Tetrapropylammonium Bromide Research Articles

Synthesis of pyrazolopyridine and pyrazoloquinoline derivatives by one-pot, three-component reactions of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide

Abstract Pyrazolopyridine and pyrazoloquinoline derivatives were obtained by a one-pot, three-component reaction of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide at 80°C in water through Knoevenagel and Micheal reactions, followed by intramolecular condensation, unexpected dearoylation and oxidation. Mild reaction conditions, high yields, simplicity of work up procedure, starting materials availability and clean product formation are some of the main advantages of this synthetic strategy.

Synthesis of Indeno[1,2-b]benzofurans using TPAB as Highly Efficient and Recoverable Catalyst

Herein we report the synthesis of some novel indeno[1,2-b]benzofuran derivatives by reaction of ninhydrin with cyclic 1,3-dicarbonyl compounds including cyclopentane-1,3-dione, cyclohexane-1,3-dione, dimedone, 4,4-dimethylcyclohexane-1,3-dione, meldrum's acid, barbituric acid, thiobarbituric acid, 1,3-dimethylbarbituric acid and indane-1,3-dione. We also used tetra-propylammonium bromide (TPAB) as an organocatalyst. Keywords: Cyclic 1,3-dicarbonyl compounds, ninhydrin, indeno[1,2-b]benzofurans, TPAB.

One‐pot, Three‐component Synthesis of a Series of New Bis‐pyrrolo[2,3‐d]pyrimidines in the Presence of TPAB under Reflux Conditions

A one‐pot, three‐component reaction of 1,4‐phenylene‐bis‐glyoxal, 6‐aminouracils, and dimedone or barbituric acid derivatives in the presence of tetrapropylammonium bromide (5 mol%) in ethanol under reflux conditions gave a series of new bis‐pyrrolo[2,3‐d]pyrimidine derivatives in high yields.

Environmentally benign non-fluoro deep eutectic solvent and free-standing rice husk-derived bio-carbon based high-temperature supercapacitors

Deep eutectic solvents (DESs) have been emerging as newer environmentally benign electrolytes for energy storage devices with the high-temperature operational capability. For the first-time, we propose ethylene glycol and tetrapropylammonium bromide based non-fluoro DESs as electrolytes for the supercapacitor. Different compositions of DESs were also evaluated. Also, the high-temperature operational capability of the proposed electrolytes was evaluated with the free-standing microporous commercial activated carbon (AC) and mesoporous rice husk-derived bio-activated carbon (Bio-AC). The maximum cell voltages of 1.3 V and 1.0 V are identified for AC and Bio-AC based supercapacitors, respectively at 25 °C. The specific capacitances of both AC and Bio-AC electrodes are ∼100 F g−1 at 0.1 A g−1. The proposed DES electrolyte can be operated at the maximum temperature of 115 °C, which is higher than the previously reported DESs (80 °C). The specific capacitance increases with increasing temperature, and the maximum specific capacitance of an electrode is 172 F g−1 at 115 °C for Bio-AC supercapacitor. Excellent long-term stability is noted after 10,000 cycles at 25 °C and 115 °C for both AC and Bio-AC supercapacitors. The supercapacitors here may be practically used in high-temperature applications.

Isomerization of hydrocarbons over Pt supported on micro-mesoporous ZSM-5

Nanosized ZSM-5 with different Si/Al ratios, possessing both micro and mesopores, were synthesized by a hydrothermal method using tetrapropyl ammonium bromide (TPABr) as a template. The synthesised materials were characterized by different characterization methods to evaluate the phase purity, particle size, morphology, textural properties and acid strength. Pt (0.5 wt%) was loaded on the calcined (at 500 °C) ZSM-5 samples and evaluated for the isomerization of n-pentane, n-hexane and light naphtha. ZSM-5 as a catalyst showed higher conversions in comparison to other prepared zeolites with different SiO2/Al2O3 ratios. In addition, the ZSM-5(5.4) catalyst exhibited considerably higher conversions under most conditions. The reaction temperature, pressure, WHSV and H2 flow are key factors for this novel isomerization. The obtained results may have a great prospective in useful applications for humankind. In addition, the mechanism of the n-pentane, n-hexane and light naphtha isomerizations over the ZSM-5 zeolites was considered by density functional theory (DFT), using the cluster modeling approach.

Properties Modification of Nanosized Hollow Zeolite Crystals by Desilication

AbstractA strategy to modify the properties of hollow zeolite was developed by leaching the “parent” zeolite in alkaline solution. A systematic study was performed to identify the effect of both the synthesis conditions of “parent” zeolite and the leaching conditions on the properties of hollow zeolite. Fine‐tuning the leaching conditions, i. e. the concentration of sodium hydroxide solution, allows control over the degree of hollowness of the zeolite, achieving the introduction of larger voids in different locations of individual crystals, which is a key factor if the crystals are to be used for catalytic applications. In addition, a hypothesis was proposed to explain the formation of hollow ZSM‐5 crystals. By replacing part of tetrapropylammonium hydroxide (TPAOH) with tetrapropylammonium bromide (TPABr) as the structure‐directing agent (SDA), the “parent” zeolites obtained were less stable in alkaline solution and formed hollow structures more easily. The size of hollow zeolite crystals could be easily controlled by adjusting the water content of the synthesis gel. Finally, crystals with double shells were prepared by a method involving two consecutive crystallizations followed by base leaching. Overall, fine‐tuning of zeolite synthesis and post‐synthesis conditions leads to control of the structure of hollow zeolite crystals.

IM-5 Zeolite Treated with Mixed Solution of NaOH and TPABr: Characterization and Application for Alkylation of Benzene with Ethanol

IM-5 series zeolites (I-xat-0.05TPABr) were prepared by treating the pristine IM-5 zeolites in a mixed solution of NaOH and TPABr (tetrapropylammonium bromide) with different NaOH concentrations (CNaOH). It was found the porosity and acidity of modified IM-5 zeolite changed obviously with CNaOH. When used for alkylation of benzene with ethanol, the modified I-xat-0.05TPABr exhibited better reaction stability than the unmodified IM-5 zeolite, and I-0.5at-0.05TPABr showed the best stability. Typically, the reaction stabilities of I-xat-0.05TPABr catalysts were directly related to the hierarchical factor, besides the carbon deposition rate.

A Facile Synthesis of Xanthene‐1,8(2H)‐dione Derivatives by Using Tetrapropylammonium Bromide as Catalyst

Several new derivatives of 9‐aroyl‐3,4,5,6,7,9‐hexahydro‐1H‐xanthene‐1,8(2H)‐dione have been synthesized in yields varying from high to excellent by the condensation reaction of arylglyoxals with 1,3‐diketones (cyclohexane‐1,3‐dione or dimedone) and TPAB as an inexpensive, recoverable, and non‐toxic catalyst in the presence of ethanol/water under reflux conditions.

Salting-in and salting-out effects of organic and inorganic ammonium salts on the aqueous polymer solutions

This paper accomplishes a broad survey of the salting effects of different ammonium salts on the aqueous polymer solutions. In order to cover a wide range of hydrophilic and hydrophobic nature of solutes, salts including ammonium chloride (NH4Cl), ammonium bromide (NH4Br), tetraethyl ammonium bromide (TEAB), tetrapropyl ammonium bromide (TPAB), tetrabutyl ammonium bromide (TBAB), tetrabutyl ammonium chloride (TBAC), and dodecyl trimethyl ammonium bromide (DTAB), and polymers polyethylene glycol (PEG400 and PEG10000) and polypropylene glycol (PPG400 and PPG1000) have been used. In the first part of this work, cloud point temperatures (TC) for binary system of PPG1000 in pure water and for ternary systems of PPG1000 in aqueous solutions of ammonium salts have been determined by visual observation. It is shown that while the inorganic ammonium salts (NH4Cl and NH4Br) reduce the TC values of PPG1000 aqueous solutions (salting-out effect), the organic ammonium salts (TEAB, TPAB, TBAB, TBAC, DTAB) because of hydrocarbon portions in their structure favourably interact with PPG1000 and elevate the TC values (salting-in effect). The values of salting coefficient and energetic parameters of clouding process have been calculated. In the second part of this work, the isopiestic equilibrium has been investigated for several ternary {polymer + ammonium salt + water} systems at 298.2 K. Three different types of constant water activity curves deviation from the linear isopiestic relation (LIR) were observed: negative deviations for systems which undergo salting-out phenomenon and phase separation, positive deviations for systems which undergo salting-in effect, and non-deviation for semi-ideal solutions. The effects of type and molar mass of polymers, and type of cation and anion of ammonium salts on the magnitude and type of salting effects have been scrutinized.

Preparation of Consolidated Body Zeolite from Rice Husk Ash

Rice husks (RHs) are agricultural wastes which include approximately 20 mass% of silica (SiO2). In Thailand, RHs have been applied as fuel for thermal power generation systems and a large amount of ash (Rice husk ash: RHA) was produced. In addition, our research group has reported before that binder-free consolidated zeolite A could be obtained by using SiO2 powder with geopolymer reaction as a humidity conditioning material because zeolite A has been used as desiccant and builder for detergent with low silica content. Moreover, other kind of zeolite with high amount of SiO2 content, such as ZSM-5, was under interest due to its good properties as catalytic activity and a unique pore structure. But, it was not widely utilized because of the difficulty of consolidated body preparation. Therefore, in the present study, the possibility of the usage of RHA as raw materials for consolidated zeolite A and ZSM-5 was investigated for the high-value application of RHA under specific heat treatment condition, molar ratio and preparation technique. After specimens were obtained, XRD analysis and SEM were charactarized for consolidated bodies to confirm cystalline phases and observe microstructure, respectively. Consolidated zeolite A was synthesized with heat treatment above 60°C. The sample heat treated at 60°C for 24 h consisted of homogeneous zeolite A particles with the size smaller than 1 μm. In addition, consolidated ZSM-5 was synthesized with an usual method as TPABr (Tetra propyl ammonium bromide) technique and research method as S.C. (seed crystal) technique. The results showed that although around 10 μm seed crystal was used, around 4~5 μm of ZSM-5 particles were obtained by S.C. technique. This result led to the possibility to use RHA with S.C. technique to synthesize consolidated body and control ZSM-5 particle size.

Desilication of *BEA zeolites using different alkaline media: Impact on catalytic cracking of n-hexane

The desilication of two commercial nano- and one synthesized microcrystal *BEA zeolites via different alkaline solutions have led to several observations. In the nanocrystal *BEA zeolites, the use of NaOH alone reduced the crystallinity and microporosity, which was recovered after the use of pore directing agents as tetrapropylammonium bromide (TPABr). The use of tetrabutylammonium hydroxide (TBAOH) was not as much effective with NaOH as TPABr in terms of crystallinity and microporosity recovery, as it wasn't also as much effective as was NaOH alone in introducing intracrystalline mesopores to these nanocrystals. In the microcrystal series, the use of NaOH with TBAOH was seen to be more effective than NaOH alone or NaOH with TPABr. The increase of relative Brønsted acidity was observed at lower alkaline concentrations with a pronounced decrease at higher alkaline media. The company of the pore directing agents was seen to provoke the formation of new Lewis acid sites. In the cracking of n-hexane, the desilication treatments were not seen to improve the catalytic performance of the requested catalysts, as the slight deactivation of the catalysts was at the basis of coke formation. The activity was seen to drop due to even the diffusional limitations occurring or due to loss of acidity after desilication. More olefin and isomers products were produced despite of coke formed which was considered non-toxic being located inside the mesopores.

Transalkylation Properties of Hierarchical MFI and MOR Zeolites: Direct Synthesis over Modulating the Zeolite Grow Kinetics with Controlled Morphology

Hierarchical zeolites with improved diffusion rate are considered the best strategy to eliminate the limitation of purely microporous network in typical zeolite materials. Herein, hierarchical MFI (Hi-MFI) and hierarchical MOR (Hi-MOR) zeolites with controlled morphology were directly synthesized over modulating grow kinetics. The synthetic parameters were investigated systematically, including gel aging and crystallizing conditions. Using hexadecyl trimethyl ammonium bromide (CTAB) and tetrapropyl ammonium bromide (TPABr) as templates, Hi-MFI nanosheets and sphere-like zeolites were obtained. Besides, unilamellar, multilamellar, nanorod and worm-like Hi-MOR zeolites were synthesized in the presence of CTAB and polyethylene glycol (PEG). The transalkylation of toluene and 1,3,5-trimethylbenzene to xylene performance showed that the hierarchical structure of MFI and MOR zeolites enable zeolite with improved 1,3,5-trimethylbenzene conversion and xylene selectivity Controlled synthesis of hierarchical MFI and MOR zeolites over modulating the grow kinetics.

Conversion of South African Coal Fly Ash into High-Purity ZSM-5 Zeolite without Additional Source of Silica or Alumina and Its Application as a Methanol-to-Olefins Catalyst

Characteristics of ZSM-5 synthesized from H2SO4-treated coal fly ash and fused coal fly ash extracts are compared in this study. In the synthesis process, fused coal fly ash extract (without an additional silica source) was used in the synthesis of ZSM-5. The effect of the structure-directing agent (tetrapropylammonium bromide, 1,6-hexanediamine or 1-propylamine) on the properties and methanol-to-olefins (MTO) effectiveness of the fly ash-based ZSM-5 was also investigated. A pure ZSM-5 synthesized from the fused coal fly ash extract led to a methanol conversion higher than 90% after 5 h on stream. The template 1,6-hexanediamine led to the synthesis of the most stable fly ash-based catalyst keeping a 44% methanol conversion after 24 h on stream.

The capability of tetra alkyl ammonium bromides for aqueous biphasic systems formation with both polymers and electrolytes in aqueous solutions

It was found that the tetra alkyl ammonium halides can solute-out the water soluble polymers and solute out by electrolyte in aqueous solutions and form the aqueous biphasic systems (ABS). To investigate these new kinds of ABS, vapor – liquid equilibria (VLE), vapor – liquid - liquid equilibria (VLLE) and liquid – liquid equilibria (LLE) measurements were carried out for ternary systems containing tetra alkyl ammonium bromides (TAAB): tetra methyl ammonium bromide (TMAB), tetra ethyl ammonium bromide (TEAB), tetra propyl ammonium bromide (TPAB) and tetra butyl ammonium bromide (TBAB); electrolytes: NaCl, NaNO3, Na2CO3 and Na3Cit; and polymers: polypropylene glycol400 (PPG400) and polyethylene glycol400 (PEG400) at different temperatures. It was found that in these systems the soluting-out effect and then the tendency to ABS formation increases by increasing the difference between the hydrophilicity of two components. In the case of TAAB + polymer aqueous systems, the polymer is solute out by the more hydrophilic component TAAB and therefore ABS are formed for aqueous solutions containing PPG (which is more hydrophobic than PEG) and TMAB/TEMB (which are more hydrophilic than TPAB and TBAB). In these types of ABS, the soluting-out effects increase with an increase in temperature. On the other hand, in the case of TAAB + salt aqueous systems, the TAAB is solute out by salt which is the more hydrophilic than TAAB and therefore aqueous solutions containing (TBAB + NaNO3, Na2CO3 and Na3Cit), (TPAB and TEAB + Na2CO3 and Na3Cit) and (TMAB + Na2CO3) are undergoing phase separation and their soluting-out effects increase with decreasing temperature. The isopiestic measurements of the investigated systems show that the constant water activity lines of aqueous PPG + TAAB systems show the positive and the negative deviation from the semi-ideal behavior respectively in biphasic and monophasic area, but those of aqueous salt + TAAB systems show the negative deviation in both biphasic and monophasic area. However, the constant water activity lines of the systems with soluting-in effect, show the positive deviation from the semi-ideal behavior.

An Efficient One-Pot, Four-Component Synthesis of Pyrazolo[3,4-b]pyridines Catalyzed by Tetrapropylammonium Bromide (TPAB) in Water

A novel and one-pot pseudo-four-component reaction between a series of arylglyoxals, malononitrile, 3-methyl-1-phenyl-1H-pyrazol-5-amine, and acetone in the presence of tetrapropylammonium bromide (TPAB) has been developed to synthesize a series of new substituted pyrazolo[3,4-b]pyridines, using water as an environmentally friendly solvent, in high to excellent yields.

Thermodynamics of Inclusion Complexes in Water α-cyclodextrin-Alkyl Halides Adducts at 303.15, 308.15 and 313.15 K

The interaction in water of tetra ethyl ammonium bromide ((C2H5)4N(Br)), tetra propyl ammonium bromide ((CH3CH2CH2)4N(Br)) and tetrabutylammonium bromide ((CH3CH2CH2CH2)4N(Br)) with β-cyclodextrin (β-CD, cyclomaltose) (C42H70O35) for dilute solutions has been studied calorimetrically at the temperature 303.15 and 313.15 K. The values of enthalpy of mixing, Q, of two binary aqueous solutions of β-CD with alkyl halides at all temperatures have been fltted by the method of least squares to the equatlon Q = x1x2 [Ao + A1(x2-x1) + A2(x2-x1)2+ A3(x2-x1)3], where x2 refers to the mole fraction of the alkyl halide. The results obtained have been interpreted in terms of hostguest interaction.

Template‐Free Synthesis of High‐Content Vanadium‐Doped ZSM‐5 with Enhanced Catalytic Performance

AbstractThe high cost of preparation of transition metal doped ZSM‐5 zeolite is limited to the use of organic template such as tetrapropylammonium hydroxide or tetrapropylammonium bromide. In this work, vanadium atom was successfully incorporated into the framework of ZSM‐5 zeolite without using any organic template. Moreover, the method not only decreases the preparation cost of vanadium doped ZSM‐5, but also greatly enhances the utilization ratio of vanadium atom. Vanadium atom mainly exists as tetrahedral coordination in the framework of ZSM‐5 which was demonstrated by the ultraviolet visible and X‐ray photoelectron spectrum. Furthermore, vanadium doped ZSM‐5 performs high and stability catalytic activity in the oxidation of styrene compared to that of the catalyst prepared by the traditional organic template method ascribe to the greatly increase of tetrahedral vanadium species.

Fine-Tuning Synthesis and Characterization of Mono-Sized H-Beta Zeolite-Supported Palladium-Iridium Nanoparticles and Application in the Selective Hydrogenation of Acetylene

In this research, a mono-sized Beta zeolite support synthesized by the solvothermal method was used in the selective acetylene to ethylene hydrogenation reaction with minimum coke build up on the catalyst surface. Tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), n-butylamine, and morpholine were used as structure direct agents (SDA) in the support to obtain various shapes. The characterization results show that although the Si/(Al+SDA) ratio has no effect on the phase purity of support, it has a remarkable effect on porosity, crystal size, shape, and structure of micropores. After comparing characterization results, the developed support, based on TPAOH, was selected and modified by different metals (Ce, Ir, Ag, and Pd) using the incipient wetness co-impregnation method. Since there is an interaction between selectivity and conversion, the optimum metal content in the synthesized catalysts and reaction condition were determined to achieve the desired acetylene conversion and ethylene selectivity. The physicochemical transformation of the developed optimum catalysts was determined using different techniques. Based on the characterization and cata-test results, the catalyst which contains 0.29% Ir and 0.08% Pd presents a better performance and higher stability compared to the other catalysts due to the moderate size and mono layer dispersion of the metals on the support. The experimental results show that acetylene conversion and ethylene selectivity approach 97% and 92% at 55 °C, respectively.

Synthesis and catalytic performance of ZSM-5/MCM-41 composite molecular sieve from palygorskite

ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterification of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template. XRD patterns, N2 adsorption and desorption data, and TEM images show that the composite obtained in the secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase. Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetalization and esterification reaction.

ZSM-5/SBA-15 versus Al-SBA-15 as supports for the hydrocracking/hydroisomerization of alkanes

Al-SBA-15 and ZSM-5/SBA-15 (ZSC) composite were synthesized following hydrothermal procedures in the presence of triblock copolymer Poly(ethylene glycol)- poly(propylene glycol)-poly(ethylene glycol) (Pluronic P123) and a mixture of tetrapropylammonium bromide (TPABr)/Pluronic P123 templates, respectively. Pt(0.5wt.%)/Al-SBA-15 and ZSC bifunctional catalysts were then prepared by a wet impregnation methodology and investigated in the hydrocracking/hydroisomerization of n-decane. Pt/ZSC, containing a trimodal porous texture and high Brønsted acidity, exhibited hydrocracking activity while Pt/Al-SBA-15, showing merely Lewis acidity, was active for hydroisomerization. At 300°C the conversion of n-decane on Pt/ZSC reached 98% and cracking selectivity was about 99%. Both catalysts were exhaustively characterized.