crystalline hydrate
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Author(s):  
N.K. Dosmukhamedov ◽  
◽  
E.E. Zholdasbay ◽  
V.A. Kaplan ◽  
G.S. Daruesh ◽  
...  

A laboratory setup has been developed to study the regularities of crystallization of aluminium chloride hexahydrate from hydrochloric acid solutions. The influence of the AlCl3 content in the initial solution, the consumption of gaseous HCl, and the behavior of impurities on the crystallization of AlCl3·6H2O from aluminium chloride solutions of leaching cinder obtained as a result of chlorinating ash burning from thermal power plants in Kazakhstan have been studied. The behavior of impurity metals in the process of crystallization of aluminium chloride solution has been studied, and their distribution between the products of the crystallization process has been established. It is shown that aluminium chloride content in the solution decreases with an increase in the consumption of hydrochloric acid. It was found that under the conditions of crystallization of AlCl3·6H2O, all impurities, except for barium, pass by 98% into the mother liquor. To reduce barium and other impurities in the obtained crystals of AlCl3·6H2O, it is proposed to carry out multiple washing of the crystals with hydrochloric acid (32% HCl). It has been shown that a decrease in the acidity of the washing solution from pH = 10 to pH = 5.5 ensures the isolation of ACH crystals with a minimum content of impurity metals, ppm: 3-5 Ca; 3-6 Fe; 1-3 Mg; 0.1-0.5 Ti; 1-3 Na; 20-30 P2O5. The moisture content of the obtained crystals is 4-5%; the particle size is 400-900 microns. As a result of mathematical processing, regression equations were constructed that adequately predict aluminium chloride content in the solution and its extraction into crystalline hydrate, depending on the consumption of hydrochloric acid. The optimal parameters of the crystallization process have been established: Т = 60 ºС, HCl concentration in the solution - 26-30%, HCl gas consumption = 0.5 l/min, duration 1 hour.


2021 ◽  
Vol 66 (12) ◽  
pp. 1779-1784
Author(s):  
T. L. Simonenko ◽  
V. A. Bocharova ◽  
N. P. Simonenko ◽  
E. P. Simonenko ◽  
V. G. Sevastyanov ◽  
...  

Abstract—The synthesis of NiMoO4 hierarchical nanostructures using the hydrothermal method has been studied. The decomposition of NiMoO4·xH2O crystalline hydrate formed during the synthesis has been studied using synchronous thermal analysis upon heating in a stream of air and argon. According to X-ray diffraction as well as scanning and transmission electron microscopies, the proposed conditions allow one to synthesize single-phase nanosized (average CSR size of about 25 ± 2 nm) nickel(II) molybdate, which has a spinel-type monoclinic structure (space group C2/m) without impurity inclusions.


Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1027
Author(s):  
Yuriy G. Denisenko ◽  
Maxim S. Molokeev ◽  
Aleksandr S. Oreshonkov ◽  
Alexander S. Krylov ◽  
Aleksandr S. Aleksandrovsky ◽  
...  

Crystalline hydrate of double cesium europium sulfate [CsEu(H2O)3(SO4)2]·H2O was synthesized by the crystallization from an aqueous solution containing equimolar amounts of 1Cs+:1Eu3+:2SO42− ions. Anhydrous salt CsEu(SO4)2 was formed as a result of the thermal dehydration of the crystallohydrate. The unusual effects observed during the thermal dehydration were attributed to the specific coordination of water molecules in the [CsEu(H2O)3(SO4)2]·H2O structure. The crystal structure of [CsEu(H2O)3(SO4)2]·H2O was determined by a single crystal X-ray diffraction analysis, and the crystal structure of CsEu(SO4)2 was obtained by the Rietveld method. [CsEu(H2O)3(SO4)2]·H2O crystallizes in the monoclinic system, space group P21/c (a = 6.5574(1) Å, b = 19.0733(3) Å, c = 8.8364(2) Å, β = 93.931(1)°, V = 1102.58(3) Å3). The anhydrous sulfate CsEu(SO4)2 formed as a result of the thermal destruction crystallizes in the monoclinic system, space group C2/c (a = 14.327(1) Å, b = 5.3838(4) Å, c = 9.5104(6) Å, β = 101.979(3) °, V = 717.58(9) Å3). The vibration properties of the compounds are fully consistent with the structural models and are mainly determined by the deformation of non-rigid structural elements, such as H2O and SO42−. As shown by the diffused reflection spectra measurements and DFT calculations, the structural transformation from [CsEu(H2O)3(SO4)2]·H2O to CsEu(SO4)2 induced a significant band gap reduction. A noticeable difference of the luminescence spectra between cesium europium sulfate and cesium europium sulfate hydrate is detected and explained by the variation of the extent of local symmetry violation at the crystallographic sites occupied by Eu3+ ions, namely, by the increase in inversion asymmetry in [CsEu(H2O)3(SO4)2]·H2O and the increase in mirror asymmetry in CsEu(SO4)2. The chemical shift of the 5D0 energy level in cesium europium sulfate hydrate, with respect to cesium europium sulfate, is associated with the presence of H2O molecules in the vicinity of Eu3+ ion.


2021 ◽  
Vol 1043 ◽  
pp. 109-114
Author(s):  
Violetta Bratoshevskaya

The relationship between the elastic-plastic properties of concrete and its ability to resist the external loads and internal stresses effects arising under the influence of aggressive environmental factors has been studied. In concrete, micro-and macrocracks are filled with air and a liquid phase migrates with periodic environmental temperature, therefore, humidity changes. When the structure is compacted by crystalline hydrate neoplasms arising from supersaturated solutions, their surface increases and, correspondingly the part of water hydraulically bound to it also increases which changes its mobility with temperature. This entire system of interphase and single-phase structural bonds and interactions in concrete changes with fluctuations in humidity, cooling, and especially during phase transitions during freezing. The research found that the introduction of hydraulic additives into the binder, which carry a negative charge on their surface, leads to a charge change of the material structure pore space. The penetration kinetics of aggressive environments, adsorption interaction with the cement stone capillaries surface has been studied.


Author(s):  
Rana Sanii ◽  
Ewa Patyk-Kaźmierczak ◽  
Carol Hua ◽  
Shaza Darwish ◽  
Tony Pham ◽  
...  

Author(s):  
Igor V. Polyakov ◽  
Mikhail V. Barannikov ◽  
Ekaterina A. Stepanova

The effect of a complex additive containing superplasticizer C-3 on the properties of heavy concrete has been investigated. The efficiency of the plasticizing action of the specified additive at the stage of preparation of the concrete mixture and subsequent molding of concrete products has been revealed. It is proved that at the stage of concrete hardening, the investigated additive promotes to the formation of a more homogeneous colloidal-crystalline structure and the formation of dense crystalline hydrate complexes of cement stone by the time of completion of concrete hardening. The objects of investigation were samples of grade B22.5 concrete without additives; containing a monoadditive - superplasticizer S-3; containing the complex additive. When designing the composition of additives for heavy concrete, we proceeded from the fundamental provisions of construction science that the complexity of the action of additives lies in the optimal combination of two main opposite processes in time and volume of the concrete matrix. The use of the caprolactam oligomer synthesized in the course of this investigation makes it possible to solve the problem of involving concentrated wastes of caprolactam production in the production turnover. The obtained caprolactam oligomers can be used in construction as plasticizers of concrete mixtures, as inhibitors of corrosion of steel reinforcement in the production of reinforced concrete products. Water-soluble oligomers of caprolactam, which reduce the time of dissolution of the superplasticizer C-3 and the dispersion of low-temperature catalyst in the volume of the concrete mixture being mixed, were synthesized. It was found that in the presence of the oligomer caprolactam in an amount of 10 to 20% of the mass. the dissolution rate of S-3 superplasticizer in water at a temperature of 20-21 °C increases by 2.0-2.2 times. This contributes to a better mixing of the components of the concrete mixture, primarily to improve the dispersion of the complex additive in the volume of the concrete mixture. The caprolactam oligomer used in this research work is an effective water-soluble wetting agent for the surface of particles of cement, sand, and crushed stone, which is very important for activating hydration and sorption processes during mixing of a concrete mixture. The increased wetting properties of the caprolactam oligomer are characterized by a wetting angle of 19.6 °.


2021 ◽  
Author(s):  
Dinesh J. Paymode ◽  
Natarajan Vasudevan ◽  
Saeed Ahmad ◽  
Appasaheb L. Kadam ◽  
Flavio S. P. Cardoso ◽  
...  

<p>A two-step synthesis of molnupiravir (<b>1</b>) is presented. This work focuses on the development of practical reaction and purification conditions toward a manufacturing route. The sequence commences from highly available cytidine (<b>2</b>), and molnupiravir is formed through direct hydroxamination of the cytosine ring and esterification of the sugar’s primary alcohol without use of protecting or activating groups. A highly crystalline hydrate of <i>N</i>-hydroxycytidine (<b>3</b>) resulted in an easily purified intermediate, and a practical, off-the-shelf enzyme was selected for the acylation. The yield was increased through a chemically-promoted, selective ester cleavage which converted a by-product, molnupiravir isobutyryl oxime ester (<b>4</b>), into the final API. Both reactions proceed in >90% assay yield and crystallization procedures are used to afford intermediate and active pharmaceutical ingredient in purities above 99% with an overall yield of 60%. Excellent throughput and sustainability is achieved by limiting the total concentration to 7 volumes of solvent in the course of the two reactions with an overall PMI of 41 including work-up and isolation. Environmentally friendly solvents, water and 2-methyl tetrahydrofuran, enhance sustainability of the operation. </p>


2021 ◽  
Author(s):  
Dinesh J. Paymode ◽  
Natarajan Vasudevan ◽  
Saeed Ahmad ◽  
Appasaheb L. Kadam ◽  
Flavio S. P. Cardoso ◽  
...  

<p>A two-step synthesis of molnupiravir (<b>1</b>) is presented. This work focuses on the development of practical reaction and purification conditions toward a manufacturing route. The sequence commences from highly available cytidine (<b>2</b>), and molnupiravir is formed through direct hydroxamination of the cytosine ring and esterification of the sugar’s primary alcohol without use of protecting or activating groups. A highly crystalline hydrate of <i>N</i>-hydroxycytidine (<b>3</b>) resulted in an easily purified intermediate, and a practical, off-the-shelf enzyme was selected for the acylation. The yield was increased through a chemically-promoted, selective ester cleavage which converted a by-product, molnupiravir isobutyryl oxime ester (<b>4</b>), into the final API. Both reactions proceed in >90% assay yield and crystallization procedures are used to afford intermediate and active pharmaceutical ingredient in purities above 99% with an overall yield of 60%. Excellent throughput and sustainability is achieved by limiting the total concentration to 7 volumes of solvent in the course of the two reactions with an overall PMI of 41 including work-up and isolation. Environmentally friendly solvents, water and 2-methyl tetrahydrofuran, enhance sustainability of the operation. </p>


The chapter is devoted to structure and properties of composite adsorbents ‘salt inside porous matrix'. Characteristics of adsorbents ‘salt inside porous matrix', such as ‘zeolite – crystalline hydrate', ‘vermiculite – crystalline hydrate', ‘silica gel – crystalline hydrate' were analysed. Main advantages of composite adsorbents are shown to be higher adsorptive capacity and lower regeneration temperature as compared with host matrix. Adsorptive capacities of composite materials are shown to be significantly enhanced by introduction of salts in host matrix such as zeolite, vermiculite, or silica gel. Water uptake by composite adsorbent is shown to be increased by rising the salt content in it. The drawback of most of existing impregnation technologies is shown to be impossibility of obtaining composite with salt content more than 40 – 60% along with complexity. Sol gel method is shown to be an alternative for conventional impregnation methods. Properties of adsorbents ‘silica gel – sodium sulphate' synthesized according to sol gel method developed by authors were considered. The composite ‘silica gel – sodium sulphate' composition and structure were studied by IR-spectroscopy and wide-angle x-ray scattering. Adsorptive properties of crystalline Na2SO4 when allocated in silicon oxygen matrix are shown to result from dispersion up to nanoscale. Adsorptive capacities and heat of adsorption of composites ‘silica gel – sodium sulphate' and ‘silica gel – sodium acetate' surpass almost by 30% the value calculated from the linear superposition of the sorption capacities of the sorbent and massive salt. Their adsorption properties are shown to be not a linear combination of properties of silica gel and salt. The formation of a unique structure promoting an increase in the rate of reaction between crystalline hydrates and water vapor in the developed pores of the silicon-oxygen matrix is confirmed. It leads to increasing the heat of adsorption and the heat energy storage density. Strong difference of water sorption kinetic curves of composite ‘silica gel – sodium sulphate' and massive sodium sulphate is revealed. The correlation of their composition, structure, water adsorption kinetic, and operating characteristic as heat storage material is stated.


The chapter is focused on state of the art of materials for adsorptive heat energy conversion basic principles for substantiation of working pair choice. Types of heat storage materials based on heat storage mechanism were compared. Sensible heat mechanism of thermal energy is based on increasing the temperature of the material. Phase-change mechanism of heat energy storage concerns with alternating reversible processes of phase-changing. As a rule, they are mainly melting-crystallization. Thermo-chemical heat energy storage mechanism is based on reversible chemical reactions. Limitations of conventional sensible heat storage are shown to lowest density of heat energy storage determined by sensible heat of materials, which led to large mass storage units and additional needs of large areas and building volumes, calculated according to heat storage density, constant changing the temperature when discharged, the need for a large overheating of heat storage media. The main defects of phase-change materials are instability of properties of heat-accumulating substances in multiple cycles of crystallization – melting, degradation in time, corrosion activity, the need for developed surfaces of heat exchange and environmental danger. Commercilisation of thermal chemical storage materials is strongly limited by high operating temperatures of thermal chemical storage materials, which are unacceptable for systems of district heating and decentralized heat supply due to sanitary regulations, impropriety for multifold cycling because of irreversibility of a wide range of chemical reactions. Perspective of adsorptive heat energy storage and conversion is shown. Interval of operating temperatures and heat storage density of conventional adsorptive materials are shown to be intermediate between phase-change and thermal chemical heat storage materials. Properties of probable adsorptive heat storage materials were analysed according with literary data. Low adsorptive capacity of conventional adsorbents results in low heat of adsorption and heat energy storage density. Salts forming crystalline hydrate occur to exhibit rather high energy storage density of 1.9–2.7 GJ/m3 of crystalline hydrate, but their application is strongly inhibited not only by physical and chemical instability along with the corrosive activity of these salts at high temperatures, but instability in multifold cycling, degradation in time, and an underdeveloped heat exchange surface. As engineering solution, modification of conventional adsorbents with salt can be considered. Composites ‘salt inside porous matrix' is shown to be promising alternative to conventional adsorbents. Main advantages of these materials are low regeneration temperature and high adsorptive capacity. Crucial impediments of industrial introduction of composite adsorbents ‘salt inside porous matrix' is shown to be complex technology of their production based on rather expensive dry and wet impregnation of porous media by crystalline hydrate solutions. As an alternative, sol gel method for obtaining composite adsorbents ‘silica gel – crystalline hydrate' developed by authors is suggested. The adsorption properties of the obtained composite adsorbents ‘silica gel – sodium sulphate' and ‘silica gel – sodium acetate' are shown to be non-linear combinations of characteristics of silica gel and massive salt. The key distinction of kinetics of adsorption of water vapor with massive salts and composites obtained with sol gel method is shown to be difference limitative stage of process. The adsorption of water with massive crystalline hydrates is shown to be complicated by kinetic limitations. For composite adsorbents limiting stage is water transport through the pore system. Composites ‘slilica gel – crystalline hydrate' are shown to be a promising material for adsorptive heat energy storage and conversion.


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