Effect Of Phase Transfer Catalysts Research Articles

The role of phase transfer catalysts on properties of polyamide thin-film composite forward osmosis membranes

In this article, 1,3,5-benzenetricarbonyl trichloride (TMC), m-phenylenediamine (MPD) and phase transfer catalysts (PTCs) were used to produce polyamide thin-film composite (TFC) forward osmosis (FO) membranes through interfacial polymerization (IP) reaction. The effects of dodecyl trimethyl ammonium chloride (DTAC), sodium dodecyl sulphate (SDS) and dodecyl dimethyl betaine (BS12) on the polyamide molecular aggregation structures, surface morphology and FO separation performance of the membranes were systematically investigated. In the FO process, concentrated 1.0 M NaCl aqueous solution was chosen as the draw solution and 0.1 M NaCl aqueous solution was used as the feed solution (at room temperature). Separation performance included the water flux (Jw) and reverse salt rejection (reverse solute flux, RS). The experiment proved that PTCs can regulate the molecular chain aggregation state and surface morphology of polyamide, which can lead to a relatively definite improvement in water flux (11.5 L m−2 h−1) (DTAC-polyamide). Simultaneously, the polyamide surface morphology was found to play a major role in the water permeability of the FO membrane rather than the density of the skin layer (i.e., degree of cross-linking), and we found that a relatively smooth surface is more conducive to weakening the external concentration polarization (ECP) phenomenon that occurs in the FO process. We attribute this mechanism on polyamide to the size effect and charge interaction of PTCs. In the current study, the balanced effect of the synergistic interaction of the molecular structure and rough surface of polyamide on FO separation performance should be comprehensively considered.

Kinetic study for benzyloxylation of p-bromotoluene using phase transfer catalyst assisted by microwave irradiation

The synthesis of 4-benzyloxy toluene was successfully carried out by reacting the sodium benzyloxide (BnO−Na+) with p-bromotoluene and sodium hydroxide/phase transfer catalyst system at 50°C under microwave irradiation. The nucleophilic susbstitution reaction was well explained by comparing the phase transfer catalyst system and microwave irradiation. The chemical kinetics of the reaction depends on the amount of catalyst, amount of sodium hydroxide, effect of phase-transfer catalysts, volume of benzylalcohol (BnOH) and temperature on the transformation of the reaction were studied.

Development of ketonic resin by polymerization reaction: A critical review

Synthetic resins are used for various applications including in paint industry to improve the glossiness, adhesiveness, hardness, and dryness of paints. Resins are essentially polymers, which are builds up from simple molecules or monomers and can be prepared mainly by either addition polymerization or condensation polymerization. Ketones and aldehydes can be converted to resinous products by condensation reaction. The desired property of a synthetic resin greatly depends on its method of preparation and its field of application. In this communication, the literature pertaining to the self–condensation of ketones to yield dimer, trimer and tetramer products and also the condensation of various ketone molecules with aldehydes to produce ketone–aldehyde resins are analyzed and a state–of–the–art review is written. The present study provides an overview of: i) effect of various operating parameters like reaction time, temperature, pressure, type of catalyst and its loading on a condensation polymerization reaction; ii) various techniques and ideas to analyze the product properties and to remove the catalyst from the reaction mass; iii) effect of phase transfer catalysts (PTCs) on the resin product properties such as softening temperature, moisture content, gardener color number etc. In a nutshell, an attempt has been made to get the aforementioned aspects together in a coherent manner so that the information is available at a glance and is expected to be useful to the researchers and for industrial practices.

New Role of Layered Silicates as Phase Transfer Catalyst for In Situ Polymerization of Poly(ethylenetetrasulfide) Nanocomposite

In this study, polyethylenetetrasulfide/montmorillonite nanocomposite (PETS/nanoclay) is synthesized from ethylene dichloride and sodium tetrasulfide monomers by in situ polymerization method. The effect of phase-transfer catalyst (PTC) on polymerization kinetics in addition to the structure of resulting PETS containing nanoclay is investigated. The results show that surface-modified montmorillonites by methyl tallow bis-2-hydroxyethyl quaternary ammonium chloride could properly act as PTC. Therefore, it is demonstrated that the addition of nanoclay as PTC reduces the reaction time and increases the polymerization rate during the production of final nanocomposite. The samples were characterized using Fourier transform infrared and Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nuclear magnetic resonance spectroscopy besides energy-dispersive X-ray spectroscopy (EDS) combined with SEM (SEM–EDX). In addition, thermal behavior of nanocomposite was perused by differential scanning calorimetry and thermogravimetric analysis. XRD and AFM results show proper dispersion of clay in PETS matrix and SEM–EDX results demonstrate suitable distribution of clay in polymer matrix. PETS/nanoclay nanocomposite show a better thermal stability, and also higher glass transition and melt temperature compared to pure polysulfide polymer. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (nanoclay) deals.

Transport Limitations during Phase Transfer Catalyzed Ethyl-Benzene Oxidation: Facts and Fictions of “Halide Catalysis”

The mechanistic interpretation of the catalytic effect of phase transfer catalysts in the selective oxidation of ethyl benzene is hampered by mass transfer effects. We demonstrate that proper experiments lead to a more correct interpretation of the role of the quaternary ammonium salt (QAS) and its counterion. Specifically, experiments unequivocally show that the main action of the counterion is to enhance physical mass transfer processes, while its catalytic effect is limited to a shift in selectivity, not activity. The QAS as a whole accelerates the induction process in the ethyl benzene (EB) oxidation by degenerate branching of its hydroperoxide (EBHP). Proper mechanistic understanding of these phenomena in QAS catalysts is especially crucial under industrially relevant conditions

Characterization of synthesized poly(aryldisulfide) through interfacial polymerization using phase-transfer catalyst

A new polysulfide polymer was synthesized from 1,4-bis(chloromethyl)-benzene and sodium disulfide by an interfacial polycondensation technique in the presence of tetrabutyl ammonium bromide, methyltributyl ammonium chloride and benzyl triethyl ammonium chloride as phase-transfer catalysts (PTC). The effect of PTC on the kinetics of polymerization was investigated. Structures of this aromatic polysulfide were confirmed through elemental analyses, attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, an X-ray diffraction technique, and a nuclear magnetic resonance spectroscopy method. The thermal behavior of this polymer was also characterized by differential scanning calorimetry and thermogravimetric analysis. The solubility of prepared polymer was critically dependent on the identity of the solvent.

Effect of a Phase Transfer Catalyst on the Dynamics of an SN2 Reaction. A Molecular Dynamics Study

The effect of a tetramethylammonium cation phase transfer catalyst on the benchmark Cl− + CH3Cl reaction at the water/chloroform liquid/liquid interface is investigated by a molecular dynamics-empirical valence bond (EVB) model. The effect of the catalyst on the reaction free energy profile at different interface locations and in bulk chloroform is examined. We find that, because of significant water “pollution”, activation of the nucleophilic attack is limited to the bulk organic region. The barrier height at the interface is equal to or slightly larger than the barrier in bulk water and is unaffected by the presence of the catalyst. In bulk chloroform, our calculations suggest that the barrier height, which is much lower than in bulk water, moderately increases when a few water molecules interact with the system and when the catalyst forms an ion-pair with the nucleophile. Thus, the catalyst is most effective if its role is limited to bringing the nucleophile to the bulk organic phase.

Microwave assisted phase-transfer catalytic ethoxylation of p-chloronitrobenzene—A kinetic study

p-Ethoxynitrobenzene was synthesized by the reaction of p-chloronitrobenzene with potassium ethoxide in a homogeneous system using benzyltriethylammonium chloride (BTEAC, QCl) as a phase-transfer catalyst at 50 °C under microwave irradiation conditions. The use of phase-transfer catalysts and microwave has been compared and demonstrated in this nucleophilic substitution reactions. The kinetics of the reaction depends on the effect of phase-transfer catalysts, amount of catalyst, amount of potassium hydroxide, volume of ethanol and temperature on the conversion of the reaction were investigated.

Tungsten-based catalysts for the oxidation of cyclohexanol: The effect of phase transfer catalysts

The oxidation of cyclohexanol with hydrogen peroxide in the presence of tungsten-based catalysts was studied in this paper. The effect of phase transfer catalysts was discussed and clarified. [CTA]9[SbW9O33] showed the best activity and good recyclability with a conversion over 95%.

Emulsion‐induced ordered microporous films using amphiphilic poly(ethylene oxide)‐block‐poly(n‐butyl isocyanate) block copolymers

AbstractWell‐defined poly(ethylene oxide)‐block‐poly(n‐butyl isocyanate) (PEO‐block‐PBIC; AB) diblock copolymers were prepared with trichloropentadienyl titanium (IV) (CpTiCl3) catalyst. Ordered microporous films (hexagonal pattern) were constructed by emulsion micelles of A110B230 diblock copolymer (the subscript indicates the degree of polymerization of each block component) formed from CHCl3/H2O/tetrahydrofuran (THF) = 100/5/10 (v/v) solution. The addition of THF promoted uniform micelles in immiscible CHCl3/H2O mixed solvent as well as the effect of phase transfer catalyst. Diblock copolymers formed spherical micelles, consisting of a PEO core and a PBIC corona. At some concentration, interaction between micelles forced a disorder–order transition, resulting in freezing of micelles in some superlattice. Subsequently, the leaving gaps among micelles were filled by PBIC block chains on a corona through the evaporation of organic solvents. At last, water within hydrophilic PEO core was vomited through the film matrix. We also constructed the microporous films using A110B230 diblock copolymer by the current water‐assisted method. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Kinetics and Process Parameter Studies in Oxidative Chlorination of 4-Methylphenol under Phase-Transfer Conditions

The effect of phase-transfer catalysts on the rate and selectivity of oxidative chlorination of 4-methylphenol was studied in ethylenedichloride with HCl−H2O2. Under identical reaction conditions, the rate of oxidative chlorination increased 6−7-fold in the presence of a phase-transfer catalyst (PTC) like tetraheptylammonium chloride in comparison to an ordinary two-phase system with no PTC. The activation energy was found to be 78 kJ/mol, and the reaction was found to be first-order on 4-methylphenol. An appropriate mechanism has been proposed.

Synergetic Effect of Two Kinds of Phase Transfer Catalysts in Third Phase for Dehydrohalogenation of 2-Bromooctane.

Dehydrohalogenation of 2-bromooctane in the organic phase with dodecane solvent by using phase transfer catalysts (PTC) was carried out in a batch reactor with potassium hydroxide solvent in the aqueous phase. A synergetic effect of PTC was observed for the combination of tetrahexyl ammonium bromide ((Hex)4NBr) and polyethylene glycols (PEG) in the third phase. The observed reaction rate constant (kobs), which is determined from the first order kinetics, depends on the average molecular weight of PEG, and remarkably increases with the increasing KOH concentration in the aqueous phase. If the optimum combination of (Hex)4NBr and PEG with average molecular weight of 200 (PEG200) is used, the amount of quaternary ammonium salt can be significantly saved (for example, by one-nineteenth).The volume of the third phase and the concentration of water in the third phase (CH2O) were measured and related to the reaction rate constant as well as the distribution coefficient (KA).Catalysts which exist in the third phase can be reused without any loss of catalytic activity.

Rate enhancements in a solid-liquid reaction using PTC, microphase, ultrasound and combinations thereof

A phase transfer catalyst (PTC) provides an elegant and efficient way of effecting reaction between components present in two immiscible phases: liquid-liquid and liquid-solid. Such reactions can also be initiated or enhanced by other strategies, such as use of a microphase or ultrasound. Results are reported in this paper on rates and rate enhancements in a model solid-liquid reaction (synthesis of benzyl sulfide from benzyl chloride and sodium sulfide in a suitable organic solvent) in the presence of PTC, microphase, and ultrasound. The study is then extended to include the effects of combinations of these stragegies. A preliminary kinetic analysis of the results is also attempted. For the system studied it is found that the accelerating effect of PTC is the most profound, while that of microphase or ultrasound is only marginal when they are used individually. On the other hand, the effects of microphase and ultrasound acquire far greater significance in the presence of PTC.

Rate enhancements in a solid-liquid reaction using PTC, microphase, ultrasound and combinations thereof

A phase transfer catalyst (PTC) provides an elegant and efficient way of effecting reaction between components present in two immiscible phases: liquid-liquid and liquid-solid. Such reactions can also be initiated or enhanced by other strategies, such as use of a microphase or ultrasound. Results are reported in this paper on rates and rate enhancements in a model solid-liquid reaction (synthesis of benzyl sulfide from benzyl chloride and sodium sulfide in a suitable organic solvent) in the presence of PTC, microphase, and ultrasound. The study is then extended to include the effects of combinations of these stragegies. A preliminary kinetic analysis of the results is also attempted. For the system studied it is found that the accelerating effect of PTC is the most profound, while that of microphase or ultrasound is only marginal when they are used individually. On the other hand, the effects of microphase and ultrasound acquire far greater significance in the presence of PTC.

Effect of phase transfer catalysts on the interfacial tension of water/toluene system

L'effet de la tension interfaciale du binaire toluene-eau a ete etudie a 25°C en presence de quatre catalyseurs de transfert de phase: le chlorure d'ammonium de tricaprylmethyle, le chlorure d'ammonium d'hexadecyltrimethyle, le bromure d'ammonium d'hexadecyltrimethyle et le bromure de phosphonium d'hexadecyltributyle. La tension interfaciale d'un melange de phenol aqueux et de resorcinol-toluene en presence et en l'absence de chlorure d'ammonium de tricaprylmethyle est egalement indiquee. On s'est efforce de comprendre le changement dans la vitesse volumetrique d'extraction avec differents catalyseurs pour deux reactions de phase, en s'appuyant sur la tension interfaciale

Effect of phase transfer catalyst on CO substitution of Mo(CO)6

The effect of Q+ OH- was studied, which is formed in NaOH solution used for anion exchange with PTC, on CO substitution of molybdenum hexacarbonyl complex by strong electron donating ligand, 2,2’-bipyridine. The change of product yield was discussed according to the amount and types of solvent and PTC, their compositions, reaction temperature and time, and different cation and anion of PTC.

The effect of phase-transfer catalysts on polysilane formation

Augmentation du rendement, meilleure reproductibilite du rendement et de la distribution de masse moleculaire par addition de 15 crown 5 dans le milieu dans le cas de la polymerisation par reaction de Wurtz du dichloro hexyl methyl silane et du dichloro methyl phenyl silane. Effet similaire d'un cryptand (Kryptafix 222) mais avec degradation du polymere par prolongation de la reaction

Fast and very slow reactions: phase transfer catalysis

The effect of phase transfer catalysts (PTC), such as tricaprylmethyl ammonium chloride (Aliquat-336), cetyl trimethyl ammonium bromide, etc. on the rate of alkaline hydrolysis of different formate and acetate esters was studied. In the case of formate esters extraction is accompanied by fast pseudo-first order reaction in diffusion film; for acetate esters the reaction is insufficiently fast to occur in the diffusion film. The values of the volumetric rate of extraction, R A a, and the specific rate of extraction, R A , with or without PTC, were measured in a fully baffled mechanically agitated contactor and a constant interfacial area stirred cell, respectively. The alkaline hydrolysis reaction was carried out with aqueous solutions of sodium hydroxide or aqueous lime slurry and the effect of speed of agitation and PTC concentration on the rate of hydrolysis was studied. A remarkable increase in the value of R A was realized in the presence of PTC and the enhancement factor for the formate ester hydrolysis reaction ranged from 20 to over 200.

Inhibition by phase transfer catalysts

While phase transfer catalysts have generally a positive effect on substitution of halides by rhodanide ion in two-phase reaction systems changing the structure of alkyl halide from primary to tert.-alkyl groups, catalysis reverses into inhibition. The assumption that this is due to the change in reaction mechanism from SN2 to SN1 was proved on hydrolysis of triphenylmethyl chloride in a two-phase system, where the inhibitory effect of phase transfer catalysts is even more pronounced.

The effect of phase transfer catalysts on the Reimer-Tiemann reaction

Quaternary ammonium salts were found inactive as phase transfer catalysts in the Reimer-Tiemann reaction. Tertiary amines, on the other hand, proved to have significant effect on the process.