Preparation and Characterization of Carbon Nanotubes Supported Ni2P for Hydrodesulfurization (HDS) of Naphtha

Abstract

Ni₂P nanoparticles supported by functionalized carbon nanotubes (CNTs) were prepared for the first time. Nickel (II) dihydrogenphosphite as a source of nickel, with different loadings on the functionalized CNTs, were used. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. Surface areas of the samples were measured by using Brunauer, Emmett and Teller (BET) method. The catalytic activity of the prepared samples was studied in hydrodesulfurization (HDS) of naphtha. The results showed that the CNTs were

functionalized and Ni₂P particles were dispersed on the functionalized CNTs. It was also indicated that the pores size of Ni₂P particles were less than 20 nm. The catalytic study of the prepared samples confirmed that these compounds were stable and active in the process. Removal of sulfur from the desired naphtha in presence of the samples depended on the nickel loadings and increased with temperature in all cases.     

高效可回收催化剂In(OTf)_3用于无溶剂条件下Pechmann缩合反应(英文)

In(OTf)3 plays the role of a Lewis acid catalyst in the Pechmann condensation of phenols with β-ketoesters under solvent-free conditions to give coumarin derivatives. This novel and inexpensive method has advantages such as short reaction time, excellent product yields, and avoids the use of organic solvents in agreement with green chemistry principles. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding coumarins at 80 °C. The catalyst can be recovered after the reaction, and reused with only a slight decrease in the yield.     

Ultrasonic-assisted synthesis of magnetite/carbon nanocomposite for electrochemical supercapacitor

Iron oxides are considered as the promising pseudocapacitive materials for high-performance supercapacitors due to their high theoretical specific capacitance, low cost, environmental benignity, and natural abundance. In this work, we study capacitive behavior of different magnetite (Fe₃O₄) nanoparticles/carbon black (CB) composites ratios. These composites are synthesized by the coprecipitation method in the presence of ultrasonic waves. The structural and morphological characteristics of the magnetite/CB composites are investigated by X-ray diffraction and scanning electron microscopy, respectively. The electrochemical performance of magnetite/CB composite electrodes is tested by cyclic voltammetry and galvanostatic charge/discharge in a Na₂SO₄ electrolyte. The results indicate that the magnetite/CB electrodes show typical pseudo-capacitive behavior in Na₂SO₄ solution. Moreover, in comparison to the pure Fe₃O₄ (37 F g^?1) and carbon black (23 F g^?1), the as-prepared 45 % magnetite/CB nanocomposite electrode shows a higher specific capacitance (300 F g^?1). Additionally, the supercapacitor device of the magnetite/CB nanocomposite exhibits excellent long cycle life along with 98.5 % specific capacitance retained after 10,000 cycle tests.     

Reusable and robust high sensitive non-enzymatic glucose sensor based on Ni(OH)2 nanoparticles

Nickel hydroxide nanoparticles were successfully electrodeposited on graphite electrode (Gr/NiONP) and employed as a robust non-enzymatic glucose sensor. The results of cyclic voltammetry (CV) and chronoamperometry demonstrated that the Gr/NiONP electrode displayed high electrocatalytic activity toward glucose. The oxidation current is directly related to the glucose concentration from 1 μM to 15 mM. Besides, the glucose sensor displayed high sensitivity (2400 μA mM⁻¹ cm⁻²) with a detection limit of 0.53 μM (S/N = 3) in basic solution. Moreover, the sensor showed excellent selectivity, reproducibility and stability properties. The relative standard deviation is 1.2% for 10 successive measurements in 16 μM glucose. Interestingly, the signal for glucose was maintained at 95% of its initial value even after 6 months of storage under ambient conditions. Gr/NiONP electrode has also been tested to detect glucose in human serum with satisfactory results.     

Rapid determination of lead in water samples by dispersive liquid-liquid microextraction coupled with electrothermal atomic absorption spectrometry

The need for highly reliable methods for the determination of trace and ultratrace elements has been recognized in analytical chemistry and environmental science. A simple and powerful microextraction technique was used for the detection of the lead ultratrace amounts in water samples using the dispersive liquid-liquid microextraction (DLLME), followed by the electrothermal atomic absorption spectrometry (ET AAS). In this microextraction technique, a mixture of 0.50 mL acetone (disperser solvent), containing 35 microL carbon tetrachloride (extraction solvent) and 5 microL diethyldithiophosphoric acid (chelating agent), was rapidly injected by syringe into the 5.00 mL water sample, spiked with lead. In this process, the lead ions reacted with the chelating agent and were extracted into the fine droplets of CCl(4). After centrifugation (2 min at 5000 rpm), the fine CCl4 droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then, 20 microL from the sedimented phase, containing the enriched analyte, was determined by ET AAS. The next step was the optimization of various experimental conditions, affecting DLLME, such as the type and the volume of the extraction solvent, the type and the volume of the disperser solvent, the extraction time, the salt effect, pH and the chelating agent amount. Moreover, the effect of the interfering ions on the analytes recovery was also investigated. Under the optimum conditions, the enrichment factor of 150 was obtained from only a 5.00 mL water sample. The calibration graph was linear in the range of 0.05-1 microg L(-1) with the detection limit of 0.02 microg L(-1). The relative standard deviation (R.S.D.) for seven replicate measurements of 0.50 microg L(-1) of lead was 2.5%. The relative lead recoveries in mineral, tap, well and sea water samples at the spiking level of 0.20 and 0.40 microg L(-1) varied from 93.5 to 105.0. The characteristics of the proposed method were compared with the cloud point extraction (CPE), the liquid-liquid extraction, the solid phase extraction (SPE), the on-line solid phase extraction (SPE) and the co-precipitation, based on bibliographic data. The main DLLME advantages combined with ET AAS were simplicity of operation, rapidity, low cost, high-enrichment factor, good repeatability, low consumption of extraction solvent, requiring a low sample volume (5.00 mL).     

Resource allocation for performance improvement

In this paper the problem of allocating resources among Decision Making Units is considered. This study covers the case in which several homogeneous units are operating under the supervision of a central unit. The resource allocation is carried out by the DM (central unit) in such a way that the overall performance of the system is improved. Performance is defined by means of a convex combination of the ratio of the efficiencies before and after the resource allocation. It is assumed that each unit is allowed to modify its resources within the current production possibility set. A novel model is proposed which aims at achieving the best performance of the system. The method is capable of dealing with some additional constraints, imposed by the DM. The model is illustrated by a simple numerical example and a real application.     

Which nido:nido-macropolyhedral boranes are most stable?

A comparison of the relative stabilities computed at RB3LYP/6-311+G(d,p)//RB3LYP/6-31G(d)+ZPE of the neutral nido-single clusters and two vertex-sharing macropolyhedral nido:nido-clusters shows single-cluster nido-boranes with up to 11 vertexes to be energetically more favorable than isomeric macropolyhedral boranes. Extra hydrogen atoms at the open face have a significant influence on the relative stabilities of the single cluster nido-boranes vs nido:nido-macropolyhedral boranes. For anionic species, a clear-cut turning point for macropolyhedral preference is shifted to no less than 17 vertexes. Thermodynamically most stable neutral and anionic nido:nido-macropolyhedral boranes usually consist of a nido-10-vertex and a nido-11-vertex unit, respectively. The relative stabilities of isomeric neutral macropolyhedra reflect the patterns exhibited by the sum of thermodynamic stabilities of the individual clusters.     

Selection of diverse polymorphic structures from a small dynamic molecular network controlled by the environment

The complex interplay between systems and their environment plays an important role in processes ranging from self-assembly to evolution. Polymorphism, where, from the same ingredients different products can be formed, is likely to be an important enabler for evolutionary adaptation. Environmental pressures may induce polymorphic behaviour, where different pressures result in different structural organisation. Here we show that by combining covalent and non-covalent bond formation three distinct polymorphs can emerge from the same small dynamic molecular network: vesicular aggregates, self-replicating fibres and nanoribbons, depending on the nature of the solvent environment. Additionally, a particular set of conditions allows the transient co-existence of both vesicles and fibres.

The solvent environment dictates assembly morphology and molecular constitution allowing access to a remarkable variety of self-assembled structures.     

Single-Molecule Two-Color Coincidence Detection of Unlabeled alpha-Synuclein Aggregates

Protein misfolding and aggregation into oligomeric and fibrillar structures is a common feature of many neurogenerative disorders. Single-molecule techniques have enabled characterization of these lowly abundant, highly heterogeneous protein aggregates, previously inaccessible using ensemble averaging techniques. However, they usually rely on the use of recombinantly-expressed labeled protein, or on the addition of amyloid stains that are not protein-specific. To circumvent these challenges, we have made use of a high affinity antibody labeled with orthogonal fluorophores combined with fast-flow microfluidics and single-molecule confocal microscopy to specifically detect α-synuclein, the protein associated with Parkinson's disease. We used this approach to determine the number and size of α-synuclein aggregates down to picomolar concentrations in biologically relevant samples.     

Embedded palladium nanoparticles on metal–organic framework/covalently sulfonated magnetic SBA-15 mesoporous silica composite: As a highly proficient nanocatalyst for Suzuki–Miyaura coupling reaction in amino acid-based natural deep eutectic solvent

In this project, the main aim is the design and present a novel and unique heterogeneous nanocatalyst based on a metal–organic framework/covalently sulfonated magnetic SBA-15 mesoporous silica composite with the emphasis on promoting clean and green synthetic transformations and increasing the catalytic properties. In more detail, initially, SBA-15 containing magnetic nanoparticles was functionalized by a 1,3-propane sultone ligand. In the next step, the functionalized mesoporous substrate was used as a scaffold for the growth and synthesis of the zeolite imidazolate framework-8 (ZIF-8) crystals. The obtained composite was further applied as a suitable support for the immobilization of Pd nanoparticles via a post-modification procedure and the generation of heterogeneous catalysts. The prepared Fe₃O₄@SBA-15-SO₃H@ZIF-8@Pd was incorporated as a heterogeneous and green catalyst in the Suzuki coupling reaction in the natural deep eutectic solvent with efficient recyclability.