Effect of the Preparation Methodof Al–Mg–O Catalysts on the Selective Decomposition of Ethanol

Summary.  Selective decomposition of ethanol was used as a test reaction at 350°C to evaluate the catalytic activity of two Al–Mg–O mixed oxides prepared by two different methods (wet impregnation and coprecipitation). The catalyst precursors were examined by TG and DTA and were calcined between 500–900°C for 5 h in air. The surface area of all catalysts was measured by N₂ sorption using the BET method. The total acidity and basicity were determined by TPD using pyridine and formic acid. The catalysts were characterized by XRD analysis. It was found that the preparation method of Al–Mg–O catalyst has a great effect on the selective decomposition of ethanol. Al–Mg–O (I) catalysts, prepared by wet impregnation, were more selective towards ethene formation during dehydration of ethanol. This is ascribed to their high total surface acidity. On the other hand, Al–Mg–O (II) catalysts, prepared by coprecipitation, were highly selective in the oxidative dehydrogenation of ethanol to yield acetaldehyde. This could be attributed to their high concentration of basic sites. In addition, the production of traces of diethyl ether was also observed (three times more for Al–Mg–O (II) than for Al–Mg–O (I)). Corresponding author. E-mail: shalawy99@yahoo.com Received October 12, 2001. Accepted (revised) January 7, 2002     

An effective high-speed countercurrent chromatographic method for preparative isolation and purification of mollugin directly from the ethanol extract of the Chinese medicinal plant Rubia cordifolia

The medicinal plant Rubia cordifolia has been used widely in traditional Chinese medicine (TCM) for its antibacterial, antioxidant and anti-inflammatory activities. In this study, a preparative high-speed countercurrent chromatography (HSCCC) method for isolation and purification of the bioactive component mollugin directly from the ethanol extract of R. cordifolia was successfully established by using light petroleum (bp 60-90 degrees C)/ethanol/diethyl ether/water as the two-phase solvent system. The upper phase of light petroleum/ethanol/diethyl ether/water (5:4:3:1 v/v) was used as the stationary phase of HSCCC. Under the optimum conditions, 46 mg of mollugin at 98.5% purity, as determined by HPLC, could be yielded from 500 mg of the crude extract in a single HSCCC separation. The peak fraction of HSCCC was identified by 1H NMR and 13C NMR.     

Diphasic dialysis extraction technique for clenbuterol determination in bovine retina by gas chromatography-mass spectrometry

Summary A method is described for the extraction of clebuterol from bovine retina samples by diphasic dialysis using gas chromatography—mass spectrometry (GC-MS) as the procedure of determination. Following chemical digestion of retinal tissue in alkaline medium at 80°C, clenbuterol is extracted by diphasic dialysis using diethyl ether as solvent at 37°C, for 4 h at 150 rpm. Diethyl ether is evaporated to dryness and clenbuterol determined by GC-MS after butylboronic acid (BBA) derivatization. A detection limit of 2.5 ng g⁻¹, repeatability of 9.0% and reproducibility of 22.9%, with recoveries always >86% (n=5), are achieved as validation criteria.     

On the nature of decrease in the particles size of nanostructured nickel oxide obtained by the sol-gel method in the presence of surfactants

A processes of formation of nanostructured powders of nickel oxide by annealing in the temperature range of 200–700°C of the nickel hydroxide obtained by the sol-gel method at 80°C from solutions of nickel nitrate by precipitation with alkali in the presence of surfactant AF-12 (polyethylene oxide alkylphenyl ether) was investigated. The formation of nanostructured powders of nickel oxide in the presence of a surfactant reduces the size of nanoparticles to 20–25 nm, which is 1.5 times smaller than the particles obtained without a surfactant. The effective influence of surfactant on the particle size begins in the temperature range of its decomposition and evaporation equal 350–400°C.     

Conversion of lignocellulosics pretreated with liquid hot water to ethanol

Lignocellulosic materials pretreated using liquid hot water (LHW) (220°C, 5 MPa, 120 s) were fermented to ethanol by batch simultaneous saccharification and fermentation (SSF) usingSaccharomyces cerevisiae in the presence ofTrichoderma reesei cellulase. SSF of sugarcane bagasse (as received), aspen chips (smallest dimension 3 mm), and mixed hardwood flour (−60 +70 mesh) resulted in 90% conversion to ethanol in 2–5 d at enzyme loadings of 15–30 FPU/g. In most cases, 90% of the final conversion was achieved within 75 h of inoculation. Comminution of the pretreated substrates did not affect the conversion to ethanol. The hydrolysate produced from the LHW pretreatment showed slight inhibition of batch growth ofS. cerevisiae. Solids pretreated at a concentration of 100 g/L were as reactive as those pretreated at a lower concentration, provided that the temperature was maintained at 220°C.     

Monolayers of hydrogen-bonded polymer blends at the air–water interface: poly(vinylacetate)+poly (4-hydroxystyrene)

 The surface pressure (Π) vs surface concentration (Γ_s) curves of the hydrogen-bonded polymer blend poly(vinylacetate)+ poly(4-hydro-xystyrene) (PVAc+P4HS) have been measured at 25 °C onto a water subphase at pH=2.0. While PVAc forms extended monolayers, and the free surface of water is found to be a good solvent for it, P4HS forms compressed monolayers, and the surface is a near Θ-type solvent for it. PVAc and P4HS form miscible non-ideal monolayers until near the collapse pressure through the whole concentration range. The composition dependence of the Π–Γ_s curves is rather complex. Contrary to what might be expected, the addition of PVAc to the blend does not reduce the rigidity of the monolayer until its weight fraction is larger than 0.5. The compressibility data of the P4HS-rich monolayers suggest the existence of a second maximum at high surface coverages, a result already observed in some polysiloxanes. Received: 11 March 1998 Accepted: 7 May 1998     

Complex formation between chlorine dioxide and 2,2,6,6-tetramethylpiperidin-1-oxyl

The complex formation of ClO₂ with 2,2,6,6-tetramethylpiperidin-1-oxyl (TMPO) in acetone, acetonitrile,n-heptane, diethyl ether, carbon tetrachloride, and toluene was studied spectrophotometrically at −20 to +20 °C. The thermodynamic parameters of complex formation were determined at 20 °C. The transformation of the complex into the oxoammonium salt TMPO⁺ClO ₂ ⁻ was found. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1703–1706, October, 2000.     

Thermoanalytical studies of titanium(IV) acetylacetonate xerogels with emphasis on evolved gas analysis

Thermal decomposition of precursor xerogels for TiO₂, obtained by gelling of acetylacetonate-modified titanium(IV) tetraisopropoxide (prepared at Ti-alkoxide:acetylacetone molar ratios of 1:1 (Ti-1) and 1:2 (Ti-2)) in boiling 2-methoxyethanol, was monitored by simultaneous TG/DTA/EGA-MS and EGA-FTIR measurements. Thermal degradation processes of Ti-1 and Ti-2 in the temperature range of 30–700°C consist of six mass loss steps, the total mass loss being 46.3% and 54.4%, respectively. EGA by FTIR and MS revealed release of H₂O below 120°C; followed by evolution of acetone and acetic acid between approximately 100 and 320°C, and that of CO₂ up to 560°C. Acetylacetone is evolved to a significant extent from sample Ti-2 at 120–200°C.     

Fast dynamic wetting of polymer surfaces by miscible and immiscible liquids

The initial stages of spontaneous spreading of a solvent drop (toluene) on the surface of a soluble polymer (polystyrene) have been studied with a high-speed camera. For drops of 1–4 μL volume, the increase in contact radius r can be described by a power law r μ t^a r \propto {t^{\alpha }} , with the spreading exponent α = 0.50 and for the first ≈8 ms. Thereafter, the three-phase contact line was pinned leading to a macroscopic static contact angle of Θ₀ = 12–15°. The insoluble liquids ethanol (α = 0.47, Θ₀ = 0) and water (α = 0.35, Θ₀ = 90°) showed a slower spreading. We attribute the fast spreading of toluene to the strong interaction with the polymer, like in reactive wetting. The finite macroscopic contact angle indicates the formation of a ridge by softening of polystyrene due to permeated toluene and the subsequent plastic deformation by the surface tension of the liquid. This interpretation is supported by experiments on polymers grafted from a silicon wafer. Toluene completely wets polymer brush surfaces. Transport of toluene through the vapor phase plays a significant role.     

Thermal analysis of polyesters containing oxirane groups

The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic anhydride and ethylene glycol and its new epoxidized form have been performed. The thermal characterization of initial polyester and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program. The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking of epoxidized polyester (322.8–336.4°C) and the endothermic decomposition peak of the cured material (363.8–388.9°C) were observed. The peak maximum temperatures (Tmax) and the heat of cross-linking reaction (ΔH_c) for epoxypolyester prepared at 20–60°C under 1–4 h were evaluated. The Tmax1 were almost independent from epoxidation conditions, while, the values of ΔH_c were dependent from conditions of synthesis. The ΔH_c values of this process decreased when time of oxidation increased. The highest values of ΔH_c at 40°C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester indicating the ester (370–380°C) and ether (450–460°C) bond breakdown.     

Thin-layer chromatography of chlorinated anisoles and veratroles

Summary The thin-layer chromatography of chlorinated anisoles (methoxybenzenes) and veratroles (1,2-dimethoxybenzenes) has been examined on silica gel G60 and RP-18 thin-layer plates. More than fifty solvent systems were screened and some of them recommended for particular separations. Acetone was shown to be suitable for group separation of both chlorinated anisoles and veratroles on a silica gel G60 stationary phase having a very narrow range of R_F values. On the other hand, benzene, dichloromethane and the various mixtures of light petroleum (b.p. 40–60°C) and a more polar eluent (such as diethyl ether, acetone or ethyl acetate) were recommended for separation of certain individual isomers. The best separation of chloroanisoles was achieved using RP-18 plates and methanol-water (9010) as the solvent system.     

Extractability of radiocesium from processed green tea leaves with hot water: the first emergent tea leaves harvested after the TEPCO’s Fukushima Daiichi Nuclear Power Plant accident

In some tea tree planting areas within 300 km from the TEPCO’s Fukushima Daiichi Nuclear Power Plant (FNPP), it was found that newly emerged tea plant leaves for green tea contained two radiocesium species (cesium-134 and cesium-137). In this study, using processed green tea leaves for drinking, extraction ratios of radiocesium under several brew conditions were observed. When 90 °C water was used, 50–70% of radiocesium was extracted into the water, while 54–60% of radiocesium was extracted with 60 °C water. A part of radiocesium would be removed from leaves if the leaves were washed with 20 and 60 °C water before brewing, and the efficiencies were 11 and 32%, respectively. Newly emerged camellia leaves were used to simulate the radiocesium removal ratio from raw tea leaves by washing and boiling; radioactivity concentration was decreased to 60% of the original concentration with washing and 10 min boiling. From these results, it was found that almost half of the radiocesium would not be removed from raw or processed tea leaves. The values obtained in the present study could be used for internal radiation dose estimation from tea leaves.     

Radiation-Induced Degradation of a Series of Poly(vinyl Ethers)

The degradative effects of γ-radiation on diethyl ether solutions of poly(alkyl vinyl ethers) under a variety of conditions were studied by polymer molecular weight measurements. Poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(isopropyl vinyl ether) (PIPVE), and poly(isobutyl vinyl ether) (PIBVE) exhibited similar degradative behavior, with G_(SC) values between 0.3 and 0.9 scissions/100 eV at 0°C. Chemically polymerized and radiation-polymerized PEVE samples gave comparable results. Chain degradation was much more pronounced for samples of poly(tert-butyl vinyl ether) (PTBVE) which yielded a G_(SC) value of 3.6 at 0°C. Degradation experiments conducted on PEVE in air resulted in significantly higher rates of scission: G_(SC) = 5.6 scissions/100 eV at 0°C. Chain scission was not measurably influenced by changing the solvent from diethyl ether to di-isopropyl ether. Increased polymer concentration was found to reduce the rate of polymer degradation.     

Microwave‐assisted alkylation of diethyl ethoxycarbonylmethylphosphonate under solventless conditions

The reaction of diethyl ethoxycarbonylmethylphosphonate with a series of alkyl halides, under microwave (MW) and solventless conditions at 120°C, in the presence of Cs₂CO₃ and in the absence of a phase transfer catalyst afforded the corresponding monoalkylated products in yields of >70%. The thermal variant carried out in boiling acetonitrile was slow and led to incomplete conversions. In the MW method, the phase transfer catalyst is substituted by MW irradiation and there is no need for a solvent. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:241–246, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21009     

Thermoluminescence of photoirradiated petroleum luminophores of pyrolytic origin

Photothermoluminescence (PTL) of petroleum luminophores of pyrolytic origin was studied over a wide temperature range (−196 to 250°C). Problems related to the mechanism and stages of photochemical processes in petroleum luminophores are discussed. It was revealed that low-temperature PTL maximums at −165, −108, and −75°C are due to recombination of trapped electrons with radical cations of polycyclic aromatic hydrocarbons (PAHs) during the freezing out of the motions of H, O₂, and R^·. High-temperature (relative to the luminophore freezing points) PTL maximums at 52, 105–120, and 130–140°C are due to processes associated with the oxidation of R^·, PAHs, and olefins by ³O₂ and ¹O₂.     

The solvent extraction of flurazepam and its major metaboutes and their determination by polarography

The solvent extraction of flurazepam and its major metabolites from aqueous solutions of varying pH has been studied at concentrations encountered in body fluids following therapeutic dosage. Distribution ratios have been calculated over the pH range 0–14 and for the solvents, ethyl acetate, diethyl ether, cyclohexane and petroleum ether (40–60°C). Based on this study, a solvent extraction scheme is evaluated for the recovery of such concentrations of these compounds in mixtures, with final polarographic determinations. Recoveries exceeding 95% were found; the method is specific for the determination of flurazepam and its acetic acid metabolite in mixtures. The total concentration of the remaining metabolites, i.e. the hydroxyethyl-, N-1-desalkyl-, and N-1-desalkyl-3-hydroxy metabolites can be estimated after solvent extraction and differential pulse polarography in alkaline solutions.     

Catalytic carbonylation for the synthesis of chemical intermediates

Chemistry related to three catalytic carbonylation reactions is discussed. Synthesis of diphenylurea from nitrobenzene, aniline, and CO gives isolated yields above 98% at 100–120 °C and 15–60 bar of CO in the presence of a palladium (II) complex, PPh₃ and NEt₄Cl. Experimental evidence was provided to prove a new reaction stoichiometry and involvement of a carbamoyl intermediate. In carbonylation of HCHO over ion exchange resin catalysts, reaction temperature, time, pressure, and solvent were important variables to obtain high yields of methyl glycolate. Carbonylation of isobutylphenylethanol at 120°C and 40 bar of CO in the presence of PdCl₂−PPh₃−HCl gives 98% yield of α-(4-isobutylphenyl) propionic acid (ibuprofen). Each catalyst component had a definite role that is indispensable for an efficient overall reaction.     

Use of pH-Zone Refining Countercurrent Chromatography for Preparative Separation of Fangchinoline and Tetrandrine from Stephania tetrandra

pH-Zone-refining countercurrent chromatography with a multilayer coil planet centrifuge has been successfully used for separation of fangchinoline and tetrandrine from crude extracts of Stephania tetrandra. The two target compounds were completely resolved by use of the two-phase solvent system petroleum ether (60–90 °C)–ethyl acetate–methanol–water 5:5:1:9 (v/v), with 10 mm triethylamine in the organic stationary phase and 5 mm hydrochloric acid in the aqueous mobile phase. Separation of 3.5 g sample yielded 126 mg fangchinoline (LC purity >93%) and 249 mg tetrandrine (LC purity >95%). The structures of the compounds were confirmed by use of electrospray ionization mass spectrometry and ¹H NMR.     

Synthesis of phosphate‐pendant polymers and their application to thermally latent polymeric initiators

A novel phosphate monomer, O‐p‐(methacryloyloxymethyl)benzyl O,O‐diethyl phosphate (MDP) was synthesized by the reaction of diethyl phosphorochloridate with 1,4‐benzenedimethanol, followed by the reaction with methacryloyl chloride in the presence of triethylamine. The radical polymerization of MDP and copolymerization with methyl methacrylate were carried out in the presence of 2,2′‐azobisisobutyronitrile (3 mol %) in dimethylacetamide at 60 °C for 20 h to afford phosphate‐pendant polymers. The polymerization of glycidyl phenyl ether (GPE) was carried out with the phosphate‐pendant polymer as an initiator in the presence of ZnCl₂. The polymerization did not proceed below 90 °C but rapidly proceeded above 90 °C to afford polyGPE. The phosphate‐pendant polymer served as a good thermally latent polymeric initiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3365–3370, 2001     

Experimental designs dedicated to the evaluation of a membrane extraction method: membrane-assisted solvent extraction for compounds having different polarities by means of gas chromatography–mass detection

Membrane-assisted solvent extraction was applied for the determination of different classes of compounds in water, having K _o/w (octanol–water partition coefficient) values between 10¹ (aniline) and 10⁸ (methyl stearate), by means of experimental designs. Four solvents were investigated—propan-2-ol, ethyl acetate, diisopropyl ether and cyclohexane—as well as extraction time, temperature, salt impact, pH and methanol addition. The best choice was diisopropyl ether, 50 °C, 30 min and an addition of 3 g of sodium chloride at pH 2 for polar compounds. The relative standard deviation (n = 3) was found in the range from 5 to 17%. Recoveries ranged between 34 and 100%. Membrane-assisted solvent extraction was successfully applied to a fast screening method dedicated to an unknown wastewater sample.