فهرست مطالب

  • Volume:10 Issue: 1, 2020
  • تاریخ انتشار: 1399/01/23
  • تعداد عناوین: 10
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  • Manikandan Balakrishnan, Rita John * Pages 1-16
    The present study, describes the structural, electrical, and the photocatalytic activity of sol-gel synthesized TiO2- ZnO nanostructure. The synthesized mixed oxide nanostructure is characterized by XRD, FTIR, Raman, UV-Vis, FESEM, DLS and Impedance Spectroscopy analyses. In addition, photocatalytic activity of multiphase TiO2 (TAB)-ZnO (ZW) nanostructure is analysed using Methylene Blue dye as the model dye under UV and Visible light illumination. The XRD analysis confirms the bi-phase TiO2 and mono-phase ZnO in the multiphase TiO2-ZnO nanostructures. The average crystallite size of 33 nm has been estimated using Scherrer formula. The crystallite size and mechanical properties such as strain, stress, and other parameters are analysed using Williamson-Hall model. The FTIR spectrum shows the characteristics absorption peaks of TiO2 and ZnO at 679.44 and 432.79 cm-1 respectively, and reveals the presence of TiO2 and ZnO in the synthesized multiphase nanostructure. The optical band gap is calculated using Tauc relation with the data obtained from UV-Vis spectrometer. The calculated band gap value is 3.1 eV. The FESEM study shows the spherical morphology and the DLS analysis confirms the particle size is 433 nm. The presence of Ti-O and Zn–O stretching modes are confirmed from Raman spectrum. The electrical properties such as dielectric constant, dielectric loss, and ac conductivity are analysed from impedance data. The prepared multiphase TiO2 (TAB)-ZnO (ZW) nanostructure shows better photocatalytic activity in both UV and visible light region. The rate constant has been calculated as 0.0083 and 0.0052 min-1 for UV and visible light irradiation.
    Keywords: sol-gel, Multiphase TiO2-ZnO, Williamson-Hall model, Stress-Strain analysis, Photocatalysis
  • BiBi Fatemeh Mirjalili *, Mina Keihanfar Pages 17-22

    In this study, the nano-SiO2/hexamethylenetetramine as a new basic heterogeneous nanocatalyst was prepared and used for the synthesis of pyranopyrazole via the four-component reaction. Various aldehydes, hydrazine hydrate, ethyl acetoacetate and malononitrile were reacted at room temperature under solvent-free and grinding conditions. The morphology and structure of nano-catalyst were investigated by techniques such as FT-IR spectroscopy, FESEM, TEM, XRD, CHNS elemental analyzer and TGA. The structure of pyranopyrazoles was determined by spectroscopic data of FTIR and NMR. The principal affairs of this procedure are easy work-up, high yields, mild conditions and short reaction times.

    Keywords: Nano-SiO2, hexamethylenetetramine, Multicomponent reactions, Pyrano[2, 3-c]pyrazole, Basic nanocatalyst, reusable catalyst
  • Abdollrahman Mahmoodi, SeyedMahmood Mehdinia, Ayat Rahmani, Hamidreza Nassehinia * Pages 23-32

    This study was performed with the aim of investigating the efficiency of the Nano photocatalytic of ultraviolet and titanium dioxide compound and rice husk silica adsorbent (UV/TiO2/RHS) in removal reactive red 198 dye from synthetic aqueous solutions. The removal of reactive red 198 dye was done in batch reactors with a volume of 250 ml using RHS deposited by titanium dioxide in the presence of a UV lamp. The effect of pH, immobilization of TiO2 on RHS adsorbent, contact time, nanoparticle mass and initial concentration of dye in removal efficiency were investigated. The results of this research showed that with an increase in pH and alkalinity of the solution, the removal efficiency declined. As the pH changed from 3 to 9, the removal efficiency in UV/TiO2/RHS, RHS adsorbent and UVC radiation declined from 75.25 to 27.87, 8.37 to 3.4, and 16.62 to 3.25%, respectively. The maximum dye removal efficiency obtained by UV/TiO2/RHS was as large as 87.5% under pH=3, contact time of 60 min, nanoparticle mass of 1 g/L, and 25 mg/L concentration of the reactive red 198 dye. Therefore, the rice husk silica as a natural adsorbent in combination with (TiO2/UV) can be used as an effective method for removal reactive red of aqueous solutions on a larger scale by optimizing the parameters affecting the removal efficiency.

    Keywords: Photocatalyst, Rice husk silica, Reactive red 198, Removal efficiency
  • Hamed Abbasi * Pages 33-45
    The samples of spent chlorinated Pt/Al2O3 catalysts that were used in the isomerization process were decoked at elevated temperatures under airflow and different oxygen concentrations. The surface of the catalyst was characterized by thermal gravimetric analysis, differential scanning calorimetry, Brunauer-Emmett-Teller analysis, attenuated total reflection fast Fourier infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray elemental mapping. The effective parameters for the catalyst decoking optimized were coke burning temperature (450-600 ), temperature ramp (5-25 /min) and oxygen content of the feed gas (0.5-2.0% vol.) in a tubular fixed-bed reactor using the response surface experimental design method. The spectroscopic tests were set based on the absorbance at 1390 cm-1, representing the surface coverage of platinum-alumina, and the results revealed that the greatest safe regeneration of chlorinated Pt/Al2O3 catalyst is achieved under a specific concentration of oxygen, temperature domain and thermal ramp. Moreover, the mechanism and the reaction rates of the decoking step of the catalyst regeneration were examined and the kinetic parameters of chlorinated Pt/Al2O3 decoking were determined.
    Keywords: Catalyst fouling, Fixed-bed reactor, SEM mapping, Exothermic process, Catalyst deactivation
  • AbdolHossein Dabbagh, Marzie Naderi, Mehdi Zamani * Pages 47-55

    The influence of NaNO2, HNO3 and H2SO4 on the structure and morphology of gamma-alumina was investigated by XRD, BET, SEM and FT-IR spectroscopy. Selected amounts of NaNO2, HNO3 and H2SO4 were added to a solution of aluminum isopropoxide (as a precursor for the boehmite synthesis). The boehmite samples were calcined at 350 and 600 ℃ to form the semi-crystalline high surface area gamma-Al2O3. The reactivity and selectivity of the modified gamma-alumina catalysts were examined using dehydration reaction of 2-octanol. There was a good correlation between reactivity, selectivity and the amounts (and type) of the modification. The dominant product was cis-2-octene for all of the catalysts. Low conversion and high selectivity were obtained for dehydration of 2-octanol over alumina modified with NaNO2. High conversion, low selectivity and excessive isomerization were found for gamma-alumina catalyst modified with H2SO4.

    Keywords: Alumina, Dehydration, Alcohol, reactivity, Selectivity
  • Elmira Jahangard, Leila Khazdooz *, Amin Zarei Pages 57-63
    One of the important Multi-component reaction (MCRs) is the synthesis of dihydropyrano chromene derivatives by one-pot reaction. In this research, an inexpensive and effective one pot three component procedure with good yields for the synthesis of dihydro pyrano chromenes is reported. In this method, the synthesis of pyrano chromene derivatives was followed by using 4-hydroxycoumarin, malononitrile and aldehydes in the presence of catalytic amount of nano fluoro apatite doped with Mg and Si (Mg-Si-FA). It should be cited that all reactions were carried out in H2O/EtOH as the solvent under reflux condition and the corresponding products were obtained in good yields and pretty short reaction time. Moreover, the anti-bacterial properties of the present products were studied by determination of their minimum inhibitory concentration (MIC).
    Keywords: Dihydropyrano[3, 2-c]chromene, Multi-component reaction, Cooperative catalyst, Antibacterial activity
  • Zohreh Kheilkordi, Ghodsi Mohammadi Ziarani *, Alireza Badiei, Hossein Vojoudi Pages 65-70
    The acidic agent (SO3H) was stabilized on the silica coated Fe3O4 magnetic nanoparticles to produce Fe3O4@SiO2@Pr-SO3H, as a heterogeneous acidic catalyst, was designed, and then fully studied and characterized by FT-IR, XRD, TGA, DTA, TEM, and SEM analysis. Subsequently, the catalytic activity of Fe3O4@SiO2@PrSO3H was investigated by the one-pot four- component condensation reaction between 1,3-indandione, aromatic aldehydes, acetophenone or propiophenone and ammonium acetate under the solvent-free condition at 80 ℃. The main advantages of this magnetic and heterogeneous acidic catalyst are high product yields, being environmentally benign, short reaction times, and easily separated from the reaction mixture using an external magnet.
    Keywords: Fe3O4@SiO2@PrSO3H, Nanomagnetic heterogeneous catalyst, Indeno[1, 2-b]pyridines, multi component reaction, Solvent-free condition
  • Hassan Zakeri, Saeed Rayati *, Goldasteh Zarei, Ali Parsa, Forogh Adhami Pages 71-78
    A heterogeneous catalyst containing manganese Schiff base complex (derived from 2,4-dihydroxybenzadehyde and 1,2-phenylenediamine) is produced by covalent anchoring in MCM-41 matrix. The synthesized catalyst was characterized by X-ray diffraction pattern (XRD), inductivity coupled plasma (ICP), Fourier transform infrared (FT-IR) spectroscopy, N2 sorbtion-desorbtion isotherm and by transmission electron microscopy (TEM). The obtained catalyst was used in the epoxidation of alkenes with hydrogen peroxide. Furthermore, the effect of various parameters such as reaction time, temperature, amount of catalyst, oxidant and imidazole has been investigated. The catalyst reusability was investigated. Our result reveals that this catalyst shows high catalytic activity in the epoxidation of alkenes.
    Keywords: Alkene Epoxidation, Heterogeneous catalyst, MCM-41, Schiff base
  • Meysam Yarie * Pages 79-83

    Stereoelectronic effects is a bridge between structure and reactivity [1]. Anomeric effect plays an important role in the domain of stereoelectronic interaction and can be used for description of several unusual phenomena. Intramolecular negative hyperconjugation is also known as anomeric effect [2]. In anomeric effect, both donor (lone pairs) and acceptor groups (electronegative elements) coexist in a proper molecule. This coexistence causes the acceptor groups to prefer the axial position in anomeric position (Scheme 1) [1, 3-15]. Meysam Yarie was born in 1987 in Malayer/ Hamedan, Iran. He received his B.Sc. in Applied Chemistry from Malek-Ashtar University of Technology and M.Sc. in Organic Chemistry from Kurdistan University under the supervision of Dr. Kamal Amani. He received his Ph.D. from Bu-Ali Sina University under the supervision of Professor Mohammad Ali Zolfigol. He is currently working towards his Post-Doctoral under the supervision of Professor Mohammad Ali Zolfigol at Bu-Ali Sina University. His research interest is the design, synthesis, characterization and applications of task-specific catalysts, ionic liquids and molten salts in the organic synthesis.

    Keywords: anomeric effect, Anomeric based oxidation, Catalytic vinylogous anomeric based oxidation
  • Sima Kalhor * Pages 85-89

    Sima Kalhor was born in Qom, Iran in1988. He received his B.Sc. in applied Chemistry (2012) from Islamic Azad University Qom and M.Sc. in Organic Chemistry (2014) at Islamic Azad University Qom, Iran. Also, she is currently working towards her Ph.D. student in Organic Chemistry (2016) under the supervision of Prof. Mohammad Ali Zolfigol. Her research interest is the synthesis, characterization and applications of homogeneous and heterogeneous reagents and catalysts in organic synthesis.

    Keywords: [Pyridine-SO3H]X, Ionic liquids (ILs), spotlight