فهرست مطالب

Physical Chemistry Research - Volume:8 Issue: 4, Autumn 2020
  • Volume:8 Issue: 4, Autumn 2020
  • تاریخ انتشار: 1399/06/18
  • تعداد عناوین: 12
|
  • Masoomehalsadat Rahmati, Reza Fazaeli *, Masood Giahi Saravani, Reza Ghiasi Pages 585-608
    In this study, immobilized CuAlO2 onto the ZSM-12&35 composite was prepared and used as a photocatalyst to remove N-containing oil pollutants (Carbazole) through advanced oxidation. In this method, acetone is used as a reaction solvent that can be partially converted to fuel oxygenates compounds (Octane enhancers) through an aldol condensation reaction. Photocatalyst characterization was performed using X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDS), Mapping, and BET/BJH (Brunauer-Emmett-Teller & Barrett-Joyner-Halenda) techniques. The effect of operating parameters (contaminant concentration, catalyst dosage, and pH of the solution) on the efficiency of carbazole removal (model oil) was investigated through the RSM methodology. The removal products are identified by Gas Chromatography (GC-MAS) technique. The results indicated complete elimination of carbazole under mild conditions as well as the in-situ formation of typical fuel oxygenates compounds through aldol condensation among solvent molecules. Accordingly, this new protocol can be utilized to refine fuel products accompanied by enhancing their octane numbers.
    Keywords: Advanced oxidation, Carbazole, ZSM-12&35, photocatalyst, Fuel oxygenates
  • Zahra Yazdanpanahfard, Mohsen Oftadeh *, Sara Fahkraee Pages 609-627
    The interpretation of the ultrafast luminescence decay in [Re(Br(CO)3(N^N)] complexes as a new group of chromophoric imidazo[4,5-f]-1,10-phenanthroline ligands, including 1,2-dimethoxy benzene, tert-butyl benzene (L4) and 1,2,3-trimethoxy benzene, tert-butyl benzene (L6), was studied. Fac-[Re(Br(CO)3L4 and L6] with different aryl groups were calculated in singlet and triplet excited states. The calculations were performed in the gas phase and in the presence of chloroform as a solvent. The absorption and luminescence wavelengths, transition energy, and oscillator strength for singlet and triplet states were calculated for entitled complexes with L4 and L6 ligands. The UV-Vis spectrum and the singlet and triplet energy diagrams show a good agreement between our computational results and the experimental results, particularly in the case of a triplet state in chloroform. Spin-orbit coupling calculations show sufficient intensity and short wavelength in the UV-Vis absorption after SOC corrected absorption. The results of NBO calculations in the solvent show that rhenium acts as an acceptor by means of E(2), the second-order interaction energies between donor and acceptor orbitals, at the B3LYP/lanl2mb level of theory.
    Keywords: TD-DFT method, excited states, Intersystem crossing, Spin-orbit coupling, Rhenium(I) complexes
  • Mohammad Izadi, Hassan Sabzyan * Pages 629-644
    Reactive molecular dynamics simulations (RMDS) with the ReaxFF force field are used to study nucleation and growth of silica nanoparticles during flame synthesis from tetramethoxysilane (TMOS). Two reactive systems (A & B) are considered and formation and/or consumption of various reactants, intermediates and products are followed. In the RMDSs of system A (TMOS, O2, SiO2, and Ar), the temperature-dependence of the formation of initial SimOn seeds show that formation of transient SiO3C3H9 intermediate is an important stage in the conversion of TMOS to the initial SimOn seeds, which then aggregate to produce silica nanoparticles. Increasing temperature speeds up this conversion. Results of the RMDSs on system B (TMOS, O2, Ar, and {SimOn}; the SimOn seeds play the role of initial silica nanoparticles) show that at 2100 K, weak EFs (~1 V/Å) narrows the size distribution of the silica nanoparticles compared to that in the absence of EF while by application of stronger EFs (4-8 V/Å), the initial SimOn nanoparticles split into smaller species. In the absence of EF, increasing temperature from 1500 K to 3000 K increases sizes of the nanoparticles. The radial distribution functions, coordination numbers, and atomic compositions are used to characterize nanoparticles and evolution of the reaction.
    Keywords: Reactive molecular dynamics simulation, Silica Nanoparticle, Flame synthesis, Nucleation, electric field
  • Paria Nikparsa, Amirhosein Nikparsa, Ali Mirzaei * Pages 645-656
    Magnetic behavior of Co/Al2O3 catalyst in Fischer-Tropsch (FT) synthesis is performed using a magnetically fixed bed reactor. X-ray diffraction (XRD) spectroscopy, scanning electron microscope (SEM) method, Brunauer-Emmett-Teller (BET) method, and vibrating sample magnetometer (VSM) method are used to analyze the catalyst. Magnetic field of 0.015 T is suggested for CO hydrogenation on Co/Al2O3 catalyst with fixed bed reactor. Significant effects of magnetic fields are observed in the FT reaction of CO hydrogenation over Co/Al2O3 catalyst. The CO conversion value increases from 78% to 86% at 250 oC with external magnetic field. The apparent activation energy of FT reaction (102.33kJ/mol without external magnetic field) is reduced (96.45 kJ/mol with applying external magnetic field), and the catalytic activity of Co/Al2O3 catalyst is improved by applying the external magnetic fields during FT process at low temperatures (200-250 oC). The results indicated that the external magnetic fields improved both the rate of reaction and catalytic selectivity to desired hydrocarbons on Co/Al2O3 catalyst.
    Keywords: Magnetic field effect, Fixed-bed Reactor, CO hydrogenation, activation energy
  • Hossein Dashti Khavidaki *, Mousa Soleymani Pages 657-669

    In this study, the adsorption of alanine on pristine, functionalized, and boron and/or nitrogen doped functionalized C60 fullerenes was studied by theoretical methods. For this purpose, the structures of alanine, C60 fullerenes derivatives and complexes (C60-alanine) were optimized by using M062X/6-31G* level of theory. Then, it was calculated the adsorption energies, global DFT reactivity indices, the atomic charges and the global electron density transfer (GEDT). The results showed that the maximum adsorption energy occurs for the adsorption of alanine on C60H-OH derivative in both gaseous and aqueous phases. In addition, the doping three nitrogen/boron atoms with the functionalized carbon atom in C60H-OH increases the adsorption energy significantly. The results were confirmed by global DFT reactivity indices such as chemical potential and electrophilicity indices. In addition, analysis of the GEDT values showed that the charge transfer occurs from alanine toward C60H-OH fullerene in both phases upon adsorption. AIM results indicated that the interaction between alanine and C60H-OH in both gaseous and aqueous phases is non-covalent and hydrogen interaction.

    Keywords: Alanine, C60 fullerene, Functionalized C60 fullerenes, Doped functionalized C60 fullerenes
  • Sandip Pathade *, Bapu Jagdale Pages 671-687
    In the present work 4,6-bis(4-fluorophenyl)-5,6-dihydropyrimidin-2(1H)-one was synthesized by condensation of (2E)-1,3-bis(4-fluorophenyl)prop-2-en-1-one with urea in basic medium. The synthesized compound was characterized by using FT-IR and 1H NMR spectroscopic techniques. To determine the molecular structure of synthesized molecule some quantum chemical calculations were carried out by density functional theory (DFT) with employing B3LYP level at 6-311++G(d,p) basis set in gas phase, water and CCl4 solvents by using Gaussian-03 package. The optimized geometrical parameters, thermochemical parameters and global reactivity descriptors have been computed. The frontier molecular orbital (FMO) and molecular electrostatic potential (MEP) analysis also performed to explore the reactivity of title molecule at same level of theory. The vibrational frequencies of title molecule were analysed and compared with the corresponding experimental data. The results show fair correlation between the calculated frequencies in gas phase and experimental frequencies. The effect of water and CCl4 solvents on vibrational frequencies and global chemical reactivity descriptors were also examined. Obtained results show that polar solvent water decreased the carbonyl stretching frequency largely while other frequencies in water and CCl4 are slightly different than gas phase. There is no significant change by solvents were observed on energy gap (∆E) and global reactivity descriptors of studied molecule.
    Keywords: FT-IR, B3LYP, Quantum chemical calculations, Gaussian
  • Narmin Noorani *, Abbas Mehrdad Pages 689-703

    To improve the gas separation performance of poly (vinyl chloride) membrane, 1-vinyl imidazole was grafted onto the poly (vinyl chloride) by free radical graft copolymerization. The synthesized of the graft copolymer was characterized by the elemental analyzer technique (CHN). The prepared membrane morphology was surveyed by Scanning Electron Microscope (SEM). The properties of thermodynamics of CO2 adsorption were investigated at various temperatures and pressures by quartz crystal microbalance (QCM). The experimental data were correlated by the dual-mode model. The calculated thermodynamics parameters of CO2 adsorption display that CO2 adsorption has the nature of exothermic. Also, methane and carbon dioxide gas permeability was measured. The effects of variation of temperature and feed pressure on the membrane performance were surveyed. The increment in temperature cause to decrement the selectivity of membrane for carbon dioxide/methane gases; whiles, the selectivity of the membrane was incremented by incrementing feed pressure. The outcomes indicate that the permeation selectivity of the grafted copolymer is more than those of the poly (vinyl chloride) membrane for CO2/CH4 gasses. Moreover, Density functional theory (DFT) computes corroborated that the interaction energy of grafted copolymer with CO2 is stronger than this of CH4.

    Keywords: PVC, Vinylimidazole, Permeation, Adsorption capacity, DFT
  • Nahid Shajari *, Hooriyeh Yahyaei Pages 705-718
    The two-component reaction of phenol or naphthol derivatives and trichloroacetyl isocyanate in CH2Cl2 proceeded smoothly and cleanly at room temperature and aryl (trichloroacetyl)carbamate derivatives were formed in excellent yields and no side reactions were observed. The structures of the products were confirmed by IR, 1H NMR, 13C NMR, and elemental analysis. The data from IR spectra and 1H and 13C NMR chemical shifts computations of the aryl (trichloroacetyl)carbamate derivatives in the ground state were calculated by using density functional theory (DFT). The correlation graphic for compounds by the B3LYP method at the 6-311++G** basis set level in gas phase and CH2Cl2 solvent have been. There was an excellent agreement between the experimental and theoretical results.
    Keywords: Trichloroacetyl isocyanate, Carbamate, Density functional theory
  • Fatemeh Tabesh, Hassan Sabzyan * Pages 719-735
    Precursor spectroelectrochemical behavior of guanine is investigated based on UV-Vis absorption and fluorescence, and IR and Raman spectra of guanine and its radical cation in the presence of a model electrode, computed using (TD)M06/6-31++G** method. Effects of electrode potential ( ), molecule-electrode distance (d) and molecular orientations (θ) on this behavior are investigated. Results indicate that application of electric potential causes changes in the molecular structure and distribution of charge and spin densities, which consequently changes the electronic and vibrational characteristics of the system. Also, perturbation due to the applied electric potential, changes both the intensities and frequencies of the vibrational bands of the studied species. The absorption wavelength, and the peak intensity and width of the electronic spectra of guanine and its radical cation also show sensitivity to the applied electrode potential. Presence of solvent both as electrostatic medium and as explicit solvent (molecules) have significant effects on the spectroelectrochemical properties of guanine, and change the chemical activity of guanine radical cation formed by the electrode reaction. Furthermore, population and orbital analyses show that for all orientations, application of the electric potential by the electrode increases contribution of the inter-molecular (guanine→water) charge density displacement to the UV-Vis transitions.
    Keywords: Spectroelectrochemistry, DFT-M06, 6-31++G**, UV-Vis, Fluorescence, IR, raman spectra, Guanine, Radical cation
  • Vivek Pathania, Shrutila Sharma *, Shashi Vermani, B. Vermani, Navya Grover Pages 737-753
    A study of the interactions in non-aqueous system containing n-Butylammonium perchlorate is presented. The densities and ultrasonic velocities of n-Butylammonium perchlorate in binary mixtures of Acetonitrile and Dimethylsulfoxide at the temperature range from 298 to 328K under atmospheric pressure were measured. The binary mixtures contain 20, 40, 60 and 80 mol% of Dimethylsulfoxide and the concentration range taken is from 0.03-0.28 mol kg-1. Anton Paar density and sound velocity meter was used for measurement of densities and ultrasonic velocities. The experimental data have been employed to calculate various acoustical parameters like isentropic compressibility (βs), intermolecular free length (Lf), relaxation strength (r), specific acoustic impedance (Z), relative association (RA), Wada’s constant (W), Rao’s constant (R), Vander walls constant (b), molar volume (Vm) and free volume (Vf). The results of the derived acoustical parameters have been discussed as a function of salt concentration, solvent composition and temperature. Overall results shows appreciable solute-solvent interactions in Dimethylsulphoxide rich region of the binary mixtures studied and the extent of these interactions have been found to be decreasing with rise in temperature.
    Keywords: Isentropic compressibility, Acoustic Impedance, Acetonitrile, Dimethylsulfoxide, relative
  • Fatemeh Hafizi, S. Mohammad Hoseinpoor, Narges Nikoofard * Pages 755-765
    Advances in nano-fabrication techniques have enabled confinement of polymers at nano-scale cavities. This has raised a higher demand for development of theories for polymers in severe confinements. In this manuscript, the escape of a polymer confined in a nano-slit through a nano-pore in the strong confinement regime is investigated, theoretically and by using Langevin Dynamics (LD) simulations. The strong confinement occurs when the height of the nano-slit becomes smaller than the persistence length of the polymer. Persistence length is a measure of the polymer stiffness. The radius of gyrations R_g, the confinement force on the polymer f, and the ejection time of the polymer τ are obtained in different values of the polymer length L, the height of the nano-slit D, and the persistence length of the polymer P. The simulation results are well described with the scaling relations R_g/L^0.75 ~(P/D)^0.25 and f/L~(PD^5 )^(-0.4) and τ/L^2 ~(PD^2 )^0.42, respectively. The simulation results are in rather good agreement with the theory. It seems that the relative difference between theory and simulations is due to being close to the transition region between weak and strong confinement regimes.
    Keywords: Semi-flexible polymer, Nano-slit confinement, Strong confinement, Odijk regime
  • Zakarya Baouch, Benabadji Kamel Ismet *, Brahim Bouras Pages 767-787
    The structural evolution of cost-effective organo-clays, i.e. bentonite modified with various loadings of hexadecyltrimethylammonium bromide, from 50 to 200% of the cationic exchange capacity, was investigated. The materials BAS were prepared and then characterized by XRD, FTIR, and ATG/DTG analysis. The increase in the basal spacing, from 1.13 to 1.78 nm, was a sufficient confirmation that the surfactant cations were intercalated within the interlayer spaces of bentonite (BA). Batch adsorption experiments were performed to evaluate the adsorption efficiencies of Methylene Blue, Bezathren Red, and Telon Blue dyes on the surfactant-modified bentonite from an aqueous solution. In addition, the kinetic data were found to follow the pseudo second-order model for the adsorption processes of all three dyes. Afterwards, the equilibrium data were analyzed using the Langmuir and Freundlich isotherm models, and the Langmuir isotherm model turned out to be the most suitable to describe the adsorption of these dyes. It is worth indicating that the calculated Langmuir maximum adsorption capacities increased from 74 to 166.67 mg/g for Methylene Blue, from zero to 111.1 mg/g for Bezathren Red, and from zero to 500 mg/g for Telon Blue. The adsorption process was found to be endothermic in nature, in all cases.
    Keywords: Inorganic, organic hybrid materials, Adsorption mechanism, Cationic, Anionic, Vat dyes