Tetrapropylammonium Bromide Research Articles

Measurement and Correlation of Isothermal Vapor−Liquid Equilibrium Data for the System Acetonitrile + Water + Tetrapropylammonium Bromide

Isothermal vapor−liquid equilibrium data for the system acetonitrile + water + tetrapropylammonium bromide at four constant salt molalities [(0.200, 0.400, 0.800, and 1.000) mol·kg-1] have been measured with the help of headspace gas chromatography at (298.15 and 323.15) K. The experimental data were correlated using two different electrolyte models: an electrolyte nonrandom two-liquid model and an electrolyte universal quasi-chemical functional-group activity coefficients model. Mean absolute deviations of vapor phase compositions for these models were 0.006 and 0.007, respectively.

Tertiary amine-mediated synthesis of microporous carbon membranes

Microporous carbon membranes were prepared on an α-alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO 2, O 2, N 2, CF 4, n-C 4H 10 and i-C 4H 10, as well as binary mixtures of CH 4/ n-C 4H 10 and N 2/CF 4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH 4/ n-C 4H 10 mixtures and higher than 8100 for the N 2/CF 4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.

Influence of synthesis parameters on vanadium-silicalite-1 crystal growth prepared with fluoride-containing media

Vanadium-silicalite-1 samples are readily prepared at 170 °C from fluoride-containing gels. The amounts of vanadium and fluoride salts were varied in gels of initial composition 10SiO 2: xVO 2:1.25TPABr: yMF:330H 2O with the vanadium source=VOSO 4, V 2O 5, VO(acac) 2 and 0.0 5 ⩽ x ⩾ 3.0 ; M=NH 4, Na, K and y = 1 , 3, 5, 7, 10 and TPABr=tetrapropylammonium bromide. The influence of synthesis parameters (Na/Si, MF/Si, Si/V, the vanadium source) on the preparation of well-formed crystals was systematically investigated. Sodium and potassium cations show different behaviours with respect to ammonium ions on the crystallization rates and crystal aspect ratios. Crystal morphologies are strongly influenced by the nature of the fluoride salt added to the reaction mixture. The vanadium incorporation in zeolite crystals increases regularly with the initial transition metal and fluoride content in the reaction batch. Moreover, the vanadium incorporation is similar for the various salts used. The kinetic data show that the vanadium fluoride amount not only influences the reaction rates, but also the induction periods.

Novelties of kinetics of chemoselective reduction of citronellal to citronellol by sodium borohydride under liquid–liquid phase transfer catalysis

Borohydride reductions, although common, have not been studied from kinetic and mechanistic view points due to complex chemistry and more so, there is no report on kinetics and mechanism of such reductions under phase transfer catalysis. The novelties of phase transfer catalysed chemoselective reduction of citronellal to citronellol using sodium borohydride were studied in detail in liquid–liquid phase transfer catalysis using tetrabutylammonium bromide (TBAB), tetrapropylammonium bromide (TPAB), tetraethyl ammonium bromide (TEAB) and tetrabutylammonium hydrogen sulfate (TBAHS). TBAB was the best catalyst at 30 °C. Citronellol is very extensively used in a number of perfume compositions. The effects of different parameters such as speed of agitation, phase volume ratio, catalyst concentration, sodium borohydride concentration, citronellal concentration and temperature have been studied. The reaction was found to be 100% selective towards the formation of the desired product. The kinetics and mechanism are presented to account for the effects of various parameters on conversion and rates. It was possible to establish both rate constant and distribution constant from the same set of data. The results are novel.

Ion-solvent and ion-ion interactions of some tetraalkylammonium, alkali metals and ammonium halides in isoamyl alcohol at 298.15 K by conductometric technique

Precise conductance measurements are reported for tetramethylammonium chloride (Me 4 NCl), tetraethylammonium bromide (Et 4 NBr), tetrapropylammonium bromide (Pr 4 NBr), tetrabutylammonium bromide (Bu 4 NBr), tetrabutylammonium iodide (Bu 4 NI), lithium bromide (LiBr), sodium iodide (Nal) and ammonium bromide (NH 4 Br) in isoamyl alcohol at 298.15 K. The conductance data have been analyzed by the Fuoss conductance-concentration equation in terms of the limiting molar conductance (A 0 ), the association constant (K A ) and the distance of the closest approach of ions (R). The results have been explained in terms of ion-solvent and ion-ion interactions.

Catalytic and multinuclear MAS NMR studies of a thermally treated zeolite ZSM-5

Catalysts of ZSM-5 type were obtained by synthesis with tetrapropyl-ammonium-bromide (TPABr) as a template and subsequent hydrothermal treatment up to 1173 K. 1H-, 27Al-, and 29Si-NMR spectroscopy and the direct oxidation of benzene with N 2O as a catalytic test were applied to characterize the products. 27Al MAS NMR and 27Al 3QMAS NMR studies of the samples give evidence that fivefold-coordinated extra-framework aluminum species exist if the product is treated at 1173 K and then rehydrated. The values of all characteristic catalytic key data are highest when the catalysts are precalcined at 1173 K. This is a clue that species giving rise to fivefold-coordinated aluminum species in the hydrated products are responsible for the high catalytic key data. The nature of these species is not yet clear. Two models for the species are in agreement with our experimental findings.

Synthesis of Fe‐loaded MFI zeolite using silatrane as precursor and its CO activity

AbstractFe‐MFI zeolite was successfully synthesized using silatrane as precursor and tetrapropyl ammonium bromide as template via the sol–gel process and microwave heating technique. The effects of ageing time, heating temperature, heating time and iron concentration were investigated, and it was found that Fe‐MFI synthesis favors higher heating temperatures, but is limited by the degradation of the incorporation of a template molecule. Moreover, longer ageing and heating times promote the incorporation of higher amounts of iron atom in the MFI structure. However, too long an ageing time decreases the incorporation of iron. The lower the percentage Fe loading, the greater the percentage of Fe3+ ions incorporated into the MFI framework. The catalytic activity of Fe‐MFI catalyst for the oxidation of CO was studied and it was found that these synthesized catalysts catalyzed the oxidation of CO very well. Copyright © 2005 John Wiley & Sons, Ltd.

Synthesis of silica hollow spheres assisted by ultrasound

A simple and effective method for synthesizing silica hollow spheres is presented. The synthesis utilizes vesicles from oppositely charged surfactants sodium dodecyl sulfate (SDS) and tetrapropylammonium bromide (TPAB) aqueous solution as template for the silica growth. Tetraethyl orthosilicate (TEOS) is added to the vesicular template as a precursor for the silica formation. Ultrasound was employed to accelerate the formation of vesicles template. The morphology of the silica spheres is uniform and well-defined (diameter: 200 nm–5 μm, wall thickness: 50 nm). The product was also characterized by FTIR, TG-DTA, N 2 adsorption. TEM images reveal that the spheres have structure stability after calcinations at 550 °C.

Synthesis of TS-1 using amorphous SiO 2 and its catalytic properties for hydroxylation of phenol in fixed-bed reactor

Titanium silicalite-1 (TS-1) has been synthesized using amorphous SiO 2 as silicon source and tetrapropylammonium bromide (TPABr) as template. The effects of preparation parameters, such as silicon sources, crystallization temperature and time, aging time, H 2O/SiO 2, SiO 2/TiO 2, TPABr/SiO 2 and n-butylamine (NBA)/SiO 2, and nonionic surfactants on the physicochemical and catalytic properties of TS-1 were investigated in detail. The TS-1 samples were characterized by XRD, FT-IR, UV–vis, SEM, ICP-AES and N 2 adsorption. In the fixed-bed reactor, the catalytic property of TS-1 for the phenol hydroxylation was tested. The studies show that the catalytic performance of TS-1 synthesized using amorphous SiO 2 is close to that of the samples prepared with tetraethyl orthosilicalite (TEOS) for the phenol hydroxylation with H 2O 2. The crystallinity of the sample increases with an increase of the crystallization temperature, crystallization time, the ratio of SiO 2/TiO 2, SiO 2/H 2O and NBA/SiO 2. TS-1 with smaller crystals can be obtained by increasing aging time, H 2O/SiO 2 and NBA/SiO 2, and using the nonionic surfactants. Moreover, adding the nonionic surfactants in the matrix gel can increase the amount of Ti incorporated in framework of zeolite and reduces the amount of TiO 2 in an extra framework.

Electrical Conductances of Tetraethylammonium Bromide and Tetrapropylammonium Bromide in 2-Ethoxyethanol (1) + Water (2) Mixtures at (308.15, 313.15, 318.15, and 323.15) K

The electrical conductances of the solutions of tetraethylammonium bromide (Et4NBr) and tetrapropylammonium bromide (Pr4NBr) in 2-ethoxyethanol (1) + water (2) mixed solvent media containing 0.25, 50, and 0.75 mass fractions of 2-ethoxyethanol (w1) have been reported at (308.15, 313.15, 318.15, and 323.15) K. The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA), and the association diameter (R). These two electrolytes are found to exist essentially as free ions in the solvent mixtures with w1 = 0.25 and 50 over the entire temperature range; however, slight ionic association was observed in the mixed solvent medium richest in 2-ethoxyethanol. The electrostatic ion−solvent interaction is found to be very weak for the tetraalkylammonium ions in the aqueous 2-ethoxyethanol mixtures investigated.

Hydrolysis‐improved thermosensitive polyorganophosphazenes with α‐amino‐ω‐methoxy‐poly(ethylene glycol) and amino acid esters as side groups

AbstractA series of hydrolysis‐improved thermosensitive polyorganophosphazenes with α‐amino‐ω‐methoxy‐poly(ethylene glycol) (AMPEG) and amino acid esters (AAEs) of ‘N,N‐systems’ was synthesized, and their properties were evaluated in comparison with the thermosensitive polyorganophosphazenes with methoxy‐poly(ethylene glycol) (MPEG) and AAEs of ‘O,N‐systems’, by means of 31P NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Most of the present polymers showed a lower critical solution temperature (LCST) in the range 32.0–79.0 °C, depending on the kinds of AAE, length of AMPEG and the mol ratio of the two substituents. These polymers exhibited higher LCSTs and faster degradation rates than the MPEG‐based polymers. The aqueous solution of poly(ethyl glycinate phosphazene)‐graft‐poly(ethylene glycol) [NP(GlyEt)0.94(AMPEG350)1.06]n did not show an LCST, which is presumed to be due to its high hydrophilicity, in contrast to [NP(GlyEt)1.01(MPEG350)0.99]n which showing an LCST at 77.5 °C. On the other hand, the polymers with a high content of AAE or with hydrophobic amino acids such as L‐aspartic acid and L‐glutamic acid, have shown a similar LCST to those of the MPEG‐based polymers. The half‐lives (t1/2) for hydrolysis of [NP(AMPEG350)1.06(GlyEt)0.94]n at pH 5, 7.4 and 10 were 9, 16, and 5 days, respectively, which are almost 2.5 to 4 times faster than that of the MPEG‐based polymers. The LCST of the present N,N‐polymers has been shown to be more influenced by salts such as NaCl (‘salting‐out’ effect) and tetrapropylammonium bromide (TPAB) (‘salting‐in’ effect) compared with the ‘O,N‐system’. Such differences of the ‘N,N‐systems’ from the ‘O,N‐systems’ in thermosensitivity, hydrolysis behavior and salt effect seem to be due to the higher hydrophilicity of the amino group in AMPEG. Copyright © 2005 Society of Chemical Industry

Viscosities of some tetraalkylammonium bromides in 2-ethoxyethanol at 308.15, 313.15, 318.15, and 323.15 K

The viscosities of the solutions of tetraethylammonium bromide (Et4NBr), tetrapropylammonium bromide (Pr4NBr), tetrabutylammonium bromide (Bu4NBr), tetrapentylammonium bromide (Pen4NBr), and tetraheptylammonium bromide (Hep4NBr) in 2-ethoxyethanol have been reported at 308.15, 313.15, 318.15, and 323.15 K. The viscosity data have been analyzed by the Jones–Dole equation for the associated electrolytes to evaluate the viscosity B coefficients of the electrolytes. These data have also been analyzed by the transition-state treatment to obtain the contribution of the solutes to the free energy of activation for viscous flow of the solution. The viscosity of the solvent is found to be greatly modified by the presence of all of the tetraalkylammonium ions investigated. Moreover, the tetraalkylammonium ions are found to be unsolvated in 2-ethoxyethanol solutions, they behave neither as structure-breaker nor as structure-maker and the formation of the transition state is made less favorable in their presence.Key words: viscosity, electrolytes, tetraalkylammonium ion, 2-ethoxyethanol, ionic contribution, solvation, transition-state treatment.

Some New Features on Synthesis of Titanium Silicalite-1 in a Non-TPAOH Inorganic Reactant Synthetic System

Various effects on the synthesis of titanium silicalite-1 (TS-1) were discussed in the non-TPAOH (tetrapropyl ammonium hydroxide) inorganic reactant synthesis system, in which cheap colloidal silica and TiCl3 aqueous solution, TiCl4 were used as the silicon and titanium sources, respectively, TPABr (tetrapropyl ammonium bromide) as the template reagent, and weak organic bases as the base source to provide the alkalinity needed for crystallization. The influence of diverse synthesis parameters such as different base sources, SiO2/TiO2 ratio, silicon source, titanium source, amounts of template, N2 protection, seed crystals, aging period, amount of water, crystallization temperature, and crystallization time have been investigated in detail.

Organic‐Templating Approach to Synthesis of Nanoporous Silica Composite Membranes (II): MTES‐Templating and CO2 Separation

Nanoporous silica composite membranes for gas separation have been synthesized by the organic‐templating sol‐gel technique and their CO2/N2 separation efficiency has been investigated. Stable organic‐templating silica sols capable of coating nanoporous amorphous silica layers on SiO2/α‐Al2O3 composite supports were prepared by the two‐step acid‐catalytic process using the mixture of TEOS and template such as MTES (methyltriethoxysilane) being covalently bonded with TEOS or TPABr (tetrapropylammonium bromide) non‐reacted. The SiO2/α‐Al2O3 composite supports (pore size 1.6 nm) prepared by pressurized coating of the porous α‐alumina tube with a nanoparticulate silica sol were found to be more suitable than pure α‐Al2O3 composite supports for synthesizing crack‐free membranes which have the high CO2/N2 separation efficiency. The N2 permeability of organic‐templated silica composite membranes synthesized was about 10−8 mol/m2 · s · Pa and the CO2/N2 separation factor of the MTES‐templated silica composite membranes was enhanced up to 19 at room temperature by surface‐modifying the templated silica membrane with the TEOS‐EtOH solution.

Microporous carbons prepared from cationic surfactant–resorcinol/formaldehyde composites

Microporous carbons have been synthesized by the carbonization of cationic surfactant–resorcinol/formaldehyde (RF) composites, which were themselves formed by electrostatic organic–organic interaction. The porous structure produced by the decomposition of the surfactant plays an important role for the gasification of the RF polymer at higher temperatures. The pore size of the carbon prepared from tetrapropylammonium bromide (TPAB)–RF, cetyltrimethylammonium bromide (C 16TAB)–RF and decyltrimethylammonium bromide (C 10TAB)–RF mixtures can be estimated as 0.53 nm from the Horvath–Kawazoe method using N 2 adsorption isotherms. Their pore size distributions were very narrow, showing that the microporous carbons derived from surfactant–RF mixture may have promise as adsorbents and membrane materials.

Conductometric Study of Some Tetraalkylammonium Bromides in 2-Ethoxyethanol in the Temperature Range 35–50 °C

Abstract The electrical conductances of the solutions of four tetraalkylammonium bromide salts (R4NBr), namely tetraethylammonium bromide (Et4NBr), tetrapropylammonium bromide (Pr4NBr), tetrapentylammonium bromide (Pen4NBr) and tetraheptylammonium bromide (Hep4NBr) in 2-ethoxyethanol have been reported at 35, 40, 45 and 50 °C. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ0), the association constant (K A) and the association diameter (R). The ionic contributions to the limiting molar conductance have also been estimated. Appreciable ionic association was observed for all of these electrolytes in 2-ethoxyethanol. The tetraalkylammonium ions (R4N+) were found to remain scarcely solvated in the present solvent medium within the temperature range investigated here. The solvation of the bromide ion in these tetraalkylammonium bromide is found to be weakened as soon as the ion-pairs are formed. An increase in the temperature results in a lower level of ion-pairing for each of these salts.

Synthesis of ZSM-5 zeolite from lignite fly ash and rice husk ash

The lignite fly ash from the Mae-Moh power plant, Thailand, and rice husk ash were used as raw materials for ZSM-5 zeolite synthesis. Factors affecting the yield of ZSM-5 zeolite synthesized from fly ash, i.e., the SiO 2/Al 2O 3 mole ratio, the presence of tetrapropyl ammonium bromide (TPABr, the structure-directing material for ZSM-5 zeolite synthesis), the holding temperature and time, and the initial pressure were investigated. It was found that without TPABr only zeolite P could be synthesized at SiO 2/Al 2O 3 mole ratios of 2.8–200. In order to synthesize ZSM-5 zeolite, sodium silicate solution was added to adjust the SiO 2/Al 2O 3 mole ratio in raw ash. The yield of ZSM-5 zeolite was as high as 59 wt.% when following conditions were used: SiO 2/Al 2O 3 mole ratio, 40; the holding temperature, 210 °C; the holding time, 4 h and the initial pressure, 4 bar. The catalytic performance for CO 2 hydrogenation reaction of the ZSM-5 zeolite was preliminary tested and compared with that of commercial one. It was observed that there was no significant difference in the catalytic performance between these two catalysts.

Ultrasonic velocities and isentropic compressibilities of some symmetrical tetraalkylammonium and alkali-metal salts in N, N-dimethylacetamide–water mixture at 298.15 K

The ultrasonic velocities of tetraethylammonium bromide (Et 4NBr), tetrapropylammonium bromide (Pr 4NBr), tetrabutylammonium bromide (Bu 4NBr), tetrapentylammonium bromide (Pen 4NBr), sodium tetraphenylborate (NaBPh 4), and sodium bromide (NaBr) in N, N-dimethylacetamide+water (50% v/v) mixture have been measured in the concentration range 0.01–0.10 mol dm −3 at 298.15 K. Apparent molar isentropic compressibilities ( κ φ ) of these electrolytes were derived from these data supplemented with their density values. The limiting apparent molar isentropic compressibilities ( κ φ 0) have been obtained by the method of extrapolation from the linear plots of apparent molar isentropic compressibilities ( κ φ ) against the square root of the molal concentration. The limiting apparent molar isentropic compressibility ( κ φ 0) values were separated into approximate limiting ionic compressibilities ( κ φ± 0) on the basis of the assumption that the limiting ionic compressibility of the bromide ion is zero. The results have been interpreted in terms of electrostriction and penetration effects.

Synthèse et caractérisation des zéolithes de type ZSM-5

Synthesis and characterization of ZSM-5 zeolites. The purpose of this work is the synthesis of the ZSM-5-type zeolite by varying the Si/Al ratio and the length of the alkyl chain of the template by using tetrapropylammonium bromide, tetrabutylammonium bromide and tetramethylammonium bromide. The obtained zeolites were characterized by X-ray diffraction and electron microscopy. The X-ray diffraction patterns of samples A (TPA, Si/Al = 36), B (TPA, Si/Al = 60) and C (TPA, Si/Al = 120) indicated a pure zeolite ZSM-5, with however different morphologies. On the other hand, the X-ray diffraction patterns as well as the micrograph of sample F (TPA, Si/Al = 30), show a mixture of phases. The X-ray diffraction patterns of the samples D (TBA, Si/Al = 30) and E (TMA, Si/Al = 30) also indicated a mixture of phases. To cite this article: A. Soualah et al., C. R. Chimie 7 (2004) .

Effect of quaternary ammonium salts on the hydrolysis of N-glutaryl- l-phenylalanine catalysed by α-chymotrypsin

The hydrolysis of N-glutaryl- l-phenylalanine p-nitroanilide catalysed by α-chymotrypsin (α-CT) was studied in the presence of the following quaternary ammonium salts: tetrapentyl ammonium bromide (TPeABr), tetrabutyl ammonium bromide (TBABr), tetrapropyl ammonium bromide (TPABr), tetraethyl ammonium bromide (TEABr) and tetramethyl ammonium bromide (TMABr). The activity of the enzyme is strongly affected by the salts that act as activators. Superactivity has been detected in the presence of TPeABr, TBABr, TPABr and TEABr. The enzyme activity seems to depend on the molecular structure of the salts; the higher the molecular weight of the alkyl residues in the cationic ammonium group, the higher the superactivity. In the whole investigated range, the enzyme hydrolysis rate resulted to be a monotonic increasing function of the salt concentration. The model of a non-essential activator was adopted to describe the effect of the salts on the hydrolysis activity and good agreement was found between the experimental results and the model predictions. The dependence of the enzyme activity on the substrate concentration was also studied to further verify the applicability of the model. Finally, a preliminary study about the effect of these additives on α-chymotrypsin thermal stability was performed.