Scientia Iranica
Volume:27 Issue: 3, May-Jun 2020

N-(2-Pyridylmethyl)-L-histidine functionalized Fe3O4 magnetic nanoparticles (PMHis@Fe3O4 MNPs) efficiently catalyzed three-component Mannich-type reaction of ketones, aromatic aldehydes and anilines, to synthesize β-amino ketones in good to high yields. Mannich adducts were obtained in moderate to high diastereoselectivity, favoring anti isomer. The imidazole moiety of PMHis residue on catalyst plays an important role in the diastereoselectivity. PMHis@Fe3O4 MNPs were prepared via simple coprecipitation from an aqueous solution of Fe2+ and Fe3+ ions using NH4OH in the presence of L-histidine, followed by reductive amination with 2-pyridine carbaldehyde in the presence of NaBH4. Obtained PMHis@Fe3O4 MNPs were characterized by FT-IR, XRD, VSM, BET, TGA, SEM, EDX and TEM analysis.

Fused benzo-4H-pyran, namely, 4H-chromene moiety is the leading formation block of several heter-ocyclic natural products with biological activity such as, antioxidant, antibacterial, antiviral, antifun-gal, hypotensive, diuretic, and antiallergenic, antileishmanial, anticoagulant and antitumor. Herein, one-pot three components of aldehyde, malononitrile and enolizable compounds in the presence of nano-kaoline/BFn/Fe3O4 catalytic system to improve the 4H-chromenes via domino Knoevenagel-Michael-cyclization coupling reaction is reported. The advantages of this protocol involve high yield of products, use of solvent-free condition, easy experimental work-up system, low reaction times, re-cyclable catalyst and green process which privilege it as an alternative for other analogous synthetic procedures. The structure of synthesized 4H-chromenes were elucidated by FT-IR, 1H NMR and 13C NMR.

Abstract. A thin film carbon monoxide (CO) gas sensor based on PEDOT:PSS/Fe (salen) has been developed using the spin coating technique on several glass pieces with interdigitated Au electrodes. The change in electrical resistance of the sensors with various content of dopants was measured in different CO gas concentrations and temperatures. It is found that Fe (salen) as a dopant can significantly improve the performance of PEDOT:PSS based gas sensors. Least square support vector regression (LSSVM) method was applied to predict the gas response characteristics of the films for different testing conditions. Modeling results show a satisfactory agreement with experimental findings.

The kinetic studies for acetone acidic oxidation with potassium permanganate in the absence and presence of CuO based nanocatalysts were carried out. The rate law and activation energy as kinetic parameters were evaluated for reaction with no catalyst and with 0, 2.5, 5 and 10 weight percentages of CuO on γ-Al2O3. Catalysts were prepared with impregnation method and were characterized using ICP-OES, XRD, BET, and TEM techniques. Products were analyzed with UV-VIS technique and examinations were performed with changing in concentration of a reactant and keeping constant the others to determine the order of the reaction for targeted one. Results showed that in the absence and presence of nano-catalysts, the order of reaction for all KMnO4, (CH3)2CO and H2SO4 were one. The rate constants for the reaction in the absence of catalyst and the presence of 0, 2.5, 5 and 10 wt% CuO were 0.0022, 0.0023, 0.0025, 0.0026 and 0.0029 L2.mole-2.min-1 as well as the relationship between the rate constants and temperature was investigated for each experiment and the activation energies for them were 56.767, 56.807, 53.978, 50.075 and, 46.774 kJ.mol-1, respectively. Also it was demonstrated that there was no relationship between the products concentrations and the rate of reaction.

A ZSM-5 supported membrane was synthesized by secondary growth method. The Pt-ZSM5 membrane was prepared by impregnation method. The membrane was characterized by single gas permeation step at room temperature. The isomerization of n-pentane was chosen as a probe reaction for evaluating the catalytic performance of the membrane. In particular, the effect of the space velocity and the time on stream were considered. After the catalytic tests, the membrane was characterized by SEM, EDX and XRD. N2 permeance for the membrane, after calcination, was equal to 2.9 × 10-7 mol/m2.s.Pa indicating a coverage of the larger support pores by the zeolite crystals. This results was also confirmed by the SEM investigation. In addition, XRD analysis showed as the ZSM-5 was the desired zeolite-type. During the catalytic tests, it was observed a decrease of the nC5 conversion and an increase of the iC5 selectivity with WHSV. The nC5 conversion was decreased from 2.5 to less than 0.5, with an enhancement in weight hourly space velocity (WHSV), while the selectivity increases from 30 to over 70. On the other hand, it's conversion on catalyst enhanced from 10% to approximately 38%, with an increase in the reaction temperature from 250 to 450°C.

Adhesion improvement of an acrylic-urethane paint on a bumper surface made from polypropylene/ethylene-propylene-diene monomer was investigated at long term after electrochemical treatment by 2N nitric acid and 0.6M Silver (II)-nitrate /2N nitric acid. The stability of the electrochemically treated samples was examined at different aging times by ATR and SEM. The results were also compared to those of the untreated and flame-treated samples. Accelerated UV weathering analysis along with morphology study by SEM approved the effectiveness of the Ag (II) treatment technique in long term particularly at curvature area of the bumper. For the Ag (II) treated samples, the increase in adhesion strength was sustained even after 650 hours exposure to UV irradiation in wet condition prior to bonding. In addition, the stability of the Ag (II)-treated surface was maintained for at least three months. In case of the flame-treated surface, hydrophobic recovery during aging in environment was found to reduce the polarity of the PP-EPDM surface. The pull-off test showed Ag (II) treatment can enhance adhesion strength of the acrylic-urethane coating on to PP-EPDM in comparison with the flaming method by 20.7%. Moreover the results of zeta potential analysis for Ag (II) treated blend showed a typical acidic surface.

Gas separation process by the membrane is performed without changing the phase. For this reason, the costs are decreased. This study examined gas separation in Polyacrylonitrile (PAN) and Polysulfone (PSF) blend membranes. The ratio of polymers to mixed matrix membranes was considered 100% PAN, 100% PSF, (95% PAN -5% PSF), (90% PAN-10% PSF), (85% PAN-15% PSF). The best combi-nation of mixture was determined. Then, iron oxide nanoparticles with different weight percentages were placed on the membrane. The impact of adding different values of iron oxide nanoparticles in membrane was examined on separation of gas. Adding iron oxide nanoparticles to the membrane by 10% weight and measuring the value of permeability, it was observed that the permeability of this membrane for carbon dioxide, oxygen, nitrogen, and methane gases increased by 117%, 137%, 95%, and 53% compared to membranes without iron oxide nanoparticles. Examining the findings, it was re-vealed that the optimal value of adding iron oxide to improve the membrane properties was 10% by weight.

Electrocoagulation process with direct and alternative current as inductive by using Fe and Al rods with different arrangements and polarity inverter and the factors related to the efficacy of the process. EC process efficacy was investigated in a batch mode under different conditions. Also the amount of energy and electrode consumption and the amount of sludge produced were determined. The highest efficiency of decreasing total hardness (98.26%) and calcium hardness (87.69%) was obtained by using alternative current with Fe-Al electrode arrangement under optimal conditions (pH of 9, current density of 9 mA/cm2 and reaction time of 12 min). Optimum charge loading was 0.54 F/m3. The maximum energy and electrode were consumed in optimum current density by using direct current, which was 2.47 kwh/m3 and 2.12 kg/m3, respectively. The maximum sludge production was in optimum current density by using alternative current of 0.098 kg/m3 and with the settleability of 0.075 L/g and by using direct current with disposing capacity of 0.063 L/g. This study showed that EC technology by using alternative current and using Fe electrodes can be used as an alternative and new method for decreasing water hardness with high efficiency and low energy consumption.

The complexity behavior lies in many natural phenomena’s, such as our ecosystems, the earth’s climate, the behavior of the animal group, living cells and our brain. Therefore, a new field of “systems chemistry” is emerging, which aims to capture the complexity observed in natural systems within a synthetic chemical framework. To understand the physical behavior of the chemical components in a reaction mechanism (system), we need to understand the overall (complete) reactions network as well as different available reaction-paths. We propose the development of a multi-route reaction mechanism for a complex chemical reaction mechanism which is unsolvable through a common way. Further, invariant manifold approximation has been constructed through the Quasi Equilibrium Manifold. The numerical results have been tabulated along with the graphical view through MATLAB