Thiophene hydrodesulfurization activity of MoS2/Al2O3 catalysts prepared via exfoliation. The effect of cobalt

In contrast to the bulk MoS₂, the structure of the active phase of the catalyst prepared via exfoliation is shown to exhibit a number of distortions, which form a superstructure of the type of the charge density waves with a quasi-period of 30 ?. Due to such distortions, the ions of cobalt firmly chemisorb on the basal plane of MoS₂ occupying, along the perimeter of the MoS₂ clusters, the regions with a lower energy of the Mo-S interaction. A synergetic increase in the catalyst activity due to the introduction of cobalt was observed up to the atomic ratios of Co/(Co+Mo) = 0.33, which is possible for the nanoparticles of MoS₂ with a diameter 200 ?, only if cobalt adsorbs on the basal plane. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phase-controlled synthesis and characterization of nickel sulfides nanorods

Different one-dimensional nickel sulfides, NiS nanorods and Ni₉S₈ nanorods were synthesized in the presence (Route 1) and absence (Route 2) of gas CO₂. X-ray powder diffraction patterns, scanning electron microscopy and transmission electron microscopy images show that the product from Route 1 is NiS nanorods with a diameter of about 50-120 nm, while the product from Route 2 is Ni₉S₈ nanords about 70-200 nm in diameter. A molecular-template-like mechanism was proposed for the one-dimensional structures growth. The products were also investigated by Raman and photoluminescence (PL) spectroscopy.     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Measurement of the enthalpy of phase transition for iron chevrel phase sulphide in the temperature range from 300 to 500 K

Enthalpy increment H_T-H_289K measurements have been made on iron Chevrel phase sulphide Fe₂Mo₆S_7.8, in the temperature range 300 to 500 K by the drop method using a hightemperature Calvet-type twin calorimeter. The first-order phase transition of this sulphide from a triclinic (low-temperature phase) to a rhombohedral (high-temperature phase) occurred at 375 K, and the enthalpy was evaluated to be 6.0 kJ/mol. The heat capacities of iron Chevrel phase sulphide Fe₂Mo₆S_7.8 were also calculated before and after the phase transition.

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Zusammenfassung Nach der Tropfenmethode wurden mittels eines Hochtemperaturdoppelkalorimeters vom Typ Calvet im Temperaturbereich 300–500 K an Fe₂Mo₆S_7.8Messungen der Enthalpieinkremente H_T-H_298K durchgeführt. Die Phasenumwandlung erster Ordnung bei diesem Sulfid von der triklinen (Niedertemperaturphase) in die rhomboedrische (Hoch-temperaturphase) erfolgt bei 375 K und die Enthalpie erhielt man mit einem Wert von 6.0 kJ/mol. Die Wärmekapazitäten für Fe₂Mo₆S_7.8 wurden sowohl vor als auch nach der Phasenumwandlung berechnet.

     

Kinetic characterization of the reduction of silica supported cobalt catalysts

Abstact  The reduction process of silica supported cobalt catalyst was studied by thermal analysis technique. The reduction of the catalyst proceeds in two steps:

Molten salt synthesis (MSS) of Cu2Mo6S8—New way for large-scale production of Chevrel phases

The Chevrel phase (CP), Mo₆S₈, was found to be an excellent cathode material for rechargeable magnesium batteries. Mo₆S₈ is obtained by a leaching process of Cu₂Mo₆S₈, which removes the copper. A new method of Cu₂Mo₆S₈ production was developed. In contrast to the well-known solid-state synthesis of CP, the method is based on the reaction in a molten salt media (KCl). A fast kinetics of this reaction allows using less active, but more convenient precursors (sulfides instead of sulfur), decreasing temperature and synthesis duration, as well as operation in the inert atmosphere instead of dynamic evacuated systems. It was shown that the composition and the electrochemical behavior of the products obtained by MSS and by the solid-state synthesis are identical. Thus, the molten salt method is extremely attractive for the large-scale production of the active materials for Mg batteries.     

钼酸镍铵的环保合成及其对二苯并噻吩的加氢脱硫反应性能

日益苛刻的环保法规对柴油中的硫含量提出了更高的要求,而非负载型加氢脱硫催化剂具有较高的催化反应活性,其研发及应用不仅具有理论研究价值,同时还具有较高的社会经济性.非负载型加氢脱硫催化剂中的典型代表即为Nebula催化剂,该催化剂可以在不更改原有装置的前提下,使得原始设计生产硫含量为500 μg/g的装置得以生产硫含量不高于10 μg/g的超低硫柴油.已有的文献报道中,非负载型加氢脱硫催化剂前驱体主要是通过水热反应法及化学沉淀法制备而成.这两种方法以水为溶剂,溶剂水的量远远高于反应原料的添加量,因此,这两种方法不仅产生大量含有重金属离子的污水,同时能量及沉淀剂的消耗较高,最终导致产品的收率较低,原子经济性较差.为了更加环保、可持续地生产非负载型加氢脱硫催化剂前驱体,本文报道了一种以加水辅助研磨、固相反应法合成非负载型加氢脱硫催化剂前驱体钼酸镍铵((NH4)HNi2(OH)2(MoO4)2),并且揭示了其形成机理.相较于传统的水热反应法和化学沉淀法,我们提出的固相反应法使合成过程明显简化,主要步骤包括原料的物理混合、添加少量水进行研磨及加热.通过X射线衍射、红外光谱及拉曼光谱研究了钼酸镍铵的形成机理.结果表明,在钼酸镍铵的形成过程中,钼酸铵分子中的一个Mo原子被Ni原子取代形成了一种介稳态中间物种((NH4)4(NiH6Mo6O24)· 5H2O),而在120℃下处理不仅可以移除加入的少量水,而且促进了钼酸镍铵的形成.揭示钼酸镍铵的形成机理对于后续的研究具有重要的意义,因为可以更有针对性的调节、优化制备方法或者引入其它溶剂,从而制备具有某些特定性质的钼酸镍铵类物质.通过这种固相反应法制备的钼酸镍铵,具有与化学沉淀法制备的样品几乎相同的物理化学性质,包括物相、热稳定性能、孔结构性质等.不添加任何组分,将钼酸镍铵前驱体直接压片,并在固定床高压微型反应装置中进行原位硫化,制备了硫化态非负载型加氢脱硫催化剂.以二苯并噻吩为模型化合物,考察了通过化学沉淀法和固相反应法制备的两种钼酸镍铵前驱体的加氢脱硫反应活性.虽然这两种制备方法有所区别,但是硫化态非负载型加氢脱硫催化剂中活性组分二硫化钼(MoS2)纳米颗粒具有相似的堆积层数和片层长度,同时对二苯并噻吩的转化频率(TOF)相近,分别为28×10-4s(固相反应法)和26×10-4 s(化学沉淀法).因此,与传统的水热反应法或化学沉淀法相比,该法具有简化合成过程、降低水及能源的消耗及提高产品的收率等明显的优势.对于大规模地合成钼酸镍铵并用于工业加氢脱硫反应装置中具有重要的意义.与此同时,这种少量水辅助研磨固相反应法可以扩展到钼酸镍铵同晶物质的合成,例如钼酸钴(锌、铜)铵.     

Synthesis, characterization and activity of alumina-supported cobalt nitride for NO decomposition

A new type of transition metal nitride, viz. alumina-supported cobalt nitride, was synthesized for the first time by NH₃-temperature-programmed reaction, and its structure was characterized by BET, X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) techniques. The supported cobalt nitride performs much better than its bulk counterpart for NO decomposition, owing to its small crystal size, high thermal stability and big surface area.     

含磷、硫、氮配原子的钴羰基簇合衍生物的合成和表征

过渡金属原子簇化学是当今化学学科中非常活跃的研究领域之一 ,这类簇合物大多有着新颖的几何构型和多样化的成键方式 ,并且具有独特的催化性能[1 ] 。迄今为止 ,人们合成了多种含磷、硫、氮等原子的铁、钴、钌等羰基簇合衍生物 ,但其中三种以上原子同时配位的情况并不多见 ,有金振兴等的含Ｃ、Ｓ、Ｎ配原子的三核钴簇[2 ] ;Ｌｕｇａ和Ｃａｂｅｚａ的三钌簇[3 ,4] 以及Ｃｈｉｈａｒａ等合成的五核钌簇[5] ,其分子中都有Ｐ、Ｎ、Ｏ三原子配位。我们利用复杂的含Ｐ、Ｓ、Ｎ等可配原子的有机配前体与二元钴羰合物反应 ,合成了一系列三核、四核…     

Synthesis and neurotropic activity of silyl propargyl alcohols and sulfides

New silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols were synthesized using phase‐transfer catalytic and organometallic methods. These compounds were tested for acute toxicity and neurotropic activity in the pentylenetetrazole test, and for phenamine hypothermia, phenamine hyperactivity and passive avoidance response tests. We have found that the silyl propargyl alcohols and sulfides are low toxicity compounds, the LD₅₀ being 700–1300 mg kg^?1. In the PAR test, the synthesized compounds exerted some memory‐improving activity. For di‐1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)methyl(3‐iodopropyl)silane ( 16 ) the effect was statistically significant and amounted to 250% of the control level. In the pentylenetetrazole test, all compounds possessed anticonvulsant activity, the most active compounds being 3‐(benzoxazolylthio)‐1‐propynyl(trimethyl)silane ( 6 ) and di‐[2‐(1‐hydroxycyclohexyl)ethynyl]methyl(3‐iodopropyl)silane ( 17 ). The phenamine‐induced hyperactivity was significantly elevated after treatment with (3‐trimethylsilyl‐2‐propynyl)thiobenzene ( 1 ) or di‐[1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)diphenylsilane ( 12 ). Our data show that these silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols possess certain memory improving and anticonvulsant activity that should be studied in detail to evaluate the receptor systems involved. Copyright © 2004 John Wiley & Sons, Ltd.     

Catalytic activity of Mn(III) porphyrins supported onto graphene oxide nano-sheets for green oxidation of sulfides

Abstract

In this research, oxidation of various sulfides with urea hydrogen peroxide (UHP) in the presence of manganese porphyrin grafted onto graphene oxide ([Mn(THPP)OAc@GO]) in ethanol was studied. The heterogenized catalyst was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), and UV–Vis spectroscopy. The amount of Mn-porphyrin loaded on the GO nano-sheets was determined by atomic absorption spectroscopy (AAS) and the thermal stability of the heterogenized catalyst was investigated by thermo-gravimetric analysis (TGA). [Mn(THPP)OAc@GO] was applied for the green oxidation of different sulfides and the solid catalyst can be simply reused several times without losing its catalytic efficiency.     

Synthesis of diaryl sulfides through CH bond functionalization of arylamides with cobalt salt and elemental sulfur

A cobalt(II)-mediated, highly chemoselective thioarylation reaction of arylamides with elemental sulfur was reported. This reaction led to the formation of various symmetric diaryl sulfides in yields of up to 65% under mild reaction conditions. A cobalt-sulfur radical process was proposed based on preliminary results and mechanistic studies.     

Thermoelectric and structural properties of a new Chevrel phase: Ti0.3Mo5RuSe8

The new Chevrel phase Ti_0.3Mo₅RuSe₈ has been synthesized and characterized by quantitative microprobe analysis, powder X-ray diffraction, and high-temperature thermoelectric properties measurements. The thermoelectric properties of this compound are compared to the previously reported data for other related Chevrel phases. We report also the results of Rietveld analysis of powder X-ray diffraction data for Ti_0.3Mo₅RuSe₈. This compound adopts the rhombohedral Chevrel phase structure (space group , Z=3) with hexagonal lattice constants a=9.75430(25) Å and c=10.79064(40) Å. The low level of incorporation and low scattering power of Ti precluded the identification of the Ti positions, and Rietveld refinement was carried out only for the Mo₅RuSe₈ framework of Ti_0.3Mo₅RuSe₈ (R_p=10.5%, R_wp=14.6%). Rietveld analysis was also used to refine the structure of the unfilled phase Mo₅RuSe₈ (, Z=3, a=9.63994(8) Å, c=10.97191(11) Å, R_p=8.0%, R_wp=10.5%). Comparisons between the two structures are made.     

Correlation between electronic properties and hydrodesulfurization activity of 4d-transition-metal sulfides

The present study attempts to examine the relationship between electronic-structure properties exhibited by 4d-transition-metal sulfides (TMSs) in connection with the hydrodesulfurization (HDS) catalytic activity. The electronic structure is studied by means of a periodic density functional approach using a plane-wave basis set and appropriate pseudopotentials. Both bulk and relevant surfaces of NbS, NbS(2), MoS(2), TcS(2), RuS(2), Rh(2)S(3), PdS, and PdS(2) have been analyzed. High densities of nonbonding states below the Fermi level have been found for the TMSs that exhibit good catalytic performance. Therefore, it is suggested that the incomplete filling of the band gap at exposed transition metal atoms over the catalyst surface plays a determinant role in the HDS reactions. It has also been found that the highest HDS activity occurs when the surface-metal-site density of electronic states has a local minimum at the Fermi level that enhances the donation-back-donation mechanism. Additionally, the Sabatier principle is qualitatively rationalized in terms of the position of covalent bands below the Fermi level.     

The effect of milling on the performance of a Mo6S8 Chevrel phase as a cathode material for rechargeable Mg batteries

In the present study, we explored how milling Mo₆S₈ Chevrel phase in inert or air atmosphere affects their electrochemical behavior as a Mg-ion insertion material for rechargeable Mg batteries. Electrochemical tools such as slow scan rate cyclic voltammograms and potentiostatic intermittent titration technique have been used in conjunction with X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy. In contrast to the deterioration observed for milling Mo₆S₈ in air, its milling under Ar results in specific capacity increase due to improved Mg-ion diffusion kinetics. It was shown that in spite of the conservation of the bulk crystallographic structure, both for air and the Ar-milled materials, they differ significantly in the average particle sizes and the degree of surface oxidation state.Dedicated to Prof. G. Horanyi on the occasion of his 70th birthday     

An approach to preparing porous and hollow metal phosphides with higher hydrodesulfurization activity

This paper describes an effective method for the synthesis of metal phosphides. Bulk and supported Ni₂P, Cu₃P, and CoP were prepared by thermal treatment of metal and the amorphous red phosphorus mixtures. Porous and hollow Ni₂P particles were also synthesized successfully using this method. The structural properties of these products are investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP-AES) and X-ray photoemission spectroscopy (XPS). A rational mechanism was proposed for the selective formation of Ni₂P particles. In experimental conditions, the Ni₂P/SiO₂ catalyst exhibits excellent hydrodesulfurization (HDS) activity for dibenzothiophene (DBT).     

Synthesis and characterization of multiwall carbon nanotubes/alumina nanohybrid-supported cobalt catalyst in Fischer-Tropsch synthesis

Multiwall carbon nanotubes (MWNTs) and alumina are combined to give a new type of nanohybrid for Fisher-Tropsch synthesis (FTS) catalyst support. Alumina nano-particles (10 wt%) were introduced directly on functionalized MWNTs by a modified sol-gel method. Microstructure observations show that alumina particles were homogeneously dispersed on the inside and outside of modified MWNTs surfaces. 15 wt% cobalt loading catalysts were prepared with this nanohybrid and γ-alumina as a reference, using a sol-gel technique and wet impregnation method respectively. These catalysts were characterized by TEM, XRD, N₂-adsorption, H₂ chemisorption and TPR. The deposition of cobalt nanoparticles synthesized by sol-gel technique on the MWNTs nanohybrid shift the reduction peaks to a low temperature, indicating higher reducibility for uniform cobalt particles. Nanohybrid also aided in high dispersion of metal clusters and high stability and performance of catalyst. The proposed MWNTs nanohybrid-supported cobalt catalysts showed the improved FTS rate (g_HC/(g_cat·min)), CO conversion (%), and water gas shift rate (WGS)(g_CO2/(g_cat·h)) of 0.012, 52, and 30E-3, respectively, as compared to those of 0.007, 25, and 18E-3, respectively, on the γ-alumina-supported cobalt catalysts with the same Co loading.     

Chemical transformations of organic sulfides during hydrogenolysis in the presence of metal chloride complexes

Desulfurization of organic sulfides in hydrocarbon solvents in the presence of aqua complexes of metal chlorides H[MAlCl₄OH] that exhibit lower acidity as compared to AlCl₃ proceeds under mild conditions (450–525 K, atmospheric pressure) without external introduction of hydrogen. The process occurs with cleavage of C-S bonds and through intermediate formation of mercaptans to give H₂S and the corresponding hydrocarbons. The reaction is accompanied by cleavage of C-C bonds in the groups surrounding the organosulfur moiety, in thiacyclane rings, as well as in hydrocarbon solvent molecules, resulting in the formation of a wide spectrum of gaseous and liquid products.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1998–2002, October, 1995.     

Conductometric and DSC evidence for a high temperature phase transition in cobalt dibromide

A solid-state phase transition in cobalt dibromide at 647 K has been revealed by three different alternative current techniques. A small thermal effect of (181±18) J mol⁻¹ corresponding to the enthalpy of the transition has been determined by differential scanning calorimetry. The effect was observed on cooling and on heating as well.     

Photocatalytic activity of nanoparticles of metal sulfides in the degradation of organic dyes

The photocatalytic degradation of dyes at the nanosized sulfides of transition metals in aqueous solutions was investigated. The rate of degradation increases with decrease in the synthesis temperature of the nanoparticles and with the addition of alcohol. The substitution of Cd²⁺ cations by Ag⁺ or Cu²⁺ leads to a decrease in the photoactivity of the CdS, while substitution by In³⁺ leads to an increase. The substitution of Ni²⁺ and Co²⁺ cations in the corresponding sulfides by Cd²⁺ leads to an increase in the rate of degradation. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 276–280, September–October, 2006.