Scientia Iranica
Year:2012 | Volume:19 | Issue:6 (TRANSACTIONS C: CHEMISTRY AND CHEMICAL ENGINEERING)|Papers Count:16

ZnFe2O4 nanoparticles have been successfully prepared through a controlled microwave- assisted co-precipitation. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM) were used for the structural, morphological and magnetic investigation of the product. SEM micrographs of ZnFe2O4 nanopowder also reveal that nanoparticles have spherical shape. Average particle size was obtained as 12 nm from XRD. Catalytic activity of ZnFe2O4 nanopowder for O-acylation of alcohol and phenol has been investigated. A trace amount of ZnFe2O4 has been effectively used as a nanocatalyst for the acylation of alcohol and phenol in acetic anhydride.

Many acid additives are used during acidizing treatment in order to prevent excessive corrosion, prevent sludge and emulsions, prevent iron precipitation, improve cleanup, improve coverage of the zone, and prevent precipitation of reaction products. Foremost among acid additives are corrosion inhibitors; therefore compatibility of other additives with corrosion inhibitor is very critical to the success of acidizing treatment. Any additive that alters the tendency of the corrosion inhibitor to adsorb on casing and tubing will also change its effectiveness. In present work, the inhibitive action of henna extract on corrosion of N 80 API steel in regular mud acid (HCL/HF 12/3 wt%) at 28 oC was investigated through electrochemical technique. After determining the optimum concentration of henna extract, effect of acid additives on inhibitive action of henna extract on corrosion behavior of N80 steel in regular mud acid was investigated through polarization measurement and electrochemical impedance spectrometry methods. Inhibition efficiency of henna extract as a corrosion inhibitor forN80 API steel in regular mud acid at 28 oC is 85.98% (average of three methods). The results show that except iron control additive, all additives decrease the performance of henna extract as corrosion inhibitor.

A thermodynamic model for an open inverse Brayton cycle (refrigeration or heat pump cycle) with pressure drop irreversibilities is established. There are seven flow resistances (or pressure drops) encountered by the working fluid stream for the inverse Brayton cycle. Two of these, the friction through the blades and vanes of the compressor and the expander, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet and outlet, heat exchanger inlets and outlets and expander inlet and outlet. The analytical formulae about the cooling load of refrigeration cycle, the heating load of heat pump cycle and other coefficients are derived, which indicate that the thermodynamic performance for open inverse Brayton cycle can be optimized by adjusting the mass flow rate (or the distribution of pressure losses along the flow path). It is shown that there are optimal air mass flow rates (or the distribution of pressure losses along the flow path) which maximize the cooling load of refrigeration cycle, and the optimal air mass flow rates are smaller than the one at the maximum power output of the direct Brayton cycle.

This paper concerns the simulation and control of multi-vessel batch distillation configurations for separating tertiary zeotropic mixtures. Three configurations, namely, conventional middle vessel, modified middle vessel and rectifier column were selected. Unlike the previous works, a detailed model without assumptions of constant level, pressure and boilup rate was used. This model was simulated in Aspen Hysys 2009 software. In addition, a control structure which has one pressure and one/two level controllers was selected for each configuration. The results indicate that the selected control structure has an acceptable performance and the modified middle vessel configuration needs the least batch time and energy consumption. Finally, the performances of level control and temperature control strategies were compared. The results show that the level control strategy has better dynamic performance and needs lower batch time, but with uncertain feed composition, the temperature control structure is preferred.

In this paper, a new plant based natural cationic surfactant, named Seidlitzia rosmarinus, is introduced, and the viability of using this natural surfactant as an alternate to synthetic surfactants for chemical enhanced oil recovery is investigated. For this purpose, the interfacial tension values between natural surfactant solution and oil are measured by using the pendant drop method. The results show that Seidlitzia rosmarinus decreased the interfacial tension values from 32 to 9 mN/m. Results confirm the fair surface activity of Seidlitzia rosmarinus in comparison with other natural and synthetic surfactants. Accordingly, this natural surfactant can be used as a surfactant for chemical enhanced oil recovery.

A simple and highly efficient method for the protection of amines from their corresponding N-boc derivatives is reported. It is interesting that only 0.1 mol % of novel ionic liquid 1, 3-disulfonic acid imidazolium hydrogen sulfate {[Dsim] HSO4} can efficiently catalyze the reaction. Clean reaction, very short reaction times, high yields, easy preparation and high TOF (turn over frequency) values of the catalyst in comparison with reported catalysts are some advantages of this work.

Curcumin, a polyphenol yellow orange pigment present in Indian spice “turmeric”, is a member of the ginger family (Zingiberaceae). The extract of turmeric was obtained by using soxhlet apparatus at 45-55 oC, using methanol as solvent and then curcumin was isolated from methanolic extract by column chromatography. In the present study, a series of four new derivatives of curcumin (3a-d) were synthesized by reacting curcumin (1) with different alkyl halides (2a-d) using DMF and lithium hydride. The structures of natural curcumin and its synthetic derivatives were confirmed with the help of their 1H-NMR spectra and all these were screened against acetylcholinesterase, butyrylcholinesterase, lipoxygenase and trypsin enzymes. Curcumin and its derivatives exhibited moderate inhibitory potential against all aforesaid enzymes.

A class of one-way isothermal mass transfer processes is investigated in this paper. Based on the definition of mass entransy, the entransy dissipation function, which reflects the irreversibility of the mass transfer ability loss, is derived. The optimality condition for the minimum entransy dissipation of the mass transfer process with a generalized mass transfer law is obtained by applying an optimal control theory. Special cases for the linear [g µ D(m)] and the diffusive [g µ D(c)] mass transfer laws are obtained based on the general optimization results. The obtained results are also compared with strategies of minimum entropy generation, constant concentration ratio and constant concentration difference operations. The results obtained herein can provide some theoretical guidelines for optimal design and operation of practical mass transfer processes.

Sol-gel methods and organic and inorganic precursors of titania were used for preparation of the monolithic catalysts, Rh=TiO2. Techniques, such as X-ray diffraction, porosimetry, temperatured programmed reduction, scanning electron microscopy, and X-ray photoelectron spectroscopy, were utilized to characterize the monolithic catalysts. Results of the short contact-time partial oxidation of methane revealed the promoting role of tungsten. This study demonstrates that the catalyst prepared from titanium isopropoxide is more effective in the production of synthesis gas.

This article describes simple and efficient method for the diazotization and iodination of different aromatic amines over cellulose sulfuric acid, sodium nitrite and potassium iodide under solvent-free conditions at room temperature. Various aryl amines possessing electron-withdrawing groups or electron-donating groups are converted into the corresponding aryl iodides in 54%-97% yields. Advantages of this methodology are the use of mild reaction conditions, avoiding the use of harmful acids and toxic solvents and short reaction time.

This paper presents a methodology for calculation of a slug, two-phase flow hold-up in a horizontal pipe. The advantage of this method is that the slug unit hold up can be calculated directly from the solutions of flow field equations with no need to use correlations. An experimental apparatus to measure air-water hold up was setup. The flow pattern and liquid holdup in horizontal and inclined pipes, from angles 5o to 40o, for air-water two-phase flow, are experimentally observed. The test section, with an inside diameter of 30 mm and 3 m in length, was made of plexy-glass to permit visual observations of the flow patterns. The proposed model was tested extensively against experimentally collected data. Furthermore, other data sources for slug flow in horizontal pipes, for air-water and air-oil systems, were also used for comparison. The presented methodology was compared against four recently developed models of a two phase, slug flow holdup in horizontal pipes. Not only does the presented model demonstrate good agreement, with less than 6.8% error, compared to the experimental data, but also has less error compared to other models. These results substantiate the general validity of the model.

The SAPO-34 catalyst was synthesized by the combination of TEAOH and morpholine templates, and colloidal silica and silicic acid, as the silica source under hydrothermal conditions. The effect of the template molar ratio and silica source on the physicochemical properties of each catalyst was studied by XRD, SEM, BET and TPD techniques. XRD patterns revealed the significant effect of gel composition on the crystallinity and particle size of the samples. SEM photos showed that all the catalysts have cubic morphology, but their particle size was different. According to the XRD and SEM of the catalyst prepared by silicic acid, this catalyst showed low crystallinity and large crystal size. TPD analysis indicated that the acidity reduced by increasing the morpholine content in the reaction mixture. The catalytic performance of the synthesized catalysts was tested in MTO reaction. The catalyst produced by the TEAOH/morpholine ratio of 0.5:1.5 exhibited the highest light olefins yield, as well as the longest catalyst lifetime. The maximum yield of ethylene and propylene was determined to be 94 wt%, with 100% methanol conversion.

An efficient, highly chemoselective and simple synthesis of secondary amines via reductive amination of aldehydes, aromatic amines and inexpensive and easily accessible Diethyl 2, 6-dimethyl-1, 4-dihydro-3, 5-pyridinedicarboxylate (DHP) in the presence of catalytic amounts of p-toluenesulfonic acid (PTSA) in water in good to excellent yields is reported.

Dye sensitizers loaded on TiO2 decrease the electron excitation energy, thereby improving the photocatalytic performance by causing an increase in sensitivity under visible light irradiation. Three dye sensitizer precursors, Mordant Orange 1, N3 (red dye) and Cobalt (II) Phthalocyanine Tetrasulfonate (CoPcTs), were utilized to load the photocatalyst. The rate of the electron trapping process on platinum is clearly compatible with the migration rate of boundary electrons. Consequently, the migration of boundary electrons from the conduction band towards electron acceptors is increased by loading platinum onto the titanium dioxide.In this research, TiO2 was synthesized from a titanium isopropoxide precursor using the solgel method, and the product was compared with commercial TiO2-P25 (consisting of 80% anatase and 20% rutile phases). Evaluation of the effect of calcination temperature on the formation of the nanosize photocatalyst and the phase formed was performed through the XRD technique. The specific surface area was determined by BET measurement. Ultimately, the absorption of all samples and their efficiencies were compared using the Diffuse Reflectance Spectroscopy (DRS) technique under visible light irradiation.

Ploycyclic Aromatic Nitrogen Heterocycles (PANHs) are a widespread class of water pollutants that are known to cause serious human health problems; and the demand for effective adsorbents for the removal of toxic compounds is increasing. In this work Ordered Mesoporous Carbon (OMC) was prepared by using SBA-3 silica mesoporous molecular sieves as hard template. Then, Cu (II) modified mesoporous carbon molecular sieves, Cu2+-OMC, was prepared through wet impregnation of OMC by CuSO4 . 5H2O. Orthophenanthroline (OP) and 2; 2’-bipyridine (BP) were used as probe molecules to investigate their adsorption behavior on Cu2+-OMC. The synthesized mesoporous sample is used as a sorbent for fast and highly efficient removal of OP and BP from contaminated waters. The isotherms of OP and BP on Cu2+-OMC are well simulated by a Langmuir adsorption model. Theoretical studies show that the adsorption kinetics of OP and BP on Cu2+-OMC can be well depicted by using a pseudo-second-order kinetic model.

Artificially made seismic waves have been used for both tertiary recovery and well stimulation purposes. The idea behind using this method for enhancing recovery came from a number of real examples, in which a kick in oil production has been seen following an earthquake. Most published information has addressed the United States and earlier Soviet Union regions. This paper documents the results of observations regarding the effect of earthquake waves on well production from Khami carbonate gas condensate reservoir in the Marun field, in the northern Persian Gulf. The response of three wells in this reservoir (referred to as wells A, B, and C) to a magnitude M=5.7 earthquake at an approximate distance of 217 km away is discussed. After this earthquake, there was a sharp significant increase in production from well A. The flowing wellhead pressure of this well suddenly increased from 4263 to 5042 psig and went back to its normal condition after five months. The two other wells behaved differently and showed no change in production. Analyses showed the removal of near wellbore formation damage caused by a condensate dropout in well A using natural seismic waves.