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The impact of solvent flexibility and electron correlation on the simulation results of Cu2+ in liquid ammonia has been investigated via an ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulation approach. To achieve this, three different simulation systems were considered in this study, namely Cu2+ in rigid and flexible ammonia at Hartree‐Fock (HF) level of theory, as well as resolution of identity second order Møller‐Plesset (MP2) perturbation theory in the rigid body case. In all cases, a stable octahedral [Cu(NH3)6]2+ complex subject to dynamic Jahn‐Teller distortions without the occurrence of ligand exchange was observed. The Cu2+ − NH3 distance in the first shell agrees well with the experimental and other theoretical data. In all three cases, the structural data shows that the rigid‐body ammonia model in conjunction with the HF level of theory provides accurate data for the first solvation shell, while at the same time, the computational demand and thus the achievable simulation time are much more beneficial. The vibrational analysis of the Cu2+ − NH3 interaction yields similar force constants in the three investigated systems indicating that there is no distinct difference on the dynamical properties of the first solvation shell. In addition to the QMCF MD simulations, a number of natural bond orbital (NBO) analyses were carried out, confirming the strong electrostatic character of the Cu2+ − NH3 interaction. [ABSTRACT FROM AUTHOR]

Crystals of the two new compounds (NHCtBuAu)3NHCl and [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 could be isolated from the reaction of Rb6Cs6Si17 with NHCtBuAuCl in the presence of [2.2.2]‐cryptand in liquid ammonia. Both compounds were characterized by single‐crystal X‐ray diffraction and crystallize trigonally without any alkali metals or chelating ligands. Additionally, the crystal of [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 was further interpreted by means of ELF and NBO calculations. In the case of (NHCtBuAu)3NHCl, NMR experiments provided an exceptional insight into the reaction processes in solution and allowed for the detection of sequential precursors. In the class of capped gold triangles (NHCtBuAu)3NHCl impresses with its unique characteristics of being capped by an imide and bound to N‐heterocyclic carbenes as ligands instead of the ubiquitously employed phosphines. The gold capped silicon tetrahedron [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 represents the first known silicide‐gold compound, as well as the first known functionalized Zintl anion, crystallized with a cationic central moiety. [ABSTRACT FROM AUTHOR]

By reaction of NaC2H with elemental selenium (grey or red) in liquid ammonia a crystalline brownish powder of NaSeC2H was obtained. The existence of the new –SeC2H anion – recently discovered in AISeC2H (AI = K, Rb, Cs) – was confirmed by IR spectra showing the expected C≡C, C–H, and C–Se vibrations. A synchrotron powder diffraction pattern (SNBL, ESRF/Grenoble) was indexed in a cubic unit cell with a = 7.044 Å. Analysis of the data led to a pyrite‐type structure (Pa3, Z = 4) with a static orientational disorder of the –SeC2H anions over two positions. No phase transition was observed upon cooling to 100 K, where essentially the same structure was obtained with a = 6.989 Å. Upon heating, NaSeC2H releases C2H2 as revealed by thermal analysis (DSC/TGA) resulting in potential Na2Se2C2 crystallizing in a small cubic unit cell with a ≈ 3.899 Å similar to findings on the decomposition of the other AISeC2H compounds. [ABSTRACT FROM AUTHOR]

There is a growing interest in using ammonia as a liquid carrier of hydrogen for energy applications. Currently, ammonia is produced industrially by the Haber‐Bosch process, which requires high temperature and high pressure. In contrast, bacteria have naturally evolved an enzyme known as nitrogenase, that is capable of producing ammonia and hydrogen at ambient temperature and pressure. Therefore, nitrogenases are attractive as a potentially more efficient means to produce ammonia via harnessing the unique properties of this enzyme. In recent years, exciting progress has been made in bioelectrocatalysis using nitrogenases to produce ammonia. Here, the prospects for developing biological ammonia production are outlined, key advances in bioelectrocatalysis by nitrogenases are highlighted, and possible solutions to the obstacles faced in realising this goal are discussed. [ABSTRACT FROM AUTHOR]

This paper reports on the effect of pH and temperature on size and polymorph stability of calcium carbonate (vaterite) formed without use of additives by Steamed ammonia liquid waste. The effect of the reaction temperature (20–80 °C), the initial Steamed ammonia liquid waste pH (1.5–12.1) and the stirring speed (800 and 1200 rpm/min) on the preparation of CaCO 3 with respect to the particle size and polymorph stability of final product were investigated. The obtained different CaCO 3 size and polymorphs were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and a Laser particle size analyzer (LPSA). The phase of vaterite transformed to calcite with increasing temperature 20 to 80 °C. The SEM and LPSA show that the CaCO 3 particle size increased from nano to several micron with the increase of temperature. When the initial CaCl 2 aqueous solution in low pH (1.5 and 2.6), nano-micro porous spherical vaterite can be obtained. When the initial CaCl 2 aqueous solution in high pH (11.7 and 12.1), preparation of CaCO 3 is mainly for the vaterite contains a small amount of calcite and the size particle increased. The possible mechanisms for the porous vaterite CaCO 3 formation have also been discussed. Since requirements for the physical properties of CaCO 3 particles are diverse for industrial and medical applications, it is important to understand CaCO 3 crystallization behavior for tailored particle synthesis. Unlabelled Image • High purity vaterite calcium carbonate was prepared without additives. • Preparation porous vaterite calcium carbonate. • Study the pH and temperature on calcium carbonate crystal and particle effect. • The mechanism of vaterite formation in porous spheres is described. [ABSTRACT FROM AUTHOR]

The compounds [M(NH3)8]I2 (M = Eu, Yb) were obtained from reactions in anhydrous liquid ammonia solutions as side products. They were characterized by single‐crystal X‐ray diffraction and found to be isotypic to the compounds [Ca(NH3)8]X2 (X = Cl, Br, I). The coordination sphere of the lanthanoid(II) cations is not square‐antiprismatic but much better described as bicapped trigonal‐prismatic. In contrast, quantum‐chemical gas‐phase calculations show the square‐antiprismatic coordination polyhedron (point group S8) to be energetically favored over the bicapped trigonal prism and the latter is not even a true local minimum. Obviously, hydrogen bonding and eventually other weak interactions have an impact on the observed bicapped trigonal‐prismatic coordination sphere of the [M(NH3)8]2+ cations in the solid state. [ABSTRACT FROM AUTHOR]

The pyrophoric compound Rb2[U(NH2)6] was obtained as a grey to black powder from the reaction of more than three equivalents of RbNH2 with UI3 in anhydrous liquid ammonia. During the process, UIII is oxidized to UIV and ammonia is reduced under evolution of H2. Rb2[U(NH2)6] crystallizes in the cubic crystal system, space group Fm3m, with the lattice parameter a = 9.7870(12) Å, V = 937.4(2) Å3, Z = 4 at T = 293 K. It is isotypic to K2PtCl6. The compound contains the unprecedented hexaamidouranate(IV) anion [U(NH2)6]2–. [ABSTRACT FROM AUTHOR]

The performance of experimental batch-reactor loaded with slaughterhouse waste at mesophilic temperature was investigated as well as the inhibition of both ammonia and sulfide concentration in the aqueous phase. The digester was operated for 68 days by evaluating the process stability basing on controlling parameters such as pH, volatile fatty acids and alkalinity in relation to the methane produced. The maximum CH4 content of 69.6% was achieved at 0.37 VFA/Alkalinity ratio and pH of 7.51 during day 37 of anaerobic digestion. However, a sudden increase of ammonia nitrogen in the digester from day 44 to day 68 decreased the methane content about 62.15% from 65% to 24.6%. Similarly, as the amount of sulfide content decreased in the liquid phase, gaseous H2S was elevated up to 132 ppm in the 68th day. During this time, it was observed that the ratio of VFA/Alkalinity decreased to 0.16, with a very low concentration of VFA, which was 150.92 mg/L. This phenomenon indicated that all the acids produced were consumed by methanogens and ammonia inhibition was at the highest rate due to the increase of ammonia nitrogen concentration in the last days of digestion. Furthermore, among of peculiar characteristic shown by slaughterhouse waste is the ability to maintain the pH above 7 without the addition of any buffering agent throughout the AD process. Meanwhile, the evaluation of the level of both ammonia and sulfide in the aqueous phase revealed that the inhibitory effect of ammonia concentration was higher than sulfide concentration. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Increased interest in liquid ammonia (NH3) for hydrogen storage can be attributed to its lack of carbon, high energy density to volume and mass ratios (17.6 wt% hydrogen), a ubiquitous supply and distribution network, and lower cost. Recent progress in direct ammonia fuel cells for power generation, as well as ongoing work on the electrochemical synthesis of ammonia, motivate the need for fundamental investigations of aqueous ammonia interactions with electrode materials. Porous gas-diffusion media (GDM) play a large role in facilitating liquid, gas, and charge transport and are an inherent part of these technologies membrane electrode assemblies (MEA). This work characterizes how key wetting properties such as contact angle, advancing/receding contact angles, adhesion force, and breakthrough pressure are influenced by GDM wet-proofing, thickness, and structure. These properties are studied for aqueous ammonia solutions with 0, 10, 20, and 30 wt% NH3. The higher concentrations of NH3 along an electrode surface can lead to lower contact angles as surface tension is reduced. Wet-proofing with PTFE loadings up to 10 wt% increases hydrophobicity, while higher loadings have diminishing effects. The results are useful to those involved with modeling, design, construction, and optimization of these systems. [ABSTRACT FROM AUTHOR]

Experimental studies of the electronic structure of excess electrons in liquids—archetypal quantum solutes—have been largely restricted to very dilute electron concentrations. We overcame this limitation by applying soft x-ray photoelectron spectroscopy to characterize excess electrons originating from steadily increasing amounts of alkali metals dissolved in refrigerated liquid ammonia microjets. As concentration rises, a narrow peak at ~2 electron volts, corresponding to vertical photodetachment of localized solvated electrons and dielectrons, transforms continuously into a band with a sharp Fermi edge accompanied by a plasmon peak, characteristic of delocalized metallic electrons. Through our experimental approach combined with ab initio calculations of localized electrons and dielectrons, we obtain a clear picture of the energetics and density of states of the ammoniated electrons over the gradual transition from dilute blue electrolytes to concentrated bronze metallic solutions. [ABSTRACT FROM AUTHOR]

Solutions of gallium trihalides GaX3 (X=F, Cl, Br, I) and their ammoniates in liquid ammonia were studied at ambient temperature under autogenous pressure by multinuclear (71Ga, 35Cl, 81Br) NMR spectroscopy. To unravel the role of pH, the analyses were done both in absence and in presence of ammonium halides, which are employed as mineralizers during ammonoacidic gallium nitride crystal growth. While gallium trifluoride and its ammoniate were found to be too sparingly soluble to give rise to a NMR signal, the spectra of solutions of the heavier halides reveal the presence of a single gallium‐containing species in all cases. DFT calculations and molecular dynamics simulations suggest the identification of this species as consisting of a [Ga(NH3)6]3+ cation and up to six surrounding halide anions, resulting in an overall trend towards negative complex charge. Quantitative 71Ga NMR studies on saturated solutions of GaCl3 containing various amounts of additional NH4Cl revealed a near linear increase of GaCl3 solubility with mineralizer concentration of about 0.023 mol GaCl3 per mol NH4Cl at room temperature. These findings reflect the importance of Coulombic shielding for the inhibition of oligomerization and precipitation processes and help to rationalize both the low solubility of gallium halides in neutral ammonia solution and, in turn, the proliferating effect of the mineralizer during ammonoacidic gallium nitride formation. [ABSTRACT FROM AUTHOR]

1,4-dihydropyridines, namely diethyl 4-(4-fluorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (1a), diethyl 2,6-dimethyl-4-(3,4,5-trimethoxyphenyl)-1,4-dihydropyridine-3,5-dicarboxylate(1b), and diethyl 4-(3,4-dimethoxyphenyl)-2,6-dihydroxy-2,6-bis(trifluoromethyl)piperidine-3,5-dicarboxylate (2), are synthesized by one-pot multicomponent condensation of aromatic aldehyde with ethyl acetoacetate and liquid ammonia in the presence of an ethanol-water mixture and are characterized by single crystal X-ray diffraction. The effect of a fluorine atom on the dihydropyridine nucleus give insight into the self-assembly of compounds with various types of non-covalent interactions that greatly affect the crystal packing. [ABSTRACT FROM AUTHOR]

The discovery of low-valent Zn compounds resulted in the renaissance of organometallic Zn complexes. Polyhedral clusters of tetrel elements can interact with Zn atoms either as Lewis donors or by incorporation of the Zn atoms as additional cluster vertices. Herein we report the reactions of ZnR2 (R = ethyl (Et), pentamethylcyclopentadiene (Cp*), phenyl (Ph) and 1,3,5-trimethylbenzene (Mes)) with Zintl ions of the types [E4]4− (E = Ge, Sn) and [Ge9]4− in liquid ammonia. Besides the desired Zintl ion complexes, intermediates were isolated that give insight into the reaction of organo Zn compounds in liquid ammonia. Three ions, [(η3:η3-Ge4)(ZnEt)2]2− (1a), [(η2-Sn4)Zn(η2-Sn4)]6− (2a) and [(η4-Ge9)(ZnEt)]3− (3a), were obtained and characterized by means of single crystal X-ray diffraction analysis. Furthermore, amides [(ZnPh2)2(μ2-NH2)2]2− (4a) and {[Zn(μ2-NH2)4][(ZnEt)2(μ2-NH2)2]2}2− (5a) were formed during the reactions, together with the addition products [ZnPh3]− (6a) and [ZnMes3]− (7a) and an anion [Cp*]− (8a), suggesting the following reaction sequence: in liquid ammonia the Zintl anions form amides, which then serve as ligands for ZnR2 molecules. The NH2− ligands weaken the corresponding Zn–R bonds, and thus bond cleavage and the addition of the Zintl anion to the Zn ion can take place, additionally promoted by the trapping of the leaving group R− by unreacted Zn organyls with the formation of [ZnR3]−. [ABSTRACT FROM AUTHOR]

Most existing thermal conductivity data for ammonia were obtained before 1988. Data obtained before 1988 may be affected by convection. The potential for these effects needs to be examined by the transient hot-wire method with high-speed sampling. In this study, the thermal conductivity of liquid ammonia was measured by the transient short-hot-wire method and compared with values from REFPROP 10.0. The transient short-hot-wire method was used to measure thermal conductivity at 284–354 K and 2–10 MPa. Compared with the calculated values from REFPROP 10.0, the average absolute deviation was 5.6 % and all the measured values were lower than those from REFPROP 10.0. [ABSTRACT FROM AUTHOR]

Cyclopropenone 1,3-propanediol ketal is an increasingly versatile building block for the introduction of various C3 and dioxaspiro units due to the emergence of numerous methodologies for the application of strained hydrocarbons. This Practical Synthetic Procedure gives an updated synthesis for a basic ketal of cyclopropenone with lowered solvent toxicity and a detailed step-by-step guide for the safe production of potassium amide in liquid ammonia and for its application in the synthesis of the cyclopropene ring. [ABSTRACT FROM AUTHOR]

A versatile, temperature controlled apparatus is presented, which generates deeply cooled liquid microjets of condensed gases, expelling them via a small aperture into vacuum for use in photoelectron spectroscopy (PES). The functionality of the design is demonstrated by temperature- and concentration-dependent PES measurements of liquid ammonia and solutions of KI and NH4I in liquid ammonia. The experimental setup is not limited to the usage of liquid ammonia solutions solely. [ABSTRACT FROM AUTHOR]

Liquid ammonia yield is the main index characterizing the process output of ammonia synthesis, the prediction of which is crucial for process control and optimization. However, the industrial process of ammonia synthesis involves multiple variables and strong nonlinearity, making it difficult to be accurately predicted using conventional mechanism‐driven model, or a certain type of data‐driven model. Therefore, a deep learning‐based heterogeneous pruning ensemble (DL‐HPE) model is proposed to overcome the limitations of conventional models. In this model, a "VDiv" pruning strategy that trades off diversity and accuracy is proposed and successfully applied to select the optimal subset from nine representative base models. Finally, the deep learning is employed to integrate the outputs of the involving models to generate the final prediction. The DL‐HPE method was applied to modeling the UCI standard dataset and the historical dataset collected from an ammonia plant in China. The results show that the method is superior to single model or other ensemble models both in accuracy and in robustness. [ABSTRACT FROM AUTHOR]

We report the synthesis of the doubly deprotonated calcium guanidinate, CaC(NH)3, from liquid ammonia and its crystal structure as determined from powder X‐ray and neutron diffraction, and confirmed using CNH elemental analysis and infrared (IR) spectroscopy data. CaC(NH)3 crystallizes in the hexagonal system with space group P63/m (no. 176) with Z = 2 and a = 5.2666(13) Å, c = 6.5881(6) Å and V = 158.25(4) Å3. We also compare the structural similarities and differences of this phase with the isotypical strontium and ytterbium compounds. [ABSTRACT FROM AUTHOR]

In‐depth investigations of the long‐time known Zintl phase NaTl revealed a phase transition of tetragonal NaTl‐tI8 [I41/amd; a = 5.2268(9) Å, c = 7.539(1) Å, V = 205.97(9) Å3] to Zintl's cubic NaTl‐cF16 [Fd3m; a = 7.4697(6) Å, V = 416.79(5) Å3] between 351 and 355 K. This phase transformation was observed for NaTl prepared by two different synthetic routes including Zintl's original procedure. An excess of sodium applied during the synthesis in liquid ammonia also resulted in the formation of NaTl‐tI8. DSC measurements suggest a first order phase transition. In addition to in‐situ temperature dependent powder X‐ray diffraction experiments, DSC measurements and solid‐state NMR investigations, we also performed theoretical DOS and band structure calculations for the cubic and tetragonal phase, respectively. The results suggest Na‐Tl interactions in the second coordination sphere being responsible for the observed tetragonal distortion of Zintl's cubic NaTl. [ABSTRACT FROM AUTHOR]

We report the synthesis of the doubly deprotonated calcium guanidinate, CaC(NH)3, from liquid ammonia and its crystal structure as determined from powder X‐ray and neutron diffraction, and confirmed using CNH elemental analysis and infrared (IR) spectroscopy data. CaC(NH)3 crystallizes in the hexagonal system with space group P63/m (no. 176) with Z = 2 and a = 5.2666(13) Å, c = 6.5881(6) Å and V = 158.25(4) Å3. We also compare the structural similarities and differences of this phase with the isotypical strontium and ytterbium compounds. [ABSTRACT FROM AUTHOR]

Nanocrystalline SnO2 powder has been successfully synthesized by using tin(II) chloride dihydrate (SnCl 2 ⋅ 2 H2O), distilled water and liquid ammonia by the simple chemical co-precipitation method at room temperature using different SnCl 2 ⋅ 2 H2O molar concentration of 0.3 M, 0.4 M and 0.5 M. The structural properties of the prepared SnO2 and transition metal doped SnO2 nanoparticles has been studied using X-ray diffraction method and scanning electron microscope. The composition of the powders has been analyzed using energy dispersive X-ray analysis. The XRD pattern of the SnO2 nanoparticles indicates the formation of single-phase rutile tetragonal structure. The grain size is found to be in the range of 3–7 nm and is found to increase with increasing SnCl2 molar concentration. The absorption spectra revealed that the bandgap decreased from 3.74 eV to 3.59 eV with increasing SnCl2 molar concentration. The photoluminescence spectra of SnO2 nanoparticles showed a visible broad luminescence band in the region of 385–430 nm. The magnetic studies have been carried out using the hysteresis loop obtained from a vibrating sample magnetometer. The SnO2 samples using 0.3 and 0.4 SnCl2 molar concentration exhibited ferromagnetic behavior whereas the SnO2 sample prepared using 0.5 M SnCl 2 ⋅ 2 H2O exhibited paramagnetic nature. [ABSTRACT FROM AUTHOR]

The reaction of uranium tetrabromide with potassium cyanide in anhydrous liquid ammonia at room temperature leads to the formation of brown crystals of [U2(CN)3(NH3)14]5+ [KBr6]5− · NH3. We determined the crystal structure of the compound by single crystal X-ray diffraction. To the best of our knowledge it contains the unprecedented spatially separated [KBr6]5− anion and presents the first uranium(IV) cyanide compound which forms a layer structure. The compound crystallizes in the trigonal space group P3̅m1 (No. 164) with a = 10.3246(13), c = 8.4255(17) Å, V = 777.8(3) Å3, Z = 1 at T = 100 K and is well described with the Niggli formula [ U (CN) 3 2 (NH 3) 7 1 ] ∞ 2 2 [ KBr 6 1 ]. $\mathop {} \limits_{\infty}^{2}{\left[ {{\rm{U}}{{({\rm{CN}})}_{{3 \over 2}}}{{({\rm{N}}{{\rm{H}}_3})}_{{7 \over 1}}}} \right]_2}\left[ {{\rm{KB}}{{\rm{r}}_{{6 \over 1}}}} \right].$ [ABSTRACT FROM AUTHOR]

The reaction of uranium tetrabromide with potassium cyanide in anhydrous liquid ammonia at room temperature leads to the formation of brown crystals of [U2(CN)3(NH3)14]5+ [KBr6]5− · NH3. We determined the crystal structure of the compound by single crystal X-ray diffraction. To the best of our knowledge it contains the unprecedented spatially separated [KBr6]5− anion and presents the first uranium(IV) cyanide compound which forms a layer structure. The compound crystallizes in the trigonal space group P3̅m1 (No. 164) with a = 10.3246(13), c = 8.4255(17) Å, V = 777.8(3) Å3, Z = 1 at T = 100 K and is well described with the Niggli formula [ U (CN) 3 2 (NH 3) 7 1 ] ∞ 2 2 [ KBr 6 1 ]. $\mathop {} \limits_{\infty}^{2}{\left[ {{\rm{U}}{{({\rm{CN}})}_{{3 \over 2}}}{{({\rm{N}}{{\rm{H}}_3})}_{{7 \over 1}}}} \right]_2}\left[ {{\rm{KB}}{{\rm{r}}_{{6 \over 1}}}} \right].$ [ABSTRACT FROM AUTHOR]

Here, we report a novel ammonia : ammonium salt solvent based pretreatment process that can rapidly dissolve crystalline cellulose into solution and eventually produce highly amorphous cellulose under near-ambient conditions. Pre-activating the cellulose I allomorph to its ammonia–cellulose swollen complex (or cellulose III allomorph) at ambient temperatures facilitated rapid dissolution of the pre-activated cellulose in the ammonia-salt solvent (i.e., ammonium thiocyanate salt dissolved in liquid ammonia) at ambient pressures. For the first time in reported literature, we used time-resolved in situ neutron scattering methods to characterize the cellulose polymorphs structural modification and understand the mechanism of crystalline cellulose dissolution into a 'molecular' solution in real-time using ammonia-salt solvents. We also used molecular dynamics simulations to provide insight into solvent interactions that non-covalently disrupted the cellulose hydrogen-bonding network and understand how such solvents are able to rapidly and fully dissolve pre-activated cellulose III. Importantly, the regenerated amorphous cellulose recovered after pretreatment was shown to require nearly ∼50-fold lesser cellulolytic enzyme usage compared to native crystalline cellulose I allomorph for achieving near-complete hydrolytic conversion into soluble sugars. Lastly, we provide proof-of-concept results to further showcase how such ammonia-salt solvents can pretreat and fractionate lignocellulosic biomass like corn stover under ambient processing conditions, while selectively co-extracting ∼80–85% of total lignin, to produce a highly digestible polysaccharide-enriched feedstock for biorefinery applications. Unlike conventional ammonia-based pretreatment processes (e.g., Ammonia Fiber Expansion or Extractive Ammonia pretreatments), the proposed ammonia-salt process can operate at near-ambient conditions to greatly reduce the pressure/temperature severity necessary for conducting effective ammonia-based pretreatments on lignocellulose. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The method of chromatography–mass spectrometry is used to study the impurity composition in monosilane obtained in the reaction of magnesium silicide with ammonium chloride in liquid ammonia. To improve the reliability of the impurity identification, along with the study of pure monosilane samples, we analyzed monosilane fractions isolated upon purification by low temperature rectification. To separate the impurities of permanent gases, hydrocarbons C1–C3, volatile inorganic hydrides, disilane, and alkylsilanes, we used an adsorption capillary column GS-GasPro 60 m × 0.32 mm with a modified silica gel. To separate the homologs of monosilane, siloxanes, and alkylsilanes, we used a column 25 m × 0.26 mm, df = 0.25 μm with a polytrimethylsilylpropyne (PTMSP) sorbent. The impurities were identified by comparison of their experimental mass spectra with the NIST database. In the absence of the mass spectra of analytes in the NIST electronic database or in the case of their low coincidence with the database spectra, the identification was performed using mass spectra and retention times published in the literature. The impurities of permanent gases, carbon dioxide, hydrocarbons C1–C3, volatile inorganic hydrides, monosilane homologies, siloxanes, and alkyl silanes were identified in monosilane. Quantitative determination of the impurities was carried out in the mode of selective ion detection using the mass numbers for which the signal-to-noise ratio was maximal. Their concentrations were calculated using a method of absolute calibration by the peak areas; in the case where reference samples were absent, the concentrations were determined using the dependence of the sensitivity coefficients of their detection on the magnitude of the total ionization cross sections. The detection limits of the impurities range within 1 × 10–5–2 × 10–7 mol %. The accuracy of the analysis was verified by the method of sample size variation. The results of determination of the impurities in monosilane after synthesis, as well as in monosilane purified by low temperature rectification and in the isolated fractions with concentrated higher and lower boiling impurities, are reported. [ABSTRACT FROM AUTHOR]

A quantitative structure–retention relationship study was performed by thin layer chromatography on a number of β‐blockers using 315 molecular descriptors of which nine were selected to be having the most important physicochemical properties. These descriptors provide good correlations with chromatographic behavior of the studied structurally related drugs. This research was completed on three pretreated silica gel plates via impregnation in urea, sodium dodecyl sulfate, and dimethylformamide, hence it possesses varying interplay mechanisms and polarities. The retention parameters were obtained by utilizing four solvent systems of two additives of variable ratios, consequently specific polarities in addition to imparted different pH values using either glacial acetic acid or liquid ammonia. Calculated theoretical approaches prove good correlations between investigated descriptors and retention factors. Some correlations show excellent predicting models, which might be critical for toning better know‐how relationships between chemical structures and retention of β‐blockers. [ABSTRACT FROM AUTHOR]

High-pressure and high-temperature Brillouin scattering studies have been performed on liquid of composition corresponding to the ammonia dihydrate stoichiometry (NH3·2H2O) in a diamond anvil cell. Using the measured Brillouin frequency shifts from 180° back- and 60° platelet-scattering geometries, the acoustic velocity, refractive index, density, and adiabatic bulk modulus have been determined under pressure up to freezing point along the 296, 338, 376, and 407 K isotherms. Along these four isotherms, the acoustic velocities increase smoothly with increasing pressure but decrease with the increased temperature. However, the pressure dependence of the refractive indexes on the four isotherms exhibits a change in slope around 1.5 GPa. The bulk modulus increases linearly with pressure and its slope, dB/dP, decreases from 6.83 at 296 K to 4.41 at 407 K. These new datasets improve our understanding of the pressure- and temperature-induced molecular structure changes in the ammonia-water binary system. [ABSTRACT FROM AUTHOR]

The high temperature and high pressure Brillouin scattering studies of liquid ammonia have been performed in a diamond anvil cell. Acoustic velocity, refractive index, adiabatic bulk modulus, and the equation of state of liquid ammonia were determined at temperatures up to 410 K and at pressures up to the solidification point. Velocity and refractive index increase smoothly with increasing pressure along isothermals but decrease slightly with the temperature increase. The bulk modulus increases linearly with pressure and its slope dB/dP decreases slightly with increasing temperature from 6.67 at 297 K to 5.94 at 410 K. [ABSTRACT FROM AUTHOR]

The microscopic dynamics of four prototype systems (water, ammonia, nitrogen, and neon) across the critical temperature has been investigated by means of high-resolution inelastic x-ray scattering. The experimental line shape has been described using a model based on the memory function formalism. Two main relaxations, the thermal and the structural one, were observed in all the investigated systems. We found that the microscopic mechanism driving the structural relaxation clearly changes, being mainly governed by intermolecular bond rearrangements below the critical temperature and by binary collisions above it. Moreover, we observed that the relative weight of the thermal relaxation systematically increases on approaching the critical temperature, thus allowing for the observation of a transition from an adiabatic to an isothermal regime of sound propagation. Finally, we found the presence of an additional instantaneous relaxation, likely related to the coupling between collective vibrational modes and intramolecular degrees of freedom. [ABSTRACT FROM AUTHOR]

The dynamic structure factor S(Q,ω) of liquid ammonia has been measured by inelastic x-ray scattering in the terahertz frequency region as a function of the temperature in the range of 220–298 K at a pressure P=85 bars. The data have been analyzed using the generalized hydrodynamic formalism with a three term memory function to take into account the thermal, the structural, (α) and the microscopic (μ) relaxation processes affecting the dynamics of the liquid. This allows to extract the temperature dependence of the structural relaxation time (τα) and strength (Δα). The former quantity follows an Arrhenius behavior with an activation energy Ea=2.6±0.2 kcal/mol, while the latter is temperature independent suggesting that there are no changes in the interparticle potential and arrangement with T. The obtained results, compared with those already existing in liquid water and liquid hydrogen fluoride, suggest the strong influence of the connectivity of the molecular network on the structural relaxation. [ABSTRACT FROM AUTHOR]

To reduce greenhouse gases in accordance with stringent emission regulations, interest in ammonia, a carbon-free fuel, is increasing in the heavy-duty engine industry. Pre-mixed ammonia-diesel dual-fuel combustion showed better results than diesel combustion in efficiency and greenhouse gas emissions, but NO and unburned NH 3 levels were significant. Therefore, a liquid ammonia direct injection strategy should be considered, and that requires detailed combustion and emission formation process analyses. Therefore, in this study, a numerical analysis of the direct injection ammonia-diesel combustion process was conducted, and an optimal injection strategy was sought. Compensating for the slow flame speed of ammonia by supplying additional momentum to the ammonia through direct injection could improve combustion characteristics. Furthermore, NO removal could be promoted by widening the thermal DeNO x reaction region compared to that in pre-mixed ammonia-diesel combustion. At injection timing was −7 CAD for the ammonia injection and −15 to −10 CAD for the diesel injection, the efficiency increased by 8 %, NO emissions were reduced by up to 13.5 %, and GHG emissions were reduced by about 91 % compared with diesel alone. In addition, unburned ammonia was reduced to least 58.4 ppm, a significant improvement over pre-mixed ammonia combustion. • Direct injection of ammonia reduces the effects of slow flame propagation. • Ammonia direct injection can improve NO emissions over pre-mixed combustion. • Applicable ammonia energy fraction limit was 97 % with ammonia direct injection. • Improving in efficiency, NO x , and GHG compared to diesel using ammonia direct injection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigates the directional transformation of N in pig manure. • 84.62% of N is enriched into liquid during supercritical water gasification. • Maximum NH 4 +-N predominated the liquid N at 620 °C in the presence of K 2 CO 3. • A few of N remained in solid residues with stable quaternary-N. • The conversion and stability of N rely on catalysts rather than temperature. Nitrogen is a valuable nutrient element in pig manure. This work focuses on investigating the distribution, directional transformation, and migration pathways to facilitate the recovery of nitrogen from supercritical water gasification products. Results indicated that no nitrogen-containing gas was detected and 12.65 % of nitrogen remained in solid products. 82.49 % of nitrogen migrated into liquid products, which are predominated by ammonia. Catalysts were employed to promote the conversion of solid nitrogen to liquid nitrogen and organic nitrogen to ammonia. Finally, 85 % of nitrogen is enriched into liquid products and ammonia predominated the liquid nitrogen. The percentage of ammonia increased to 97.51 % at 620 °C in the presence of potassium carbonate. The migration pathways indicated that nitrogen was transformed into ammonia by various intermediates such as indole. The rest of the nitrogen remained in solid products with stable quaternary-nitrogen. These findings provide valuable insights into nitrogen management and recovery. [ABSTRACT FROM AUTHOR]

• Numerical simulations of spherically expanding liquid ammonia flames are conducted. • A comparison is made between gaseous and liquid ammonia flames. • Reaction heat release and evaporation heat loss compete to dominate flame propagation. • The effects of equivalence ratio, temperature, and ammonia heat fraction are explored. Directly using liquid ammonia in combustion devices can simplify the fuel supply system and reduce equipment costs. However, the detailed ignition and propagation mechanisms of liquid ammonia flames have not been fully understood. This study aims to investigate the ignition and propagation of liquid ammonia flames numerically under various conditions. Spherically expanding liquid ammonia flames are studied using detailed chemistry. The effects of initial temperatures, droplet diameters, equivalence ratios, and heat fraction are investigated. The results indicate that the rapid flash boiling of liquid ammonia droplets leads to a strong local heat loss, hindering the ignition and propagation of the flame. Preheating can significantly increase the reaction rate, which compensates for the heat loss caused by phase change, allowing the flame kernel to ignite and propagate outwards. While droplet-flame interaction is present but not significant due to the rapid evaporation of liquid ammonia. The effect of droplet on the flame surface curvature is only distinguishable at conditions of large diameter. Equivalence ratio and ammonia heat fraction ratio change the amount of liquid ammonia. The more liquid ammonia, the more heat is absorbed by the phase change process, making the flame more difficult to be ignited. [ABSTRACT FROM AUTHOR]

• Chemical kinetic model was improved to better predict NH 3 /CH 3 OH oxidation process. • HO 2 generated a substantial amount of OH radicals and facilitated the oxidation of methanol and ammonia. • More than 80% of the N 2 O was produced by NH 2 + NO 2 = N 2 O + H 2 O. • NH 2 promoted the conversion of NO x to N 2. Methanol and liquid ammonia can form a mixture with better combustion quality. In order to investigate the ammonia (NH 3)/methanol (CH 3 OH) mixture oxidation process, jet-stirred reactor (JSR) oxidation experiments were conducted at atmospheric pressure and temperature of 700–1200 K. The concentration of NH 3 in the NH 3 /CH 3 OH mixture was 80%, 60%, and 40%, respectively, for equivalent ratios of 0.8, 1.0, and 1.2. By using synchronous vacuum ultraviolet photoionization mass spectrometry, important species (such as CH 2 O, CO, NO, NO 2 , N 2 O) involved in the oxidation reaction were identified and quantified. The original chemical kinetic model was validated and optimized based on experimental data, which improved the model's ability to predict NH 3 /CH 3 OH oxidation process (the overall improvement is approximately 81.3% compared to the original mechanism). The results demonstrated that methanol accelerated the rate of ammonia oxidation, and methanol was rapidly oxidized at high methanol content. The sensitivity analysis of reaction pathways with varying equivalent ratios revealed that HO 2 generated a substantial amount of OH radicals and facilitated the oxidation of methanol and ammonia. During the oxidation of ammonia, nearly half of the NO produced NO 2 through NO + HO 2 = NO 2 + OH, and about 60% of the NO came from the reduction reaction of NO 2. More than 80% of the N 2 O was produced by NH 2 + NO 2 = N 2 O + H 2 O, and most of the N 2 O was converted to N 2 , while NH 2 promoted the conversion of NO x to N 2. [ABSTRACT FROM AUTHOR]

• Ignition and diffusion combustion process of liquid phase ammonia spray ignited by diesel jet were investigated by optical diagnostics prospectively. • The effective ammonia ignition zone by diesel spray is the space of gas entrainment zone except for the liquid phase ammonia volume under evaporated condition. • The ammonia spray can be ignited by diesel jet only at the effective ignition zone, otherwise the ammonia spray would extinguish the diesel flame without being ignited. • An effective regulation scheme to achieve stable diffusion combustion of ammonia has been proposed, which can at least realize the ammonia energy replacement of 74.4%. Ammonia fueled engines applying diffusion combustion mode is expected to further improve the thermal and combustion efficiencies with high burning rate and high ammonia energy replacement. However, there is a lack of the fundamental studies about ammonia diffusion combustion characteristics. Therefore, the fundamental optical experiments of liquid phase ammonia spray and combustion, which is ignited by pilot diesel injection, were performed to investigate the ignition and diffusion combustion characteristics of liquid phase ammonia. According to the high-speed photography, interaction processes between the liquid phase ammonia spray and the diesel spray had been described, and the whole ignition and combustion processes were also recorded in detail. The discussion about the effect of diesel jet ignition location on ammonia ignition process shows that the effective ammonia ignition zone by diesel spray is the region of gas entrainment zone except for the liquid phase ammonia volume under evaporated condition, where the interval on ammonia spray axis is about 16 mm ∼ 35 mm away from the ammonia nozzle exit under the current experimental conditions, and the ammonia spray is failed to be ignited at any region out of the effective ignition zone. Moreover, the ammonia diffusion combustion characteristics under various ammonia injection durations reveals that the entrainment, including both the diesel flame and the surrounding ambient gas, into the effective ignition zone of liquid phase ammonia spray, is the effective way to achieve reliable ignition and the subsequent diffusion combustion of ammonia, which can increase the energy ratio (ammonia to pilot diesel) up to at least 2.9. Finally, based on the control of combustion mode of the pilot diesel, utilizing premixed diesel flame to induce the diffusion combustion of ammonia is proved to be an effective regulation scheme to enhance the performance of ammonia combustion under engine-like thermal conditions. [ABSTRACT FROM AUTHOR]

• Accurate process models for kW-level ammonia SOFC systems are developed. • Effect of off-gas recirculation on ammonia SOFC system is studied with energy flow diagram. • An optimization strategy by off-gas steam separation is proposed for ammonia SOFC system. • Comprehensive analyses of efficiency, power density and thermal safety are conducted. Solid oxide fuel cell (SOFC) power system fueled with the carbon-free fuel ammonia is a promising technique to reduce CO 2 in traffic and transportation sector. This study constructed zero-dimensional steady-state models for the SOFC stack and corresponding balance of plant (BOP) components, and conducted efficiency, power density and thermal safety analysis on a kW level ammonia SOFC system. The effects of off-gas recirculation strategy on system performance were firstly studied. The results show that in the basic ammonia SOFC system without off-gas recirculation, the fuel and air stream entering the afterburner are strictly determined by the stack operating parameters such as stack fuel utilization and flow rate. This makes its net electrical efficiency be not only low but also impossible to be independently and flexibly adjusted via controlling the fuel thermally consumed in the afterburner. The use of anode off-gas recirculation (AOGR) greatly improves the net electrical efficiency and operating flexibility via decoupling the system fuel utilization from the stack fuel utilization. By contrast, cathode off-gas recirculation (COGR) exhibits adverse effects, which reduces the net electrical efficiency and is not conducive to the thermal stability of the afterburner. In the end, a new system architecture design (SOFC-AOGR-SS) is proposed, which adopts both AOGR and steam separation in the anode recirculated off-gas using the vaporization cooling of liquid ammonia. The proposed system could operate at extended stack fuel utilization range of 0.67–0.80 and achieve a net electricity efficiency of 51.94–56.50% without external cooling water. Moreover, with additional external cooling water, the stack fuel utilization range and the net electricity efficiency of system could be extended to 0.58–0.80 and 51.84–57.15% respectively. [ABSTRACT FROM AUTHOR]

Ammonia is an alternative carbon-free fuel that can be easily stored in a liquid phase, unlike hydrogen, and then directly utilized in diesel engines. Hence, a single-cylinder diesel engine was retrofitted for direct injection of liquid ammonia with pilot ignition of biodiesel in dual fuel combustion mode. The effects of the liquid phase of ammonia and ammonia energy share (AES) on combustion, emissions, and engine performance were investigated and compared with pure biodiesel operation. Moreover, various ammonia injection timings were studied to improve ammonia/biodiesel combustion and reduce emissions. A CFD model was developed and validated with experimental data to study ammonia/biodiesel sprays, combustion characteristics, and emissions formation. The results showed higher AES significantly reduced the local cylinder temperature due to the strong cooling effects of ammonia, therefore, a maximum AES of 50% was achieved. Increasing AES to 50% decreased combustion duration and combustion phasing by 26.2 and 4.4 CAD, respectively. However, it deteriorated the indicated thermal efficiency (ITE) by 1.3 percent point compared to pure biodiesel. Furthermore, retarding ammonia injection from −25 to −10 CAD significantly reduced NO x , CO, and ammonia emissions by 31.4%, 39.6%, and 31.3%, respectively. Ultimately, the optimal operating condition was suggested when ammonia was injected at −10 CAD and biodiesel at −16 CAD with AES of 50%. • The ammonia-biodiesel dual direct injection engine was investigated. • The ammonia spray and combustion characteristics were studied by the CFD. • Direct ammonia injection reduced unburned ammonia by 10813 ppm compared to the port injection. • Late injection of ammonia at −10 CAD reduced NO x and NH 3 emissions by 31% at the same time. [ABSTRACT FROM AUTHOR]

For the first time, the photoanodic behavior of undoped n-InP (≈ 1015 atoms.cm−3) is studied in liquid ammonia at low temperature (-55 °C) under atmospheric pressure. Under illumination, the low doping level provides unique conditions to monitor charge transfer at the interface since only photo-generated holes are involved in the passivation mechanism. Specific photoanodic transient phenomena are observed due to the photo-holes availability at the interface which depends on light intensity. Cycle voltammograms differ strongly from the initial ones in the dark. Photo-electrochemical transformations of InP responses are followed by cycle voltammetry for two conditions of illumination; under low and high luminous flux intensity. In spite of a pure photo-holes process for both cases, voltammograms are highly dependent on light intensity while impedance measurements present the same strong modifications. One-volt positive shift of the flat band potential is indeed observed. However, whatever is the luminous flux intensity, a low photo-anodic charge is consumed (≈ 1 mC.cm−2) and the same ultra-thin film of polyphosphazene onto n-InP is shown by XPS analyses. Properties of this new interface is discussed in term of energy diagram and photo-holes transfer ability. Under these experimental conditions used, (J ≤ 100 µA.cm−2 and Q ≈ 50 mC.cm−2), the passivated interface behaves as a photoanode toward ammonia oxidation since the ultra-thin film is maintained onto InP. [ABSTRACT FROM AUTHOR]

High-level ab initio calculations have been carried out to evaluate the lifetimes of complexes formed by the association of Cu2+ to water, ammonia, and hydrogen cyanide. The corresponding binding energies were evaluated at the CCSD(T)/6-311+G(3df,2pd) level of theory. The potential-energy curves corresponding to their dissociation into Cu++L+ (L=H2O, NH3, and HCN) were obtained at the CCSD(T)/6-311+G(3df,2p) level on BHLYP/6-311+G(d,p) optimized geometries. Lifetimes were calculated using the exterior complex scaling and the semiclassical WKB methods. Although all the complexes investigated are thermodynamically unstable with respect to their dissociation into Cu++L+ in a typical Coulomb explosion, the activation barrier is high enough to accommodate several vibrational resonances, with very large lifetimes. As a matter of fact, if the three complexes are produced in the lowest vibrational levels, they behave as totally bound (with almost infinite lifetime) species. [ABSTRACT FROM AUTHOR]

Resonance enhanced multiphoton ionization and cavity ring down spectroscopies have been used to provide spatially resolved measurements of relative H atom and CH[sub 3] radical number densities, and NH column densities, in a hot filament (HF) reactor designed for diamond chemical vapor deposition and here operating with a 1% CH[sub 4]/n/H[sub 2] gas mixture—where n represents defined additions of N[sub 2] or NH[sub 3]. Three-dimensional modeling of the H/C/N chemistry prevailing in such HF activated gas mixtures allows the relative number density measurements to be placed on an absolute scale. Experiment and theory both indicate that N[sub 2] is largely unreactive under the prevailing experimental conditions, but NH[sub 3] additions are shown to have a major effect on the gas phase chemistry and composition. Specifically, NH[sub 3] additions introduce an additional series of "H-shift" reactions of the form NH[sub x]+H...NH[sub x-1]+H[sub 2] which result in the formation of N atoms with calculated steady state number densities >10[sup 13] cm[sup -3] in the case of 1% NH[sub 3] additions in the hotter regions of the reactor. These react, irreversibly, with C[sub 1] hydrocarbon species forming HCN products, thereby reducing the concentration of free hydrocarbon species (notably CH[sub 3]) available to participate in diamond growth. The deduced reduction in CH[sub 3] number density due to competing gas phase chemistry is shown to be compounded by NH[sub 3] induced modifications to the hot filament surface, which reduce its efficiency as a catalyst for H[sub 2] dissociation, thus lowering the steady state gas phase H atom concentrations and the extent and efficiency of all subsequent gas phase transformations. [ABSTRACT FROM AUTHOR]

A quantum mechanical charge field (QMCF) molecular dynamics (MD) simulation has been carried out to describe the structural and dynamical properties of Cu+ ion in liquid ammonia. The first and second shells were treated by ab initio quantum mechanics at the Hartree−Fock (HF) level with the DZP-Dunning basis set for ammonia and LANL2DZ ECP basis set for Cu. The system was equilibrated for 4 ps, then the trajectory data was collected every fifth step for 20 ps at 235.15 K. The structural analysis showed that in the first solvation shell, Cu+ is solvated by 4 ammonia molecules forming a stable structure of tetrahedral with Cu-N bond length of 2.15 Å, whereas in the second solvation shell there are 29 ammonia molecules that have an average distance of 4.79 Å to Cu+ ion. Mean residence time of 3.06 ps was observed for the ammonia ligand in the second solvation shell indicating for a highly unstable structure of the solvation shell. The obtained structure of the first solvation shell from this simulation is in excellent agreement with experimental data.

Reduction of the heteroleptic metal carbonyl complex Mo(CO)3(η5-Cp)H with the metallic salt Cs5Bi4 in the presence of [2.2.2]crypt (= 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) in liquid ammonia led to single crystals of bis[(4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)caesium] pentacarbonylmolybdate, [Cs(C18H36N2O6)]2[Mo(CO)5] or [Cs([2.2.2]crypt)]2[Mo(CO)5]. The twofold negatively charged anionic complex corresponds to the 18 valence electron rule. It consists of an Mo atom coordinated by five carbonyl ligands in a shape intermediate between trigonal–bipyramidal and square-pyramidal. The Mo—C distances range from 1.961 (3) to 2.017 (3) Å, and the C[triple-bond]O distances from 1.164 (3) to 1.180 (4) Å.

MXenes have demonstrated significant potential in electrochemical energy storage, particularly in supercapacitors, owing to their exceptional properties. The surface terminal groups of MXene play a pivotal role in pseudocapacitive mechanism. Considering the hindered electrolyte ion transport caused by -F terminal groups and the limited ion binding sites associated with -O terminal groups, this study proposes a novel strategy of replacing -F with -N terminal groups. The modulated MXene-N electrode, featuring a substantial number of -N terminal groups, demonstrates an exceptionally high gravimetric capacitance of 566 F g -1 (at a scan rate of 2 mV s -1 ) or 588 F g -1 (at a discharge rate of 1 A g -1 ) in 1 м H 2 SO 4 electrolyte, and the potential window is significantly increased. Furthermore, subsequent spectra analysis and density functional theory calculations are employed to investigate the mechanism associated with -N terminal groups. This work exemplifies the significance of terminal modulation in the context of electrochemical energy storage., (© 2023 Wiley-VCH GmbH.)

Studies the structure of liquid ammonia by classical ab initio, classical and path-integral molecular dynamics. Types of calculations employed to generate insights into the ability of theoretical methods to model liquid ammonia; Limitations of using the methods; Characteristics of the intramolecular quantum structure.