Scientia Iranica
Year:2014 | Volume:21 | Issue:3 (TRANSACTIONS C: CHEMISTRY AND CHEMICAL ENGINEERING)|Papers Count:14

A simple, fast and inexpensive method based on Dispersive Liquid-Liquid Microextraction (DLLME) and Dispersive Solid-Phase Extraction (DSPE) has been developed for preconcentration and pectrophotometric determination of paracetamol (PC) using pH-sensitive hydrogel (HG). In this study, we demonstrate a novel microextraction technique, entitled\semi solid-liquid dispersive microextraction", which can be successfully used for preconcentration of analytes of interest from aqueous samples. The procedure involves the oxidation of paracetamol by Fe (III) and a subsequent reaction with ferricyanide in the presence of HCl to yield a Prussian Blue (PB) complex. In the extraction step, an appropriate amount of poly (styrene-alt-maleic anhydride), as a pH-sensitive hyrogel, was injected into the aqueous solution, so a cloudy solution was formed. Organic and inorganic compounds, having the potential to interact with polymer particles, could be extracted into the organic phase. For our case, the PB complex could be extracted to the cloudy phase. After centrifuging, the hydrogel-rich phase was sedimented at the bottom of the centrifuge tube. The absorbance of the sedimented phase diluted in methanol was measured at the absorption maximum of 733 nm (lmax of PB in hydrogel). The absorbance was linear to paracetamol concentration in the range of 0.01-0.5 mg mL-1, with a correlation coecient of 0.995.

1-aryl-2, 3-dihydro-3-phenyl-1H-naphth [1, 2-e] [1, 3] oxazines are synthesized in good to excellent yields in the presence of LaCl3/ClCH2COOH as an inexpensive and environmentally benign catalytic system under solvent-free conditions.

Silica supported boron triuoride nanoparticles; Dimedone; 2-naphthol; Aromatic aldehydes; Xanthenes. Ane cient and convenient synthesis of benzo [a] xanthene-11-one derivatives has been achieved by a one-pot, three-component reaction of various aromatic aldehydes with 2-naphthol and dimedone in the presence of Silica supported boron triuoride nanoparticles (BF3-SiO2 NPs) as a mild solid acid catalyst in improved yields.

Novel bipodal, tripodalpiperidin-4-ones and their corresponding piperidin-4- ols were subjected to dielectric analysis, which signi es drug delivery. The studies reveal that these compounds can exhibit better drug release in association with polymer.

A room-temperature procedure is developed for the direct synthesis of monoarylidene derivatives of pyran-4-one and piperidin-4-one systems under solventfree conditions. Relatively high yields of products are obtained from the reaction of ketones 1 with dierent aromatic and aliphatic aldehydes under the catalytic system of TMSNMe2 and MgBr2.OEt2. Notably, formation of the undesired bis counterparts, as a major limitation of these reaction types, is minimized using the employed conditions.

Abstract. A one-pot, three-component condensation of aldehydes, 2-naphthol and 2- aminobenzothiazole in the presence of multi-SO3H functionalized ionic liquid (synthesized from hexamethylenetetramine and 1,4-butane sulfonate), as an eective catalyst for the synthesis of 1-(benzothiazolylamino)methyl-2-naphthol derivatives, under thermal and solvent-free conditions, is described. These products involve two biologically active parts; Betti's base and benzothiazole. The present methodology oers several advantages, suchas good yields, short reaction times, and easy work-up. The catalyst could be recycled and reused without substantial reduction in its catalytic activities.

4-hydroxycoumarin 2a and 4-hydroxy-6-methyl-pyran-2-one 2b were applied in a one-pot reaction with Baylis-Hillman adduct acetates 1 to form novel 3-benzylpyrano [3, 2-c] pyran-2, 5-diones 3 in high yields (70-85%). The synthesized framework is available in many biologically active moieties. The reaction was carried out under dierent conditions to achieve optimum conditions. The results indicated that Et3N, as a base under solvent-free conditions, was optimum. The reaction procedure and puri cation method are mild and straightforward.

A simple, ecient and one-pot method has been developed for the synthesis of densely functionalized aryl derivatives of 2-amino-3-cyano-7-hydroxy-4H-chromene by the domino Knoevenagel-Michael-cyclization reactions of aromatic aldehydes, resorcinol and malononitrile in the presence of a catalytic amount of Na2CO3 under grinding conditions.

An easy and highly ecient one-pot, three-component synthesis of rhodanines is reported. The reaction of primary amines, carbon disul de and chloroacetyl chloride proceeded in the absence of solvent and catalyst, to aord 2-thioxothiazolidin-4-ones in good to excellent yields.

In this work, an experimental study of CO2 hydrate formation kinetics was undertaken. The eects of stirring rate and initial pressure on the hydrate formation rate were investigated. The results showed that a stirring rate of 600 rpm was optimum for increasing the CO2 hydrate formation rate, especially at lower temperatures. The eects of additives on the hydrate formation rate were also investigated. Three surfactants: Sodium Dodecyl Sulfate (SDS), Dodecyl Trimethyl Ammonium Bromide (DTAB) and Triton X-100 (TX-100), were tested. DTAB and TX-100 were new surfactants for investigation into CO2 hydrate formation kinetics. SDS and DTAB did not signi cantly aect the hydrate formation rate at concentrations of 300 and 500 ppm, whereas SDS increased, and DTAB insigni cantly decreased the hydrate formation rate at 1000 ppm. Furthermore, TX-100 negligibly decreased the hydrate formation rate at 300 and 500 ppm, but signi cantly decreased the rate at 1000 ppm. In contrast, the application of thermodynamic additives, tetrahydrofuran (THF) and tetra-n-butyl ammonium bromide (TBAB), at low concentrations, increased the hydrate formation rate, and these additives aected the rate of hydrate formation in a manner similar to kinetic promoters.

In this work, the process of free gravity drainage under the inuence of ultrasonic waves was investigated. A glass bead pack porous medium was used to perform free fall gravity drainage experiments. The tests were performed in the presence and absence of ultrasonic waves, and the data of recovery were recorded versus time under both conditions. The wetting phase relative permeability curves were obtained using the data of recovery versus time, based on the Hagoort backward methodology. Subsequently, using the wetting phase relative permeability curve, the relative permeability of non-wetting phases were calculated by performing history matching to the experimental production data. The results revealed that ultrasound considerably increases the recovery factor of the free gravity drainage process. It was also observed that the relative permeability of both wetting and non-wetting phases increases under exposure to ultrasonic waves. The results of this work can be helpful in better understanding/evaluating the behavior of the relative permeability curves of both wetting and non-wetting phases during a free gravity drainage process under exposure to ultrasonic waves.

Removal of zirconium from its dilute aqueous solution using Aspergillus niger as a dried and living biomass was investigated. Through that, the eect of some operational parameters on biosorption, including pH, temperature, contact time, initial concentration of zirconium and dose of biomass, were studied. Based on the results, it was concluded that the uptake of zirconium by both dried and living biomasses is pH dependent, and maximum uptake was observed in pH=3.1 for both biomasses. The maximum uptake capacity of the living biomass was obtained at 30 C. However, the biosorption of zirconium by dried biomass was not aected by temperature. The maximum uptake capacity for living and dried biomasses (78.8 mg/g and 142 mg/g, respectively) was obtained at equilibrium time of 120 min and 30 min, respectively. Equilibrium isotherms showed that adsorption of zirconium by living biomass follows the Freundlich model, and the uptake of dried biomass follows the Langmuir model. Kinetic studies showed that both kinds of biomass follow the second order kinetic model.

In fractured reservoirs, a large variation of permeability due to the presence of fractures leads to changes in the production mechanism compared to conventional reservoirs. Hence, an appropriate model with the ability to describe the reservoir properly can provide a more con dent prediction of its future performance. One of the features of a representative model is the number and height of the matrix blocks. The determination of these two parameters is one of the decisive steps in the calculation of an accurate amount of oil production from these reservoirs. In fact, matrix height shows its eect as a gravity force, which is one of the driving mechanisms. If the matrix height is less than the threshold height, it will have a signi cant inuence on production. The aim of this study is, therefore, to obtain mathematical relations that are able to estimate the matrix height from material balance analysis. In this study: (a) The Havlena and Odeh straight line form of the material balance equation has been extended to analyze the behavior of naturally fractured reservoirs, and (b) Equations that can be used to estimate the matrix height are obtained for the Warren-Root and Kazemi models.

Renewable resources such as natural llers in reinforced materials, with their new range of applications, represent an important basis for ful lling the ecological objective of creating environmental friendly materials. A study on composites, using breadfruit seed hull ash particles (BFSHAp) as a reinforcing material and recycled low-density polyethylene (RLDPE) as a novel matrix, has been undertaken. The composites were produced by varying the breadfruit seed hull ash particles from 5-25 wt% and the properties studied using mechanical tests and microstructural analysis. The results show that there was a uniform distribution of the breadfruit seed hull ash particles in the microstructure of RLDPE composites, which is a major factor responsible for improvement in mechanical properties.