Department of Process Engineering (1986 - Present)
chemical engineering
, Polytechnic Bucharest, Romania
Using promoters in different types of catalysts can positively affect the yield of oxidative dehydrogenation process and the selectivity of propylene as the main product Titania nanotubes containing distinct promoters including silver, nitrogen and cerium have been synthesized with high specific area by the hydrothermal technique and used as a support in oxidative dehydrogenation of propane. The incipient wetness impregnation method was applied for catalysts preparation Mo/Ce-TNT, Mo/Ag-TNT and Mo/N-TNT were characterized by various techniques such as XRD, TEM, SEM, EDS, BET, H2-TPR. The presence of these promoters lead to enhancement of propylene yield among which the Mo/Ce-TNT catalyst was of great efficiency. From the results, it is considered to be quite evident that the oxygen capacity of the catalyst containing Ce can contribute to the oxidation state and redox reactions. In comparison to Mo …
Porous single-layer graphene is believed to be an ultimate molecular sieving membrane. One of the bottlenecks in scaling up graphene membranes is the transfer process in which capillary forces as well as the mechanical tensions imposed on the graphene film generate unwanted cracks and tears. Herein, we report a single-step fishing-free transfer technique for the fabrication of a helium-sieving graphene membrane using a spin-coating-assisted approach in which no capillary forces and mechanical tensions are exerted on the graphene film. The porous polysulfone (PS), which is synthesized in this method, is applied as both the graphene protective layer and the porous reinforcing support; thus, eliminating the fishing stage in which the graphene film is scooped onto a supporting substrate. The proposed technique yields a crack-free and large-area (∼1 cm2) graphene film on the porous polymer substrate. This …
A highly mesoporous ZSM-48 zeolite has been prepared using low-cost anionic surfactant sodium dodecylsulphate (SDS) as mesopore-generating agent and short-chain 3-aminopropyltrimethoxysilane (APTMS) as co-structure directing agent. The mesoporosity formation took place through the interaction between the silica species/APTMS and SDS molecules existing in the gel composition. In the synthesis solution with a pH slightly less than ten, the methoxysilyl moiety in APTMS was hydrolysed to the –SiO3 units and became incorporated inside the zeolite crystals while the positively charged ammonium site of APTMS interacted with the negatively charged head group of the SDS. Aggregation of aluminosilicate/APTMS species around the SDS micelles during the crystallization process, led to the formation of a mesoporous zeolite. In this study, a conventional ZSM-48 and seven ZSM-48 zeolites from different …
This paper studies an efficient way to produce syngas from the methane couple reforming and partial methane oxidation by utilizing a catalytic plate reactor. Methane steam and dry reforming as endothermic reactions are coupled with partial methane oxidation as an exothermic reaction in a catalytic plate reactor, which is simulated using detailed reaction kinetics, mass, and energy balances. The impact of inlet temperature, composition, and velocities on the reforming and partial oxidation channels, and also the resulting methane conversions, is studied. In addition, the H 2/CO ratio is evaluated for both endothermic and exothermic sides across varied feed ratios. Co-and counter-flow arrangements are simulated for catalytic plate reactors, and their impact on temperature distribution and methane conversion is studied. The suitable plate dimensions, in particular, plate length, are computed during this simulation. Applying a metal plate, Co-and counter-flow arrangements are simulated for catalytic plate reactors, and their impact on temperature distribution and methane conversion is studied. During this simulation, the appropriate plate dimensions, particularly plate length, are determined. The use of a metal plate with a greater thermal conductivity allows for effective heat transmission between endothermic and exothermic channels, resulting in outstanding temperature distribution and slight temperature differences.
Selective removal of ethyl mercaptan from natural gas is presently challenge in the gas industry. Nanoporous zeolite frameworks with different topologies have been known as the most appropriate compounds for the adsorption of ethyl mercaptan. Grand Canonical Monte Carlo (GCMC) simulation has been employed to predict the adsorption and separation properties of mixtures containing ethyl mercaptan under difficult experimental conditions. The adsorption isotherms of ethyl mercaptan in pure form and mixtures with methane on purely siliceous zeolites including BEA, FAU, LTL, MFI, and MOR have been obtained at the temperature of 298 K over the pressure range of 0–100 kPa. The results show that the adsorption capacity is a function of the pore diameter of zeolites. FAU has appeared as an adsorbent with high adsorption capacity. In contrast, it has shown considerably lower adsorption affinity for methane …
The aim of this paper is to modify the X zeolite adsorbent to enhance nitrogen adsorption capacity. To this end, a novel procedure for modification of X zeolite, including both NH4+ treatment and Ca2+ ion-exchange, is introduced which results in a hierarchical mesopore-micropore structure with multilayer N2 adsorption behavior. The presented adsorbents, “hierarchical X zeolite” (HX) and “Ca2+ exchanged hierarchical X zeolite” (CaHX), are compared with the available microporous 13X zeolites, modified by Na+ (NaX), and mixed Ca2+ /Na+ cations (CaNaX). The properties of these adsorbents are characterized by N2 adsorption-desorption in 77K, XRD, and XRF analysis. The high-pressure N2 adsorption isotherms are measured at 283, 298, and 31
Catalytic reforming is a process known in the refining industry to improve the quality of gasoline by increasing the octane number, the production of aromas, and hydrogen production as a byproduct. The purpose of this research is to develop a kinetic model for naphtha catalytic reforming reactions with consideration of simple and reliable assumptions and also to provide a mathematical model using mass balance. In the kinetic model, 22 lamps and 48 reactions are present. Also, in the mathematical model, the superficial velocity of the fluid is considered variable in the axial direction of the reactor. In order to evaluate the proposed model, laboratory tests have been used in 24 different operating conditions, which according to the results of the analysis of the products, the yield of liquid is observed in the range of 0.701 to 0.952. Also, using experimental results, the model parameters are obtained through optimization with MATLAB software. Finally, the results of comparing the predicted product distribution through the model with their experimental values showed that the proposed model with acceptable accuracy could predict the distribution of the products.
The aim of this study was to develop fast and facile methods for the determination and classification of zeolite samples based on Si/Al ratio by fourier transform infrared spectroscopy (FTIR). The ZSM-5, ZSM-48 and mordenite catalysts spectral data were used for estimation of Si/Al ratio using two approaches according to PLS-R and SVM-R algorithms in whole (600–4000 cm−1) and fingerprint (3000–3800 cm−1) spectral regions. The drift-FTIR spectral data were also analyzed by classification method using the soft independent modelling of class analogies (SIMCA) for mordenite, ZSM-5 and ZSM-48 catalysts classification. Performance of the regression models was adequate with good statistical results. The correlation coefficients (R2) were about 0.99 and 0.96 for SVM and PLS regression models. The results obtained for the SVM model of the MIR spectra was very good and encouraging, since the RMSEP was …
Hierarchically porous zeolites with different porosity levels have attracted much attention because of their well-defined pore system, improved mass transfer and, higher catalytic performance. In the present work, mesoporosity was introduced into silicoaluminophosphate (SAPO) zeolite by the hydrothermal method using tetraethylammonium hydroxide and morpholine as structural directing agents and polyethylene glycol (PEG) as a cost-effective mesopore soft template with a wide range of molecular weights (MWs) and molar ratios. The selected catalysts were characterized by techniques of XRD, BET, FESEM, and NH3-TPD and, the catalytic performance of all hierarchical porous SAPO-34 samples in the methanol to olefins (MTO) reaction was evaluated in a fixed bed reactor at 425 °C and methanol weight hourly space velocity (WHSV) of 2.3 h−1 using a 20% methanol in water as a feed stream …
The aim of this work is sorptive removal of cesium and strontium ions from aqueous solution using natural zeolite and management of produced secondary waste. Characterization of the natural zeolite was performed by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), and field emission scanning electron microscopy (FE-SEM). The effective parameters on the sorption process such as initial solution pH, adsorbent dosage, and concentration of cesium and strontium ions were optimized by using experimental design method. Based on the results, removal efficiency for cesium ion was about 67.8% at the optimum condition of adsorbent dosage of 0.40 g, pH= 7.23 and Cs+ concentration of 10 mg L− 1, and for the strontium
A method based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was employed to quantify the mesopore volume of the ZSM-48 zeolites. Partial least squares (PLS) and support vector machine (SVM) multivariate calibration methods were used to construct linear and non-linear regression models, respectively. N2 physisorption analysis using BET model was used as a reference method to determine the mesopore volume of zeolites. In mid-IR region, three different ranges, 3700–3800, 3200-3800 and 400-4000 cm-1 were investigated in order to selection the optimum spectral range for evaluation of the mesopore volume of the zeolites. The effect of orthogonal signal correction (OSC) as a preprocessing method on the quality of linea
Vanadium oxide supported on TiO2(P25) catalysts were synthesized via atomic layer deposition (ALD) of vanadyl acetylacetonate (VO(acac)2). Comprehensive investigations were performed to evaluate the ALD temperature window and the saturation deposition period of VO(acac)2, which were found to be 140–210??C and 120?min, respectively. The synthesized catalysts were compared to their corresponding impregnation ones for the oxidative dehydrogenation of propane reaction (ODH-P). The ODH-P results indicated the superior performance of the ALD catalysts for the low temperature ODH-P (< 350??C) given its better dispersion of vanadium oxide(vanadia) in the ALD catalysts. Several characterization techniques including HR-TEM, FE-SEM, XRD, BET, XPS
Separation of carbon dioxide in flue gases from the combustion equipment is one of the most serious concerns for industries and especially for the power plants which are the main producers of this pollutant gas. From the various separation methods, vacuum pressure swing adsorption (VPSA) process is attracted interest due to its lower energy consumption and high efficiency. A VPSA process was studied for the separation of a mixture of CO 2/N 2 (80% N 2 and 20% CO 2). Experiments were performed in an eight-step, four-bed setup using zeolite 13X and carbon molecular sieve (CMS) as adsorbents. Experimental measurements by the bench-scale system have been obtained in a pressure range of 2.7–4.7 bar, cycle times of 360–600 s, the product flow
Abstract Two types of zirconium-containing hierarchical SAPO-34 catalysts were successfully synthesized by isomorphous substitution and impregnation methods and applied for the conversion of methanol to light olefins. Carbon nanotube was employed as a mesopore template to create mesopores in the crystals of SAPO-34. Physical and chemical characterizations of the catalysts demonstrated that the modification of SAPO-34 with Zr by isomorphous substitution and impregnation methods gives rise to differences in acidity, porosity and crystal size. MTO results showed that the lifetime of the catalysts was in the order of ZrAPSO-34 > SAPO-34 > Zr/SAPO-34 while the selectivity to ethylene was in the order of Zr/SAPO-34 > ZrAPSO-34 > SAPO-34.
In regards to the unique properties of lithium, lithium separation with high purity is crucial in various industries. Due to the close radii of alkali and alkaline earth metals, this is important to choose a technique with appropriate properties for ion separation in aqueous medium. Among the available methods for lithium enrichment, polymer inclusion membrane (PIM) system has features that meet the needs. In this study, a PIM containing green polyol as the base polymer, 12-Crown-4 (12C4) as the carrier and 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid was synthesized to separate lithium ion from an aqueous solution of Li+, Na+, K+, Ca2+, and Mg2+. Also, the zeolitic imidazolate framework type ZIF-8 was employed in the membrane
SAPO-34 samples were prepared via a seeding-induced method with a considerable reduction of template concentration. The resultant SAPO-34 zeolites were investigated by XRD, FESEM, EDS, N2 adsorption, and NH3-TPD analyses. The samples represent different catalytic activity in the MTO process due to their differences in the physic-chemical properties, including crystallite/particle sizes, surface area, acid strength and concentration. Pure SAPO-34 was obtained with a 60% reduction of organic template for the first time. However, due to the increase of particle sizes, it did not show the desired catalytic performance. An excellent catalytic performance was achieved for the seeding-induced catalyst prepared by a 40% reduction of template conten
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,
SAPO-34 catalysts were synthesized through the seeding approach under different seed conditions. The different seed synthesis times (6 h, 12 h, and 24 h) and three types of seeds were evaluated: the dried seed, the calcined seed, and the mother liquor from an unseeded synthesis, called the solution seed. Pure SAPO-34 was obtained using 12 h and 24 h solution seeds, in which a 40% reduction of template consumption was achieved simultaneously. All seeding induced samples represented higher catalytic performance in the MTO process than conventional SAPO-34 due to the smaller crystallite/particle sizes and larger external surface areas and mesopore volume. Furthermore, the changes in the acidity of samples affect their performance. The maximum
The SAPO-34 catalysts were successfully synthesized with different amounts of a cheap and green nonionic surfactant (Triton X-100) as a mesoporogen additive and MOR/TEAOH as microporous mixed templates. The prepared samples were characterized and tested in the methanol to olefins (MTO) reaction under the industrial feed composition of 72 wt% methanol in water. The results revealed that the surfactant concentration affects the acidity, particle size, and textural properties which results in different catalytic performances. The sample prepared with the surfactant molar ratio of 0.02 exhibits a 12% improvement in the light olefins selectivity (90%) as well as the longer catalyst lifetime (more than 330 min) compared to the parent one (79
High-end applications require a very tall vertical extraction column in some cases which deteriorates protection against radiation and cannot be employed for indoor applications. On the other hand, horizontal extraction columns offer higher efficiency and pretension, but lower maximum throughput. In order to address this issue, the L-shaped pulsed extraction column is a new type of extractors which were recently introduced for such applications with area constraints. The objective of this study is to evaluate the effects of operating parameters and physical properties on the variation of holdup and slip velocity in this type of extractors for three liquid systems including toluene–water, butyl acetate–water and n butanol–water without
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