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.

Catalytic performance of CeAPSO-34 molecular sieve with various cerium content for methanol conversion to olefin

Mehdi Sedighi,Mostafa Ghasemi,Alireza Jahangiri 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4

A series of CeAPSO-34s with various cerium contents was synthesized and characterized by multiple techniques such as XRD, SEM, BET, 29Si MAS NMR, NH3-TPD and CO2-TPD. NH3-TPD spectra showed that a number of acid sites, especially those of strong acidity, is reduced with the increasing of Ce incorporation. Incorporation of metal ions gave rise to more silica-islands in the CeAPSO-34 framework. CO2-TPD showed that basic sites on the surface of modified samples are due to the presence of Ce-containing species incorporation into the framework of CeAPSO-34 molecular sieves. The performance of the catalysts was studied in methanol to olefin reactions at 425 oC under the atmospheric pressure. The results showed that the incorporation of cerium ions had great effects on the structure and acidity of the molecular sieves. All SAPO-34 and MeAPSO-34 molecular sieves were the very active and selective catalyst for light olefins production. Cerium incorporation improved the catalyst lifetime and favored the ethylene and propylene generation. However, an excess Ce content resulted in an inferior catalytic performance and stability. Therefore, there existed optimal cerium content for a specific SAPO-34.

Matrix Metalloproteinase-13 - A Potential Biomarker for Detection and Prognostic Assessment of Patients with Esophageal Squamous Cell Carcinoma

Sedighi, Maryam,Aledavood, Seyed Amir,Abbaszadegan, MR,Memar, Bahram,Montazer, Mehdi,Rajabian, Majid,Gholamin, Mehran Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.6

Background: Matric metalloproteinase (MMP) 13 gene expression is increased in esophageal squamous cell carcinomas (ESCCs) and associated with increasing tumor invasion, lymph node involvement and decreased survival rates. Levels of the circulating enzyme may be elevated and used as a marker of tumor progression. In this study, clinical application of MMP-13 serum levels was evaluated for early detection, prediction of prognosis and survival time of ESCC patients. Materials and Methods: Serum levels of MMP13 were determined by ELISA in 66 ESCC patients prior of any treatment and 54 healthy controls for comparison with clinicopathological data through statistical analysis with Man Whitney U and Log-Rank tests. In addition, clinical value of MMP13 levels for diagnosis was evaluated by receiver operating characteristic (ROC) test. Results: The serum level of MMP-13 in patients (>250 pg/ml) was significantly higher than in the control group (<100 pg/ml) (p value=0.004). Also the results showed a significant correlation between MMP-13 serum levels with tumor stage (p value = 0.003), depth of tumor invasion (p value=0.008), involvement of lymph nodes (p value = 0.011), tumor size (p value = 0.018) and survival time. While there were no significant correlation with grade and location of tumors. ROC analysis showed that MMP-13 level is an accurate diagnostic marker especially to differentiate pre-invasive/ invasive lesions from normal controls (sensitivity and specificity: 100%). Conclusions: These findings indicate a potential clinical significance of serum MMP13 measurement for early detection and prognostic assessment in ESCC patients.

Experimental study and optimization of heavy liquid hydrocarbon thermal cracking to light olefins by response surface methodology

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.

Microbial fuel cell for oilfield produced water treatment and reuse: Modelling and process optimization

Majid Mohammadi,Mehdi Sedighi,Rajamohan Natarajan,Sedky Hassan Aly Hassan,Mostafa Ghasemi 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.1

Oilfield produced water is one of the vast amounts of wastewater that pollute the environment and cause serious problems. In this study, the produced water was treated in a microbial fuel cell (MFC), and response surface methodology and central composite design (RSM/CCD) were used as powerful tools to optimize the process. The results of two separate parameters of sulfonated poly ether ether ketone (SPEEK) as well as nanocomposite composition (CNT/Pt) on the chemical oxygen demand (COD) removal and power generation were discussed. The nanocomposite was analyzed using XRD, SEM, and TEM. Moreover, the degree of sulfonation (DS) was measured by NMR. A quadratic model was utilized to forecast the removal of COD and power generation under distinct circumstances. To obtain the maximum COD removal along with maximum power generation, favorable conditions were achieved by statistical and mathematical techniques. The findings proved that MFC could remove 92% of COD and generate 545mW/m2 of power density at optimum conditions of DS=80; and CNT/Pt of 14 wt% CNT- 86 wt% Pt.

The effects of SiO2/Al2O3 and H2O/Al2O3 molar ratios on SAPO-34 catalysts in methanol to olefins (MTO) process using experimental design

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.

Evaluation of solvent dearomatization effect in heavy feedstock thermal cracking to light olefin: An optimization study

Mostafa Ghasemi,Mohsen Nouri,Mehdi Sedighi,Majid Mohammadi 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.9

Response surface method was used to study the effect of aromatic extraction of heavy feedstock in thermal cracking. N-methylpyrrolidone as the solvent performing dearomatization of feedstock was at different temperature and molar solvent to oil ratios. Temperature, flow rate and steam-to-hydrocarbon ratio were in the range of 1,053-1,143K, 1-2 g/g, and 0.75-1.2 g/min, respectively. From the CCD studies, the effects of flow rate and coil outlet temperature were the key factors influencing the yield of light olefins. Ethylene and propylene yields increased more than 10%by dearomatization. C5+ decreased by 13% on average. Finally, we obtained the single maximum yield of ethylene,propylene, and simultaneous maximum yields for untreated and raffinate.