Iranian Journal of Chemical Engineering (IJChE)

Abstract The SrO-CaO-Al₂O₃ nanocatalysts were prepared and optimized using the co-precipitation method. In this work parameters affecting the catalytic performance for the production of biodiesel from sunflower oil have been investigated. Thev response surface methodology (RSM) has been used to assess the impact of operational conditions on the production of biodiesel, with the biodiesel yield as the response variable. The catalyst was found to be calcined at 600 °C, with a 5-hour calcination time, 75 minutes of the aging time, and a precipitation temperature of 50 °C as optimal conditions for the production of biodiesel. The results showed that the optimal reaction conditions were CH₃OH/oil=12/1 at 60 ˚C with the concentration of 6wt.%of the catalyst and reaction time of 3 h at stirring speed of 600 rpm. Furthermore, the biodiesel yield reached 99% under optimal operational conditions. The SrO-CaO-Al₂O₃ nanocatalysts were characterized by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transforms-infrared spectroscopy (FT-IR), and N₂adsorption–desorption measurements methods. The kinetic study has been done and the first order kinetic model was found  in agreement with experimental results (R²= 0.998). From the kinetic studies, E_a=41.57 kJ.mol^–1 and A= 5.25×10⁵ L.mol^-1s^-1 were obtained.

Abstract In this novel study, various heat exchangers are compared to identify the most efficient one for heat transfer. This investigation involves shell and tube, double pipe, and plate heat exchangers, of which each is filled with different nanofluids. Following several hours of operation, output temperatures are recorded. The effects of nanofluids, containing aluminium oxide, magnesium oxide, and silicon oxide, at concentrations of 0.2%, 0.4%, and 0.6% are simulated. These simulated results are then compared with laboratory findings. Among the tested nanofluids, the most significant enhancement in the heat transfer coefficient is demonstrated by magnesium oxide, achieving a 40% improvement. Additionally, graphs illustrating the increase in the heat transfer coefficient and Nusselt number for Reynolds numbers of 900, 600, 300, and 1800 are obtained and compared. Finally, tables summarizing the tests performed on different heat exchangers using various nanofluids are presented. Using laboratory-obtained temperatures, several parameters are calculated, including the logarithmic mean temperature difference, heat loss from hot water, heat gain by cold water, overall heat transfer coefficient, and total heat transfer. Based on these analyses, the shell and tube heat exchanger was purposed as the most efficient heat exchanger with the overall heat transfer coefficient of 5.06 W/m²K.

Abstract The study examines the operational lifespan and catalytic efficiency of the acetylene hydrogenation reactor at Amirkabir Petrochemical Company in Iran, a critical component in industrial olefin production. Acetylene, an undesirable by-product in olefin synthesis, adversely impacts profitability and polymer product quality. To mitigate these effects, the acetylene concentration in the feed stream must be reduced to below 0.5 ppm through catalytic hydrogenation. However, excessive conversion leads to ethane production, thereby reducing ethylene yield. This research uses a modeling approach, supported by industrial data, to investigate the reactor’s behavior under various conditions. A major focus is placed on the reaction kinetics to optimize operational parameters and minimize ethane production, which is less desirable than ethylene. The analysis includes key variables such as temperature, pressure, and the hydrogen-to-hydrocarbon ratio. Moving average method was used to smoothing 78 operational data in this work. Results showed the average absolute selectivity is less than 10%. Additionally, the study evaluates the role of carbon monoxide (CO) as a selective agent that enhances ethylene yield while reducing operational risks. The results showed that the main conversion takes place in the beginning of the reaction (first 1 m of the bed). Additionally, findings indicate that optimal management of these parameters can greatly improve reaction selectivity and the efficiency of the hydrogenation process. The results provide significant insights for refining practices in acetylene hydrogenation, suggesting strategies for improving product quality and operational efficiency in the petrochemical industry.

Abstract To reduce water production from oil and gas reservoirs, it is necessary to block certain fractures and layers of hydrocarbon formations. Although polymer gels are employed as water shut-off agents to reduce water production, they face challenges due to inefficiencies. This study aims to examine silicate-polymer gels, based on the factors influencing the formation of gel by focusing on controlling the gelation time of the silicate-polymer gelants at various temperatures and investigating the stability of gels. An experimental design was conducted based on 5 levels and 2 parameters, where these two parameters are the concentration of the polymer ranging from 0.06% to 0.3% by weight and the temperature ranging from 20 to 100 degrees Celsius in the presence of a crude oil from the southwest of Iran. Experimental results indicated that citric acid successfully covered the ions and effectively controlled the gelation time. Sodium silicate proved to be one of the main components, along with formation water, citric acid to mitigate the impact of formation ions on the gelation time, and the polymer itself. The presence of formation water led to an increase in gel strength and a decrease in the gelation time. Moreover, elevated temperatures resulted in shorter gelation times and lower viscosity in the polymer gel. Doubling the concentration of the polymer reduced the gelation time by 43%, while a two-fold increase in temperature decreased it by 54%. Increasing the concentration of the polymer indicated a decrease in the gelation time, and an increase in both gel strength and gel viscosity.

Abstract Nowadays, increasing demand for sustainable energy sources has led to a growing interest in using biomass as a renewable feedstock for producing hydrogen and methanol. The main objectives of this study involve simulation and economic analysis and evaluation of synthesis gas, hydrogen, and methanol production processes from various biomass sources using Aspen HYSYS software. Three lignocellulosic sources were waste wood biomass (WWB), thin hardwood chips biomass (THWCB), and almond shells biomass (ASB). In the first part of the simulation, the unrefined synthesis gas was produced through a multi-stage biomass gasification process. The outcomes reveal that the yield and composition of synthesis gas were increased by raising the steam-to-biomass ratio (SBR). Subsequently, an integrated model for hydrogen production from various biomass sources was examined through gasification in the presence of steam and oxygen through a water-gas shift (WGS) reaction and the separation and purification of the produced hydrogen using a pressure swing adsorption (PSA) unit. Finally, the hydrogen produced in the previous step was fed to the methanol synthesis unit. The results of the simulation of the gasification process of various lignocellulosic biomasses showed that the use of WWB, THWCB, and ASB can yield annual hydrogen production of 261,000, 349,344, and 361,656 kg, respectively. Consequently, the economic analyses indicated that hydrogen and methanol production from biomass is associated with significant efficiency and profitability. Furthermore, the comparison of synthesis gases' heating values derived from three biomasses revealed that the highest heating values were generated from ASB, THWCB, and WWB, respectively.

Abstract Ultrasonic distillation has been implemented as a green technology for desalination of saltwater due to its low energy consumption. It has also been proposed as an alternative to conventional distillation for separating water-ethanol mixtures, offering easy operating conditions and significant reduction in energy consumption (up to 80%). The Response Surface Methodology (RSM) was employed to optimize key parameters that influence ethanol enrichment, which includes initial ethanol concentration, solution height, and the quantity of ultrasonic modules. A central composite design (CCD) was utilized to reduce the number of experimental trials while formulating a predictive mathematical model. The findings suggest that elevated initial ethanol concentrations and an augmented number of modules significantly improved the ethanol concentration in the collected mist. Under optimal conditions—65% ethanol concentration, 2.5 cm solution height, and three modules—the purity of ethanol attained was akin to that achieved through conventional distillation techniques, accompanied by markedly diminished energy consumption. This research illustrates the potential of ultrasonic distillation for ethanol separation, offering operational efficiency and reduced energy demands.