Influence of Traces of Water on Adsorption and Diffusion of Hydrocarbons in NaX Zeolite

Measurements have been performed on the influence of a small amount of water on adsorption properties of alkanes (C₃ to C₆) and olefins (C₃ and C₄) in NaX zeolite. Adsorption capacity and heat of adsorption have been measured by a Volume Step method. Kinetics has been measured by Thermal Frequency Response method and the results have been compared with the results obtained by PFG-NMR.It has been found that water reduces the adsorption capacity especially at low adsorbate concentration. The heat of adsorption is slightly reduced by water. The kinetics of alkanes is always reduced by the adsorbed water. On the contrary, the diffusion kinetics of olefins is improved or remains unchanged, depending of the sorbat concentration.     

Study of solvents effect on distribution of configurational and conformational isomers of apo-tirucallol theoretically and experimentally

The adsorption of carbon monoxide on the rutile (1 1 0) and the anatase (1 0 1) surfaces has been investigated by a periodic approach using hybrid-exchange density functional theory; the quantum-mechanical study on the CO adsorption on the anatase surface has been carried out for the first time. The full optimization of the systems has been performed by considering different surface coverages and periodicities. The adsorption energetics have been investigated, on the basis of a recently proposed model, in terms of interaction, distortion and binding energies and the lateral effects have been analyzed using a simple model of nearest and next-nearest neighboring molecules. The experimental adsorbed CO stretching frequencies have been compared with the computed ones obtained by considering the highest investigated periodicity. The Lewis acidity of the two surfaces is comparable and the rutile (1 1 0) acid site seems to be slightly more electrophilic than that of the anatase (1 0 1) one.     

Thermodynamics of coupled reactions by the amplitudes of chemical relaxation

The amplitudes of the relaxation curves, as obtained by the Temperature-jump method have been used to measure simultaneously equilibrium constant and enthalpy for the reaction of complex formation of Ni²⁺ ion by 2,6-dihydroxobenzoic acid in the presence of a buffer. The experiments have been performed by changing the concentration of metal ion at constant ligand concentration andpH as in a complexometric titration. The points of such ‘dynamic titrations’ have been analysed by means of the concept of ‘normal reactions’ which enabled us to transform a set of coupled individual steps into a set of kinetically independent reactions. The potentialities of the dynamic titrations are discussed.     

Spectroscopic studies on the influence of 10 mol% of glycine on nonlinear optical crystal L-valinium picrate

Nonlinear optics is a fascinating field, which plays a vital role in the emerging field of photonics and optoelectronics. A new nonlinear optical crystal of glycine mixed l-valine picrate (GVP) have been grown from saturated aqueous solution by slow evaporation method at a temperature of 36 °C using a constant temperature bath of accuracy of ±0.01 °C. The synthesized organic optical material has been purified by repeated recrystallization. Single crystal X-ray diffraction analysis has been made to determine the cell parameters and it confirms the crystal lattice to be orthorhombic. UV–vis-NIR spectrum have recorded for GVP crystals in the range from 190 nm to 1100 nm and it is found that the crystal has cut-off at 450 nm. Fourier transform infrared transmission has confirmed the presence of the functional group present in the title compound. The spectrum has been recorded by KBr pellet technique. The ¹H and ¹³C NMR spectra have been recorded to elucidate the molecular structure of GVP crystals. The second harmonic generation (SHG) of the grown crystal have been confirmed by Kurtz–Perry method using Nd:YAG laser as source.     

Thermogravimetric studies on the reduction of hematite ore fines by a surrounding layer of coal or char fines: Part 1. Isothermal kinetic studies

Although there is a good deal of literature on the reduction of iron oxide by carbonaceous materials, it mostly covers systems where the oxide and reductant are thoroughly mixed. The present work concerns a system where the oxide and the reductant are not mixed.The kinetics of isothermal reduction of a central column of ore fines by a surrounding layer of coal fines have been studied by thermogravimetry. The course of reaction has been expressed in terms of a “degree of reaction” (f) defined as weight loss measured at a given time (t) with respect to the maximum possible weight loss. The kinetic data expressed in terms of f have been analysed using a kinetic law appropriate for diffusion-controlled processes and apparent activation energies have been calculated for reduction by coal and char. The results have been interpreted to identify carbon gasification as the rate-controlling step.     

Thermal degradation studies of substituted conducting polyanilines

The synthesis of conducting polymers based on m-nitroaniline, m-chloroaniline and m-aminophenol by aniline initiated ammonium peroxydisulfate oxidation, has been attempted. The IR spectra of the polymers have been studied. Thermogravimetric analysis of the conducting polymers has been followed using a computer analysis method LOTUS PACKAGE, developed by us for assigning the degradation mechanism. A number of equations have been used to evaluate the kinetic parameters. The mechanism of degradation of the conducting polymers has been explained on the basis of their kinetic parameters.     

Radiation induced polymerization of isoprene: A spectroscopic study

Isoprene polymerizes under the action of γ-radiation from a ⁶⁰Co source yielding a low molecular weight polyisoprene which remains soluble in the unreacted monomer. The electronic absorption spectrum of polyisoprene oligomer in isoprene monomer has been explained using squalene, a polyisoprene hexamer, as model compound. The radiation chemical yield for polyisoprene formation has been estimated from both gravimetric and spectrophotometric data pertaining the amount of polymer formed. An average G value of 35 molecules/100 eV has been determined suggesting that the polymerization mechanism involves free radicals. The chemical structure of the resulting polyisoprene radio-oligomer has been determined by FT-IR spectroscopy and found identical to that of a reference polyisoprene sample prepared by a chemically-initiated free radical polymerization process. The structure determination by FT-IR spectroscopy has been reported in detail.     

The role of microstructure in the pyrolysis of polypropylene. A preliminary study on the syndiotactic stereoisomer

The pyrolysis of two syndiotactic polypropylene samples with different molar mass and microstructure has been studied by means of TGA. The volatiles evolved have been analysed as a whole by mass spectrometry. The relative content of the different low mass alkenes, alkanes and dienes provides a fingerprint which has been used to asses the similarity of the mechanism. The changes in the apparent E_a with conversion have been shown by means of the Friedman’s method.The results show that, even though the chemical pattern is identical in both samples, important differences in the E_a trends are found. Such disparity in the energy requirements for the pyrolysis to take place can be reasonably attributed to the different microstructure of the samples.     

Functionalized electrospun mats from styrene-maleic anhydride copolymers for immobilization of acetylcholinesterase

A series of electrospun mats of styrene-maleic anhydride copolymers has been functionalized by modification with two types of spacers - a polymer with a flexible hydrophilic polyether chain (Jeffamine® ED) and a rigid low-molecular-weight spacer (р-phenylenediamine). The successful modification of the microfibrous mats with these bifunctional compounds has been proved by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. In a further step, acetylcholinesterase (AChE) has been covalently immobilized onto the modified mats using glutaraldehyde as a binding agent. The amount of bound protein and the specific activity of the immobilized AChE have been determined. The highest activity has been displayed by AChE covalently bound to Jeffamine-modified microfibrous mats. Moreover, the immobilized AChE is characterized by enhanced thermal and storage stability as compared to the free enzyme.     

Synthesis of a novel copolymer using glycogen and poly(lactide) as a carrier of dual drugs—ornidazole and ofloxacin

Biodegradability and biocompatibility are two crucial prerequisites for a promising therapeutic vehicle. Herein, a novel biocompatible copolymer has been synthesized using glycogen and polylactide (PLA). Glycogen, a naturally occurring biopolymer has been functionalized by methacrylation. On the other hand, lactide has been polymerized through ring opening polymerization (ROP), initiated by hydroxyethyl methacrylate (HEMA) and catalyzed by tin (II) 2‐ethyl hexanoate. Finally, the synthesized two substrates (i.e., glycogen methacrylate and PLA‐HEMA) are covalently connected by free‐radical polymerization, initiated by AIBN. The structure of the developed copolymer has been confirmed using ¹H and ¹³C NMR spectral analyses. The gel characteristics have been evaluated by rheological studies, while the morphological assessment has been investigated by FESEM analysis. In vitro cytocompatibility study reveals that the hydrogel (Gly‐co‐PLA) is biocompatible. The in vitro and in vivo release studies demonstrate the excellent pH‐sensitive control release profile of dual drugs: ornidazole and ofloxacin. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1697–1703     

Elucidation of the Structure of Products of Triphenylphosphine Electrooxidation in the Presence of Camphene

The structure of the products of anodic oxidation of triphenylphosphine in the presence of camphene carried out in acetonitrile with sodium perchlorate as supporting electrolyte has been studied. The major product, triphenylphosphine oxide, has been isolated from the solution in the form of cocrystals of free triphenylphosphine oxide and its complex with sodium perchlorate. The molecular structure of the cocrystals has been studied by X-ray diffraction analysis. Triphenylcamphenylphosphonium perchlorate, bornylacetamide, and a terpene compound with triphenylphosphonium and acetamide substituents in the cycle have been detected by NMR ¹³C as the electrolysis side products.

     

Effect of manganese nanoparticles on the mechanical, thermal and fire properties of polypropylene multifilament yarn

Polypropylene filled with 10 wt% of inorganic nanoparticles has been prepared by melt blending. The fillers investigated were manganese oxides (MnO and Mn₂O₃) and manganese oxalate (MnC₂O₄). The morphology and thermal stability of these nanocomposites have been studied by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The experimental results reveal that the addition of 10 wt% manganese oxides improves the thermal stability in air of polypropylene by about 70-80 °C. In a second step, these nanocomposites have been processed by melt spinning in order to produce multifilament yarn. The mechanical properties of these filaments have then been characterized. It is shown that just the addition of Mn₂O₃ improves the mechanical properties of polypropylene filaments. The flammability of these nanocomposites used as knitted fabrics has finally been evaluated with a mass loss calorimeter at 35 kW/m². This kind of experiment has not revealed a real improvement of fire properties.     

Thermal oxidation of clay-nanoreinforced polypropylene

The thermo-oxidation process at low temperatures for a montmorillonite-nanoreinforced polypropylene (PP) was studied. Experimental aging kinetic data at 100, 80 and 60 °C have been obtained and compared with a computational simulation in which a kinetic model based on the closed loop approach was used. As a result, it has been found that the montmorillonite role is not limited to a role of inert filler in the polymer matrix but induces a slight catalytic effect leading to induction period reduction. This effect has been well simulated by increasing initial hydroperoxyde concentration. The consequences of kinetic control by oxygen diffusion have also been investigated by using micro ATR-FTIR mapping to assess concentration profiles of the oxidation products across the sample thickness. It has been found that the oxidized layer thickness is close to 17 μm for the pure polypropylene whereas it is around 10 μm for the nanocomposite at 100 °C. These profile variations have been attributed to differences in oxygen diffusion coefficient values. Simulations based on the kinetic model including diffusion-reaction coupling describe these profiles well.     

13C NMR spectroscopy of natural substances: IV—13C NMR studies of trachylobane diterpenes: Complete carbon assignment

The diterpene trachylobane and a series of derivatives have been completely analysed by FT ¹³C NMR spectroscopy. All ¹³C frequencies for trachylobanol have been unambiguously assigned by experimental techniques, i.e. by proton single-frequency selective decoupling and shift reagent experiments. Shift calculations have been performed for the parent compound by using known methods. The results are discussed in comparison with the experimental data. Satisfactory agreement between predicted and experimental values has been obtained.     

Abatement of volatile organic compounds using an annular photocatalytic reactor: Study of gaseous acetone

Photocatalytic oxidation of organic compounds in gas phase appears to be a promising process for remediation of polluted air. In the present work, the photocatalytic degradation of acetone, which is a typical pollutant of indoor air, was investigated by using an annular photoreactor. After a modelling by a cascade of elementary continuously stirred tank reactor, the annular photoreactor was assimilated to a plug flow reactor (PFR). No transfer limitation (external and internal) has been demonstrated for this reactor with the fibreglass photocatalytic support. The influence of several kinetic parameters has been studied such as pollutant concentration, incident light irradiance, contact time and humidity content. The Langmuir–Hinshelwood model has been verified for acetone. It can be noticed that no by-products have been detected by FID suggesting almost total mineralization. The possible minor gaseous by-products have been accumulated into a mixture of ethanol–liquid nitrogen at −50 °C then a sample of it has been injected into a GC/MS for analysis. A mechanistic pathway is then proposed for the photocatalytic degradation of acetone.     

Effect of vegetable oils on obtaining lipid nanocarriers for sea buckthorn extract encapsulation

The principal aim of the present study was to develop new safe and highly antioxidant nanostructured lipid carriers loaded with sea buckthorn extract. Three vegetable oils — grape seed oil, sea buckthorn oil and St. John's wort oil (Hypericum perforatum oil) — were used as matrix components and the modified high shear homogenization technique has been employed for the synthesis of nanostructured materials. The effect of these oils on the antioxidant and antimicrobial activities of loaded sea buckthorn extract — nanostructured lipid carriers — has also been studied. For this purpose, a combination of two solid lipids: cetyl palmitate with glyceryl stearate and lecithin/block copolymer has been used. The obtained nanostructured lipid carriers have been characterized for the particle size and zeta potential by means of dynamic light scattering measurements. The nano-dimension morphology of loaded nanostructured lipid carriers was confirmed by transmission electron microscopy. Their crystallinity measured by differential scanning calorimetry has revealed a high disordered lipid matrix. The properties of sea-buckthorn-extract-loaded nanoparticles have been evaluated by an appropriate in vitro analysis (chemiluminescence method). The presence of the three vegetable oils influences extensively the antioxidant properties of the developed nano-formulations, as has been demonstrated using the chemiluminescence technique. The antimicrobial activity of the studied nanostructured lipid carriers, analyzed by the diffusion disc method, shows in most of the samples a high efficiency against Escherichia coli bacteria.     

Decontamination of some radioactive effluents by means of ceramic filters

The paper deals with the use of some ceramic materials for the removal of⁵⁵⁺⁵⁹Fe³⁺ and⁶⁰Co²⁺ ions from residual waters. For this purpose, chamotte powder has been used both by itself or in a mixture with aluminium oxide. The pastes obtained by wetting these materials have been shaped in the form of crucibles. The radioactive ions which exist in residual effluents, have been retained to a large extent on these filters. Separately, the leaching of radioactive ions previously retained on the filtering mass, has been studied under the influence of water and of diluted solutions of hydrochloric acid or sodium chloride.     

Microhardness of compatibilized blends of polypropylene with a semiflexible liquid-crystalline polymer

 The Vickers microhardness of blends of isotactic polypropylene and a semiflexible liquid-crystalline polymer (iPP/LCP 90/10 and 80/20 w/w), compatibilized with 2.5, 5 or 10 wt% PP-g-LCP copolymers with different composition has been studied. It has been shown that the microhardness values of uncompatibilized blends are close to the additive ones, while for compatibilized blends a strong positive deviation from additivity has been established. This result is interpreted by the increase in the degree of crystallinity of PP, by the decrease in the surface free energy of PP crystals and by the decrease in the surface free energy of the LC domains when the PP-g-LCP compatibilizer is present. The effect of the composition and concentration of the compatibilizer on the experimental hardness values has also been studied. The values of the microhardness/modulus of elasticity of some of the materials have been obtained. It is demonstrated that according to these values the compatibilized blends take a position closer to the elastic material in the elastic–plastic spectrum than the uncompatibilized blends. The results are interpreted by the compatibilizing efficiency of PP-g-LCP copolymers towards iPP/LCP blends. Received: 18 June 2001 Accepted: 4 October 2001     

Optical nonlinearity of organic dyes as studied by Z-scan and transient grating techniques

The excited state absorption cross-section of 5,5′-dichloro-11-diphenyl-amino-3,3′-diethyl-10, 12-ethylinethiatricarbocyanine perchlorate (IR140) have been measured by using a single beam transmission technique. Z-scan experiments have been used to find out a few nonlinear parameters. The excited state relaxation times have also been measured by using laser induced transient grating (LITG) technique.     

Synthesis of Quinaldinic Acid Amide Derivative of Styrene-Divinylbenzene Copolymer and its Application in Preconcentration of Mercury (II)

Abstract

A new chelating resin has been synthesized by introducing a quinaldinic acid amide group into styrenedivinyl benzene (8%) copolymer beads. The resin is stable in fairly strong acids or alkali and has been characterized by elemental analysis for nitrogen and from i.r. spectra. The water regain value is 0.37g/g. The sorption patterns of Na(I), K(I), Ca(II), Mg(II), Pb(II), Cu(II), Ni(II), Zn(II), Cd(II), Hg(II) and Fe(III) on the chelating resin have been studied as a function of pH. The resin selectively sorbs Hg(II) ever a wide pH-range of 2.5–7.6 with high efficiency. The maximum exchange capacity for Hg(II) is 1.98 mmols g^?1 at pH 5.5. Over 99% of Hg(II) sorbed has been recovered by using 10% thiourea in 1M HClO₄ both by batch and column operations. The has been utilized in the preconcentration and recovery of Hg(II) from industrial and laboratory waste water.