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Mina Alyani,Jafar Towfighi,Seyed Mojtaba Sadrameli 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.6
The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 ℃. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 ℃, 44 hr^(−1) and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.
H2S oxidation by multi-wall carbon nanotubes decorated with tungsten sulfide
Ali Mohamadalizadeh,Jafar Towfighi,Morteza Adinehnia,Hamid Reza Bozorgzadeh 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.4
Tungsten sulfide catalysts decorated on single and multiwall carbon nanotubes (SWNTs & MWNTs) and activated carbon were synthesized, and XRD, ICP, SEM, TEM and ASAP analyses were employed to acquire the characteristics of each catalyst. Afterwards a gas flow containing 5,000 ppm of H2S was passed over the catalyst in gas hour space velocity (GHSV) of 5,000 h−1, temperature of 65 oC, steam volume percent of 20 and O2/H2S ratio equal to 2. The results revealed that the catalyst supported on MWNTs exhibited higher conversion amongst its counterparts. Then effects of GHSV, steam volume percent in the feed, catalyst loading and temperature were investigated on conversion of hydrogen sulfide to elemental sulfur for tungsten sulfide catalyst decorated on MWNTs.
Nanoclays as nano adsorbent for oxidation of H_2S into elemental sulfur
Ali Mohamadalizadeh,Jafar Towfighi,Alimorad Rashidi,Mehrdad Manteghian,Ali Mohajeri,Rohollah Arasteh 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5
Modified bentonites were used for the oxidation of H_2S into elemental sulfur. Active phases such as iron and cobalt sulfide were added to supports Cloisite 30B and 15A. The produced nano adsorbents were characterized by X-Ray diffraction, ICP, BET surface area and SEM. Selective oxidation of H_2S was carried out over the nano adsorbent in the experimental setup. The tests were performed at 70 and 180℃, under atmospheric pressure and in the presence of 5,000 ppm of H_2S in the inlet gas stream. The results confirmed the increase in the distribution of active metals and activity of Cloisite 30B, in comparison with Cloisite 15A. Cobalt-containing support showed significant improvement in the capacity of H_2S removal, and in the outlet stream less than 50 ppm of H_2S was detected.
Mehdi Alibolandi,Jafar. Towfighi. Darian,Maryam Ghaedian,Sayed Javid Royaee,Amin Shafeghat 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.11
This study modelled and optimized the oxidative desulfurization of gas condensate with ozone, as a gaseous oxidant. Experiments in this study were non-catalytic, and sulfone extraction was done by acetone. Response surface methodology was applied for the experimental design, mathematical modeling, and optimization using Design- Expert® software. The influence of effective variables and their interaction on the response was also investigated. For the first time, non-catalytic ozonation of this feed was performed on the oxidative desulfurization process. The developed model properly fitted the experimental results. The accuracy of the model was confirmed, while this model predicted 95% desulfurization would result in the optimized conditions, and the actual value of desulfurization obtained was 95.8%. Further, the results indicated interaction between the superficial gas velocity of ozone and coefficient of oxidant- to-sulfur molar ratio. GC-SCD revealed that DBT was the most refractory component in comparison with the other sulfur components in the gas condensate. It was also found that 84.3% desulfurization occurred just with oxidation and sedimentation of sulfones and without solvent extraction.
Kobra Rahimi,Jafar Towfighi,Mehdi Sedighi,Shima Masoumi,Zahra Kooshki 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.35 No.-
To investigate the effects of silicon and water content on SAPO-34 catalyst, a number of experiments byusing response surface methodology of molar ratios of SiO2/Al2O3 = 0.1–0.6 and H2O/Al2O3 = 50–120were performed. The catalytic performances of prepared SAPO-34 samples at 410 8C and 30 wt.%methanol in water for MTO process were investigated. Due to relatively high crystallinity and smallcrystal size (1.3 mm); SiO2/Al2O3 = 0.17 and H2O/Al2O3 = 109.75 catalyst showed high total light olefinsselectivity (71.45%). ANOVA results indicated that the light olefins selectivity was influenced more bychanging of SiO2/Al2O3 molar ratio rather of H2O/Al2O3 molar ratio.
Determination of yield distribution in olefin production by thermal cracking of atmospheric gasoil
Sorood. Zahedi. Abghari,Jafar. Towfighi. Darian,Ramin. Karimzadeh,Mohammad Reza Omidkhah 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.4
A pilot plant was designed and set up to study the thermal cracking of atmospheric gasoil. Based on the CCD (central composite design) method, a set of systematic experiments were designed and carried out. The designed variables were COT (coil outlet temperature), steam ratio and feed flow rate. The ranges of these variables were, respectively, equal to 716-884 oC, 0.46-1.136 and 0.977-6.02 g/min. The obtained minimum and maximum yield of ethylene was, respectively, equal to 1.7% and 30.9%, as well as the maximum yield of propylene was 12.2%. To predict the yield distribution of products and the coke formation in the range of operating conditions, a mechanistic model was developed based on experimental results. To analyze and characterize the atmospheric gasoil, a novel algorithm was applied. This algorithm utilized density, ASTM distillation curve, H/C ratio and the total aromatic fraction and generates the detail analysis of feedstock including paraffinic, naphthenic, aromatics and poly aromatic compounds.
Kamyar Keyvanloo,Mehdi Sedighi,Jafar Towfighi 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.4
Response surface methodology coupled with central composite design (CCD) was used to investigate the effects of operating variables, namely, coil outlet temperature (COT), flow rate and steam ratio, on the yield of light olefins (ethylene and propylene) in thermal cracking of heavy liquid hydrocarbon. From the CCD studies the effects of COT and flow rate were concluded to be the key factors influencing the yield of light olefins. Based on this experimental design, two empirical models, representing the dependence of ethylene and propylene yields on operating conditions,were developed. The single maximum response of ethylene and propylene yields and simultaneous maximization of both responses have also been obtained at the corresponding optimal independent variables. The results of the multi-response optimization could be used to find the suitable operating conditions.
Kinetic modeling formulation of the methanol to olefin process: Parameter estimation
Mehdi Sedighi,Hussein Bahrami,Jafar Towfighi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
Detailed kinetic models at the elementary step level were developed for the methanol to olefins (MTO) process over SAPO-34 catalyst. Starting from believable mechanisms, forming primary products was modeled rigorously by the Hougen–Watson formalism. Discrimination of kinetic equations and calculation of the parameters of best fit were performed by solving the mass conservation equations of the main products of the kinetic scheme. For rate constants, preexponential factors and apparent activation energies were then calculated according to the Arrhenius equation. For thermodynamic constants, the difference between apparent activation energies of forward and reverse reaction was considered. The kinetic model fits well the experimental data, which is obtained in a fixed bed reactor. The results showed that rising space-time is favorable for olefin yields while an optimum temperature might produce the maximum olefin.
Abdolsamad Zarringhalam Moghaddam,Somayeh Alijani,Mohammad Vaez,Jafar Towfighi 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.10
TiO2 nanoparticles were synthesized by the P-25 powder modified sol-gel method under different TTIP (Titanium tetraisopropoxide) concentrations, P-25 loading and the gelation pHs. Structural properties of nanoparticles were characterized by XRD, FESEM and BET analysis. Results show that crystallinity level, particle size and the surface area are a function of P-25 loading and gelation pH, whereas TTIP concentration affects only the crystalline composition. Response surface methodology based on central composite design was used to optimize these synthesis parameters in photodegradation of Acid Red 73. The degradation efficiency was significantly affected by P-25 loading,pH value of gelation and the interaction effect between TTIP concentration and P-25 loading. The optimal values of parameters were found to be a pH of 1.34, a TTIP concentration of 0.25M and a P-25 loading of 39.76 g/L. At optimal synthesis conditions, TiO2 film was coated on alumina foam and its structural properties were characterized by XRD,SEM and BET technique. The photocatalytic activity of the as-prepared films was found to be higher than that of the films prepared by the sol-gel method and those made from the slurries of P-25. The reasonable photocatalytic performance and good stability offered by the optimized film make it as an effective alternative for large application of water treatment.