乙醇辅助的化学沉积法制备硫化型Mo/γ-Al2O3加氢脱硫催化剂

以硫代乙酰胺为硫源,钼酸钠为钼源,乙醇为分散剂,采用化学沉积法制备了MoS₃/Al₂O₃催化剂前驱体,再用H₂高温处理得到高分散硫化型MoS₂/γ-Al₂O₃催化剂,运用N₂吸附-脱附、X射线光电子能谱以及高分辨透射电子显微镜等技术对MoS₂/γ-Al₂O₃催化剂进行了表征,并以二苯并噻吩作为模型化合物评价了催化剂的加氢脱硫(HDS)活性.结果表明,与浸渍法相比,所制催化剂具有更大的比表面积和孔体积、更高的活性金属分散度、更佳的Mo物种硫化度以及更短的MoS₂片层长度和更高的堆积度,因而在二苯并噻吩HDS反应中表现出远优于浸渍法所制催化剂的活性.乙醇可通过S?H-O氢键吸附至MoS₃纳米粒子表面,可有效防止其生长和团聚,起到分散剂的作用.     

Investigation on the Growth Mechanism of Cu2MoS4 Nanotube,Nanoplate and its use as a Catalyst for Hydrogen Evolution in Water

Cu₂MoS₄ is a ternary transition‐metal sulfide that shows great potential in the field of energy conversion and storage, namely catalytic H₂ evolution in water and Li‐, Na‐ or Mg‐ion battery. In this work, we report on a growth mechanism of the single‐crystalline Cu₂MoS₄ nanotube from (NH₄)₂MoS₄ salt and Cu₂O nanoparticle. By probing the nature and morphology of solid products generated in function of reaction conditions we find that the crystalline Cu(NH₄)MoS₄ nanorod is first generated at ambient conditions. The nanorod is then converted into Cu₂MoS₄ nanotube under hydrothermal treatment due to the Kirkendall effect or a selective etching of the Cu₂MoS₄ core. Extending the hydrothermal treatment causes a collapse of nanotube generating Cu₂MoS₄ nanoplate. The catalytic activities of these sulfides are investigated. The Cu₂MoS₄ shows superior catalytic activity to that of Cu(NH₄)MoS₄. Catalytic performance of the former largely depends on its morphology. The nanoplate shows superior catalytic activity to the nanotube, thanks to its higher specific electrochemical surface area.     

Titania-supported mixed HPMoV polyoxometallates as precursors of hydrodesulfurization catalysts

HDS catalysts were prepared by loading H₃PMo₁₂O₄₀ or H₄PMo₁₁V₁O₄₀ polyoxometallates on TiO₂ (0.5 and 1.0 mmol (Mo+V)). Activity of the catalysts was tested in the HDS of thiophene. The activity of catalysts of low concentration was 2–3 times higher than the activity of those of high concentration. Temperature programmed reduction (TPR) and IR spectroscopy were used to determine the properties of the catalyst. TPR measurements proved that vanadium promotes and stabilizes HDS activity due to an increase in the Mo⁵⁺/Mo⁴⁺ ratio.     

The role of Rh on a substituted Al Anderson heteropolymolybdate: Thermal and hydrotreating catalytic behavior

The influence of Rh heteroatom on the molybdenum reducibility in the Anderson-type heteropolyoxomolybdate structure of formula (NH₄)₃[RhMo₆O₂₄H₆]·7H₂O was investigated by means of TPR technique. With comparative purposes, the thermal behavior in non-reducing conditions was also carried out by means of TGA-DTA studies. The study was performed by XRD, SEM, EDAX and FTIR-Raman techniques. Results were related to those preliminary measurements over other XMo₆ Anderson phases. Likewise, Rh(III)-Al(III) formal replacement in the RhMo₆ structural arrangement was proved. The formation of a solid solution in a limited range of composition (up to 0.25 Rh) was established in order to explore the catalytic performance of γ-Al₂O₃ supported planar heteropolyoxomolybdate, aiming at optimizing the noble metal content in the catalytic system. Preliminary measurements of RhMo₆/γ-Al₂O₃ and (Rh, Al)Mo₆/γ-Al₂O₃ activity for HDS and HYD processes were also performed. These results were compared to those obtained for CoMo₆/γ-Al₂O₃ system in similar operating conditions and other conventional catalytic systems. The potentiality and scope of RhMo₆ catalytic system for the HDS and HYD processes were analyzed.     

Cobalt salts of decamolybdodicobaltic acid as precursors of the highly reactive type II CoMoS phase in hydrorefining catalysts

Catalysts have been synthesized using the Anderson polyoxometalates (POMs) (NH₄)₄[Ni(OH)₆Mo₆O₁₈] (NiMo₆POM), (NH₄)₆[Co₂Mo₁₀O₃₈H₄] · 7H₂O (Co₂Mo₁₀POM), and H₆[Co₂Mo₁₀O₃₈H₄] (Co₂Mo₁₀HPA) as the precursors and hydrogen peroxide as the solvent. The catalysts have been characterized by low-temperature nitrogen adsorption, XPS, and HRTEM. Their catalytic properties have been tested in thiophene hydrodesulfurization and in the hydrodesulfurization and hydrogenation of components of diesel oil. The active phase of the catalysts synthesized using the POMs is the type II CoMoS phase in which the mean plate length is 3.6–3.9 nm and the mean number of MoS₂ plate per plate packet is 1.8–2.0. Use of hydrogen peroxide provides an efficient means to reduce the proportion of Co²⁺ promoter atoms surrounded by oxygen in the case of an impregnating solution containing both an ammonium salt of a heteropoly acid and a Co²⁺ salt. In the catalysts synthesized using cobalt salts of Co₂Mo₁₀HPA, the support surface contains the multilayer type II CoMoS phase and cobalt sulfides. These catalyst show high catalytic properties in thiophene hydrogenolysis and diesel oil hydrorefining. Models are suggested for the catalysts synthesized using Anderson POMs.     

Room‐Temperature and Aqueous‐Phase Synthesis of Plasmonic Molybdenum Oxide Nanoparticles for Visible‐Light‐Enhanced Hydrogen Generation

A straightforward aqueous synthesis of MoO_3?x nanoparticles at room temperature was developed by using (NH₄)₆Mo₇O₂₄?4 H₂O and MoCl₅ as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as‐prepared products are nanoparticles with diameters of 90–180 nm. The diffuse reflectance UV‐visible‐near‐IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible‐light and near‐infrared region, such nanostructures exhibit an enhancement of activity toward visible‐light catalytic hydrogen generation. MoO_3?x nanoparticles synthesized with a molar ratio of Mo^VI/Mo^V 1:1 show the highest yield of H₂ evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as‐prepared plasmonic MoO_3?x nanoparticles, which reveals its potential application in visible‐light catalytic hydrogen production.     

Highly active CoMo HDS catalyst for the production of clean diesel fuels

HY–Al₂O₃-supported CoMo catalysts with a chelating agent and phosphorus for the hydrodesulfurization (HDS) of diesel fractions were prepared. The activity measurements with the prepared catalysts were carried out with straight-run light gas oil feedstocks in a pilot plant under industrial hydrotreating conditions. As a result, Cosmo Oil Co., Ltd. developed a new CoMoP/HY–Al₂O₃ catalyst, C-606A, which had three times higher HDS activity than the conventional CoMoP/Al₂O₃ catalyst. Commercial operations to produce ultra-low sulfur diesel (ULSD) with C-606A have successfully demonstrated its high performance and high stability. This catalyst has an extremely high activity, which enables to achieve <10-ppm sulfur in products in diesel hydrotreater designed to produce 500-ppm sulfur diesel fuels. Mo K-edge EXAFS, TEM and FT-IR of adsorbed NO were performed to investigate the nature of the active sites on the developed catalysts. The results showed that the new catalyst has multiple layers of MoS₂ slabs and the edges of MoS₂ are mainly occupied by Co–Mo–S phases. XPS and FT-IR were used to investigate the sulfiding behavior of Co and Mo in the formation process of the active sites during sulfidation. The results showed that addition of carboxylic acid to the impregnation solution postponed the sulfidation of Co at low temperatures, thereby increasing formation of the Co–Mo–S phase.     

Ultra Deep Hydrodesulfurization of Gas Oils Over Sulfide and/or Noble Metal Catalysts

Deep hydrodesulfurization (HDS) of sterically hindered sulfur compounds in gas oils will require enhanced hydrogenation activity to hydrogenate the aromatic rings of the sulfur compounds. Although H₂S is known to inhibit the direct HDS route for most of the sulfided catalysts, its promotion to the hydrogenation and subsequent HDS was newly observed for unsupported MoS₂. This promotion suggests that ultra deep HDS over sulfide catalysts can be achieved along with high metal loading, minimal support-metal interactions and optimal dependence on the Ni species. On the other hand, the strong hydrogenation activity of sulfur-tolerant noble metal catalysts suggests that ultra deep HDS as well as deep aromatics saturation can be achieved. This paper discusses recent catalytic approaches for ultra deep HDS using conventional sulfide catalysts and/or noble metal catalysts, such as the newly developed Pd-Pt/Yb-USY zeolite catalyst.     

Keplerate巨型纳米多孔聚氧钼酸盐作为可重复使用催化剂用于合成1,2,4,5-四取代咪唑(英文)

The Keplerate‐type giant nanoporous isopolyoxomolybdate (NH4)42[MoVI72MoV60O372‐(CH3COO)30(H2O)72], denoted {Mo132}, has been used as a catalyst for the synthesis of1,2,4,5‐tetrasubstituted imidazoles by the one‐pot, four‐component thermal reaction of benzil with aromatic aldehydes, primary amines, and ammonium acetate under solvent‐free conditions. The catalyst was prepared according to a previously published literature procedure using inexpensive and readily available starting materials, and subsequently characterized by FT‐IR, UV and X‐ray diffraction spectroscopy, as well as microanalysis. The results showed that {Mo132} exhibited high catalytic activity towards the synthesis of 1,2,4,5‐tetrasubstituted imidazoles, with the desired products being formed in good to high yields. Furthermore, the catalyst was recyclable and could be reused at least three times without any discernible loss in its catalytic activity. Overall, this new catalytic method for the synthesis of 1,2,4,5‐tetrasubstituted imidazoles provides rapid access to the desired compounds following a simple work‐up procedure, and avoids the use of harmful organic solvents. This method therefore represents a significant improvement over the methods currently available for the synthesis of tetrasubstituted imidazoles.     

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds and their morphology and application in catalysis: III. Catalytic properties of massive Ni-Mo sulfide catalysts synthesized using mechanochemical activation

The precursors of massive Ni-Mo catalysts for hydrotreating processes, which were synthesized by the mechanochemical activation of a mixture of nickel hydroxocarbonate NiCO₃·2Ni(OH)₂·nH₂O and ammonium paramolybdate (NH₄)₆Mo₇O₂₄ · 4H₂O, were sulfidized. Their structure was studied by X-ray diffraction analysis and high-resolution electron microscopy. It was found that MoS₂ packets, which are characterized by the presence of structural defects and geometric curvature, are the constituents of the massive catalysts. The catalyst also includes a phase of Ni₃S₂ and regions containing a complex Ni-Mo-S phase. The catalytic tests of the synthesized catalysts in the model reactions of 1-methylnaphthalene and dibenzothiophene conversions showed that the catalyst whose precursor was a heteropoly compound with the Anderson structure after the stage of mechanochemical activation exhibited the highest activity.     

Sustainable activation of peroxymonosulfate by the Mo(IV) in MoS2 for the remediation of aromatic organic pollutants

Although MoS₂ has been proved to be a very ideal cocatalyst in advanced oxidation process (AOPs), the activation process of peroxymonosulfate (PMS) is still inseparable from metal ions which inevitably brings the risk of secondary pollution and it is not conducive to large-scale industrial application. In this study, the commercial MoS₂, as a durable and efficient catalyst, was used for directly activating PMS to degrade aromatic organic pollutant. The commercial MoS₂/PMS catalytic system demonstrated excellent removal efficiency of phenol and the total organic carbon (TOC) residual rate reach to 25%. The degradation rate was significantly reduced if the used MoS₂ was directly carried out the next cycle experiment without any post-treatment. Interestingly, the commercial MoS₂ after post-treated with H₂O₂ can exhibit good stability and recyclability for cyclic degradation of phenol. Furthermore, the mechanism for the activation of PMS had been investigated by density functional theory (DFT) calculation. The renewable Mo⁴⁺ exposed on the surface of MoS₂ was deduced as the primary active site, which realized the direct activation of PMS and avoided secondary pollution. Taking into account the reaction cost and efficient activity, the development of commercial MoS₂ catalytic system is expected to be applied in industrial wastewater.     

硫代硫酸铵对 CoMo 和 NiMoP 催化剂的预硫化

 采用硫代硫酸铵预硫化 CoMo 和 NiMoP 催化剂, 考察了预硫化剂的负载量对催化剂加氢脱硫活性的影响. 对于 CoMo 催化剂, 预硫化剂含量适中, 氢气活化后脱硫活性优于硫化氢硫化的对照催化剂. 预硫化过程中产生的 SO42?可修饰 Al2O3 载体, 减弱了活性相与金属的相互作用, 这可能是催化剂活性增加的原因. 硫代硫酸铵含量过低, 导致催化剂硫化不完全, 脱硫活性下降, 而硫化剂含量过高, 使活性颗粒长大, 因而活性中心数量减少, 脱硫活性降低. NiMoP 催化剂的活性金属含量高, 不易被硫代硫酸铵充分硫化, 导致预硫化催化剂活性低于对照的 NiMoP 催化剂.     

Cobalt-promoted MoS2 nanosheets: A promising novel diesel hydrodesulfurization catalyst

MoS₂ has been commonly used as a catalyst in hydrodesulfurization (HDS) of petroleum cuts in crude oil refineries. In this study, the synthesis of unsupported MoS₂ and Co-promoted MoS₂ nanosheets produced from molybdenum oxide and thiourea is reported. The synthesized samples were characterized by using x-ray fluorescence, x-ray diffraction, Brunauer–Emmett–Teller (BET), temperature-programmed reduction, thermal gravimetric analysis, and transmission electron microscopy methods, and then they were utilized for HDS of diesel through a fixed-bed catalytic reactor. Results indicated that a cobalt promoter affected both the number and the performance of active sites of the molybdenum sulfides, and the activity of the promoted MoS₂ catalyst was consistently higher than that of the MoS₂ catalyst. More significantly, the activity of the promoted catalyst was slightly declined during 48 h continuous HDS reaction, which indicated the stability of this catalyst. Additionally, during 12 h of test run, the HDS activity of the promoted catalyst was about 60% higher than MoS₂ one.     

Two novel molybdenum complexes containing [Mo2O2S2]2+ fragment: synthesis,crystal structures and catalytic studies

Mo₂O₂S₂(HGly)(Gly)₂ 1 and K₆[Mo₂O₂S₂(nta)₂][Mo₂O₂S₂(ntaH)₂]^·4H₂O 2 were synthesized by the reactions of (NH₄)₂MoS₄ and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol–water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV–visible spectra, TG–DTA and XPS. X‐ray crystallographic structural analyses revealed that compound 1 is a binuclear Mo? S? glycinate complex, a glycinate ligand is coordinated to each molybdenum atom through its amine nitrogen and carboxylato oxygen, respectively, and the third glycinate acts as a bridge through its two carboxylato oxygens linking the two molybdenum atoms. Compound 2 is also a binuclear Mo? S complex with two nitrilotriacetate ligands, each of which is coordinated to a molybdenum atom via its two β‐carboxylato oxygens and a nitrogen atom. Simultaneously, each molybdenum atom in 1 and 2 is chelated to a terminal oxygen and two bridging sulfurs to complete the octahedral configuration. Their catalytic activities in the reduction from C₂H₂ to C₂H₄ as well as other binuclear Mo? S? polycarboxylate complexes, a [Fe₄S₄] single cubane and a chainlike Mo? Fe? S compound were investigated and it was found that 1 exhibited relatively good catalytic activity. Copyright © 2007 John Wiley & Sons, Ltd.     

Influence of polycrystalline MoS2 nanoflowers on mouse breast cancer cell proliferation via molten salt sintering

In this paper, polycrystalline molybdenum disulfide (MoS₂) nanoflowers were prepared by mixing ammonium molybdate tetrahydrate [(NH₄)₆Mo₇O₂₄·4H₂O] and potassium thiocyanate (KSCN) at 300 °C for 2 h via molten salt sintering method. Under scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), MoS₂ showed popcorn-like shape, which surface distribution defects were easy to be further modified. MoS₂ as a nano-enzyme was used to inhibit the proliferation of mouse breast cancer cells (4 T1), which had 69.8 % inhibitory effect on 4 T1 cell proliferation. Electron spin resonance (ESR) analysis showed that MoS₂ could produce a large number of stable hydroxyl radicals (–OH). The disulfide bond in MoS₂ was highly sensitive to reactive oxygen species (ROS). High ROS level leads to the death of cancer cells under oxidative stress and inhibits the proliferation of 4 T1. This work demonstrates that MoS₂ is a potential anticancer drug or carrier for cancer treatment.     

An organic‐inorganic heterogeneous catalyst based on Keplerate polyoxometalates for oxidation of dibenzothiophene derivatives with Hydrogen peroxide

An organic‐inorganic material (NH₄)₂(MimAM)₄₀[Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] have been synthesized by reacting [(NH₄)₄₂[Mo^VI₇₂ Mo^V₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] with the ionic liquid 3‐Aminoethyl‐1‐methylimidazolium bromide. The catalyst showed remarkably a high catalytic performance in the oxidation of dibenzothiophene (DBT) derivatives with H₂O₂ 35% as a safe and green oxidant. The main parameters affecting the process including catalyst, acid additive, hydrogen peroxide amounts and temperature have been investigated in detail. Sulfur removal of DBT in n‐heptane reached to 98.3% yield at 40 °C using 2.5 mmol H₂O₂ and 100 mg of (NH₄)₂(MimAM)₄₀[Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] after 90 min. Under the optimal conditions, BT (benzothiophene), DBT (dibenzothiophene) and 4,6‐DMDBT (4,6‐dimethyl‐dibenzothiophene) achieved high desulfurization efficiency. Our results showed that the reactivity order of different model sulfur compounds are thiophene <4,6‐dimethyl dibenzothiophene< dibenzothiophene. The catalysts could be easily separated from the reaction solution by simple filtration and recycled for several times without loss of activity.     

Probing the Catalytically Active Species in POM-Catalysed DNA-Model Hydrolysis**

Phosphoester hydrolysis is an important chemical step in DNA repair. One archetypal molecular model of phosphoesters is para-nitrophenylphosphate (pNPP). It has been shown previously that the presence of molecular metal oxide [Mo₇O₂₄]⁶⁻ may catalyse the hydrolysis of pNPP through the partial decomposition of polyoxomolybdate framework resulting in a [(PO₄)₂Mo₅O₁₅]⁶⁻ product. Real-time monitoring of the catalytic system using electrospray ionisation mass spectrometry (ESI-MS) provided a glance into the species present in the reaction mixture and identification of potential catalytic candidates. Following up on the obtained spectrometric data, Density Functional Theory (DFT) calculations were carried out to characterise the hypothetical intermediate [Mo₅O₁₅(pNPP)₂(H₂O)₆]⁶⁻ that would be required to form under the hypothesised transformation. Surprisingly, our results point to the dimeric [Mo₂O₈]⁴⁻ anion resulting from the decomposition of [Mo₇O₂₄]⁶⁻ as the active catalytic species involved in the hydrolysis of pNPP rather than the originally assumed {Mo₅O₁₅} species. A similar study was carried out involving the same species but substituting Mo by W. The mechanism involving W species showed a higher barrier and less stable products in agreement with the non-catalytic effect found in experimental results.     

The molecular and electronic structure of the Mo12S24 macromolecule as a model of the active component of a hydrodesulfurization catalyst

The density functional theory (DFT) with the B3P86 hybrid exchange-correlation functional was used to calculate the molecular and electronic structure of the Mo₁₂S₂₄ macromolecule as a single MoS₂ layered structure slab. Calculations with geometry optimization are indicative of insignificant relaxation of the coordinatively unsaturated Mo and S atoms, which corresponds with the literature DFT data on the MoS₂ single slab obtained with periodic boundary conditions. The calculated forbidden band width (0.85–0.98 eV) is comparable with its experimental value (1.30 eV) and the results of DFT calculations of MoS₂ with periodic boundary conditions (0.89 eV). An analysis of the electronic state of the surface Mo centers in the Mo₁₂S₂₄ macromolecule showed that these centers were reduced to a greater degree than the Mo(IV) atoms in the bulk. The adsorption complex between the Mo₁₂S₂₄ macromolecule and six H₂S molecules was calculated to characterize the adsorption ability of the coordinatively unsaturated Mo centers. The structure and energy characteristics of the adsorption complex corresponded to weak donor-acceptor interaction between the π lone pair of H₂S and the surface (reduced) Mo centers. The suggestion was made that the active center of the catalytic cycle of thiophene hydrodesulfurization should induce the oxidative addition of H₂ followed by the occlusion of hydrogen into the MoS₂ matrix.     

A sensitive electrochemical aptasensor based on palladium nanoparticles decorated graphene–molybdenum disulfide flower-like nanocomposites and enzymatic signal amplification

In the present study, with the aggregated advantages of graphene and molybdenum disulfide (MoS₂), we prepared poly(diallyldimethylammonium chloride)–graphene/molybdenum disulfide (PDDA–G–MoS₂) nanocomposites with flower-like structure, large surface area and excellent conductivity. Furthermore, an advanced sandwich-type electrochemical assay for sensitive detection of thrombin (TB) was fabricated using palladium nanoparticles decorated PDDA–G–MoS₂ (PdNPs/PDDA–G–MoS₂) as nanocarriers, which were functionalized by hemin/G-quadruplex, glucose oxidase (GOD), and toluidine blue (Tb) as redox probes. The signal amplification strategy was achieved as follows: Firstly, the immobilized GOD could effectively catalyze the oxidation of glucose to gluconolactone, coupling with the reduction of the dissolved oxygen to H₂O₂. Then, both PdNPs and hemin/G-quadruplex acting as hydrogen peroxide (HRP)-mimicking enzyme could further catalyze the reduction of H₂O₂, resulting in significant electrochemical signal amplification. So the proposed aptasensor showed high sensitivity with a wide dynamic linear range of 0.0001 to 40 nM and a relatively low detection limit of 0.062 pM for TB determination. The strategy showed huge potential of application in protein detection and disease diagnosis.     

Preparation and Characterization of a New Ternary Chromium(III)–Molybdenum(VI) Oxide Cr2–2xMoxO3

A new mixed oxide was prepared by coprecipitation of Cr(NO₃)₃and (NH₄)₆Mo₇O₂₄from aqueous solution and subsequent calcination. The ternary oxide with the general stoichiometry Cr_2–2xMo_xO₃was characterized by X-ray diffraction (XRD), thermoanalysis (TA), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and Raman scattering. The new oxide showed the typical temperature-dependent electric conductivity known for semiconductors. The structure was refined with the Rietveld method from powder diffraction data. It is strongly related to the hexagonal chromiumsesquioxide structure. Preliminary catalytic experiments revealed a low combustion rate for methane but an increasing preference for C–C coupling reactions with higher Mo content.