Correlation between hysteresis of gas-liquid mass transfer and liquid distribution in a trickle bed

The hysteresis of gas-liquid mass transfer rate and the corresponding radial liquiddistribution in a trickle bed reactor are measured to provide evidence for the correlation between thesetwo behaviors.Experimental results indicate that the hysteresis of gas-liquid mass transfer originatesfrom the nonuniformity of the hydrodynamic state of gas-liquid flow and the radial maldistributionof local k_(gia) corresponds very well to the radial maldistribution of liquid flow in the bed.The localliquid flow rate is also found to be nonuniform in the azimuthal direction.In view of maldistributedliquid flow even in the pulsing flow regime,the conventional plug flow model seems oversimplifiedfor describing the behavior of a trickle bed.     

Low-dimensional compounds containing bioactive ligands. Part VI. Spectral and structural characterizations of a unique zinc(II) compound with biologically active ligand — clioquinol

The investigated compound of {[Zn(CQ)₂(H₂O)₂]₂[Zn(CQ)₂(H₂O)]₃}·5DMF·2H₂O (1) composition (where CQ = 5-chloro-7-iodo-quinolin-8-ol, DMF = N,N-dimethylformamide) was prepared by simple mixing of ZnCl₂ and CQ. Infrared spectroscopy confirmed the presence of CQ, DMF and H₂O molecules in the prepared compound. X-ray structural analysis revealed that the structure of the title compound consists of five independent Zn(II) atoms, which are coordinated by two bidentately coordinated molecules of CQ. Three of these central atoms are also coordinated by one water molecule, while the other two have two water molecules in the coordination sphere. The structure of 1 also includes five solvated DMF and two water molecules involved in thirteen hydrogen bonds, which interconnect different complex species to form four “triplets”, in the centre of which are units with hexacoordinated Zn atoms surrounded by two units with pentacoordinated Zn atoms. These triplets are linked together to chains parallel with the b axis by two kinds of π–π interactions.     

Antioxidant activity of phenolic compounds in 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidation: Synergistic and antagonistic effects

Interactions between phenolic antioxidants in binary systems were determined by adding two antioxidants simultaneously in equimolar proportions to an aqueous dispersion of linoleic acid that was then subjected to 2,2′-azobis (2-amidinopropane) dihydrochloride-induced oxidation and by evaluating the protective effect of the antioxidant mixture. The antioxidant power of the mixture was then compared with the expected antioxidant activity calculated by the sum of efficiencies of each compound separately, relative to their proportions in the mixture. If it was higher, a synergy was pointed out whereas a lower value was representative of an antagonism. Thus, synergistic effects were observed between rosmarinic acid and quercetin, or rosmarinic acid and caffeic acid, whereas antagonistic effects were obtained with the following mixtures: α-tocopherol/caffeic acid; α-tocopherol/rosmarinic acid; (+)-catechin/caffeic acid; and caffeic acid/quercetin. These mixture effects are partly explained by regeneration mechanisms between antioxidants, depending on the chemical structure of molecules and on the possible formation of stable intermolecular complexes.     

Study of a Polydimethylsiloxane (PDMS) Elastomer Generated by γ Irradiation: Correlation Between Properties (Thermal and Mechanical) and Structure (Crosslink Density Value)

The present study investigates the structural modification of polydimethylsiloxane (PDMS) with a molecular weight of 35 kDa, using varying high doses of gamma irradiation. Elastomeric structures with different crosslinked density values were obtained as a function of the gamma irradiation dose (250, 300, 350 and 400 kGy). The structural characterization of the obtained elastomers was performed by employing Fourier Transform Infrared, ²⁹Si Magic Angle Spinning Nuclear Magnetic Resonance and X-Ray Diffraction (FTIR, ²⁹Si MAS NMR and XRD), showing integration with the polymer chains by siloxane crosslinks (Type-Y) and methylene crosslinks (Type-H). The mechanical and thermal characterizations were carried out by employing dynamical-mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). The results showed an important correlation between the thermo-mechanical behavior and the irradiation dose. The thermal stability, analyzed by a thermo-gravimetric analysis (TGA), exhibited interesting behavior that suggested a direct correlation between the decomposition temperature and the structure generated by the gamma irradiation. These results suggest that the obtained elastomers could potentially be considered shape changing materials (SCM).     

Аntimicrobial and anticancer activity of new poly(propyleneamine) metallodendrimers

The synthesis, EPR characterisation and biological evaluation of two new metallodendrimers, i.e. a poly(propyleneamine) dendrimer functionalized at the external surface with 4-bromo-1,8-naphthalimide and conjugated with Cu(II) and Zn(II), was performed with the aim to evaluate their antimicrobial and anticancer activity. The antimicrobial activity was investigated in meat-peptone broth against bacteria B. subtilis and P. aeruginosa, and the yeast C. lipolytica. The results showed that the compounds inhibited effectively the tested pathogens even after their deposition on a textile fabric. Anticancer activity was investigated against three human permanent cell lines from non-small cell lung cancer (A549), triple negative breast cancer (MDA-MB-231) and carcinoma of the uterine cervix (HeLa) in the c?=?0.01–30 μM concentration range. The results suggest that these compounds are promising for application in biomedicine as anticancer drugs in the design of new effective preparations. The antimicrobial and anticancer activity may be related to the peculiar structural and dynamical properties revealed for the Cu(II) complexes, by a computer aided analysis of the electron paramagnetic resonance (EPR) spectra. This analysis indicated the formation, at the lowest Cu(II) concentrations, of a flexible rhombic Cu-N4 coordination with the internal amino groups of the dendrimer, which transformed into a Cu2-N4 coordination already at 0.25 equiv. of Cu(II).     

Synthesis,structure, and catalytic activity of a new chiral NHC–iridium(III) complex

The new chiral NHC–iridium complex 3 has been prepared in CH₃CN from the reaction between [Ir(COD)Cl]₂, NaOAc, KI, and dibenzimidazolium salt 2 which is derived from (S)-2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl. Complex 3 has been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analysis. It has a distorted-octahedral IrC₂N₂IH core structure, and shows good catalytic activity for the asymmetric hydrosilylation of arylmethyl ketones, leading to 1-arylethanol with moderate ee values.     

Synthesis of 1,1′-ferrocene bis(carboxypyrazole) compounds and displacement of the pyrazole ligands

The reaction of 1,1′-ferrocenedicarbonyl chloride with pyrazole or 3,5-dimethyl pyrazole generates novel 1,1′-ferrocene bis(amide) compounds 1 and 2, respectively. The crystal structure of 1 shows that the pyrazole rings are essentially co-planar with each other and with the cyclopentadienyl rings. Attempts to use the complexes as a chelating ligand were unsuccessful. Instead, treatment of 1 or 2 with Mo(CO)₄(pip)₂, pip = piperidine, led to displacement of the pyrazole ligands and formation of the known amide compound, 1,1′-ferrocene bis carbonyl piperidine. Replacement of the pyrazole is ascribed to the weakness of the amide bond caused by the aromaticity of the pyrazole ring. Crystal data for C₁₈H₁₄FeN₄O₂ (1): monoclinic P2(1)/c, a = 13.3907(18) Å, b = 10.2112(14) Å, c = 11.3082(16) Å, β = 105.209(2)°, V = 1492.1(4) Å³, Z = 4.     

Correlations between microstructural characterization and thermal properties of well defined poly(ε-caprolactone) samples by ring opening polymerization with neutral and cationic bis(2,4,6-triisopropylphenyl)tin(IV) compounds

In this paper a study of correlations between the microstructure of well defined poly(ε-caprolactone) (PCL) samples and their physical properties such as thermal degradation, crystallization kinetics and melting behavior is described. The PCL samples were obtained in the presence of the compound benzyl-methoxy-bis(2,4,6-triisopropylphenyl)tin (1), acting as single-site and living initiator, as well as in the presence of compounds Tip₂SnRR′ [Tip = 2,4,6-triisopropylbenzene; R = R′ = CHCH₂ (2); R = CH₂Ph, R′ = Br (3)] activated by ionizing agents. PCL samples having different end groups, molecular weight and molecular weight distribution were obtained. The samples were fully characterized by GPC and NMR. The thermal degradation of the synthesized samples were studied by thermogravimetric analysis (TGA) in air flow. The experimental results suggested that the presence of ester chain end groups has a beneficial effect on the thermal stability of the PCL samples, independently on the molecular weights and molecular weight distribution. The crystallization behavior was studied in isothermal conditions at 37 °C, 40 °C, and 43 °C through differential scanning calorimetry (DSC). In this case, either the molecular weight (M_w) or the polydispersivity index (PDI) have a significant effect on the kinetics of crystallization of PCLs.     

Synthesis and test of styrene—Cyclosiloxane and butadiene-cyclosiloxane block copolymers containing ultraviolet (UV) absorber and antioxidant groups

Block copolymers of polystyrene and poly(dimethylsiloxane) or of polybutadiene and poly(dimethylsiloxane) with nonhydrolyzably bound 2-hydroxybenzophenone and 2,6-di-tert-butylphenol residues were prepared by terminating the living block copolymers with glacial acetic acid to form siloxanol end groups, followed by condensation with diethoxysilyl derivatives of the stabilizers in the presence of dibutyltin dilaurate. The polymeric UV absorbers were proved to be nonextractable from polystyrene. At Xenotest aging (40°C) the polymeric UV absorbers were less effective than 2-hydroxy-4-octyloxybenzophenone. The polymeric antioxidants were superior to antioxidants of low molecular weight both in thermooxidative aging of vulcanized polybutadiene films at 70°C and in oxygen-uptake studies with stabilized polypropylene at 180°C over long periods.Siloxanes with Functional Groups, XII. XIth communication, cf. Ref. 1. Long-Term Stabilization of Polymers, VI. Vth communication, cf. Ref. 2.     

Preparation of single-site tin(IV) compounds and their use in the polymerization of ε-caprolactone

Butyltin(IV) carboxylate compounds were obtained by reactions of butyltrichlorotin(IV) with potassium pivalate, perfluoroheptanoate, methacrylate, 2,6-pyridinedicarboxylate, and phthalate. The synthesized complexes were fully characterized by nuclear magnetic resonance (¹H-, ¹³C-NMR), Fourier transform infrared (FTIR), mass spectroscopies (MS) and elemental analysis. These tin complexes were used as catalysts for the ring opening polymerization of ε-caplolactone and the conversion of monomers to polymers was completed in just 1 h. The structures of polymers were characterized by a combination of spectroscopic techniques (NMR, FTIR, MS), differential scanning calorimeter (DSC) and gel permeation chromatography. In this study, the ε-caplolactone polymers with different average molecular weights between 5000 and 40,000 Da having a regular structure were obtained.     

In situ UV‐VIS diffuse reflectance spectroscopy of reduction–reoxidation of heteropoly compounds by methanol and ethanol: a correlation between spectroscopic and catalytic data

The degree of reduction/oxidation of H₄PVMo₁₁O₄₀ (HPA) and Cs₂H₂PVMo₁₁O₄₀ (CsPA) was studied during reduction and reoxidation by methanol, ethanol and mixtures with oxygen, respectively. The peak intensity of the intervalence charge transfer (IVCT) band, the apparent band gap energy (E _g ^* ) and catalytic data were obtained by in situ UV‐VIS diffuse reflectance spectrosccopy (UV‐VIS‐DRS) and on‐line gas chromatography (GC), respectively. The peak intensity of the IVCT band and E _g ^* increase during the reduction of heteropoly compounds by the alcohols. The spectroscopic and catalytic data (conversion, selectivity) correlate in the transient state during the reoxidation process. It is shown that isolated Keggin anions act as precursors for the active states of the catalysts, which molecular structure cannot be deduced from UV‐VIS spectroscopy alone. UV‐VIS spectroscopy, however, can serve as a tool to determine the degree of reduction in future combined in situ UV‐VIS/Raman/XRD studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

A rare bond between a soft metal (FeI) and a relatively hard base (RO−, R = phenolic moiety)

Reacting a bidentate ligand H₂L, 2-(2-methoxybenzyl)-2-methylpropane-1,3-dithiol, with Fe₃(CO)₁₂ formed a diiron hexacarbonyl complex (1Me) from which a diiron hexacarbonyl complex (1H) pendant with a phenolic group was derived via in-situ demethylation. Further deprotonation of complex 1H gave a diiron pentacarbonyl species (1) in which a rare bond between the soft metal Fe^I and the relatively hard base phenolate formed, Fe^I-OR (R = phenolic moiety). This bonding may be a suitable mimic of the bonding feature, {Fe^IFe^I}R-OH/OH₂ found in the [FeFe]-hydrogenase.     

Synthesis and characterization of poly(N-acryloyl’-methyl piperazinium(+1)) tetrachlorometallate (II) compounds

Summary The interactions of metal ions with poly(N-acryloyl N-methyl piperazine) in the solid state were studied. The Cu(II) and Zn(II) compounds were prepared and characterized by means of elemental analysis; FT-IR, electronic spectroscopies, and thermogravimetric analysis. PM3 semiempirical calculations on the polymer conformations and the Zn(II) complex have been performed. The piperazine group in the polymer shows the conformations; namely; the chair and a distorted chair conformation. Both structures differ by just ca. 10 kcal/mol. In the compounds MCl₄(PAPH)₂ the MCl₄ ^2- complex ion presents a distorted tetrahedral geometry. The electronic spectrum of the yellow Cu(II) coordination compound shows a band at 894 nm. In the IR spectra, an absorption band at 3020 cm^-1 has been assigned to the v(N-H) stretching mode of the NH⁺ group. The protonated nitrogen atom is the one bonded to the methyl group due to the larger basicity according to the calculated electronic charge density and to the lower steric hindrance. The interaction of the MCl₄ ^2- anion and the polymer is achieved by hydrogen bonding at the NH⁺ group and the chloride with N-H ···Cl distances lying betwen 1.7 to 3.3 A°.     

NanoZnO initiated polymerization of N-vinylcarbazole (NVC) and evaluation of a poly(N-vinylcarbazole)–ZnO nanocomposite

The polymerization of N-vinylcarbazole was conducted in bulk in presence of ZnO without any external initiator and a nanocomposite of poly(N-vinylcarbazole)–ZnO (PNVC–ZnO) was isolated from the system. The polymerization of N-vinylcarbazole by ZnO impregnated with acetylene black (AB) and Fe³⁺ was also conducted to isolate the respective AB and Fe³⁺ loaded PNVC–ZnO composites, PNVC–ZnO(AB) and PNVC–ZnO(Fe³⁺). The formation of the poly(N-vinylcarbazole) in these systems was confirmed by FTIR, UV–vis and emission spectroscopic analysis. TGA, DSC and SEM characteristics of these composites were evaluated in details. XRD analysis revealed no crystanillity in poly(N-vinylcarbazole) moiety. PNVC–ZnO was nonconducting but PNVC–ZnO(AB) and PNVC–ZnO(Fe³⁺) systems exhibited conductivities in the range 0.12 and 10⁻³ S/cm respectively. A carbocationic propagation pathway was suggested to explain the initiation of N-vinylcarbazole by Zn⁺⁺ moiety in ZnO. Kinetic studies revealed that the polymerization is first order with respect to ZnO and the monomer concentration respectively.     

Partitioning of U(VI) and Eu(III) between Acidic Aqueous Al(NO3)3 and Tributyl Phosphate in n‐Dodecane

Abstract

The preferred approach to removing Al from Hanford tank sludges, based on aqueous alkaline leaching, often does not achieve complete success. Previous laboratory investigations on the treatment of Hanford tank sludge simulant samples indicate that an acidic scrub can enhance the dissolution of Al from various sludge matrices. If acidic leaching was deployed to enhance removal of tank waste residues, the resulting acidic Al(NO₃)₃ leachate solution could contain measurable amounts of solubilized transuranic elements and so would demand treatment prior to disposal. In this study, a liquid‐liquid extraction system for the decontamination of the HNO₃/Al(NO₃)₃ aqueous leachate by contact with 60% v/v tributyl phosphate (TBP)/n‐dodecane organic solution has been examined. The partitioning of U and Eu between the TBP phase and solutions of varying [HNO₃] and [Al(NO₃)₃] containing small amounts of Cr or ascorbic acid have been investigated._. The results indicate that >99% of both species could be removed from the aqueous phase using such a process.     

Synthesis,X-ray structure and catalytic properties of a copper(II) Schiff base complex modeling the activity of the CuB site of dopamine β-hydroxylase

The copper(II) complex [Cu(salgly)(bpy)]·4H₂O (1), where salgly is a tridentate glycinatosalicylaldimine Schiff base ligand, is prepared and structurally characterized. The complex is found to be catalytically active in the oxidation of ascorbic acid by dioxygen and the process is also effective in the presence of benzylamine giving benzaldehyde as a product, thus modeling the activity of the Cu_B site of dopamine β-hydroxylase.     

Correlation between local structure variations and critical temperature of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1-x(TiO2)x superconductor

TiO₂ doping content affects the critical temperature (T_c) and the variations of local structure on Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ. The (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ)_1-x(TiO₂)_x samples were fabricated with the solid-state reaction process, where x = 0, 0.002, 0.004, 0.006, 0.008, and 0.01. The T_c values of the samples were obtained by measuring resistivity versus temperature, indicating that T_c gradually decreased with increasing doping content (x). To explain the obtained degradation of T_c, carrier properties, role of interlayer coupling, and local structure were systematically investigated using Azlamozov–Larkin theory and its Lawrence–Doniach modification for strong anisotropic superconductors. The calculation of excess conductivity at the mean field region showed that the c-axis coherence length (ξ_c) and the effective inter-layering spacing (d) increased with increasing doping content. X-ray diffraction patterns also showed that the bond distances increased with increasing TiO₂ content. The copper valence (V) and carrier concentration (p) of the samples were determined by analyzing the Cu L_2,3-edge X-ray absorption near edge structure spectra. The values of V and p showed the same trend of decreasing with increasing x. A close correlation between the changes in local structure parameters and degradation of T_c of (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ)_1-x(TiO₂)_x was then probably concluded.     

Characterization of the Binding Interaction between Poly(Epicholorohydrin‐Diamine) and Reactive Dyes using a Multiple Linear Regression and Quartz Crystal Microbalance Methods

Abstract

The binding processes of Reactive Red K‐2BP (K‐2BP) and Reactive Violet K‐3R (K‐3R) onto poly(epicholorohydrin‐diamine)(PEPIDA) in solution and film were investigated by spectrophotometric and quartz crystal microbalance (QCM) methods, respectively. By using a multiple linear regression technique, the concentrations of the colored components in the mixtures of dye+PEPIDA were measured simultaneously from the absorbance spectra. The binding equilibrium constants for K‐3R and K‐2BP onto PEPIDA in solution were estimated to be 9.31×10⁶ and 1.86×10⁶ L · mol^?1, respectively. The difference in the color removal between K‐3R and K‐2BP by PEPIDA was discussed. The binding processes of K‐3R and K‐2BP onto PEPIDA film were followed by the QCM. The binding equilibrium constants were evaluated to be 1.27×10⁶ and 3.28 ×10⁵ L · mol^?1 for K‐3R and K‐2BP onto PEPIDA film, respectively. They are less than those determined in PEPIDA solutions. The binding rate constants for K‐3R and K‐2BP onto PEPIDA film were estimated to be 1.43×10⁵ and 1.72×10⁵ L · mol^?1 · s^?1, respectively.     

Investigation of electron-transfer reaction between alkaline hexacyanoferrate(III) and ranitidine hydrochloride – a histamine H2 receptor antagonist,in the presence of homogenous ruthenium(III) catalyst

The ruthenium(III)-catalyzed electron-transfer reaction between hexacyanoferrate(III) and ranitidine hydrochloride is studied in alkaline medium at 25°C and at an ionic strength of 1.10?mol/dm³. The reaction stoichiometry is established and is found to be 1:4, that is, for the oxidation of one mole of ranitidine, four moles of hexacyanoferrate(III) are consumed. The reaction products were characterized by spectral studies such as IR, GC-MS, ¹H-NMR and ¹³C-NMR. The reaction rate shows a less than unit order in substrate and alkali and a first-order dependence in oxidant, [Fe(CN)₆]^3? and the catalyst, ruthenium(III) concentrations. The active species of ruthenium(III), [Ru(H₂O)₅OH]²⁺, forms an intermediate complex with the substrate. The attack of complex by hexacyanoferrate(III) in the rate determining step produces a radical cation, which is further oxidized in the subsequent step to form the oxidation product. The effect of the reaction environment on the rate constant upon adding varying concentrations of KNO₃ and t-butanol was studied. The initially added products did not have any significant effect on the reaction rate. A plausible mechanism is proposed based on the experimental results. The effect of varying temperature on the reaction rate was also studied. The activation parameters for the slow step and the thermodynamic quantities for the equilibrium steps were evaluated.

The mechanism of title reaction has been studied and one mole of ranitidine consumes four moles of [Fe(CN)₆]^3?, as shown in the following equation:     

Titanium(IV) oxide photocatalyst of ultra-high activity: a new preparation process allowing compatibility of high adsorptivity and low electron–hole recombination probability

Microcrystalline anatase titanium(IV) oxide (TiO₂) particles were synthesized by hydrothermal crystallization in organic media (HyCOM) followed by calcination, and used in a photocatalytic reaction system of silver metal deposition. Upon elevating the post-calcination temperature, the photocatalytic activity was enhanced in spite of the simultaneous decrease in amount of surface-adsorbed Ag⁺. Comparison with the effect of calcination temperature on the other reaction systems revealed that the annealing effect became more significant with increasing number of electrons (or holes) required to complete the photocatalytic reaction process. This revised version was published online in July 2006 with corrections to the Cover Date.