Ionic Hydrates Research Articles

Introduction of Cyclic Structures into Phosphonium Salts As Potential Guest Substances for Ionic Clathrate Hydrates

An ionic clathrate hydrate composed of tri-n-butylbenzyl-phosphonium chloride has been investigated from the viewpoint of phase equilibrium (temperature-composition) relations in comparison with an ionic clathrate hydrate with tri-n-butyl(cyclohexylmethyl)phosphonium bromide. The highest dissociation temperature of the ionic clathrate hydrates composed of tri-n-butylbenzylphosphonium chloride and tri-n-butyl(cyclohexyl-methyl)phosphonium bromide were 274.4 ± 0.1 K and 276.0 ± 0.1 K, respectively at the atmospheric pressure. The dissociation enthalpy of tri-n-butylbenzyl-phosphonium chloride ionic clathrate hydrate was 192 ± 3 kJ·kg−1. These results allow us to suggest that controlling steric structures in the guest compounds might be one of the options for tuning the equilibrium temperatures of ionic clathrate hydrates.

Prediction of Ionic Liquids Methane Hydrate Average Depression Temperature via COSMO-RS

COSMO-RS is a tool used to pre-screen and pair ionic liquids for gas hydrate mitigation. However, the ionic liquids properties estimated from COSMO-RS lack direct connectivity to the determination of the safety margin (hydrate depression temperature) the inhibitor can alter on the hydrate phase boundary conditions. In this study, a parametric function that relates COSMO-RS estimated ionic liquid surface area and hydrogen bonding energies to the methane hydrate average depression temperature (∆T) have been presented. The statistical model in this study was developed using multiple linear regression techniques on about 90 data samples at 10 wt.% ionic liquids. The developed model in this work accurately predicts the methane hydrate average depression temperature with standard error of 3.14 and average deviation error of 0.92. Also, the ionic liquid surface area and hydrogen bonding energy contribute to hydrate inhibition by 23% and 77%, respectively. The model could predict the methane hydrate average depression temperature in the similar range as reported in literature. The findings in this work provide a simple and fast method of pre-screening and developing efficient ionic liquids gas hydrate inhibitors for use in the oil and gas industry.

Nucleation-promoting effect of mixed Zn and ZnO particles on tetra-n-butylammonium bromide hydrate

Tetra-n-butylammonium bromide (TBAB) hydrate is an ionic semi-clathrate hydrate, and it can be used as an energy-storage and gas-separation medium. Nucleation of TBAB hydrate is unlikely to occur and this characteristic causes problems in the refrigeration system due to the need for excessive cooling and delays in gas separation due to the slow formation. Therefore, a technique for rapid formation of TBAB hydrate is required. In a previous study, it was found that addition of mixed and ground Zn and ZnO particles (Zn–ZnO) to TBAB aqueous solution significantly promoted nucleation of TBAB hydrate. Since the nucleation of TBAB hydrates was effectively promoted by the very simple addition of Zn–ZnO, this technique can be easily applied to conventional systems. However, the nucleation-promoting mechanism have not been clarified. The clarification of the nucleation-promoting effect of Zn–ZnO on TBAB hydrates is important to elucidate the nucleation-promoting mechanism of clathrate hydrates by the addition of substances. Therefore, the objective of the present study was to investigate the nucleation-promoting mechanism of Zn–ZnO on TBAB hydrate. Experimental results showed that immersion of Zn–ZnO in TBAB aqueous solution reduced the nucleation-promoting effect, but a decrease in the nucleation-promoting effect was not observed when Zn–ZnO was immersed in water. Microscopy observation confirmed that immersion of Zn–ZnO in TBAB aqueous solution had little effect on its surface morphology, but X-ray diffraction and X-ray photoelectron spectroscopy indicated formation of solid TBAB on Zn–ZnO. Zn–ZnO did not show a significant nucleation-promoting effect on tetrahydrofuran hydrate, which is a non-ionic clathrate hydrate. This suggest that Zn–ZnO has properties that attract tetra-n-butylammonium and Br ions, and that the proximity of these ions may promote formation of TBAB hydrate. It was also suggested that the mechanism of nucleation promotion by the addition of substances is different for ionic clathrate hydrates and non-ionic clathrate hydrates.

Fluoride-incorporated ionic clathrate hydrates

Fluoride-incorporated ionic clathrate hydrates

Readily regenerable amine-free CO2 sorbent based on a solid-supported carboxylate ionic liquid

Accumulation of anthropogenic CO2 is undoubtedly the major cause of global warming. In addition to reducing emissions, minimising the threatening effects of climate change in the near future might also require the capture of enormous amounts of CO2 from point sources or from the atmosphere. In this regard, the development of novel affordable and energetically attainable capture technologies is greatly needed. In this work, we report rapid and greatly facilitated CO2 desorption for amine-free carboxylate ionic liquid hydrates as compared to a benchmark amine-based sorbent. Complete regeneration was achieved at moderate temperature (60 °C) over short capture-release cycles using model flue gas on a silica-supported tetrabutylphosphonium acetate ionic liquid hydrate (IL/SiO2), whereas the polyethyleneimine counterpart (PEI/SiO2) only recovered half its capacity after the first cycle in a rather sluggish release process under the same conditions. The IL/SiO2 sorbent achieved a slightly superior working CO2 capacity than PEI/SiO2. The easier regeneration of carboxylate ionic liquid hydrates, which behave as chemical CO2 sorbents leading to bicarbonate in a 1:1 stoichiometry, is due to their relatively low sorption enthalpies (≈40 kJ mol−1). The faster and more efficient desorption from IL/SiO2 fits a first-order kinetic model (k = 0.73 min−1), whereas a more complex process was observed for PEI/SiO2 (pseudo-first order initially, k = 0.11 min−1, pseudo-zero order at later stages). The remarkably low regeneration temperature, the absence of amines and the non-volatility of the IL sorbent are favourable assets to minimise gaseous stream contamination. Importantly, regeneration heats —a crucial parameter for practical application— are advantageous for IL/SiO2 (4.3 kJ g (CO2)−1) vs. PEI/SiO2, and fall within the range of typical amine sorbents indicating a remarkable performance at this proof-of-concept stage. Further structural design will enhance the viability of amine-free ionic liquid hydrates for carbon capture technologies.

Measurements of the Dissociation Heats of Tetrabutylammonium Acetate and Tetrabutylammonium Hydroxide Ionic Semiclathrate Hydrates

Measurements of the Dissociation Heats of Tetrabutylammonium Acetate and Tetrabutylammonium Hydroxide Ionic Semiclathrate Hydrates

Effect of introducing a cyclobutylmethyl group into an onium cation on the thermodynamic properties of ionic clathrate hydrates

Cyclic hydrocarbon groups in phosphonium cations can be one of the options for tuning the equilibrium temperature of ionic clathrate hydrates.

Rotational-electric principles of RNA/DNA and viability

<abstract> <p>Photographic investigations of rising bubbles in seawater revealed that each bubble may conduct a single or bi-spiraling motion, which resemble architecture of RNA or DNA respectively. The rotational motion results from acceleration of ionic hydrates, which are separated to anionic and cationic domains at the upper and bottom curvatures of the bubble. Afterwards, rotational motion undergoes further acceleration in the bubble upper vortex, followed by deceleration at the vortex tip. During that phase, the spiraling motion cause significant friction that result in polarization of electronegative atoms of H, C, N, O and P. These may be simultaneously arranged around a whirling cationic strands and form phosphate groups, ribose and nitrogen bases equipped with H<sub>2</sub> and H<sub>3</sub> rotors. It is hypothesized that such hydrogen rotors may operate as generators of electrons, which may be detached from valence shells of electropositive atoms. Then, electrons may flow via nitrogen bases and deoxyribose or ribose to phosphate groups. Next, the negatively charged edges of phosphate groups may attract cationic hydrates and energize their rotational motion in the grooves, then causing also its spiraling projection outward. That may be responsible for replication of nucleotides and its arrangement along the cationic flow into RNA or DNA polymers, in the same manner as originally produced by rising bubbles. Moreover, it points that hydrogen rotors may generate energy needed for viability as well as interact with all physical and chemical fields.</p> </abstract>

Thermophysical Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylphosphonium Malonate

Thermophysical Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylphosphonium Malonate

Machine learning-aided atomic structure identification of interfacial ionic hydrates from AFM images.

Relevant to broad applied fields and natural processes, interfacial ionic hydrates have been widely studied by using ultrahigh-resolution atomic force microscopy (AFM). However, the complex relationship between the AFM signal and the investigated system makes it difficult to determine the atomic structure of such a complex system from AFM images alone. Using machine learning, we achieved precise identification of the atomic structures of interfacial water/ionic hydrates based on AFM images, including the position of each atom and the orientations of water molecules. Furthermore, it was found that structure prediction of ionic hydrates can be achieved cost-effectively by transfer learning using neural network trained with easily available interfacial water data. Thus, this work provides an efficient and economical methodology that not only opens up avenues to determine atomic structures of more complex systems from AFM images, but may also help to interpret other scientific studies involving sophisticated experimental results.

Synthesis and thermophysical properties of Tetrabutylammonium picolinate hydrate as an energy storage phase change material for cold chain

Ionic semiclathrate hydrates, the water-based phase change materials (PCMs) have potential for thermal energy storage media. There are a number of hydrates, reported in the literature, which are suitable as PCMs for air conditioning system of the required temperature range 10–15 °C. In this study, Tetrabutylammonium picolinate hydrate (TBAPi hydrate) was newly synthesized as a PCM for the cold chain, which has a lower phase equilibrium temperature than the previously reported hydrates. Thermophysical properties of TBAPi hydrate were experimentally measured. The hydrate dissociation heat was determined using a differential scanning calorimeter (DSC). The phase equilibrium temperature was measured by visually observing system with a CMOS camera and microscope. Also, the cycling test was conducted to confirm the long-term stability of thermophysical properties. The largest dissociation heat was 157.7 ± 4.9 kJ･kg−1 at a mass fraction of TBAPi aqueous solution, wTBAPi of 0.37. The highest phase equilibrium temperature of TBAPi hydrate was 5.5 °C at 0.34 ≤ wTBAPi ≤ 0.36. These thermophysical properties did not change even after 200 cycles of hydrate formation and dissociation. Based on the experimental results, TBAPi hydrate can be applied to the transport and storage of vaccines, blood packs, and perishable foods.

(Digital Presentation) Phosphonium Salts As Potential Guest Substances for Ionic Semiclathrate Hydrates

Semiclathrate hydrates (SCHs) are ionic crystalline compounds consisting of an organic guest cation in several cages formed by hydrogen bonding of water1. SCHs have recently been considered for application to air conditioning systems and refrigeration systems since desirable equilibrium temperatures and the considerable decomposition enthalpies are observed in the solid-liquid equillibria2. Ionic guest substances of SCHs include quaternary onium compounds such as tetrabutylammonium2 and tetrabutylphosphonium based salts3. We report here the preparation and thermodynamic properties of SCHs based on quaternary phosphonium bromides containing an unsaturated carbon-carbon double bond, as shown in Fig. 1, in comparison with the conventional saturated phosphonium salt, such as tetrabutylphosphonium bromide (P4444-Br).The unsaturated phosphonium bromides (P444(1All)-Br and P444(2All)-Br) were synthesized by quaternarization reaction of tributylphosphine with alkenyl bromides in a nitrogen atmosphere. The aqueous solutions were prepared from 5 to 50 w/w %. After thorough stirring, the aqueous solutions were cooled in a freezer to form SCHs. The SCHs were immersed into a thermostatic bath at 268 K for at least 1 day. The temperature in the thermostatic bath was raised from 268 K at a rate of 0.1 K/step (1 step: more than 5 h). The equilibrium temperatures were defined as the temperature at which SCHs were completely dissolved. The ionic crystal structure was analyzed by a powder X-ray diffraction (PXRD) technique, the dissociation enthalpy was measured by a micro differential scanning calorimeter (μDSC).Fig. 2 depicts the solid-liquid phase equilibrium diagram representing the phase equilibrium temperatures of SCHs. The equilibrium temperature of P444(1All)-Br SCH was higher than P4444-Br SCH. These results might be due to the steric effect of alkenyl group. As shown in Fig. 3, the ionic crystal structure of both P444(1All)-Br and P444(All)-Br SCHs were orthorhombic. The dissociation enthalpy of P444(1All)-Br SCHs and P444(2All)-Br SCHs were 188 J/g and 199 J/g, respectively. The unsaturated phosphonium bromides would be regarded as potential guest substances used for latent heat storage materials in air conditioning systems.References M. Oshima, et al, J. Chem. Thermodynamics, 90, 277 (2015).H. Oyama, et al, Fluid Phase Equilibria, 234, 131 (2005).J. Shimada, et al, Chem. Eng. Sci., 236, 116514 (2021). Figure 1

Measurements of phase equilibrium temperature and dissociation heat of tetrabutylphosphonium glutarate ionic semiclathrate hydrate

Thermophysical properties such as phase equilibrium temperature and dissociation heat are important to determine the performance of phase change materials targeting thermal energy storage. The phase equilibrium temperature and dissociation heat of tetrabutylphosphoniumglutarate ionic semiclathrate hydrate were measured in this study. The highest phase equilibrium temperature of tetrabutylphosphoniumglutarate hydrate was experimentally determined 287.4 K at the mass fraction 0.347 and 0.357. The largest dissociation heat was 193.3 ± 1.6 kJ/kg at the mass fraction 0.357. The measurement results in this work show that the dissociation heat can be utilized in the suitable temperature range targeting general air conditioning and data center.

Ionic Clathrate Hydrates of Tetraalkylammonium/phosphonium Salts: Structures, Properties, Some Applications, and Perspectives

Ionic clathrate hydrates (ICHs) belong to one of the groups of a wide class of clathrate hydrates. In the crystal structures of ICHs, cation–anion pairs of guest molecules, typically tetraalkylammonium/phosphonium salts, are included into the host framework of hydrogen-bonded water molecules. Because of their suitable phase change temperature and latent heat, ICHs are considered as promising phase change materials for application in cold energy storage and transportation. The presence of vacant cavities in ICHs structures, which can incorporate small gas molecules such as, for example, H2, CH4, CO2, N2, H2S, determines the possibility of their use for the separation and storage of gases. The formation of these double ICHs occurs under much milder pressure and temperature conditions compared to the pure gas hydrates of the same gases. Studying of the structural characteristics and thermophysical properties of ICHs and double ICHs with gases is the necessary basis for their effective applications in different practical ends. This work reviews information related to the new details and features of the structures of ICHs and double ICHs with gases revealed over the last decade or a little more as well as some thermophysical data such as hydrate numbers, temperatures and enthalpies of dissociation. This review focuses only on ICHs of tetrabutyl-, tetraisoamylammonium (TBA, TiAA), and tetrabutylphosphonium (TBP) salts, which are the most common representatives of this class of compounds. One of the sections is devoted to ICHs of TBA and TiAA with polymeric anions such as cross-linked polyacrylates. The purpose of the present paper is to review the studies that have been relatively little addressed in previous works.

Synthesis and evaluation of green phase change materials for efficient air conditioning by tetrabutylphosphonium phosphate ionic semiclathrate hydrate

A tetrabutylammonium bromide (TBAB) hydrate is the only ionic semiclathrate hydrate that has been commercialized as a medium for efficient thermal energy storage targeting general air conditioning. However, TBAB is an environmental pollutant, while liquid water and ice that have been widely used as conventional media, also have difficulty in increasing the thermal energy storage density as well as the coefficient of performance (COP) of a refrigerator to form solid. In this study, a tetrabutylphosphonium phosphate ((TBP)3PO4) hydrate was proposed as an alternative green medium. The dissociation heat and the phase equilibrium temperature, which were both crucial factors to evaluate the thermal energy storage density, and COP was experimentally determined. It was found that the maximum dissociation heat was 154.1 ± 2.0 kJ･kg−1 at the mass fraction of 0.309. The highest phase equilibrium temperature was 10.0 °C at the mass fractions of 0.290, 0.299, and 0.309. The thermal energy storage density of (TBP)3PO4 hydrates was 3.7 times larger than that of water. (TBP)3PO4 hydrates increased the COP of a refrigerator to form solid by 42% as compared with ice, indicating the potential size-reduction of conventional devices with the decrease in the power consumption of a refrigerator. The effective balance between environmental protection and the system performance through (TBP)3PO4 hydrates was also discussed.

Bubble mediated polymerization of RNA and DNA

<abstract> <p>Research dedicated to trace rotational motion of bubbles in saline water revealed that these may generate either single cationic or cationic/anionic motions, including spliced double helix flow. In all cases, the aggregated ionic flows propagate in spiraling as well as rotational manner. However, if bi-ionic or double helix motion is generated, the flow is oppositely directed and has opposite electric charges. Next, the assembled flow is forced to pirouette within the bubble vortex. During that processing the narrowing of spiraling flow takes place and result in increase of revolutions to even millions per second. As a result, a significant friction is induced between revolving ionic hydrates allowing continuous detachment of electrons from covalent atomic shells of electropositive elements. Then, free electrons may be attracted by electronegative elements that are dissolved in seawater. Afterwards, that negatively charged elements may undergo electrical condensation around cationic centers of revolutions. That explain a unique mechanism which operates when negatively charged phosphate compounds and pentagonal blocks found in RNA and DNA as ribose as well as pentagonal rings in nitrogenous bases A and G are being winded. The compensative anionic flow and revolutions may conduct winding of hexagonal blocks found in nitrogenous bases A, G and C, T or U. These assume to gather more positive charge needed to bridge negatively charged sugar molecules in nucleic acids. Thus, the continuity in generation of electronegative compounds and spiral manner of arranging them within the sub-bubble vortices should be regarded as a mechanism responsible for precise, rotational-electric polymerization of elongated macromolecules of RNA/DNA architecture. Reported research refers mainly to physical processes activated by rising bubbles thus should be confronted with other experimental methods used in genetics, microbiology and chemistry.</p> </abstract>

Synthesis and thermophysical property evaluation of ionic semiclathrate hydrate formed with tetrabutylphosphonium glycine as a chilling temperature phase change material

Ionic semiclathrate hydrate, which is formed under atmospheric pressure with sustainably safe properties, has a potential for solid-liquid phase change materials(PCMs). In this study, the thermophysical property of tetrabutylphosphonium glycine(TBPGly) hydrate containing no halogen guest compound, glycine (aminoacetic acid), was investigated to evaluate the availability as an eco-efficient thermal energy storage medium. The phase equilibrium temperature was obtained through visual observation method. The heat flow rate curve behavior and dissociation heat were measured via differential scanning calorimetry(DSC). In the dissociation process, a single hydrate dissociation peak emerged, indicating TBPGly hydrate has one type of crystallographic structure. The concentration dependency of the TBPGly aqueous solution on the equilibrium temperature and the dissociation heat was confirmed. The highest equilibrium temperature of 5.8 °C was confirmed at the fraction range wTBPGly =0.368 or xTBPGly =0.0306, and the largest dissociation heat was 177.7 kJ·kg−1 at the fraction range wTBPGly =0.377or xTBPGly =0.0318. The estimated hydration number in the congruent composition was found to be in 31.2 to 32.5. In addition, based on the measured physical property, the optimum operating temperature and volume fraction of TBPGly hydrate was evaluated to determine the concentration for the practical cooling system. These data revealed TBPGly hydrate is available as a solid or slurry PCM under the operating temperature range 2 °C to 5.8 °C. The experimental data as well as the illustrative calculations contribute to accelerate the expansion in the application range, and provide the prospect in selecting the suitable composition toward the actual hydrate-based cooling system.

Visual Observation of Tetra-n-butylammonium Bromide Ionic Semiclathrate Hydrate Formation: A Laboratory Experiment

A laboratory experiment was performed using tetra-n-butylammonium bromide (TBAB) ionic semiclathrate hydrate, a crystalline compound. Ionic semiclathrate hydrates have unique properties, and hence, novel technologies utilizing the ionic semiclathrate hydrates have been proposed to date. Thus, students could learn fundamentals of functional materials through ionic semiclathrate hydrates from chemical and engineering points of view. In the experiment, formation of the TBAB hydrate was observed at fixed temperature and under atmospheric pressure by using TBAB aqueous solutions having TBAB mass fractions of wTBAB = 0.10, 0.20, 0.30, 0.40, and 0.50. There are no serious safety hazards. In addition, the experiment can be performed using inexpensive equipment and materials. The amount of the formed TBAB hydrate and its crystal morphology depended on the concentration of the aqueous solution. The students needed to submit a laboratory report describing fundamentals of the ionic semiclathrate hydrates, a relationship between equilibrium conditions and the amount of the formed TBAB hydrate, and an adequate crystal morphology of the TBAB hydrate crystals as a thermal storage material. Most students understood the experiment well, and the average score of the reports was approximately 80%.

The transition from salt-in-water to water-in-salt nanostructures in water solutions of organic ionic liquids relevant for biological applications.

The nanostructure in water solutions of three organic ionic liquids relevant for biological applications has been studied by molecular dynamics simulations based on empirical force fields. The three compounds consisted of two different triethylammonium salts, known to affect the fibrillation kinetics of Aβ peptides, and a phosphonium dication, which has been shown to possess a marked bactericidal activity. The structure of solutions spanning a wide concentration range (from 25 to 75 wt%) has been analysed by computing several combinations of partial structure factors, measuring the fluctuation of the ion and water distribution in space. At moderate salt concentration, the results reflect the formation in water of salt-rich domains of nanometric size. With salt concentration increasing beyond 50 wt%, the system enters the so-called water-in-salt regime, in which the aggregation properties of water become relevant, giving origin to water-rich domains in the nearly uniform salt environment. The persistence over a wide concentration range of nearly integer (∼6; ∼4) water-ion coordination numbers suggests the formation of stoichiometric liquid ionic hydrates.

Kinetics and Mechanism of the Dehydration of Calcium Sulfate Dihydrate: A Comprehensive Approach for Studying the Dehydration of Ionic Hydrates under Controlled Temperature and Water Vapor Pressure

We studied the kinetics and mechanism of the dehydration reaction of calcium sulfate dihydrate to hemihydrate under controlled temperature and water vapor partial pressure. From kinetic and reactio...