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Showing 4 results for Towfighi


Volume 2, Issue 3 (Autumn 2019)
Abstract

Due to increase in global demand of propylene, many extensive studies and research have been done to find alternative method for lower energy consumption and efficiency. In this research, gamma alumina is used for molybdenum catalyst base in oxidative dehydrogenation process of propane, in order to produce the propylene. The catalysts are prepared based on wet impregnation method. The analysis of  FTIR, XRD, BET, SEM, and XRF are done to evaluate and determine the  characteristics of prepared catalysts. Central composition method is employed to study the influence of reaction temperature, molybdenum loading percentage, oxygen to propane ratio, and the effect of interactions between them in propylene production. The molybdenum in the range of 4-16%, propane to oxygen ratio in ‎the range of 1-3%, and temperature in the range of 380-540 ºC are the input parameters of ‎the central composite method. Finally, according to reactor test and analysis of the results of the Design expert software, it is shown that the predicted models for propane conversion, propylene selectivity, and efficiency persentage of oxidation dehydrogenation are about 95%. Maximum of efficiency percentage with a value of 14.02% is obtained at 487 ºC, 11.22% molybdenum percentage, and propane to oxygen ratio of 1.5, which in experimental results, achieving an accuracy of 94% is possible as compared to the optimal design of the test design model.

Volume 2, Issue 4 (Winter 97 2019)
Abstract

In this study, sonochemical synthesis was used to prepare nanostructured HZSM-5 catalysts. The three most effective ultrasound related variables including ultrasound power, irradiation time, and sonication temperature were investigated. The combined effect of these variables on relative crystallinity and mean crystal size of HZSM-5 nanocatalysts was studied using a central composite design. Higher crystallinity and lower crystal size were obtained by increasing ultrasound power, irradiation time, and sonication temperature while there was an optimum range for mentioned variables. The maximum relative crystallinity and minimum mean crystal size were obtained as 55.51% and 62.37 nm, respectively, under the optimal conditions of ultrasound power (231 W), irradiation time (21.18 min), and sonication temperature (42.68 °C). The results confirmed that sonochemical method considerably increased crysatllinity and reduced crystal size of HZSM-5 nanocatalysts at lower time. Hydrothermal method produced catalyst with full crystallinity and mean crystal size of 893 nm with 120 min aging and 48 h crystallization in autoclave while sonicated HZSM-5 catalyst with 21 min sonication and 4 h crystallization has 55.51% crystllinity and 62.37 nm mean crystal size. On the other hand, no HZSM-5 phase was formed in hydrothermal method with 120 min aging and 4 h crystallization in autoclave. These results strongly suggests that a catalyst with smaller crystal size, higher crystallinity and BET surface area at lower crystallization time can be obtained by using ultrasound instead of aging step in HZSM-5 synthesis

Volume 6, Issue 1 (Spring 2022)
Abstract

Research subject: Because of the rising global demand for propylene, various extensive studies and research have been done in order to develop alternative ways that are both more energy-efficient and require less energy. In this research, CuBTC is used as a manganese catalyst base in the oxidative dehydrogenation of propane to produce propylene. The wet impregnation method is used to manufacture the catalysts.
Research approach: Wet impregnation is used to prepare the catalysts, which is a step in the manufacturing process. Analyses such as FTIR, XRD, BET, SEM, and EDX are used to examine and describe catalysts that have been created. On the basis of the central composition method, we have investigated the impacts of reaction temperature, manganese loading percentage, oxygen-to-propylene ratio, and their interactions on the synthesis of propylene in this study. The central composite method's input parameters include manganese concentrations ranging from 1 to 5 percent, a propane-to-oxygen ratio ranging from 1 to 3 percent, and a temperature ranging from 140 to 280 degrees Celsius.
Main results: After that, it is shown that the projected models for propane conversion, propylene selectivity, and oxidative dehydrogenation efficiency percentage are about 95 percent based on reactor testing and evaluation of the Design-Expert software results. It was possible to improve the efficiency of the oxidation dehydration process by 4.9 percent by using a conversion percentage of 28.38 percent, a selectivity of 18.14 percent at 278 degrees Celsius, a metal oxide loading of 3.74 percent, and propane to oxygen ratio of 1.5 percent. When laboratory data were compared to predicted data, the correlation coefficient was 93% in favor of the laboratory data.
 

Volume 6, Issue 2 (Summer 2022)
Abstract

Research Subject: In recent years, industrial-scale production of propylene based on oxidative dehydrogenation of propane has been of particular importance due to the lack of thermodynamic limitations. In this regard, the use of natural zeolites with high abundance and low price has placed a special position. In this research, perlite natural zeolites were treated with ionic liquid solution and acid, then supported vanadium catalysis were synthesized. Performance of catalysis were investigated in oxidative dehydrogenation of propane to propylene process with a mixed feed of propane and air in a fixed bed quartz reactor under condition of atmospheric pressure and temperature of 500˚C with a flow rate of 40000 h-1 (GHSV).
Research Approach: In this study, natural perlite support as a source of aluminum oxide (Al2O3) and silica (SiO2) was ion exchanged by one molar solution of ammonium nitrate (NH4NO3 1 M). Continuously, to investigate the effect of delamination, different acid molar concentrations of nitric acid (HNO3) equal to 0.75, 1.5, and 2.25 were used and then compared with the just modified ion exchange sample without acid leaching (V/PERLIT-I). Dry vanadium impregnation, as an active metal, was carried out to synthesize 8% wt. catalysts. X-ray diffraction analyzes (XRD), scanning electron microscopy (FE-SEM), and ammonia Temperature-programmed desorption program (NH3-TPD) were used to characterization and evaluate the properties of the catalyst.
Main Result: The results showed that the concentration of acid used affects the conversion and selectivity of the catalysis. In comparison, a significant difference was observed between the performance of V/PERLIT-I sample compared to V/PERLIT-IA samples. The maximum selectivity value for V/PERLIT-IA(2.25) was 74%. According to the results, the treated perlite support with suitable selectivity can be considered in the studies of use as an industrial support.

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