فهرست مطالب

Chemical Engineering - Volume:13 Issue: 3, Summer 2016

Iranian journal of chemical engineering
Volume:13 Issue: 3, Summer 2016

  • تاریخ انتشار: 1395/03/20
  • تعداد عناوین: 7
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  • M. Bayat*, M. R. Rahimpour Pages 3-18
    Nowadays, hydrogen and methanol are attractive prospects because of lower emissions compared to the other energy sources and their special application in fuel cell technology, which are now widely regarded as key energy solutions for the 21st century. These two chemicals can also be utilized in transportation, distributed heat and power generation and energy storage systems. In this study, a novel double fluidized-bed two-membrane reactor (DFTMR) is proposed to produce ultrapure hydrogen and enhance methanol synthesis as environmentally friendly fuels, simultaneously. The fluidization concept is used in both sides to overcome drawbacks such as internal mass transfer limitations, pressure drop, radial gradients of concentration and temperature in thermally coupled membrane reactors. The DFTMR system is modeled based on the two-phase theory of fluidization and then its performance is compared with those of thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) under the same operating conditions. The simulation results show 24.69% enhancement in hydrogen production in comparison with TCMR. Furthermore, 14.39% and 15.78% improvement in the methanol yield can be achieved compared with TCMR and CR, respectively.
    Keywords: Ultrapure Hydrogen Generation, Methanol Enhancement, Fluidized, bed Reactor, Recuperative Coupling, Two, membrane Concept
  • L. Amirkhani, J. Moghaddas*, H. Jafarizadeh, Malmiri Pages 19-31
    Magnetic silica aerogel in hydrophobic and hydrophilic forms were used as support to immobilize Candida rugosa lipase by adsorption method. Response surface methodology (RSM) was employed to study the effects of the three most important immobilization parameters, namely enzyme/support ratio (0.3-0.5, w/w), immobilization time (60-120 min) and alcohol percentage (20-40, v/v%) on the specific activity of immobilized lipase on the hydrophobic supports. For hydrophilic supports, alcohol percentage was removed as there was no need for pre-wetting step in enzyme immobilization process. Second order regression models with high coefficient determination (R2) values of higher than 0.98 were fitted to predict the response as function of immobilization parameters. The results indicated that for hydrophobic supports, optimum values for enzyme/support ratio, immobilization time and alcohol percentage were obtained at 0.45 (w/w), 94.00 min and 37.22%, respectively, in which specific activity were predicted at 15.34 U/mg-protein. For hydrophilic supports, the optimum enzyme/support ratio and immobilization time were predicted at 0.47 (w/w) and 83.47 min, respectively. Specific activity in these conditions was obtained 11.21 U/mg-protein. As the difference between the experimental and predicted values was shown as non-significant, the response surface models employed could be considered as adequate.
    Keywords: Magnetic Silica Aerogel, Hydrophobic, Central Composite Design, Mesoporous, Response Surface Methodology, Candida Rugosa Lipase
  • A. A. Sarbanha, F. Sobhanian, S. Movahedirad* Pages 32-42
    A Laser Induced Fluorescence technique (LIF) has been used to study the mixing behavior of two emerging streams in a T-Type mixing chamber. A mixing index on the basis of digital image light intensities is calculated. It has been shown that averaging over more than 800 images leads to a stable mixing index calculation. Moreover, the effect of equal and un-equal flow rates on the mixing behavior of the streams has been studied. The results show that the histograms of the light intensity changes from double peak (unmixed) to a single peak (mixed) at high elevations of the chamber. Mixing index has a linear descending behavior moving toward the cell front wall and it was shown that the mixing index can be reduced up to 50% moving from cell center to near wall region. Moreover, there is a transition zone in both equal and un-equal fluid flow rates in mixing index. It was shown that the third component velocity plays an important role in mixing behavior in T-Type mixing chamber.
    Keywords: Laser Induced Fluorescence (LIF), T, Type Chamber, Liquid Mixing, Mixing Index
  • A. Karimi, E. Fatehifar*, R. Alizadeh, M. Jamili, A. Jafarizad Pages 43-53
    In this paper, xCuO/CeO2–γAl2O3 nano-catalysts were successfully synthesized by precipitation method and modified via ultrasonic waves. For characterization of xCuO/CeO2–γAl2O3 samples N2 adsorption results showed that the BET surface area of the CuO/CeO2–γAl2O3, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-rays (EDX dot-mapping) were used. The BET, XRD and SEM results indicate that CuO/CeO2-γAl2O3 particles are nano-structured catalysts. These catalysts (xCuO/CeO2–γAl2O3) have high specific surface and finer particle that confirm SEM pictures. xCuO/CeO2–γAl2O3 catalyst compared to other previous synthesis catalysts for selective CO oxidation. The activity and selectivity of these catalysts obtained in the presence of rich hydrogen stream, with space velocity of 30,000 h−1 in the absence of CO2 and H2O. Results show that CuO/CeO2–γAl2O3 demonstrate high CO conversion in temperature less than 120°C, and selectivity of more than 63% at 100°C. Also, results show that decreasing of CeO2 amount decreases selectivity of CO oxidation.
    Keywords: Selective Oxidation, CuO, CeO2, Alumina, Ultrasound Energy, nanocrystal
  • P. Abimannan, V. Rajendran* Pages 54-62
    Article history:Received: 2015-11-28
    Accepted: 2016-04-19 In this paper, we report the reaction of isoamyl alcohol with 1-chloro-4-nitrobenzene that was carried out in a batch reactor in aqueous-organic biphasic condition using the techniques like phase transfer catalysis and ultrasound irradiation. Tetrabutylammonium bromide (TBAB) was employed as the phase transfer catalyst. The reaction is greatly enhanced by adding a small quantity of phase-transfer catalyst under ultrasound (28 kHz, 300W). Kinetics of the etherification was investigated in detail. The rate constants were determined by varying the concentration of the catalyst, stirring speed, the concentration of alcohols, temperature, different solvents, and concentration of sodium hydroxide, different inorganic salts and different phase transfer catalysts. From the detailed kinetic study, the optimum reaction condition to produce higher yield of 1-(isopentyloxy)-4-nitrobenzene was obtained. The experimental data were well described by the pseudo-first-order equation. The individual experiment was carried without ultrasound; the obtained kapp value is 0.0094 1/min. The combination of ultrasound and stirring resulted the kapp value of 0.0178 1/min. From the observed results, the kapp value for ultrasonically promoted reaction is almost two-fold higher than the normal reaction.
    Keywords: Phase Transfer Catalysis, Immiscible Phases, Ultrasound, 1, (Isopentyloxy), 4, Nitrobenzene, Reaction Kinetics
  • M. Omidifar, S. Shafiei*, H. Soltani Pages 63-77

    In modern refineries, hydrogen is widely used for the production of clean fuels. In this paper, a new method is presented in order to use hydrogen more effectively in refineries. This new method is based on combination of linear programming with imperialist competitive algorithm (ICA) in order to optimize the hydrogen distribution network. In this new approach, optimization is performed in two levels. In one level the hydrogen network layout is proposed by ICA and in the other level the total annual cost and utility are optimized by the linear programming. Thus, the minimum cost and the optimal configuration of the hydrogen distribution network are obtained. Finally, to illustrate the application of this method two cases are studied.

    Keywords: Linear Programming, Optimization, Hydrogen Distribution Network, Clean Fuel, Imperialist Competitive Algorithm
  • M. Shahzamani, N. Golshan Ebrahimi *, M. Sadeghi, F. Mostafavi Pages 78-88
    In this study, the relation between the permeation properties and structural characteristics of thermoplastic polyurethane based on polycaprolactone diol, TPU(PCL), and polycaprolactone (PCL) blends is investigated. For the purposes of this study, PU, PCL, and TPU/PCL blends containing 20 wt% and 40 wt% PCL were prepared via a solution blending method. The miscibility and good distribution of PCL in the soft segment of PU were represented by the reduced intensity of the band attributed to the NH band at 3400 cm-1 in the Fourier transform infrared (FTIR) spectra. X-ray diffraction (XRD) results indicated that the amorphous structure of TPU changed to a crystalline one when PCL was added. These results were further confirmed by FTIR and differential scanning calorimetry (DSC) analyses. The permeability of CO2, O2, N2, and CH4 gases at different feed pressures ranging from 12 to 16 bar was determined. A reduction in gas permeability due to the increase in PCL content was observed in the blends. However, gas selectivity did not change with addition of PCL.
    Keywords: Polyurethane, Polycaprolactone, Polymer Blend, Microstructure, Gas Transport Property