Tetrabutylammonium Bromide Research Articles

The Adhesion Strength of Semi-Clathrate Hydrate to Different Solid Surfaces

The adhesion between a hydrate and a pipe wall is the main cause of hydrate deposition and blockage. In this study, the adhesion strength of semi-clathrate hydrate (tetrabutylammonium bromide hydrate) to four kinds of solid surfaces (E235B carbon steel, E355CC low alloy steel, SUS304 stainless steel, and polytetrafluoroethylene) was measured. This investigation reveals that the adhesion strength of the hydrate to a solid surface is negatively correlated with the wettability of the solid surface, which suggests that hydrophobic materials effectively reduced the hydrate adhesion to the pipe wall. The surface roughness showed different effects on the adhesion of the hydrate to hydrophilic or hydrophobic surfaces. To be specific, when the surface roughness increased from 3.2 µm to 12.5 µm, the hydrate adhesion strength to the hydrophilic surface of SUS304 increased by 123.6%, whereas the hydrate adhesion strength to the hydrophobic surface of polytetrafluoroethylene only increased by 21.5%. This study shows that low wettability and low surface roughness effectively reduce the critical rate required to remove hydrate deposition, which achieves the self-removal of hydrates. At the same time, it was found that the adhesion strength of the hydrate to surfaces increases with increasing subcooling. This investigation holds significant theoretical implications for designing self-cleaning surfaces for oil and gas pipes.

Stabilization of Iron Gall Ink Damaged Paper with Nanosized Magnesium Hydroxide and Antioxidants

ABSTRACT Ink-paper historical documents, which are an important part of cultural heritage, can be damaged by various materials on the outside and the inside of the paper. Cotton fiber sheets treated with iron gall ink and then treated with stabilization materials were studied. Nanosized Mg(OH)2 was used as a deacidification material and potassium bromide, tetrabutylammonium bromide, or propyl gallate as antioxidant materials were investigated as a stabilization system for iron gall ink-damaged paper. All samples were artificially aged in the air for 150 h at 65 °C in a UV/moisture chamber or 500 h at 90 °C. The pH and alkaline reserve (AR) measurements, monitoring of color change, and scanning electron microscopy analysis data confirm that the aging effect is more destructive to the iron gall inked paper. The experiment results show that using alkaline materials with antioxidants, such as nano-Mg(OH)2 and propyl gallate, positively affects color changes of ink-damaged paper. Treatment with a stabilization system such as nanosized Mg(OH)2, a binder hydroxypropyl cellulose (Klucel), and an antioxidant as propyl gallate is a suitable method for iron gall ink damaged paper stabilization and preservation, according to the study results.

SYNTHESIS AND STUDY OF THE PROPERTIES OF EPOXYCYCLOCARBONATES BASED ON ACRYLATE-VINYL COPOLYMERS

A method of synthesis of acrylate-vinyl copolymers based on glycidyl methacrylate and styrene at different molar ratios and epoxy cyclocarbonates based on them was developed. Synthesis of styrene-glycidyl methacrylate (СP GMA/St) copolymers was carried out by the method of thermally initiated radical polymerization in steel reactors in the presence of 1% azo-bis-isobutyronitrile initiator at a temperature of 65 °C for 10 hours. The number of epoxy groups in the synthesized СP GMA/St, determined by the potentiometric titration method, naturally decreases with a decrease in the molar ratio of GMA/styrene. The synthesis of СP GMA/St epoxycyclocarbonates was carried out in a high-pressure autoclave by passing CO2 through the reaction mixture of a solution of KP in toluene with a catalyst (tetrabutylammonium bromide 5%) with stirring at a temperature of 110–120 °C, a pressure of (4-5) atm. The structure of СP and ECC was confirmed by IR spectroscopy. No bands of double bonds are observed in the IR spectra of СP GMA/St, there are vibration bands characteristic of oligostyrene and vibration bands of C=O, C–O–C and epoxy groups. During the formation of ECC, new vibration bands of cyclocarbonate groups with a maximum of 1802 cm-1 appear, changes are observed in the absorption region of C–O–C groups (1100–1300) cm-1, and the vibration bands of epoxy groups with a maximum of 843 cm-1 decrease. The study of relaxation transitions in acrylate-vinyl copolymers GMA/St and epoxy cyclocarbonates based on them using the DSC method showed that all samples are amorphous single-phase polymers. After changing the background, the excessive enthalpy observed during the first heating disappears, and the glass transition temperature shifts towards higher temperatures, which indicates the formation of a denser and thermodynamically balanced structure. The thermostability of the synthesized GMA/St copolymers and epoxy cyclocarbons was investigated by the method of thermogravimetry. It was established that all the obtained substances have one stage of weight loss and are heat resistant, since weight loss begins at a temperature above 240 °C. In the future, the obtained epoxycyclocarbonates will be used for the synthesis of polyurethanes by the non-isocyanate method.

Catalytic activity of two-dimensional cobalt-ZIF catalyst for NaBH4 hydrolysis

In this work, cobalt-ZIF catalysts were synthesized by water-based synthesis methods. Various hydrogen bond acceptor (tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), tetrabutylammonium bromide (TBAB) and trimethylphenylammonium bromide (TMPAB)) were co-added during cobalt-ZIF catalyst synthesis procedures to promote the deprotonation of 2-methyl imidazole and the deprotonated 2-methyl imidazole was then further coordinated with cobalt ion to form a ZIF framework. Co-addition of TMPAB during synthesis resulted in 3D imperfect rhombic dodecahedrals with high surface area (432.3 m2/g), while, the rest of used hydrogen bond acceptors (TMAB, TEAB, TPAB and TBAB) provided 2D ZIF-L structure with relatively small surface area and pore volume. All synthesized cobalt-ZIF with different structures and morphologies were used as a catalyst for H2 generation by NaBH4 hydrolysis reaction. It was found that all 2D cobalt-ZIF structures exhibited higher hydrogen production rate than that of the 3D imperfect rhombic dodecahedral structure. This can be explained by the cushion-shaped cavity of a two-dimensional framework exhibiting higher flexibility which can promote more diffusion of reactants than the tetrahedral structure of a 3D-framework. X-ray absorption spectroscopy was used to investigate the electronic state of cobalt and to monitor the changing of cobalt probe atom during hydrolysis reaction. The electronic state of cobalt for all catalysts was Co2+ with the same tetrahedral symmetry. The lowering of pre-edge peaks of cobalt K edge XANES spectra during hydrolysis reaction indicated to distortion of the symmetry which is related to the reduction of the catalytic performance.

Influence of tetrabutylammonium bromide based ionic liquid on the aggregation behavior of dodecyltrimethylammonium bromide in the range (293.15 K–313.15 K): acoustic and volumetric investigation

Abstract The effect of the ionic liquid analogue tetrabutylammonium bromide on the aggregation behaviour of the cationic surfactant dodecyltrimethylammonium bromide in aqueous medium was investigated with volumetric and compressibility measurements over a wide temperature range (293.15–313.15) K. The data obtained were used to obtain density data. Based on the density data obtained, the volumetric properties (apparent molar volumes and partial molar volumes) of the surfactant in unimeric and micellar forms were evaluated and discussed in terms of the respective ionic and dipolar interactions. The data obtained were analysed to determine the effects of (i) temperature and (ii) salt added to the surfactant. The results were also interpreted in terms of the molecular interactions occurring in the binary mixtures of the present study. The addition of tetrabutylammonium bromide has a lowering effect on the CMC values of the surfactant studied in aqueous medium.

Insight into the experiment and extraction mechanism for separating carbazole from anthracene oil with quaternary ammonium-based deep eutectic solvents

Carbazole is an irreplaceable basic organic chemical raw material and intermediate in industry. The separation of carbazole from anthracene oil by environmental benign solvents is important but still a challenge in chemical engineering. Deep eutectic solvents (DESs) as a sustainable green separation solvent have been proposed for the separation of carbazole from model anthracene oil. In this research, three quaternary ammonium-based DESs were prepared using ethylene glycol (EG) as hydrogen bond donor and tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide or choline chloride as hydrogen bond acceptors. To explore their extraction performance of carbazole, the conductor-like screeningmodelfor real solvents (COSMO-RS) model was used to predict the activity coefficient at infinite dilution (γ∞) of carbazole in DESs, and the result indicated TBAC:EG (1:2) had the stronger extraction ability for carbazole due to the higher capacity at infinite dilution (C∞) value. Then, the separation performance of these three DESs was evaluated by experiments, and the experimental results were in good agreement with the COSMO-RS prediction results. The TBAC:EG (1:2) was determined as the most promising solvent. Additionally, the extraction conditions of TBAC:EG (1:2) were optimized, and the extraction efficiency, distribution coefficient and selectivity of carbazole could reach up to 85.74%, 30.18 and 66.10%, respectively. Moreover, the TBAC:EG (1:2) could be recycled by using environmentally friendly water as antisolvent. In addition, the separation performance of TBAC:EG (1:2) was also evaluated by real crude anthracene, the carbazole was obtained with purity and yield of 85.32%, 60.27%, respectively. Lastly, the extraction mechanism was elucidated by σ-profiles and interaction energy analysis. Theoretical calculation results showed that the main driving force for the extraction process was the hydrogen bonding ((N–H…Cl) and van der Waals interactions (C–H…O and C–H…π), which corresponding to the blue and green isosurfaces in IGMH analysis. This work presented a novel method for separating carbazole from crude anthracene oil, and will provide an important reference for the separation of other high value-added products from coal tar.

Guest molecule optimum aggregation hypothesis and optimal concentrations for energy storage from the perspective of hydrate phase change-induced liquid layer

Tetrabutylammonium bromide (TBAB) semi-clathrate hydrate possesses a unique clathrate structure for capturing and sequestering small-molecule gases, such as CH4, H2 and, CO2 and the advantage of phase change energy storage. Elucidating the diversified reactions and determining the optimal phase change characteristics of TBAB hydrate is crucial to discovering and overcoming specific limitations hindering the large-scale applications. In this study, in situ macroscopic visualization, three-dimensional reconstruction via X-ray Computed Tomography, and differential scanning calorimeter measurements were performed to discover, verify, and analyze the distinct characteristics of TBAB hydrate phase change, including phase separation, three-dimensional structure, and thermal effects. The optimal concentration of TBAB hydrate energy storage was found and verified experimentally for the first time. A peculiar liquid layer (liquid-liquid phase separation) caused by hydrate-solution phase separation was observed after multiple formation-dissociation cycles. The liquid layer separated a region that optimized the hydrate phase change. The solutions with different initial concentrations could evolve an optimized phase-change region of the same concentration (37 wt%) via multiple cycles. The region of the same concentration was shown to be the result of optimal aggregation of molecules. In proving the particularity of the concentration in the optimized region, TBAB hydrate dissociation exhibit thermal effects that can be easily ignored (TBAB molecules ionization and ionic bond synthesis), which affected the TBAB hydrate latent heat measurement. Finally, the optimal concentration of TBAB hydrate phase change was determined as 37 ± 1 wt%, and the characteristics of the concentration, including the volume fraction, complete conversion of water molecules and TBAB molecules, and latent heat, were confirmed by the liquid layer. The experimental results obtained for the first time in this study are important guidance for TBAB hydrate in the field of gas capture and energy storage.

Application of Polymer-Embedded Tetrabutylammonium Bromide (TBAB) Membranes for the Selective Extraction of Metal Ions from Aqueous Solutions.

The selective extraction of metals from aqueous solutions is a very important stage in the hydrometallurgical processing of metallic waste. Leach solutions are usually a multicomponent mixture. The main impurity of aqueous solutions obtained after leaching using inorganic acids is iron. In this work, the membrane separation of iron(III) from nickel(II), cobalt(II), and lithium(I) was studied. The facilitated transport of metal ions using polymer inclusion membranes (PIMs) with tetrabutylammonium bromide (TBAB) as an ion carrier under various conditions was analyzed in detail. Several factors, such as the ion carrier concentration in the membrane as well as the effect of the inorganic acid concentration in the source/receiving phases on the kinetic parameters, were investigated. The results show that ionic liquid TBAB is a very selective ion carrier of Fe(III) towards Ni(II), Co(II), and Li(I).

Interactions of ammonium based ionic liquids with DNA in aqueous medium through Volumetric, acoustic and viscometric properties

Ionic liquids (ILs) have emerged as a promising alternative solvent for DNA based studies as most of the studied ILs enhance the stability of DNA and act as a media for extraction and storage. Investigation of IL-DNA interactions through spectroscopic and computational analysis have been carried out earlier and we here attempt to explore the interaction through physicochemical properties of IL-DNA mixture in water medium that provide fundamental knowledge of the solvation behaviour. Properties such as density, ρ, speed of sound, u and viscosity, η, of two ILs, Benzyltributylammonium chloride ([BTBA]Cl) and Tetrabutylammonium bromide ([TBA]Br) in water as well as in aqueous DNA solutions with varying concentrations were measured over a temperature range from 293.15 − 323.15 K and at atmospheric pressure. The derived volumetric properties were calculated to understand the strength and extent of the solute–solvent interactions prevail in the solution. The analysis of partial molar volume at infinite dilution, V2∞, helped in the comparison of the strength of the interactions in between the studied solutes. The second derivative of V2∞ with respect to temperature, (∂2V2∞/∂T2)P facilitated in identifying the influence of the solutes in water structure formation around the solute and it was interesting to note that, although both the ILs behaved similarly in water as structure makers, [TBA]Br showed variation in the presence of DNA by demonstrating water structure breaking effects. Similar results were obtained from the analysis of viscometric properties as well. Further, the capability of the ILs to stay solvated in the DNA aqueous solution was confirmed by the results from the solvation number calculations.

Crystal growth of tetra-n-butylammonium bromide hydrate nucleated from metallic particles

Nucleation of tetra-n-butylammonium bromide (TBAB) hydrate is unlikely to occur; thus, nucleation promotion is required to nucleate TBAB hydrate. In a previous study, it was found that addition of specific metallic particles effectively promotes nucleation of TBAB hydrate. TBAB hydrate is known to have two stable crystal structures (type A and type B). It is expected that the type of TBAB hydrate crystals that initially grow will differ depending on the molecular structure of the precursor liquid phase influenced by the added metallic particles. In this study, the correlation between the type of added metallic particles and the crystal structure of the formed TBAB hydrate was experimentally investigated. Addition of Ag, Ag–AgBr, Zn, and Zn–ZnO particles promoted nucleation of TBAB hydrate. When Ag or Ag–AgBr was added, type-A TBAB hydrate crystals formed from 10 wt% TBAB aqueous solution, where type-B TBAB hydrate should preferentially be formed. In contrast, when Zn or Zn–ZnO was added, only type-B TBAB hydrate crystals formed from 10 wt% TBAB aqueous solution. These results suggest that Ag and Ag–AgBr affect the molecular structure of the liquid phase, facilitating formation of type-A TBAB hydrate crystals.

Highly Efficient Flexible Perovskite Solar Cells on Polyethylene Terephthalate Films via Dual Halide and Low‐Dimensional Interface Engineering for Indoor Photovoltaics

Flexible perovskite solar cells are lightweight, bendable, and applicable to curved surfaces. Polyethylene terephthalate (PET) has become the substrate of choice compared to other plastic substrates like polyethylene naphthalate. PET is not only stable but also much cheaper to manufacture, an important factor for photovoltaics (PV). Herein, highly efficient devices on PET are demonstrated using a dual low‐temperature (≤100 °C) approach, first by anion mixing (replacing I with Br) of the lead‐containing perovskite composition, increasing bandgap (42% improvement), and then by interfacial engineering with tetrabutylammonium bromide (TBAB) (a further 26% improvement), reaching efficiencies of 28.9% at 200 lx and a record 32.5% at 1000 lx. The TBA+ cation intercalates into the structure, substituting formamidinium cations at the perovskite/TBAB interface, inducing the formation of large‐sized, lower dimensional structures over the 3D perovskite matrix. The resulting PV cell has 1.4 times higher carrier lifetime, one order of magnitude lower leakage currents, and 3 times lower defect densities, suppressing recombination. Importantly, stability (ISOS‐D1 protocol) improves by more than double with treatment. Highly efficient and stable cells on PET films enable seamless integration with wearable, portable, smart building, and Internet of Things electronic devices, expanding the reach of indoor applications.

Nitrogen-rich, click-based porous organic polymers featuring flexible amine cores for catalytic CO2/epoxide cycloaddition

CO2 utilization to produce value-added products such as cyclic carbonates, especially under mild catalytic conditions, is a promising strategy to reduce CO2 emissions to the environment. In this work, nitrogen-rich, click-based porous polymers (CPPs) were prepared from coupling of tripropargylamine and rigid diazido aromatic substrates, featuring 1,4-phenylene (TB), 1,5-naphthalene (TN), and 4,4′-benzanilide (TBA) linkers, in moderate to good yields (48–83%) using Cu-catalyzed azide–alkyne cycloaddition (CuAAC; TB-C, TN-C, TBA-C) and Huisgen cycloaddition (TB-H, TN-H, and TBA-H). The presence of the chelate tris(triazolylmethyl)amine ligands within the polymer's structure led to strong copper binding and consequently high copper loading ability of the CPPs. In addition, high contents of Lewis basic N donors (21–27 wt% N) of TB-C, TN-C, TBA-C are most likely attributed to strong interactions between CO2 and CPPs and exceptionally high CO2 selectivity over N2 at 273 K, based on gas sorption studies. The catalyst system TB-C/TBAB (TBAB = tetrabutylammonium bromide) promoted complete conversion of epoxides to cyclic carbonates under an atmospheric CO2 pressure, after 24 h or 48 h at 100 °C, with the exception of the epichlorohydrin substrate where 42% selectivity was observed by 1H NMR spectroscopy. The TB-C/TBAB catalyst system could be reused for five catalytic runs without a loss in catalytic activities and any pre-activation processes.

Facile Synthesis of Glycidyl Azide Polymer (GAP) in a Tetrabutylammonium Bromide/Ethylene Glycol Based Deep Eutectic Solvent

AbstractGlycidyl azide polymer (GAP) is an energetic material used in composite solid rocket propellants. Herein, a novel synthetic method for GAP was introduced using a tetrabutylammonium bromide and ethylene glycol‐based deep eutectic solvent (DES). Using this DES combination, the azidation of poly(epichlorohydrin) was successfully conducted within several hours. This strategy eliminates the use of organic solvents during the entire synthetic process and provides the advantage of recovery and reuse of the DES.

Synergistic Effect of Water-Soluble Hydroxylated Multi-Wall Carbon Nanotubes and Graphene Nanoribbons Coupled with Tetra Butyl Ammonium Bromide on Kinetics of Carbon Dioxide Hydrate Formation

In this work, the thermodynamics and kinetics of hydrate formation in 9.01 wt% tetra butyl ammonium bromide (TBAB) mixed with water-soluble hydroxylated multi-wall carbon nanotube (MWCNTol) systems were characterized by measuring hydrate formation conditions, induction time, and final gas consumption. The results showed that MWCNTols had little effect on the phase equilibrium of CO2 hydrate formation. Nanoparticles (graphene nanoribbons (GNs) and MWCNTols) could significantly shorten the induction time. When the concentration was ≤0.06 wt%, MWCNTols had a better effect on the induction time than the GN system, and the maximum reduction in induction time reached 44.22%. The large surface area of MWCNTols could provide sites for heterogeneous nucleation, thus shortening the induction time of hydrate formation. Furthermore, adding different concentrations of nanoparticles to the 9.01 wt% TBAB solution effectively increased the final gas consumption, and the maximum increase was 10.44% of the 9.01 wt% TBAB + 0.08 wt% GN system. Meanwhile, the suitable initial pressure and experimental temperature could also promote the hydrate formation and increase the motivation in hydrate formation. The 9.01 wt% TBAB + 0.02 wt% MWCNTol system had the best effect at 3.5 MPa and 277.15 K. The induction time was reduced by 66.67% and the final gas consumption was increased by 284.11% compared to those of the same system but at a different initial pressure and experimental temperature. This work helps to promote the industrial application of hydrate technology in CO2 capture and storage.

Selective extraction of plant bioactive compounds with deep eutectic solvents: Iris sibirica L. as example.

Deep eutectic solvents (DESs) are promising extractants with tuneable properties. However, there is a lack of reports about the influence of the nature of the original DES on obtaining the metabolomic profile of a plant. The aim of this study is to investigate the possibility of obtaining Iris sibirica L. chromatographical profiles with DESs based on various hydrogen bond donors and acceptors as extraction solvents. DESs were prepared by mixing choline chloride or tetrabutylammonium bromide with various hydrogen bond donors and investigated for the extraction of bioactive substances from biotechnological raw materials of I. sibirica L. The obtained extracts were analysed by HPLC with diode array detector (DAD) and Q-MS. Chromatographic profiles for I. sibirica L. extracts by eight choline chloride DESs and six tetrabutylammonium DESs have been obtained. It has been found that selective recovery of bioactive substances can be achieved by varying the composition of DESs. Eleven phenolic compounds were identified in I. sibirica L. using HPLC-MS. Phase separation was observed with acetonitrile for four DESs. New flavonoid derivatives have been found in DES extracts compared with methanol extracts. The results showed the possibility of DES usage for extraction without water addition. Selectivity of DESs varies depending on the chemical composition of hydrogen bond donors and acceptors. Choline chloride is a more suitable hydrogen bond acceptor for the flavonoid extraction. Choline chloride-lactic acid (1:1) DES has demonstrated a metabolic profile that was the closest to the methanol one and enhanced the extraction up to 2.6-fold.

Green and low-cost deep eutectic solvents for efficient extraction of basic and non-basic nitrides in simulated oils

The removal of nitrogenous compounds from fuel oil is essential to reduce NOx emissions and improve the quality of the oil. In the present work, a new method of nitrogen removal using deep eutectic solvents (DESs) as extractants is reported. Seven green and low-cost quaternary ammonium acidic DESs were prepared and used for the extraction of basic N-compounds (quinoline) and non-basic N-compounds (indole) in model oil. The results indicated that the structure of DESs has a profound effect on denitrification performance. Under the same conditions, DES composed of tetrabutylammonium bromide and formic acid ([TBAB:2FA]) showed the best denitrification performance and could effectively remove both basic and non-basic nitrogen compounds. The main experimental parameters such as the mass ratio of DESs to model oil, extraction temperature, time, initial concentration of N-compounds and water content when [TBAB:2FA] were used as extractants were investigated. Under the optimal conditions (initial N-compounds concentration of 200 ppm, DESs-oil mass ratio of 1:5, 30 °C, and 60 min of extraction), the extraction efficiency of quinoline and indole were 99.60% and 98.42%, respectively. In addition, the DESs were regenerated with deionized water. When reused four times, the denitrification capacity remained high. Finally, the mechanism of the extraction process was investigated by FT-IR spectroscopy. This research is expected to provide a theoretical reference for the removal of nitrogen compounds from fuel oil.

Antimicrobial, antioxidant, and toxicity assessment of Ammonium-Based deep eutectic solvents with formic acid and butyric acid hydrogen bond donors

An investigation on the toxicological assessment of tetrabutylammonium bromide (TBABr)-based deep eutectic solvents (DESs) with formic acid (FA) and butyric acid (BA) towards bacteria, fungi, Cyrinus Carpio fish, and mouse fibroblast cell line was performed. A homogenous mixture of DESs was formulated by heating at 60 °C for 20 min which was further analyzed by Fourier Transform Infrared Spectroscopy (FTIR). In FTIR, a significant difference was found in the absorbance of DESs and their precursors. Among tested DESs, TBABr: FA exhibited maximum zone of inhibition towards tested bacterial strains in comparison to TBABr: BA. While TBABr: BA was found to be more effective against both fungal strains than TBABr: FA. TBABr: FA had a higher lethal concentration at 50% (LC50) than TBABr: BA against Cyprinus carpio fish. Both DESs were found to have a higher % of cell viability at higher concentrations while a gradual decline was observed with a decrease in concentration. However, both DES had ∼50% of the DPPH scavenging activity in comparison to standard (ascorbic acid). In conclusion, both DESs had been successfully formed and were found less harmful at their higher concentrations, thus can be used as promising solvents in the future.

Electrical conductivity-based assessment method for semi-clathrate hydrate conversion and phase change characteristics in gas capture and energy storage

In gas capture/storage and energy storage, tetrabutylammonium bromide (TBAB) hydrates have been regarded as superior carriers owing to their unique molecular selectivity and high latent heat. Hydrate conversion amount is a significant parameter in evaluating gas selection and cold storage characteristics. This study proposes a method for calculating hydrate conversion amount proposed based on the correlation between electrical conductivity and solution concentration. The correlation index (R2) between electrical conductivity and TBAB solution concentration was above 0.99 at concentrations less than below 5 wt%. The conversion amounts of different hydrate types were obtained using a unique hybrid calculation method. The differences in hydrate conversion amount, conversion ratio, and memory effect were compared at different mass fractions. The results indicated that the hydrate morphology and accumulation patterns were influenced by the TBAB solution ionization degree. Regular hexagonal TBAB hydrate crystals were observed at a low ionization degree. The maximum conversion ratio of TBAB hydrate reached 96% (1 °C/30 wt%). The variation trend of TBAB hydrate phase equilibrium temperature was consistent with that of the electrical conductivity of the solution. The investigation of the memory effect revealed that the phase change process of TBAB hydrate is more predictable in high-concentration initial solutions.

Fluorine recovery through alkaline defluorination of polyvinylidene fluoride

The establishment of technological approaches for the defluorination of waste fluoropolymers and recovery of eliminated F– may contribute to the development of fluorine recycling routes. In this study, we investigated the effects of alkalinity, phase transfer catalyst (PTC) concentration, reaction temperature, and solvent types on the defluorination of polyvinylidene fluoride (PVDF) by alkaline wet processing. The rate of defluorination of PVDF in 4.0 M sodium hydroxide (NaOH) and 50 mM tetrabutylammonium bromide (TBAB) under aqueous conditions reached 89.2%. In addition, the defluorination reaction proceeded faster in solvents such as diethylene glycol (DEG) and triethylene glycol (TEG) than in water because of the high affinity between PVDF and these diols. To investigate the feasibility of developing a fluorine recycling route, the defluorination of a photovoltaic (PV) backsheet and subsequent CaF2 precipitation from the eliminated F– was examined. A total of 88.3% of F contained in the PV backsheet was recovered as CaF2, which satisfied the quality standards of commercial fluorspar. This study demonstrated that alkaline wet processing is effective for the defluorination of PVDF and that the establishment of a F recycling route along the F supply chain may be feasible.

Design and Discovery of Water-Soluble Benzooxaphosphole-Based Ligands for Hindered Suzuki-Miyaura Coupling Reactions with Low Catalyst Load.

We report a new class of highly effective, benzooxaphosphole-based, water-soluble ligands in the application of Suzuki-Miyaura cross-coupling reactions for sterically hindered substrates in aqueous media. The catalytic activities of the coupling reactions were greatly enhanced by the addition of catalytic amounts of organic phase transfer reagents, such as tetraglyme and tetrabutylammonium bromide. The optimized general protocol can be conducted with a low catalyst load, thereby providing a practical solution for these reactions. The viability of this new Suzuki-Miyaura protocol was demonstrated with various substrates to generate important building blocks, including heterocycles, for the synthesis of biologically active compounds.