Tetrabutylammonium Bromide Research Articles

Effects of Surfactants on the Stability of Nickel Ferrite/Water Nanofluid

Nanofluid stability is a critical factor for the effective application of nanofluids in various fields. One simple and effective method to enhance nanofluid stability is through the addition of surfactants. This study examines the effect of different surfactants on the stability of nickel ferrite (NiFe₂O₄)/water nanofluid. The nanofluids were synthesis using the two-step method, and the surfactants investigated inculded oleic acid, polyethylene glycol 400, tetrabutylammonium bromide, gum arabic, and citric acid. Different concentrations for each surfactant were tested by adjusting the nanoparticles-to-surfactant ratio. The suspension stability was evaluated through visual observation, Zeta potential measurements, and thermal conductivity analysis. The most stable NiFe₂O₄/water nanofluid was achieved using citric acid surfactant, with a nanoparticles-to-surfactant volume ratio of 1:0.25, a Zeta potential value of -35.0 mV and an average thermal conductivity of 0.585 ± 0.007 W/m·K. The results of this study are important for developing nanofluid and magnetic nanofluid systems with optimum conductive heat transfer performance.

Chitosan-Based Porous Carbon Materials with Built-In Lewis Acid Boron Sites for Enhanced CO2 Capture and Conversion via an Electron-Inducing Effect.

Electron-induced effects, which are prevalent in adsorption and heterogeneous catalytic reactions, can significantly influence the state and uptake of adsorbates. Here, we demonstrate the in situ doping of electron-deficient boron into the backbone of chitosan-based porous carbon materials. Despite a reduction in specific surface area, the resulting boron-doped porous carbons (NBPCs) exhibit an enhanced CO2 adsorption performance, with sample NBPC-10 achieving CO2 adsorption capacities of 7.62 and 4.82 mmol·g-1 at 273 and 298 K, respectively. This improvement is attributed to the electron-induced effect of boron doping, which also enhances the separation selectivity of CO2 from N2. Additionally, the high CO2 adsorption capacity fosters synergism between NBPCs and the cocatalyst tetrabutylammonium bromide (TBAB), thereby augmenting the catalytic activity for the cycloaddition of CO2 and epoxide. Notably, cyclic carbonate yields exceeding 99% were attained even under 1 bar of CO2. Controlled experiments corroborated the pivotal role of boron-doping-induced modifications in the porous carbon structure in enhancing both CO2 selective adsorption and conversion performance. Furthermore, NBPCs demonstrated excellent recyclability as both adsorbents and catalysts, offering fresh perspectives for the design of functionalized porous carbon materials tailored for CO2 capture and conversion.

Boosting H2O2 Activation for the Efficient Alkene Epoxidation over Polyoxometalate‐based Tetrakaidecahedron‐like Nanodice Assemblies

The activation of hydrogen peroxide (H2O2) as a terminal oxidant holds great promise for catalytic oxidation processes. However, developing an efficient catalyst for the epoxidation of bulky organic molecules with H2O2, including cyclic alkenes, remains challenging. In this research, a lacunary polyoxometalate (POM)‐based tetrakaidecahedron nanodices (NDs) are synthesized by [PW11O39]7− (PW11) clusters with tetrabutylammonium bromide (TBAB). The NDs exhibit significantly enhanced catalytic activity in the epoxidation of cyclooctene, with a yield 55.4 times greater than that of the raw PW11. Conversely, nanospheres (NSs) assembled from non‐lacunary POM clusters of [PW12O40]3− (PW12) under the same conditions achieve only a 2.9% yield, highlighting the essential role of the lacunary PW11 structure in NDs. Raman spectroscopy and density functional theory calculations confirm that the active hydroperoxo species from H2O2 activation serves as the effective epoxidizing agent. The reduced energy barrier for H2O2 activation on PW11, relative to PW12, corroborates the superior activity of the NDs. Furthermore, the intermediate generated post‐H2O2 activation shows stronger adsorption of cyclooctene, increasing oxygen transfer to cyclooctene during the epoxidation process. This study demonstrates the exceptional performance of an assembly structure utilizing lacunary POMs for the activation of H2O2 and subsequent oxidation reactions.

Electrochemical oxidative dearomatization of electron-deficient phenols using Br+/Br- catalysis.

An electrochemical method for the oxidative dearomatization of electron-deficient phenols by employing tetrabutylammonium bromide as a mediator under aqueous biphasic conditions is reported. This approach represents a safer alternative to the use of stoichiometric chemical oxidants and enables oxidative dearomative spirolactonization and spiroetherification reactions. Compared to previous approaches based on direct electrolysis, this strategy expands the substrate scope to electron-deficient phenols. Cyclic-voltammetry analysis suggests that the bromide ions might be oxidized to Br2 or Br3- ions that are in equilibrium with the catalytically active hypobromite under aqueous conditions.

Kinetics of reduction of m‐iodonitrobenzene by aqueous ammonium sulfide under liquid–liquid phase transfer catalysis

AbstractHydrogen sulfide generated during hydrotreatment of sour crude oil fractions could be absorbed into aqueous ammonium hydroxide to produce ammonium sulfide. This ammonium sulfide can then be utilized to produce commercially valuable aromatic amino compounds by reducing the corresponding nitro compounds. In this work, the reduction of m‐iodonitrobenzene (m‐INB) to m‐iodoaniline (m‐IA) was performed by aqueous ammonium sulfide using a phase transfer catalyst, tetrabutylammonium bromide (TBAB). The study scrutinized the influences of various parameters such as concentrations of TBAB and m‐INB, as well as initial sulfide and ammonia concentrations, on the rate of reaction of m‐INB. An 11‐fold increase in reaction rate was obtained with only 0.09 kmol of catalyst TBAB per cubic meter of the organic phase. The selectivity of m‐IA was found to be100%. The reaction was found to be kinetically controlled with an activation energy of 40.0 kJ/mol. The rate of reaction of m‐INB was observed to be directly proportional to the concentrations of m‐INB, initial sulfide, and catalyst. A pseudo‐first order kinetic model was developed to correlate the conversion versus time data and an excellent agreement between observed and predicted reaction rates was obtained. The present work has very high commercial importance as it could be a viable alternative to the traditional Claus process to arrest H2S released by petroleum refineries.

Extractive rectification using DES for benzene‐cyclohexane‐cyclohexene ternary azeotropic system

AbstractBACKGROUNDBenzene, cyclohexane, and cyclohexene are ternary azeotropic systems, which cannot achieve high‐purity separation by ordinary distillation, but this issue can be solved by extractive distillation. Deep Eutectic Solvents (DES) is a ‘green solvent’ that has emerged in recent years and is often used as an extractant.RESULTSIn this study, the COSMO‐SAC solvation model was used to calculate the infinite dilution activity coefficients (γ∞) of DES with different compositions to screen suitable DES, and the effect was demonstrated by vapor–liquid equilibrium experiment (VLE). In addition, the effect of intermolecular interactions was explored in this study by means of independent gradient (IGM) equivalence plot, and process simulations were carried out by means of Aspen Plus software.CONCLUSIONVLE experiments showed that the combination of DES extractants tetrabutylphosphonium bromide: levulinic acid (1:4) and tetrabutylammonium bromide: cyclobutyl sulfone (1:4) could break the azeotropic relationship of benzene, cyclohexane, and cyclohexene ternary systems. In addition, using Aspen process simulation to compare the screened DES extractant with the industrially used dimethylacetamide (DMAC) extractant, the use of the screened DES extractant was able to reduce the condenser and reboiler energy consumption by 14.93%. © 2024 Society of Chemical Industry (SCI).

Caboxylative Coupling of N‐(Arylmethyl)sulfonimides with Allyltributylstannane Catalyzed by Palladium Nanoparticles Involving Benzylic C−N Cleavage

AbstractThe palladium‐catalyzed three‐component coupling of aryl (hetero) methylsulfonamide, allyltributyltin and carbon dioxide (carboxylative Stille coupling reaction) was successfully conduced to produce β,γ‐unsaturated esters in satisfactory to good yields. The reaction was carried out under mild conditions by using in situ generated palladium nanoparticles as catalyst through the formation of π‐allylpalladium sulfonamide intermediates in the presence of tetrabutylammonium bromide (TBAB).

Synthesis of Tetrabutylammonium Tri(1,1,1,3,3,3-hexafluoro-2-propanol)-Coordinated Fluoride and Its Application to Anodic Fluorination

Organofluorine compounds are widely used in pharmaceuticals, agrochemicals, and functional materials due to their specific properties. However, organofluorine compounds are rarely found in nature. Therefore, organofluorine compounds must be synthesized using fluorinating agents. While Hydrogen fluoride (HF) is the most typical nucleophilic fluorinating agent, it is toxic and corrosive. Furthermore, HF is a gas at room temperature, making it difficult to handle in the ordinary laboratory. On the other hand, potassium fluoride (KF) is one of the safest and cheapest fluorinating agents, but KF is insoluble in most organic solvents. In contrast, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) dissolves KF at high concentrations.Tetrabutylammonium fluoride (TBAF) is a highly reactive fluorinating agent that is soluble in organic solvents. However, preparation of anhydrous TBAF is difficult, because TBAF readily forms hydrates due to its high hygroscopicity. The reaction of tetrabutylammonium cyanide with hexafluorobenzene is one of the most promising methods for the synthesis of TBAF. On the other hand, TBAF-alcohol complexes such as TBAF(t-BuOH)4 have been reported as fluorinating agents with low hygroscopicity. With these facts in mind, we investigated the synthesis of TBAF from KF based on the ion exchange reaction between KF and tetrabutylammonium bromide (TBABr) in HFIP in this work.First, TBAF was synthesized by the ion exchange reaction between KF and TBABr in HFIP. 1H and 19F NMR measurements of the obtained product revealed that it is not TBAF but TBAF(HFIP)3 with three molecules of HFIP coordinated to TBAF. The TBAF(HFIP)3 was obtained in excellent yield without complicated operations. Next, anodic fluorination of a sulfide was investigated using TBAF hydrate or TBAF-alcohol complexes. As results, the corresponding fluorinated product was obtained in good yield only when TBAF(HFIP)3 was used. These results may be due to the low nucleophilicity and oxidation resistance of HFIP. From these results, TBAF(HFIP)3 would be a promising new supporting electrolyte and fluorinating agent. Figure 1

Molecular Insights into the Concentration Dependent Promotion Effect of Tetrabutylammonium Bromide on Hydrate Growth: A Molecular Dynamics Simulation Study.

Tetrabutylammonium bromide (TBAB) has been proven to improve the growth of hydrate via experimental methods, which may be attributed to its different concentrations. In this study, the molecular dynamics (MD) simulation is employed to investigate the concentration dependent promotion effect of TBAB on the growth of CO2 hydrate. The tetrahedral order parameter, number of cages, hydrate crystal growth trajectories, significant microconfigurations, and distribution of CO2 and TBAB are analyzed in detail. It is found that the promotion effect of TBAB is more prominent at low concentrations (5 and 10 wt %) than that at high concentrations (15 and 20 wt %). During the growth of hydrate crystal, tetrabutylammonium (TBA+) ions adsorb on the hydrate crystal and serve as guest molecules to form TBA+ semiclathrate hydrate cages. Then, the TBA+ semiclathrate hydrate cages undergo a self-adjustment process and induce the generation of CO2 hydrate cages. At high concentrations, the great accumulation of TBA+ at the hydrate-liquid interface disturbs the effective adsorption and self-adjustment processes, and the tightly packed arrangement of TBA+ at the gas-liquid interface partially inhibits the mass transfer of CO2. This study provides visible mechanisms of the concentration dependent promotion effect of TBAB from the microscopic level, which complements the vacancy in experimental studies.

Hydrate phase equilibrium of hydrogen with THP, DCM, TBAB+THF and sulfur hexafluoride +TBAB aqueous solution systems

Experimental hydrogen hydrate dissociation data with single thermodynamic additive: tetrahydropyran (THP, with oxygen-containing functional group) or dichloromethane (DCM, with halogen group), and thermodynamic additive mixtures: tetrahydrofuran (THF) + tetrabutylammonium bromide (TBAB) system and sulfur hexafluoride (SF6) +TBAB system were reported with temperature range from 275.33 to 282.98 K and pressure range from 1.65 to 12.63 MPa. Other experimental data were collected from the literature. The compared results showed that the oxygen-containing or halogen functional group can significantly affect the hydrogen bonding between water molecules, which present great promoting effects on hydrogen hydrates formation. Also, the promoting effects of mixture additives on the phase equilibrium of hydrogen hydrates were investigated. The results indicated that the combination of thermodynamic additives showed better promoting effects on hydrate formation compared to the individual ones. And the results obtained in this work would provide useful information to select suitable and effective thermodynamic additives for hydrate-based hydrogen storage technology.

Electric Response of a Negative Dielectric Anisotropy Nematic Liquid Crystal Doped with Ionic Dopant

The electrical properties measurements have been performed in a homogeneous alignment parallelepiped cell containing 4-methoxy benzylidene- 4-butylaniline (MBBA) liquid crystal doped with 0.02%wt tetrabutylammonium bromide (TBAB). The measurement of the complex permittivity was conducted in the nematic phase, covering a frequency range of 42 Hz to 5 MHz. A new relaxation mode was observed in the low-frequency region, which was not present in pure MBBA. The obtained dielectric dispersion could be fitted using the double Cole–Cole formula to determine the relaxation frequencies. The steady-state current exhibited a nonlinear dependence on the applied voltage, and hysteresis was observed in the transient current-voltage characteristic curve.

Influences of hydrogen-bond promoting hydroxyl group on photophysical and catalytic properties of lanthanide pyridine dicarboxylate frameworks

To study the influences of hydrogen bonding interactions on photophysical properties and catalytic activities with insignificant interference from structural disparity, two new isostructural [LnIII2(OH-pda)(ox)2(H2O)4]∙4H2O coordination polymers (LnIII = EuIII (I) and NdIII (IIa), OH–H2pda = 4-hydroxypyridine-2,6-dicarboxylic acid, H2ox = oxalic acid) were synthesized and characterized. They are also isostructural to [NdIII2(pda)(ox)2(H2O)4]∙4H2O (IIb), H2pda = pyridine-2,6-dicarboxylic acid) containing pda2− instead of OH-pda2-. The identical framework structure of IIa and IIb with additional hydrogen bonding interactions in IIa due to –OH group of OH-pda2- has been presented. Based on IIa and IIb, the effects of the –OH group on photophysical properties and catalytic activities were then investigated without structural bias. With reference to the UV–vis absorption and phosphorescent emission spectroscopy, the singlet (S1) and triplet (T1) state energies of OH–H2pda (41,600 and 19,200 cm−1), H2pda (48,200 and 23,300 cm−1), OH-pda2- (IIa, 41,400 and 22,500 cm−1) and pda2− (IIb, 47,100 and 23,300 cm−1) were determined from which the influences of the –OH group have been revealed. Important roles of the –OH group as electron-donating group as well as hydrogen bond promoter have been proposed. Catalytic activities of IIa and IIb were comparatively examined using the solvent-free CO2 cycloaddition reaction at atmospheric pressure with epichlorohydrin in the presence of tetrabutylammonium bromide. The inferior performance of IIa (maximum yield of 62(±2)%) to IIb (maximum yield of 68(±2)%) was unexpectedly disclosed and the drawback of the substantial involvement of the catalytic sites in hydrogen bonding interactions has been demonstrated. Their reusability was additionally explored.

A novel electrochemical sensor based on ꞵ-cyclodextrin/bismuth oxybromide/multi-walled carbon nanotubes modified electrode with in situ addition of tetrabutylammonium bromide for the simultaneous detection and degradation of tebuconazole.

A novel electrochemical sensor-based glassy carbon electrode (GCE) was fabricated and appliedtosimultaneous detection and degradation of tebuconazole (TBZ) for the first time.TheGCE was consecutively modified by multi-walled carbon nanotubes (MWCNTs), bismuth oxybromide (BiOBr), ꞵ-cyclodextrin (ꞵ-CD), and in situ addition of tetrabutylammonium bromide (TBABr). The detection was based on the decreasing of Bi signal at its anodic potential (Epa) of 0.05V. Under the optimum conditions, the modified electrode exhibited a linear response to TBZ in the concentration range 1-100μg L-1 with a detection limit of 0.9μg L-1. TBZ was firstly adsorbed on the surface of the modified electrode through host-guest molecule interactions of the ꞵ-CD. The adsorption was further enhanced by the large surface area of BiOBr and MWCNTs. The adsorbed TBZ on the electrode surface hindered the electron transfer of Bi, thus decreasing the oxidation of Bi. In addition, the in situ addition of tetrabutylammonium bromide (TBABr) enriched TBZ via electrostatic interactions, increasing its detection sensitivity. The fabricated electrochemical sensor was applied to determine TBZ in water and soil samples from rice fields with recoveries of 80.5-100.5% and 87.6-112%, respectively. Furthermore, the degradation of TBZ on the modified electrode was studied under a solar light simulator. The degradation percentage (100%) of TBZ (50µg L-1) was achieved in5min owing to the excellent photocatalytic properties of BiOBr.

High‐Throughput Experimentation (HTE) Applied to the Synthesis of API Impurities: A Case Study in Oxidative Decarboxylation of Aryl Acetic Acids

AbstractHigh‐throughput experimentation (HTE) has dramatically impacted experimental reaction development by enabling the rapid exploration of a diverse set of reaction conditions. During the past few decades, HTE has evolved as a tool to expedite reaction discovery and optimization. This work details the application of HTE to synthesize impurities of active pharmaceutical ingredients (APIs) with ketone/aldehyde functionality, specially focusing on ibuprofen impurity E. Initial experiments using K2S2O8 as oxidant yielded moderate results. Subsequent HTE screens identified cerium ammonium nitrate (CAN) and RuCl3‐NaIO4 as new effective decarboxylative oxidants, with RuCl3‐NaIO4 in the presence of tetrabutylammonium bromide (TBAB) achieving the highest yield of 65 %. This optimized method was successfully applied to synthesize ibuprofen impurity E on a gram scale. Additionally, the applicability of these methods to obtain other API related substances, such as naproxen impurity L and ketoprofen impurity A, was demonstrated. This research highlights the potential of HTE to streamline the synthesis of API impurities, making them widely accessible for pharmaceutical development purposes.

Enhanced Study of CO2 Hydrate Formation in Marine Oil–Gas Based on Additive Effect

During marine oil–gas extraction, significant amounts of carbon dioxide (CO2) gas are often produced. Effectively separating these associated CO2 gases during extraction has become a critical technical challenge. Therefore, this paper aims to enhance the efficiency of CO2 hydrate-based capture technology and conduct relevant research. The goal is to increase the driving force for hydrate formation by combining the traditional thermodynamic additive TBAB with pressure modulation and to improve the hydrate formation rate through the use of multiple kinetic promoters. This paper presents the initial investigation into the effect of the thermodynamic accelerator tetrabutylammonium bromide (TBAB) on the characteristics of CO2 hydrate formation. The promotion effects of TBAB solutions with varying mass concentrations (3%, 5%, 7.5%, 10%) and reaction pressures (3 MPa, 4 MPa) were subjected to a systematic analysis, and the optimal conditions were identified as 4 MPa and a 5 wt% TBAB concentration. Subsequently, the impact of combining TBAB with kinetic promoters (SDS, nano Al2O3, L-methionine, L-leucine) on CO2 hydrate generation characteristics was further investigated. In this paper, the effect of a single promoter on the generation characteristics of CO2 hydrate was investigated, and the efficient carbon trapping ability of the complex promoter was verified, which provides theoretical support for the application of CO2 trapping technology using the hydrate method.

Electricity-Driven Strain-Release Cascade Cyclization of Bicyclo[1.1.0]butane (BCB): Stereoselective Synthesis of Functionalized Spirocyclobutyl Oxindoles.

Spirocyclobutyl oxindoles, characterized by their unique three-dimensional structures, are valuable building blocks for many pharmacophores and drug units. However, stereoselective synthetic strategies for these scaffolds remain underdeveloped, with most existing methods relying on transition metal catalysts and stoichiometric redox reagents. In this work, we introduce an electrochemical strain-release driven cascade spirocyclization of bicyclo[1.1.0]butane (BCB) derivatives for the stereoselective synthesis of functionalized spirocyclobutyl oxindoles. Tetrabutylammonium bromide serves a dual purpose as both a supporting electrolyte and brominating agent. The method offers a broad substrate scope, high atom economy, and excellent diastereoselectivity. The stereoselectivity of the product is controlled by minimizing the dipolar repulsion between the amide C=O and the C-Br bonds. We also explored the methodology's versatility by applying it to various functionalizations and demonstrated its scalability for practical use. The efficient derivatization of the products allowed for the rapid creation of a diverse library of functionalized spirocyclobutyl oxindoles.

Rheological behavior of deep eutectic solvent promoted methane hydrate formation

Natural gas hydrates are recognized as a crucial and sustainable energy resource. The formation, dissociation, and flow properties of CH4 hydrate from deep eutectic solvents (DESs) are investigated using a high-pressure rheometer. In this work, rheological experiments are performed using two DESs namely, tetrabutylammonium bromide + ethylene Glycol (TBAB + EG, DES1) and methyltriphenylphosphonium bromide + ethylene Glycol (MTPB + EG, DES2) at 1 wt% concentration, 274 K temperature and 8 MPa pressure. The hydrate formation starts around 1.7 h for DES1 and around 4 h for DES2. Pressure and viscosity of the slurry are analyzed while methane hydrate forms and dissociates. The pressure drop experienced during hydrate formation is roughly 1.4 MPa for DES1 and 1.7 MPa for DES2. Further, viscosity profiles are analyzed for both DESs with varying shear rate. The viscosity gradually decreases as the shear rate increases. At equilibrium conditions of pure CH4, a spike is observed during dissociation. The rheological data is further analyzed with Cross model to validate the shear-thinning behavior of methane hydrate.

Effect of water on the excess properties of eutectic solvents

Three eutectic solvents were created utilizing a heating and stirring process. The solvents consist of tetrabutylammonium bromide and levulinic acid, as well as tetrabutylammonium chloride with either levulinic acid or lactic acid. The characterization of the samples was conducted using 1H NMR and IR techniques. The density and viscosity of three different low eutectic solvent and water binary mixture systems were determined within the temperature range of 293.15 to 333.15 K. The volume properties (excess molar volume, coefficient of expansion, coefficient of excess expansion) of the binary mixtures with different amounts of water were thoroughly investigated across the complete range of mole fraction. The study also investigated the impact of viscosity parameters, such as viscosity deviation and Excess activation Gibbs free energy of viscous flow. Furthermore, an analysis was conducted on the interaction between the eutectic solvent and the solvent molecules in the binary mixture. This analysis revealed the presence of hydrogen bonds between the eutectic solvent and water molecules. Moreover, it was confirmed that the excess properties could be fitted with the Redlich-Kister equation with r2 ≥ 0.99,demonstrating high suitability for binary mixes consisting of low eutectic solvents and water.

Synthesis of Aryl Alkyl Thioethers via a Copper-Catalyzed Three-Component Reaction with DABSO, Aryldiazonium Salts, and Alkyl Bromides.

We developed a method for synthesizing aryl alkyl thioether compounds via a three-component reaction involving aryldiazonium salts, 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide), and alkyl bromides. Optimal yields were achieved when a copper catalyst was used in conjunction with zinc and tetrabutylammonium bromide in an acetonitrile solvent at 130 °C for 10 h. This methodology demonstrates good functional group tolerance and enables the successful synthesis of various aryl alkyl thioethers with moderate to high yields.

Construction of the Co3O4/Nb2O5 Composite Catalyst with a Prickly Spherelike Architecture for CO2 Cycloaddition with Styrene Oxide.

A high-performance Nb2O5-based catalyst for the cycloaddition of CO2 with SO is designed by properly unifying the concepts of compositional regulation and architectural engineering. The Co3O4/Nb2O5 composite catalyst shows an intriguing prickly spherelike morphology. It exhibits a high styrene carbonate (SC) yield of 94.3% within 4 h (0.0824 mol g-1 h-1) under mild reaction conditions (0.4 MPa of CO2 and a reaction temperature of 90 °C) assisted by tetrabutylammonium bromide (TBAB). The coupling of Co3O4, which chemically interacts with Nb2O5, can effectively modulate the electronic structures of Nb2O5, constructing abundant acid/base sites for effectively activating the reactants and boosting the intrinsic activity. The high activity, cost-effectiveness, and good recyclability make the tailor-made Co3O4/Nb2O5 prickly spheres more appealing for commercial applications. This work offers new insights into designing and constructing well-integrated metal oxide composites for the cycloaddition of CO2 with an epoxide.