Thermal decyanation,a new organic reaction. II

When heated in solution at about 160°C, pyridine quaternary salts of bromomalonamides lose 1 mole of cyanic or isocyanic acid almost quantitatively in a manner quite analogous to the decarboxylation of an acid. By DTA and DSC, the crystalline salts are stable up to their melting points (>220°C) at which temperatures concurrent fusion and decyanation processes occur (endotherm); these are immediately followed by an exotherm related to the trimerization of cyanic acid. TGA measurements on the solid salts do not clearly define the loss of 1 mole of cyanic acid because in the solid state, thermal decyanation is accompanied to some extent by other pyrolytic reactions. Preparative methods for quaternizing poly(4-vinylpyridine) with bromomalonamide are described and two polymeric quaternary salts (33 and 100% substituted) were prepared and analyzed. These polyelectrolytes are water soluble and upon the addition of base the yellow polymeric nitrogen ylids are generated. Infrared spectra on the polymeric quaternary salts and visible spectra on the polymeric ylids are included. The ylid chromophore has an ε = 1800 at λ_max = 415 nm. The dilute solution viscosity behavior of these polymers in H₂O and in 0.05N KBr is typical of polyelectrolytes. Both polymers in dilute solution show a maximum in η_sp versus pH plots. In water, the viscosity of these polymers decreases with time, and it is proven that this results from a conformational change which accompanies amide hydrolysis rather than polymer backbone degradation. Glass transitions are not detectable by DTA but both polymers show well-defined trimerization exotherms for cyanic acid starting at 170–175°C. Thus, decyanation of the solid polymeric quaternary salts is more analogous to decyanation of the crystalline quaternarys in solution than as solids. TGA measurements on the polymers show weight losses which are of the correct order of magnitude and in the correct temperature range for monodecyanation. Some data are presented which suggest that perhaps a second mole of cyanic acid is lost at about 250°C. Quaternization of poly(4-vinylpyridine) with bromomalonamide reduces its gross decomposition temperature from 385°C to about 285–317°C. It is demonstrated how thermal decyanation can be used for the in situ generation of cyanic acid for the modification of organic compounds. The preparation of a partial urethane of poly(vinyl alcohol) using this method is described. We have also shown that aliphatic quaternary salts can be prepared and that they too undergo the decyanation reaction.     

Soluble polymer-supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 15a-d ) with carbon dioxide (CO₂) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO₂ proceeded very smoothly to give the corresponding five-membered cyclic carbonates ( 16a-d ) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.     

Multicomponent systems LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>–Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>

Phase equilibria in the LiCl–LiBr–Li₂SO₄ ternary system and the LiCl–LiBr–Li₂SO₄–Li₂MoO₄ quaternary system were studied by differential thermal analysis. The compositions and temperatures of minima in the ternary and quaternary systems were determined to be (31.2 mol % LiCl, 46.8 mol % LiBr, 22.0 mol % Li₂SO₄, 460°C) and (25.2 mol % LiCl, 30.2 mol % LiBr, 14.6 mol % Li₂SO₄, 30.0 mol % Li₂MoO₄, 411°C), respectively.     

Thermodynamic performance of the NaNO3–NaCl–NaNO2 ternary system

Calculations of phase diagram for additive ternary molten salt system are carried out by the conformal ionic solution theory. The liquidus temperatures of the system NaNO₃–NaCl–NaNO₂ are determined according to different types of solid–liquid equilibrium and different values of the binary interaction coefficients. For the system NaNO₃–NaCl–NaNO₂, the calculated and experimental temperatures differ are very small below 673 K, but the oxidation and decomposition of the mixed salts are found when the temperature is higher than 673 K. Meanwhile, the eutectic point is obtained from calculated phase diagram and the eutectic temperature is 507 K. Thermal stability of this eutectic mixture is investigated by thermo-gravimetric analysis device. Experimental results show this kind of molten salt has a lower melting point (501.28 K), similar to solar salt (493 K). It is thermally stable at temperatures up to 819 K, and may be used up to 827 K for short periods.     

High-temperature equilibria and critical phenomena in the Na2CO3-NaCl-H2O and Na2CO3-Na2WO4-H2O systems

Phase equilibria in the Na₂CO₃-NaCl-H₂O and Na₂CO₃-Na₂WO₄-H₂O ternary systems formed by type 1 salts (NaCl, Na₂WO₄) and a type 2 salt (Na₂CO₃) were experimentally studied at temperatures from 425 to 500°C and pressures from 30 to 160 MPa with the contents of type 1 salts from 10 to 30 wt %. Transition from supercritical homogeneous fluid equilibria of the Na₂CO₃-H₂O system to heterogeneous equilibria of the title ternary systems was studied in the presence or absence of liquid phase immiscibility in the type 1 subsystems.     

Insoluble polystyrene-bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO₂) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO₂ proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.     

Amino-group excites vitality in nitrogen-rich energetic salts of triazolium

Incorporating amino groups is an efficient strategy for the tuning properties of energetic materials. However, there is no unanimous conclusion on the effect of the number of amino groups (−NH₂) on performance. Therefore, in this study, different number of −NH₂ of four energetic salts of triazolium based on oxadiazole and triazole were designed and synthesized. The structure features of energetic salts 4 – 6 were then investigated by single-crystal X-ray diffractions and Hirshfeld surfaces analyses. Afterward, the effects of −NH₂ were evaluated by thermal stability, impact sensitivity and detonation performance. All these energetic salts were insensitive to mechanical stimulation (IS >40 J), but the thermal decomposition temperatures of energetic salt 5 – 7 with −NH₂ are 24 °C to 54 °C higher than energetic salt 4 without −NH₂. Moreover, energetic salt 5 with one −NH₂ has the highest theoretical detonation properties compared to those without −NH₂ ( 4 ) and with two −NH₂ ( 6 , 7 ). These observations revealed that appropriate amount of −NH₂ can lead to desirable increase in the energetic properties, and this work can offer guidance for the design and synthesis of further energetic salts.     

LiCl-LiBr-LiVO3 and LiCl-LiBr-Li2MoO4 ternary systems

Phase equilibria in the LiCl-LiBr-LiVO₃ and LiCl-LiBr-Li₂MoO₄ ternary systems have been investigated by differential thermal analysis. The following compositions have been revealed (mol %): eutectic in the LiCl-LiBr-LiVO₃ system (18.0% LiCl, 72.0% LiBr, and 10.0% LiVO₃) with a melting point of 464°C and specific enthalpy of melting of 213 kJ/kg, and a minimum in the LiCl-LiBr-Li₂MoO₄ system (27.0% LiCl, 48.0% LiBr, and 25.0% Li₂MoO₄) with a melting point of 444°C. The investigation of ternary systems including salts of alkali metals is of practical interest for chemical industry and metallurgy, where salt mixtures are used as fused electrolytes and heat carriers. Original Russian Text ? T.V. Gubanova, E.I. Frolova, I.K. Garkushin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1220–1223.     

Formation of complex and double salts in systems MX2-NR4X-H2O [M = Cd(II), Cu(II), Co(II), Mg(II); X = Cl, Br; R = Me, Et, Bu] at 25°C

Results of an experimental research of phase equilibrium in ternary systems MX₂-NR₄X-H₂O [M = Cd(II), Cu(II), Co(II), Mg(II); X = Cl, Br; R = Me, Et, Bu] at 25°C were reported. A comparative analysis of compositions of solid compounds and regions of their crystallization, which are equilibrium with liquid phase, was conducted. An effect of hydration, association of salts of quaternary ammonium and acido complexation of ions of d-elements on the formation of the complex and double salts in the systems was presented.     

Study of crystallization process of soda lead silicate glasses by thermal and spectroscopic methods

The crystallization process of some glasses in the ternary Na₂O–SiO₂–PbO system with good chemical stability that can be used for waste inertization was studied using X-ray diffraction (XRD), infrared spectroscopy (FT-IR), differential thermal analysis (DTA) and scanning electron microscopy. The parent glasses were characterized by XRD and FT-IR, and their vitreous state was determined. DTA measurements evidenced glass transition (T _g) and crystallization temperatures (T _c). The thermal treatments were conducted at vitreous transition temperature (400 °C) and at highest effect of crystallization (650 °C). XRD evidenced the lead and sodium silicate crystalline phases in samples treated at 650 °C for 12 h. Micrometer crystallites dispersed in the glass matrices have affected the transparence of glasses and made them opaque after treatment at 650 °C. The influence of oxide quantities in compositions on the crystallization tendency was revealed. A PbO higher content than that of SiO₂ as well as lower Na₂O content decreased the tendency of crystallization.     

The role of the cation in the oxygen isotopic exchange in crystalline sulfate salt hydrates

The oxygen isotopic exchange during dehydration and decomposition of five sulfate salt hydrates (CoSO₄·6H₂O, NiSO₄·7H₂O, ZnSO₄·7H₂O, CaSO₄·2H₂O, Li₂SO₄·H₂O) was studied in detail by temperature programmed desorption mass spectrometry (TPD-MS) in a supersonic molecular beam (SMB) inlet mode. Crystals of the ¹⁸O-enriched salts were grown and the detailed desorption steps of the various gaseous products released during dehydration and decomposition of these compounds were recorded. The desorption patterns confirmed the known characteristic stepwise dehydration of these salts, where regardless of the crystalline structure and composition, in all the salts (excluding the Li and Ca sulfates) a major group of n ? 1 loosely bounded water of crystallization molecules (out of total of n molecules in the fully hydrated form) are released at adjacent temperatures in a typical low temperature range (<200 °C), while the last, most strongly bounded water molecule, consistently desorbs at relatively higher temperatures (240 < T < 440 °C). Interestingly, it is established that the oxygen isotopic exchange occurs exclusively between that latter, most strongly bound water molecule, and the salt anion. Remarkably, the results point out that the exchange process is mostly of solid-solid nature. Finally, the results point out that the probability of the isotopic exchange increases with the increment in the desorption temperature of the last dehydration step, i.e. with the bond strength in the monohydrate, between the last water molecule of crystallization and the cation.     

Phase Diagram of the Quaternary System KCl–MgCl<Subscript>2</Subscript>–NH<Subscript>4</Subscript>Cl–H<Subscript>2</Subscript>O at <Emphasis Type="Italic">t</Emphasis> = 60.00 °C and Their Application

Based on the requirement for the comprehensive exploitation and utilization of the salt lake resources magnesium chloride and potassium chloride, a new technology to produce KCl and ammonium carnallite (NH₄Cl·MgCl₂·6H₂O) by using NH₄Cl as salting-out agent to separate carnallite is proposed. The solubilities of quaternary system KCl–MgCl₂–NH₄Cl–H₂O were measured by the isothermal method at t = 60.00 °C and the corresponding phase diagram was plotted and analyzed. The analysis of this phase diagram shows that there are seven saturation points and eight regions of crystallization. These eight regions of crystallization represent salts corresponding to KCl, NH₄Cl, MgCl₂·6H₂O, (K_1?n (NH₄) _n )Cl, ((NH₄) _n K_1?n )Cl, (K_1?n (NH₄) _n )Cl·MgCl₂·6H₂O, KCl·MgCl₂·6H₂O and NH₄Cl·MgCl₂·6H₂O. According to the phase diagram analysis and calculations, ammonium carnallite (NH₄Cl·MgCl₂·6H₂O) and KCl can be obtained using carnallite as raw materials and ammonium chloride as salting-out agent at t = 60.00 °C. The new technology shows the advantages of being easy to operate and having low energy consumption. The research on this quaternary phase diagram is the foundation for reasonable development of carnallite resources and comprehensive utilization of the salt lake brines.     

Effect of molten salt synthesis temperature on TiO<Subscript>2</Subscript> and Li cycling properties

In this project, we synthesized TiO₂ compounds through the molten salt method (MSM) using Ti(IV) oxysulfate, as the Ti source. Molten salts in the ratio of 0.375 M LiNO₃:0.180 M NaNO₃:0.445 M KNO₃ were added and heated at temperatures of 145, 280, 380, and 480 °C for 2 h in air, respectively. A part of the sample prepared at 145 °C was further reheated to 850 °C for 2 h in air. X-ray diffraction studies showed that the amorphous phase was obtained when the sample was prepared at 145 °C, and polycrystalline to crystalline anatase phase was formed when heated from 280 to 850 °C, which is complementary to the results of selected area electron diffraction studies. Electrochemical properties were studied using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy at a current density of 33 mA g^?1 (0.1 C rate) and a scan rate of 0.058 mV s^?1, in the voltage range 1.0–2.8 V vs. Li. Electrochemical cycling profiles for the amorphous TiO₂ samples prepared at 145 °C showed single-phase reaction with a low reversible capacity of 65 mAh g^?1, whereas compounds prepared at 280 °C and above showed a two-phase reaction of Li-poor and Li-rich regions with a reversible capacity of 200 mAh g^?1. TiO₂ produced at 280 °C showed the lowest capacity fading and the lowest impedance value among the investigated samples.     

Ambazone salt with p-aminobenzoic acid

In this study, we obtained a novel salt of ambazone (AMB) with p-aminobenzoic acid (PABA) that exhibits improved solubility and antibacterial activity. The salt was produced by solvent-drop grinding and characterized by powder X-ray diffraction, thermal analysis and Fourier transform infrared spectroscopy. The salt nature of the new form was confirmed by infrared spectroscopy based on the characteristic vibrational band of the protonated amino group. Based on the X-ray powder diffraction data, the compound crystallizes in the triclinic P_-1 space group with the following unit cell parameters: a = 14.294 Å, b = 9.162 Å, c = 8.777 Å, α = 95.90°, β = 100.63°, γ = 91.73°. Thermal analysis reveals the thermal events and different decomposition steps of this solid form as compared to the starting compounds. Powder dissolution measurements showed solubility improvement compared with pure ambazone of 2 and 3.3 times in water and phosphate buffer, respectively. Antibacterial tests showed higher activity of the salt to Gram-negative Escherichia coli and Salmonella bacteria as compared to AMB and PABA. The study demonstrates that the pharmaceutical salt of ambazone with p-aminobenzoic acid (AMB–PABA) can be a possible alternative to ambazone in the treatment of infections with Gram-negative bacteria.     

Solubility in the diagonal sections of the 2KCl + Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> ⇆ 2KNO<Subscript>3</Subscript> + CaCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O system

Solubility data in the diagonal sections of the quaternary reciprocal 2KCl + Ca(NO₃)₂ → 2KNO₃ + CaCl₂–H₂O system at 25 and 15°C are presented. It has been shown that the quaternary system has no stable diagonal at the studied temperatures, but contains a stable pair of salts, namely, potassium nitrate and calcium chloride. The obtained data can be used to optimize the thermal and concentrational parameters of the synthesis of potassium nitrate from calcium nitrate and potassium chloride.     

Equilibrium in biphasic aqueous systems: A model for the excess gibbs energy and data for the system H2O−NaCl-1-propanol at 25°C

Liquid-liquid equilibrium data were measured for the 1-propanol-NaCl–H₂O system at 25°C. Liquid-liquid equilibrium in aqueous biphasic salt systems containing salts and alcohols or polymers was modelled using an expression for the excess Gibbs energy of the solution. The model is based on modified forms of the nonprimitive Mean Spherical Approximation, the Bromley equation, and the Flory-Huggins theory and requires three and five adjustable parameters for ternary and quaternary systems, respectively. The model accurately correlated binary water-polymer or water-alcohol vapor-liquid equilibrium data and liquidliquid equilibrium data for seven ternary and three quaternary aqueous biphasic salt systems.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Experimental study on optimized composition of mixed carbonate for phase change thermal storage in solar thermal power plant

36 kinds of mixed carbonate molten salts were prepared by mixing potassium carbonate, lithium carbonate, sodium carbonate in accordance with different proportions. The data of melting point and latent heat are measured by the analysis of DSC curves of 36 kinds of salts, which show that the majority of ternary carbonate’s melting points are close at around 400 °C. 24 kinds of eutectic molten salts were selected among 36 kinds of molten salts. With high latent heat, ternary carbonate salt has the potential to be employed for phase change thermal storage. The costs for phase change thermal storage of 24 kinds of carbonate salts are calculated. Finally, 13 kinds of ternary carbonate salts with lower cost for phase change thermal storage are recommended, where there are 6 kinds of mixed carbonates have the considerably larger latent heat of melting.     

Synthesis,characterization, and thermal study of solid-state alkaline earth metal mandelates,except beryllium and radium

Characterization, thermal stability, and thermal decomposition of alkaline earth metal mandelates, M(C₆H₅CH(OH)CO₂)₂, (M = Mg(II), Ca(II), Sr(II), and Ba(II)), were investigated employing simultaneous thermogravimetry and differential thermal analysis or differential scanning calorimetry, (TG–DTA or TG–DSC), infrared spectroscopy (FTIR), complexometry, and TG–DSC coupled to FTIR. All the compounds were obtained in the anhydrous state and the thermal decomposition occurs in three steps. The final residue up to 585 °C (Mg), 720 °C (Ca), and 945 °C (Sr) is the respective oxide MgO, CaO, and SrO. For the barium compound the final residue up to 580 °C is BaCO₃, which is stable until 950 °C and above this temperature the TG curve shows the beginning of the thermal decomposition of the barium carbonate. The results also provide information concerning the thermal behavior and identification of gaseous products evolved during the thermal decomposition of these compounds.     

On the Double Salt Formation in the Systems Rb2SeO4=ZnSeO4=H2O andCs2SeO4=ZnSeO4=H2O at 25°C

 The solubilities in the systems Rb₂SeO₄=ZnSeO₄=H₂O and Cs₂SeO₄=ZnSeO₄=H₂O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb₂Zn(SeO₄)₂ċ6H₂O and Cs₂Zn(SeO₄)₂ċ6H₂O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt).     

On the Double Salt Formation in the Systems Rb2SeO4=ZnSeO4=H2O andCs2SeO4=ZnSeO4=H2O at 25°C

Summary.  The solubilities in the systems Rb₂SeO₄=ZnSeO₄=H₂O and Cs₂SeO₄=ZnSeO₄=H₂O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb₂Zn(SeO₄)₂ċ6H₂O and Cs₂Zn(SeO₄)₂ċ6H₂O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt). Received March 14, 2000. Accepted (revised) June 5, 2000