Iranian Journal of Chemical Engineering (IJChE)

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

Abstract A continuous process was designed and optimized at a conceptual stage for the 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 fort he commercial scale productions. The effect of major variables on the yield of the process was studied by modeling esterification and transesterification reactors. The mole fraction of free fatty acids (FFAs) in the feedstock, production rate, conversion and molar ratio of the reactants in both reactors were chosen as major variables. By considering the economic potential as the objective function of the process optimization, the optimum mole fraction of FFA was obtained as about 0.50 (24 wt %). Also, the optimum values of the 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 the economic potential increases linearly as the 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.

Abstract 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 the 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 coatings. 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 the drug release in these media will be better than the same in other cells. The kinetics of the drug release was also studied based on zero-order, first-order, Higuchi and Korsmeyer-Peppas models. Among 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 that of 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.

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

Abstract In this research, silica gel as a low-cost adsorbent for the uptake of carbon dioxide 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, the CO2 adsorption capability improved over time. At a pressure of 6 bar and a dose of 1 g of silica gel, the impact of temperature (25, 45, 65, and 85 °C) on the 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 the 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 (R2) of the second-order model and Ritchie's second model are equal to 0.995 and have the highest value. The total pore volume was 0.005119 (cm3 g-1) and the specific surface area was 2.1723 (m2g−1). The maximum CO2 adsorption capacity at 25 °C near 8 bar was 195.8 mg/g.

Abstract 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 react with moisture and carbon dioxide in air and release oxygen. In this study, The effect of five parameters; the pressing pressure (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 the Taguchi method. The carbon dioxide absorption and Surface Erosion were selected as criteria for optimizing the performance of Potassium Superoxide tablets based on the analysis of variance and the optimal conditions of each were evaluated separately and simultaneously. The optimal conditions for the higher carbon dioxide absorption and smaller Surface Erosion include the Humidity of 15 %, pressing pressure of 4 bar, CuSO₄.5H₂O as the Catalyst, SiO₂ as the H₂O absorbent and Ca(OH)₂ as the CO₂ absorbent. Experiments performed in the performance test show that the optimized tablets in this study show a 28 % and 79 % increase in the 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.