Presence Of Tetrapropylammonium Bromide Research Articles

Gas-Phase Epoxidation of Propylene with Hydrogen Peroxide Vapor: Effect of Modification with NaOH on TS-1 Titanosilicate Catalyst in the Presence of Tetra-propylammonium Bromide

This study was related to a solvent-free gas-phase epoxidation of propylene with H2O2 vapor to synthesize propylene oxide (G-HPPO). Focus was given to the hydrothermal modification of TS-1 with NaO...

Facile, one-pot, four-component synthesis of a new series of imidazo[1,2-a]pyridines in presence of TPAB in EtOH under reflux conditions

A convenient, regioselective, novel, and elegant one-pot, four-component reaction was designed for synthesis of a series of new of imidazo[1,2-a]pyridines using aryl glyoxal monohydrates, ethyl acetoacetate, hydrazine hydrate, and 2-aminopyridine in presence of tetrapropylammonium bromide under reflux in EtOH as solvent. The main advantages of this protocol include the availability and low cost of the starting materials, short reaction time, convenient operation, easy workup process, highly facile operation, nonhazardous byproducts, and high yield (82–94%).

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.

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.

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.

Synthesis of ZSM-5 zeolite from metakaolinite: Effects of the SiO2/Al2O3 molar ratio, the initial precursor and the presence of organic template agent

Highly crystalline ZSM-5 zeolites are successfully prepared from kaolinite as low cost precursor. The effects of SiO2/Al2O3 molar ratio, the presence of tetrapropylammonium bromide (TPABr) and the initial precursor on the textural properties of the final products have been investigated. Crystallized samples have been characterized by scanning electron microscopy and nitrogen adsorption in addition to X-ray diffraction. The results show that getting pure ZSM-5 zeolite with a high crystallinity degree is directly dependent on the starting precursor as well as on the presence of the organic template highlighting the role of SiO2/Al2O3 molar ratio. The directed-template ZSM-5 sample prepared frommetakaolinite with the smallest particles (crystal size of 700 nm) and a maximum crystallinity of 98% is obtained at a SiO2/Al2O3 molar ratio of 31.69. Increasing the SiO2/Al2O3 molar ratio to 41.13 isrequired to prepare an organic-template free ZSM-5 from metakaolinite with a relative crystallinity of 81%. In order to synthesize ZSM-5 zeolite from the acid-activated metakaolinite as the only silica and alumina sources, a SiO2/Al2O3 molar ratio of 76.19 is used, the maximal crystallinity degree is 79%, with the largest ZSM crystals of about 3000 nm.

Synthesis of ZSM-5 zeolite from diatomite for fluid catalytic cracking (FCC) application

In this study, ZSM-5 zeolite was successfully synthesized hydrothermally from cheap and easily accessible natural mineral diatomite in the presence of tetrapropyl ammonium bromide. The pore structure, acidic sites and surface features of as-synthesized ZSM-5 zeolite were well characterized by X-ray diffraction, scanning electron microscopy, pyridine-adsorbed Fourier transform infrared spectroscopy, and N2 adsorption. The analysis results revealed that the as-synthesized ZSM-5 zeolite exhibited excellent hydrothermal stability, high specific surface area (223 m2 g−1) and more acidic cites than diatomite. After mixing ZSM-5 zeolite with a FCC base catalyst, the catalytic performance was evaluated in a micro-fixed bed reactor using vacuum gas oil (VGO) as feedstock. The high surface area and more acidic sites of as-synthesized ZSM-5 zeolite played an important role in the production of light olefins (propylene and butylene) during catalytic cracking of VGO.

Effect of Tetra Propyl Ammonium Bromide During Cobalt Electrodeposition from Acidic Sulfate Solutions

In the current study, the effect of an organic additive tetra propyl ammonium bromide (TPAB) on the structural, morphological characteristics of the cobalt metal produced from aqueous sulfate solutions has been investigated. The concentration of TPAB was varied over a range of 1 to 50 mg/L to evaluate its effect on current efficiency, energy consumption, and quality of electrodeposited cobalt. Smooth and bright electrodeposits of cobalt were obtained at low concentration of TPAB (10 mg/L) maintaining a current efficiency of 99.4 pct, with a low energy consumption of 2.42 kWh/kg. X-ray diffraction studies revealed that (100) plane is the most preferred plane of crystal growth during cobalt electrodeposition. However, at higher concentrations, the (101) plane became the most preferred one. Scanning electron micrographs indicated that smooth and uniform deposit of cobalt was obtained at 10 mg/L beyond which the deposit quality deteriorates. The presence of TPAB in the electrolytic bath polarizes the cathode and decreases the cathodic current considerably. AAS results indicated that the cobalt deposits were of high purity.

Catalytic cracking of heavy naphtha-range hydrocarbons over different zeolites structures

The effects of textural, structural, morpholgical, and acidic properties of HZSM-5, H-mordenite and (MFI/MOR) composite zeolite on the catalytic cracking of heavy naphtha-range hydrocarbons (dodecane, iso-octane, and ethylbenzene) as well as heavy naphtha were studied. XRD and SEM results revealed the presence of (MFI/MOR) overgrowth composite zeolite upon recrystallization of H-mordenite in the presence of tetrapropylammonium bromide. Significant cracking of dodecane occurred over different zeolites, however, very low cracking of iso-octane was observed over HZSM-5. The conversion of ethylbenzene, iso-octane and dodecane at 400°C was 69.6, 74.5 and 86.4wt.%, respectively, over H-mordenite, compared with 69.8, 11.2 and 83.8wt.%, respectively, over HZSM-5. (MFI/MOR) overgrowth zeolite exhibited an intermediate level of cracking. Catalytic cracking of hydrocarbon mixtures followed similar trends as those for pure model compounds. Catalytic cracking of heavy naphtha was higher over HZSM-5, compared to H-mordenite (94.4wt.% vs. 76.5wt.%). The kinetic modeling studies indicated that the rate of hydrocarbon cracking varies with the nature of model compounds and zeolite structure. The apparent activation energies (Ea) for the three model compounds increased in the following order; HZSM-5>(MFI/MOR)>H-mordenite, whereas the difference in Ea over various zeolites was much larger for iso-octane and ethylbenzene.

Synthesis and characterization of aluminium-free ZSM-5 type chromosilicates in different alkaline systems and investigation of their pore structures

Aluminium-free ZSM-5 type chromosilicates as M[Cr]ZSM-5 (M=Na, K and Cs), were synthesized successfully from silicic acid, sodium (or potassium or cesium) carbonate and chromium (III) nitrate using hydrothermal procedure in the presence of tetrapropylammonium bromide (TPABr) as a template. These samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TG), Fourier transform infrared spectroscopy (FT-IR) and N2 physical adsorption analysis. The experimental results show that M[Cr]ZSM-5 mesoporous molecular sieves were successfully synthesized. In the synthesis of M[Cr]ZSM-5, a pure MFI phase was obtained with a relatively low concentration of chromium in the synthesis gel. For higher chromium concentration in the synthesis gel, the final product was found to be amorphous. According to N2 physical adsorption analysis, the linear portion of the last section of t-plot, is extrapolated to the adsorption axis of the comparison plot, and this intercept is used to obtain the volume of the micropores. By using different alkalin cations in the synthesis process such as Na or K or Cs, the crystallinity of the zeolite, decreases with the order of Na>K>Cs; studying the porosity characterization of the system with different alkaline cations, also shows the same order for the BET surface area of the samples, but reverse order for the size of pores in the structures of chromosilicates. The effect of various factors, such as crystallization temperature, crystallization time and pH of reaction system on the crystallization process was investigated in detail.

ZSM-5/SBA-15 microporous/mesoporous composites prepared by a microwave-assisted zeolitisation of Al-SBA-15 mesoporous solids

ZSM-5/SBA-15 composites with high textural properties were synthesised by a microwave-assisted zeolitisation of Al-SBA-15 in the presence of tetrapropylammonium bromide. The effect of the hydrothermal treatment temperature and of ammonium fluoride, often used as a catalyst, was studied. Resulting materials were characterised by XRD, SEM, N2 sorption, HR-TEM, hyperpolarised Xe NMR, pyridine sorption as well as by their stability toward boiling water. It was shown that the hydrothermal synthesis has to be carried out at 140°C in order to better preserve the structure of the mesoporous precursor. Composite materials could be obtained only from a fluoride-free synthesis at short crystallisation times, t<5h. Appearance of 2–5nm nanoparticles in some of the corresponding samples, has been related to the increase in the total acidity. Inclusion of zeolitic material in the remaining Al-SBA-15 structure was demonstrated by hyperpolarised xenon NMR studies.

Hydrothermal Synthesis of Magadiite/Si‐ZSM‐11 Composites

The simplified one‐step hydrothermal synthesis, in which SiO2 is directly reacted with aqueous NaOH in the presence or absence of tetrapropylammonium bromide (TPABr) and tetrabutylammonium bromide (TBABr) as the template compound, was investigated. The reaction in the absence of the template compounds leads to the production of pure magadiite, whereas pure Si‐ZSM‐5 is produced by the reaction in the presence of TPABr. On the other hand, crystalline magadiite/Si‐ZSM‐11 composites are synthesized by the reaction in the presence of TBABr. Furthermore, for the composites, the particle sizes of the magadiite and Si‐ZSM‐11 may be influenced by the TBABr concentrations. It was also found that the compositions of magadiite and Si‐ZSM‐11 in the composites can be controlled by regulating the NaOH concentrations.

Synthesis, characterization and acidic properties of nanopowder ZSM-5 type ferrisilicates in the Na +/K + alkali system

In this study Aluminium-free ZSM-5 type nanopowder ferrisilicates (as K–FZ or Na–FZ) were synthesized successfully from silicic acid, potassium (or sodium) carbonate and iron (III) nitrate using hydrothermal procedure (in relatively low crystallization time) in the presence of tetrapropylammonium bromide (TPABr) as a template. Prepared samples have been characterized by XRD, TEM, EDAX, NH 3-TPD, BET surface area, FTIR, TGA/DTA, SEM and ICP analysis. FTIR spectra confirm the production of ZSM-5 type ferrisilicates by the zeolite pentacycle peak at 547 cm − 1 and the symmetric stretching peak of Si–O–Fe at 656 cm − 1. XRD diffractograms confirmed ZSM-5 crystal phase. The results clearly show that K + cation (like Na +) plays a role of structure directing as well as a role of charge balancing agent. This could be assigned from NH 3-TPD analysis that ferrisilicate pretreatment procedure and iron-exchanging can significantly affect the strength of acidic sites. NH 3-TPD indicates that using potassium instead of sodium, leads to an increasing of the global acidity. Furthermore Na–FZ exchanging with iron ions (as Fe–NaFZ) leads to the same results. Thermal analysis revealed 14.7% weight loss due to the decomposition of TPABr template. Scanning electron microscope revealed that there is clustering of spherical particles in dry state. The TEM images confirm the particle size of the ferrisilicates in the range of 15–30 nm and show that iron-exchanged ferrisilicate has well-dispersed nano-sized iron oxide particles with various sizes in the range of 5–15 nm.

SYNTHESIS AND PHYSICOCHEMICAL CHARACTERIZATION OF ZSM-5 METALLOSILICATE ZEOLITES PREPARED BY ISOMORPHOUS SUBSTITUTION PROCESS

Metal ions-containing ZSM-5 materials were prepared by isomrphous substitution of purely ZSM-5 using different metal ions, namely Co(II), Ni(II) and Cu(II). The metal modified ZSM-5 samples were synthesized hydrothermally in the presence of tetrapropyl ammonium bromide (TPABr) as the template and n-propyl amine (n-PrNH2) as the mobilizing agent. The structure, morphology, particle-size distribution, surface texture and acidity of these materials have been investigated and compared with ZSM-5 prepared by direct hydrothermal synthesis. The apparent effect of the substitution of Al by Co(II) ions on the crystal size results in a structural arrangement of the gel during aging-favoring nucleation.Thesurfacearea, degree of crystallinity and particle size of Co/ZSM-5 increase at the expense of pore radius, though Ni(II) and Cu(II) ions substituted ZSM-5 cause lesser effects. The M/ZSM-5 catalyst in the presence H2O2/UV is an active system for the oxidative color removal of Direct blue-1 in aqueous heterogeneous suspensions with a very low M(II)/substrate ratio. The high phase heterogeneity of Co/ZSM-5 catalyst account for the increased values of the activity than the corresponding Ni/ and Cu/ZSM-5 ones.

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.

Surface Characteristics and Catalytic Oxidation of CO on Silicalites and Silicalites Containing Cobalt, Copper and Silver Oxides

Two silicalite samples, S1 and S2, were prepared hydrothermally in the presence of tetrapropylammonium bromide (TPA-Br) and tetrabutylammonium bromide (TBA-Br), respectively. Cobalt oxide, copper oxide or silver oxide (all at 10 wt% concentration) were incorporated into the S1 and S2 silicalites by impregnation methods. The structural and textural properties of the prepared samples were studied using a variety of techniques together with their ability to catalyze the oxidation of CO. The results obtained indicated that S1 and S2 existed as pure phases with structures analogous to those of ZSM-5 and ZSM-11 zeolites, respectively.Electron microscopic analysis showed that the crystalline morphology of S1 and S2 consisted of intergrown discs and shelf-like shapes with diameters in the range 10-15 μm and 29-33 μm, respectively. Differences noted during kinetic studies of CO oxidation over the prepared samples were discussed.