Published Papers ( Journals)

39. Investigation of a novel combination of adsorbents for hydrogen purification using Cu-BTC and conventional adsorbents in pressure swing adsorption

Jamali, S., Mofarahi, M. & Rodrigues, A.E.

Adsorption vol. 19 issue 1 February 2013. p. 101 - 110

DOI:  ISSN: 0929-5607.



This study is an attempt to simulate and analyze a lab-scale two-bed pressure swing adsorption in order to investigate the performance of three different adsorbents (Cu-BTC as a new generation adsorbent, activated carbon, and zeolite 5A) with different feed compositions, and find a novel combination of layered bed. Four different flows of steam methane reforming reactor were considered as inlet feeds for hydrogen purification. Comparison of the feeds with different compositions showed that in the presence of high amounts of impurities, an adsorption bed of Cu-BTC produces hydrogen at a higher purity than activated carbon, zeolite 5A, or an activated carbon-zeolite 5A layered bed. The simulation results from feed 4 (H2:CO2:CO:CH4 = 0.4574:0.3174:0.0622:0.1630) with high amounts of impurities, showed that the use of Cu-BTC leads to hydrogen purity of up to 97.22%, while activated carbon, zeolite 5A, and the layered bed cannot improve the purity beyond 86.46%. This work shows that Cu-BTC is capable of being used in the first layer of layered beds. This was confirmed by comparing the performance of the three combinations of Cu-BTC, activated carbon, and zeolite 5A. The first configuration of the three adsorbents, in which the Cu-BTC was used as the first layer, purified hydrogen up to + 99.99% and recovered it up to 21.25%.

Keywords: Pressure swing adsorption; Layered bed; Cu-BTC; Simulation; Hydrogen purification 



38. Thermodynamic modelling using e-UNIQUAC model for CO2 absorption by novel amine solutions: 1-Dimethylamino- 2-propanol (1DMA2P), 3-dimethylamino-1-propanol (3DMA1P) and 4-diethylamino-2-butanol (DEAB)

Morteza Afkhamipour, Masoud Mofarahi, Chang-Ha Lee

Fluid Phase Equilibria 2018, xxx, pp. xx-xx  ISSN: 0378-3812






The proper selection of thermodynamic models is an important step in the design and simulation of CO2 removal processes using amine solutions. In this study, we aim to study the thermodynamic behaviour of the CO2 removal process by employing the extended-universal quasichemical (e-UNIQUAC) model for three novel amine systems, namely CO2+1DMA2P + H2O, CO2+3DMA1P + H2O, and CO2+DEAB + H2O. The thermodynamic behaviour was studied in terms of the CO2 loading of amines, the ion speciation profiles, the isothermal pressure-composition (Pxy) profiles, and the pH of the amine solutions. Adjustable parameters of the model include binary interaction parameters, and the volume and surface area parameters of the amine and protonated amine were determined using different objective functions based on the experimental data available in the literature. The ion and molecular speciation profiles are obtained and compared with nuclear magnetic resonance (NMR) data for CO2+1DMA2P + H2O and CO2+DEAB + H2O systems. The model predicted the experimental data with average absolute relative deviations (AARDs) of 8.06%, 13.39% and 16.50% for CO2 loading values of DEAB, 1DMA2P, and 3DMA1P, respectively. In addition, the results of Pxy profiles at different temperatures show that the azeotrope does not form in the 3DMA1P + H2O system. The adjustable parameters and predicted data of the applied e-UNIQUAC model may contribute to the rate-based simulation of CO2 absorption processes using novel amine systems.

Keywords: e-UNIQUAC; Amine; CO2 loading; Adjustable parameters; Chemical speciation



37. Effects of operating parameters of packed columns on the KGav for CO2 absorption by amine solutions using optimization–simulation framework

Morteza Afkhamipour and Masoud Mofarahi,

Sep. Purif. Technol. 2018, 202, pp 86-102








The aim of this study is to investigate the effects of key operating parameters of packed absorption columns on the performance of mass transfer considering the volumetric overall mass transfer coefficient (). The effects were studied for CO2 absorption by using 4-diethylamino-2-butanol (DEAB) and N,N-Diethylethanolamine (DEEA) mixed with monoethanolamine (MEA) as novel amine solutions. In doing so, an optimization–simulation framework was developed based on the two-film theory model, thermodynamic model, multi-layer perceptron neural network (MLPNN), and statistical technique. To predict the CO2 loading as one of the parameters in input of MLPNN model, the Deshmukh–Mather model, as an electrolyte thermodynamic model, was developed for CO2 + DEAB + H2O and CO2 + DEEA + MEA + H2O systems. The effect of enhancement factor on the was considered based on the series resistances model including pseudo-first order enhancemnt factor and instantaneous enhancemnt factor. To optimize and rank the key operating factors that simultaneously affect the , the Taguchi method was used. Statistical indices showed that our model could efficiently predict the experimental data with AARDs of 5.6%, 0.43% and 4.96%, respectively, for data, CO2 loading data of DEAB and DEEA + MEA. A significant order of process variables affecting the values was as CO2 mole fraction > amine temperature > amine flow rate > gas temperature > packing type > CO2 loading > amine concentration. Moreover, the sensitivity analysis results showed that by increasing the CO2 mole fraction in gas feed, gas temperature, and CO2 loading, the values decreased, and by increasing the amine concentration, amine flow rate, and amine temperature, the values increased.




36. Experimental Measurement of Dissociation Condition for Carbon Dioxide Hydrates in the Presence of Methanol/Ethylene Glycol and CaCl2 Aqueous Solutions

Majid Dastanian, Amir Abbas Izadpanah, and Masoud Mofarahi

Chem. Eng. Data, 2018, 63 (5), pp 1675–1681

DOI: 10.1021/acs.jced.8b00021






In this study, hydrate dissociation conditions of carbon dioxide in the presence of methanol/ethylene glycol + CaCl2 at the temperature range of 262.2–276.8 K and the pressure range of 1.49–3.36 MPa, not found in the related literature, were measured and reported. The equilibrium data were conducted by isochoric pressure search method. The experimental findings showed that methanol inhibition power was superior to that of ethylene glycol at similar mass concentrations. An available thermodynamic model was used to predict and compare the results with the measured experimental data. In addition, in order to investigate the inhibitory effect of various inhibitors as well as their synergy to one another, the suppressed temperature of hydrate formation in the presence of various inhibitory solutions used in this work and also in the similar studies in the literature was examined. This measurement indicated no effect of pressure on the reduction amount of suppressed temperature for each solution, so that it can be considered to be independent of pressure. Moreover, at low concentrations synergy level of CaCl2 with methanol or ethylene glycol was negligible, indicating no effect of these two inhibitors on the performance of each other. By increasing the concentration of alcohol and glycol, this rule was interrupted and inhibitors interacted each other and the synergy level increased.


35. Thermodynamic Consistency Test for Experimental Hydrogen Solubility Data in Alkenes

Mohammad Jamali, Amir Abbas Izadpanah, and Masoud Mofarahi

Chem. Eng. Data, 2017, 62 (12), pp 4371–4376

DOI: 10.1021/acs.jced.7b00729






In this communication, a thermodynamic consistency test is performed on the isothermal solubility of hydrogen in alkenes and vapor–liquid equilibrium data for systems containing hydrogen and alkenes. The improved Peng–Robinson equation of state was used for this purpose. The fugacity coefficient of each component and compressibility factor of liquid and vapor phases were calculated by this equation of state. Thermodynamic consistency tests have been performed by rewriting the Gibbs–Duhem equation in terms fugacity coefficient and using the area test method. The results showed that most of the equilibrium data of the liquid phase were consistent, but for the vapor phase less than one-half of the data was consistent.

34.Prediction of heat capacity of amine solutions using artificial neural network and thermodynamic models for CO2 capture processes

Morteza Afkhamipour, Masoud Mofarahi,Tohid Nejad Ghaffar Borhani, Masoud Zanganeh

Heat and Mass Transfer, 54(3), 855-866   ISSN: 1432-1181







In this study, artificial neural network (ANN) and thermodynamic models were developed for prediction of the heat capacity (CP) of amine-based solvents. For ANN model, independent variables such as concentration, temperature, molecular weight and CO2 loading of amine were selected as the inputs of the model. The significance of the input variables of the ANN model on the CP values was investigated statistically by analyzing of correlation matrix. A thermodynamic model based on the Redlich-Kister equation was used to correlate the excess molar heat capacity (CEP) data as function of temperature. In addition, the effects of temperature and CO2 loading at different concentrations of conventional amines on the CP values were investigated. Both models were validated against experimental data and very good results were obtained between two mentioned models and experimental data of CP collected from various literatures. The AARD between ANN model results and experimental data of CP for 47 systems of amine-based solvents studied was 4.3%. For conventional amines, the AARD for ANN model and thermodynamic model in comparison with experimental data were 0.59% and 0.57%, respectively. The results showed that both ANN and Redlich-Kister models can be used as a practical tool for simulation and designing of CO2 removal processes by using amine solutions.




33.An experimental and modeling study of CO2 solubility in a 2-amino-2-methyl-1-propanol (AMP) + N-methyl-2-pyrrolidone (NMP) solution

Peyman Pakzad, Masoud Mofarahi, Amir Abbas Izadpanah,Morteza Afkhamipour,Chang-Ha Lee


Chemical Engineering Science   ISSN: 0009-2509







In this study, an experimental setup based on the static-synthetic method was used to measure the new experimental data of CO2 solubility in an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) + N-methyl-2-pyrrolidone (NMP) solution. For the static-synthetic method, the mass balance of compositions and the pressure–volume–temperature conditions were used for measuring the amount of absorbed CO2 by the AMP+NMP solution. The measurements were performed over a temperature range of 313.15 to 353.15 K, CO2 partial pressure up to 316.7 kPa, and in different concentrations of the AMP+NMP solution. Two models, modified Kent–Eisenberg, and Deshmukh–Mather, based on the empirical correlations and activity-fugacity approach, respectively, were used for the prediction of experimental data. The parameters of the equilibrium constants of the protonation and carbamate reactions for the modified Kent–Eisenberg model and the interaction parameters for Deshmukh–Mather model were obtained. For validation of our setup, a new set of experimental data for the solubility of CO2 in an aqueous solution of AMP, methyldiethanolamine (MDEA) and diethanolamine (DEA) were measured and compared with existing experimental data in the literature, and good results were obtained. The results of the modeling study showed that the Deshmukh–Mather model gave a better prediction of experimental CO2 loadings data than the modified Kent–Eisenberg. Also, the results showed that the solubility of CO2 in an aqueous solution of AMP+NMP increases as the CO2 partial pressure increases while the temperature decreases.



32. A modeling-optimization framework for assessment of CO2 absorption capacity by novel amine solutions: IDMA2P, 1DEA2P, DEEA, and DEAB

Afkhamipour, M.; Mofarahi, M.

Journal of Cleaner Production  2018,171(10) , pp 234-249   ISSN: 0959-6526







In this study, new experimental data of CO2 equilibrium solubility for an aqueous solution of 1DMA2P, a novel ternary amine, are presented over a CO2 partial pressure range of 3–168 kPa, at different concentrations of 1DMA2P (2, 3 and 4 M), and in a temperature range of 298.15–333.15 K. Besides, new experimental data of viscosity and density are reported in a concentration range from 20 wt% up to pure 1DMA2P, in a temperature range of 298.15–333.15 K, and in atmospheric pressure. CO2 equilibrium solubility data were predicted by Deshmukh–Mather (D-M) thermodynamic model. From the experimental data of density and viscosity, thermodynamic properties including the thermal expansion coefficient (αp), excess molar volume (VE), viscosity deviation (∆η), activation molar enthalpy (∆H), activation molar entropy (∆S), and activation molar Gibbs free energy (∆G) were obtained. We have modeled and predicted the experimental data of viscosity based on Eyring’s theory and nonrandom two-liquid (NRTL) and Wilson models. The results showed that the Eyring-Wilson model predicts the experimental viscosity data better than Eyring-NRTL. For CO2 equilibrium solubility, D-M model gave a good prediction with an absolute average relative deviation of 2.64%.

Keywords: CO2 solubility, Viscosity, Density, 1DMA2P, Thermodynamic models


31.Experimental measurement and modeling study on CO2 equilibrium solubility, density and viscosity for 1-dimethylamino-2-propanol (1DMA2P) solution

Afkhamipour, M.; Mofarahi, M.

Fluid Phase Equilibria 2018,457, pp. 38-51  ISSN: 0378-3812






In this study, new experimental data of CO2 equilibrium solubility for an aqueous solution of 1DMA2P, a novel ternary amine, are presented over a CO2 partial pressure range of 3–168 kPa, at different concentrations of 1DMA2P (2, 3 and 4 M), and in a temperature range of 298.15–333.15 K. Besides, new experimental data of viscosity and density are reported in a concentration range from 20 wt% up to pure 1DMA2P, in a temperature range of 298.15–333.15 K, and in atmospheric pressure. CO2 equilibrium solubility data were predicted by Deshmukh–Mather (D-M) thermodynamic model. From the experimental data of density and viscosity, thermodynamic properties including the thermal expansion coefficient (αp), excess molar volume (VE), viscosity deviation (∆η), activation molar enthalpy (∆H), activation molar entropy (∆S), and activation molar Gibbs free energy (∆G) were obtained. We have modeled and predicted the experimental data of viscosity based on Eyring’s theory and nonrandom two-liquid (NRTL) and Wilson models. The results showed that the Eyring-Wilson model predicts the experimental viscosity data better than Eyring-NRTL. For CO2 equilibrium solubility, D-M model gave a good prediction with an absolute average relative deviation of 2.64%.

Keywords: CO2 solubility, Viscosity, Density, 1DMA2P, Thermodynamic models



30.Rate-based modeling and sensitivity analysis of a packed column for post-combustion CO2 capture into a novel reactive 1-dimethylamino-2-propanol (1DMA2P) solution

Afkhamipour, M.; Mofarahi, M.

International Journal of Greenhouse Gas Control  vol. 65 October, 2017. p. 137-148     ISSN: 1750-5836






This study presents the rate-based modeling for CO2 absorption into a novel amine solution, 1DMA2P, in a column packed with random packing. The rate-based model has been developed on the basis of five key elements: the heat and mass transfer balances, thermodynamic model, estimation of physicochemical properties, enhancement factor model, and calculations of column internal hydraulic. The heat and mass transfer balances were derived based on the two-film theory by taking a differential element from a packed column. The Deshmukh–Mather model as thermodynamic framework was incorporated in the rate-based model to calculate the CO2 loading of 1DMA2P solution. The physicochemical properties such as amine density, amine viscosity, amine surface tension, amine heat capacity, and diffusivity of the CO2 in amine solution were predicted based on the thermodynamic correlations developed in this study. The rate-based model was numerically solved and validated by using experimental data of the CO2 concentration along the height of a packed column. In addition, we have performed the sensitivity analysis on the profiles of CO2 and H2O and profiles of gas and liquid temperature by applying four different mass transfer correlations of the random packing. Also, the effects of different operating parameters were investigated on the CO2 mole fraction profiles in gas phase. The rate-based model predicted the experimental data of CO2 concentration along the height of a packed column with an AARD% of 2.18. The sensitivity analysis showed that Onda’s correlations provided good results in comparison with other analyzed correlations.

Keywords:rate-based,Deshmukh-Mather,Physicochemical properties,Sensitivity analysis,1DMA2P,Packed column



29.Application of inverse method to predict the breakthrough curve in fixed-bed adsorption

Hossein Rahideh, Masoud Mofarahi, Parviz Malekzadeh 

Inverse Probl Sci Eng, 2018, 26 (4), pp 581–600






In this paper, at first by means of the differential quadrature element-incremental method as a computationally efficient and accurate numerical tool in conjunction with the Newton-Raphson method, the behaviour of the bicomponent fixed-bed adsorption is studied. The kinetics of the adsorption is formulated based on the linear driving force (LDF) approximation. Then, an inverse algorithm is employed to estimate the overall mass transfer coefficients of the adsorption column by using the measured time histories of the mole fractions of outlet multicomponent. The method allows one to obtain the values of the LDF mass transfer coefficients for the different adsorbents and adsorbates. The conjugate gradient method is adopted for the optimization procedure of the inverse algorithm. The robustness and applicability of the present inverse approach are demonstrated by solving different examples with the exact data of the known kinetics.


28. Phase Equilibria of Carbon Dioxide Hydrates in the Presence of Methanol/Ethylene Glycol and KCl Aqueous Solutions

Majid Dastanian, Amir Abbas Izadpanah, and Masoud Mofarahi

J. Chem. Eng. Data, 2017, xx (x), pp xxx–xxx

DOI: 10.1021/acs.jced.7b00146   




In this study, the experimental data for dissociation conditions of carbon dioxide hydrates in the presence of 0.05 and 0.1 mass fraction KCl solution + 0.1 and 0.2 mass fraction methanol and ethylene glycol were measured and then reported at different temperatures and pressure ranges not available in the related literature. The phase equilibrium curves were drawn using an isochoric pressure-search method. To validate the used apparatus and the experimental findings of the current study and also to show the inhibition effects of the aqueous solutions used in this study, the experimental values were compared with some selected experimental data from the literature about the dissociation conditions of carbon dioxide hydrates in the presence of pure water and aqueous solution with 0.05 mass fraction KCl. Finally, to examine the inhibitory effect of various inhibitors and their synergies on each other, the suppressed temperature for hydrate formation was evaluated in the presence of different inhibitor solutions. This value showed that the rate of suppressed temperature for hydrate formation for each solution has been almost constant in various pressures. The synergy effect of KCl with methanol or glycol at low concentrations is negligible indicating that these two inhibitors have no impact on each other. It was also shown that, by increasing the concentration of the inhibitors, this rule was violated, the inhibitors were affected by each other, and the amount of inhibition effect increases. This synergy is of utmost importance for oil and gas pipelines and also for the industrial equipment that naturally contain some salt, in which alcohol or glycol will be added to prevent hydrate formation.


27. Review on the mass transfer performance of CO2 absorption by amine-based solvents in low- and high-pressure absorption packed columns


Morteza Afkhamipour & Masoud Mofarahi  

RSC Adv., 2017,7, 17857-17872
DOI: 10.1039/C7RA01352C, Review Article





The gas-phase volumetric overall mass transfer coefficient (KGaV) plays a key role in the assessment of an absorption packed column's performance since it determines the height of an absorber column. The effective and useable data provided by KGaV is necessary for designing and scaling up absorption packed columns. This study provides the first comprehensive review of mass transfer performance in terms of KGaV for CO2 (KGCO2aV) absorption into amine solutions for absorber columns with random and structured packing. To date, researchers associated with the KGCO2aV parameter have focused on two main fields: experimental works and developing empirical correlations. For experimental works, KGCO2aV has been evaluated in the literature for a large number of conventional and improved amines over a range of operating parameters in laboratory-scale packed columns. In addition, researchers have developed empirical correlations for KGCO2aV based on operating parameters affecting KGCO2aV and physical properties. The details of research determining the KGCO2aV have been reviewed for low- and high-pressure absorption packed columns. Finally, directions for future research of the mass transfer performance for absorber packed columns in the CO2 capture process have been discussed.


26. An inverse method to estimate adsorption kinetics of light hydrocarbons on activated carbon


H. Rahideh, M. Mofarahi, P. Malekzadeh

Computers & Chemical Engineering, 2016, 93, 197–211

DOI: 10.1016/j.compchemeng.2016.06.014




An inverse algorithm to estimate the adsorption kinetics inside the spherical particles in a constant molar flow (CMF) gas adsorber reservoir by measuring the bulk pressure is developed. The formulation includes Knudsen diffusion, surface diffusion, slip and viscous flows. To obtain an efficient algorithm, the conjugate gradient method (CGM) for optimization procedure and the incremental differential quadrature method (IDQM) for solving the governing equations are adopted. The results show that the Knudsen diffusion, surface diffusion, slip and viscous flows effects depend on the type of adsorbate and adsorbent gases. It is shown that the effective diffusivity is not constant and goes through a minimum at an intermediate pressure. Also, it is found that the Knudsen diffusion and the viscous flow are the dominant parts of the mass transfer process at low and high pressure, respectively, and despite the viscous flow, the Knudsen diffusion is highly sensitive to temperature change.

25. Preparation and Characterization of Activated Carbon–Zeolite Composite for Gas Adsorption Separation of CO2/N2 System

Masoume Rostami, Masoud Mofarahi, Ramin Karimzadeh, Davoud Abedi

J. Chem. Eng. Data, 2016, 61 (7), pp 2638–2646

DOI: 10.1021/acs.jced.6b00374




 In the present work, an alternative type of composite adsorbent has been prepared by adding a small amount of about 7 wt % of activated carbon into the zeolite 13X structure. Besides, zeolite 13X is synthesized as a pure adsorbent for operational comparison. The synthesized zeolite 13X, as well as the composite form, is produced by a hydrothermal method. Moreover, both of them are characterized using a variety of conventional analyzing procedures including X-ray diffraction, X-ray fluorescence, Brunauer–Emmett–Teller, and scanning electron microscopy analyses. Both adsorbents are tested in CO2/N2 separation via a standard adsorption process. Pure adsorption data of CO2 and N2 were determined experimentally at three temperatures of (283, 303, and 323) K and pressures up to 1600 mbar in a static volumetric method on both adsorbents. The results of comparing the activated carbon-zeolite composite with the crystalline structure of zeolite 13X revealed upgrades in some properties. Furthermore, the binary adsorption data of the system have been also measured on both adsorbents and evaluated by ideal adsorbed solution theory. Finally, the job is completed by the presentation of binary equilibrium diagrams as well as the experimental selectivities.


24. An indirect method to evaluate the performance of the activated carbon filters in the amine sweetening process

Masoud Mofarahi, Morteza Afkhamipour Emad Benhelal

Separation Science and Technology,2016 , 51 (10), pp 1627–1635

DOI: 10.1080/01496395.2016.1176045




In order to maintain the quality of amine circulation in the gas sweetening process, activated carbon filters are used to remove hydrocarbons, degradation products, and antifoam from amine circulation. In this study, a new indirect gas chromatography analysis is proposed to evaluate saturation point of the activated carbon filters. In this method, the measured compositions of gas-phase hydrocarbons in equilibrium with amine solution samples (from the inlet and the outlet of the filter) were applied to estimate hydrocarbon compositions in amine solution by a thermodynamic model. The proposed method described in this study is believed to be a simple and viable approach to evaluate the performance of the activated carbon filters in the amine scrubbing plants.

Kewords: Activated carbon filter,Gas sweetening,Gas Chromatography,Amine scrubbing


23. Modeling and optimization of CO2capture using4-diethylamino-2-butanol (DEAB) solution

Afkhamipour, M.; Mofarahi, M.

International Journal of Greenhouse Gas Control  vol. 49 February, 2016. p. 24-33



ISSN: 1750-5836





A multi-layer perceptron neural network (MLPNN) model with Levenberg–Marquardt learning algo-rithm were applied to model CO2 capture by a novel amine solution called 4-diethylamino-2-butanol(DEAB). The MLPNN model predicted the CO2 concentration and temperature profiles along the heightof the packed column as the model output. Inlet feed conditions of the absorber column (flue gas andamine) were selected as the inputs of the MLPNN model. Experimental data about random and structured packed columns were extracted from the literature and used to train the MLPNN model. In addition, asystematic procedure, i.e. Taguchi method, was applied to obtain the significant sequence of process parameters affecting CO2 removal efficiency and to optimize the variables in the absorber column. Five levels of five variables, including lean amine temperature, amine concentration, CO2 loading of amine,gas temperature, and amine flow rate, were used for the optimization of the absorber column. The average absolute relative deviations (AARD) between the predicted results and the experimental data suggested that our MLPNN model could predict CO2 concentration and temperature profiles along the packed column (AARD% = 5.47 and 3.61, respectively). The signal to noise ratio analysis of the Taguchi method yielded a significant sequence of factors affecting CO2 removal efficiency in the packed column(CO2 loading > amine flow rate > amine concentration > gas temperature > amine temperature). This study demonstrated the acceptable accuracy of the MLPNN and Taguchi method in, respectively, the model ingand optimization of CO2 capture in amine solutions.

Keywords: Packed column, MLPNN model,Taguchi method,DEAB,CO2 removal, efficiency


22.Adsorption equilibrium of methane and carbon dioxide on zeolite13X: Experimental and thermodynamic modeling

Fatemeh Gholipour, Masoud Mofarahi       

The Journal of Supercritical Fluids 2016, 111, Pages 47–54



A static, volumetric method has been used to determine the adsorption equilibrium of CH4and CO2andtheir binary mixtures on 13X molecular sieves at various temperatures between 273 and 343 K. Pressures for the pure component data extend up to 10 bar, while all binary data were obtained at 4 bar and 6 bar. Themeasured pure isotherms were regressed using different isotherm equations and the regressed parameters were applied to different thermodynamic models such as ideal adsorbed solution theory (IAST),vacancy solution theory (VST) and real adsorbed solution theory (RAST). CH4/CO2system that deviate from ideality is not well represented by IAST and VST, whereas RAST which include activity coefficient in the adsorbed phase as characterizing parameter for non-ideality, show a much better representation of the binary equilibria. Experimental selectivities CO2/CH4range from 26 to 2 at different pressure and temperatures. It is concluded that zeolite 13X suitable for natural gas industrial separation with yCO2< 0.2at 303 K and 4 bar. For landfill gas upgrading, where yCO2< 0.45, zeolite 13X can be successfully applied at 303 K, 4 bar and 303 K, 6 bar and 323 K, 4 bar.


21.Application of Inverse Method to Estimation of Gas Adsorption Isotherms

H. Rahideh · M. Mofarahi1 · P. Malekzadeh ·M. R. Golbahar Haghighi

Transport in Porous Media, 2015, 110 (3), pp 613-626

DOI: 10.1007/s11242-015-0576-8






Abstract As a first step to analyze the inverse kinetic of adsorption, an inverse algorithm is developed to estimate equilibrium adsorption isotherm in a gas storage vessel by using the dynamic transient internal pressure. In the present study, no prior information is need for the functional form of the unknown isotherm equation to solve continuity equation. The conjugate gradient method is employed for optimization procedure. The incremental differential quadrature method as a computationally efficient and accurate numerical tool is applied to solve the corresponding direct, sensitivity and adjoint problems. The accuracy of the presented approach is examined by simulating the exact data of known model. Good accuracy of the obtained results validates the presented approach.


20. Experimental Investigation and Thermodynamic Modeling of CH4/N2 Adsorption on Zeolite 13X

 Masoud Mofarahi and Ali Bakhtyari

 J. Chem. Eng. Data, 2015, 60 (3), pp 683–696

 DOI: 10.1021/je5008235







 To implement an experimental study of CH4/N2 adsorption on Zeochem Co. zeolite 13X, a volumetric apparatus was utilized. In this regard, pure adsorption isotherms were measured at different temperatures [(273, 283, 303, 323, and 343) K] and pressures up to 10 bar, while binary data were collected at (303 and 323) K and different pressures and bulk gas phase molar fractions. Integral and differential thermodynamic consistency tests (TCT) were performed to validate the collected data and certify accuracy of the measurements. To have a thermodynamic view over the investigated system, thermodynamic functions such as enthalpy, entropy, surface potential, and Gibbs free energy were estimated numerically. Besides, the measured pure isotherms were regressed using different isotherm equations and the regressed parameters were applied to different models based on the thermodynamic theory of solutions, i.e., ideal adsorbed solution theory (IAST), vacancy solution models (VSM), and Peng–Robinson two-dimensional equation of state (PR 2D-EOS). All the models were applied in the predictive scheme. Experimental and predicted adsorption data were compared through the appropriate phase diagrams. Almost all the models could predict binary adsorption behavior of CH4 and N2 over zeolite 13X.


19. Numerical Modeling of Fluid Flow and Thermal Behavior of Different Nanofluids on a Rotating Disk

 Masoud Mofarahi, Mohammad Amin Makarem, Peyman Jowkar, Benyamin Jafarian

 Heat Transfer—Asian Research

 DOI: 10.1002/htj.21166                                                                                                                                                                                                                                                         







The thermal and velocity profiles of various nanofluid systems on a rotating disk are simulated. Finite difference method, the orthogonal collocation method, and the differential quadrature method (DQM) of numerical approaches are used to solve the governing equations and are compared to determine the faster and more accurate solution procedure. Five nanoparticles Al, Al2O3, Cu, CuO, and TiO2 solved in three base fluids water, ethylene glycol, and engine oil are considered to be used on the disk at different volume fractions. A new general algorithm is presented for solving equations of a rotating-disk problem quickly and accurately and it is found that the DQM method is the best approach for this numerical simulation. Heat transfer performance of a rotating disk would be much better enhanced with water based Al nanofluid. A wide range of results for different base–fluid combinations with nanoparticles is presented with untransformed 3D results and effects of the variation of different parameters provides comprehensive insight and prevents inaccurate deductions.


18. Gas Adsorption Separation of CO2/CH4 System Using Zeolite 5A


Masoud Mofarahi ; Fatemeh Gholipour                                           

Microporous and Mesoporous Materials   2014,200, Pages 1–10 

DOI: 10.1016/j.micromeso.2014.08.022








Pure gas adsorption isotherms of carbon dioxide at (273, 283, 303, 323, 343) K and binary adsorption isotherms of carbon dioxide and methane at (303,323) K and pressures up to 10 bar on Zeochem Co. Zeolite 5A were measured using a volumetric method. Equilibrium gas phase compositions have been determined using a gas chromatograph (GC). The experimental binary equilibrium data were compared with equilibrium data calculated by ideal adsorbed solution theory (IAST), and vacancy solution model (VSM). A model analysis of the experimental data has been performed with real adsorbed solution theory (RAST) owing to not satisfactory prediction of multi-component behavior with IAST and VSM. For this purpose, activity coefficients, accounting forthe non-ideality of the adsorbed mixture, were calculated from the experimental data. The results of the pure experimental data showed that, the heat of adsorption for methane is approximately independent of loading (about 20kJ/mol), and for carbon dioxidedecreases by increasing loading when q<0.5 mol/kg. Subsequently, by increasing loading, the heat of adsorption increases upto q=2 mol/kg. The selectivity of both simulated landfill and biogas mixtures have been also measured experimentally. These data indicated that; zeolite 5A can be successfully applied in CO2/CH4 separation for landfill gas and biogas upgrading.


 17. Sensitivity analysis of the rate-based CO2 absorber model using amine solutions (MEA, MDEA and AMP) in packed columns

Afkhamipour, M.; Mofarahi, M.

International Journal of Greenhouse Gas Control  vol. 25 March, 2014. p. 9-22

DOI: 10.1016/j.ijggc.2014.03.005 ISSN: 1750-5836.







The modeling and simulation of CO2 capture processes with amine solutions are considered as important developments toward the detailed study and analysis of these processes. In the literature, the application of rate-based models for the modeling of CO2 capture processes by amine solutions has been proved superior to equilibrium-stage models. The results of rate-based models, however, depend strongly on the selection of model parameters such as physical properties, transport properties, kinetic models, and mass transfer correlations. In this study, sensitivity analysis was performed to investigate the effect of mass transfer correlations in combination with kinetic models on the performance of an absorber column. The reason for this investigation is to establish appropriate correlations that can be used for design of the CO2 capture process. Sensitivity analysis was performed using a rate-based model for capture of CO2 in monoethanolamine (MEA), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP) solutions in packed columns containing structured and random packing. The model was successfully validated by comparison of obtained results with published experimental data. The sensitivity analysis revealed that the mass transfer correlations developed by Hanley and Chen (2012) to simulate a structured packing absorption column, obtained the best results in comparison with the other tested and analyzed correlations in this study. For a randomly packed column, the correlations suggested by Onda et al. (1968) exhibited the best results. The kinetic models tested and examined in this study had a determinant role in the results of the sensitivity analysis in a manner that reflected the assumptions used in development of the model such as the temperature and amine concentration ranges. Therefore, careful selection of the mass transfer correlations and kinetic models to be used in the rate-based absorber model is required for modeling of the CO2 capture process. Otherwise, serious errors in design of the CO2 capture process may result.

Keywords: CO2 capture; Packed column; Rate-based model; Sensivity analysis; Kinetic models; Mass transfer correlations


16. Pure and Binary Adsorption Equilibria of Methane and Nitrogen on Zeolite 5A

Ali Bakhtyari and Masoud Mofarahi

Journal of Chemical & Engineering Data vol. 59 issue 3 February 13, 2014 p. 626–639

DOI: 10.1021/je4005036. ISSN: 0021-9568.



Adsorption isotherms of pure methane and nitrogen and their binary mixtures on Zeochem Co. zeolite 5A were measured using a static volumetric apparatus. Pure isotherms were measured at (273, 283, 303, 323, and 343) K and pressures up to 10 bar, while binary data were measured at (303 and 323) K and different pressures and bulk gas phase compositions. Experimentally measured data were validated using the integral thermodynamic consistency test. In contrast to the aforementioned binary measurements, predictions of different thermodynamic models utilizing pure adsorption isotherms were used to describe binary adsorption behavior of methane and nitrogen over zeolite 5A. Models based on the thermodynamic theory of solutions such as ideal adsorbed solution theory, vacancy solution models, and two-dimensional equations of state were used for this purpose. Experimental and predicted equilibrium data were compared through the appropriate phase diagrams. Predicted selectivity curves were compared against experimental data. All the proposed models are capable to describe adsorption equilibria of the investigated system. Results of the present study show that methane and nitrogen form an ideal and energetically homogeneous adsorptive system on Zeochem Co. zeolite 5A.



 Masoud Mofarahi;Ehsan Javadi Shokroo

 Petroleum & Coal   Vol. 55(3), 2013. p. 216-225







The performances of two types of zeolite 5A and zeolite 13X in oxygen separation from air with a two-bed six-step pressure swing adsorption (PSA) system were investigated using mathematical modeling. The effects of feed flow rate, adsorption step pressure, adsorption step time and purge to feed ratio on oxygen purity and recovery are studied. Comparison of two types of zeolites shows that the PSA process performance (in terms of purity and recovery) was better with zeolite 13X than the zeolite 5A. Furthermore, Results of simulation indicated a very good agreement with some current literature experimentally work.



14. Oxidized single-walled carbon nanotubes (SWCNs-COOH) as a new catalyst for the protection of carbonyl groups as hydrazones 

Maryam Kiani Borazjania, Hamid Reza Safaeib, Majid Panahandehb, Ali Reza Kiania

Masoumeh Kianic, Masoud Mofarahi

S. Afr. J. Chem. vol. 66, 2013. p. 279-281

DOI: .... ISSN: 0379-4350












Nano-materials are considered as suitable heterogeneous catalysts for many organic reactions. Herein oxidized carbon nanotube (SWCNTs-COOH) has been reported as a heterogeneous catalyst, for protection of carbonyl groups as hydrazones in EtOH at 80 °C. The reactions proceed smoothly with good to excellent yields, and the SWCNTs-COOH used can be recycled.

Keywords: Carbon nanotubes, protection, catalyst, carbonyl group



13. Pure and binary adsorption isotherms of ethylene and ethane on zeolite 5A 

Mofarahi, Masoud; Salehi, Seyyed Milad.

Adsorption vol. 19 issue 1 February 2013. p. 101 - 110

DOI: 10.1007/s10450-012-9423-1. ISSN: 0929-5607.





Pure and binary adsorption equilibrium data of ethylene and ethane on zeolite 5A were collected with a volumetric method for the temperature range 283 K to 323 K and pressure up to 950 kPa. The applicability of the binary adsorption prediction by the vacancy solution theory (VST) was investigated. Further individual adsorption and selectivity were obtained by VST prediction. According to the experimental results, zeolite 5A has a high adsorption capacity and selectivity for ethylene in the ethylene/ethane system. VST predicts that ethylene selectivity increases with pressure; it also shows that the amount of ethylene separated by zeolite 5A increases as the temperature decreases at a specified pressure.

Keywords: Adsorption; Zeolite 5A; Ethylene/ethane separation system; Vacancy solution theory



12. Comparison of rate-based and equilibrium-stage models of a packed column for post-combustion CO2 capture using 2-amino-2-methyl-1-propanol (AMP) solution.

Afkhamipour, M.; Mofarahi, M.

International Journal of Greenhouse Gas Control  vol. 15 July, 2013. p. 186-199

DOI: 10.1016/j.ijggc.2013.02.022. ISSN: 1750-5836.







In this study, two mathematical models including rate-based and equilibrium-stage were applied and compared for CO2 absorption by 2-amino-2-methyl-1-propanol (AMP) solution in a packed column. In the rate-based model, process of simultaneous mass and energy transfer across the interface was modeled by means of rate equation and mass transfer coefficients. The rate-based model was based on the two-film theory. In contrast, the equilibrium-stage model was based on the theory of theoretical number stages combined with the concept of Murphree efficiency. In this model, different values of Murphree efficiencies were used along the absorption column. The two modeling approaches were validated by comparison of obtained results with published experimental data. The simulation of the absorber column shows the rate-based model gives a better prediction of the temperature and concentration profiles compared to the equilibrium-stage model. As a result, for a detailed process design the rate-based model should be applied. Also, comparison of the absorption performance between the CO2-MEA and CO2-AMP system in a bench-scale absorber packed with high efficiency packing was performed. Finally, The effect of important process parameters such as CO2 partial pressure, CO2 loading of amine solution, flow rate of amine solution, concentration of amine solution and solution temperature on the CO2 removal efficiency were analyzed. The results of this analysis showed that CO2 removal efficiency increases with the increase of solution flow rate, solution concentration and solution temperature (in the CO2 loading of more than 0.15) and decreases with the increase of the CO2 loading of AMP solution (in the CO2 loading of more than 0.15) and CO2 partial pressure.

Keywords: CO2 capture; AMP solution; Packed column; Rate-based model; Equilibrium-stage model; Murphree efficiency


 11. Reduction of CO2 capture plant energy requirement by selecting a suitable solvent and analyzing the operatingparameters.

Salkuyeh, Yaser Khojasteh; Mofarahi, Masoud.

International Journal of Energy Research vol. 37 issue 8 25 June 2013. p. 973-981

DOI: 10.1002/er.2899. ISSN: 0363-907X.







Among various developed methods for CO2 capturing from industrial flue gases, chemical absorption system is still considered as the most efficient technique, because of its lower energy requirement and also its applicability for low concentration of CO2 in the inlet gas stream. Also, it can be used to retrofit the existed power plants, which are the major industrial CO2 emission sources, without changing their design condition. Selection of a suitable solvent is the first parameter that should be considered in the design of capture plants that use absorption technology. The most important challenge for using chemical solvents is finding the optimum operating conditions to minimize the energy requirement. Study of technical parameters can be helpful to improve the overall capture plant efficiency. In this paper, CO2 capture plant has been simulated for different solvents to compare their performance and energy requirement. To improve the plant overall efficiency, effect of the main operating factors such as amine flow rate, temperature, inlet gas temperature, and pressure has been studied in this paper. This analysis indicates the best chemical solvent for various cases of inlet flue gas. This parametric study reduces the overall energy requirement and helps design a cost-effective plant. Copyright © 2012 John Wiley & Sons, Ltd.

Keywords: CO2 capture; chemical solvent; power plant; energy; absorption




10. Comparison of MEA and DGA performance for CO2 capture under different operational conditions.

Salkuyeh, Yaser Khojasteh; Mofarahi, Masoud.

International Journal of Energy Research vol. 36 issue 2 February 2012. p. 259-268

DOI: 10.1002/er.1812. ISSN: 0363-907X.







Carbon capture and storage from flue gases is the most common method to reduce greenhouse gas emissions. Using a primary amine as the solvent of CO2 capture unit is popular because of its high activity and ability to be used for streams with low concentration and low partial pressure of CO2. Monoethanolamine(MEA) and Diglycolamine(DGA) are the most common kinds of primary amines which have been traditionally used in many natural gas sweetening plants. In this research, the capture plant has been designed for these two solvents at various CO2 concentrations in the feed flue gas. This paper proposes different possible alters to overcome the high energy requirements of capture plant. It also presents the results of technical evaluation of different parameters, in order to design an actual plant with minimum energy requirement. The results of different parameters show that for DGA solvent, there will be an improvement in overall energy usage in the capture plant rather than MEA for some special cases. To gain the practical results, actual stages have been used for absorber and stripper instead of equilibrium stages. Copyright © 2011 John Wiley & Sons, Ltd.

Keywords:CO2 capture; parametric design; MEA; DGA; avoided CO2:


9. New mixing rule for predicting multi-component gas adsorption.   

Mofarahi, M.; Hashemifard, S. A.

Adsorption vol. 17 issue 2 April 2011. p. 311 - 323

DOI: 10.1007/s10450-010-9288-0. ISSN: 0929-5607.


The present work describes a predictive model for ascertaining the multi-component gas adsorption equilibria. The model utilizes special form of covolume-dependent (CVD) mixing which is combined with the generalized form of 2-D EOS. Four well known 2-D EOSs; van der Waals, Soave-Redlich-Kwong, Peng-Robinson, Eyring along with the modified CVD mixing rule were used to predict the total adsorption of several binary and ternary systems. Based on the concept of the CVD mixing rule, it was inspired that CVD mixing rule could be a binding bridge between the molecular size and the molecular interaction. To show this, the ratio of the classical mixing rule %AAD to the CVD mixing rule %AAD were plotted versus the difference of the collision or the Leonard-Jones diameters of the gas molecules in the mixtures. It shows that there is a criterion between the CVD and the classical mixing rules in terms of molecular size difference. It seems that, Δσ LJ≈0.60 Å is the criterion. The CVD mixing rule is approximately predominant in the region of Δσ LJ≥0.60 Å, whilst, region of Δσ LJ≤0.60 Å is nearly governed by the classical mixing rule. All predictions by the new mixing rule and the classical mixing rule were compared with the experimental data from the case studies. The new form of the mixing rule is in good agreement with the experimental data even for the non-ideal systems; hence provides a powerful framework to predict multi-component gas adsorption.

Keywords: CVD mixing rule; Gas adsorption; Multi-components; Prediction


8. Pure and Binary Adsorption Isotherms of Nitrogen and Oxygen on Zeolite 5A.

Mofarahi, Masoud; Seyyedi, Majid.

Journal of Chemical & Engineering Data vol. 54 issue 3 March 12, 2009. p. 916-921

DOI: 10.1021/je8006919. ISSN: 0021-9568.







Adsorption isotherms were measured for pure nitrogen, oxygen, and their binary mixtures (20 %, 40 %, and 60 % nitrogen in the mixture) on a commercial zeolite 5A. The measurements were conduced using a volumetric method at temperatures of (273, 283, 303, and 343) K and at pressures to 950 kPa. The 2D equations of state of van der Waals, Soave−Redlich−Kwong, Peng−Robinson, and Eyring have been applied to represent total adsorption for the pure and binary systems. The amount of adsorption of each component has been obtained in the mixture as well as the selectivity by thermodynamic prediction. Experimental results indicate a very good agreement with thermodynamic modeling and with some current results in the literature.


7. Oxygen Separation from Air by Four-Bed Pressure Swing Adsorption.

Mofarahi, Masoud; Towfighi, Jafar; Fathi, Leila.

Industrial & Engineering Chemistry Research vol. 48 issue 11 June 3, 2009. p. 5439-5444

DOI: 10.1021/ie801805k. ISSN: 0888-5885.







A study on a four-bed seven-step pressure swing adsorption (PSA) using zeolite 5A was performed experimentally and theoretically for separation of oxygen from air. In this process the steps of feed pressurization, production, blowdown, purge, pressure equalization (two steps), and product pressurization are included in a cycle. The effects of various operating parameters such as adsorption pressure, cycle time, production rate, and purge rate on the product purity and recovery were investigated experimentally. Oxygen purity and recovery both increase when adsorption pressure increases. For most of the experiments at the highest purge rate, a higher purity of oxygen is obtained, but the recovery of oxygen is reduced. Oxygen recovery increases as production rate increases while the purge flow rate remains constant. It was observed that increasing the cycle time increases the performance of the process. An equilibrium based isothermal model in conjunction with an LDF (linear driving force) approximation was employed to simulate process performance. Comparison of the results obtained from the experiments and simulation results shows reasonable agreement.


6. Design of CO2 absorption plant for recovery of CO2 from flue gases of gas turbine

Masoud Mofarahi, Yaser Khojasteh, Hiwa Khaled, Arsalan Farahnak

Energy  vol. 33 issue 8 June 3, Auguest, 2008. p.1311–1319

DOI: 10.1016/j.ijggc.2013.02.022. ISSN: 1750-5836.


The ongoing human-induced emission of carbon dioxide (CO2) threatens to change the earth's climate. A major factor in global warming is CO2 emission from thermal power plants, which burn fossil fuels. One possible way of decreasing CO2 emissions is to apply CO2 removal, which involves recovering of CO2 from energy conversion processes. This study is focused on recovery of CO2 from gas turbine exhaust of Sarkhun gas refinery power station. The purpose of this study is to recover the CO2 with minimum energy requirement. Many of CO2 recovery processes from flue gases have been studied. Among all CO2 recovery processes which were studied, absorption process was selected as the optimum one, due to low CO2 concentration in flue gas. The design parameters considered in this regard, are: selection of suitable solvent, solvent concentration, solvent circulation rate, reboiler and condenser duty and number of stages in absorber and stripper columns. In the design of this unit, amine solvent such as, diethanolamine (DEA), diglycolamine (DGA), methyldiethanolamine (MDEA), and monoethanolamine (MEA) were considered and the effect of main parameters on the absorption and stripping columns is presented. Some results with simultaneous changing of the design variables have been obtained. The results show that DGA is the best solvent with minimum energy requirement for recovery of CO2 from flue gases at atmospheric pressure.

Keywords: Carbon dioxide recovery; Chemical absorption; Amines; Gas turbine; Flue gases


5. Four-Bed Vacuum Pressure Swing Adsorption Process for Propylene/Propane Separation

Masoud Mofarahi, Mojtaba Sadrameli,Jafar Towfighi

Industrial & Engineering Chemistry Research vol. 44 issue 5 January 20, 2005. p. 1557–1564

DOI: 10.1021/ie034016k. ISSN: 0888-5885.







A vacuum pressure swing adsorption (VPSA) using zeolite 5A was studied experimentally and theoretically. An equimolar mixture of propylene/propane was used as a feed gas for an eight-step, four-bed VPSA process. Isotherm data of zeolite 5A at various temperatures and breakthrough curves of propylene and propane for both adsorption and regeneration steps were obtained to acquire the input parameters for the test runs with the pilot plant. Experimental measurements by the pilot plant have been obtained between a maximum pressure of PH = 5.8−6.4 bar and a minimum pressure of PL = 0.1−0.05 bar at a constant temperature of 70 °C. The effects of feed rate and dilution with H2, purge rate, and vacuum pressure on the product purity and recovery were also investigated via experimentation. Using a feed rate of 320 NL/h of a mixture of 50% propylene/propane at 70 °C, a purity of 92% propylene and a recovery of 29% were obtained. Comparison of the results from the experiments and the simulation gave a reasonable agreement.


4.Characterization of Activated Carbon by Propane and Propylene Adsorption

Masoud Mofarahi, Mojtaba Sadrameli, and Jafar Towfighi

Journal of Chemical & Engineering Data vol. 48 issue 3 July 17, 2003. pp 1256–1261

 DOI: 10.1021/je0340553  ISSN: 0021-9568.



Two types of commercial activated carbons, Westvaco BAX 1100 and Chemviron LAC 30-57, were characterized by microporosity, equilibrium, and kinetic adsorption of propane and propylene. The porosity was determined by the measurement of the N2 adsorption isotherm at 77 K. Single component equilibrium adsorption of propane and propylene on the adsorbents was measured in the temperature range (273 to 343) K and the pressure range (0.0001 to 1) bar and correlated by several well-known isotherm models. The enthalpies of adsorption were estimated by the Clausius−Clapeyron equation and its dependence on adsorption coverage. Fractional uptake experiments performed to study the single component kinetics and apparent diffusivity were evaluated.



3. Oxygen Separation from Air Using Pressure Swing Adsorption

Fathi L.; Towfighi, J.:  Mofarahi, M.

J. Sep. Sci. Eng. , 2009, 1,1




2. Study of a Four-Bed Pressure Swing Adsorption for Oxygen Separation from Air

 Mofarahi, M.; Moghadaszadeh Z.; Towfighi J.

Int. J. Chem. Bio. Eng.,2008,3;140





1. SHAHAB-PC Based Simulatorfor Prediction of Furnace Run Length the Pyrolysis of Hydrocarbons

(Ethane to Naphtha)

Towfighi J., Karimzadeh R., Sadrameli M.,  Mofarahi, M., Niaei A.,

Saedi G., Hosseini S., Mokhtarani B.

Iranian  J. of Chemical Engineering, 2004, 1, 55