A zirconium Schiff base complex immobilized on starch-coated maghemite nanoparticles catalyzes heterogeneous condensation of 1,2-diamines with 1,2-dicarbonyl compounds

A magnetically separable zirconium Schiff base nanocatalyst was synthesized under ultrasonic agitation. TEM images revealed a uniform spherical particle shape with average size of 10–14 nm for the as-prepared catalyst. The catalytic performance of ZrOL₂@SMNP in the heterogeneous condensation of various 1,2-diamines and 1,2-dicarbonyls for the synthesis of heterocyclic compounds in ethanol has been explored.     

Economical Oxygenation of Olefins and Sulfides Catalyzed by New Molybdenum(VI) Tridentate Schiff Base Complexes: Synthesis and Crystal Structure

Abstract. New cis‐dioxomolybdenum(VI) complexes (MoO₂Y^xCH₃OH) were synthesized using MoO₂(acac)₂ and 2[(1‐hydroxy‐2‐methylpropane‐2‐ylimino)methyl]phenol derivatives as tridentate ONO donor Schiff base ligands (H₂Y^x). MoY¹ was crystallized in orthorhombic space group Pbca. The epoxidation of olefins using tert‐butyl hydroperoxide and oxidation of sulfides to the sulfoxides by hydrogen peroxide were efficiently enhanced by the catalytic activity of title Mo^VI complexes with excellent selectivity. The high efficiency and relative stability of the catalysts was observed by turnover number and UV/Vis investigations. The electron‐rich and bulky ligands promoted the effectiveness of the catalysts.     

A novel acrylonitrile–butadiene–styrene/poly(ethylene glycol) membrane: preparation,characterization, and gas permeation study

Polymeric membranes were prepared by blending different grades of poly(ethylene glycol) (PEG) as the added polymer with acrylonitrile–butadiene–styrene as the backbone structure. The membranes were characterized by Fourier transform infrared, X‐ray diffractometry, dynamic mechanical thermal analysis, differential scanning calorimetry, and scanning electron microscopy. Furthermore, the gas permeation and separation properties of CO₂/CH₄ were studied. In addition, the effect of pressure (1–8 bar) and the effect of PEG content (0–40 wt%) on CO₂ and CH₄ permeability/selectivity were investigated. The results showed that, in more cases, with the introduction of PEG molecules, CO₂/CH₄ selectivity increases without significant changes in CH₄ permeability, indicating that the incorporation of intermolecular interaction is suitable for the separation of gas pairs with no molecular size domination but the solution–diffusion. From the viewpoint of gas separation applications, the resultant data are in the commercially attractive region. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental study of hydrogen sulfide hydrate formation: Induction time in the presence and absence of kinetic inhibitor

In this paper, the effect of adding different concentrations of kinetic inhibitors on the induction time of hydrogen sulfide hydrate formation in a reactor equipped with automatic adjustable temperature controller is studied. A novel method namely “sudden cooling” is used for performing the relevant measurements, in which the induction time of H₂S hydrate in the presence/absence of PVP and L-tyrosine with different concentrations (100, 500, and 1000 ppm) is determined. As a result, PVP with the concentration of 1000 ppm in aqueous solution is detected as a more suitable material for increasing the induction time of H₂S hydrate formation among the investigated kinetic hydrate inhibitors.     

Fabrication of electrospun polyethersulfone/titanium dioxide (PES/TiO2) composite nanofibers membrane and its application for photocatalytic degradation of phenol in aqueous solution

The main objective of this research is to use the photocatalytic properties of PES/TiO₂ nanofibers membranes to remove the phenol as a toxic pollutant in various effluents. The uniform fibers in terms of minimum bead formation and fibers diameter were fabricated. Therefore, more TiO₂ catalysts are on the surface of the fibers which increase the active surface area of nanoparticles and consequently improve the phenol degradation efficiency. The effects of TiO₂ concentration on hydrophilicity, mechanical properties, porosity, mean pore size, and water flux of membranes were studied. The PES/TiO₂ nanofibers were evaluated for phenol degradation under UVA irradiation through a transparent membrane module. The amount of removable phenol was analyzed with high‐performance liquid chromatography. Central composite design was used as a statistical experimental design. Finally, the effect of TiO₂ content in nanofibers and initial phenol concentrations were investigated as well as pH values in synthetic wastewater, on phenol degradation. The results from analysis of variance (ANOVA) analysis indicated that TiO₂ content in nanofibers was the most important and effective parameter on phenol degradation. It was also presented that there is no significant interaction between parameters so that the effect of each parameter was investigated separately. Maximum phenol degradation was 43.0 ± 0.3% and found under conditions of TiO₂ content, initial phenol concentration, and pH value of 8%, 120 ppm, and 7, respectively.     

Advances in the Study of Gas Hydrates by Dielectric Spectroscopy

The influence of kinetic hydrate inhibitors on the process of natural gas hydrate nucleation was studied using the method of dielectric spectroscopy. The processes of gas hydrate formation and decomposition were monitored using the temperature dependence of the real component of the dielectric constant ε′(T). Analysis of the relaxation times τ and activation energy ΔE of the dielectric relaxation process revealed the inhibitor was involved in hydrogen bonding and the disruption of the local structures of water molecules.     

Triple-Diffusive Mixed Convection in a Porous Open Cavity

The triple-diffusive mixed convection heat and mass transfer of a mixture is analyzed in an enclosure filled with a Darcy porous medium. The mass transfer buoyancy effects due to concentration gradients of the dispersed components (pollutant components) are taken into account using the Boussinesq approximation model. The governing equations are transformed into a non-dimensional form, and six groups of non-dimensional parameters, including Darcy–Rayleigh number, Peclet number, two Lewis numbers for pollutant components 1 and 2 and two buoyancy ratio parameters for pollutant components 1 and 2, are introduced. The governing equations are numerically solved for various combinations of non-dimensional parameters using the finite element method. The effect of each group of non-dimensional parameters on the pollutant distribution and the heat transfer in the cavity is discussed. The results indicate that the presence of one pollutant component can significantly affect the pollutant distribution of the other component. When the Lewis number of a pollutant component is small, the increase in the bouncy ratio parameter of the proposed component always increases the Nusselt and Sherwood numbers in the cavity.     

Synthesis,Spectra Characterization,Electrochemical Behavior of Silyl Derivatives of Ferrocene

Ferrocenyl‐substituted silanes via the reaction between mono and dilithio‐ferrocene with trimethyl, trietheyl, vinyldimethyl or t‐butyldimethyl chlorosilanes is prepared. The electrochemical behaviors of these compounds were investigated by cyclic voltammetry. This work describes the electrochemical and electrocatalytic properties of carbon ceramic electrode (CCE) modified with ferrocene composites as a new electrocatalyst material.     

Supramolecular photocatalyst of Palladium (II) Encapsulated within Dendrimer on TiO2 nanoparticles for Photo‐induced Suzuki‐Miyaura and Sonogashira Cross‐Coupling reactions

In this study, synthesis, characterization and catalytic performance of a novel supramolecular photocatalytic system including palladium (II) encapsulated within amine‐terminated poly (triazine‐triamine) dendrimer modified TiO₂ nanoparticles (Pd (II) [PTATAD] @ TiO₂) is presented. The obtained nanodendritic catalyst was characterized by FT‐IR, ICP‐AES, XPS, EDS, TEM, TGA and UV‐DRS. The as‐prepared nanodendritic catalyst was shown to be highly active, selective, and recyclable for the Suzuki–Miyaura and Sonogashira cross‐coupling of a wide range of aryl halides including electron‐rich and electron‐poor and even aryl chlorides, affording the corresponding biaryl compounds in good to excellent yields under visible light irradiation. This study shows that visible light irradiation can drive the cross‐coupling reactions on the Pd (II) [PTATAD] @ TiO₂ under mild reaction conditions (27–30 °C) and no additional additives such as cocatalysts or phosphine ligands. So, we propose that the improved photoactivity predominantly benefits from the synergistic effects of Pd (II) amine‐terminated poly (triazine‐triamine) dendrimer on TiO₂ nanoparticles that cause efficient separation and photogenerated electron–hole pairs and photoredox capability of nanocatalyst which all of these advantages due to the tuning of band gap of catalyst in the visible light region.     

Silica iminopyridine-functionalized nanomaghemite enhances the oxygenation activity and durability of simple Co(II) salophen complex

A novel magnetically recoverable catalyst was produced by coordinative attachment of Co(II) salophen complex to silica iminopyridine (SIPy)-functionalized-γ-Fe₂O₃ magnetic nanoparticles (SMNP@SIPy/Co(II) salophen). The vibration spectra and compositional data provided sufficient evidences for the structural integrity of as-prepared organic–inorganic nanohybrid. The magnetic nanocatalyst proved to be an efficient and selective heterogeneous catalyst for oxidation of different benzylic alcohols and featured higher catalytic activity and stability than that of homogenous counterpart. A TOF of 151 h⁻¹ and TON of more than 322 were obtained for oxidation of 4-cholrobenzyl alcohol in this catalytic system. The supported catalyst could easily be recovered from the reaction mixture by an external magnetic field and reused for subsequent experiments with consistent catalytic activity.