4)4[NiMo6-xWxO24H6]•5H2O soportados sobre γ-Al3O2, utilizando el método de coprecipitación. Estos solidos fueron utilizados como precursores en la reacción de hidrodesulfuración (HDS) de tiofeno a 400°C. Los precursores catalíticos se caracterizaron por propiedades texturales (área específica (B.E.T) y, distribución del diámetro y volumen de poros), difracción de rayos X (DRX), espectroscopía infrarroja (FT-IR) y análisis elemental (CHON-S). Las áreas específicas estuvieron dentro del intervalo de 109 y 35 m2/g con una distribución del diámetro y volumen de poros de 8,9-9,6 nm y 0,11-0,34 cm3/g, respectivamente. El análisis por DRX mostró la presencia de NiWO4, (NH4)4[NiMo6O24H6]•5H2O y WO3. Los análisis FT-IR determinaron la obtención de la estructura tipo Anderson, debido a las distintas flexiones y estiramientos de los grupos funcionales presentes. El precursor NiMo6-O/Al fue el más activo en la HDS, con un porcentaje de conversión de 72,75% e incluso fue más activo que el catalizador comercial AERO. Los resultados de HDS revelaron que la actividad catalítica en HDS se incrementa en el orden: NiMo6-O/Al > AERO > NiMo3W3-O/Al > NiW6–O/Al. La selectividad catalítica de precursores y el catalizador comercial (AERO) estuvo dirigida hacia cis-buteno.

5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine. The compounds were characterized by 1H and 13C nuclear magnetic resonance (NMR), elemental analyses and mass spectrometry. Some compounds showed promising luminescence properties in solution and in solid state; the absorption and emission characteristics were measured and the fluorescence quantum yield of two of the derivatives [4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-5-(3,4,5-trimethoxyphenyl)-1-phenyl-1 H -pyrazoline and 5-(4-chlorophenyl)-4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-1-phenyl-1 H -pyrazoline] were found to have excellent values compared to rhodamine B standard. Theoretical calculations at time-dependent density functional theory (TD-DFT) level are in agreement with the experimental measurements and are helpful to explain the electronic behavior.

Precursores catalíticos de polioxometalatos de FeMo, CoMo y NiMo tipo Anderson-Evans soportados sobre zeolita β en la hidrodesulfuración de tiofeno fue investigada. Los sólidos fueron caracterizados por análisis elemental (ICP plasma), área específica (SBET), difracción de rayos X (DRX) y espectroscopía infrarroja (FTIR). El soporte se impregnó con una solución acuosa del heteropolioxomolibdatos tipo Anderson-Evans de FeMo, CoMo y NiMo. El análisis elemental de Fe, Co, Ni y Mo dio resultados de acuerdo con la exactitud experimental de las relaciones atómicas nominales para cada precursor. La presencia de zeolita β, (NH4)3[FeMo6O24H6]•7H2O, (NH4)3[CoMo6O24H6]•7H2O y (NH4)4[NiMo6O24H6]•5H2O se verificó por DRX, mientras que el FTIR permitió asignar los estiramientos y flexiones de los grupos funcionales presentes en la estructura del heteropolioxomolibdato Anderson-Evans y la zeolita β. Los precursores catalíticos FeMo6/zeolita β, CoMo6/zeolita β y NiMo6/zeolita β mostraron mayor área específica (204-268 m2/g) que los heteropolioxomolibdatos tipo Anderson-Evans (1-3 m2/g). Los catalizadores provenientes de heteropolioxometalatos tipo Anderson-Evans de FeMo, CoMo y NiMo soportados en zeolita β presentaron mayor actividad HDS que los precursores no soportados (FeMo6/zeolita β y CoMo6/zeolita β), lo cual está asociado a la formación de mayor número de sitios activos.

The influences of reaction parameters on the etherification of phenols to obtain 1-bromo-2-aryloxyethane derivatives were evaluated. The compounds were prepared by direct etherification of phenols with 1,2-dibromoethane using anhydrous K2CO3 and acetonitrile as solvent reaction, at 80°C, in a reaction time of 6 h. Under these conditions, excellent yields (71%-94%) were obtained, with low yields of secondary products. The anhydrous K2CO3 was recycled by simple filtration, dried in vacuum, and reused. The compounds were characterized by conventional spectral data (MS and NMR). Larvicidal activity results showed a 100% larval mortality after 24-hour exposure to the compound 1-(2-bromoethoxy)-2-phenylbenzene., Facultad de Ciencias Agrarias y Forestales, Centro de Investigación y Desarrollo en Ciencias Aplicadas

El efecto del soporte modificado con cerio en precursores catalíticos de NiMo tipo Anderson sobre la hidrodesulfuración de tiofeno fue investigada. Los sólidos fueron caracterizados por área específica (SBET), difracción de rayos X (DRX) y espectroscopía infrarroja (FTIR). El soporte modificado con cerio se impregnó con una solución acuosa del heteropolioxomolibdato tipo Anderson de Ni. La presencia de (NH4)4[NiMo6O24H6]•5H2O y alúmina en fases gamma y gibbsita se verificó por DRX, mientras que el FTIR permitió asignar las características vibracionales de la estructura tipo Anderson, debido a los estiramientos y flexiones de los grupos funcionales presentes. Los soportes γ-Al2O3, γ-Al2O3-Ce y Ce/γ-Al2O3 mostraron mayor área específica (149-66 m2/g) que los precursores catalíticos NiMo6/γ-Al2O3, NiMo6/γ-Al2O3-Ce y NiMo6-Ce/γ-Al2O3 (76-36 m2/g). Los catalizadores provenientes de alúminas modificadas con cerio presentaron mayor actividad HDS que los obtenidos con alúmina no modificada, lo cual está asociado a la formación de mayor número de sitios activos.

Ni–Mo carbides supported on activated carbon were synthesized by carbothermal hydrogen reduction and the effect of the sulfidability on the thiophene hydrodesulfurization catalytic activity was studied. The X-ray diffraction patterns of Ni–Mo carbides showed the presence of β-Mo 2 C and NiC when the atomic ratio AR = Ni/(Ni + Mo) was between 0.25 and 0.75, while for AR = 1, it only was detected metallic Ni. The X-ray photoelectron spectroscopy results showed the distribution of different surface species in the passivated catalysts: Mo δ + (0 ≤ δ ≤ 2), Mo 4 + , Mo 6 + , Ni δ + and Ni 2 + . After sulfiding the carbides were modified in their surface and catalytic activity.

Temperature-programmed sulfiding (TPS) and temperature-programmed reduction of the sulfided catalysts (TPR-S) have been employed to evaluate Mo, Fe–Mo, Co–Mo and Ni–Mo carbide catalysts supported on activated carbon (AC). The carbides were prepared by carbothermal hydrogen reduction from co-impregnated precursors, and submitted to presulfiding prior to HDS. Samples of passivated catalysts prepared from the sulfates of Fe and Co contained variable amounts of sulfur, as shown by XPS and elemental analysis, while all samples showed increased sulfur contents after HDS. The TPS traces (up to 400 °C) of the Mo and Co–Mo samples exhibited two H2S consumption peaks, the first one starting at 100 °C and the second within the 400 °C isothermal region, located immediately after a H2S production peak centered at 400 °C for Mo and at 340 °C for Co–Mo. The Fe–Mo and Ni–Mo carbides exhibited a broad H2S consumption signal between 100 and 400 °C. The low temperature signals can be attributed to reduction of Mo(VI) oxide into Mo(V) or Mo(IV) sulfides, while the broad, higher temperature band is assigned to further reduction to the fully sulfided surface species. The TPR-S spectra showed three H2S evolution peaks, where the area of the first peak (assigned to reduction of sulfur species adsorbed on coordinatively unsaturated edge/corner sites) follows the order Co–Mo ≫ Ni–Mo ≈ Mo > Fe–Mo, which fully agrees with the order of HDS activities at steady state. Elemental analysis of the pre-sulfided AC support suggest that a large part of the sulfur consumed in sulfiding the catalysts is retained as elemental sulfur within the microporous structure of the support, although HRTEM observations confirm that MoS2-like structures are present in these samples. These results reinforce the importance of sulfided surface phases in HDS on carbides of transition metal catalysts. Transmission electron microscopy shows that activated carbon supported (M-)Mo carbide catalysts (M = Fe, Co, Ni) present MoS2-like fringes on top of bimetallic carbide crystals. Temperature-programmed techniques and elemental analysis prove that a large amount of sulfur is retained in the catalyst, likely within the slit-shaped microporous structure of the support. A good correlation was established between thiophene HDS activity at steady state and the size of a TPR peak of sulfided catalyst samples.

La sensibilizacion del dioxido de titanio con porfirinas es esencial para la generacion de especies reactivas del oxigeno inducida con luz visible. Sin embargo, estos sensibilizadores tienden a lixiviarse en el medio de reaccion. La distribucion del tamano de particula es una propiedad fundamental para caracterizar sistemas de particulas en suspension. En este trabajo se estudio la distribucion del tamano de particula de la tetracarboxifenilporfirina de cobre (II) anclada sobre dioxido de titanio por la tecnica de dispersion dinamica de luz. Los resultados indican que la tecnica de dispersion dinamica de luz es adecuada para determinar la estabilidad de estos sistemas, mostrando un solo tipo de particula para el sistema TCPPCu/TiO2 con diametro promedio de 211,1 nm.

The effect of passivation and presulfidation after carbiding of activated carbon-supported Fe–Mo, Co–Mo and Ni–Mo catalysts on their thiophene HDS activity was evaluated. Catalytic precursors were prepared by co-impregnation of the support with solutions of ammonium heptamolybdate and the promotor nitrates or sulfates. Carbiding was achieved by means of the carbothermal method, employing pure H 2 as reductant and the support as the carbon source. Carbided samples were submitted to one out of three types of procedures before HDS tests: (a) passivation at room temperature followed by presulfiding; (b) presulfiding (no passivation); and (c) neither passivation nor sulfiding before HDS. Samples of passivated catalysts prepared from the sulfates of Fe, Co or Ni contained variable amounts of sulfur, as shown by XPS and elemental analysis, while XRD showed only metals and mixed Fe 3 Mo 3 C or η-M 6 Mo 6 C 2 (M Co, or Ni) phases. The nitrate-derived catalysts only presented β-Mo 2 C and metals (XRD). Sulfur containing catalysts showed high initial activities although deactivate strongly during the first 40 min on the reaction stream, while the unsulfided nitrate-derived samples showed a more stable behavior and lower activities during the 2–3 h of testing. In general, samples submitted to passivation followed by presulfiding showed the higher steady state activities and those neither passivated nor sulfided were the less active. The results show the benefits of a passivating treatment on these carbon-supported catalysts, and point out to the importance of sulfided surface phases in HDS on carbides of transition metal catalysts.

Resumen en: This paper studies the effect of the presulfiding agent and the synthesis method on the catalytic activity of thiophene hydrodesulfurization (HDS), using...

In this work it is studied the effect of the type of precursor (sulfate vs. nitrate of promotor) and the synthesis method (conventional vs. carbothermal carbiding) on the thiophene hydrodesulfurization (HDS) activity of activated carbon supported Fe-Mo, Co-Mo and Ni-Mo carbides. Catalytic precursors were prepared by co-impregnation of the support with solutions of ammonium heptamolybdate and the promotor salt. Conventional carbiding consists of a temperature-programmed treatment under a CH4/H2 (1:4) atmosphere, while the carbothermal method employs pure H2. The passivated carbided solids were characterized by XRD and XPS. The presence of metals and Fe3Mo3C or M6Mo6C2 phases (M = Co or Ni) in samples from sulfate precursors and of β-Mo2C and metals in those from nitrate precursors was verified by XRD, whereas XPS showed the presence at the surface of Moδ+(0 ≤ δ ≤ 2), Mo4+, Mo6+, Fe3+, Co2+, Ni0 and Ni2+ species. The bimetallic carbides obtained from sulfate precursors retained sulfur on the surface, as shown by signals in the S 2p region, at 169 and 162 eV, assigned to S2− and SO42−, respectively. Prior to the catalytic reaction, the passivated carburized forms of carbon supported catalysts were presulfided in situ. The catalytic activity of carbides was strongly influenced by the type of precursor and slightly by the synthesis method. The activity of carbides obtained by the carbothermal method and with sulfate precursors was greater than that of the solids obtained by the conventional method and with nitrate precursors. The carbides obtained from nitrates showed increased catalytic activity when presulfided, suggesting that the carbides with sulfided surfaces or mixed carbo-sulfide species could be the active phase in HDS on carbide catalysts. The catalysts derived from sulfates showed higher activity than those obtained from nitrates, even without presulfiding, suggesting that sulfide from the precursor sulfate results in more active species than those obtained after presulfiding.