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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]

Herein we report the synthesis of unsupported bimetallic CoMo and trimetallic CoNiMo sulfide catalysts prepared by thermal decomposition (ex situ activation) of carbon-containing precursors and varying the nickel concentration for the hydrodesulfurization (HDS) of dibenzothiophene. The catalysts prepared were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma mass spectrometry and BET surface area measurements. The results from the characterization showed that the addition of an alkyl chained precursor results in non-porous catalysts with low surface area and high carbon content, which negatively affects the formation of crystalline phases such as molybdenum sulfide and their performance in the HDS reaction. Furthermore, the addition of nickel has a negative effect on the catalysts since it was observed that when it was added, the reaction rate values decreased and the catalyst with the highest catalytic activity turned out to be the CoMo catalyst. Although nickel catalysts generally have more affinity for hydrogenation reactions, unsupported trimetallic catalysts showed a preference for the direct desulfurization pathway. [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]

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]

An adequate wound dressing reduces time of healing, provides cost-effective care, thereby improving patients' quality life. An antimicrobial bioactivity is always desired, for that reason, the objective of this work is to design an antimicrobial nanocomposite of chitosan/silver nanocrystals/graphene oxide (ChAgG). ChAgG nanostructured composite material is composed of chitosan from corn (Ch), and silver nanocrystals from garlic (Allium sativum). The nanocomposite obtained is the result of a series of experiments combining the graphene oxide (GrOx) with two members of the Amaryllidaceae family; garlic and onion (Allium cebae), which contain different sulfur materials. The characterization arrays confirmed the successful production of silver crystal, graphene oxidation and the blending of both components. The role of the chitosan as a binder between graphene and silver nanocrystals is proved. Moreover, the study discusses garlic as an optimal source that permits the synthesis of silver nanocrystals (AgNCs) (⁓ 2 to 10 nm) with better thermal and crystallinity properties. It was also confirmed the successful production of the ChAgG nanocomposite. Escherichia coli and Staphylococcus aureus were used to demonstrate the antibacterial bioactivity and L-929 fibroblast cells were utilized to visualize their biocompatibility. The proposed ChAgG nanomaterial will be useful for functionalizing specific fiber network that represents current challenging research in the fabrication of bioactive wound dressings., (© 2023. The Author(s).)

To achieve sulfur content in gas oil at a near-zero level, new catalysts with improved hydrogenation functions are needed. In this work, new Ni-Mo-Mo hydrodesulfurization (HDS) catalysts supported by Al 2 O 3 -CeO 2 materials were synthesized to evaluate their efficiency in the reaction of HDS with dibenzothiophene (DBT). Al 2 O 3 -CeO 2 supports different CeO 2 loadings (0, 5, 10 and 15 wt.%) and supported NiMoW catalysts were synthesized by sol-gel and impregnation methods, respectively. The physicochemical properties of the supports and catalysts were determined by a variety of techniques (chemical analysis, XRD, N 2 physisorption, DRS UV-Vis, XPS, and HRTEM). In the DBT HDS reaction carried out in a batch reactor at 320 °C and a H 2 pressure of 5.5 MPa, the sulfide catalysts showed a dramatic increase in activity with increasing CeO 2 content in the support. Nearly complete DBT conversion (97%) and enhanced hydrogenation function (HYD) were achieved on the catalyst with the highest CeO 2 loading. The improved DBT conversion and selectivity towards the hydrogenation products (HYD/DDS ratio = 1.6) of this catalyst were attributed to the combination of the following causes: (i) the positive effect of CeO 2 in forcing the formation of the onion-shaped Mo(W)S 2 layers with a large number of active phases, (ii) the inhibition of the formation of the undesired NiAlO 4 spinel phase, (iii) the appropriate textural properties, (iv) the additional ability for heterolytic dissociation of H 2 on the CeO 2 surfaces, and (v) the increase in Brønsted acidity.

Nanotubes made of non-concentric and multiple small layers of porous MoS 2 contain inner pores suitable for membrane applications. In this study, molecular dynamics simulations using reactive potentials were employed to estimate the stability of the nanotubes and how their stability compares to macroscopic single- (1L) and double-layer MoS 2 flakes. The observed stability was explained in terms of several analyses that focused on the size of the area of full-covered layers, number of layers, polytype, and size of the holes in the 1L flakes. The reactive potential used in this work reproduced experimental results that have been previously reported, including the small dependency of the stability on the polytype, the formation of S-S bonds between inter- and intra-planes, and the limit of stability for two concentric rings forming a single ring-like flake.

The effect of adding iron, cobalt or nickel to a prepared niobium-supported catalyst using mesoporous silica SBA-15 as a support was evaluated in the hydrodeoxygenation (HDO) reaction of anisole, chosen as a model compound in lignocellulosic biomass derived bio-oil. HDO activity as well as selectivity toward O-free products were highly dependent on the catalyst formulation: Ni incorporation showed the highest anisole conversion and selectivity to deoxygenated products, followed by Co and Fe counterparts. The activity was explained in terms of acidity, metal surface exposure and reducibility as a function of the interaction between the phases present. Regarding the characterization results, the better performance of NiNb/SBA-15 was associated with its lower acidity, higher Nb/Si surface exposure, NbO 2 /Nb 2 O 5 ratio and better interaction between Ni and Nb species., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

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 60 Co 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., (Copyright © 2018 Elsevier Ltd. All rights reserved.)