Liquid Ammonia Reduction Research Articles

Synthesis, characterization and sintering of Si-C-N nano-powders via sodium reduction in liquid ammonia

Si-C-N nano-powders with tunable carbon content were synthesized through the reduction of silicon tetrachloride (SiCl4) and trichloromethylsilane (SiCl3CH3) solution by sodium in liquid ammonia. The nano-powders contain two domains of structure, Si-C-N amorphous or continuous random networks (CRNs), and free carbon. The carbon content in Si3+nCnN4 CRNs, is tunable from n=0 to n=1. Free carbon will appeared with the increase of the C/Si mole ratio when C/Si is higher than 1/4. The crystallization of amorphous Si-C-N powders occurs at temperatures ranging from 1300°C to 1500°C depending on the carbon content. The additive-free dense Si-C-N ceramics with relatively low porosity were fabricated by Spark Plasma Sintering (SPS).

Graphane Nanostripes.

Graphane, the hydrogenated counterpart of graphene, was shown to exhibit properties such as tunable band gaps through varied degrees of hydrogenation, fluorescence, or ferromagnetism. Graphane nanostripe properties have also been theoretically predicted. Herein, we show that graphane nanostripes can be prepared by opening carbon nanotubes using Birch reduction in liquid ammonia utilizing potassium as a reducing agent and water as a proton donor. The prepared graphane nanostripes exhibit several exceptional properties when coupled with trace metal dopants. The interplay of metallic nanoparticles and defects lead to a spin polarization and induction of ferromagnetic moment, as well as to enhanced electrocatalytic properties in the hydrogen evolution reaction when compared to non-hydrogenated carbon nanotubes.

Graphane Nanostripes

AbstractGraphane, the hydrogenated counterpart of graphene, was shown to exhibit properties such as tunable band gaps through varied degrees of hydrogenation, fluorescence, or ferromagnetism. Graphane nanostripe properties have also been theoretically predicted. Herein, we show that graphane nanostripes can be prepared by opening carbon nanotubes using Birch reduction in liquid ammonia utilizing potassium as a reducing agent and water as a proton donor. The prepared graphane nanostripes exhibit several exceptional properties when coupled with trace metal dopants. The interplay of metallic nanoparticles and defects lead to a spin polarization and induction of ferromagnetic moment, as well as to enhanced electrocatalytic properties in the hydrogen evolution reaction when compared to non‐hydrogenated carbon nanotubes.

Synthesis and sintering of silicon nitride nano-powders via sodium reduction in liquid ammonia

Nano-sized silicon nitride powders were synthesized through the reduction of silicon tetrachloride (SiCl4) by sodium in liquid ammonia at around −40°C.The product was in uniform particles of several nanometers, and in the amorphous form. The amorphous structure was stable up to 1200°C and turned to the crystal structure of α-Si3N4 at 1300°C, and then to β-Si3N4 structure when heated at temperatures higher than 1450°C.Via spark plasma sintering (SPS) dense bulks with 97.9% relative density of theoretic value and the grain size of 100–300nm was successfully fabricated at 1500°C without any sintering additives.

Approach to Monobactams and Nocardicins via Diastereoselective Kinugasa Reaction.

A Kinugasa reaction between copper(I) acetylides and cyclic nitrones derived from chiral amino alcohols and glyoxylic acid is reported. The stereochemical preferences observed in this reaction are discussed. The alkyne molecule approaches the nitrone exclusively anti to the large substituent next to the nitrogen atom to provide the cis-substituted β-lactam ring preferentially. The six-membered oxazinone ring can be opened by reduction with lithium borohydride. Deprotection of the β-lactam nitrogen atom can be achieved by lithium in liquid ammonia reduction or by CAN oxidation, depending on the substituents attached to the four-membered azetidinone ring. The adducts obtained by the Kinugasa reaction provide an attractive entry to a variety of monocyclic β-lactam structures related to monobactams and nocardicins.

Highly hydrogenated graphene via active hydrogen reduction of graphene oxide in the aqueous phase at room temperature

Hydrogenated graphene and graphane are in the forefront of graphene research. Hydrogenated graphene is expected to exhibit ferromagnetism, tunable band gap, fluorescence, and high thermal and low electrical conductivity. Currently available techniques for fabrication of highly hydrogenated graphene use either a liquid ammonia (-33 °C) reduction pathway using alkali metals or plasma low pressure or ultra high pressure hydrogenation. These methods are either technically challenging or pose inherent risks. Here we wish to demonstrate that highly hydrogenated graphene can be prepared at room temperature in the aqueous phase by reduction of graphene oxide by nascent hydrogen generated by dissolution of metal in acid. Nascent hydrogen is known to be a strong reducing agent. We studied the influence of metal involved in nascent hydrogen generation and characterized the samples in detail. The resulting reduced graphenes and hydrogenated graphenes were characterized in detail. The resulting hydrogenated graphene had the chemical formula C1.16H1O0.66. Such simple hydrogenation of graphene is of high importance for large scale safe synthesis of hydrogenated graphene.

Co3O4–carbon nanotube heterostructures with bead-on-string architecture for enhanced lithium storage performance

In this report, alkylcarboxyl group-decorated carbon nanotubes (CNTs) with clustered functionalization patterns are achieved based on a modified Birch reduction in liquid ammonia. By using these functional CNTs (f-CNTs), a new type of Co3O4-CNT heterostructure is prepared via a simple hydrothermal method. SEM and TEM analyses reveal that the as-synthesized Co3O4-CNT heterostructures exhibit bead-on-string architecture, in which the Co3O4 spheres are threaded with CNTs. A possible growth mechanism is proposed to explain the formation of these Co3O4-CNT heterostructures. The electrochemical properties of the Co3O4-CNT heterostructures as anode materials for lithium ion batteries are investigated. The Co3O4-CNT heterostructures display high electrochemical activity, good cycle stability and improved rate performance. Such a large improvement of the electrochemical performance can be related to the robust necklace-like architectures which possess properties such as high mechanical stability, excellent electric conductivity and good strain accommodation.

Molecular Imaging of Mesothelioma withT99mc-ECG andG68a-ECG

We have developed ethylenedicysteine-glucosamine (ECG) as an alternative to 18F-fluoro-2-deoxy-D-glucose (18F-FDG) for cancer imaging. ECG localizes in the nuclear components of cells via the hexosamine biosynthetic pathway. This study was to evaluate the feasibility of imaging mesothelioma with 99mTc-ECG and 68Ga-ECG. ECG was synthesized from thiazolidine-4-carboxylic acid and 1,3,4,6-tetra-O-acetyl-2-amino-D-glucopyranose, followed by reduction in sodium and liquid ammonia to yield ECG (52%). ECG was chelated with 99mTc/tin (II) and 68Ga/69Ga chloride for in vitro and in vivo studies in mesothelioma. The highest tumor uptake of 99mTc-ECG is 0.47 at 30 min post injection, and declined to 0.08 at 240 min post injection. Tumor uptake (%ID/g), tumor/lung, tumor/blood, and tumor/muscle count density ratios for 99mTc-ECG (30–240 min) were 0.47 ± 0.06 to 0.08 ± 0.01; 0.71 ± 0.07 to 0.85 ± 0.04; 0.47 ± 0.03 to 0.51 ± 0.01, and 3.49 ± 0.24 to 5.06 ± 0.25; for 68Ga-ECG (15–60 min) were 0.70 ± 0.06 to 0.92 ± 0.08; 0.64 ± 0.05 to 1.15 ± 0.08; 0.42 ± 0.03 to 0.67 ± 0.07, and 3.84 ± 0.52 to 7.00 ± 1.42; for 18F-FDG (30–180 min) were 1.86 ± 0.22 to 1.38 ± 0.35; 3.18 ± 0.44 to 2.92 ± 0.34, 4.19 ± 0.44 to 19.41 ± 2.05 and 5.75 ± 2.55 to 3.33 ± 0.65, respectively. Tumor could be clearly visualized with 99mTc-ECG and 68Ga-ECG in mesothelioma-bearing rats. 99mTc-ECG and 68Ga-ECG showed increased uptake in mesothelioma, suggesting they may be useful in diagnosing mesothelioma and also monitoring therapeutic response.

The Efficient and Enantiospecific Total Synthesis of Cyclopenta[b]phenanthrenes Structurally‐Related to Neurosteroids

We report an efficient synthesis of cyclopenta[b]phenanthrenes functionalized at C-3 and C-8 from an optically pure Hajos-Parrish ketone. The key step is a neutral alumina catalyzed Michael addition of a Hajos-Parrish ketone derivative (4) to 1,7-octadien-3-one (2) in 98% yield. This Michael addition product went through Krapcho decarbomethoxylation, aldol condensation, lithium liquid ammonia reduction, Wacker oxidation and acid catalyzed cyclization to form cyclopenta[b]phenanthrene (1a) in 37% overall yield for the 7 steps.

Synthesis and Sintering of Aluminium Nitride Nano-particles

AbstractAluminum nitride (AlN) nano-particles were synthesized from aluminum chloride by sodium reduction in liquid ammonia. A liquid solution of sodium dissolved in ammonia was employed as a reduction-nitridation agent, which enabled direct nitridation of aluminum chloride at −45°C. The synthesized particles were heat-treated at 1000°C in vacuum, and were characterized by X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area measurement. The results indicated that the product were hexagonal wurtzite AlN particles, with a specific surface area of 262 m2g−1. Spark plasma sintering (SPS) process was used to consolidate the as-prepared AlN nanoparticles, and a dense AlN ceramic (>98.5%) with average grain size of 200-400nm was obtained at 1600°C without the use of sintering additives.

A synthesis of 17-epi-calcidiol

The first synthetic approach to 17-epi-calcidiol 4 and congeners is presented. Key steps of the synthesis involve Pd-catalyzed reaction of the androst-16-ene derivative 6 with alkyl diazoacetates producing the respective cyclopropane derivatives 5, and lithium in liquid ammonia reduction of 5 leading to 17α-pregnane-20-carboxylic acid derivatives 9. The side chain was attached to ester 19 in a known manner.

Synthesis of nanoscale particles of Ta and Nb3Al by homogeneous reduction in liquid ammonia

The analysis of metallothermic reduction as an electronically mediated reaction predicted that the particle size of solid product could be reduced if the reaction were conducted in a medium that is a mixed conductor (ionic and electronic). This prediction was confirmed by reacting TaCl5 with sodium, each dissolved in liquid ammonia, to produce tantalum powder having an average particle size over an order of magnitude finer than the micron-sized powders produced commercially today. Metallothermic reduction in a mixed conducting medium has been extended to a multicomponent system in order to synthesize nanosized powder of Nb3Al by co-reduction of NbCl5 and AlCl3 both dissolved in liquid ammonia.

Energy and environmental analysis of an entire coke production plant using ECLIPSE

In the present work the sequential code ECLIPSE is used to perform an energy analysis of an entire industrial process—a coke production plant—aiming its characterization and optimization in terms of energy requirements and environmental impact. The code is validated by comparing its results against existing experimental data acquired at the above-referred plant, for the present operating conditions. Agreement is observed to be rather good, as the maximum relative errors between the ECLIPSE predictions and the actual values are 9.2, 9.7 and 8.7 per cent, respectively, for mass flows, temperatures and pressures. Moreover, those errors occur only once and at different streams, the vast majority of the relative errors for the remaining streams being below 1.0 per cent. In order to optimize the process both as far as energy and environmental aspects are concerned, alternative or new unit operations are suggested and are included in the production flow sheet or added to it and the entire new processes are simulated. More specifically, the better sealing of the coke ovens doors eliminating 80 per cent of the volatiles escape, the recovery of the lost sensible heat in the coke extinction operation and the restart of the 10 non-productive coke ovens would yield remarkable energy savings—losses would reduce from 46 440 to 9260 kW, apart from the environmental benefits emerging from the elimination of the volatiles escape to the atmosphere. In addition, for the coke gas cleansing sub-process, the substitution of the stripping process in the column distillation by a separation process, making recourse to a reverse osmosis installation, together with the operation setting of the ammonium destruction oven at a more convenient temperature, would allow both for energy savings of 66 per cent and a substantial reduction in both gaseous and liquid emissions, namely naphthalene, ammonia, nitric oxides and sulphur oxides. The improvements attained are noticeable and encouraging. Therefore, ECLIPSE proved to be an adequate tool for global industrial processes simulation, analysis and optimization, in spite of some limitations exhibited by the code in simulating detailed complex physical phenomena, such as combustion or coal distillation. Copyright © 2001 John Wiley & Sons, Ltd.

Introduction of monosaccharides having functional groups onto a carbosilane dendrimer: A broadly applicable one-pot reaction in liquid ammonia involving Birch reduction and subsequent S n2 reaction

Benzylthioalkyl glycosides of d-glucuronic acid, N-acetyl- d-glucosamine, and N-acetylneuraminic acid (common monosaccharide constituents of natural oligosaccharide chains) have been prepared as sulfide precursors for the carbohydrate coating of dendric carbosilane cores and used in a generally applicable one-pot reaction (Birch reduction in liquid ammonia and subsequent S n2 reaction) to generate a thioether linkage between the monosaccharide moieties and a carbosilane dendrimer. The dendrimers were uniformly functionalized with the monosaccharides in good yields.

Sulfurization of polymers

Polyethylene exhaustively sulfurized with elemental sulfur shows paramagnetic (spin concentration 2.7–9.7·1019 sp g−1,g=2.0041–2.0045, ΔH=0.53–0.62 mT) and redox properties, which was demonstrated by both voltammetric and chemical methods (sodium reduction in liquid ammonia). The high concentration of unpaired electrons, the character of the electrochemical activity, and the chemical properties are in agreement with the presence in the polymers of polyconjugated ladder polythiophene and parquet polynaphtho-thienothiophene structures along with polyene-polysulfide blocks. The use of the polymers under consideration as an active cathode material in lithium batteries enables their repeated cycling with a specific charge capacitance of 150–340 mA hg−1.

96/03772 Changes of macromolecular structure of coals in the processes of reduction and reductive alkylation in liquid ammonia

96/03772 Changes of macromolecular structure of coals in the processes of reduction and reductive alkylation in liquid ammonia

Stepwise synthesis of selenium coronands containing an odd number of selenium atoms: 1,5,9-triselenacyclododecane and 1,5,9,13,17-pentaselenacycloeicosane

The stepwise synthesis of two new selenium coronands containing an odd number of selenium atoms, starting from the fragments HO-(CH2)3-Cl, HO-(CH2)3-Br, HO-(CH2)3-SeCN, and NCSe-(CH2)3-SeCN, is described. The key diol containing one selenium atom, 4-selenaheptan-1,7-diol 4, was obtained in 97% yield from the reaction of 3-bromo-1-propanol 3 and the selonolate anion derived from 3-selenocyanato-1-propanol 2 by sodium metal reduction in liquid ammonia. The ditosylate 5, obtained from 4, was then treated with the bisselenolate anion derived from 1,3-bisselenocyanatopropane 6 to give the target selenium coronand, 1,5,9-triselenacyclododecane [12Se3] 7, in 96% yield. The ditosylate 5 was treated with two equivalents of the selenolate anion derived from 2 to give a second key acyclic diol 8 now containing three selenium atoms. The ditosylate 9, obtained from 8, was then treated with the bisselenolate anion derived from 6 to afford the second target coronand, 1,5,9,13,17-pentaselenacycloeicosane [20Se5] 11 in 44% yield. Keywords: selenium coronands, stepwise synthesis, macrocycles, heterocycles.

Alcaloides monoterpéniques III: Synthese stéréospésifique de la (±) épi-7,7a técomanine

The presence of a borane axial group in compound 14 induces a regio and stereospecific 1O 2 cycloaddition at low temperature. This selectivity together with that obtained during the lithium liquid ammonia reduction of the 4aβ-hydroxyenone 6, allows a short and stereospecific synthesis of the (±) epi-7,7a tecomanine 5, an unnatural and undescribed isomer of the tecomanine 1.

Potential dependence of the relative conductivity of poly(3-methylthiophene): electrochemical reduction in acetonitrile and liquid ammonia

Potential dependence of the relative conductivity of poly(3-methylthiophene): electrochemical reduction in acetonitrile and liquid ammonia

β-Elimination of an aminoborane by lithium-liquid ammonia reduction

The presence of an aminoborane group induces a fragmentation of the carbanionic intermediate 11 during the lithium liquid ammonia reduction of the unsaturated ketol 7a .