Molybdenum Salts Research Articles

Deposition and properties of mixed molybdenum sulfide (MoS2) and copper sulfide (CuxS) films on glass surface using elemental sulfur as a precursor

Mixed molybdenum sulfide (MoS2) and copper sulfide (CuxS) materials were synthesized on glass slides as a model substrate by successive ionic layer adsorption and reaction method using elemental sulfur as a sulfur source and solutions of copper (II/I) and molybdenum (IV) salts. X-ray diffraction data showed the presence of copper sulfides (anilite Cu7S4 and djurleite Cu31S16 phases), molybdenum disulfide and molybdenum oxide with adjustable crystalline phase composition dependent on the precursor exposure time and reaction temperature. Scanning electron microscopy images showed that the surface had a homogenous layer distribution at lower temperatures/short exposures and comprised of ~1 μm particles. X-ray photoelectron spectroscopy showed no oxidized sulfate (SO42−) compounds present on the sample surface while a thin MoO3 layer was found to cover the sample surface. Optical ultraviolet-visible spectroscopy showed mixed layers formed, containing optical properties of both MoS2 and CuxS. After annealing in an N2 atmosphere at 100 °C, the sample was composed primarily of MoS2 and copper sulfides in the crystalline phase with minimal residual S8. Usability of this mild mixed metal sulfide thin film preparation method on supports for sour natural gas catalyst synthesis is also discussed.

Relation of Structural and Chemical Parameters of Tar Hydroconversion Residue to Catalytic Properties of Nanosized Catalysts Based on Mo, Co, Ni, Al Compounds

At a pilot plant with a flow reactor, the hydroconversion of oil vacuum distillation residue (tar) was studied at a hydrogen pressure of 7 MPa, a temperature of 445°C, a feed space velocity of 2 h–1 in the presence of suspensions of nanosized particles of catalysts obtained in situ in the reaction zone from previously prepared in the feed of reverse emulsions of aqueous solutions of precursors: salts of molybdenum, nickel, cobalt, and aluminum. Based on the data of elemental analysis and 1H NMR spectra, the structural parameters of the hydrogenated feed vacuum distillation residues, are determined. The relationship between the structural and chemical parameters of the residues, conversion of raw materials, coke yield, and catalyst composition was established. Tar conversion and unsaturation of the vacuum residue, as structural parameter, increase in the series of Mo–Al, Ni, Mo–Co–Al, Mo, Mo–Co, Mo–Ni, Al catalysts.

Ce1.0Mo0.15Eu0.05Ox Aqueous Perovskites for Stable Near-Infrared Emission and Their Sensitivity toward Hydrogen Peroxide

We report a solvent free method to synthesize red fluorescent perovskites from oxide salts of cerium, molybdenum, and europium (CME perovskites). A combination of dry and wet grinding followed by annealing and calcination results in a crystalline and highly ordered structures of CME perovskites. The particle size obtained was surprisingly small (<100 nm) with aqueous dispersity and intense red fluorescence in the near-infrared (NIR) regime. The quantum yield of the CME perovskites was calculated to be 9.71%. We found that the metal oxide bond can be altered using hydrogen peroxide (H2O2) resulting in an enhanced fluorescence signal. Owing to its high sensitivity to low concentration levels of H2O2, the perovskites are utilized to detect hydrogen peroxide up to 1.17 nM in aqueous solution and 1.62 nM in a biological fluid (urine).

Assessment of some indicators of oral liquid in children with the pathology of the temior-lower under jaw joint

The problem of the relationship between dental and somatic health in children and adolescents is of interest to researchers and does not lose relevance. Firstly, this is due to a tendency to increase the frequency of somatic and dental diseases in children. Secondly, this is due to the fact that modern concepts of the development of diseases, new clinical forms of pathologies arise, research methods, diagnostics and treatment are improved. During the interaction of lysozyme with a substrate of Micrococcus lysodeikticus, substrate bleaching is observed, which is recorded spectrophotometrically. The degree of enlightenment is proportional to the activity of lysozyme, which was expressed in units/ml of oral fluid [Levitsky AP, 2005]. Catalase activity in the oral fluid was evaluated using a method based on the ability of hydrogen peroxide, which did not react with catalase, to combine with molybdenum salts into a stable orange complex. Thus, in children with TMJ disease, imbalances in the prooxidant-antioxidant system are observed; a decrease in catalase activity and an increase in the level of malondialdehyde, a decrease in antimicrobial protection and an increase in the degree of contamination of pathogenic and conditionally pathogenic microflora. In children with TMJ pathology, a significant decrease in the lysozyme content in the oral fluid and a simultaneous increase in urease activity relative to these healthy children were recorded. This suggests that in children with TMJ, there was a decrease in the level of antibacterial protection of the oral fluid, as a result of which the degree of contamination of the oral cavity with pathogenic and conditionally pathogenic microflora increased.

Hydroconversion of Vacuum Residue of a Blend of Western Siberian Oils in the Presence of Ex Situ Synthesized Suspensions of Nanosized Catalysts

Concentrated suspensions of nanosized МоS2, МоS2+Ni7S6, Ni7S6, Fe1– xS, and (NH4)0.25 · WO3 particles with an average size of 273–364 nm have been synthesized from reverse emulsions of aqueous solutions of molybdenum, nickel, iron, and tungsten salts in the presence of a sulfiding agent and hydrogen in oil vacuum distillation residues and tested in oil vacuum distillation residue hydroconversion running in an autoclave and a pilot flow system. The test results have shown that the highest activity in hydrogenolysis reactions is exhibited by Mo-containing catalysts. The kinetic characteristics have been determined; the heat of the hydroconversion process has been calculated.

Crystal structures and hydrogen-bonding analysis of a series of solvated ammonium salts of molybdenum(II) chloride clusters.

Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic com-pounds, especially when the cation or cations are primary ammonium salts. We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations. The crystal structures of bis-(anilinium) octa-μ3-chlorido-hexa-chlorido-octa-hedro-hexa-molybdate N,N-di--methyl-formamide tetra-solvate, (C6H8N)2[Mo6Cl8Cl6]·4C3H7NO, (I), p-phenyl-enedi-ammonium octa-μ3-chlorido-hexa-chlorido-octa-hedro-hexa-mol-yb-date N,N-di-methyl-formamide hexa-solvate, (C6H10N2)[Mo6Cl8Cl6]·6C3H7NO, (II), N,N'-(1,4-phenyl-ene)bis-(propan-2-iminium) octa-μ3-chlorido-hexa-chlo-rido-octa-hedro-hexa-molybdate acetone tris-olvate, (C12H18N2)[Mo6Cl8Cl6]·3C3H6O, (III), and 1,1'-dimethyl-4,4'-bipyridinium octa-μ3-chlo-rido-hexa-chlorido-octa-hedro-hexa-molybdate N,N-di-methyl-formamide tetra-solvate, (C12H14N2)[Mo6Cl8Cl6]·4C3H7NO, (IV), are reported and described. In (I), the anilinium cations and N,N-di-methyl-formamide (DMF) solvent mol-ecules form a cyclic R 4 2(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF mol-ecule forming a D(2) inter-action. The p-phenyl-enedi-ammonium cation in (II) forms three D(2) inter-actions between the three N-H bonds and three independent N,N-di-methyl-formamide mol-ecules. The dication in (III) is a protonated Schiff base solvated by acetone mol-ecules. Compound (IV) contains a methyl viologen dication with N,N-di-methyl-formamide mol-ecules forming close contacts with both aromatic and methyl H atoms.

Chromium-modified cobalt molybdenum nitrides as catalysts for ammonia synthesis

AbstractThe influence of chromium compounds on the properties of cobalt molybdenum nitrides was studied. CoMoO4 obtained by precipitation from cobalt and molybdenum salts was modified by the addition of chromium(III) nitrate. A mixture of cobalt-molybdenum nitrides, Co2Mo3N and Co3Mo3N, was formed by ammonolysis of modified CoMoO4. The concentration of Co2Mo3N decreases with increasing chromium content. The specific surface area of cobalt molybdenum nitrides consisting of 2 wt% of Cr atoms increased by 50% in comparison to pure cobalt molybdenum nitrides. The catalytic activity of obtained catalysts in ammonia synthesis process decreases with rising of chromium concentration.

Biosynthesis of isocitric acid in repeated-batch culture and testing of its stress-protective activity.

Biosynthesis of Ds(+)-threo-isocitric acid from ethanol in the Yarrowia lipolytica batch and repeated-batch cultures was studied. Repeated-batch cultivation was found to provide for a good biosynthetic efficiency of the producer for as long as 748h, probably due to maintenance of high activities of enzymes involved in the biosynthesis of isocitric acid. Under optimal repeated-batch cultivation conditions, the producer accumulated 109.6g/L Ds(+)-threo-isocitric acid with a production rate of 1.346g/Lh. The monopotassium salt of isocitric acid isolated from the culture liquid and purified to 99.9% was found to remove neurointoxication, to restore memory, and to improve the learning of laboratory rats intoxicated with lead and molybdenum salts. Taking into account the fact that the neurotoxic effect of heavy metals is mainly determined by oxidative stress, the aforementioned favorable action of isocitric acid on the intoxicated rats can be explained by its antioxidant activity among other pharmacological effects.

Highly Crystalized Co2Mo3O8 Hexagonal Nanoplates Interconnected by Coal-Derived Carbon via the Molten-Salt-Assisted Method for Competitive Li-Ion Battery Anodes.

Highly crystalized Co2Mo3O8 hexagonal nanoplates interconnected by coal-derived carbon have been successfully fabricated by the molten-salt-assisted method. The formation process of the nanostructural hybrids via molten salts is proposed. The eutectic salts with low melting points act as ionic liquid solvents and "molecular templates" at high temperature, making cobalt and molybdenum salts react in the form of bare ions to get the regular Co2Mo3O8 hexagonal nanoplates interconnected by conductive carbon. In addition, the crystallinity of Co2Mo3O8 hexagonal nanoplates is increased with the help of molten salts. The effects of temperature on morphology and electrochemical performance of the composites were studied. Thanks to the unique structure design, the optimal composite obtained by this simple low-cost strategy exhibits remarkable electrochemical performance as anodes for lithium-ion batteries, which reveals a high reversible capacity of 1075 mA h g-1 at 200 mA g-1 and 596 mA h g-1 at 1000 mA g-1 after 100 cycles. More importantly, the sample shows good rate capability with a high capacity of 533 mA h g-1 at a high current density of 4000 mA g-1. The molten-salt-assisted method is also applicable to design and synthesize other metal oxide-based Li-ion battery anodes.

Синтез модифицированных молибденом и вольфрамом композиционных систем на основе бисорбента из рисовой шелухи

The article presents results of the synthesis of a new composite material modified with polyvalent metals. Rice husk was chosen as a raw material for obtaining a carrier – a bisorbent consisting of carbon and amorphous silicon oxide. The sorption material was obtained from the products of thermal decomposition of rice husks. Further it was modified with ammonium salts of molybdenum and tungsten: (NH4)6Mo7O24·4H2O and (NH4)2O·12WO3·5H2O in Mo/W ratios: 5/5 wt. %, 10/5 wt. % and reducted by heating in a stream of hydrogen. The registration of the voltammetric curves in the medium of 1-methyl-4-piperidone was carried out in various background electrolytes: 0.2 M Li2SO4, pH = 6.36 and 0.1 M KOH, pH = 13, 2,5·10–2 M K2HPO4 + 2,5·10–2 M NaH2PO4, pH = 6.86. Differential voltammetric curves were analyzed. The electrochemical activity of the obtained modified composites in the potential range from -1.2 V to 0.5 V was determinated. The mechanism of the proceeding electrochemical processes on these modified electrode materials has been studied. The possibility of further use of synthesized composite systems based on bisorbents from the rice husk for the electrochemical reduction of 1-methyl-4-piperidone was shown.

Про-антиокcидантна рівновага в печінці та м’язах cтерляді за дії штучного гіпобіозу й анестезії

&lt;p&gt;The pro-antioxidant balance in the liver and muscles of sterlet under the influence of artificial carbonic dioxyde hibernation and anaesthesia have been studied. In experiments were used two-years old sterlet weighing 170–210 g which were grown under conditions of a closed water supply. Four groups of five copies of each fish were formed: Control group I (fish remained intact); Group II (the clove oil was used for fish anaesthesia, which was added to the water); Group III (fish were hibernated by carbon dioxide); Group IV - control of hibernation (after complete recovery from carbon dioxide hibernation, these groups of fish were returned to the pool of incubation shop for her follow–up). The research of intensity of the formation products of peroxide oxidation of lipids (POL) in the body of sterlet in the experimental conditions were conducted by determining the content of thiobarbituric acid active products (TBA–active products) in the muscles and liver that are generated at the final stages of lipid peroxidation. The content of malonic dialdehyde (MDA), one of the intermediate products of lipid peroxidation of membrane was determined photometrically by the concentration of colored complex formed by its reaction in the acidic environment of the two molecules of thiobarbituric acid (TBA). Catalase activity was determined by the ability of hydrogen peroxide to form the stable colored complex with Molybdenum salts. The results support the adaptive character in fluctuations in the antioxidant protection system by the actions of carbon dioxide hibernation and anaesthesia on the sterlet body. This also contributes to usage of these conditions in fish transportation at long distances without stress factors.&lt;/p&gt;

Paradoxical influence of combined effect of Semax and ammonium molybdate on learning and memory in rats

The combined effect of Semax with water solutions of plumbum diacetate (10–7 M) and ammonium molybdate (10–5 M) on the two-way active avoidance learning in rats in the shuttle chamber was studied. It was established that both salts of heavy metals oppress the learning and memory; plumbum diacetate caused larger oppression. Semax slowed down the development of the conditioned response but counteracted the negative influence on this process from the side of both metals. The effect of Semax on the development of the avoidance reaction in the presence of ammonium molybdate, which oppressed the avoidance by itself, paradoxically intensified. During the combined effect of the peptide and ammonium molybdate, the development of the conditioned reaction occurred much faster than against the background of Semax without the combination with molybdenum. In total, data obtained indicate a counteraction of Semax to neurotoxic effect of plumbum and molybdenum salts. Since oxidative stress is the main mechanism of neurotoxic effect of heavy metals, the indicated positive effect of Semax can, in our opinion, confirm the presence of antioxidant properties in the spectrum of the peptide pharmacological activity.

A complex influence of chromium and zinc citrates on antioxidant defense system in rats’ organism with an experimentally induced diabetes mellitus

Introduction. Since the diabetes mellitus is a genetically predetermined disease, preventive measures to postpone the onset of the disease or to avert its appearance are especially important for people from risk group. That is why it is so important to evaluate role of some microelements in diabetes prevention. In particular, it is known that zinc plays an important role in insulin synthesis, accumulation and release by β-cells in pancreas, while its synergist chromium activates insulin receptors on cell membranes.The aim of the study – to establish the effect of chromium and zinc citrates on the functioning of antioxidant system and on the content of lipid peroxidation products in rats’ blood and tissues under the condition of experimental streptozotocin-induced diabetes mellitus.Methods of the research. Experiments were conducted on white laboratory rats which were divided into three groups: 1 – the control group, 2, 3 – research groups. Rats from the 1 and 2 groups received only basic ration, while chromium and zinc citrates solutions were added to the water of animals from the group 3 in 25 mcg Cr/kg and 50 mg Zn/kg of body weight dosage. An experimental diabetes mellitus (EDM) was induced in animals from 2 and 3 research groups on the 25th day of the experiment, after 24-hour fasting, by intraperitoneal injection of Streptozotocin in 45 mg/kg bodyweight dosage. Materials for the research were rats’ blood and tissues that were received after decapitation. The content of lipid hydroperoxides in blood and tissues was determined by a method that requires protein sedimentation by a trichloroacetic acid (TCA) and further addition of ammonium thiocyanate to the solution. The MDA content was measured by means of a colored reaction of malondialdehyde with the thiobarbituric acid. The activity of superoxide dismutase (SOD, EC 1.1.15.1.) was determined by a method where nitrotetrazolium is reduced by superoxide radicals. Glutathione peroxidase activity (GP, EC 1.11.1.9.) was measured by the speed of reduced glutathione oxidation. The activity of catalase (EC 1.11.1.6.) was measured by hydrogen peroxide ability to form a stable colored complex with molybdenum salts. The activity of glutathione reductase (GR, EC 1.6.4.2) was measured by a speed of glutathione reduction in the presence of NADPH. The content of reduced glutathione was gauged by the level of thionitrophenol anion formation as a result of SH-groups of glutathione and 5.5-dithiobis-(2-nitrobenzoic acid) reaction.Results and Discussion. It was determined during the research that lipid hydroperoxides (LHP) and MDA contents in rats’ blood, skeletal muscles and pancreas were increased, while the activity of antioxidant defense system enzymes and reduced glutathione content were decreased under the condition of streptozotocin-induced DM. Under the condition of combined chromium and zinc citrates addition to the diet of rats from group 3 we observed the credible decrease of lipid hydroperoxides content, while the increased activity of antioxidant enzymes compared to those indexes from group 2.Conclusions. The received results indicate the normalization of lipids peroxidation processes and antioxidant defense under the influence of chromium and zinc citrates in animals with hyperglycemia. The further research of antioxidant properties of organic compounds of these microelements will let to develop medical remedies for diabetes prevention and treatment.

Supported Molybdenum Catalysts for the Deoxydehydration of 1,4-Anhydroerythritol into 2,5-Dihydrofuran.

Efficient deoxygenation strategies are crucial for the valorization of renewable feedstocks. Deoxydehydration (DODH) enables the direct transformation of two adjacent hydroxyl groups into a double bond. Supported molybdenum-based catalysts were utilized for the first time in DODH. MoOx /TiO2 showed superior catalytic activity compared to common molybdenum salts. The catalyst efficiently converted 1,4-anhydroerythritol into 2,5-dihydrofuran in the presence of 3-octanol as reducing agent, showing high reproducibility and stability.

Characterization of Fresh Oil Hydro Treating Catalysts

Catalysts are of great importance in catalytic processes. Key features of oil hydrotreating catalysts are highlighted. These catalysts play a significant role in removing impurities, as sulfur and other hetero-atoms existing in these oil fractions. These catalysts are composed of mainly, molybdenum salts spread in the porous structure of the carrier, mainly γ-Alumina (γ-Al2O3). Other metal salts supporting the action of the catalytic activity of Molybdenum, as Cobalt, Nickel, are added. The first step in the process of catalyst production is the drying of the wet salts mixture to remove moisture. The oxidic precursor is produced by the calcination of the dried mixture. The choice of the appropriate catalyst is based on its ability to maintain a high level of activity for long periods before re-activation. This ability depends on the chemical composition and on the porous structure of the carrier, which ensures the appropriate properties such as the density of active centers, particle strength, and porous structure parameters. Also, the catalyst resistance to chemical poisons destroying active centers in particular, is considered as a limiting factor in selecting the catalyst.

MoV Reagents in Organic Synthesis

AbstractThe use of MoV reagents, and in particular MoCl5, in organic synthesis is surveyed. The oxidative treatment of aromatic substrates is the most common application. The unique properties of these reagents are due to their high oxidative power combined with exquisite Lewis acid properties. In several examples MoV reagents outperform other common oxidative coupling reagents. C–C bond formation through inter‐ and intramolecular oxidative coupling can lead to selective formation of five‐ to eight‐membered ring systems. Mechanistic investigations of the courses of reactions involving MoV reagents and aromatic substrates indicate that radical cations are initially formed, entering the oxidative coupling scenery. Mechanistic studies reveal that Scholl‐type conversion is unlikely. However, over‐oxidation of the product seems to be the rationale for the selective conversion. Reduction occurs during workup, through the action of the lower‐valency molybdenum salts present. This opens up the pathway to oxidative domino sequences. MoCl5 has already been used in the key steps of the syntheses of several natural products or their analogues. In addition, MoCl5 can serve in chlorination reactions and in stereoselective isomerization by template formation, and also as a precursor for alkyne trimerization.

In SituGeneration of Molybdenum-Based Catalyst for Alkyne Metathesis: Further Developments and Mechanistic Insights

Molybdenum-based catalysts are among the best candidates to achieve alkyne metathesis. They can be either well-defined carbynes, previously synthesized before their use, but also prepared in situ upon using stable molybdenum carbonyl complexes, or high oxidation state molybdenum salts that need a previous alkylation, both type of precursors being “activated” by hydroxyl-containing compounds such as phenols and silanols. This paper is presenting studies made on these systems, directed towards the knowledge of the reaction paths leading to the active species, and in particular to define the essential role of hydroxyl-containing co-catalyst in the formation of the active species, still ill-defined. From an analysis of the byproducts formed during the reaction, as well as of the initial products, reaction paths to access catalytic carbyne species is suggested, where the ligand environment consists of phenoxy (or siloxy) groups, typically required and identified to lead to alkyne metathesis in the case of well-defined catalysts.

Aquatic acute toxicity assessments of molybdenum (+VI) to Daphnia magna.

Generally, molybdenum (Mo) metals in the environment are very rare, but wastewater discharges from industrial processes may contain high concentrations of Mo, which has the potential to contaminate water or soil if not handled properly. In this study, the impact of three common compounds of hexavalent Mo (sodium molybdate (Na2MoO4‧2H2O), ammonium molybdate ((NH4)6Mo7O24‧4H2O) and molybdenum trioxide (MoO3)) in an aquatic system were assessed based on 48-h exposure acute toxicity to Daphnia magna (D. magna). The LC50 toxicities for associated conjugate ions including Na(+), Cl(-), SO4(2-), and NH4(+) were determined. Furthermore, the LC50 values for the three forms of hexavalent Mo were determined, and the acute toxicities of the Mo forms were found to follow the order: (NH4)6Mo7O24‧4H2O > MoO3 > Na2MoO4‧2H2O in solution. (NH4)6Mo7O24‧4H2O exhibited the lowest LC50 of 43.3 mg L(-1) (corresponding to 23.5 mg Mo L(-1)) among the three molybdenum salts. The research confirmed that the toxicity of molybdenum in the aquatic system is highly dependent on the form of molybdenum salts used, and is also associated with the influence of the background water quality.

Generation of acidic sites in Al, Ga, In salts of molybdenum and tungsten Keggin-type heteropolyacids. DFT modeling and catalytic tests

The catalytic properties, both redox and acidic, of 12-tungsto- and 12-molybdo-phosphoric Al3+, Ga3+, In3+ salts were studied. As a model reaction the gas phase ethanol conversion was used. On different sites (redox and acidic) various products are obtained (acetaldehyde and diethyl ether/ethylene respectively). Catalytic activity of MePW and MePMo salts was theoretically predicted, using both periodic and cluster models. Performed experiments confirm the theoretical prediction concerning the influence of addenda atoms (W and Mo) and various counter-cations (Al3+, Ga3+, In3+) on the catalytic properties of studied systems.

Metal nature effect on catalytic reactions in furfural-H2O2-H2O-group V or VI d-metal salt systems in acid media

Homogeneous catalytic reactions of furfural oxidation by hydrogen peroxide in an aqueous medium in the presence of catalytic amounts of a vanadium, niobium, molybdenum, or chromium salt have been studied to compare them with the acid-autocatalytic reaction. The formation of peroxo complexes of the corresponding metals has been established. The interaction of these peroxo complexes with the carbonyl group of furfural affords organic metal-containing peroxides. The subsequent transformations of these peroxides in the presence of the indicated catalysts lead to different dominant final products. This is explained by different mechanisms of the oxidation of the key intermediates, namely, 2-formyloxy- and 2-hydroxyfurans. In the presence of the vanadium and molybdenum salts, the catalytic role of the resuting carboxylic acids is insignificant, as distinct from what is observed in the acid-autocatalyzed reaction.