Band 65, Heft 3

Production of hydrogen by steam-reforming of ethanol has been performed using different catalytic systems. The present review focuses on various catalyst systems used for this purpose. The activity of catalysts depends on several factors such as the nature of the active metal catalyst and the catalyst support, the precursor used, the method adopted for catalyst preparation, and the presence of promoters as well as reaction conditions like the water-to-ethanol molar ratio, temperature, and space velocity. Among the active metals used to date for hydrogen production from ethanol, promoted-Ni is found to be a suitable choice in terms of the activity of the resulting catalyst. Cu is the most commonly used promoter with nickel-based catalysts to overcome the inactivity of nickel in the water-gas shift reaction. γ-Al2O3 support has been preferred by many researchers because of its ability to withstand reaction conditions. However, γ-Al2O3, being acidic, possesses the disadvantage of favouring ethanol dehydration to ethylene which is considered to be a source of carbon deposit found on the catalyst. To overcome this difficulty and to obtain the long-term catalyst stability, basic oxide supports such as CeO2, MgO, La2O3, etc. are mixed with alumina which neutralises the acidic sites. Most of the catalysts which can provide higher ethanol conversion and hydrogen selectivity were prepared by a combination of impregnation method and sol-gel method. High temperature and high water-to-ethanol molar ratio are two important factors in increasing the ethanol conversion and hydrogen selectivity, whereas an increase in pressure can adversely affect hydrogen production.

A novel and easy method for the separation of inorganic anions by capillary electrophoresis using a polymeric ionic liquid (PIL), poly(1-vinyl-3-butylimidazolium bromide) as a background electrolyte modifier has been developed. The PIL has been proved to generate a reversed electroosmotic flow which reduces the analysis time and improves the separation significantly. Effects of the PIL concentration and buffer composition (pH and concentration) were evaluated on basis of the resolution and efficiency of the sample. Under optimum conditions, good separation of six model inorganic anions was achieved with high efficiency and excellent reproducibility within 3 min. The results obtained indicate that the combination of reversed EOF and the association between the analytes and the PIL on the capillary wall or BGE play a prominent role in the separation of anions. Therefore, the PIL presents a useful alternative for the BGE modifier in the study of inorganic anions by CE.

Hydrophilic β-cyclodextrin (β-CD) and its derivatives are not soluble in organic liquids but they are highly soluble in water and can interact with enantiomers selectively to form diastereomeric complexes which enable their use as chiral selectors in chiral solvent extraction. In this paper, terbutaline enantiomers were extracted by hydrophilic β-CD derivatives in an aqueous/organic biphasic solvent system with racemic terbutaline in the organic phase and β-CD in the aqueous phase. Five β-CD derivatives, namely: methyl-β-cyclodextrin (Me-β-CD), hydroxyethyl-β-cyclodextrin (HE-β-CD), 2-hydroxyethyl-β-cyclodextrin (2-HE-β-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) and (4-sulfobutylether)-β-cyclodextrin (SBE-β-CD) were used as hydrophilic selectors, respectively. Process variables affecting extraction efficiency were investigated, namely influence of the type of organic solvents and β-CD derivatives, concentrations of selectors and terbutaline enantiomers, pH, and temperature. Experimental results show that the efficiency of extraction depends, often strongly, on process variables. All five β-CD derivatives studied preferentially extract the more biologically active (R)-terbutaline from the organic phase; HP-β-CD has the strongest recognition ability. The maximum enantioselectivity (α) of 1.42 was achieved under optimal conditions: pH 7.0 and temperature of 5°C. Utilization of the extraction method for separation of terbutaline enantiomers is expected to be cheap and easy to scale up to commercial scale.

Zeolite-based photocatalysts were prepared by the sol-gel and deposition methods. The photocatalysts were characterised by X-ray diffraction, nitrogen adsorption-desorption isotherms, FTIR spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectrometry. The activity of the prepared photocatalysts was evaluated by the UV-induced degradation of acid blue 92, a textile dye in common use. The effect of various parameters, such as catalyst concentration, initial dye concentration, thiosulphate concentration and pH, on the rate and efficiency of the photocatalytic degradation of acid blue 92 was investigated. The results showed that each parameter influenced the degradation rate and efficiency in a particular way. It was also found that, under optimised conditions, Ag/AgBr/TiO2/zeolite exhibited the highest photocatalytic performance. A comparison of catalytic activity when exposed to visible light under the same conditions showed that the photocatalysts containing AgBr had the highest activity.

This paper reports the results of an investigation into enhancement of the electrochemical oxidation of p-aminophenol (4-AP) in an aqueous solution with a boron-doped diamond (BDD) electrode, assisted by photocatalysis using a zeolite-supported TiO2 (Z-TiO2) catalyst. The BDD electrode was characterised in 0.1 M Na2SO4-supporting electrolyte and the presence of 4-AP by open-circuit potential behaviour (OCP) and cyclic voltammetry (CV). The electrode behaviour was investigated in the dark and following UV irradiation and in the absence/presence of the Z-TiO2 catalyst. The electro-oxidation process was carried out using chronoamperometry (CA) and multiple-pulsed amperometry (MPA) at the selected potential under potentiostatic conditions. The electrochemical degradation process of 4-AP on the BDD electrode was improved by the application of a pulsed potential, which allowed both in-situ electrochemical cleaning of the electrode and indirect oxidation of 4-AP by oxygen evolution. The application of photocatalysis using Z-TiO2 in the 4-AP electrochemical degradation exhibited an enhanced effect when the anodic potential was set at +1.25 V vs. Ag/AgCl in the water stability region, close to the oxygen evolution potential.

Some mixed ligand complexes containing 2-methylbenzimidazole and thiocyanate ion were synthesized. Free ligands and their metal complexes were characterized using elemental analysis, determination of metal, magnetic susceptibility, molar conductivity, infrared, UV-VIS, and (1H, 13C) NMR spectra, and X-ray structure analysis. The results suggest that the Ag(I) complex has linear geometry, Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have tetrahedral geometry, Pd(II) complex has square planar geometry, VO(IV) square pyramidal geometry, Pb(II) irregular tetrahedral geometry, and that the Cr(III) and Mn(II) complexes have octahedral geometry. The following general formulae were proposed for the prepared complexes: [AgBX], [CrB3X3], (HB)2[MnB2X4] · 2B and [MB2X2], where B = 2-methylbenzimidazole, HB = 2-methylbenzimidazolium, X = thiocyanate ion, and M = VO(IV), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Cd(II), and Pb(II). Molar conductance of a 10−3 M solution in N,N-dimethyl formamide (DMF) indicates that all the complexes are non-electrolytes except the Mn(II) complex which is an electrolyte because the molar conductivity of its solution in DMF is high.

A novel platinum(IV) coordination compound with 6-mercaptopurine (6-Hmp) has been synthesised and characterised by IR and NMR spectroscopy. Spectroscopic parameters indicate the presence of two chelate (S-6, N-7) monodeprotonated ligands and two chloride ions in the coordination sphere of [PtCl2(6-mp)2] · H2O (I). Two Pt(IV) coordination compounds, [PtCl2(6-mp)2] · H2O (I) and [PtCl4(dbtp)2] (II), were used in the in vivo test against B16 mouse melanoma tumours. Cytotoxic activity of compound II against the tumour cells was found to be high (LC10 = 2.6 μM, LC50 = 17.0 μM, LC90 = 58.0 μM) compared to that of cisplatin.

Swelling properties of amphoteric polyacrylamide (AmPAM) dispersions were investigated by measurements of apparent viscosity and particle morphology. AmPAM dispersion was prepared by dispersion polymerization in aqueous solution of ammonium sulphate. Changes of particles during dispersion polymerisation of AmPAM were simulated and compared with anionic and cationic polyacrylamide (APAM and CPAM, respectively). Sample viscosity and particle morphology were obtained using a rotational viscometer and optical microscope. It was found that small molecules or ions enter and swell particles in the AmPAM dispersion when (NH4)2SO4 concentration decreases. Similarly, monomers, including acrylamide, acrylic acid, and methacrylatoethyl trimethyl ammonium chloride, have the same effects on the AmPAM dispersion but the effect degree is different. Swelling properties of the AmPAM dispersion were different from those of the APAM and CPAM dispersions due to their different ionic nature, type of stabiliser, media, etc. Particles in the APAM or CPAM dispersions were swelled less than those in the AmPAM dispersion.

The equilibrium geometries and electronic structures for a series of single-wall carbon nanotubes (SWCNTs) modified with phenylene were studied using the density functional theory (DFT) at the B3LYP/6-31G(d) level. Of the four configurations of the phenylene-modified SWCNTs, the v-configuration in which the bond is perpendicular to the main axis of the SWCNT is the most thermodynamically stable. The increase in radii of the modified SWCNTs generally leads to a decrease in the energy gaps. The first absorptions in the electronic spectra of the modified SWCNTs compared with those in the electronic spectra of pristine SWCNTs are basically red-shifted. The chemical shifts of bridged carbon atoms connected with phenylene in the v-configuration are shifted downfield relative to those of the pristine SWCNTs. The aromaticity of the rings in SWCNTs is improved owing to the addition of phenylene.

A series of nine 5-arylidenerhodanine derivatives was prepared in good yields and purity without the use of a solvent or catalyst under microwave-assisted condensation with some substituted isatins. All 5-arylidenerhodanines were evaluated as possible inhibitors of the CK1α/β, CDK5/p25, and GSK-3α/β kinases. None of them showed substantive inhibitory activity against these kinases when evaluated at the concentration of 10 μM.

The Pd-catalysed conjugate addition of arylboronic acids to α,β-unsaturated cyclic ketones was studied under controlled microwave irradiation conditions. A variety of catalysts, bases and solvents was explored in order to achieve optimum yields in the shortest possible reaction time. Under optimised conditions (Pd(OAc)2/2,2′-bipyridine and KF in a mixture of toluene, water, and acetic acid and 10 min microwave irradiation), a range of arylboronic acids was successfully added to several cyclic enones. With chiral phosphane ligands, a promising enantioselectivity was obtained (85 % ee).

The Mitsunobu reaction is a well-established fundamental reaction and has been widely applied in organic synthesis. In this paper, under Mitsunobu conditions dehydration proceeds between (2-chloroquinolin-3-yl)methanol and nitrogen heterocyclic compounds such as quinazolinone, pyrimidone, 2-oxoquinoline in dry THF in the presence of triethylamine, triphenylphosphane and diethyl azodicarboxylate to give the corresponding products. As part of our recent research, we attempted to couple two N-heterocyclic compounds under Mitsunobu reaction conditions to provide efficient building blocks for natural product synthesis.

A series of forty-five derivatives of 3-phenyl-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones and forty-five derivatives of 3-phenyl-2H-1,3-benzoxazine-2,4(3H)-dithiones was synthesised. The compounds exhibited in-vitro activity against Mycobacterium tuberculosis, M. kansasii (two strains), and M. avium. The most active derivatives were more active than isonicotinhydrazide (INH). The quantitative relationships between the structure and antimycobacterial activity were calculated. The activity against M. tuberculosis increased with the lipophilicity of the substituents.

The present work summarizes results of isolation and identification of polar constituents of the methanolic extract of Ligustrum vulgare L. leaves and of the evaluation of inhibiting activity of selected isolates on rat lung cytosol fraction lipoxygenase. Six different compounds were isolated from the ethylacetate and butanol portions of the methanolic extract (hydroxytyrosol and its glucoside, ligustroflavon, oleuropein, acteoside, echinacoside). The inhibitory activity of oleuropein, echinacoside and the water infusion of Ligustrum vulgare leaves tested on LOX was expressed as IC50. Kinetic parameters (K M, V max) and type of inhibition were determined. As the most effective in competitive inhibition of LOX, oleuropein was proved.

The emissions of methane (CH4), a powerful greenhouse gas (GES), contribute to the increase in GES concentration level in the atmosphere. For this reason, the importance of controlling CH4 emissions of anthropogenic origin has increased over the last decades. Physicochemical and biological processes are available for treating CH4. For this reason, such properties as the solubility of CH4 in aqueous solutions and organic solvents are of great relevance in different applications in environmental engineering and biotechnology. In this study, the solubility of CH4 was determined at 298 K and 101.3 kPa in organic solvents, such as polyoxyethylenesorbates (Tween 20, Tween 40, and Tween 60), and linear alcohols (methanol, ethanol, and butan-1-ol) alone and in their admixtures. Admixtures of methanol with butan-1-ol exhibited the highest solubility of CH4, of around 0.49 g m−3 of solvent, whereas the solubility of CH4 in linear alcohols varied from 0.167 g m−3 to 0.41 g m−3 of solvent. In the case of Tweens, CH4 solubility decreased with the hydrophilic-lipophilic balance (HLB) number.

Bicyclo[1.1.1]pentane is a highly strained hydrocarbon system due to close proximity of nonbonded bridge head carbons. Based on fully optimized molecular geometries at the density functional theory using the B3LYP/6-31G* level, densities, detonation velocities, and pressures for a series of polynitrobicyclo[1.1.1]pentanes, as well as their thermal stabilities were investigated in search for high energy density materials (HEDMs). The designed compounds with more than two nitro groups are characterized by high heat of formation and magnitude correlative with the number and space distance of nitro groups. Density was calculated using the crystal packing calculations and an increase in the number of nitro groups increases the density. The increase in density shows a linear increase in the detonation characteristics. Bond dissociation energy was analyzed to determine thermal stability. Calculations of the bond length and bond dissociation energies of the C-NO2 bond indicate that this may be the possible trigger bond in the pyrolysis mechanism. 1,2,3-Trinitrobicyclo[1.1.1]pentane (S3), 1,2,3,4-tetranitrobicyclo[1.1.1]pentane (S4), and 1,2,3,4,5-pentanitrobicyclo[1.1.1]pentane (S5) have better energetic characteristics with better stability and insensitivity, and as such may be explored in defense applications as promising candidates of the HEDMs series.

Kinetics of the electron transfer process between citrates and manganese(III) ions has been studied in acidic aqueous solutions. Acidification of the reaction mixture increased the reaction rate. The reaction is dependent on pH because there are two main protolytic forms of the Mn(III)-citrate complex in the studied pH range (4.5–6.5). Reduction potentials of Mn(III)/Mn(II) system in acidic and basic solutions as well as protolytic equilibria play a crucial role in understanding the pH profile of the studied system. The rate constants for Mn(III)citH and Mn(III)citH2+ species degradation processes are presented (citH3− and citH22− are trivalent and divalent anions of citric acid, citH4, respectively). Protolytic constant (expressed as pK′a) for Mn(III)citH protonation is estimated and discussed.