Interaction in the zinc perchlorate–urea–perchloric acid–water system at 25°С

Heterogeneous equilibria in the zinc perchlorate–urea–perchloric acid–water quaternary system at 25°С were studied by investigating solubility. The crystallization regions were found for the initial solid components, eutonic compositions of the ternary systems constituting the quaternary system, binary compounds of urea with zinc perchlorate and perchloric acid, and also two new coordination compounds containing simultaneously zinc perchlorate, urea, and perchloric acid: ZnClO₄ · 4CO(NH₂)₂ · HClO₄ and ZnClO₄ · 2CO(NH₂)₂ · HClO₄.     

Solubility in the manganese perchlorate–urea–perchloric acid–water system at 25°С

Heterogeneous equilibria in the manganese perchlorate–urea–perchloric acid–water quaternary system at 25°С were studied by investigating solubility. The crystallization regions were determined for the initial solid components, eutonic compositions of ternary systems constituting the quaternary system, binary compounds of urea with manganese perchlorate and perchloric acid, and also two new coordination compounds containing simultaneously manganese perchlorate, urea, and perchloric acid: Mn(ClO₄)₂ · 4CO(NH₂)₂ · HClO₄ and Mn(ClO₄)₂ · 2CO(NH₂)₂ · HClO₄.     

Ein neuartiges Diorganylzinn(IV)-Komplexkation als Gastspezies in einer ionischen Harnstoff-Einschlußverbindung: Bildung und Struktur von [trans-Me2Sn{OC(NH2)2}4]2+ · 2 (MeSO2)2N7 · 6 (NH2)2CO

Polysulfonylamines. CVIII. A Novel Diorganyltin(IV) Complex Cation as Guest Species in an Ionic Urea Inclusion Compound: Formation and Structure of [ trans -Me₂Sn{OC(NH₂)₂}₄]²⁺ · 2 (MeSO₂)₂N⁷ · 6 (NH₂)₂CO The title compound (triclinic, space group P 1, Z = 1, X-ray analysis at –130 °C) was fortuitously obtained during an attempt to complex the known dimeric hydroxide [Me₂Sn(A)(μ-OH)]₂, where A⁷ = (MeSO₂)₂N⁷, with four equivalents of urea. The trans-octahedral and crystallographically centrosymmetric [Me₂Sn(urea)₄]²⁺ cation (Sn–O 221.6 and 223.7 pm, cis-angles in the range 90 ± 1.5°) is the first structurally authenticated [R₂Sn(L)₄]²⁺ complex featuring a urea-type ligand L. In the crystal, these cations are sandwiched between and hydrogen-bonded to puckered layers corresponding to the [011] family of planes. Each layer is constructed from rows of A⁷ anions, which extend parallel to the x axis and are alternatingly cross-linked by a planar zig-zag tape of urea molecules or by a pair of inversion-related urea zig-zag tapes displaying a non-planar roof profile. The structure contains 23 crystallographically independent hydrogen bonds N–H…O/N, comprising two intracationic N–H…O bonds, two and four N–H…O bonds leading to the two respective types of urea tapes, eight N–H…O bonds and one N–H…N⁷ bond connecting the urea tapes to the electronegative atoms of the anions, and six N–H…O interactions between the ligands of the complex guest cation and C=O or S=O acceptors within the layers of the host lattice. The anion A⁷ accepts a total of twelve H bonds and adopts a previously unreported conformation.     

Solar Urea: Towards a Sustainable Fertilizer Industry

Urea, an agricultural fertilizer, nourishes humanity. The century-old Bosch–Meiser process provides the world's urea. It is multi-step, consumes enormous amounts of non-renewable energy, and has a large CO₂ footprint. Thus, developing an eco-friendly synthesis for urea is a priority. Herein we report a single-step Pd/LTA-3A catalyzed synthesis of urea from CO₂ and NH₃ under ambient conditions powered solely by solar energy. Pd nanoparticles serve the dual function of catalyzing the dissociation of NH₃ and providing the photothermal driving force for urea formation, while the absorption capacity of LTA-3A removes by-product H₂O to shift the equilibrium towards urea production. The solar urea conversion rate from NH₃ and CO₂ is 87 μmol g^?1 h^?1. This advance represents a first step towards the use of solar energy in urea production. It provides insights into green fertilizer production, and inspires the vision of sustainable, modular plants for distributed production of urea on farms.     

(NH4)6Nd(NO3)9, ein ammoniumreiches ternäres Lanthanidnitrat mit einsamen Nitrationen: (NH4)6[Nd(NO3)6](NO3)3

(NH₄)₆Nd(NO₃)₉, A Ternary Ammonium-Rich Lanthanide Nitrate with Lonesome Nitrate Ions: (NH₄)₆[Nd(NO₃)₆](NO₃)₃ . Single crystals of the ternary ammonium neodymium nitrate (NH₄)₆Nd(NO₃)₉ are obtained from a solution of Nd₂O₃ in a melt of NH₄NO₃. In the crystal structure (monoclinic, C 2/c, Z = 4, a = 1 775.1(4), b = 912.7(3), c = 2 072.3(5) pm; β = 125.56(1)°; R = 0.059, R_w = 0.036) the Nd³⁺ ion is surrounded by six bidentate nitrate ligands so that anionic units [Nd(NO₃)₆]^3? are formed. The units are isolated, but they are incorporated in layers parallel to (010). The structure is held together by a network of hydrogen bonds, built up by NH₄⁺ and NO₃^? ions lying between the layers. Due to the structure, the compound may be described as a double salt like (NH₄)₃[Nd(NO₃)₆] · 3 NH₄NO₃ or, better, as (NH₄)₆[Nd(NO₃)₆](NO₃)₃.     

Ammonium-exchanged phase of γ-titanium phosphate

The monoammonium salt of γ-titanium phosphate has been prepared by hydrothermal treatment of π-Ti₂O(PO₄)₂·2H₂O in the presence of urea and phosphoric acid, and its crystal structure was obtained by Rietveld analysis using powder X-ray diffraction data. γ-Ti(PO₄)(NH₄HPO₄) crystallizes in the monoclinic space group P2₁/m with a = 5.0725(3) Å, b = 6.3101(3) Å, c = 11.2435(5) Å, β = 97.980(3)° (Z = 2). The structure consists of 2D titanium phosphate layers in the ab-plane. The titanium atoms and one of the phosphate groups are located nearly in the ab-plane of the layer. All the oxygen atoms of this phosphate group are involved in titanium coordination sphere. The other phosphate group located in the layers edges links two neighboring titanium atoms in the a-direction through two of its oxygen atoms. The remaining two oxygens are pointed toward the interlayer space being involved in hydrogen bond interactions with the ammonium ions. Each ammonium ion is shared by four oxygens belonging to four different phosphate hydroxyl groups. γ-Ti(PO₄)(NH₄HPO₄) is stable until 453 K, while above this temperature, it transforms to γ’-Ti(PO₄)(NH₄HPO₄) high temperature polymorph stable until 573 K. Thermal decomposition of this material leads to cubic TiP₂O₇ structure, with previous formation of two intermediate pseudo-layered compounds: Ti(PO₄)(NH₄HP₂O₇)_0.5 and Ti(PO₄)(H₂P₂O₇)_0.5. The activation energy of thermal decomposition has been calculated as a function of the extent of conversion applying the Kissinger–Akahira–Sunose (KAS) isoconversional method to the thermogravimetric data.     

Synthesis and thermal decomposition of Cr–urea complex

In this work, Cr–urea complex ([Cr(NH₂CONH₂)₆](NO₃)₃) was synthesized by direct solid-state reaction of chromium nitrate and urea, and its thermal decomposition reaction was studied for the first time to explore the possibilities of using the complex as precursor to nanosized chromium oxide. The formation of [Cr(NH₂CONH₂)₆](NO₃)₃ is confirmed from infrared spectroscopy and elemental analysis. Thermogravimetric and differential thermal analysis of the compound show a three-stage thermal decomposition in the temperature range from 190 to 430 °C. The result of X-ray diffraction (XRD) shows that the [Cr(NH₂CONH₂)₆](NO₃)₃ decompose at ~300 °C into α-Cr₂O₃ nanopowder with an average crystallite size of 33 nm.     

基于尿素电合成反应的电催化剂研究进展

尿素是一种重要的化工原料并作为氮源广泛应用于化肥生产。工业合成尿素由氮气加氢合成氨气以及氨气和二氧化碳转化为尿素两步实现,存在高能耗和高污染等问题。通过电催化碳氮偶联,将二氧化碳和氮源（氮气、硝酸根、亚硝酸根、一氧化氮等）转化为尿素,可直接跳过合成氨反应并在温和的反应条件下同时实现人工固氮和固碳。因此,尿素电合成技术不仅避免了高能耗和高污染,还能够实现惰性气体分子的高效利用,对于加快实现“碳达峰碳中和”战略有着重要的意义。本文聚焦尿素电合成这一前沿研究热点,结合领域内最新研究进展,首先介绍了不同电催化剂的设计策略及其催化机制,随后总结了电催化碳氮偶联合成尿素的反应机理,并对尿素电合成的后续研究方向进行了展望。     

Sur le dosage argentométrique de l'anion phosphorique

1. In aqueous solutions of phosphoric acid or alcali phosphates, the PO₄^-3can be determined by potentiometric titraition with silver nitrate PO₄^-3 + 3 Ag⁺ ár unAg₃PO₄↓The pH value of the solution is maintained about 9 by using borax-buffer 2 The determination of phosphate ion is also possible by precipitation of Ag₃PO₄ with an excess of silver nitrate, the pH of the solution is adjusted between 7 and 8 by using a new buffer mixture containing NH₄⁺, NHXXX, and Ag⁺. After diluting the solution up to a known volume and filtering through dry filter paper, the excess of silver is determined by potentiometric titration with potassium bromide. This method gives very good results, it is applicable in the presence of Mg⁺² and Ca⁺². The presence of Fe⁺³ and Al⁺³ hinders the determination of the phosphate ion. 3. The properties of the ,,ammonium-silverdiamme” buffer system are described. This buffer contains NH₄⁺, NH₃ and Ag⁺ (the latter in excess with regard to NH₃)     

Thermal Decomposition of the System CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript> in the Presence of Nitrate Compounds

Chemical, derivatographic, IR spectral, and X-ray diffraction analyses were used to study thermal transformations in the system CO(NH₂)₂-H₃PO₄ and in the same system with addition of KNO₃, CsNO₃, LiNO₃ · 3H₂O, and NH₄NO₃ salts in the temperature range 20–600°C. The influence of the chosen nitrate compounds on the process of reorganization of the constituent ingredients, evolution of nitrogen into the gas phase, yield of the solid residue, and preservation of nitrogen and phosphorus was revealed.     

Ambient Electrosynthesis of Urea with Nitrate and Carbon Dioxide over Iron-Based Dual-Sites

The development of efficient electrocatalysts to generate key *NH₂ and *CO intermediates is crucial for ambient urea electrosynthesis with nitrate (NO₃⁻) and carbon dioxide (CO₂). Here we report a liquid-phase laser irradiation method to fabricate symbiotic graphitic carbon encapsulated amorphous iron and iron oxide nanoparticles on carbon nanotubes (Fe(a)@C-Fe₃O₄/CNTs). Fe(a)@C-Fe₃O₄/CNTs exhibits superior electrocatalytic activity toward urea synthesis using NO₃⁻ and CO₂, affording a urea yield of 1341.3±112.6 μg h⁻¹ mg_cat⁻¹ and a faradic efficiency of 16.5±6.1 % at ambient conditions. Both experimental and theoretical results indicate that the formed Fe(a)@C and Fe₃O₄ on CNTs provide dual active sites for the adsorption and activation of NO₃⁻ and CO₂, thus generating key *NH₂ and *CO intermediates with lower energy barriers for urea formation. This work would be helpful for design and development of high-efficiency dual-site electrocatalysts for ambient urea synthesis.     

Bulk properties and hydration numbers of components of water–salt,water–urea,and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH₂)₂CO?H₂O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm³ (44% NaCl) and 1.800÷1.849 g/cm³ (67% Na₂SO₄). In a saturated urea solution, NaNO₃, NaCl, and Na₂SO₄ complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO₃, NaCl, and Na₂SO₄. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.     

Part I. A specific electrode for urea.

A specific simple enzyme stirrer electrode is described for the assay of urea in blood serum. The enzyme is placed directly on a magnetic stirrer and held in place with a nylon net. The enzyme stirrer both stirs the solution and effects an enzymatic transformation, permitting the direct assay of a substrate such as urea. Potassium, Na⁺ , NH₄⁺ and other organic and inorganic species present in blood do not interfere. Linear curves are obtained from 5· 10^-2M to 1· 10^-4M urea with slopes close to Nernstian, 0.95 pH/decade. Urea in blood was assayed with an accuracy of 1.8% and a precision of 2.0% with immobilized urease in the stirrer. The stirrers were used for 15 weeks and over 500 assays with excellent results.     

Deep eutectic silsesquioxane hybrids with quaternary ammonium/urea derivatives: synthesis and physicochemical and ion-conductive properties

We report the synthesis of deep eutectic silsesquioxane hybrids (DE-SQs) by simple mixing of quaternary-ammonium-containing SQ and urea derivatives. Cationic SQ, which was prepared by the hydrolytic condensation of a triethoxysilane precursor derived from 2-(dimethylamino)ethyl acrylate, followed by a quaternization reaction with methyl iodide, was used as a quaternary-ammonium-containing SQ component. Cationic SQ reacted with urea at a 1:2 M ratio at 80 °C for 48 h to yield a viscous DE-SQ (2Urea) liquid with a low glass transition temperature (T_g = ?11 °C). Urea derivatives—1,3-dimethylurea (DMU) and 1,3-dimethylthiourea (DMTU)—were additionally used as hydrogen bond donors to form low-T_g DE-SQs. The thermal, physical, and ion-conductive properties of the DE-SQ family of organic–inorganic hybrids were investigated and characterized, and the influences of the nature of the urea derivative and their feed ratios on DE-SQ formation were evaluated. Among the DE-SQs developed in this study, DE-SQ (2Urea) and DE-SQ (2DMTU) achieved the highest ionic conductivity, with DE-SQ (2Urea) exhibiting 2.35 × 10^?6 and 6.63 × 10^?4 S cm^?1 at 25 and 75 °C, respectively, under anhydrous conditions. This is the first report on the synthesis of DE-SQs by simple mixing of two solids, wherein the resulting compounds exhibit low T_g, thermal stability, and characteristic ionic conductivity. The ability to incorporate unique DE units into the SQ structure facilitates the development of advanced organic–inorganic hybrid materials possessing a wide range of functions and applications.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Solvent‐Dependent Delamination,Restacking, and Ferroelectric Behavior in a New Charge‐Separated Layered Compound: [NH4][Ag3(C9H5NO4S)2(C13H14N2)2]⋅8 H2O

A new anionic coordination polymer, [NH₄][Ag₃(C₉H₅NO₄S)₂(C₁₃H₁₄N₂)₂] ⋅ 8 H₂O, with a two‐dimensional structure, has been synthesized by a reaction between silver nitrate, 8‐hydroxyquinoline‐5‐sulfonic acid (HQS), and 4,4′‐trimethylene dipyridine (TMDP). The compound stabilizes in a noncentrosymmetric space group, and the lattice water molecules and the charge‐compensating [NH₄]⁺ group occupy the inter‐lamellar spaces. The lattice water molecules can be fully removed and reinserted, which is accompanied by a crystalline–amorphous–crystalline transformation. This transformation resembles the collapse/delamination and restacking of the layers. To the best of our knowledge, this is the first observation of delamination and restacking in an inorganic coordination polymer that contains silver. The presence of a natural dipole (the anionic framework and cationic ammonium ions) along with the noncentrosymmetric space group gives rise to the room‐temperature ferroelectric behavior of the compound. The ferroelectric behavior is also water‐dependent and exhibits a ferroelectric–paraelectric transformation. The temperature‐dependent dielectric measurements indicate that the ferroelectric/ paraelectric transformation occurs at 320 K. This transformation has also been investigated by using in‐situ IR spectroscopy and PXRD studies. The second‐harmonic generation (SHG) study indicated values that are comparable to some of the known SHG solids, such as potassium dihydrogen phosphate (KDP) and urea.     

Study of the solubility of components in the NaClO3 · 2CO(NH2)2-NH2C2H4OH · CH3COOH-H2O system

The solubility of components in the NaClO₃ · 2CO(NH₂)₂-NH₂C₂H₄OH · CH₃COOH-H₂O system was studied by the visual polythermal method over wide temperature and concentration ranges. In the phase diagram, crystallization fields were determined for ice, urea, diurea sodium chlorate, acetic acid, monoethanolamine acetate, and the compound CO(NH₂)₂ · NH₂C₂H₄OH · CH₃COOH. The compound was identified by chemical, thermogravimetric, and X-ray powder diffraction analyses.     

Study of simultaneous solubility of salts in the ammonium nitrate–ammonium chloride–water system

Ternary eutectic of the NH₄NO₃–NH₄Cl–H₂O system at–23.6°С has been found using a set of theoretical and experimental methods. According to the data of visual-polythermal and differential thermal analyses data, crystallization surface of the system has been plotted at–23.6 to 100°С.     

Preparation of quaternized dimethylaminoethylmethacrylate grafted nonwoven fabric for the removal of phosphate

Dimethylaminoethylmethacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fabric was prepared by radiation-induced graft polymerization. Grafting conditions were optimized and about 150% DMAEMA grafted samples were used for further experiments. DMAEMA graft chains were later quaternized with dimethyl sulphate for the removal of phosphate ions. Adsorption experiments were conducted with quaternized DMAEMA grafted fabric for phosphate removal at low (0.5–25 ppm) and high phosphate concentrations (50–1000 ppm). Adsorbed phosphate amounts at pH 7 were found to be 63 mg phosphate/g polymer and 512 mg phosphate/g polymer for low (25 ppm) and high phosphate concentrations (1000 ppm) respectively showing the efficiency of the adsorbent material in removing phosphate. The pH effect on phosphate adsorption showed that the quaternized DMAEMA grafted nonwoven fabric can adsorb phosphate over a wide pH range (5.00–9.00) indicating that adsorbent material can effectively remove different forms of phosphate ions, namely H₂PO₄^?, HPO₄^2? and PO₄^3? in aqueous solution at this pH range where the species exist. Competitive adsorption experiments were also carried out with two concentration levels at pH 7 to investigate the effect of competing ions. Phosphate adsorption on quaternized DMAEMA grafted nonwoven fabric was found to be higher than the other competing ions at two concentration levels. At high concentration level, the adsorption order was phosphate>nitrite>bromide>sulphate>nitrate whereas at low concentration level, the order was phosphate?sulphate>bromide>nitrite>nitrate.     

Liquidus and glass transition temperatures of the ammonium nitrate-dimethylsulfoxide-water system

The liquidus temperature was measured in the ammonium nitrate-dimethylsulfoxide-water system over in the concentration range 0–60 mole% ammonium nitrate. The probable formation of the NH₄NO₃·nDMSO solvate with n=1.3–1.5 and the mixed solvate NH₄NO₃·DMSO·H₂O at 30 mole% ammonium nitrate and a DMSO:H₂O ratio of 4∶1 are indicated. The glass transition temperatures T _g were measured over a salt concentration range of 0–50 mol% ammonium nitrate and at various compositions of the mixed solvent (y _DMSO =0.1–0.9 mole fraction). At a constant mixed solvent composition, the dependence of the glass transition temperature on the salt concentration can be approximated by a linear relationship, as can its dependence on the DMSO content in the solution at constant salt concentration. The glass-forming composition regions were found and the limits of this region are discussed.