Transition Metal Salts Research Articles

A green and recyclable ligand-free copper (I) catalysis system for amination of halonitrobenzenes in aqueous ammonia solution

The amination of halonitrobenzenes is an important reaction to produce the corresponding nitroanilines. Direct amination of p-chloronitrobenzene (p-CNB) to p-nitroaniline (p-NAN) with aqueous NH3 solution was investigated over various transition metal salts in the absence of ligand, inorganic base and organic solvent. It was found that CuI is the most effective catalyst with respect to p-CNB conversion, p-NAN selectivity (≈ 100%) and the post-reaction separation and recycling. A high p-NAN yield of 97% could be obtained at 200 °C in 6.5 h with molar ratios of NH3/p-CNB and CuI/p-CNB of 21 and 0.1, respectively. A possible reaction mechanism was proposed, in which NH3 was not only a substrate but also a ligand to coordinate with CuI and formed a water-soluble Cu complex, and then it started the catalytic cycle. The influence of reaction variables such as NH3 concentration, CuI concentration, temperature and time on the p-CNB conversion and the p-NAN selectivity was examined. At room temperature the desired product of p-NAN is insoluble in water but the Cu complex catalyst is water-soluble and so the aqueous phase including the catalyst and NH3 can be easily separated and reused for the subsequent reaction runs. The green and sustainable system is effective for the conversion of diverse halonitrobenzenes to nitroanilines.

Titania - Supported transition metals sulfides as photocatalysts for hydrogen production from propan-2-ol and methanol

A series of transition metals sulfides deposited on anatase titania (MSx/TiO2) were prepared by precipitation of transition metals salts with thioacetamide in aqueous medium under reflux. The solids were characterized by XRD, XPS, temperature programmed reduction and transmission electron microscopy. The properties of as obtained catalysts were compared for the photocatalytic hydrogen evolution reaction (PHER) in pure methanol and water-isopropanol mixture. The sequences of PHER activity were compared with electrochemical HER and thiophene hydrodesulfurization (HDS) activity of the corresponding sulfides prepared by the same technique. For PHER, in both alcohols the most active photocatalysts contain hydrogenating sulfides of Co and Ru. However the PHER activity does not follow the same trend as electrocatalytic HER and thiophene HDS. Some sulfides, such as HgS or CuS, show poor activity in HDS and electrocatalytic HER, but have the PHER activity comparable with that of the best samples. This difference suggests that the PHER rate is not merely related to the hydrogen activating properties of the co-catalyst, but is enhanced by the transfer of photogenerated electrons from TiO2 towards the sulfide. The ranking of the co-catalysts and the PHER activity depend also on the nature of the alcohol molecule, the overall PHER rates in water-isopropanol mixture being lower than in methanol.

Desulfurization of Light Distillates by Oxidation and Rectification of Gas Condensate

The possibility that a process comprising the oxidation of sulfur compounds present in gas condensate and its subsequent rectification can be used to desulfurize light petroleum fractions has been explored. Oxidation of gas condensate with hydrogen peroxide in the presence of transition metal salts followed by its rectification makes it possible to decrease the sulfur content in the gasoline and diesel fractions by 95 and 75%, respectively in the fraction, with the sulfur content of -the residual fraction (350°C–FBP) remaining almost unchanged.

Transition Metal Salts Additive as Antioxidant or Metal Oxide Decorator during Electrochemical Exfoliation of Graphite?

The preparation of graphene via electrochemical exfoliation in aqueous solution is considered very attractive in terms of cost, scalability and non-toxicity. However, the quality of graphene produced by this method is inferior to the material produced by methods such as mechanical exfoliation due to the functionalisation of carbon by reactive oxygen radical species derived from water oxidation.1 There is a need to alleviate the effect of these radicals in order to capitalize on the use of anodic electrochemical exfoliation in aqueous solution. In this presentation, we will describe the use of a new approach, based on the unexpectedly versatile role of transition metal ions to produce high quality graphene via an anodic electrochemical exfoliation route, using sulfate as the intercalating anion.2 Notably, some of the transition metals (Co2+, Fe3+) acted as antioxidants, preventing surface oxidation of graphene, while others (Ru3+, Mn2+, Ir3+) acted as metal oxide decorators (Figure 1). The graphene obtained by electrochemical exfoliation of graphite in the presence of Co2+ is two orders of magnitude more conducting and defect free than the one obtained in the absence of cobalt ion. This Co-treated graphene found to be an excellent cathode material for Aluminum-based batteries in terms of performance and cycling stability. The use of other transition metal ions (Ru3+, Mn2+, Ir3+) in the electrolysis solution resulted in decoration of graphene with the oxide of that metal in a single stage simultaneous process. This process can also allow for producing graphene functionalised with hybrid metal oxides (G-RuO2-Mn3O4) in a one-pot single step process, which can be used as electrodes for supercapacitors (500 F g-1) and as an efficient electrocatalyst for water splitting. References 1) K. Parvez, Z. S. Wu, R. J. Li, X. J. Liu, R. Graf, X. L. Feng, K. Mullen, J. Am. Chem. Soc. 2014, 136, 6083. 2) A. Ejigu, K. Fujisawa, B. F. Spencer, B. Wang, M. Terrones, I. A. Kinloch, R. A. W. Dryfe, Adv. Funct. Mater. 2018, 28, 1804357. Figure 1

Role of Coprecipitation and Calcination of Precursors on Phase Homogeneity and Electrochemical Properties of Battery Active Materials

Coprecipitation is generally expected to produce particles with atomic level mixing between different cations, and thus has been extensively used to synthesize homogeneous and phase pure multi-component transition metal precursors that are converted to oxides for use as lithium-ion battery active materials. However, very few studies have attempted to quantitatively confirm the mixing level of ions by coprecipitation reactions, and neither have shown the superiority of local mixing for the homogeneity of final materials compared to alternative routes to producing battery active materials. In this talk, we will present experimental results from systematically comparing the phase purity and crystallinity of oxide powders that were either from a solution mixed multicomponent transition metal precursor via coprecipitation or from physically mixed single transition metal salts after calcination at the same conditions. A simple model was also applied to understand the diffusion limitations during the calcination process under various conditions. High voltage spinel LiMn1.5Ni0.5O4 was used as the target final oxide material composition and phase in this study, and electrochemical data will be provided to show the role that local mixing via coprecipitation plays in forming high crystallinity battery active materials with the desired phase.

Y-Type Zeolites Modified by Transition Metal Nanoparticles for Separating Argon from a Mixture with Oxygen

Based on NaY and HY granular synthetic zeolites without binding agents, adsorbents containing transition metal nanoparticles and characterized by the selectivity for argon at adsorption from a mixture with oxygen have been fabricated. Modification has been performed by the interaction with reverse micellar solutions of silver nanoparticles, as well as by ion exchange with transition metal salt solutions and subsequent reduction of metal ions until the achievement of nanoparticles in liquid media under the effect of ultrasound. The actual sizes of metal particles and their distribution over the surface of the modified samples of zeolites have been determined by the method of transmission electron microscopy (TEM). The samples’ equilibrium adsorption capacities for oxygen and argon at 25°С and atmospheric pressure and the partition coefficients of the argon–oxygen mixture as a ratio of the Henry coefficients have been determined. It has been demonstrated that samples of the NaY zeolite modified with silver nanoparticles have the highest selectivity for argon during its separation from a mixture with oxygen. The partition coefficient value of the argon–oxygen gas mixture was equal to 1.5–1.6.

Декарбоксилирование 2'-дикарбокси-5-(метил-5'индолил-3')-индолил-3-уксусной кислоты с использованием одновалентной меди

In this article a decarboxylation method based on the use of quinoline with a copper salt is discussed. Decarboxylation is the elimination of CO2 from the carboxylic group of carboxylic acids or the carboxylate group of their salts. The process is used to produce a large number of organic compounds, such classes as alkanes, alkenes, alcohols, ketones, ethers and esters. Decarboxylation plays an important role in the metabolism of living organisms, namely in the decarboxylation of amino acids. From this we can conclude that the process is important to study. Decarboxylation proceeds in different ways. The most common methods of decarboxylation includes heating in various conditions. For example, such as heating in the presence of acids and alkalis, under severe conditions with quinoline, thermal oxidation in the presence of transition metal salts, Kolbe reaction. In the procces of the CO2 removal group in relation to amino acids there are several types: α-decarboxylation, decarboxylation, associated with the trans-amination reaction and the condensation reaction of molecules. In the synthesis of substituted auxin 2'-dicarboxy-5-(methyl-5'indolyl-3')-indolyl-3-acetic acid, the yield of the product was not high. The usual heating in the presence of alkali output was less than 5%, and in this work it was decided to use other methods of decarboxylation to increase the yield of the product. The aim of the work is to improve the method of decarboxylation of carboxyindolyl substrates for increasing product yield and to compare with the result obtained by ordinary heating of this substances in the presence of alkali. At the end of the work summed up. Found the optimal conditions for the process of decarboxylation of investigated substrates. Optimal conditions chosen based on product yield. To confirm the chemical structures of the substances, 1H NMR, IR spectroscopy, and elemental analysis were used.

Fast precipitation-induced LiFe0.5Mn0.5PO4/C nanorods with a fine size and large exposure of the (010) faces for high-performance lithium-ion batteries

Olivine-type LiFexMn1-xPO4/C cathode materials are of great interest for lithium-ion batteries because of their higher lithium ion intercalation potential compared with that of LiFePO4. Two types of LiFe0.5Mn0.5PO4/C nanorods with different sizes and crystal structures were synthesized through a facile glycol-based solvothermal process with different precursor feeding sequences. The microstructural investigation revealed that the size and structure of the LiFe0.5Mn0.5PO4 nanorods can be tuned by nucleation and crystal growth rates of the intermediate precipitates, which can be controlled by precursor feeding sequence. The LiFe0.5Mn0.5PO4 nanorods obtained through the first feeding sequence (a solution of transition metal salts was added dropwise into the solution mixture of LiOH and H3PO4) exhibited less exposure of the (010) crystal faces and had bigger sizes compared with those of the LiFe0.5Mn0.5PO4 nanorods obtained through the second feeding sequence (a LiOH solution was added dropwise into the solution mixture of H3PO4 and transition metal salts). Electrochemical investigations indicated that the LiFe0.5Mn0.5PO4 nanorods obtained through the second feeding sequence showed substantially improved electrochemical performance, in which the discharge capacities reached 157 and 119 mAh g−1 at 0.2 and 5 C, respectively. Furthermore, a capacity retention of 89% was obtained after 500 cycles at 1 C, demonstrating excellent cyclic stability.

Effects of doping zinc oxide nanoparticles with transition metals (Ag, Cu, Mn) on photocatalytic degradation of Direct Blue 15 dye under UV and visible light irradiation.

Azo dyes represent the most commonly used group of dyes in the textile industry. These organic dyes are mainly resistant to biodegradation and may exhibit toxic and carcinogenic properties. The purpose of this study was to investigate the effects of doping zinc oxide (ZnO) nanoparticles (NPs) with transition metals (silver, manganese, and copper) on the photocatalytic efficiency of ZnO NPs in the removal of Direct Blue 15 dye from aqueous environments under ultraviolet (UV) radiation and visible light irradiation. One or two metals were used for doping the NPs. In total, seven types of undoped and transition metal-doped NPs were synthesized using the thermal solvent method with ZnO precursors and transition metal salts. The characteristics of the synthesized NPs were determined based on the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM), and zeta potential measurements. The produced ZnO NPs did not exhibit any particular photocatalytic activities under UV radiation and visible light irradiation. The highest removal efficiency under UV radiation was about 74% in the presence of silver-doped ZnO NPs, while the maximum efficiency under visible light was 70% in the presence of copper-doped ZnO NPs. The lowest removal efficiency was related to pure ZnO, which was 18.4% and 14.6% under UV and visible light irradiation, respectively. Although the efficiency of dye removal under visible light was not high compared to UV radiation, this efficiency was noteworthy in terms of both practical and economic aspects since it was achieved without the presence of ultraviolet radiation. The synthesis of transition metal-doped ZnO nanophotocatalysts (with one or two metals) under UV radiation or visible light irradiation could be used as an efficient and promising technology for the photocatalytic removal of Direct Blue 15 dye from aqueous environments.

Concentration polarization in membrane distillation: I. Development of a laser-based spectrophotometric method for in-situ characterization

Membrane-based processes have gained prominence for environmental and industrial separations, especially in water purification and desalination. In spite of these developments, a fundamental knowledge gap exists with regards to fully understanding the processes that occur at or near the membrane surface. Concentration polarization is a phenomenon that may have a significant impact on mass transfer and fouling of the membrane. While attempts have been made to experimentally characterize this phenomenon for pressure-driven filtration processes, most studies employ semi-empirical methods to estimate the extent of concentration polarization. This study presents a novel non-intrusive spectrophotometric method developed to measure the concentration profile of solute near the membrane surface in a direct contact membrane distillation system. A custom membrane cell was designed and fabricated for this study to allow accurate in-situ characterization of the concentration polarization layer with spatial resolution of 4.5 μm. The spectrophotometric method was developed and validated using transition metal salt (i.e., nickel chloride) in the feed solution to probe the concentration profile near the membrane surface. The method developed in this study can be extended to other membrane-based separation processes and other solutes with known absorption spectra.

A New Protocol for Efficient and High Yield Preparation of Nanocellulose from Elaeis guineensis Biomass: A Response Surface Methodology (RSM) Study

An innovative system for isolating nanocellulose was established that uses Ni(NO3)2 transition metal salt without the assistance of mechanical disintegrations or mineral acid and was compared with the classic production by tedious acid hydrolysis. Optimization study on Ni(II)-catalyzed hydrolysis of cellulose isolated from oil palm (Elaeis guineensis) empty fruit bunch (OPEFB) towards nanocellulose yield was investigated. Response surface methodology-central composite design was used to design and optimize the experiments with three operating parameters: pH of Ni(NO3)2 (pH 2–4), reaction time (20‒100 min) and reaction temperature (25‒65 °C). The present study indicated that the nanocellulose yield as high as 81.37% was achieved under hydrolysis conditions of pH 3, 58 °C within 58 min. At the optimum conditions, the OPEFB derived nanocellulose rendered high crystallinity of 91.1% and excellent thermal stability of 341 °C. Evidence of the successful isolation of nanocellulose was proven by HRTEM observation revealing fibrils formed the long and interconnected network-like structure with the average width of 41.1 ± 1.6 nm and several micrometers in length, which resulted in high aspect ratio. Thus, the obtained nanocellulose via Ni(II)-catalyzed hydrolysis has numerous potential applications and represent a green alternative for the treatment of OPEFB. This study provided a facile high yield procedure for the production of nanocellulose with similar characteristics to traditional nanocellulose, which was significant to the commercialization of nanocellulose.

Ammonia ligand and transition metal salt complexation on naturally dyed textile surface: A reflectance spectroscopic investigation to understand coloration and fastness properties

Ammonia is a stronger ligand and can replace water molecules in a chelate metal complex as per spectrochemical series. This property of ammonia was utilized in this work for the coloration of wool in order to obtain some unusual effects. Different concentrations of ammonia solution was applied on Butea monosperma flower extract dyed wool previously premordanted with ferrous sulfate salt to evaluate the effect on colorimetric properties. A range of newer shades were produced on wool substrates which were characterized in terms of K/S, CIELa*b* values and fastness properties. The observed effects exhibited on wool and acceptable fastness properties of produced shades points out a promising approach for developing environmentally sustainable colorful textile materials and clothing. The chemical modification of wool before and after application of ammonia was also evaluated using Fourier transform infrared spectrometer analysis. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

Synthesis, crystal structure and efficient SOD activity of transition compounds constructed with 5-aminoisophthalic acid ligand

Three new superoxide dismutase model compounds: [CoL(H2O)]·2H2O (1), [CdL(H2O)]·H2O (2) and [PbL] (3) were successfully synthesized by the reaction of a transition metal salt and 5-aminoisophthalic acid under hydrothermal conditions (L: 5-aminoisophthalic acid). The three compounds were characterized by elemental analysis, infrared spectroscopy, ultraviolet–visible spectroscopy, PXRD analysis and TG analysis. X-ray single crystal diffraction analysis showed that compounds 2 and 3 were 3D inorganic–organic framework structures while compound 1 was a 2D structure. These simulations contained pores structures with maximum sizes of 4.08–14.67 Å. To further explore the functional properties of these compounds, we firstly analyzed their SOD activity, and the results demonstrated that they have different SOD activities. The IC50 values of the three mimics are much smaller than the international standard for SOD standards, demonstrating that these mimics have superior Reactive Oxygen Species resistance.

Facile one-pot synthesis of novel N-benzimidazolyl-α-arylnitrones catalyzed by salts of transition metals

A novel series of N-benzimidazol-2-yl-α-aryl nitrones 3a–j is synthesized via simple one-pot condensation/oxidation of 2-aminobenzimidazole, an aromatic aldehyde and m-chloro perbenzoic acid (m-CPBA) as an effective oxidant using Mn(NO3)2·6H2O as an efficient catalyst at room temperature. All synthesized N-benzimidazolyl nitrones were identified using FTIR, NMR and mass spectroscopy. Also, stability energy theory calculations were performed and 1H NMR computational spectra were generated for the isomeric structures of 3a; the results show that the stability order is oxaziridine (4) followed by the nitrones 3aE and 3aZ. Also, comparing the computational spectroscopy results with the experimental data shows great accordance with nitrone 3aE. Among the remarkable points of this protocol, stable N-heterocyclic nitrones were prepared for the first time from raw materials under mild oxidative conditions. Therefore, they can easily be applied as high-potential intermediates for synthesizing valuable heterocycles in mild conditions. Due to benefits such as the use of inexpensive and available catalysts, short reaction times, high yields, facile workup to obtain pure product, and facile separation of the side product (m-chlorobenzoic acid), this simple protocol complies greatly with the principles of green chemistry.

Synthesis, thermal and surface activity of cationic single chain metal hybrid surfactants and their interaction with microbes and proteins.

A series of water-soluble metal functionalized surfactants have been prepared using commercially available surfactant cetyl pyridinium chloride and transition metal salts. These complexes were characterized in the solid state by elemental analysis, FTIR, 1H NMR and thermogravimetric analysis. The interfacial surface activity and aggregation behaviour of the metallosurfactants were analysed through conductivity, surface tension and small angle neutron scattering measurements. Our results show that the presence of metal ions as co-ions along with counter ions favours micellization at a low critical micellization concentration (CMC). Small angle neutron scattering revealed that the metallomicelles are of a prolate ellipsoidal shape and exhibit strong counterion binding. This article further describes the interaction of the metallosurfactants with transport protein Bovine Serum Albumin (BSA) using different spectroscopic techniques. A spectroscopic study was used to study the binding, interaction and quenching mechanism of BSA with the metallosurfactants. Gel electrophoresis (SDS-PAGE) and circular dichroism (CD) investigated the structural and conformational changes produced in BSA due to the metallosurfactants. The results indicate that there is an alteration in the secondary structure of BSA due to the electrostatic interaction between positive head groups and metal co-ions of the metallosurfactants and negatively charged amino acids of BSA. As the concentration increases, the α-helicity of BSA decreases and all the three studied metallosurfactants gave comparable results. Finally, the in vitro cytotoxicity and antimicrobial activity of the metallosurfactants were evaluated against erythrocytes and microorganisms, which showed prominent effects related to the presence of a metal ion in metallomicelles of the hybrid surfactants.

Energetic transition metal salts of 5,5′-dinitramino-3,3′-methylene-1H-1,2,4-bistriazole: syntheses, structures and properties

Five energetic transition metal salts based on H2DNAMT were synthesized. Meanwhile, H2DNAMT was oxidized to H2BNATO due to Fe3+ in [Fe(BNATO)(H2O)4]·2H2O. All of the metal salts exhibit comparable thermal stability and insensitivity.

Structural, morphological, optical and dielectric properties of M3+/PVA/PEG SPE Films (M = La, Y, Fe or Ir)

Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23owith increased intensity as PEG ratio increases. However, doping with La3+, Fe3+or Ir3+eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe3+or Ir3+. There are a consistency betweenEgvalues obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasingσacof films to higher values that candidates them in semiconductors industry.

Oxidation of cyclic ketones to dicarboxylic acids

Abstract This paper reports the results of studies concerning an alternative method of obtaining dicarboxylic acids, which consist of the oxidation of cyclic ketones with oxygen or air. The raw materials used were cyclopentanone, cycloheptanone, cyclooctanone, cyclododecanone, 1-tetralon, 2-methylhexanone, 3-methylcyclohexanone and 4-methylcyclohexanone. Oxidation reactions were conducted at 70-100°C, under pressure of 0.1 or 0.4 MPa, for 6 h, utilizing the salts of transition metals as catalyst and acetic acid as solvent. For example, when cyclopentanone was oxidized in the presence of Mn(II) salt, a conversion above 98% and selectivity to glutaric acid up to 68% were obtained. Among synthesized dicarboxylic acids, 1,12-dodecanoic acid was obtained with the highest selectivity of 76%.

Formation of Hydrocarbon Nanoscale Microemulsions Containing Group VI Metals and Catalytic Cracking of Final Systems

Regularities of the catalytic cracking of petroleum fractions in the presence of metal sulfides formed in situ from microemulsion of the “oil fraction–aqueous solution of transition metal salt” type are studied. The conditions of formation of microemulsions containing particles of the dispersed phase with a size less than 140 nm are found. The main features of thermolysis of these systems are ascertained, and the phase composition of the resulting materials is identified. The intensification of catalytic cracking by molybdenum and tungsten sulfides at expense of internal hydrogen resources is studied. This effect makes itself evident as an increase in the feedstock conversion by 6.0–7.6%; the yield of gas and the gasoline fraction increases by 2.1–2.5 and 5.6–6.1%, respectively.

Hydrothermal reaction of NaBiO<sub>3</sub>·<i>n</i>H<sub>2</sub>O with transition-metal (Co, Ni, Cu) salts

Hydrothermal reactions of a hydrated sodium bismuth oxide, NaBiO3·1.4H2O were performed with transition-metal salts MCl2, M(NO3)2 and MSO4 (M: Co, Ni, Cu). The common identified products from nitrate and chloride solutions were (Bi,M)2O2(OH)NO3 and (Bi,M)OCl, respectively and every product contained a small amount of unknown impurity phases. Various unknown phases also appeared in the products from the sulfate solutions, and no common crystalline phases were observed. During the course of these hydrothermal reactions, a new bismuth sulfate, BiOHSO4 was found by using a H2SO4 solution, and its crystal structure was clarified by using single-crystal X-ray diffraction data. No photocatalytic activity for the phenol degradation of BiOHSO4 was observed under ultraviolet and visible light irradiation.