فهرست مطالب

Chemical Engineering - Volume:18 Issue: 4, Autumn 2021

Iranian journal of chemical engineering
Volume:18 Issue: 4, Autumn 2021

  • تاریخ انتشار: 1401/05/12
  • تعداد عناوین: 6
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  • Nemat Alimohammadi, Sohrab Fatthi * Pages 3-20

    In this research, the selective hydrogenation of benzene in a mixture of benzene and normal heptane (5 vol.% of benzene) over various heterogeneous catalysts was evaluated. For this purpose, a series of catalysts with various supports such as Pd/ZSM-5, Pd/13X and Pd/〖"Al" 〗_"2" "O" _"3" were developed. To prepare Pd supported catalysts, the modification of supports was conducted out by a specified amount of palladium nitrate in the aqueous solution. Experimental catalyst evaluation tests were performed in the catalyst assessment set-up (Cata-test). The characterizations of physicochemical properties of the prepared catalysts were performed by XRD, NH₃-TPD and BET. It was found that the conversion of benzene was promoted at the optimized operating conditions of 200 ℃, 1 MPa, WHSV=25 hr-1 and H2/HC(molar ratio)=1.3. Among these catalysts, Pd/13X exhibited the maximum benzene conversion (90%) and the minimum light-cut production at the optimum conditions. The study on stability of catalysts shows that, the activity decline of Pd/13X catalyst is more than the other catalysts (from %90 to %81) in the specified 20 h time on stream, but so far the activity of this catalyst is highest in comparison with other catalysts at the end of the defined time (20 h).

    Keywords: Benzene hydrogenation, Heterogeneous catalyst, Catalytic Performance, Catalyst stability, Benzene conversion
  • Abbas Mohammadi *, Barat Ghobadian Pages 21-36

    A continuous process was designed and optimized at conceptual stage for biodiesel production from waste vegetable oils. Unlike previous studies, the process was optimized taking into account the technical and economic considerations, simultaneously, to find the optimum operating conditions in the commercial scale productions. The effect of major design variables on the process yield was studied by modeling of esterification and transesterification reactors. Free fatty acids’ (FFAs) mole fraction in feedstock, production rate, conversion and molar ratio of the reactants in both reactors were chosen as major design variables. By considering the economic potential as objective function of process optimization, the optimum FFA mole fraction was obtained as about 0.50 (24 wt %). Also, the optimum values of conversion and molar ratio of the reactants in the esterification and transesterification reactors were found as 82-89% (depending on the different production rates), 11:1 and 96%, 8:1, respectively. It was found that economic potential increases linearly as production rate increases. Therefore, the production rate should be set at its maximum possible practical value. The break-even point at the optimum values of these variables, as mentioned above, occurs at the production rate of 157 ton/yr.

    Keywords: Biodiesel, Conceptual design, Economic potential, Free fatty acids, Process Optimization
  • Sahar Jahangiri, Leila Amirkhani *, Abolfazl Akbarzadeh, Reza Hajimohammadi Pages 37-49

    In recent years, the development of nanoparticles has received much attention in the controlled drug release and biomedicine fields. This research aims to develop new methods for the physical modification of Fe3O4 superparamagnetic nanoparticles with polymers through physical retention. In this study, first, the degradable polycaprolactone-ethylene glycol copolymer and magnetic nanoparticles were synthesized. The anticancer drug doxorubicin was prepared using a dual-emulsion (w/o/w) copolymer containing magnetic iron nanoparticles. FT-IR, NMR, XRD, VSM, and, SEM analyzes were used to characterize copolymers and magnetic nanoparticles with drug-containing copolymer coating. The results showed that nanoparticles had superparamagnetic properties and their particle size was between 70-150 nm. The drug encapsulation efficiency was about 96%. The influence of pH and temperature on the drug release curve was investigated. The drug release was 31% and 26% after 144 hours in pH = 5.8 and 7.4 respectively. Since the extracellular fluid of the tumor is acidic, the rate of drug release in these media will be better than in other cells. The kinetics of the drug release was also studied based on zero-order, first-order, Higuchi and Korsmeyer-Peppas models. From the kinetic models, Higuchi was found to be the best model based on the correlation coefficient. The performance of the drug-loaded magnetic-copolymer nanoparticles with other similar studies was compared. The results revealed that the magnetic PCL-PEG copolymer with pH-sensitive properties can be used as an effective carrier for anticancer drugs delivery.

    Keywords: Magnetic nanoparticles, doxorubicin, Polycaprolactone-polyethylene glycol copolymer, targeted drug delivery, Kinetics of drug release
  • Mahdi Hefzi Lotfabadi, Mahdieh Abolhasani * Pages 50-64

    The Micromixing plays a key role in the most of industrial processes; enhancing its efficiency is very important issue. In this study, a typical rotating packed bed (RPB) reactor equipped with blade packing and high frequency ultrasonic transducers were designed to study micromixing efficiency using iodide/iodate reaction. The utilized ultrasonic transducers were ultrasonic atomizer humidifier with a frequency of 1.7 MHz. Taking advantage of both controllable high gravitational force and induced effects of high frequency ultrasound, simultaneously, in a small volume reactor is the novelty of the present work. The effects of different parameters like rotational speed, volumetric ratio, acid concentration, ultrasonic power and number of activ transducers were investigated with and without ultrasound field. With increasing the rotational speed and volumetric flow, the segregation index decreased and with increasing the acid concentration and volumetric ratio, the segregation index increased. In all of experiments, the segregation index decreased significantly under ultrasound field. Moreover, with increasing the ultrasonic power and number of active transducers the segregation index decreased. The obtained results indicated that the relative segregation index increased up to 41.1% under 1.7 MHz ultrasound field. Therefore, high frequency ultrasound waves can intensity micromixing, even in a high efficiency equipment like RPB.

    Keywords: RPB reactor, Blade packing, Micromixing enhancement, Segregation index, Ultrasonic waves
  • Zohreh Khoshraftar, Ahad Ghaemi *, Hossein Mashhadimoslem Pages 65-81

    In this research, silica gel as a low-cost adsorbent for carbon dioxide uptake was investigated experimentally. The samples were characterized by XRD, BET and FT-IR. It shows that as pressure was increased from 2 to 8 bar, CO2 adsorption capability improved over time. At a pressure of 6 bar and a dose silica gel of 1 g, the impact of temperature (25, 45, 65, and 85 °C) on CO2 adsorption capacity (mg/g) was determined. The process behavior was investigated using isotherm, kinetics and thermodynamic models. As the temperature rises at a constant pressure, the adsorption capacity decreases. The experimental data of carbon dioxide adsorption using silica gel have a high correlation coefficient with both Langmuir (0.998) and Freundlich (0.999) models. The results of the carbon dioxide adsorption kinetics with the silica gel adsorbent show that the correlation coefficient ( ) of the second-order model and Ritchie's second model are equal to 0.995 and have the highest value. The total pore volumes was 0.005119 (cm3 g-1) and the specific surface areas was 2.1723 (m2g−1). Maximum CO2 adsorption capacity at 25 °C near 8 bar was 195.8 mg/g.

    Keywords: Carbon dioxide, Adsorption, Silica gel, Isotherm, Kinetics
  • Mahdi Norouzi *, Seyyed Ghorban Hosseini, Manoochehr Fathollahi, Seyyed Alireza Rezvan Leylan, Sajjad Ebrahimi, Azam Karimian Pages 82-98

    Potassium superoxide tablets can be used in respiratory air regeneration systems within confined spaces such as spacecraft, submarines, coal mines and individual and collective masks. These tablets reacts with moisture and carbon dioxide in air and releases oxygen. In this study, The effect of four parameters; Pressure press (0.5, 2, 4 and 5 bar), humidity (10, 15, 20, 25 %), Catalyst additives (CuSO4.5H2O, (Cu2(OH)3Cl2)2, CuO, TiO2), H2O Absorbent additives (SiO2, LiCl, CaO, SiO2.Al2O3) and CO2 Absorbent additives (LiOH, NaOH, KOH, Ca(OH)2) were investigated in four levels using Taguchi method. The carbon dioxide absorption and Surface erosion were selected as criteria for optimizing the performance of Potassium Superoxide tablets based on analysis of variance and the optimal conditions of each were evaluated separately and simultaneously. The optimal conditions for higher carbon dioxide absorption and smaller Surface erosion include Humidity 15% , pressure press 4 bar, CuSO4.5H2O as Catalyst, SiO2 as H2O absorbent and Ca(OH)2 as CO2 absorbent. Experiments performed in the performance test show that the optimized tablets in this study show a 28% and 79% increase in carbon dioxide absorption compared to commercial tablets and pure potassium superoxide, respectively. The results showed that the catalysts with copper cation had the greatest effect on the performance of the tablets

    Keywords: Potassium Superoxide, Carbon Dioxide Absorption, surface erosion, optimaization, Taguchi method